NO20150745A1

NO20150745A1 - Process for treatment of crude oil, sludges and emulsions

Info

Publication number: NO20150745A1
Application number: NO20150745A
Authority: NO
Inventors: Jyoti Dhruva Dasgupta
Original assignee: Nagaarjuna Shubho Green Technologies Private Ltd
Priority date: 2012-12-13
Filing date: 2015-06-08
Publication date: 2015-06-08
Also published as: CN104903244A; EA201591066A1; BR112015013732A2; GB201511405D0; WO2014091498A4; AU2013358575A1; MX2015007576A; WO2014091498A3; US20150322348A1; GB2523517A; CA2894026A1; CN104903244B; WO2014091498A2

Description

Field of the Invention:

The present invention relates to processes for treatment of petroleum/crude sludge, emulsions and slop oil. More particularly, the present invention relates to a process of removal of bound and unbound water from petroleum/crude sludge, emulsions and slop oil comprising of hydrocarbons, bound water, unbound water, dissolved and un-dissolved solids, into different pure salable streams, particularly but not restricted to petroleum industry.

Background of the Invention:

Petroleum crude comes out of oil wells invariably with water, dissolved and un-dissolved solids and sulfur bearing compounds containing partly both bound water and unbound water. This petroleum crude is thereafter treated at group collection centers (GCCs, hereinafter) of oil companies wherein firstly the petroleum crude is de-sulfurized and then unbound water are removed along with un-dissolved solids. However, GCCs do not remove bound water and dissolved solids except in cases where de-emulsifiers are used. Presumably, because desalting of crude leads to additional formation of emulsion with bound water, crude with bound water is sent to oil wells.

GCC is specifically required to remove sulfur with most of the un-dissolved solids from the crude and remove entire water to bring down the crude water content below 5000 ppm before sending it to refineries. The process of removal of water mainly involves allowing the crude to settle in a settling tank wherein the top layer, middle layer and bottom layer are formed. The top layer contains pure crude that is sent to refineries for further treatment. The middle layer contains water bearing emulsion that is sent to tank where it is heated subjected to high voltage oscillating electric field and optionally with use of de-emulsifiers where the purpose is to remove maximum water in least time. The bottom layer normally contains oily water with un-dissolved solids which is known as slop oil. Being a pollutant, often the slop oil is sent to abandoned oil wells for storage through pipe lines.

In refineries, production, transportation, storage and refining of the crude oil mostly create sludge. Sludge is generally a tightly held viscous emulsion of oil, water and solids wherein the solid content could vary widely. Whenever oil and water is mixed and agitated, sludge gets formed. In refineries, sludge is also formed in the desalting unit where crude is washed with fresh water to remove Alkalis that had ingressed with seawater. Also, sludge gets produced in hydro-crackers, crude storage tanks, slop oil, API separators and the like. Normally 1.6 kgs. of sludge is produced per tonne of crude. As per a 1992 US-EPA report, by and large petroleum refineries unavoidably generate about 30,000 tons of oil sludge waste streams per year per refinery. More than 80% of this sludge comes under the EPA hazardous waste nos. F037 and F038. In India, more than 2.62 lac tonnes of sludge is produced in a year.

Sludge also gets formed, when water in crude is vigorously agitated/ sheared by transfer pumps. Being heavier than light oils, it tends to settle at the bottom of ship load, but gets removed from ship, when crude is pumped out at the refinery. Apart from that, we have tank sludge, which is a solid layer that accumulates with time at ship bottom, and is removed once in 5 years or so. Typically a 60-M tank disgorges 1,000 MT of material. About 85 to 90% of it constitutes heavy hydrocarbons like paraffin, asphalt, micro-crystalline wax, etc. Often this material is removed using high pressure water jets. Sludge also gets generated in post refinery operations. When heavy liquid fuels like LSHS or furnace oil are used for power generation through low speed DG sets 0.5 wt % to 1 wt % sludge gets formed. These DG sets could either be land based or marine. Sludge also gets produced in waste-oil reconditioning plants. Formation of sludge is a great problem in overall world.

For example, Texaco, (acquired by Chevron in 2001) after oil drilling operations from 1964 to 1990, seventy billion litres of toxic petroleum sludge pools were abandoned in Ecuadorean Amazon rainforest without any remedy. This sludge came from drilling operations per se and not from production. Chevron has a patented technology for treatment of sludge as disclosed in US Pat. No.4,689,155. However, still the sludge was dumped into streams and rivers that local people depended for drinking, bathing and fishing. It dug over 900 open Air, unlined waste pits that still seep toxins into the ground. This sludge contained chemicals like benzene & polycyclic aromatic hydrocarbons. What's worse is this dumping was done intentionally to cut corners and save an estimated US $3 per barrel. The company saved US $1.32 billion, but it led to 30,000 Ecuadoreans suffering, with 1,400 of them dying. This could lead to 10,000 more deaths by 2080.

In case of orient region of Ecuadorean rainforest, which once supported 30,000 people, the land itself has become toxic and water system contaminated. Almost any kind of food from this region, whether it's farmed, domesticated, caught in the wild or in water is unsafe to eat. Local economies and communities have collapsed. Eighteen years ago locals filed a class-action law-suit. Damages had been assessed at US $27.3 billion. Locals own their case and Chevron was asked to pay US $18 billion. Rather than take responsibility and pay up for this environmental disaster, Chevron refused to pay and is wagjng unprecedented public relations and lobbying campaigns to avoid håving to clean up the mess.

In case of PdVSA, the Public Sector Oil Company in Venezuela. In August 1999, it was slapped with US $1.5 billion in environmental liabilities. Amongst other things, it was asked to clean up 15,000 oil pits containing contaminated sludge from oil wells. This al one cost the Company US $1 billion. Under pressure from courts, this Company which had traditionally ignored the environment has now started cleaning-up operations & pledges to rank environmental protection as one of its top most goals.

In case of Russia, it generates more than 3 million tonnes of Petroleum Sludge per year, more than 33% of that coming from oil wells alone. Russian oil & gas industry is the 3rd largest contributor to accumulation of industrial wastes in that country. Russia has 7,000 abandoned oil wells. It has 416,000 km of oil pipelines that often get damaged due to corrosion. Every year it faces 50,000 to 60,000 pipeline related accidents, leading to a leak of 15 million tonnes of oil before automatic flow blocking mechanisms get activated. About 30% of this ends up in rivers and lakes, i.e. 4 to 5 million tonnes a year. In 1994, at Komi alone 0.1 million tonnes of oil got spilled from a single pipeline related accident. In 1993 at Tyagan, in Tyumen region, a single pipeline related incident led to a spillage of 0.42 million tonnes of oil. Russia has lagoons holding millions of tonnes of sludge. Western Siberia has more than 3 million tonnes of slop. Tatarstan has over 2.5 million tonnes. Bashkortostan has 700 lagoons with 2 million tonnes of sludge. Land being cheap, storage of sludge in lagoons cost US $20 to $40 per tonne depending on location. They burn away most off their sludge causing extensive air pollution. Russia has 27 refineries with total capacity of 300 million tonnes. At its Saratov Refinery, lagoons cover more than 150 ha. The content of oil in its ground water is 7.2 grams per litre. US companies alone are currently providing sludge disposal service in Russia worth more than US $90 million per annum. Russia pays between US $28 to $360 to dispose off a tonne of sludge, depending on how far the area is from city & also on the kind of technology and equipment used.

The cost of a Russian custom-made sludge processing system built with foreign components start from US $5 million onwards. These are mostly de-emulsifying units based on settling tanks, centrifuges & decanters. Oil skimmed from therein gets used in barges & pumps. They also use bio-remediation & incinerators. For de-emulsification combined with bio-remediation they pay between US $ 160 to 200 per tonne. For innovative technologies like ultra-sound treatment they pay US $300 per tonne.

Since sludge is difficult to dispose off, till recently refineries were dumping it in tanks, ponds & lagoons. Most refineries in developing and under-developed countries continue to that even till the present date. Typically, such lagoons are 4 ha. in size & contain about 1.2 to 1.6 lakh tonnes of sludge. Several of them contain sludge since 1896. Sludges in such old lagoons are known as "weathered sludge" With age, they tend to get homogenized.

In developed countries like the US, fresh storage of sludge in ponds or lagoons is prohibited, unless they are lined with non-permeable materials. Even that is strongly discouraged. Thafs because surrounding soil & groundwater get adversely impacted. Evaporation of volatiles too causes strong odour & air pollution.

In 1980, US Congress enacted the Comprehensive Environmental Response, Compensation & Liability Act. This created a tax on chemical & petroleum businesses and the money thus collected went into a large trust known as Superfund. That money paid for the cleaning up of all hazardous waste disposal and spill sites, like the petroleum sludge lagoons. In 1995 the tax on industries expired. But the Superfund Programme continued. Today money is appropriated from the general tax revenue, to fund it. US-EPA administers this fund in co-operation with individual states.

Recently, cleaning-up of sludge ponds & lagoons has emerged as a lucrative commercial business. Refineries are keen to recover oil from sludge. When thafs not possible, they are keen to extract its energy. When even thafs not possible, they try to convert it into innocuous substances, at the least cost. There are various efforts seen in the art for cleaning-up of sludge using various techniques.

Use of de-emulsifiers/ chemicals is seen in the art for breaking of the sludge. For example, Chinese patent document CN101786776 to Norman Kevin, Elk Point discloses deep treatment process wherein the oil-containing sludge is introduced into a regulation pool followed by adding of hot water and subsequent stirring thereof such that the fluidity of oil-containing sludge is improved. The sludge is furfner treated in cyclone desalter and sent into a modulation tank where a predefined quantity of demulsifier is added followed by de-emulsification at an appropriate temperature. Also, Czechoslovakian patent document CS8702260-A to Baxa J entitled "Oil dehydration and desalting- by adding distillation slops and de-emulsifying vacuum distillation" discloses use of de-emulsifiers.

M/s. Smith & Loveless Inc. treats refinery sludge with chemicals and aeration. M/s. Lenntech Petrochemical Company from Netherlands uses chemicals, solvent extraction, membranes, filtration, floatation, flocculation, reverse osmosis, etc. to recover oil. M/s. Reverse Oil, a Ukrainian-American Joint Venture is desludging "Ukrtatnafta" sludge ponds since 1996, with a plethora of chemicals, merely to minimize its adverse environmental impact. However, sludge breaking with chemicals/ de-emulsifiers doesn't always affect 100% separation. Also, the use of de-emulsifiers is unfit for further use within refineries unless the recovered oil is predominantly free from water.

Alternatively, a technique of heating the sludge with solvent, preferably with Azeotropic solvent mixtures, is also seen in the art. For example, German patent document DE 19936474 to Bereznikov Anatoli provides separation of oil-containing sludges by heating with a solvent and recyeling the solvent is effected using a solvent (e.g. toluene) forming a heterogeneous azeotropic mixture with the aqueous component. The mixture is steadily mixed to give slurry which is then heated to its boiling point. The saturated vapour is condensed and the aqueous component and the solid residue removed, this being continued to complete water separation by controlling the temperature increase. Also, Spanish patent document ES2047129T3 to Richter Gedeon Vegyeszet discloses dehydration process employing Azeotropic distillation and more particularly it relates to a process for the vigorous dehydration of substances or mixtures, primarily condensation reaction mixtures, (e.g. direct esterification, direct acetal formation, direct ketal formation) using continuous Azeotropic distillation. Further, US Patent document US 3669847A to Dynamit Nobel Ag discloses process for separating steam-volatile organic solvents from industrial process waste waters wherein Steam-volatile organic solvents are removed from process waste waters by intimately mixing the process waste waters with steam to form an azeotropic steam mixture, withdrawing the Azeotropic steam mixture from the resultant mixture of steam and water, and condensing said Azeotropic steam mixture.

Companies like M/s. CEVA International Inc. & M/s. E & I Technologies, Inc. recover oil by centrifugjng sludge. In collaboration with M/s. Petro-Waste Services, Inc. (PWS), CEVA offers equipment in 2 sizes. One processes 200 tonnes of sludge/day, while the other handles 475 tonnes of sludge a day. Some of these are mobile units. Often when sludge resolution is not possible, refineries incinerate them. Due to high water content, here burning is often supported with supplementary liquid fuels. M/s. W. N. Best makes incineration systems for processing 0.38 to 26.5 tonnes of petroleum sludge/hour. Many modern refineries dump their sludge in Coker Plants, where fuel is partially recovered. Hence they don't generate sludge. Pollution prevention through non-generation is considered to be most profitable. They create whafs known as Pet Coke. However, the coke oven plants produce high sulfur contents.

Bioremediation is however emergjng as major trend. Here sludge is uniformly mixed with soil, such that its total hydrocarbon content is limited to~3 wt. %. Naturally existing bacteria in soil then degrades hydrocarbons into C02 & H20 over a period of few years. To accelerate this, one increases the supply of air, moisture & nutrients into the soil. To increase nutrients, one supplies nitrogen & phosphorus based fertilizers. A certain density & variety of bacteria also helps. With all these, one tries to achieve a significant reduction of hydrocarbons in soil within about a year. This process is also known as "land farming", since one works sludge into land with a view to achieve its final disposal through the slow process of bacterial action.

Biopiling is a further improvement in this field where homogenous sludge and soil mix are placed over an impermeable base of natural clay, along with wood chips to improve permeability. Perforated pipes are connected to a blower or vacuum pumps to aerate the soil pile. Leachate collection system is also incorporated for uniform addition of water and nutrient.

Globally M/s. Biogenie, M/s. Envirosoil Services Ltd. and M/s. Willacy Oil Services Ltd. are active in this field. The LTTD process of Envirosoil treats soil with sludge in a plant and once hydrocarbon content in soil is reduced below the acceptable level of 15 ppm, it is transferred to land. Willacy is very active in Middle East and Turkey.

In India, M/s. Tata Energy Research Institute (TERT) took 7 years to develop "Oilzapper". Thafs an efficient bacterial consortium, developed from 5 bacterial isolates, immobilized over powdered corncob. It efficiently degrades oil based hydrocarbons within about a year. This technology know-how has been transferred to M/s. Shriram Biotech Ltd., Hyderabad & M/s. Bharat Petroleum Corporation Ltd., Mumbai. Oilzapper has successfully degraded more than 10,000 tonnes of petroleum sludge in India over the last 2 years. Globally, bioremediation costs between $ 73 to $ 641 per tonne of sludge.

However, even bioremediation technique has certain limitations. Firstly, the bioremediation process leads to entire loss of valuable hydrocarbon which is highly undesired. Secondly, the bioremediation process is highly expense and consumes a lot of time in waste disposal process. Also, the product obtained after remediation fails to convert waste into wealth as the product obtained after bioremediation treatment is of no use.

Another deadliest pollutant is the slop oil which is normally an oily water containing solids and salts. This water is treated at Group Collection Centres (GCCs) prior sending it to refineries. Slop oil also gets generated in refineries where the crude is added with fresh water for desaltation and removed using same equipments as that of GCC thereby adding unnecessary cost. Also, lot of hydrocarbon is lost in such process in addition to generation of polluting slop oil.

This water being a pollutant is normally sent back for storage wherein the stored corrosive water may leak out in addition to adding cost of transport for discharging the corrosive water in sea water through pipelines. Slop oil also has large implications on environment where it contaminates sea water thereby effecting marine life. Further, slop oil is a major source which has always been neglected although being a valuable source of oil and water both.

For instance, Russia has more than 4,16,000 km pipeline that often gets damaged due to corrosion causing 50-60,000 pipeline related accidents thereby leading to leak of millions of tons of oil before automatic flow blocking mechanisms get activated. About 30% oils ends in rivers and lakes thereby generating slop oil. In 1993, Tyagan in Tyumen region a single pipeline related incident lead to spillage of 0.42 million of oil. In 1994 at Komi alone, 0.1 million tons of oil got spilt from a single pipeline leakage.

Slop oil even comes from cleaning of oil contaminated equipments including cleaning of oil carrying ships. Even in industries apart from oil industries, the industries where oil is used as coolant or for lubrication slop oil gets generated.

Conventionally centrifuge technique is used for treatment of slop oil. For example, German patent document DE4205885 to Meiken, Bernard entitled "Recovery of water, gasoline, heavy oils, and solids from slop oils or oil emulsions" discloses use of two-phase decanter for centrifugjng of slop oil/ emulsions wherein Slop oil is heated to 105-135 °C in a heating circuit formed by a heater, column, and pump. The gases and steam are then drawn from the top of the column, and, from the bottom of the column, heated oil slops are tåken, cooled, and, in a two-phase decanter separated into a centrifuged clean oil-phase and a solid phase. Also, Russian patent document RU2217476 teaches processes of the oil-bearing slimes refining and extraction hydrocarbons from them for refining of the liquid and pasty oily slimes, in particular of the bottom sediments, resistant oil-water emulsions, intermediate layers containing a fair quantity of mechanical impurities. The method provides for dilution of the oily slimes with petroleum, its heating and separation in the three-phase decanter centrifuge for petroleum, water and a concentrate of mechanical impurities. Residual water is separated from petroleum with the light oil fractions in the distillation column. Further, Chinese patent document CN100582031 to China Nat Petroleum Corp discloses a process for processing and utilizing for oil field oil-containing sewage sludge. The invention relates to the process and utilization method of the oily sludge wherein the horizontal centrifuge via a secondary lift pump is used for dehydration. The dehydrated water enters the coming liquid pipeline of the sewage disposal system after centrifuge operation.

However, centrifuge technique is not without limitations. There are generally two types of centrifuges that are used in tandem, namely a decanter and dise stack centrifuge. The dise stack centrifuge has advantages of higher G but it is inefficient when slop oil contains more amount of solids. The decanters enhance density difference but they fail in case of handling of heavy crude/ extra heavy crude contaminated water that has oil density equal to water density. Centrifuge enhances buoyancy but reduces residence time due to which it is effective only when the particle size is more and drag is less. Moreover, surface charge of the oil particles tends to prevent oil particles to coalesce and come together. Further, the centrifuge can handle ultrafine particles only until population density is very large. However, when the population density falls below a particular level mean free path increases so much that coalescence of droplets fails to occur within the residence time permitted. The main fact is that that the centrifuge can make separation only when there is coalescence. Hence, centrifuge technique substantially fails to work as intended when the slop oil contains either ultrafine oil droplets or highly viscous oil droplets containing solids and bound water therein.

Alternatively, use of filtration technique is also seen in the art for sludge treatment. For example, Canadian patent document CA1202223 to Amsted Industries Incorporated discloses a deep bed type filter containing gravity separator. The bed is agitated and dislodged oil entrapped in filter bed. Where the oil in the water is unusually viscous or has a waxy, tarlike, or sticky consistency, for example, rejuvenation of the filter bed is enhanced by the addition of a small amount of a solvating liquid to the oil-water mixture before filtering. Also, GB 1340931 to Beavon D K teaches a treatment method for oil-water mixture containing also oily particulate solids which is treated by passing it through a granular filter medium to remove the particulate solids wherein the filtrate obtained is being water or a mixture of water and oil. The next is to periodically solvate oil from the granular filter media by passing an oil stripping media through the bed in the same direction as the oil-water mixture without affecting the integrity of the filter medium followed by backwashing the filter to remove the now oil-free solids. The oil-water filtrate obtained may then be separated by gravity settling.

However, filtration technique substantially fails to produce oil free water without any chance of total separation of salable quantity of oil when there is large population of ultrafine droplets of sub-micron size. Further, the filtration technique is highly time consuming considering the pore size of the filtration medium. Moreover, regeneration of filtration medium is a highly tedious and time consuming task.

Optionally, coagulants or flocculants are also used to overcome above disclosed disadvantages of centrifuge and/or filtration. However, these coagulants/flocculants deteriorate or contaminate quality of oil. Moreover, the addition of coagulants and flocculants is a slow process and time consuming. Jf the oil droplets are held by water then neither filtration nor centrifuge will work unless the emulsifiers are used. For example, entire fats cannot be removed from milk by filtration or centrifuge because fats are hold by proteins which are emulsifier in this case.

Use of air flotation techniques for removal of emulsified oil particles was seen in the art. For example, a research paper entitled "The removal of emulsified oil particles from water by floatation" to Christine Angelldou et al., Ind. Eng. Chem. Process Des. Dev., 1977, 16 (4), pp 436^141, talks about use of air bubbles by air flotation technique for recovery of oil particles wherein the floatation of emulsified oil particles suspended in low concentrations in water has been studied. Two oils were used wherein the oil concentrations were up to 200 mg/L. To effect the separation various cationic surfactants were used in the flotation cell which was operated batch wise with an external total recycle. It was found that the rate of floatation in water was increased with addition of surfactant up to a limit. The presence of sea salt reduced the floatation rate. However, air flotation technique is not without limitations. Firstly, the air floatation is feasible only for the oil concentrations up to 200 ppm and it can never go beyond said ppm level. Secondly, these techniques make use of surfactant that highly contaminates the quality of oil and bound water. Further, removal of solid and bound water is impossible in the air floatation technique.

Accordingly, there exists a need of a process for treatment of a petroleum sludge that facilitates recovery of usable oil and usable water from the sludge considering enormous volumes of the sludge which is generally found as an untreated waste. Further, there exists a need of a process that removes bound water from the petroleum sludge apart from the use of de-emulsifiers which may work in rarest cases. In addition, there exists a need of a process for treatment of slop oil that facilitates recovery of usable water from the slop oil considering enormous volumes of the slop oil which is generally found as either physically dispersed in the water or bound to water through an emulsifier. Further, there exists a need of a process that converts waste slop oil into usable water by a cost effective way in addition to recovering usable oil therefrom.

Object of the Invention:

An object of the present invention is to remove bound and unbound water from petroleum/crude sludge and emulsions, comprising of hydrocarbons, bound water, unbound water, solids and dissolved salts into different pure salable streams.

Another object of the present invention is to provide a process for treatment of sludge that is cost effective and which facilitates recovery of pure oil and water as complete as possible without deteriorating original composition/ characteristics thereof.

Further object of the present invention is to provide a process for treatment of slop oil to recover usable water from slop oil by an effective and economically viable process.

Yet another object of the present invention is to recover usable hydrocarbons from the slop oil by an effective and economically viable process in addition to mitigating the problems of slop oil pollution.

Summary of the invention

In a preferred embodiment of the present invention, a process for treatment of a sludge mixture is disclosed wherein the sludge mixture includes hydrocarbons with bound water, unbound water, dissolved and un-dissolved solids therein. The process for treatment of the sludge mixture comprises a first step of centrifuging the sludge mixture in a first centrifuge provided if the sludge mixture splits into various components. The first centrifuge being a batch centrifuge forms a viscous hydrocarbon layer, a slop oil layer and a free flowing hydrocarbon layer. In next step, the viscous hydrocarbon layer is desalted in a first desalter followed by optional treatment thereof in a heat based low volatiles stripping vessel for removing vapors of low boiling liquid hydrocarbons therefrom. In next step, the vapors of low boiling liquid hydrocarbons are condensed in a first condenser for obtaining low boiling liquid hydrocarbons along with water for use. Optionally, the crude hydrocarbons coming from a group collection center are desalted in a second desalter for obtaining desalted product crude thereby removing bound water containing hydrocarbon layer that is subsequently mixed with the viscous hydrocarbon layer from the first centrifuge. In next step, the free flowing hydrocarbon layer is desalted in a third desalter for entire removal of salts therefrom. In next step, the viscous hydrocarbon layer is treated in a homogenizer by adding a first predefined amount of solvent for forming a volatiles free non-viscous homogenized stream therefrom. In next step, BTX and Ash tests of the non-viscous homogenized stream are performed followed by treatment thereof in an agitator cum homogenizer thereby adding a second predefined amount of solvent therein in accordance with the BTX and Ash tests results. In next step, the non-viscous homogenized stream is centrifuged in a second centrifuge for separating a bound water dominant hydrocarbon stream, unbound water dominant or water free hydrocarbon stream and the slop oil therefrom. Optionally, the non-viscous homogenized stream is treated in a hot insulated settling tank for removal of water free solvent along with hydrocarbons therefrom. In next step, the unbound water dominant or water free hydrocarbon stream is heated in a first heating vessel thereby optionally adding a predefined amount of free water. The first heating vessel operates at a first predefined temperature range thereby forming a first residual phase and a first vapor phase. In next step, the bound water dominant hydrocarbon stream is heated in a second heating vessel at a second temperature range thereby optionally adding a third predefined amount of additional solvent. The second heating vessel forms a second residual phase and a second vapor phase. In next step, the first residual phase is centrifuged in a hot centrifuge at a second predefined temperature for obtaining volatiles free desalted product hydrocarbons in a range of about 96 wt% to 100 wt% along with unbound water håving turbidity at least below 20 NTU. In next step, the second residual phase is treated in the first heating vessel. In next step, the first vapor phase and the second vapor phase are condensed through a second condenser for obtaining at least 100% solvent, the bound water in a range of about 99 wt % to 100 wt % and the free water in a range of about 94 wr% to 99 wt%. The solvent is reused in said process.

The first centrifuge reduces quantum of the sludge mixture with bound water that requires further processing which reduces cost and time of further processing. The free flowing hydrocarbon layer is about 41 wt% typically håving 3,864 ppm water and 0.88 wt. % ash with calorific value of 10,635 kcal/kg. The viscous hydrocarbon layer is håving at least 42.21 wt. % water typically håving 8.61 wt. % Ash with CV of 5,210 kcal/kg. The first centrifuge enhances separation between the components present in the sludge by extending a period of residence time of the sludge thereby gradually varying revolutions per minute of the batch centrifuge enabling collection of slop oil behind the viscous hydrocarbon layer.

The first desalter, the second desalter and the third desalter retain the quality of hydrocarbons coming from different process streams and hence improve commercial value thereof. The first desalter, the second desalter and the third desalter prevent needless repetition of identical processes done in the group collection center for removal of bound and unbound water from crude again into refineries after desalting of the crude. The first desalter, the second desalter and the third desalter prevent ingression of water into various product hydrocarbon streams in refineries thereby preventing accumulation of sludge in downstream of said process and vessels from refinery onwards processes. The first desalter, the second desalter and the third desalter allow the group collection center to dispatch crude without salts and without håving to worry about either disposal or processing of crude containing bound water. The first desalter, the second desalter and the third desalter prevent corrosion of pipelines and tankers during transportation. The heat based stripping vessel separates the low volatiles from the viscous hydrocarbon layer for preventing co-distillation thereof along with the solvent during removal of bound water with solvent in downstream of said process. Removal of the bound water from the viscous hydrocarbon layer also allows removal of heavy metal, Ash and salts therefrom which effectively improves commercial value thereof. The BTX and Ash tests help assists in determination of amount of solvent to be added in said process.

The solvent reduces viscosity for removal of bound water from topmost layer of the non-viscous homogenized stream on account of viscosity. The solvent help assists in homogenization of the sludge that in turn helps sampling and further helps in accurate determination of water and Ash content. The solvent is added in said process only for viscous portion of the hydrocarbons which substantially reduces overall use of solvent. The solvent is selected from the group of Benzene, Toluene, Xylene and similar Azeotropes of water. The solvent helps removal of the bound water from the top most layer and has least possible thermal damage to the product hydrocarbon stream in said top most layer. The solvent stream and the second centrifuge mutually remove substantial bound water from the viscous hydrocarbon layer at an ambient temperature. The solvent depresses the boiling point of the bound water. The solvent is added in a range of about 1.8 to 100 times the weight of water present in the sludge for removal of entire bound water. The solvent has a left over weight ratio of solvent to hydrocarbon in a minimum range of 2.00 to 6.00 for entire removal of the bound water at least temperature. The bound water obtained is high quality usable water that requires minimal treatment for being used as a drinking water. The first predefined temperature of the first heating vessel is in a range of about 90°C- 105°C. The second heating vessel is a multi effect evaporator preferably with thermal vapor recompression to avoid thermal cracking of the product hydrocarbon stream. The second heating vessel includes a foam breaker and an entrainment separator adapted to avoid entrainment of hydrocarbons in condensate. The first heating vessel includes a foam breaker and an entrainment separator adapted to avoid entrainment of hydrocarbons in the condensate. The second heating vessel maintains a controlled rate of heating with an optimum ratio of residual solvent to water for entire removal of bound water from the hydrocarbon. The first and second heating vessels are provided with waste heat for reducing cost of energy in said process.

The hot centrifuge is a hot settling tank that ensures adequate reduction in viscosity of hydrocarbons thereby allowing settling of free water present therein over a period of time. The hot centrifuge has a temperature in a range of about 80 °C to 94°C. The hot settling tank may be operated under high pressure so that operating temperature can be increased to further reduce the viscosity of hydrocarbon that will facilitate faster removal of free water without leading to boiling of water.

In an alternative embodiment of the present invention, a process for pre-treatment of slop oil is disclosed where the slop oil contains water, solids, salts and hydrocarbon content greater than 10,000 PPM with or without bound water. The process for pre-treatment of slop oil comprises an initial step of feeding the slop oil in a first settling tank for phase separation thereby forming a substantially unbound water-free hydrocarbon layer with or without salts, a water dominant hydrocarbon layer, and a slop oil layer håving hydrocarbon content less than 10,000 PPM. In next step, the water dominant layer is treated in a second settling tank by adding a predefined amount of alum therein. The second settling tank forms a substantially unbound water-free hydrocarbon layer, a gelatinous oil bearing layer and alum containing slop oil håving hydrocarbon content less than 10,000 PPM. Optionally, the gelatinous oil bearing layer is centrifuged in a third centrifuge by adding a predefined amount of solvent. The third centrifuge forms a solvent layer containing Alum along with solid coated with hydrocarbons. The solvent layer contains Alum that is being added to the first heating vessel in said process. The third centrifuge helps to quickly separate solvent cum hydrocarbon layers and gelatinous oil bearing layer from slop oil.

In yet another alternative embodiment of the present invention, a process for treatment of slop oil is disclosed wherein the slop oil contains water, solids, salts and limited hydrocarbon content less than 10,000 PPM with or without bound water. The process comprises an initial step of centrifugjng the slop oil through a fourth centrifuge for obtaining the slop oil with low turbidity by connecting most oil present in a thin top layer. In next step, the above slop oil from is treated in a high speed shear mixer by adding a solvent to form a mixture followed by centrifugjng thereof in a fifth centrifuge for obtaining a water dominant hydrocarbon layer and a solvent dominant hydrocarbon layer therefrom. In next step, BTX and Ash tests of the solvent dominant hydrocarbon layer are conducted for bound water followed by a heat treatment thereof in a third heating vessel and a fourth heating vessel. The third vessel has a predefined amount of solvent added therein. The fourth vessel is håving a predefined amount of free water added therein. The third heating vessel and fourth heating vessel separate a vapor phase from a liquid phase. The vapor phase is håving entire remaining solvent and free water therein. The liquid phase is håving hydrocarbons with limited solids, limited salts and alum therein. In next step, the liquid phase is centrifuged through a sixth centrifuge that is operating at a predefined temperature for separating a product hydrocarbon layer from a water layer. The water layer is håving limited salts, limited solids and alum therein. In next step, the water layer is treated through a first reverse osmosis plant for obtaining water for use and a reject stream. In next step, the vapor phase is condensed through a third condenser for obtaining water for use and solvent that can be reused in the high speed shear mixer. In next step, the water dominant hydrocarbon layer is heated in a fifth heating vessel for separating vapors of solvent therefrom followed by condensing thereof in the third condenser to obtain solvent for reuse and water for use. The fifth heating vessel produces a liquid phase that includes remaining water, limited hydrocarbons, salts and solids with a substantially low turbidity. In next step, the liquid phase is treated in a settling tank followed by addition of a predefined amount of alum therein. The settling tank forms a water dominant alum layer and a gelatinous oil bearing layer.

In next step, the water dominant alum layer is filtered in a filtration unit. The filtration unit separates the water dominant alum layer into a filtrate stream and a residual stream. The filtrate stream includes water, alum and salts therein. The residual stream includes wet solids with traces of hydrocarbons, salts and alum. The filtrate stream is treated in a second reverse osmosis plant for recovering usable water therefrom. The filtration unit in accordance with the present invention brings down the turbidity value of the slop oil below 1 NTU. Effectiveness of filtration depends on pore size of the filtrate media and nature of hydrocarbons present in the slop oil.

In next step, the residual stream is mixed with the gelatinous oil bearing layer followed by drying thereof in a first hot dryer for obtaining a viscous liquid containing hydrocarbons, alum, solids and salts. In next step, the viscous liquid is agitated in an agitator cum de-oiling unit by adding a predefined solvent followed by treatment thereof through a seventh centrifuge thereby adding water therein. The seventh centrifuge provides a water layer, a cake layer and a solvent layer, the water layer håving alum, salts and limited solvent therein. The cake layer is preferably a cake of de-oiled solids with solvent, limited salts and limited alum. The water is treated in a sixth heating vessel for obtaining vapors of solvent and water followed by treatment thereof through a fourth condenser for obtaining solvent for reuse and water either for use or for further treatment in said process. In next step, the solvent layer is treated in the fourth heating vessel for recovery of solvent. In next step, the cake layer is treated in a second hot dryer for recovery of solvent through the condenser. The second hot dryer produces dried de-oiled solids håving traces of alum and salts therein.

The third heating vessel is a multiple effect evaporator preferably with thermal vapor recompression adapted to avoid thermal cracking of the product hydrocarbon. The third heating vessel has a temperature in a range of about 70 °C- 150 °C. The fourth heating vessel has a temperature in a range of about 90 °C to 105 °C. The fifth heating vessel has a temperature in a range of about 90 °C to 105 °C. The sixth centrifuge is a hot centrifuge that has a temperature of about 80 °C to 94 °C. The sixth centrifuge is a hot settling tank that has a temperature of about 80 °C to 94 °C. The hot settling tank may be operated under high pressure so that operating temperature can be increased to further reduce the viscosity of hydrocarbon that will facilitate faster removal of free water without leading to boiling of water. The sixth heating vessel is an evaporator. The sixth heating vessel has a temperature in a range of about 90 °Ctol05 °C.

The BTX study and Ash study help assists in determination of amount of solvent to be added in said process. The solvent is selected from the group of Benzene, Toluene, Xylene and other azeotropes of water. The first hot dryer has a temperature of about 108 °C. The second hot dryer has a temperature of about 200 °C. The first reverse osmosis plant removes alum, salts and solids to produce water of usable quality. Addition of alum in the second settling tank neutralizes surface charge which facilitates speedy separation of the hydrocarbons through flocculation and formation of the gelatinous oil bearing layer. Addition of alum in third settling tank when the slop oil is håving turbidity below 90 NTU electrically discharge finest droplets of the hydrocarbons and flocculate them thereby reducing turbidity by in a range of 90 wt.%- 99 wt.%. Addition of alum is slow process by itself but it can be speeded up by applying heat such that effectiveness of alum treatment is dependent on temperature and time.

The fourth centrifuge is a multi-pass centrifuge that reduces turbidity value of slop oil to a limiting value beyond which centrifuge is unable to produce any further value addition because then size variations of dispersed oil droplets become narrow and population density of dispersed oil droplets also falls with increase in mean free path, residual droplets are electrically charged and density difference is very small. The above lacuna for centrifuge gets magnified when starting turbidity value of the slop oil is very high. The solvent is added through the high shear mixer when centrifuge reaches its limiting value. Addition of solvent enhances the operating range of centrifuge by bringing in large variation in droplet size and also by increasing the population density of droplets along with increasing density difference between oil and water. The centrifuge again reaches a limiting value at that point the residual solvent is boiled out with free water in a temperature range of about 90 °C to 99 °C.

In further alternative embodiment of the present invention, a process for treatment of a sludge mixture comprising of a centrifuge is disclosed. The process for treatment using only centrifuge comprises a step of centrifuging the sludge containing hydrocarbons, bound water, salts and solvents in a centrifuge to break the binding between hydrocarbons by increasing residence time of the hydrocarbons in the centrifuge thereby forming three different layers, namely a viscous hydrocarbon layer with bound water, salts and solids, a free flowing hydrocarbons layer with limited salts and solids and a free water with limited solids and salts. The centrifuge repositions the viscous hydrocarbon layer from a back side to a middle side of the centrifuge by slowly increasing revolutions per minute thereof and slowly decreasing an angle between a vertical axis of centrifuge container and a horizontal plane thereof by gradually reducing but not allowing it to become 0°. The sludge mixture has bound water requiring further processing which reduces further processing cost and time. The centrifuge gives a large amount of marketable product hydrocarbons, namely free flowing hydrocarbons.

In yet another embodiment of the present invention, a process for treatment of sludge mixture with combined effect of centrifuge and solvent is disclosed wherein the sludge mixture contains bound water, salts and solids therein. The process for treatment comprises an initial step of adding of a predefined amount of solvent in the sludge mixture followed by mixing thereof to reduce the viscosity of the sludge mixture. In next step, the sludge mixture is centrifuged in the centrifuge to obtain a large layer of solvent and hydrocarbon, a layer containing hydrocarbons and bound water and a free water layer. The centrifuge has an extended residence time for getting less of sludge with bound water therein. The large layer of solvent and hydrocarbon is treated for recovery of solvent by boiling through free water in a temperature range of 90 °C to 99 °C at an atmospheric pressure. The sludge mixture has bound water requiring further processing reduces thereby saving further processing cost and time. The centrifuge gives a large amount of marketable product hydrocarbons, namely free flowing hydrocarbons.

Brief Description of Drawings

FIG. 1 is a process flow diagram showing production and collection of crude at a group collection center; FIG. 2 is a process flow diagram showing treatment of a sludge mixture of FIG. 1 prior to removal of bound water therefrom; FIG. 3 is a process flow diagram showing treatment of the sludge mixture of FIG. 2 for removal of bound water therefrom; FIG. 4 is a process flow diagram showing treatment of slop oil with hydrocarbon content above 10,000 PPM; FIG. 5 is a process flow diagram showing treatment of the slop oil with hydrocarbon content equal to or less than 10,000 PPM; FIG. 6 is a continued process flow diagram of FIG.5 showing treatment of the slop oil with hydrocarbon content equal or below 10,000 PPM; FIG. 7 shows a graphical representation of Benzene at a rate of 2500 PPM when mixed with water using high shear mixer for 1 minute; FIG. 8 shows a graphical representation of Benzene at a rate of 5000 PPM when mixed with water using high shear mixer for 1 minute; FIG. 9 shows a graphical representation of Toluene at a rate of 2500 PPM when mixed with water using high shear mixer for 1 minute; FIG. 10 shows a graphical representation of Toluene at a rate of 5000 PPM when mixed with water using high shear mixer for 1 minute; FIG. 11 shows a graphical representation of Xylene at a rate of 2500 PPM when mixed with water using high shear mixer for 1 minute; FIG. 12 shows a graphical representation of Xylene at a rate of 5000 PPM when mixed with water using high shear mixer for 1 minute; FIG. 13 shows a graphical representation of Coconut Oil at a rate of 2500 PPM when mixed with water using high shear mixer for 1 minute; FIG. 14 shows a graphical representation of Coconut Oil at a rate of 5000 PPM when mixed with water using high shear mixer for 1 minute; FIG. 15 shows a graphical representation of Coconut Oil at a rate of 2500 PPM when mixed with water using high shear mixer for 3 minutes; FIG. 16 shows a graphical representation of Coconut Oil at a rate of 2500 PPM when mixed with water using high shear mixer for 5 minutes; FIG. 17 shows a graphical representation of ONGC Oil at a rate of 2500 PPM when mixed with water using high shear mixer for 1 minute; FIG. 18 shows a graphical representation of ONGC Oil at a rate of 5000 PPM when mixed with water using high shear mixer for 5 minutes; FIG. 19 shows a graphical representation of ONGC Oil at a rate of 2500 PPM when mixed with water using high shear mixer for 3 minutes; FIG. 20 shows a graphical representation of ONGC Oil at a rate of 2500 PPM when mixed with water using high shear mixer for 5 minutes; and FIG. 21 shows a graphical representation of Diesel at a rate of 2500 PPM when mixed with water using high shear mixer for 5 minutes.

Detailed Description of the Invention:

The invention described herein is explained using specific exemplary details or berter understanding. However, the invention disclosed can be worked on by a person skilled in the art without the use of these specific details.

References in the specification to "one embodiment" or " an embodiment" means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

References in the specification to "preferred embodiment" means that a particular feature, structure, characteristic, or function described in detail thereby omitting known constructions and functions for clear description of the present invention.

In the description and in the claims, the term "Sludge" is defined broadly as a mixture of hydrocarbons, bound and unbound water, dissolved and undissolved solids and naturally occurring emulsifiers. The sludge in accordance with the present invention is a sludge that contains total water content is in a range of 2 wt% to 95 wt%. However, when total water content is in a range of 2 wt% to 61 wt%, the entire water in the hydrocarbons is bound water when emulsifiers are not additionally added. When the water content is above 61% the water is combination of both bound water and unbound water. Sludge is deadly pollutant as it contains heavy metals and getting rid of is an expensive affair. It can pollute ground, water and even air through low volatiles.

In the description and in the claims, the term "Slop oil" is defined broadly as a mixture of hydrocarbons, emulsifiers, un-dissolved solids, hydrocarbon coated un-dissolved solids and dissolved solids, bound and unbound water. The slop oil in accordance with the present invention is håving hydrocarbon content in a range of 5 ppm- 5 lac ppm. These hydrocarbons are not water soluble. Often when oil content extends beyond 10,000 PPM, it will reasonably quickly spilt into 3 layers, a decantable top layer of pure oil with PPM level of water, a significant water bearing oil in the middle where separation rate of pure oil is slow and a residual bottom layer which is slop oil containing less than 10,000 PPM.

In the description and in the claims, the term "Bound Water" is defined broadly as water that does not come out hydrocarbon inspite centrifuging the sludge at 21893 RCF for at least 10 minutes is bound water.

In the description and in the claims, the term "Unbound Water" is defined broadly as any water apart from bound water.

In the description and in the claims, the term "Dissolved Solids" is defined broadly as the solids that are dissolved in the water that comes out with sludge.

In the description and in the claims, the term "Un-dissolved Solids" is defined broadly as the heavy metals including radioactive metals that come out from oil well along with crude.

Referring to FIG.l, a process flow chart 100 shows a process undergone by a petroleum crude 102 after being recovered through a plurality of oil wells 101 followed by processing thereof at a group collection center 104 (GCC, hereinafter) as illustrated. The crude 102 preferably contains sulfur, bound water, unbound water, salts and solids. However, gases, if any, are removed from the crude 102 at line 101A before being sent to GCC 104. The GCC 104 includes a desulfurization plant 106 that separates out sulfur from crude 102 via line 108 thereby forming a sulfur-free crude stream 110 containing crude with bound water, unbound water, salts and solids. The sulfur-free crude stream 110 is fed to a gravity based settling tank 112. The gravity based settling tank 112 separates crude into three streams namely an upper crude stream 114, a middle crude stream 116 and a lower crude stream 118. The upper crude stream 114 contains crude with salts, limited solids and traces of water that follows line-A. The lower crude stream 118 contains water with salts, solids and limited crude that follows line-B. It is understood here that lower crude stream 118 is slop oil stream håving less than 10,000 PPM hydrocarbon content in this one preferred embodiment. The middle crude stream 116 contains crude with salts, bound water, unbound water and solids that is fed to a hot insulated settling tank 120 through line 119.

The hot insulated settling tank 120 operates at an atmospheric pressure and at a temperature at about or less than 95 °C. A de-emulsifier 122 is optionally added to the hot insulating settling tankl20 through linel24. In addition, a high voltage oscillating electric field 125 is given to the hot insulating settling tank 120 in this one embodiment. The hot insulated settling tank 120 treats the middle crude stream 116 thereby forming three layers therein, namely a top crude layer 126, a middle crude layer 128 and bottom crude layer 130. The top crude layer 126 contains crude with salts, limited solids and traces of water that follows line-A. The bottom crude layer 130 contains water with salts, solids and limited crude that follows line-B. In this one embodiment, the bottom crude layer 130 is slop oil håving less than 10,000 PPM hydrocarbon content. In this one preferred embodiment, the middle crude layer 128 is preferably sludge in accordance with the preferred embodiment which contains crude with bound water, salts, limited unbound water and limited solids. Accordingly, the sludge 128 follows line-C in this one preferred embodiment.

Referring to FIG. 2, a process 200 for treatment of the sludge 128 before removal of bound water therefrom is illustrated. The sludge 128 is fed to a first centrifuge 202 through the line-C. Additionally, a plurality of sludges 204 from all other sources with/ without salts is added to the first centrifuge 202 along with the sludge 128. The first centrifuge 202 is a batch type or multi-pass centrifuge in this one preferred embodiment. The first centrifuge 202 forms three layers, namely a top layer 208, a middle layer 206 and a bottom layer 210. The bottom layer 210 preferably contains water with salts, solids and limited crude. The middle layer 206 is preferably a viscous hydrocarbon layer with bound water, limited solids and traces of unbound water with/without salts. The top layer 208 preferably contains free flowing hydrocarbons with or without salts, limited unbound water and limited solids. In this one embodiment, the bottom crude layer 210 is slop oil håving less than 10,000 PPM hydrocarbon content.

The middle layer 206 is preferably fed to a first desalter 212 through line 211 if it contains salts. A predefined amount of free water is added to the first desalter 212 in order to obtain an upper stream 213 and a lower stream 214. The lower stream 214 preferably contains water with salts, solids and limited crude which is mixed with bottom layer 210 in this one embodiment. The upper stream 213 preferably contains desalted viscous hydrocarbons with bound water, limited unbound water and limited solids. The upper stream 213 follows line 213-A in this one embodiment. Alternatively, the middle layer 206 can be directly fed to a homogenizer 216 through line 215 if the middle layer 206 is without salts and low volatiles. It is understood here that the line 215 may be mixed with the line 213-A before being fed to the homogenizer 216.

The top layer 208 is preferably fed to a third desalter 218 through line 217 if it contains salts. A predefined amount of free water is added to the third desalter 218 in order to obtain either two or three layers. The third desalter 218 produces an upper layer 220, a bottom layer 222 and optionally a middle layer 224 if it has a fraction håving bound water contained therein. The upper layer 220 is a free flowing salt free hydrocarbon product with limited solids and traces of water. The bottom layer 222 contains water with salts, solids and limited crude that follows line-B. In this one embodiment, the bottom crude layer 222 is slop oil håving less than 10,000 PPM hydrocarbon content. The middle layer 224, if formed, is added to the upper stream 213 in this one embodiment.

The crude stream 114 containing crude with salts, limited solids and traces of water following line-A (refer FIG. 1) is fed to a second desalter 228. The second desalter 228 preferably forms three layers, namely a top layer 230, a middle layer 232 and a bottom layer 234. The bottom layer 234 contains water with salts, solids and limited crude that follows line-B. In this one embodiment, the bottom crude layer 234 is slop oil håving less than 10,000 PPM hydrocarbon content. The top layer 230 is a desalted product crude with traces of solids and water which goes back to refinery as a product. The middle layer 232 contains desalted viscous hydrocarbons with bound water that is added to the stream 213 and fed to the homogenizer 216.

The homogenizer 216 treats desalted viscous hydrocarbon layer with bound water, limited unbound water and limited solids thereby adding a limited solvent stream 236 in case where the hydrocarbons are highly viscous. The homogenizer 216 advantageously facilitates addition of solvent only after reducing volume of sludge and specifically for viscous hydrocarbon portion thereby drastically reducing overall use of solvent in the process. The solvent is also added to the homogenizer 216 in order to help assist in BTX study being performed during the process. The solvent 236 also helps assists in reducing viscosity for removing bound water on account of viscosity. In this one preferred embodiment, the solvent 236 is selected from one or more of the following Benzene, Toluene and Xylene. The homogenizer 216 produces a non-viscous homogenized stream 238 that follows line-D as illustrated. The stream 238 preferably contains hydrocarbons that are volatiles free, desalted and non-viscous. The hydrocarbons in the non-viscous homogenized stream 238 preferably contain bound water, limited unbound water and limited solids contained therein.

Optionally, a heat based low volatiles stripping vessel 240 may be employed if the desalted viscous hydrocarbons in the stream 213 contain low boiling volatiles therein. In such case, the stream 213 is sent to a heat based low volatiles stripping vessel 240 via line 242 instead of being sent to homogenizer 216 via line 213-A. However, the viscous hydrocarbon layer 206 may be directly fed to the heat based low volatiles stripping vessel 240 through line 244 if it is free from salts but contains only low volatiles therein. The heat based low volatiles stripping vessel 240 is adapted in the process 200 to prevent the low volatiles to come out with solvent by separation thereof which would otherwise contaminate the solvent and removal of these hydrocarbons later on would need fractional distillation which would be needlessly a costlier affair. Hence, the heat based low volatiles stripping vessel 240 is adapted in the process to separate the low volatile hydrocarbons. The heat based low volatiles stripping vessel 240 is provided with a waste heat to facilitate heating. The heat based low volatiles stripping vessel 240 forms a vapor phase 246 and a liquid phase 248. The vapor phase 246 preferably contains vapors of low volatiles, hydrocarbons and water. The liquid phase 248 preferably contains volatiles free, desalted hot hydrocarbons with bound water, limited unbound water and limited solids.

The vapor phase 246 is sent to a first condenser 250 for removing heat therefrom followed by processing through a first condensate/phase separator 252. The condensate/phase separator 252 preferably forms a first layer 254, a second layer 256 and a third layer 258. The first layer 254 contains pure water that can be reused in the process or packed for sale. The second layer 256 contains low boiling liquid hydrocarbons that are mixed with a desalted product crude 230 through line 260. The third layer 258 contains non condensable vapors of hydrocarbons that are flared as a source of heat via line 262 as illustrated.

The liquid phase 248 is fed to a cooling vessel 264 wherein the hot hydrocarbons are cool ed to a room temperature and added to the homogenizer 216 via line 266 to subsequently produce the product stream 238 which follows line-D as illustrated.

It is understood here that, in case of typical sludge from ONGC lagoons, the first centrifuge 202 is able to separate sludge wherein one can find a small fraction of viscous hydrocarbons floating on the top carrying about 40-44 wt% bound water and 13% Ash. The free flowing hydrocarbons about 40 wt% are obtained which contains 0.3 wt% to 0.8 wr% Ash and less than 3000 ppm of water. The water that goes out is håving turbidity well below 20 NTU. One cannot add this water back to the hydrocarbons and make sludge thereby preventing reconstitution.

Referring to FIG. 3, a process 300 for treatment of the product stream 238 for removal of bound water is illustrated. The product stream 238 (refer FIG. 2) is fed to an agitator cum homogenizer 306 through the line-D after performing a BTX study 302 and an ash content study 304. The BTX study 302 is performed to detect moisture content in the product stream 238 and the ash content study 304 is performed to detect ash content in the product stream 238. A calculated amount of solvent 308 is added in the agitator cum homogenizer 306 through line 310. It is understood here that the quantum of solvent added has an impact in the agitator cum homogenizer 308 in order to bring out the water at least temperature from the hydrocarbons. In case of Xylene being used as solvent, preferably, ratio of Xylene to wt. of hydrocarbon/water (whichever is higher) is 5.5. In case of Toluene being used as solvent, preferably, ratio of Toluene to wt. of hydrocarbon/water is 10.0. In case of Benzene being used as solvent, preferably, ratio of Benzene to wt. of hydrocarbon/water is 80.0.

In next step, the contents in the agitator cum homogenizer 306 are fed to a second centrifuge 312 through line 311. Optionally, the contents in the agitator cum homogenizer 306 are fed to a hot insulating tank 312A that separates out a water free top layer 312B containing solvent and hydrocarbons. The water free top layer 312B follows line-J as shown. The second centrifuge 312 splits the contents in three layers, namely a first layer 314, a second layer 316 and a third layer 318. The first layer 314 is an unbound water dominant hydrocarbon stream that preferably contains volatiles free desalted hydrocarbons, solvent, limited unbound water and solids contained therein. The second layer 316 is a bound water dominant stream that preferably contains volatile free desalted hydrocarbons with bound water, solvent, limited bound water and solids contained therein. The third layer 318 preferably contains water with solids, limited hydrocarbons and solvent that follows line-B. It is understood here that the contents in the hot insulating tank 312A may be mixed with the third layer 318 via line 312C. In this one embodiment, the third layer 318 is slop oil håving less than 10,000 PPM hydrocarbon content.

It is understood here that in homogenizer 306 one puts hydrocarbons for the treatment with up to 61% bound water wherein the difference in density between water and hydrocarbon is in a region of 0.05 gm/cc and containing bound water which does not come out of the first centrifuge 202 in spite of 21900 RCF for 10 minutes. However, after adding solvent 308 followed by reduction in viscosity in the second centrifuge 312 the entire bound water comes out in subsequent processing. It is understood here that the same hydrocarbon had undergone similar centrifugal action in first centrifuge 202 where viscosity was reduced still the bound water that is recovered here had not come out. This fact of recovery of bound water is a discovery in accordance with the present invention.

The first layer 314 is fed to a first heating vessel 320 through line 322. The first heating vessel 320 operates at an atmospheric pressure and a temperature range of about 90°C to 105°C, more preferably in a range of about 90 °C - 98 °C, in this one preferred embodiment. A predefined amount of free water is added to the first heating vessel 320 and waste heat is supplied for heating the first heating vessel at the desired temperature in order to produce a first residual phase 324 and a first vapor phase 326. In case where hydrocarbons have salt and/or ash or solids therein, then free water may perform an additional function of de-salting and de-ashing apart from boiling out entire pure solvent for re-use or sale at temperatures below 100°C. The first vapor phase 326 preferably contains vapors of entire remaining solvent and part of unbound water which is fed to a second condenser 328 where heat is removed from the vapors to form a liquid phase that moves to second condensate phase separator 330 through line 329. The condensate phase separator 330 separates the liquid phase into a solvent phase 332 and a water phase 334. The solvent phase 332 is preferably reused in the process. The water phase 334 is pure water håving turbidity less than 5 NTU which is either recycled in the process or packed for sale. The first residual phase 324 preferably contains hydrocarbons and remaining unbound water with limited solids that is fed to a hot centrifuge/ hot settling tank 336. The hot centrifuge 336 operates at an atmospheric pressure and preferably at an inlet temperature less than or equal to 95°C and more preferably at the inlet temperature of 92 °C -93 °C. The hot centrifuge 336 preferably separates the liquid stream 324 into two layers, namely a top layer 338 and a bottom layer 340. The top layer 338 preferably contains volatiles free desalted hydrocarbon product with traces of water/solids håving water content less than 5000 ppm. The bottom layer 340 entirely contains unbound water with solids and traces of hydrocarbons. The bottom layer 340 is mixed with water phase 334 via line 341 if it has turbidity less than 5 NTU. Alternatively, the bottom layer 340 is fed to an alum based settling tank 342 via line 343 if the turbidity is greater than 5 NTU. The alum based settling tank treats the water to bring the turbidity below 5 NTU followed mixing thereof with water phase 334 via line 344. It is understood here that Alum based settling tank 342 may be a filtration unit or a reverse osmosis plant in other alternative embodiments of the present invention.

The second layer 316 is fed to a second heating vessel 346 through line 348 that operates at an atmospheric pressure and preferably in a temperature ranges of about 70 °C -150 °C wherein waste heat is applied for heating purpose. However, it is understood that the second heating vessel 346 may be a multi effect evaporator with thermal vapor recompression alternative embodiment of the present invention. Also, it is understood that the second heating vessel 346 may be a foam breaker and entrainment suppressor in yet another embodiment of the present invention. A predefined of solvent may be added to the second layer 316 if required. The second heating vessel 346 forms a second vapor phase 350 and a second residual phase 352. The second vapor phase 350 contains vapors of solvent with entire bound water and unbound water which is fed and processed through the second condenser 328 as per the treatment process of vapor phase 326 as stated above. The second residual phase 352 is added the first heating vessel 320 and processed therethrough as illustrated.

Now referring again to FIGS. 1- 3, in operation, the first centrifuge 202 advantageously allows rapid separation of the sludge into value added layers at ambient temperature wherein typical CV of incoming sludge is about 6,044 kcal/kg with water content about 40 wt. % and ash content about 3.68 wt. %. The first centrifuge substantially reduces the mass of the sludge to be handled subsequently by more than 3 times followed by separating in-coming hydrocarbons into two fractions that commands different market price and in all probability different subsequent treatment. Particularly, the first centrifuge 202 operates for 10 minutes at relative centrifugal force (RCF, hereinafter) of 4,500 (which requires cycle time of 30 mins.) to produce about 41 wt.% of the free flowing hydrocarbon layer 220 with 3,864 ppm water and 0.88 wt.% ash håving CV of 10,635 kcal/kg, about 32 wt% of the viscous hydrocarbon layer 206 håving 42.21 wt.% water and 8.61 wt.% ash with CV of 5,210 kcal/kg, and 26 wt.% of the slop oil after subsequent treatment with Alum håving less than 20 NTU turbidity.

In operation, the first centrifuge 202 enhances force of buoyancy over extended time by gradually increasing the RPM and also by håving centrifuge bottles held onto rotor through a pivot. The first centrifuge 202 provides an extended residence time with enhanced force of buoyancy that allows building up of an adequately large Kinetic Energy differential between droplets of separating liquids, which then, on exceeding a threshold value, provides the energy needed to break the bonds that were holding these droplets together. Breaking of bonds was necessary but not adequate. Subsequently, these different materials are carried as entirely as possible through one another and collect them into distinct, single component layers 206, 208 and 210. The enhanced or increased residence time or centrifugal force squeezes out more water and to a small extent even oil from viscous layer 213 and by doing so makes it even further viscous and hence reaching a limiting point beyond which it did not make sense to try any further. The Combination of progressively increasing RPM and of pivots holding centrifuge bottles probably had a couple of additional impacts. Initially, a less RPM which is low centrifugal force limits accumulation of viscous hydrocarbons that helps in collection of the viscous hydrocarbons as lumps without flattening thereof as cakes. Further, a low RPM wherein the force of weight is larger than centrifugal force helps collection of the viscous hydrocarbons at the bottom-most space within bottles thereby leaving behind ample free space at top. This helps initially released weakly bound water to reach the extreme end and then collect behind these lumps. The viscous hydrocarbons preferably grow with time as additional material accreted. Subsequently, more water releases and collects behind viscous lumps from top thereby releasing them from the base of the bottle and then slowly moving them towards their final position in the centre. Further, when RPM rises, the force of buoyancy increases to swivel out the bottles progressively by reducing their angle with horizontal and with that above described process became more vivid. Eventually, these bottles become near horizontal but never completely horizontal. At the end, there will be some small residual angle with the horizontal. Eventually the centrifuge 202 allows the viscous hydrocarbon to get flattened with time and high centrifugal force into thick dise shaped layer. But even then since these bottles are never truly horizontal this dise has a limited contact with bottle surface at its topmost point which provides a relatively easy opening for water to penetrate in and collect behind it.

In operation, the three desalters 212, 218, 228 facilitate de-salting of crude prior to removing bound water and also prior to dispatching it to refineries. This has a special importance in accordance with the present invention. The process 200 includes placement of desalters 212, 218 and 228 allow crude de-salting at the specific location within the proposed process which is different from its current location. The desalters 212, 218 and 228 prevent needless, expensive, time-cum-capital consuming repetition of crude de-Watering at refineries, after first carrying out exactly similar process earlier at GCCs. Besides, the desalters 212, 218 and 228 enhance product quality and reduce expense on paid energy, by preventing ingression of water into crude stream at refineries. This in turn reduces or eliminates sludge accumulation in down-stream product supply chain. The desalters 212, 218 and 228 at our disclosed location of the process 200 facilitates mitigation of the problem of bound water that gets into Crude while de-salting, without håving the advantage of distillation column. The desalters 212, 218 and 228 prevent mixing of hydrocarbons håving bound water with hydrocarbons håving unbound water and the product hydrocarbon stream in comparison to mere de-salting. This also allows preventing mixing of viscous hydrocarbons with free flowing hydrocarbons. The second desalter 228 has unique ability to dispatch de-salted hydrocarbons to refineries without loading them with bound water.

In operation, the heat based low volatiles stripping vessel 240 facilitate stripping in case of hydrocarbons coming in with bound water and low-boiling volatiles. The stripping vessel 240 strip these low volatiles and separate them by heating prior to removal of bound water using solvents and even prior to addition of solvent itself in the process 200 thereby preventing the low boiling volatiles to distill out with the solvent during removal of bound water with solvent in downstream of the process 200 wherein depending on the solvent used the final temperature could rise at least as high as 140 °C. The stripping vessel 240 also prevents the low volatiles to enter in subsequent purification of the solvent which would otherwise become a far more expensive & elaborate a process. Further, the heat based low volatiles stripping vessel 240 prevents low boiling volatiles to distill out with the solvent during removal of bound water subsequently with the use of solvent in the homogenizer 306 and the second centrifuge 312 followed by exposure to temperature of at least as high as 98°C in the first heating vessel 320. The heat based stripping vessel facilitates recovery of the low boiling hydrocarbons that can be recycled back to the desalted product crude 230 which apart from conservation and economical advantages help to deliver back the hydrocarbons in as original form as possible. If a fraction of low volatiles becomes non-condensable stream 258 due to thermal cracking then that fraction would be either flared or combusted to provide an additional source of heat.

Moreover, addition of solvent before the second centrifuge 312 is more important instead of addition of solvent before the first centrifuge 202. This is partly because one would end up consuming more solvent in such case as it will get needlessly mixed also with the free flowing hydrocarbons. This may lead to an additional cost and process for subsequent removal of the solvent from free flowing hydrocarbons. Moreover, the removed solvents would get contaminated with low boiling hydrocarbons in such case. Also, one would end up mixing low valued viscous hydrocarbons with higher valued free flowing hydrocarbons in such case.

In operation, the second centrifuge 312 treats the solvent bearing sludge after removing the clear water with turbidity values from below 20 NTU in certain cases. The second centrifuge 312 removes entire remaining bound water from the sludge stream fed thereto such as Furnace Oil Sludge, ONGC Viscous Hydrocarbons and the like. The second centrifuge 312 does not remove the entire bound water from the sludge where a part of hydrocarbons holds onto bound water on account of emulsifier. Apart from removing bound water, the second centrifuge also helps in reducing ash in hydrocarbons.

However, it is understood here that mere use of the second centrifuge 312 alone and without solvent could not remove traces of bound water inspite of high residence time of 10 minutes at an RCF value as high as 21,900 because of high drag on account of high viscosity. The use of solvent stream 308 is extremely important to reduce viscosity and to make the centrifuge 312 effective when used subsequently. On the other hand, solvent by itself is more effective than the centrifuge 312 but still it fails to remove entire bound water inspite of 72 hours of residence time as part of the water is tightly held by hydrocarbons. Bound water could not be separated either by the use of solvent alone, even when heated to temperatures a little below their azeotropic boiling temperature or by the use of centrifuge alone.

Accordingly, combined use of solvent stream 308 with second centrifuge 312 to separate bound water completely and quickly at ambient temperatures from the viscous sludges is extremely important in accordance with the present invention. The process 300 combines the enhanced force of buoyancy due to increased acceleration due to gravity and additionally a significant decrease in viscosity of the sludge by using the solvent, like Xylene, that is in proportion of two times the weight of sludge itself at ambient temperatures and over an extended period of time thereby affecting complete separation of bound water from viscous hydrocarbons which is hitherto not possible either by singly using even 4.87 times more powerful a centrifuge over same time alone or by singly using the same solvent in similar proportion even at twice the ambient temperature over 72 hours as against 10 minutes.

Referring to FIG. 4, a process 400 for pretreatment of the slop oil in accordance with an alternative embodiment of the present invention is shown. The slop oil stream 402 has hydrocarbon content greater than 10,000 PPM. In this one alternative embodiment, the slop oil feed stream 402 preferably contains water with salts, solids and limited hydrocarbons with or without bound water. The slop oil feed stream 402 is sent to a first settling tank or a phase separation column 404 wherein preferably three layers are formed, namely a top layer 406, a middle layer 408 and a bottom layer 410. The top layer 406 preferably contains free flowing hydrocarbons with or without salt along with traces of water and solids. The middle layer 408 preferably contains hydrocarbons with large amounts of water with or without salts and solids. The bottom layer 410 preferably contains water with salts, solids, limited hydrocarbons which follows line-B. In this one alternative embodiment, the bottom layer 410 is slop oil håving less than 10,000 PPM hydrocarbon content. The top layer 406 is directly stored as a product storage tank 412 through line 411 if it does not contain any traces of salts therein. Alternatively, the top layer 406 may be optionally fed to third desalter 218 (refer FIG. 2) via line F if it contains salts therein. The middle layer 408 is fed to a second settling tank 414 followed by adding a predefined amount of alum.

The second settling tank 414 forms a first layer 416, a second layer 418 and a third layer 420. The first layer 416 preferably contains free flowing hydrocarbons with or without salts and traces of water and solids which is mixed with the top layer 406 in this one embodiment. The second layer 418 mainly contains alum with water håving salts, solids, limited hydrocarbons. The second layer 418 is mixed with the bottom layer 410 to follow line-B as illustrated. The third layer 420 is a gelatinous oil bearing layer containing hydrocarbons, alum, salts, solids and water contained therein. The third layer 420 follows line-H. It is understood here that addition of alum in the second settling tank 414 facilitates speedy separation of the hydrocarbon through coagulation and formation of the gelatinous oil bearing layer.

The first settling tank 404 may occasionally produce a fraction 422 which may contain viscous hydrocarbons with or without salts/ solids/ bound water. The fraction 422 may be optionally fed to a first desalter 212 via line- I if it contains salts and bound water both. The fraction 422 may be optionally fed to second desalter 228 by mixing with line-A if it contains salts without any bound water therein. The fraction 422 may be optionally mixed with an upper stream 213 via line-E if it contains only bound water without any salts therein. The fraction 422 may be optionally sent to a third centrifuge 424 via line 423 if it contains only solids without any salts and bound water therein. A predefined amount of solvent is added to the third centrifuge 424 in order to separate the fraction 422 into two layers, namely a top layer 426 and a bottom layer 428. The third centrifuge 424 reduces drag, surface charge on the particles of hydrocarbon thereby reducing mean free path and allowing coalescence of the particles at ambient temperature. The top layer 426 preferably contains hydrocarbons and solvent with traces of solids which is sent to the first heating vessel 320 via line- J. The bottom layer 428 preferably contains solids that are coated with hydrocarbons which follows line-K in this one embodiment. However, the bottom layer 422 may be directly stored as a product 430 via line 429 if it is free from salts, solids and bound water.

Referring to FIGS. 5-6, a process 500 for treatment of the slop oil following line-B in accordance with the present invention is shown. The slop oil stream 502 preferably has a high turbidity and hydrocarbon content less than 10,000 PPM. In this one embodiment, the slop oil stream 502 preferably contains water with salts, solids and limited hydrocarbons with or without bound water. The slop oil feed stream 502 is fed to a fourth centrifuge 504 to reduce turbidity and obtain a stream 506 håving low turbidity. The fourth centrifuge 504 is a multipass centrifuge that works on its own as long as population density of ultrafine particles of hydrocarbons is high because then mean free path is low. Because, ultrafine particles can be removed only after they coalesce and for coalescing there has to be relative movement between particles .This comes only due to relative particle size distribution. This distribution is very narrow in the zone of high density of small particles. It is understood here that the multipass centrifuge 504 must begjn with fresh slop oil. Also, it is understood that the gap between slop oil generation and operation of centrifuge 504 should be as minimum as possible. Further, it is understood that the fourth centrifuge 504 uses the relative motion brought by high G till such time that mean free path between the hydrocarbon particles is increased beyond maximum capacity thereof.

The stream 506 håving low turbidity is fed to a high speed shear mixer 508 wherein a predefined amount of solvent is added via line 510 thereby forming a mixture 512 that is fed to a fifth centrifuge 514. Addition of solvent followed by high shear mixing, in a range of about 8000-10000 RPM, allows formation of the adequate size solvent particles, preferably in a range of about 0.5 to 0.8 micron size whose population density increases by a substantial amount. It is understood that for adequate disintegration of solvent there is an optimum mixing time that is about 1 min. Further increase in time may result in increase in particle size and fall in turbidity. The right particle size of solvent preferably removes almost similar size of ultra fine oil particles. Thereafter the coalescence speed increases which prove to be a rate controlling step in accordance with the present invention wherein effect of coalescence extends in the working range of the fifth centrifuge 514. Thereafter, the centrifuge 514 starts working due to high population density and continues till the population density falls down to an earlier level. This effectively allows the oil particles to completely go out. Moreover, addition of solvent facilitates coalescence that enhances the efficiency of the centrifuge 514 by håving enhanced sweeping effect wherein a limiting factor for centrifuge 514 about population density of ultra fine droplets is reached with solvent droplets instead of oil droplets.

Addition of solvent in the high speed shear mixer 508 enhances population density within the slop oil that makes the fifth centrifuge 514 to efficiently allow the solvent to facilitate coagulation thereby moving the hydrocarbon particles to move from bottom and separate with a swiping impact. Addition of solvent in large amount in the high speed shear mixer 508 allows replacement of hydrocarbon droplet with solvent droplet for replacing oil with solvent therein.

The fifth centrifuge 514 preferably forms two layers, namely a top layer 516 and a bottom layer 518. The top layer 516 is a solvent dominant hydrocarbon layer that preferably contains a top layer comprising solvent, hydrocarbons with or without bound water, limited free water, limited salts and limited solids. The bottom layer 518 is a water dominant hydrocarbon layer that preferably contains water, limited solvent, limited hydrocarbons, salts, solids with very high turbidity value.

The top layer 516 is subjected to a BTX study 520 to know water and ash content for deciding requirement of solvent, if needed. The top layer 516 is added to a third heating vessel 522 via line 524 if the top layer 516 contains hydrocarbons håving bound water contained therein. Alternatively, the top layer 516 is added to a fourth heating vessel 526 through line 528 if the top layer 516 contains hydrocarbons håving no bound water contained therein. The third heating vessel 522 may be a multi effect evaporator with thermal vapor recompression, foam breaker and entrainment suppressor in other alternative embodiments of the present invention. The third heating vessel 522 preferably operates at an atmospheric pressure and in a temperature range of about 70 °C- 150 °C in this one embodiment. A predefined amount of additional solvent may be added to the third heating vessel 522 based on the BTX study 520. A predefined amount of waste heat is applied to the third heating vessel for increasing the temperature of the third heating vessel 522 and forming two phases, namely a vapor phase 530 and a liquid phase 532. The liquid phase 532 preferably contains hydrocarbons, remaining solvent, limited solids and limited salts therein. The vapor phase 530 contains vapors håving a part of solvent, entire bound water and free water therein. The vapor phase 530 is fed to a condenser 536 through line 538. The condenser 536 removes heat from the vapor phase 530 followed by processing through a condensate/phase separator 540. The condensate/phase separator 540 preferably forms a first layer 542 and a second layer 544. The first layer 542 contains pure water that can be reused in the process or packed for sale. The second layer 544 contains solvent that is reused in the process by mixing with the solvent line 510. The liquid phase 532 is free from bound water which is subsequently added to the fourth heating vessel 526 through line 534. The fourth heating vessel 526 operates at an atmospheric pressure and in a temperature range of about 90°C to 105°C. A predefined amount of a solvent stream-G (refer FIG. 6) may be added to the fourth heating vessel 526 as illustrated. The heating vessel 526 produces a vapor phase 546 and a liquid phase 548. The vapor phase 546 contains entire remaining solvent and a part of free water. The liquid phase 548 contains hydrocarbons, remaining free water, limited solids, limited salts and alum. The vapor phase 546 is added to the condenser 536 via line 550. The liquid phase 548 is fed to a sixth centrifuge 552. The sixth centrifuge 552 is a hot centrifuge or hot settling tank in this one embodiment that operates at an atmospheric pressure and at a temperature equal to or less than 95 °C. The sixth centrifuge 552 preferably produces two layers, namely a top layer 554 and a bottom layer 556. The top layer 554 is a hydrocarbon product håving traces of water, salts and solids therein. The top layer 554 is stored or packed for sale. The bottom layer 556 contains water, limited salts, limited solids and alum. The bottom layer 556 is processed through a RO plant 558 to obtain a pure water stream 560 and a reject stream 562. The pure water stream 560 is mixed with the first layer 542. The reject stream 562 follows line-H in this one embodiment.

The bottom layer 518 is fed to a fifth heating vessel 564 that operates at an atmospheric pressure and in a temperature range of about 90°C to 105°C. The fifth heating vessel 564 is supplied with waste heat to achieve the desired temperature range. The fifth heating vessel 564 produces a vapor phase 566 and a liquid phase 568. The vapor phase 566 preferably contains vapors of solvent and part of water that is further processed through the condenser 536 as illustrated. The liquid phase 568 preferably contains remaining water, limited hydrocarbons, salts and solids. The liquid phase 568 has substantially low turbidity which follows line-E as illustrated.

As shown in FIG. 6, the liquid phase 568 following line-E is fed to a third settling tank 602 wherein a predefined amount of alum stream 604 is added. The alum stream 604 is preferably added to reduce the turbidity of the liquid phase 568 and bring it down below 2.0 NTU. The third settling tank 602 may be optionally provided with heat to facilitate alum treatment in hot condition. Addition of Alum under heated condition at a temperature in a range of about 80 °C to 90 °C for at least four hours may reduce the turbidity of the slop oil by at least 90%. Addition of the alum stream 604 is more effective under heating that allows wider distribution pattern of droplets that firstly allows the oil particles to attach with each other and form a gel. It is understood here that efficacy of addition of alum stream 604 is not limited by availability of ions as is a kinetics related problem. The settling tank 602 preferably forms two layers, namely a top layer 606 and a bottom layer 608. The top layer 606 is a water dominant alum layer that preferably contains water, alum, solids, salts and traces of hydrocarbons contained therein. The bottom layer 608 is preferably a gelatinous oil bearing layer containing hydrocarbons, alum, water, solids and salts therein. However, it is understood here that the scum may be collected either at top or both at the top and bottom depending upon the ppm level in other alternative embodiments of the present invention. The top layer 606 is sent to a filtration unit 610 that splits the top layer 606 into a filtrate stream 612 and a residual stream 614. The residual stream 614 preferably contains solids with traces of hydrocarbons, salts and alum. The residual stream 614 is mixed with the bottom layer 608 through line 616. The filtrate stream 612 preferably contains water, alum and salts. The filtrate stream 612 is sent to a RO plant 618 through line 617 for obtaining a pure water stream 620 if total dissolved solids (TDS, hereinafter) of the filtrate stream 612 is high else directly stored or packed for sale via stream622 if the TDS is low. It is understood here that addition of alum in third settling tank 602 improves rate of filtration in the filtration unit 610 thereby substantially reducing turbidity below 2 NTU. The bottom layer 608 is mixed with the third layer 420 (refer FIG. 4) following line-H and sent to a first hot dryer 624. The first hot dryer 624 preferably operates at an atmospheric pressure and a temperature of about 108 °C which boils out the water in form of a water vapor stream 626 thereby retaining a viscous liquid stream 628 containing hydrocarbons, alum, solids and salts. The viscous liquid stream 628 is fed to an agitator/ de-oiling unit 630. A predefined amount of solvent stream 631 is added to the agjtator/de-oiling unit 630 along with the bottom layer 428 (refer FIG. 4) following line-K and containing solids that are coated with hydrocarbons. The agitator/ de-oiling unit 630 produces free flowing liquid stream 632 that preferably contains solvent with hydrocarbons, alum, salts and de-oiled solids. The free flowing liquid stream 632 is sent to a seventh centrifuge 634 through line 633. It is understood however that the seventh centrifuge 634 may be phase separator in other alternative embodiments of the present invention. The seventh centrifuge 634 preferably produces three layers, namely a first layer 636, a second layer 638 and a third layer 640. The first layer 636 preferably contains solvent and hydrocarbons which is added to the heating vessel 526 (as shown in FIG. 5) through line-G. The second layer 638 is a water dominant alum layer that preferably contains water with alum and salts along with limited solvent. The second layer 638 is fed to a sixth heating vessel 642 which operates at an atmospheric pressure and in a temperature range of about 90°C to 105°C. The sixth heating vessel 642 produces two phases namely, a vapor phase 643 and a liquid phase 644. The liquid phase 644 preferably contains water, alum and salts contained therein. The liquid phase 644 is recycled to the RO plant 618 via recycle line 646. The vapor phase 643 preferably contains vapors of solvent and water. The vapor phase 643 is sent to a condenser 648 for removing heat followed by processing through a condensate/phase separator 650. The condensate/phase separator 650 preferably forms a first layer 652 and a second layer 654. The first layer 652 contains pure water that can be reused in the process or packed for sale. The second layer 654 contains solvent that can be reused in the process. The third layer 640 preferably contains cake of wet de-oiled solids with solvent, limited salts and limited alum. The third layer 640 is sent to a second hot drier 656 that operates at an atmospheric pressure and temperature of about 200°C. A predefined amount of waste heat is applied to the dryer 656 to achieve desired temperature. The second hot dryer 656 treats the third layer 640 thereby removing a vapor stream 658 thereby forming a residual stream 660. The vapor stream 658 preferably contains vapors of solvent and water contained therein. The residual stream 660 preferably contains dried de-oiled solids with traces of alum and salts. The vapor stream 658 is mixed with the vapor phase 643 and further treated through the condenser 648 as illustrated.

Referring now to FIGS. 4-6, in operation, the processes 400 and 500 advantageously convert pollutants into valuable product streams thereby mitigating problems of environmental pollution and damage to environment. In addition, the processes 400 and 500 facilitate best possible recovery of oil and valuable water wherein the water can be used as a drinking water for commercial use at a cost less than the cost of storage of sludge/ slop oil. The processes 400 and 500 facilitate use of chemicals for recovery of oils such that the chemicals used are totally recycled and reused in the process. Further, the process of the present invention runs at almost nil energy cost by making use of waste heat in overall process.

EXAMPLES

The following examples and comparative examples are provided to demonstrate particular embodiments of the present invention. It should be appreciated by those skill in the art that the methods disclosed in the examples and comparative examples that follow merely represent exemplary embodiments of the present invention. Those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments described and still obtain a like or similar result without departing from the spirit and scope of the present invention.

PREPARATION OF SLUDGES /EMULSIONS FOR SUBSEQUENT REMOVAL OF BOUND AND FREE WATER

A predefined amount of in-house Sludge was prepared with water using Viscous/Non-Viscous Hydrocarbons in order to understand sludges and also for subsequent removal of entire Bound Water from therein. Accordingly, weighed amounts of Water, Hydrocarbons and Sodium Lauryl Sulphate as emulsifier, if any, are mixed and then stirred at 10,000 rpm using a high shear Mixer, for 1 minute at a time and for 5 times, while ensuring that temperature of mixed material never exceeded 58°C. After every 1 minute of mixing the material was cooled to near ambient temperature. Subsequently, a representative sample was subjected to 10 minutes of continuous centrifuging at 21,893 relative centrifugal force (RCF), in a batch type centrifuge, to find out if any water separated. If yes, then it was considered as slop oil. The remaining material was considered as sludge with bound water. Different types of sludges were prepared as shown in the following table 1.2 and table 1.3.

It was understood that the sludge with bound water mean from wherein no free water visibly emerges out even on batch centrifuging it at RCF of 21,893 with residence time of 10 minutes at peak RCF. The sludges were made without using external emulsifier like Sodium Lauryl Sulphate (SLS) with viscous Furnace Oil but not with free flowing diesel. It was observed that, drag on account of viscosity was an important reason for hydrocarbons to tightly hold onto fine droplets of water. It was observed that for diesel, use of Sodium Lauryl Sulphate was necessary. Even then, as can be seen from Table # 3, only 5.96 wt.% of total water present could be bound to diesel and 82.64 wt.% of diesel could be bound to water, thereby forming 45.18 wt.% Sludge, when using 2.43 wt.% SLS. It was also observed that sludges could be prepared using SLS, both with Furnace Oil and Diesel. However, with same amount of water, the quantum of diesel sludge with bound water was nearly half of that one got with furnace oil. It was further observed that water holding ability of Furnace Oil in sludge was deteriorated sharply with the presence of SLS. This was because with the use of SLS, sludge became far less viscous. This also showed that binding between hydrocarbons and water on accounts of viscosity and the use of SLS did not add up. In other words, their contributions towards binding the two were not additive. Further, it was observed that with use of SLS, the quantum of sludge with bound water dropped down. This was because now only a quarter of water was present that participated in binding with furnace oil. However, it was observed that the strength of binding was a lot stranger than what would have been possible in the absence of SLS. It was observed from Table 1.2 that, in Sludge No. 5, SLS was added to the water prior to production of sludge. While in Sludge No. 6, SLS was added to a sludge that had already been prepared with 49.75 wt. % water. From this Table it was observed that the binding between water and hydrocarbon was slightly stranger when SLS was uniformly dissolved in water prior to production of the sludge. It was observed that there was an upper limit on how much bound water can be held onto by Furnace Oil on account of its viscosity wherein the furnace oil cannot be made to hold the entire water as bound water through vigorous mixing beyond about 1.5 times of its own weight of water as can be clearly seen in table-2. Further, it was observed that furnace oil can hold water as bound water only up to 67 to 82% of its own weight beyond a threshold value. Also, the quantum of sludge formed with bound water was found to be decreased sharply with increasing water content. It was observed that the remaining water stayed as free water with traces of hydrocarbons in it. That was called slop oil. Though was difficult to produce fresh Sludge with more than 60-62 wt. % bound water in it, using furnace oil, through mixing, but then one can always retain the Fumace Oil Sludge with more than 80 wt. % bound water in it, by removing a part of Furnace oil from an already prepared sludge, using a solvent with centrifuge, as can be seen later in Samples 2 to 4 in later Table 4.3. Finally, it was observed from the calorific values of sludges deteriorate in proportion with water content therein.

EXAMPLE-2

PRE-TREATMENT OF INCOMING SLUDGES/EMULSIONS WITH CENTRIFUGE

It was an aim to determine extent of bound water present in an incoming sludge thereby splitting it into sludge with bound water and slop oil through centrifuge. Also, it was an aim to establish that with a batch Centrifuge alone it is possible to recover value added, marketable hydrocarbons; remove a part of water present and also reduce the quantum of Sludge that would require further treatment. Accordingly, the Sludges prepared in house and also Lagoon Sludge procured from Oil and Natural Gas Corporation (ONGC) of India were treated in a Batch Type Centrifuge at RCF of 4,500 and 21,893 with varying residence time thereby separating and weighing the fractions thereafter followed by doing mass balance for the material centrifuged. Further, these fractions were evaluated for their moisture content by a BTX Process followed by ash content by heating in a muffle furnace and subsequently for calorific values using bomb calorimeter and turbidity of Free Water that came out, with Hach Turbidity Meter. The constituents in the prepared sludge and the conditions under which these Sludges were centrifuged are mentioned in accordance with below mentioned tables 2.1- 2.8.

It was observed that there was no impact on furnace oil sludges containing up to 61 wt. % water while centrifuging the sludges with residence time of 10 minutes at peak RCF value of 21,893, provided that the sludge was without emulsifier like SLS. The entire sludge was retrieved back expect what might stick to the walls of centrifuge bottles. This can be seen from Table 2.3, for the sludge with 50 wt. % water the calorific value was not rose. However, once wt. % water of the sludge exceeded certain threshold value, which lies between the values of 61 to 70, then even without SLS, if a Furnace Oil Sludge was centrifuged for 10 minutes at a peak RCF of 21,893 it was found to be divided into sludge with bound water and slop oil. It was observed that if the sludge was håving 70 wt.% water and nil SLS, then it was found to be divided such that 53 wt.% of the sludge was containing 44 wt.% water and the entire water was bound water. The remaining material was found to be the slop oil. Alternatively, it was observed that if furnace Oil containing 96 wt. % water and nil SLS, then on centrifuging it for 10 minutes at a peak RCF of 21,893 the sludge was found to be divided such that only 6 wt. % of it forming the sludge with 40 wt. % water, the entire water being bound water, and the remaining material mostly as slop oil. It was further observed that beyond 70 wt. % water, with increasing water content, there was less yield of sludge with bound water in it. However, it was observed that the quantum of bound water inside the sludge does not vary much. Moreover, it was observed that for the less yield of sludge more slop oil was obtained.

Further, it was observed that for furnace oil sludge with 96 wt. % water was håving a meagre calorific value of 320 kcal/kg. However, on centrifuging the sludge for 10 minutes at a peak RCF of 21,893 it yielded 6 wt. % sludge and that the sludge was håving 19 times more energy density in it at 6,130 kcal/kg. Here by centrifuging it separated heavier lumps of Sludge, where energy was relatively concentrated from the slop oil that has very less energy in it.

Further, it was observed that centrifuging of the furnace oil sludge for 10 minutes at RCF of 21,893 with emulsifier like SLS in the sludge far lesser quantity of sludge was generated with bound water as compared to similar sludge without SLS. However with SLS, the quality of sludge was far berter as it had a lot higher calorific value, on account of far less water content. Here again a centrifuge created a value by squeezing out water from within the sludge. This was possible only because of the presence of SLS, which partially reduced the ability of sludge to hold onto water on account of its viscosity. However, it was observed that SLS helped to make a centrifuge effective and without SLS the centrifuge was håving no impact on the sludge.

Also, it was observed that centrifuging with diesel sludge for 13 minutes at RCF of 21,893 adds value only when the sludge was håving emulsifier like SLS in it. This was possible only when the water was bound to the diesel. However, without SLS, water was found to be separated from the diesel without any sludge formation. But once SLS is present, the centrifuging was able to concentrate 87 wt. % diesel into the sludge with just 6.44 wt. % water thereby nearly doubling the energy density within the sludge in no time up to a value of 10,160 kcal/kg which was found to be 92% of energy density of pure diesel.

Also, it was observed that with diesel sludge håving SLS, the value added by centrifuging depends both on the residence time provided and the peak RCF value chosen. Here cumulative impact of centrifuging was found to be a helping factor. It was observed that with centrifuging of diesel sludge håving SLS for 1 minute at RCF of 3,502, the squeezing out of water was found to be less. Consequently the quantum of sludge generated was found to be increased from 45 wt. % to 66 wt. % while the increase in energy density falls from 84% to 29%. This can be seen from Table -2.6. It was observed that, without SLS, there was no binding between diesel and water. The centrifuge was found to be quickly separating the two thereby giving pure diesel at one end. However, with SLS present, the diesel delivered was not entirely water free. Hence to that extent, from the perspective of a centrifuge, SLS was found to aid in cases of furnace oil based sludges and hinder in case of diesel based sludges. Accordingly, with diesel sludge it was established that a batch type centrifuge can break emulsifier based bonds between water and diesel. Often centrifuges are not expected to remove bound water. However, the bond breaking was more pronounced with increased residence time at a higher RCF value.

It was observed that the best impact of pre-treatment of sludge with a centrifuge was seen with ONGC lagoon sludge which can be seen from Tables 2.7 and 2.8. Here, it was observed that one can enhance commercial value of sludge by extracting from it 41 wt.% of saleable, free flowing hydrocarbons with a calorific value of 10,633 kcal/kg, ash content of 0.88 wt.% and moisture content of 0.39 wt.%. Besides, it was also observed that one was able to reduce by weight of sludge requiring further treatment by little more than three times with commensurate benefits. Also, it was observed that with more residence time or higher RCF value one was able to squeeze out more water. It was also observed that pre-treatment of sludge helped in reducing salt and ash contents in hydrocarbons. Further, it was confirmed that only centrifuge cannot remove entire water from the sludge. It was observed that the centrifuge enhances acceleration due to gravity by enormously speeding up the naturally occurring separation of two different immiscible liquids due to their density difference. It was observed that the centrifuge was helping when mean free path between tiny droplets of a particular liquid is small followed by consolidating them into much larger droplets with reduced drag, which then helped them move even faster.

Further it was observed that varying acceleration between moving droplets leads to a lot larger number of collisions in a given time and hence faster consolidation followed by setting up a chain effect. Also, with enhanced residence time, droplets of two different liquids keep gathering kinetic energy while moving in opposite directions. Once the kinetic energy difference between them exceed a threshold value, then they were able to break the forces that might be binding these droplets together thereby affecting a permanent separation between them, which otherwise would have been difficult to achieve with on-line centrifuges capable of operating at similar RCF. Accordingly, separation between constituents on lagoon sludge from ONGC was ascertained. Further, it was observed that free water can be collected from ONGC Sludge, behind the impervious, viscous layer of hydrocarbons with bound water, inspite of the fact that lumps of viscous layer emerge before the free water emerges while centrifuging. Lastly, it was observed that constituents of lagoon sludge do not naturally separate out with time, even after decades wherein quantum of bonds broken depend on both the operative RCF of centrifuge and the residence time of sludge within the centrifuge.

EXAMPLE-3

EFFECT OF USING XYLENE AS SOLVENT ON SLUDGES WITH BOUND WATER

An impact on release of bound water from sludges with time was studied by reducing their viscosities through addition of varying amounts of low viscous solvents like Xylene, at ambient and elevated temperatures. Also, it was discovered how water could be held tightly by hydrocarbons. Accordingly, about 58 wt.% and 200 wt.% xylene was added to viscous Furnace Oil Sludges without SLS prepared in-house with 50 wt.% bound water therein. Alternatively, about 58 wt.% and 200 wt.% xylene was added to viscous furnace oil sludge with 20.47 wt.% bound water and 3.74 wt.% SLS, extracted from in-house Sludge with 47.5 wt.% water and 2.51 wt.% SLS, by centrifuging that for 10 minutes at 21,893 RCF. Further, about 58 wt.% and 200 wt.% xylene was added to viscous ONGC sludge with 42.21 wt.% bound water and 8.61 wt.% ash that was recovered from batch centrifuging of in-coming ONGC Lagoon Sludge for 10 minutes at 4,500 RCF. Subsequently, the mixture was stirred well and kept a part of that low viscous mixtures in the settling vessels for 6 and 72 hours at a stretch at ambient temperature of about 28 to 32°C while keeping a yet another set of samples for 6 hours in a water bath at 80-85°C. At the end of test period, fractions of material from top, middle and bottom of the settling vessels were removed and evaluated for water content using the BTX process. Subsequently, water present in various levels with the average water content of the entire mixture was measure. While top-most layer was often nearly water free, no free water or slop oil was found to be collected at the bottom-most layer. The bottom-most layer was composition wise similar to the middle layer and hence added the same in Table Nos. 3-2, 3-4, 3-6 and 3-9.

furnace oil based sludges with 50 wt.% water-

In earlier Example-1, it was observed that on addition of external emulsifiers like Sodium Lauryl Sulphate to furnace oil based sludges containing up to 61 wt.% water with respect to the total water therein, the amount of water held by Furnace Oil as bound water, dropped down from 100% to a much lower level. For sludges with 48-49 wt.% water in it, when SLS added was 2.4 to 2.5 wt.%, we found only 25-23 wt.% of total water present in Sludge, remained stuck to furnace oil as bound water. But that was measured only after subsequently centrifuging the sludge for 10 minutes at 21,893 RCF. However, in accordance with the present Example-3, the furnace oil sludge with 47.52 wt. % water and 2.51 wt. % SLS in it, centrifuging for 10 minutes at 21,893 RCF a viscous sludge was retrieved containing 20.47 wt.% bound water and 3.74 wt.% SLS therein. The obtained viscous sludge with 20.47 wt. % bound water alone was tåken for the treatment.

In earlier Example-2, it was observed that on batch centrifuging of incoming ONGC Lagoon Sludge for 10 minutes at 21,893 RCF or even at 4,500 RCF, the sludge got separated into 3 different layers and middle layer was a viscous sludge with 30 wt. % bound water therein. When RCF was just 4,500, the middle layer had 42.21wt. % total water in it, of which only 72 wt. % was bound water. However, in accordance with present Example-3, it was evaluated that the middle layer after centrifuging in-coming ONGC sludge for 10 minutes at 4,500 RCF produced 42.21 wt. % total water in it. In other words, addition of xylene as solvent to viscous sludges alone, where except for ONGC Sludge the entire water was bound so tightly to hydrocarbons that even on centrifuging for 10 minutes at 21,893 RCF there was no separation of water. Also it was observed that with ONGC Sludge, at this high RCF only 28 wt. % of water was separated.

Accordingly, it was observed that Xylene dramatically reduced viscosity of the resultant mixture especially when the quantity thereof was added twice that of the sludge. Further, the resultant mixture was heated at 80 °C -85°C to further reduce the viscosity thereof. Apart from reducing viscosity immediately, Xylene was believed to enhance the density difference between immiscible hydrocarbons and water. However, it was observed that no free water or slop oil could separate out even after waiting for 6 hours. Hence, it was confirmed that viscosity alone was not responsible for hydrocarbons to hold onto such large amounts of water.

As shown in Table 3.1, it was observed that the mixture held even up to 31.27 wt. % water on an average. It was observed that the dispersed water droplet size was so tiny that even with viscosity got immediately reduced and density difference slowly got enhanced. However the drag experienced by them remained too high to allow their rapid separation. In addition, it might be probably because of dispersed water droplet size being just so small that inspite of 10 minutes of stay within a centrifuge operating at such large RCF, still immiscible water could not separate from hydrocarbons even when it was present in quantity as high as 50 wt.%.

In order to evaluate the extent of impact of addition of Xylene to the sludge on downward percolation of bound water with time, the table Nos. 3.3, 3.5, 3.7 and 3.10 were read horizontally for the Top-Most, Middle & Bottom-Most layers. Accordingly, it was observed that addition of xylene beyond a certain threshold value is essential to get a large impact on furnace oil based sludges. It was observed that for varied the quantum of Xylene added for Furnace Oil based sludges, Xylene was effective only when it was present in the final mixture in the levels of 66 wt.% and the benefit of Xylene was muted when presence thereof was limited to 37 wt.%. It was observed that even the top-most layer was not anywhere near being water free with 37 wt. % Xylene present in the mixture.

Further, it was observed that there was no collection of free water or slop oil at the bottom but there was collection of nearly water free hydrocarbons at the top-most layer. In addition to the fact that a lot more water got collected in the bottom most layer indicated that water droplets were actually very slowly moving down with time. Very slow rate of downwards percolation of water could either be because of presence of emulsifiers or due to ultra small size of dispersed water droplets. Accordingly, it was identified that the density differential between water and hydrocarbons diminished and that in turn reduced the force of buoyancy in case for water bound to oil due to emulsifiers. Accordingly, it was confirmed that in case of emulsifier being present the concentration of water in the bottom most layer cannot exceed the average concentration of water present as much as what would be possible in case there was no emulsifier where other things remaining the same. Further, it was observed that using Xylene with additional heating one may get water free top-most layer in about 6 hours, even from sludges with high water content, if condensed water vapours are prevented from trickling back into that layer or if one prevents the condensation of regressing water vapors itself. But the time required for this will be much longer if emulsifiers are present in sludge. Also only a small fraction of water free hydrocarbons can thus be released from sludges.

Further, it was observed that the temperature had two impacts on the mixture. Firstly, apart from further reducing its viscosity, it enhanced the rate of evaporation of water from the top-most layer. Again, the latter had two implications. Firstly, it helped to reduce water in the top-most layer. Secondly, it enhanced the rate of condensation. Part of our settling vessel projected out above the water level in water bath. Hence, its top portion was relatively cooler, allowing rapid condensation. With that, droplets of condensed water rapidly trickled back into the top-most layer. That in turn explained why we had more water in the top-most layer as observed from Tables 3.5, 3.7 and 3.10.

Also, it was observed that egressing water vapors could be prevented by not allowing the top end of our settling vessel kept in water bath to cool down in addition to getting much drier top-most layer. That could also be achieved by preventing the condensed water from trickling back into the top-most layer by modifying the design of our settling vessel itself.

It was observed that with reduced Xylene and relatively higher viscosity in the mixture as seen in Table Nos. 3.5, 3.7 and 3.10 and not repeated in Table 3.3. It was observed that it might have an adverse impact on the rate of evaporation. It was seen that when xylene present in the mixture was limited to 37 wt. % then only 2.39 wt. % of the mixture evaporated by way of water vapour. However, when xylene present in mixture rose to 66.5 wt. % then about 4.63 wt.% of the mixture evaporated by way of water vapour. Accordingly, it was confirmed that with less evaporation there was less condensation and hence less harm was done through condensation. This can be ascertained by comparing Table Nos. 3.2 and 3.4. Besides, in Table 3.3, the top-most layer consisted of just 6.12 wt. % of total mixture as against 9.07 wt.% in Table 3.5 where more xylene was used. By considering a thinner layer there was lesser moisture in top-most layer in as can be seen in Table 3.3.

However, in presence of SLS very low evaporation rate was observed inspite of equally large reduction is viscosity. It was because when water was bound to hydrocarbons through emulsifier, the boiling point thereof under a given pressure went high and with that evaporation rate at a given temperature came down along with condensation rate.

Accordingly it was observed that when water is bound to hydrocarbons through emulsifier, entire water or hydrocarbons may or may not be bound. Hence the process of separation between them becomes slow and incomplete without being completely ceased. Hence when emulsifier is present, deviation from average water content in any layer was observed to be less than that without emulsifier. This too was borne out from Table Nos. 3.5 and 3.7.

An important observation with ONGC Sludge was that even after reducing its viscosity immensely by adding twice as much its own weight of xylene there was little impact on downwards percolation of bound water present therein under ambient conditions. As can be seen from Table 3.10, the average water content in bottom most layer even after waiting for 72 hours rose to 16 wt.% when overall water content of mixture itself was 14 wt.%. In contrast, for Furnace Oil Sludge when twice its weight of Xylene was added the average water content became 16.67 wt.%. But after 72 hours of waiting, water in bottommost layer rose to 69 wt.%, which is nearly 4 times as much. With ONGC Sludge additional heat however had an immense impact though not as much as that seen with Furnace Oil Sludge.

It was further observed that solvent, even when added in large amounts, it does not quickly and selectively solubilize entire hydrocarbons present in sludge and then disgorge out immiscible water due to density difference as commonly assumed. However, it was only found to weaken the forces that bind water and hydrocarbons together and to an extent additionally helped by slowly enhancing density difference between them by slowly dissolving hydrocarbons in very small quantities at a time. It certainly did not entirely or immediately eliminate the forces that bind water with hydrocarbons.

EXAMPLE- 4

COMBINED EFFECT OF CENTRIFUGE & SOLVENT ON SLUDGES WITH BOUND WATER

In order to understand the mechanism and also the impact on the release of bound water from hydrocarbons firstly by reducing viscosity of various sludges followed by adding solvents, such that the mixture contains 67 wt. % solvents, subsequently centrifuging it for 10 minutes at 4,500 RCF and at ambient temperature of about 28 to 32°C was studied. Specifically, solvents like Xylene and Toluene were added to viscous furnace oil sludge prepared in-house with 50 wt. % water. Alternatively, solvents like Xylene and Toluene were added to viscous furnace oil sludge with 20.47 wt.% bound water and 3.74 wt.% SLS, extracted from in-house Sludge with 47.5 wt.% water and 2.51 wt.% SLS, by centrifuging that for 10 minutes at 21,893 RCF. Alternatively, solvents like Xylene and Toluene were added to viscous ONGC sludge with 42.21 wt.% bound water recovered after batch centrifuging in-coming ONGC Lagoon Sludge for 10 minutes at 4,500 RCF such that the mixture contains 67 wt.% solvent and then after stirring immediately subject it to non-stop centrifuging at 4,500 RCF for 10 minutes. The process of centrifuging produced two or three distinct layers of liquids. The third layer was obtained only in case of ONGC Sludge containing clear water. The Top-most layer was invariably water free. It was containing bulk of solvent added and also large amounts of hydrocarbons released from sludge. The middle layer, in cases where three layers were obtained, was consisting of hydrocarbons and water. Subsequently, the middle layer was evaluated. On centrifuging it for 10 minutes at 21,893 RCF we got sludge with bound Water, albeit much smaller in quantity, a free flowing layer of solvent plus some dissolved hydrocarbons and slightly coloured slop oil. The sludge thus obtained was then evaluated for bound water using BTX and calorific value using Bomb Calorimeter.

It was observed that combining solvent with centrifuge does a lot more than mere addition of their individual effects. For example, Furnace Oil Sludge without external emulsifier and with 50 wt. % water could not remove any water or oil after centrifuging it for 10 minutes at 21,893 RCF. Subsequently, by adding similar quantum of same solvent we could get only 8 wt. % of the mixture, in the top most layer with 0.31 wt. % water, after waiting for 6 hours. However, even at reduced peak RCF of centrifuge to 4,500, i.e. by 4.9 times, thereby keeping the residence time at peak RCF the same it was possible to collect 80 wt.% of the mixture in top-most layer with nil water in it, in just time of 30 minutes. This was mostly because by combining the solvent and centrifuge enhanced the factors that contribute to increase force of buoyancy that naturally helps separating two immiscible liquids. However, on other hand combining the solvent and centrifuge by reducing viscosity drag was substantially reduced that inhibited such separation.

As can be clearly seen from Table Nos. 4.1 to 4.3, in case of furnace oil sludge with emulsifier like SLS, the size of topmost water-free layer shrinks sharply from 80 to 50 wt.%. This clearly established that even a combination of solvent and centrifuge is less effective when water is additionally bound to hydrocarbons through an emulsifier. With shrinking of the top most layer, middle layer expanded from 20 wt.% to 50 wt.% and while doing so the presence of sludge with bound water therein went up from 72 to 95 wt.%. Even more important act was that bound water in within higher fraction of sludge fallen from 85 wt.% to 9 wt.% thereby enhancing the calorific value of that sludge from 1,520 to 9124 kcal/kg.

With the presence of the emulsifier like SLS, the hydrocarbon component in Sludge went up slightly from 76 to 87 wt.% while its water content came down from 20 to 9 wt.% on account of the combined treatment with Solvent and Centrifuge. But when SLS was not present, with same treatment furnace oil component in the sludge fell down dramatically from 50 to 15 wt.% while water content therein went up from 50 to 85 wt.%. When SLS was present, the mass of sludge required further treatment actually increased by 41 wt. % as compared to reduction by 55 to 57 wt. % in the absence of SLS. This basically implied that with presence of SLS, the increase in hydrocarbon content in sludge was not so much on account of some water moving out from it, but because of a lot more solvent coming into it with very little amounts of furnace oil leaving the sludge. When SLS was present only 2 wt. % of furnace oil present in sludge left and moved into top most layer while 25 wt.% of xylene added moved into the sludge and then got very tightly bounded to water. Here the topmost layer was consi sting mostly of Xylene alone and hence it was only slightly coloured. On the contrary, in the absence of SLS, about 86 wt.% of furnace oil present in sludge moved out into the water-free topmost layer while nil xylene moved in. Hence it was only in the absence of SLS that combination of xylene and centrifuge was able to remove 87 wt. % of furnace oil from within the sludge. Accordingly, the combined effect of solvent with centrifuge was ascertained.

It was observed that with furnace oil sludge, use of Toluene as Solvent was found to be equally good as that of Xylene except for the fact that with Toluene the mass of sludge was found to be shrinked by about 4.6 wt. % more time and reduced its water content by about 3.3 wt.% more as compared to xylene thereby raising its calorific value from 1,520 to 1,860 kcal/kg. Also with Toluene the middle layer was found to contain less amount of solvent with dissolved hydrocarbon therein.

Toluene was observed to remove 85 wt% hydrocarbons present in sludge along with 34 wt. % of water as against Xylene removing 86 wt.% hydrocarbons along with 87 wt. % hydrocarbons and 26 wt.% water present in sludge. Toluene was found to extract water from the sludge in a relatively berter manner while Xylene seems to extract hydrocarbons a little berter manner in comparison to Toluene.

It was observed with ONGC sludge that the combined use of solvent and centrifuge can remove free water with turbidity values in the range of 20 NTU. In case of ONGC Sludge, Toluene was preferred over Xylene as it reduced mass of sludge with bound water by a factor of 2.89 against with that of 2.51 with Xylene. Similarly, the factors for furnace oil sludge without external emulsifier were respectively observed to be 2.48 and 2.30. Hence the combination of solvent cum centrifuge was found to work berter with ONGC sludge. In case of ONGC sludge, Toluene was found to reduce hydrocarbon content in sludge by 48 wt. % while Xylene reduces it by 46 wt. %. Similar figures for furnace oil sludge without external emulsifier are 85 wt. % and 87 wt. % respectively.

In case of ONGC Sludge, Toluene was found to reduce water content in sludge by 90 wt. % while Xylene was found to reduce the water content by 79 wt.%. Similarly, for furnace oil based sludge without external emulsifier, Toluene was found to reduce water content in sludge by 34 % and Xylene was found to reduce water content in the sludge by 26 wt. %.

Hence, it was confirmed that water content is far more easily extractable in case of ONGC sludge as compared to furnace oil based sludge without external emulsifier. This was also seen by free water collecting at the bottom. Toluene was found to be particularly far berter when removal of water from the sludge. Accordingly, use of Toluene was preferred for ONGC sludge.

Further, it was observed that removal of bound water from the sludge preferred rather than extraction of hydrocarbons from sludge because removal of bound water from the sludge was found to increase calorific value of sludge without loading too much of hydrocarbons in solvent. However, the solvent can be reused as such prior to separating hydrocarbons from solvent when solvent has fewer hydrocarbons therein.

In case of ONGC Sludge, it was possible to extract close to 50 wt. % hydrocarbons from the sludge containing bound water therein without loading solvent with hydrocarbons in topmost layer beyond 8.5 or 9.5 wt. % when using Toluene and Xylene respectively. This was because a lot of released hydrocarbons were not solubilised by solvent collected in topmost water-free layer.

EXAMPLE-5:

STUDY OF PURE AZEOTROPIC BOILING WITH WATER

A study was conducted in order to understand and evaluate pure azeotropic boiling of solvents like Benzene, Toluene and Xylene with water at an atmospheric pressure 933 mbar followed by comparison of results with similar values from the literature. A predefine weighed amounts of solvents and de-ionized water in certain proportions were tåken in Round Bottom (RB) Flask of Dean and Stark Apparatus followed by heating in a mantle furnace. A condenser håving chilled water at 6°C is attached to the RB flask where vapours of solvent and water are condensed. A stop cork at bottom the receiver was positioned which was periodically opened to periodically collect the condensate and weigh the immiscible constituents individually after separating them in the separating flask. The temperature of material at near bottom in the RB Flask was continuously recorded using a digital thermometer.

It was observed that minimum azeotropic boiling point with water ought to be a fixed point. Yet a small range for boiling point was observed. It was observed that inspite of lower atmospheric pressure at our place, on an average we get 6.05°C higher minimum azeotropic boiling point with Benzene; 9.55°C with Toluene and 5.7°C with Xylene than what was reported in the literature. Part of this could be because there was no stirrer inside the RB Flask.

In case of minimum azeotropic boiling weight ratio, higher values were observed than what was reported in the literature. It was observed that for Benzene, it was found to be higher by 3.3 times. For toluene, initially it was higher by 1.43 times. For Xylene, initially it was higher by 1.46 times. In case of benzene, quantity of solvent floating over water was very high and therefore entrainment was also expected to be the maximum.

It was observed that weight ratio of solvent emergjng with water vapor increased with time. This happened significantly only for Benzene and Toluene. Moreover, the weight ratio of solvent to water in residual material in RB Flask progressively became far lower than the minimum azeotropic boiling ratio itself for Benzene and Toluene. Presumably, it was found that if one boils these solvents with water, with less solvent to water ratio by weight than the minimum azeotropic boiling ratio, then a lot more solvent was found to be gone out per unit of water removed.

EXAMPLE- 6

STUDY OF ABOVE AZEOTROPIC BOILING IN PRESENCE OF FURNACE OIL, WITH AND WITHOUT BOUND AND FREE WATER

In order to berter understand behavior of solvents at boiling in presence of furnace oil and modification thereof in presence of bound water and free water thereafter, predefined weighed amounts of Toluene and Furnace Oil in certain proportions were tåken in the RB Flask in first instance. Subsequently, Benzene, Toluene and Xylene were tåken at a time with Furnace Oil based sludge containing bound water. Thereafter, each of the above solvents was tåken at a time with furnace oil with drinking water in a specific proportion in the RB Flask. This RB Flask was a part of Dean and Stark Apparatus that was heated in mantle furnace. A condenser with chilled water supply was attached to the RB flask with supply of chilled water at 6 °C wherein the vapours of solvent and water were condensed. A Stop Cork at bottom of the receiver was attached to periodically collect condensate and individually weigh the immiscible constituents after first separating them in a separating flask. The temperature of material at near bottom in the RB Flask was continuously recorded using a digital thermometer. It was observed that when Toluene and furnace Oil were tåken in proportion of 50: 50 by weight, they both being non-polar form a solution. It was observed that the boiling point of Toluene went up from 110.8 °C since the boiling point of Furnace Oil is in the region of 350 °C. It was observed that when boiling began, Toluene preferentially boiled out as its boiling point was lot lower than that of Furnace Oil. The boiling point continuously rose as Toluene kept getting depleted as can be clearly seen from Table 6.1.

As shown in Table 6.1, the boiling began at 110.93 °C at atmospheric pressure of 933 mbar. Boiling Point of pure Toluene is 110.80 °C at sea level. Boiling ended at 350.15 that being the initial boiling point of pure Furnace Oil. We actually collected back slightly more solvent than what we added. At the end some Furnace Oil too came out.

It was observed that when solvent was added to any sludge for boiling out the bound water from hydrocarbons, there was yet another phenomenon working apart from solvent helping to depress the boiling point of water and vice versa which was vast reduction in viscosity of furnace oil that helped in weakening of the forces that bind furnace oil to the bound water. It was observed that the boiling point of bound water reduced by reducing viscosity itself.

As can be seen in Table 6.2, instead of pure furnace oil in case of furnace oil based sludge with 50 wt. % bound water, it was observed that water was held onto furnace oil so tightly that even on centrifuging it for 10 minutes at 21,893 RCF, nil water was found to be separated from the furnace oil. Under such a circumstance, entire bound water got removed in temperature range of 91.2 °C to 108.86 °C through boiling along with 69 wt. % of Toluene that was origjnally present. Average weight ratio at which Toluene and Water came out was 6.93. As compared to a mixture of pure water and toluene, here the boiling point rose towards the end once ratio of Toluene to furnace oil dropped down below a certain point. It was because with Toluene being in solution with furnace oil, the latter raised the boiling point of former as seen in Table 6.1. Also wt. ratio of regressing solvent to water fell down from 9.34 to 6.93 (as shown in Table 5.2) as entrainment became less since here the solvent was in solution with furnace oil.

Similarly, with Xylene, entire bound water got removed with 35 wt. % Xylene. It was observed that even the rate of water removal was berter at 0.33 g/minute as compared to 0.30 g/minute for Toluene.

Further, the temperature range was observed to be higher. It was in a range of about 96.33 °C to 136.28°C. This was because boiling point of pure xylene was higher than that of toluene as can be seen from Table 5.1. Interestingly, it was observed that the end boiling point rose close to that of the boiling point of pure solvent. This was presumably because towards the end, with depletion of bound water, the lefl; over material in the RB flask became similar to the starting material as per Table 6.1. Here too the weight ratio of egressing solvent to water was found to be 1.92 which was lower than that 2.08 as indicated in Table 5.2.

It was observed that rise in temperature occurred towards the end when bound water was getting depleted. However, the use of multi-effect evaporator for boiling out water and solvent from hydrocarbons was preferred. The multi-effect evaporator allowed material to be in sections/vessels where ambient pressure and hence absolute temperature was low by the time boiling point rose. This successfully prevented thermal cracking.

It was observed that with benzene, entire bound water got removed with 93 wt. % of Benzene. Benzene was found to be weakest in removing bound water as per unit of bound water removed 82 units of benzene by weight were required. Benzene was found to be the slowest amongst the solvents however it was found to have an advantage that the entire process got over by 80°C.

Here the boiling point range was found to vary from 72.11 °C to 79.54 °C. It was observed that weight ratio of egressing benzene to water for boiling out pure water was 82.34 on an average, which was however more than 61.97 as seen in Table 5.2. This showed here that the water was indeed bound and not free. Therefore, a lot more benzene was required as håving weakest ability to remove free water.

When solvent boiled out bound water, towards the end the quantum of solvent required to drive out a unit mass of water rose very sharply along rising boiling point. Also, it was observed that quantum of required solvent went up partly because statistically it was then difficult for egressing solvent vapours to encounter residual water before emerging from furnace oil. It could also be partly because the last bit of water could be most tightly bound to furnace oil. Boiling point also rose towards the end as there was no further depression of boiling point of solvent present in solution with higher boiling furnace oil. The depression in the boiling point of the solvent was available earlier because of water being present was now no longer available.

A behavioral study of bound water in furnace oil based sludge after being replaced with free water can be seen from Table 6.3. Here drinking water was added in the RB Flask in specific proportions with pure furnace oil and solvent wherein water added was in excess. It was observed here that instead the entire solvent went out and that too with far lower boiling point range, leaving behind excess free water with furnace oil. Free water was not found to be mixed with furnace oil and that was removed by gravity based separation. It was observed that all three solvents were entirely boiled out within a temperature range of 97 °C to 99 °C except for benzene where boiling started from 86.7°C and went up to 98.31°C. Interestingly, it was observed that the free water drove out entire solvent from Furnace Oil and the final boiling point approached that of free water temperature and not that of solvent temperature. When free water drove out solvent, the weight ratio of egressing solvent to water was a lot lower than minimum azeotropic boiling ratio. This was totally reverse of what happened when solvent was driving out entire bound water. While entire or slightly excess solvent was removed only 30 wt.% of original free water lefl; while boiling out benzene, 42 wt.% free water lefl for boiling out toluene and 53 wt.% water left for boiling out Xylene. As can be seen from Table 6.3 that the weight ratio of egressing solvent to water was almost same i.e. 2.26 and 2.38 for Benzene and Toluene respectively. A fraction of water left when removing Toluene due to addition of less water for removing toluene. Xylene was found to be more effective in removing bound water and Toluene was found to be more effective in removing free water.

It was observed that the rate of solvent removal from the solution with higher boiling hydrocarbons like furnace oil was a lot faster with free water than the rate of bound water removal from same furnace oil in sludge with same solvents. For example, Xylene removed bound water from furnace oil at the rate of 0.33 g/min. However, free water removed Xylene from furnace oil at the rate of 1.76 g/min. This was because of slow heating when removing bound water from furnace oil using xylene. This happened because water was held to furnace oil in sludge a lot more tightly than the binding strength between Xylene and furnace oil on account of their solubility.

Further, it was observed that when only traces of solvent were present in Furnace Oil, a lot more water was required to remove a given mass of solvent towards the end. This was because with minuscule solvent left in furnace oil, the boiling point approached that of furnace oil or 350 °C although the solvent was being boiled out at less than 99 °C. Statistically it was found lot more difficult for egressing water vapour to encounter solvent present within a far larger volume of furnace oil when only traces of solvent were present.

Accordingly, it was confirmed that the boiling point of solvents like Benzene, Toluene and Xylene can be substantially depressed by adding free water to the solution of hydrocarbons when these solvents were present in the solution with other hydrocarbons håving substantially higher boiling points. It was also confirmed that one can choose to remove either the entire water or entire solvent by varying their initial ratio in the mixture in case where furnace oil was present.

EXAMPLE-7

REMOVAL OF BOUND WATER FROM FURNACE OIL SLUDGES WITH 50 WT.% BOUND WATER IN IT, BY BOILING IT WITH AZEOTROPIC SOLVENTS

In order to evaluate implications of using different quantity of various solvents on removal of bound water from Furnace Oil Sludges with 50 wt. % Bound Water in it, predefined proportions of sludge and solvent by weight were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time.

It was observed that in all above tables, entire water present in the sludge was bound water. It was observed that addition of 5.5 times the weight of water present in the sludge was must in case where Xylene was used as solvent. However, it might be reduced to 3.5- 4.5 times, without much rise in maximum temperature at the end of the experiment. It was observed that if Xylene was tåken up to 3 times the weight of water present then temperature at the end was not only high but also there was residual moisture in left over material. It was observed that addition of 10 times the weight of water present in sludge was must in case where Toluene was used as solvent. It was observed that moisture in residual Furnace Oil cum Solvent was low. It was observed that addition of 80 times the weight of water present in sludge was must in case where Benzene was used as a solvent. With this one can remove almost the entire bound water present in sludge.

As can be seen in Table 7-2, temperature rise was observed to be maximum when average weight ratio of Toluene to Water boiling out was approximately equal to original weight ratio that was present at the start of the process inspite of which entire water cannot be removed from sludge. This was because under such a condition neither water was able to boil out entire solvent nor the solvent was able to boil out entire water. However, then water may keep accumulating over time and may boil out entire solvent from the mixture if average weight ratio of solvent to water boiling out was more than what was originally present as in Test 1. On the contrary as seen in Test 3, it was seen that if average weight ratio of solvent to water boiling out was far lower than what was originally present, then solvent kept accumulating over time thereby ensuring that entire water got removed from sludge through boiling. For Xylene, the worst weight ratio to have for solvent to water was 1.85. This was because the average weight ratio of solvent to water boiling out was the same as what was present right in the begjnning.

It was observed that final temperature was very high when one began the process by håving the same weight ratio of solvent and water in mixture as one would find on an average in the vapour phase. It was also observed that it was very difficult to remove entire water or solvent from sludge under that condition. It was observed that at least 1 wt. % to 1.5 wt. % water stayed back along with similar amounts of solvent. Removal of this residual amount of water and solvent was difficult inspite of massive rise in temperature.

When Xylene was added either 1.65 or 1.85 times the weight of water present in furnace oil sludge with 50 wt. % water, at the end we found that our purpose was defeated. Instead of solvent removing entire bound water, the bound water actually ended up removing entire solvent through boiling. This was because the average egressing ratio of solvent to water by weight itself was 1.86 when xylene was 1.85 times the weight of water present. In the end it was observed that 0.54 wt. % Xylene was left behind with 1.09 wt.% water inspite of final temperature rising to 180.1 °C.

Similarly, it was observed that for Toluene and Benzene too there may be a cut off point for the amount of solvent added. If solvent added is less than that cut-off value then instead of solvent removing entire bound water one may find the bound water has boiled out the entire solvent instead. For Toluene, that amount was observed to be between 5-6 times the weight of water for furnace oil sludge with 50 wt.% water. For Benzene, that amount was about 80 times the weight of water in furnace oil sludge with 50 wt.% water.

It was observed that rate of water removal with Xylene was 0.33 g/min, with Toluene 0.30 g/min but with benzene it was only 0.02 g/min. Hence it was established that one may require a lot more benzene to take out a unit mass of water due to which the rate of water removal is so low. However, it was observed that only advantage with benzene was operative temperature range which was found 72 °C to 80 °C as against 96 °C to 138 °C for Xylene and 89 °C to 109 °C for Toluene. Here above rates of water removal with Xylene, Toluene and Benzene were found to be small er as compared to the rates of removal of free water with same solvents (refer Table 5.2). It was observed that, the quantity of Xylene egressing with unit weight of water was rising when initial ratio of solvent to water was in a range of about 1.65 to 4. Even for Toluene and Benzene, with more solvent added, more solvent found egressed per unit mass of water removed through boiling.

As can be seen from Test 3 in Table 7.1C that it was possible for average weight ratio of solvent to water boiling out to be lower than both the initial and final weight ratio in which they boil out. That was because the minimum ratio in which they boil out was not at the very start but somewhere soon after that. Also it can be seen from

Table 7.1C that a very steep rise in the weight ratio in which they boil out towards the end was observed when initial weight ratio of solvent to water was very high. Once that happened the end temperature still increased up, but then only up to the boiling point of pure solvent under ambient pressure and not well above it. Inspite of the weight ratio of egressing solvent to water increased up steeply towards the end. It was observed that average weight ratio was not differ much than their initial weight ratio. This was because such a sharp rise in their weight ratio and also in their boiling point was seen over a very short period of time towards the very end of the process.

On the contrary, as can be seen from Table 7. IA and 7. IB, the final temperature reached exceeded the boiling point of pure xylene under similar ambient pressure when weight of xylene added is the range of 1.85 to 3.0 times the weight of water present in sludge. Accordingly, it was concluded that lower the ratio higher will be the final temperature rise. This may be probably because when xylene was relatively less, it cannot adequately depress the boiling point of last bits of bound water in furnace oil. Hence, it was confirmed that first the quantity of solvent added at the start has to be such that at the end of the process, for a given heating rate enough residual solvent remains back in furnace oil to adequately reduces its viscosity and also to adequately depress the boiling point of last bits of bound water in furnace oil.

Further it was observed that one must remove entire bound water with large amounts of solvent still remaining behind in residual furnace oil in order to get low operative temperatures that probably might have helped in three ways. Firstly, furnace oil remained free flowing with very small viscosity till the end. Secondly, the boiling point was not significantly raised till the end by presence of soluble furnace oil with large fraction of residual solvent. Thirdly, it was easier for it to drive out traces of water towards the end with large presence of residual solvent.

It was observed that the left over weight ratio of solvent to oil was observed to be Minimum of 3.59, 3.09 and 2.98 for Xylene, Toluene and Benzene respectively for removing entire bound water from less viscous Oil. However, to get above mentioned left over ratios one has to take initial wt. ratio of solvent to water/oil are 5.5, 10.0 and 80.0 for Xylene, Toluene and Benzene respectively and follow optimally controlled rate of heating.

EXAMPLE- 8

ESTABLISHMENT OF THE BASIS OF EVALUATING QUANTITY OF ADDITION OF SOLVENT

In order to establish the basis of evaluating how much solvent one should add was based on amount of water present in Sludge or the amount of hydrocarbons present therein. Accordingly, predefined proportions of sludge and solvent by weight were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time. It was observed that the best results were obtained when residual solvent to furnace oil ratio, by weight, at the end of the experiment was high. In Test-3, where the above residual ratio was 5.07, least temperature rise was observed with maximum bound water removed with residual moisture level being just 85 ppm. It was established that it would not matter whether one considers the weight of water or weight of furnace oil in sludge for evaluating the quantity of solvent to be added.

As can be seen from Test Nos. 1 and 2, rate of water collection was observed to be significantly low when there was less water in Furnace Oil Sludges. This was inspite the fact that per unit mass of egressing solvent more water was removed at that time. Apparently, water in Furnace Oil based Sludge was limited to the extent to which it can depress the boiling point of solvent.

EXAMPLE- 9

EVALUATION OF EFFICACY OF PROCESS FOR REMOVAL OF BOUND WATER FROM DIFFERENT FURNACE OIL SLUDGES

It was an aim of the experiment to evaluate efficacy of our Process for removal of bound water from different Furnace Oil Sludges with varying water content with entire water present being only bound water. Accordingly, predefined proportions of sludge and solvent by weight were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time. Here bound water content in furnace oil sludges was varied from 2.15 % to 84.94 wt. %. It was observed that entire water in these sludges was bound water. It was understood that it was not possible to prepare sludge by mixing water with furnace oil, with more than 60 wt. % or 61 wt. % water in it with entire water being bound water. As explained earlier in Example- 1, if one tries to mix 85 wt. % water with 15 wt. % furnace oil it forms a mixture of sludge with bound water and slop oil. But still it was indirectly possible to get furnace oil sludge with 85 wt.% bound water in it. For that furnace oil sludge with 50 wt.% bound water was added with twice if its weight of solvent like xylene and then centrifuged for 10 minutes at 21,893 RCF. Most furnace oil in sludge was moved out with solvent leaving behind 14.5 wt.% of initial sludge cum solvent as a stable viscous sludge containing 15 wt.% furnace oil with 85 wt.% bound water in that. This sludge was tåken for Test 4 in Table 9. IB and then removed bound water from therein.

In the range of 2 wt. % to 85 wt. % bound water, entire bound water was removed from the sludges without temperature exceeding 140.12 °C using Xylene as Solvent. Throughout Xylene added was either 5.5 times the weight of furnace oil or water present in sludge, whichever allowed adding more solvent thereto. In case where final temperature rose to 140.12 °C, the least water was obtained at 159 ppm left behind in residual material at the end of the experiment.

It was also observed that the rate of water removal was distinctly low when water content in sludge is 15 wt. % or lower. Rate of bound water removal was inversely proportional to binding strength of water to furnace oil. This strength was higher when total water content was lower.

Further, it was found that the maximum rate of water removal was 0.33 g/min. Yet this maximum rate of water collection was 4.15 times lower than 1.37 g/min, which was the rate of free water collection with Xylene (as shown in Table 5.2). Accordingly, it was proved that the water removed here was bound water and not free water.

It was also found that boiling point itself starts from 121°C when water present in furnace oil sludge was only 2.15 wt. % whereas for all other cases is starts from 95 °C or 96°C. Also, on an average 14.79 times of xylene egresses out when water present was 2.15 wt.% per unit mass of water removed. This high value might possibly be due to enormous quantity of Xylene being present. Normally, this weight ratio was observed to be varying from 3.3 to 1.92.

It was observed that more than 100 wt.% water got collected when water present in furnace oil sludge is 2.15 wt.%. This may have happened because error in BTX result was high especially with low moisture. Also, even otherwise BTX indicated a slightly lower value for water present than what was actually present.

EXAMPLE-10

REMOVAL OF BOUND WATER FROM FURNACE OIL SLUDGES HÅVING 50 WT. % BOUND WATER IN IT, BY VARYING THE RATE OF HEATING, AFTER ADDING VARYING PROPORTIONS OF SOLVENTS

It was an aim of the experiment to evaluate the impact of varying rate of heating, with different proportions of solvent added, on removal of entire bound water from furnace oil sludges with 50 wt.% water in it. Accordingly, predefined proportions of sludge and solvent by weight were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time. However, except for the above mentioned facts, the rate of heating was varied with the input voltage to mantle heater. This variation in heating rate meant that in most cases 25 ml of condensates in approximately 30, 20 or 10 minutes was collected. Xylene was added to fumace oil sludges with 50 wt.% Bound Water, in 4 weight rati os, i.e. 1.85, 2.50, 3.50 and 5.50 with respect to water present in Sludge. And then for each ratio the heating rate was varied. It was observed that impact of varying heating rate was marginal except for weight ratios 1.85, 3.50 and 5.50. It was observed that medium rate of heating was necessary for weight ratio of 1.85 where water removal rate was 0.48 g/min or condensate removal rate was 1.35 g/min. It was observed that best results in terms of low residual moisture were obtained in left over material with least rise in temperature. This was found to be a very sensitive ratio since residual solvent staying back in left over furnace oil was extremely small and hence slight variation therein mattered a lot for removal of last bit of bound water with minimal temperature rise. At this rate of heating a little more water got boiled out as compared to solvent, thereby allowing little more solvent to accumulate and subsequently residual water rapidly boiled out at that elevated temperature.

Accordingly, it was established that for any amount of solvent added one must always try to leave behind maximum amount of solvent in residual furnace oil by allowing on an average least amount of solvent to boil out per unit mass of water removed through boiling if one wants to remove entire water from sludge at least temperature. However, slight increase in mass of residual solvent staying behind till the end might have played a huge role in ensuring complete removal of water from sludges at minimal temperature. It was observed that slowest rate of heating was suitable for weight ratios of 3.50 and 5.5 although for 3.50 there was not much difference between the medium and slow rates. However, for 5.5 the issue was clear. For ratio of 3.50, medium rate of heating was not found to be feasible inspite of more solvent being left behind as more water was also left behind. Here the extra water left behind was significant to remove one has to increase the temperature substantially and also consume large amounts of residual solvent.

However, it was observed that Xylene failed to boil out entire water when weight of Xylene added was 1.65 times the weight of water in sludge. Instead, water present in sludge boiled out entire Xylene. This happened because average weight ratio in which solvent and water boil out was 1.79 (as can be seen from Test-1 in Table 7.1) which was a lot higher than initial weight ratio in which they were present prior to boiling. Here, it was established that the rate of heating might have to be fast instead. Referring to Table Nos. 7. IA and 7.1C it was seen that when Xylene added was 1.65 times the weight of water, water was boiled out at an average rate of 0.52 g/min as against a value of 0.33 g/min when weight xylene added was 5.5 times the weight of water present. Accordingly, it was established that the heating rate must be slow when entire water has to be boiled out with preferred weight ratio of Xylene and the heating rate must be fast when solvent has to be driven out.

EXAMPLE-11

IMPACT OF SEVERLY CONTROLLED RATE OF HEATING ON REMOVAL OF BOUND WATER FROM FURNACE OIL SLUDGES USING SOLVENTS

A role of additional and severe controlled heating rate on removal of last fractions of bound water present in sludges was studied. Accordingly, predefined proportions of sludge and solvent by weight were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6°C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time. This was except of the fact that towards the end of the process, when about 6 wt.% of water was left in sludge the rate of heating was substantially reduced, even periodically allowing the temperature of mixture to fall by 3 °C to 10 °C. The idea was to hold the mixture within a fixed temperature range for much longer time, by firstly reducing and then by increasing temperature of residual material within that range in small steps. Also this meant entirely stopping and re-starting the boiling process a large number of times. This allowed final traces of water to emerge from sludge with lots of solvent in sharp and short bursts. However, care was exerted to ensure that condensates did not overflow from condenser top. As can be seen from Table 11-A, average rate of condensate collection was only 1.20 g/min as against a value of 1.83 g/min for successful experiment. Consequently higher amounts of xylene did not boil out, per unit mass of water removed through boiling. Hence as can be seen from Table 11-B that the left over weight ratio of solvent to water was slightly higher for failed experiment till 5th collection and at the top of that we did not severely slow down the heating rate towards the end of the process as explained above in procedure. Consequently, as can be seen from Table 11-B that due to high rate of heating we ended up boiling out solvent and water almost in equal ratio from 6th till 19th collection.

It was observed that at least egressing solvent was slightly more than the water up to 10th collection and therefore the residual weight ratio of solvent to water at least kept falling slightly. But from 1 lth till 17th collection they almost boiled out in equal proportion. Water cannot stay back with temperature of mixture approaching 232 °C. More amount of heat was fed at a rate faster than what could be consumed through boiling. However, more solvent got removed through boiling than water because of substantially slowed down rate of heating towards the end due to which enough latent heat was not supplied for boiling out water.

In case where weight of Xylene added was 2.28 times the weight of water present. Under this situation, weight ratio in which xylene and water boil out was 2.07 when heated slowly such that the rate of condensate collection was only 0.50 g/min. This allowed xylene to accumulate instead by preferentially removing water from sludge through boiling. Here, firstly the overall rate of heating of the failed sample was high with condensate collection rate being 2.30 g/min due to which it started with boiling out little more solvent per unit mass of water removed as compared to slower rate of heating. Fortunately not much harm was done till 3rd collection. In 4th and 5th collection more solvent left with fast heating. Additionally, towards the end the rate of heating was not slowed down for the failed sample. It was observed that the temperature of residual furnace oil kept rising as the rate of heat supply far exceeded the requirement. With that then firstly water started going out rapidly since had the ability to soak up heat on account of its high latent heat. Therefore, from 7th collection onwards, residual weight ratio of solvent to water that remained behind kept rising and it rose up dramatically after 9th collection. After most water left then with high temperature rate of solvent boiling went up so dramatically, at the cost of water removal. Consequently, after 10th collection inspite of the fact that some water was still left behind, there was hardly any solvent present to remove it. As can be seen in Table 11-A that at the end weight ratio of residual solvent to furnace oil fell down to 0.02. Taking out residual water from furnace oil was desirable for this ratio of initial xylene added by depressing its boiling point with the help from large amounts of residual solvent. This was how inspite of håving exceeded 300°C the entire water from furnace oil was removed.

Accordingly, it was ascertained that by opting for slow rate of heating allowed less solvent to go out by end of 6th collection and consequently a higher weight ratio of solvent to water was left behind in the RB Flask. Subsequently, heat closer to the required rate to boil out small amounts of water and solvent from furnace oil was supplied by drastically slowing the heating rate. From begjnning of 7th till the end of 1 lth collection water boiled out only in slight preference to solvent and not huge preference as earlier. Consequently, in the end lot of solvent remained behind in the RB Flask to drive out the last bit of water without furnace oil temperature rising only up to 163°C and not 307°C.

Finally, it was observed that with fast heating rate water preferentially boiled over solvent by a relatively large margin as it required a lot more latent heat for phase transformation. Also, it was observed that with ultra slow heating rate once again water preferentially boiled over solvent provided that the residual weight ratio of left over solvent to water was high but by a relatively narrow margin as reason being that the rate of heat supply was not the driving factor. Lastly, it was observed that the water preferentially boiled out with very low rate of heating if solvent was present in higher quantity than water.

EXAMPLE -12

REMOVAL OF BOUND WATER FROM DIESEL SLUDGES CONTAINING EMULSIFIER BY BOILING IT WITH AZEOTROPIC SOLVENTS

It was an aim of the experiment to evaluate the process of boiling out bound and unbound water with azeotropic solvents from diesel sludges containing emulsifier(s). Accordingly, predefined weight proportions of sludge containing emulsifier and azeotropic solvent mixture were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time.

It was observed that only a tiny fraction of bound water was present in the diesel sludge when an emulsifier like sodium lauryl sulphate was added thereto. In other words, only about 6 wt.% of total water present got so tightly bound to diesel that even on centrifuging it for 10 minutes at 21,893 RCF none of that water was separated from diesel. The rate of water removal was about 2.2 times faster when using Xylene and about 1.6 times faster when using Toluene in comparison to furnace oil sludge wherein the bound water was present in an amount of 49.81 wt. %, as clearly seen in 7.1C and 7.2. This was because only a small fraction of water present was bound water.

It was observed that water collection rate was however significantly lower than that observed in Table 5.2 where Xylene and Toluene removed the free water respectively at the rate of 1.37 g/min and 0.67 g/min. It was observed here that Xylene ended up removing entire water from sludge, i.e. both bound and free water, as the weight of Xylene added was 5.51 times the weight of total water present.

It was observed that Toluene and Xylene both remove the bound and unbound water present in sludge inspite of the fact that most of the water present was unbound water, still the final temperature shot up to 110.61 °C and 139.24 °C respectively. This was because boiling points of these solvents cannot be depressed any further once entire water was removed. Once entire water was removed what was left was a solution of solvents and diesel, where diesel was håving a slightly higher boiling point. It was observed that at that stage solvents began to boil out at their respective boiling points under given ambient pressure with further application of heat. Inspite of the fact that final weight ratio of solvent to water collected was very high, the average ratio was still very small and only slightly higher than the initial weight ratio implies that there was a brief and sharp rise in weight ratio of solvent to water only towards the end of the process.

EXAMPLE-13

REMOVAL OF BOUND WATER FROM ONGC SLUDGES, WITH 42 WT. % BOUND WATER THEREIN, BY BOILING WITH AZEOTROPIC SOLVENTS

It was an aim to evaluate implications of using different quantities of various Solvents on removal of bound water from ONGC Viscous Sludges with 42.21 wt. % bound water in it. Accordingly, predefined weight proportions of ONGC sludge and azeotropic solvent mixture were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time.

ONGC Sludges with Bound Water-

It was observed that when Toluene and Xylene were respectively added in weight ratio of 10 and 5.5 with respect to either the weight of water or hydrocarbons present in sludge thereby facilitating addition of maximum quantity of solvent. It was observed that slow rate of heating was preferred for both Toluene and Xylene that left behind more solvent over hydrocarbons in the end. It was established that it was possible to remove almost entire bound water present in viscous ONGC sludge without allowing the temperature to rise above boiling points of these pure solvents by adding optimal quantum of solvent and with slow rate of heating and under atmospheric pressure.

EXAMPLE-14

REMOVAL OF BOUND WATER FROM DIFFERENT SLUDGES BY COMBINED USE OF AZEOTROPIC SOLVENTS

It was an aim to evaluate implications of combining the use of Xylene and Toluene on removal of Bound Water from ONGC and Furnace Oil sludges with respectively 42.21 wt.% and 49.81 wt.% bound water therein. Accordingly, predefined weight proportions of sludge and azeotropic solvent mixture were tåken in the RB flask of Dean and Stark Apparatus and followed by continuous heating thereof in the mantle heater while continuously monitoring the temperature of material in RB Flask with digital thermometer. The vapours of bound water and solvent were collected in the receiver after condensing them with circulating cold water at 5 °C to 6 °C in the insulated condenser. The condensates were out and collected in separating flask using the stop cork at the bottom of the receiver. After phase separation, water and solvent collected were individually weighed each time.

These tests established that entire bound water can be removed from both ONGC as well as furnace oil sludges with combined use of Xylene and Toluene as azeotropic solvents. Also, it was observed that the observed maximum boiling temperature was almost mid way between maximum boiling temperatures when using these solvents individually for the ONGC and furnace oil sludges.

EXAMPLE-15

COMPLETE REMOVAL OF SOLVENTS FROM HYDROCARBONS BY HEATING WITH FREE WATER

It was an aim of the experiment to establish and evaluate the process of boiling out entire solvents like Xylene, Toluene and Benzene from furnace oil at below 100 °C under atmospheric pressure of 933 mbar by adding free water therein. Accordingly, weighed amounts of furnace oil, solvent and water were added in specific proportions in the RB Flask of Dean and Stark Apparatus followed by heating them in a mantle heater while periodically noting down the temperature of material in the RB Flask with digital thermometer. It was ensured that initial weight ratio of solvent to furnace oil was more than what was left behind in the RB Flask after removing entire bound water from furnace oil sludges. The vapors of water and solvent that boiled out were condensed in an insulated condenser where water was circulated at 5 °C to 6 °C. The condensates were collected in a receiver thereby using a stop cork at bottom of the receiver to periodically drain out condensate in separating flask while noting the time elapsed. After immediate phase separation the solvent and water collected were individually weighed. At the end material left in RB Flask was weighed and mass balance thereof was performed.

It was observed that the solvent cannot be entirely boiled out from the furnace oil in absence of free water without the boiling point of solvent eventually rising up to 350 °C which was the initial boiling point for pure furnace oil. It was observed that in case where initial weight ratio of solvent to furnace oil as 1 or more, the solvent might invariably begin to boil at boiling point of pure solvent under similar pressure. But eventually with last bits of solvents boiling out, its boiling point may approach that of pure furnace oil, that being 350°C under atmospheric pressure of 933 mbar. For Toluene, this was clearly seen in Table 6.1. However, it was seen that entire solvent can be boiled out from same furnace oil at less than 100 °C under a pressure of 933 mbar when free water was present in appropriate quantity. For Toluene, the boiling temperature range in present case was observed to be 95.90 to 97.60 °C as seen from Table 15.2A. However, said range was 110.93 to 350.15 without presence of free water as can be seen from Table 6.1.

Further, it was observed that by adding Xylene 5.5 times the weight of water was present in the sludge when removing almost entire bound water from the furnace oil sludge with 50 wt. % bound water therein. It was seen that at the end of the process weight ratio of Xylene to furnace oil that was left behind was 3.59. Therefore, Xylene was added 6 times the weight of furnace oil and water added was 3 times the weight of furnace oil present. It was found that the boiling temperature was in a range of 96.24 to 97.90°C in case where Xylene was added 6 times the weight of furnace oil and when water added was 1 times the initial weight of Xylene. It was found that the boiling temperature was in a range of 96.89 °C to 97.58 °C in case where Xylene was added 3 times the weight of furnace oil and water added was 2.00 times the initial weight of Xylene. Accordingly, it was ascertained that with less proportion of solvent present more free water was needed to retain boiling point range of solvent below 100 °C.

Further, as seen earlier at the end of bound water removal from above furnace oil sludge, the weight ratio of Toluene to furnace oil left behind was 3.09 as per table 7.2 and the weight ratio of benzene to furnace oil left behind was 2.98 as per table 7.3. Hence, the process was started by adding toluene 4 times the weight of furnace oil present and then 3 times the weight of furnace oil present. A preferred initial weight ratio of free water to solvent was 1 in both cases. With preferred amount of free water, boiling point range for Toluene was 97.28 °C to 98.50°C and 96.40 °C to 98.30°C respectively.

For benzene, the weight ratio Benzene was 3 times the weight of furnace oil present and then 2 times the weight of furnace oil present. It was seen that for 3 times benzene, preferred initial weight ratio of free water to solvent was 2. However with 2 times benzene, preferred initial weight ratio of free water to solvent was 1.50 times instead. It was seen that for both these preferred quantum of free water, the boiling temperature range was 80.12 - 98.59°C and 86.70 - 98.31°C respectively.

Accordingly, it was ascertained that apparently there was no limitation on how much solvent could initially be present in furnace oil or type of solvent that could be present. However, entire solvent, whether benzene, toluene or xylene, could be removed through boiling at temperatures below 100°C by adding appropriate quantity of free water prior to heating. In fact, more the initial solvent present often less was the weight ratio of free water to solvent to be added. Further, it was seen that increasing the quantum of free water beyond a certain limit, not only the boiling point range for solvent fell down but also the quantity of solvent removed by unit mass of water boiling out also fell down.

In all cases more than 100 wt.% solvent was collected inspite of not considering some solvent that would have evaporated. That was because towards the end boiling was terminated after collecting some furnace oil too. Yet, it was seen that the final boiling point for solvent always remained below 100°C under 933 mbar. Along with solvent some furnace oil was also collected only to ensure 100% removal of solvent. Therefore, furnace oil got slightly depleted. But once this solvent was re-used there could be no further depletion of furnace oil.

It was seen that average weight ratio of solvent to free water collected was almost always less than average weight ratio of solvent to bound water collected. The average collection temperature was also observed to be less with preferred initial weight ratio of free water to solvent.

As seen in Table 15.4, when mixed solvents like xylene and toluene were present in furnace oil for instance in 50:50 ratio by weight, even they can be entirely removed through boiling, at temperatures below 100°C by ensuring that the weight of free water added was 1.50 times the combined weight of initial solvents present.

However, as indicated in Table 15.4, when using mixed solvents to boil out entire bound water from sludges, the weight ratio of solvent to furnace oil left behind at the end of the process was higher. Apparently there was no upper limit on how much solvent can be present in furnace oil, as long as appropriate amount of free water was added prior to boiling.

As can be seen in Table nos. 15.5 and 15.6 that entire solvent present can be boiled out below the predefined temperature in case of hydrocarbons such as free flowing Diesel or highly viscous dewatered ONGC hydrocarbons and the like. In case where hydrocarbons have salt and/or ash or solids therein, then free water may perform an additional function of de-salting and de-ashing apart from boiling out entire pure solvent for re-use or sale at temperatures below 100°C.

EXAMPLE -16

SEPARATION OF FREE WATER AND FURNACE OIL

It was an aim to establish that free water can be separated from even viscous hydrocarbons with time through gravity based settling or centrifuge. Accordingly, weighed amounts of viscous furnace oil and free water were tåken in the RB flask and vigorously boiled for 15 minutes. Thereafter, in hot condition the contents were transferred in a pre-heated and insulated separating flask. It was seen that bulk of free water separated from immiscible furnace oil due to density difference and gravity. Accumulated free water was removed after about 30 minutes from bottom of separating flask. The remaining material within the separating flask, after removing its insulation, inside hot air oven for 48 hours while maintaining its temperature at 90 °C. Periodically, the collected water was removed from bottom of separating flask. After 48 hours, the remaining material was tåken out, homogenized and then tested for residual moisture using the BTX process. Subsequently, the boiling was repeated and the hot material was transferred into un-insulated separating flask. The material was removed soon after removal of bulk of free water therefrom. The remaining furnace oil with 17.33 wt.% moisture was then tåken out. Part of it was again heated and rest was allowed to cool to a room temperature. Both these hot and cold fractions were centrifuged for 5 minutes at 4,500 RCF. After centrifuge, 150 g of furnace oil was removed from top and tested for moisture through BTX Process. It was observed that, it was difficult to remove entire free water from the furnace oil being relatively viscous. It has to be heated to about 99°C to reduce its viscosity and then transferred hot with least fall in temperature, into a pre-heated and well insulated separating flask. On retaining there for about 30 minutes with less than 6 °C fall in temperature, about 94 wt. % to 95 wt. % of water drained out and collected at the bottom of the separating flask. Further, the entire remaining material was heated at about 85-90 °C to obtain remaining 5 wt.% to 6 wt.% water in next 48 hours. Finally it was observed that less than 3,500 ppm residual water was left in Furnace oil after periodical removal of free water collected from bottom of the separating flask. Accordingly, the parameters like the settling time required, maximum temperature needed for heating and residual water content in viscous hydrocarbon were established. It was seen that about 83 wt. % water was removed by gravity settling under hot condition followed by centrifuging it for 5 minutes at 4,500 RCF. But still residual moisture in Furnace Oil fell down from 17.3 wt. % to 11.8 wt. %. However, hot centrifuge with inlet temperature of 90 °C however worked wherein residual moisture in Furnace Oil was reduced from 16.48 wt.% to 2,900 ppm after centrifuging for 5 minutes at 4,500 RCF. It was evident that the recovered water was perfect for industrial use with turbidity values of 6 NTU to 7 NTU which was almost oil free that could be further processed for production of drinking water.

EXAMPLE -17

RECOVERY OF PURE HYDROCARBONS, BOUND WATER, SOLVENT AND THEN FREE WATER FROM PETROLEUM SLUDGES

It was an aim to quantitatively and qualitatively retrieve back pure hydrocarbons and entire water, inclusive of entire bound water, present in various sludges and also retrieve back the entire solvent and free water in accordance with process of the present invention.

Accordingly, weight fraction of bound and unbound water present in sludges were firstly determined and then calculated amount of solvent was added therein followed by heating in a Dean and Stark Apparatus using Mantle Heater. Accordingly, entire bound and free water present in sludge was removed with combined effect of solvent cum heat. Subsequently, entire water was condensed and collected along with part of solvent used. Further, a calculated amount of free water was added to residual matter in RB Flask and once again heated using the same apparatus. Subsequently, entire remaining solvent was removed and collected along with some free water. Thereafter, the entire amount of remaining free water from residual hydrocarbons was collected through gravity separation after heating the hydrocarbons and retaining them in a hot condition for a predefined time period in case where hydrocarbons were found viscous. Finally, both the waters and hydrocarbons were evaluated for their quality/purity and in addition the quantities retrieved were evaluated by doing a mass balance study.

Furnace Oil Sludges-

Referring to tables 17.1- 17.13, the total furnace oil that was present in sludges retrieved was about 99 wt. %. This was inspite of the fact that a tiny fraction thereof got removed along with solvent collected. It was seen that the furnace oil retrieved was håving about 3,806 ppm of residual moisture on an average as against original water content of 2,100 ppm therein. Inspite of slightly higher water content the recovered furnace oil was observed to have a calorific value of 10, 176 kcal/kg on an average as against the value of 10,172 kcal/kg for original furnace oil.

Further, it was observed that about 98 wt. % of the hydrocarbons present in Sludges were retrieved for ONGC hydrocarbons with 3,000 ppm of residual water on an average thereby håving a calorific value which was observed to be 10,635 kcal/kg on an average. Further, it was observed that about 96 wt. % diesel was retrieved on an average from Diesel sludges with average moisture level of 47 ppm and with an average calorific value of 11,021 kcal/kg as against to that of original diesel håving calorific value 11,002 kcal/kg.

Further, it was observed that more than 99 wt. % bound water was retrieved from furnace oil sludges with an excellent quality as can be clearly seen in table 17-5. The bound water recovered from ONGC sludge recovery was observed to be 99.5 wt. %. The bound water recovered from diesel sludges was observed to be 100 wt. %. Further, it was observed that more than 99 wt. % solvent was retrieved from furnace oil sludges. The solvent recovery for ONCG sludges was observed to be 99 wt. %. The solvent recovery for Diesel Sludges was found to be 98.9 wt. %.

Further, it was observed that free water retrieved from furnace oil sludges was about 96.5 wt.% on an average. The free water recovery for ONGC sludges was 97.3 wt. %. The free water recovery for diesel based sludges was found to be 98.6 wt. %. The free water obtained was in large in quantity and was under process for more than 48 hours with multiple steps.

EXAMPLE-18

PREPARATION OF OIL COATED SAND AND DEOILING OF SAND USING XYLENE FOLLOWED BY RECOVERY OF PURE SAND, OIL AND XYLENE

In order to study removal of hydrocarbons from solids Furnace Oil and ONGC free flowing Oil coated sand samples were prepared. These sand samples were treated using solvent like Xylene and thereafter quantitatively and qualitatively the recovery of sand, oils, Xylene and water was evaluated. Firstly, weighed amounts of oils into weighed sand which was water washed, completely dried and very clean. After mixing oils into sand, the oil coated sand samples were washed in separate batches of Xylene. Progressively, oil was moved from sand into Xylene. The washing was stopped once turbidity value and colour of pure Xylene did not change much from its original state after last washing cycle of the sand. At this stage, sand was believed to be coated with Xylene while entire oil on the sand was believed to be moved into spent Xylene. The Xylene coated sand was slowly heated beyond the boiling point of Xylene in Buchi Rotary Evaporator. The vapors of Xylene were condensed and collected. Subsequently, Xylene oil mixture was heated with free water to boil out entire Xylene with some free water in Dean and Stark apparatus thereby leaving behind oil with a fraction of free water. Subsequently, free water was removed through gravity separation while keeping entire material at 85 °C-90 °C for 48 hours. Finally recovered sand, oil and free water were evaluated for quality followed by doing mass balance thereof. Referring to tables 18.1- 18.4, it was observed that recovery of sand was about 100 wt. %. Further, it was seen that recovery of oils was about 99 wt. % and recovery of solvent was 96 wt. % inclusive of all weighable materials sticking on various surfaces. Even free water employed to boil out solvent from oils was retrieved up to 98 wt. %. The sand recovered was oil free and whose wt. % loss on heating at 815°C for 1 hour was 0.11 wt. % which was less than 0.16 wt. % for oil free, fresh sand. The turbidity was observed to be only 0.56 NTU as against the value of 1.2 NTU for water that was used for washing fines free fresh sand. The recovered ONGC free flowing oil was håving only 3,420 ppm of residual moisture with a calorific value of 10,580 kcal/kg as against residual moisture of 3,900 ppm and calorific value of 10,652 kcal/kg for original ONGC Oil. It was seen that the recovered furnace oil was håving residual moisture of about 3,123 ppm with calorific value of 10,164 kcal/kg as against original furnace oil håving residual moisture of 2100 ppm and calorific value of 10,173 kcal/kg. It was seen that the recovered Solvent had barely 153 ppm moisture in it on an average as against 40 ppm moisture in original Xylene used.

Further, it was observed that amount of Xylene required to wash unit mass of oil coated sand depends on both the type of oil that coats the sand and the amount of oil coating the sand. The weight of Xylene required was about 7 times the weight of oily sand for removing 9.2 wt. % ONGC free flowing oil. The weight of Xylene required was instead about 13 times for completely de-oiling the sand that contain 13.12 wt. % Furnace oil.

EXAMPLE-19

EFFECT OF TIME RELATED CHANGE IN TURBIDITY VALUES OF SLOP OILS

It was an aim to evaluate change in turbidity values of slop oils with time. Further, it was an aim to observe which hydro-carbons fragment easily to produce stable slop oils. Also, it was an aim to study why solvents behave differently from oils. Accordingly, slop oils were prepared with different oils and solvents. These oils/ hydrocarbons were added to water in varying parts per million and then vigorously fragmented in high shear mixer at 10,000 RPM over varying time. Subsequently, a representative sample was subjected to Turbidity test at wavelength of 455nm with Hach Turbidity Meter. The turbidity readings were measured in NTU (Normal Turbidity Unit) thereby taking turbidity values of these slop oils at regular intervals of time till they reached near constant values.

It was observed that unlike Xylene and Toluene, Benzene failed to easily fragment or remain fragmented into fine droplets even over short periods of time with vigorous stirring in water and therefore Benzene was believed to be not as suitable as Xylene and Toluene for mopping up ultra-fine oil droplets from slop oils. This was indicated by its turbidity values of 8 to 12 NTU as shown in FIG. 7 and FIG. 8. The turbidity values of transparent liquids were indicative of population density of droplets håving diameters of order of 455 nm per unit volume of liquid.

Slop Oils contain all sizes of oil droplets. Amongst them, ultra-fines were found to be most difficult to mop up. Benzene was found little less effective than Xylene and Toluene when removal of ultra-fine droplets was an object. It was found that very large droplets of solvents were berter suited for removing all oil droplets, other than a fraction of those which were ultra-fine in size. Large droplets of solvents work faster in removing bulk of the oil present. As these were the ones that swept away and then carried with them large numbers of smaller oil droplets while rising up due to buoyancy.

It was seen that only a tiny fraction of total oil present resided in difficult-to-remove ultra-fine droplets. However, the ultra fine droplets were found contributing towards turbidity to a certain extent. Hence, relatively very large droplets of solvents like those of Benzene or even Xylene and Toluene cannot lower turbidity of slop oils beyond a point when they were hand mixed into slop oils, with mild mixing in particular.

Accordingly, it was established that one must use solvents that immediately fragment into ultra-fine droplets and then quickly coalesce into very large sized droplets to derive advantages of all sizes of solvent droplets. Although both Xylene and Toluene were found good for processing Slop Oils, however, Xylene was found to be berter than Toluene since it initially fragmented into a lot smaller sized droplets.

FIGS. 9 -12 as against FIGS. 13-20, bear testimony to a statement that good solvents coalesce very rapidly unlike hydrocarbons present in the slop oils. Most dispersed hydrocarbons, other than few like Diesel, took days to coalesce and reduce their turbidity. However, the turbidity values of Toluene and Xylene fell down in hours. Also, it was seen that the turbidity values of Xylene and Toluene fell down sharply with increasing concentration, unlike those of most hydrocarbons. This can be clearly seen by comparing FIG. 9 with FIG. 14. It was seen that, with solvents, higher concentration did not lead to higher population density of ultra-fine droplets. Instead it triggered instant coalescence.

Further, it was seen that turbidity values of Toluene and Xylene dropped down steeply by increasing mixing time at 10,000 RPM. This was contrary to what happened with most hydrocarbons, including Diesel. For hydrocarbons like Diesel and ONGC Oil, increased time of mixing caused further fragmentation with increased population density of ultra-fine droplets. But for coconut oil it initially narrowed variations in droplet size. The slop oil may be made lot more stable by making droplet size more uniform with which turbidity values do not change with time.

For solvents, however, more mixing resulted in unstable rise in surface energy which then triggered immediate coalescence. It was seen that by extending mixing time from 1 to 5 minutes at 10,000 RPM and for 2500 ppm, the turbidity value of Toluene fell down from 1,570 and 4,682 NTU to 54 and 874 NTU. It was established that solvent coalesced rapidly that helped them to grow into large droplets quickly that reduced drag which then helped them to rise rapidly due to buoyancy. Here, Toluene was observed to surpasses Xylene.

In case of Diesel, it was seen that Diesel too got fragmented initially but not as much as Toluene and Xylene. It was also seen that Diesel was extremely fast as compared to other hydrocarbons with regard to coalescence, but still not found as fast as that of Toluene and Xylene. After 13 mins of mixing at 10,000 RPM turbidity values for 2,500 ppm Diesel Slop Oil was 3,852 NTU, while for same ppm & RPM, turbidity values of Toluene and Xylene after 5 mins of mixing alone were 54 and 874 NTU respectively. However, as clearly seen in FIG. 21, Diesel based Slop Oils were found easiest to be processed for recovery of oil and clean water due to rapid coalescing nature.

In case with 2,500 ppm coconut oil in water håving 3 mins of mixing at 10,000 RPM gave very stable slop oil. But this stability vanished with further increase in mixing time. Accordingly, it was established that for very stable coconut oil based slop oils, one must begjn with vigorous mixing before beginning to process them for recovery of pure oil and water.

It appeared that highly stable ONGC free flowing oil based slop oils could be formed either by extending their time of mixing or by increasing their hydrocarbon concentration. However, it was found uncertain that to what extent that value depends on color of slop oil and to what extent on oil droplet size.

EXAMPLE-20:

EFFECT OF HEAT ON TURBIDITY OF SLOP OILS

It was an aim to understand the effect of heat on turbidity of slop oils when heated in an oven at 85 to 95 °C for few hours or subjected to vigorous boiling for five minutes. Accordingly, low and medium turbidity slop oils were prepared with Coconut Oil and Free Flowing ONGC Oil as explained below in Table Nos. 20.1 and 20.3. Only the turbidity values were measured for low turbidity slop oils immediately before and after heating. Additionally, Coconut Oil based slop oils with medium turbidity were subjected to our five-step process meant for reduction in turbidity, with and without initial heating as explained in Table 20.4. The study on effect of vigorous boiling on turbidity of slop oils as shown in tables 20.1 and 20.2 was found to be important because that was limited to low turbidity, less ppm slop oils alone. This kind of slop oils were obtained after 2nd step of our 5-step process, i.e. after centrifuging for third time with solvent and then removing entire topmost layer of solvent cum hydrocarbons.

Thereafter entire dispersed solvent from slop oils was boiled out with help from free water present therein. While so doing, we wanted to separately evaluate the impact of boiling alone, apart from that of solvent removed, on residual turbidity of slop oils.

The study here showed that impact of boiling was small unless residual value of slop oils after boiling out solvent was high. The impact of boiling was further reduced for residual values ranging from 38 to 69 NTU and turbidity of slop oils by 2.09 to 4.5% of residual values. However, for high residual values like 435 NTU, reduction in turbidity on account of boiling alone was by 33% of residual turbidity value. Boiling related reduction in value was additional to that due to removal of solvent. The part of these reductions in turbidity values were on account of passage of time too. Accordingly it was concluded that impact of boiling can be neglected for low residual turbidity values.

As seen in table nos. 20.3 and 20.4, about 9 to 14 % immediate reduction in turbidity values was observed with medium turbidity coconut oil based slop oils due to heating without removing impact of passage of time. This impact was observed to be more with boiling. Effect of heating or boiling on turbidity values of coconut oil based slop oils progressively reduced with subsequent processing of slop oils. It was seen that the impact of both heating and boiling was completely vanished after boiling out solvents or prior to adding of alum. Hence, it was ascertained that prior heating or boiling of slop oils is not required.

EXAMPLE- 21

TIME ADJUSTED EFFECT OF SOLVENT ALONE ON REDUCING TURBIDITY OF SLOP OILS

An impact of using low viscous solvent, like Toluene, alone on reduction in turbidity of slop oils after removing the impact of time from reported turbidity results was studied.

Accordingly, 5 Wt. % Toluene was added to the prepared slop oils. Toluene was mixed in them using high shear mixer at 10,000 RPM for 1 minute. Before addition of Solvent, Slop Oils were tested for turbidity and time was noted. Solvent added samples were allowed to stand for 20 hours for most Oil and Solvent to collect at the top. Later, top layer containing solvent and oil was separated from each Slop Oil Sample and remaining material was tested for turbidity after homogenization and again the time was noted. Subsequently, entire residual solvent was boiled out, in temperature range of 95 °C to 98 °C from remaining material with help from free water present in sop oil. After cooling, make up water was added to replace the water lost through boiling. Thereafter, slop oils were again tested for turbidity and time was noted. Here each turbidity value of test sample was time-adjusted. This was done with control samples where turbidity values continuously changed, often only reducing, with passage of time. After identical elapsed time, turbidity values of control samples were added to those of test samples that removed the impact of time from reported values, thus reflecting the impact of solvent alone.

For slop oils produced from ONGC Free Flowing Oil, impact of mixing time required for their production was large compared to that for Coconut Oil based slop oils. It was observed that the turbidity value went up from 5,626 to 9,894 NTU for 2,500 ppm ONGC slop oil with increase in mixing time from 1 to 5 minutes. Under same conditions, for Coconut Oil based Slop Oils it rose from 4,354 to 4,856 NTU. For Slop Oils produced from ONGC Free Flowing Oil impact of increase in concentration of hydrocarbons on turbidity value was also slightly larger than that for Coconut Oil based Slop Oils.

It was seen that addition of Toluene never helped, either with Coconut or with ONGC slop oils. It could not reduce turbidity of these slop oils inspite of removing large amounts of hydrocarbons from slop oil and retaining them in the topmost layer along with it. On the contrary, after addition of solvent turbidity values infact went up inspite of boiling entire solvent that was added. For 2,500 Slop Oils rise in value was lot more in case of 1 minutes mixed Slop Oils as compared to 5 minutes mixed Slop Oils.

Solvent was invariably added into slop oils by mixing it for 1 minute at 10,000 RPM. Probably this mixing might have further fragmented existing droplets of Coconut Oil and ONGC Oil and that could have raised turbidity values by increasing the population density of ultra-fine droplets. Impact of further fragmentation was expected to be higher in case of slop oils produced through 1 minute of mixing as compared to those that had been generated after 5 minutes of mixing. Hence turbidity values of slop oils after 1 minute mixing we found to be increasing a lot more. Probably use of solvent might have failed also because most of the solvent got consumed removing large oil droplets. Consequently, ultra fine droplets might have been remained intact with additional need of solvents in batches.

It was seen that with 5,000 ppm slop oils, the differential rise for 1 and 5 minutes slop oils could not be established as final values exceeded our test equipment range. However, with 5,000 ppm Coconut Oil based Slop Oils, at least their turbidity values went up with use of solvent even after boiling out the entire solvent that was added.

EXAMPLE-22

TIME ADJUSTED EFFECT OF CENTRIFUGE ALONE ON REDUCING TURBIDITY OF SLOP OILS

Effect of centrifuge alone on reducing turbidity of slop oils after removing the impact of time from reported turbidity results was studied. Accordingly, the slop oils were prepared using Free Flowing ONGC Oil and also Coconut Oil under parameters as explained in table nos. 22.1 and 22.3. Table Nos. 22.2 and 22.4 showed time adjusted results of three rounds of centrifuge as well as the conditions under which samples were centrifuged. After each round of centrifuge turbidity values were tested and time was noted only after carefully removing the entire top layer of accumulated oil. It was understood that meaning of time adjusted results have been explained under procedure explained in Example-21.

TABLE 22. 1- PRODUCTION OF ONGC OIL BASED SLOP OIL USING HIGH SHEAR MIXING MACHINE

~SL~| DESCRIPTION I TEST I TEST I TEST I TEST

JNO. 12 3 4

1 Total Mass of Slop Oil (kg) 0.49 0.50 0.51 0.50 2 Mixing Time (min) 15 15 3 RPM of Mixing 10,000 10,000 10,000 10,000 4 Oil content in Slop Oil (ppm) 2,496 2,486 5,001 4,993 ^ Time elapsed before checking of Turbidity ^ 02 335 419 410

(min)

6 Average Turbidity of Slop Oil (NTU) 5,911 >10,000 >10,000 >10,000

TABLE 22. 2- RESULTS OF CENTRIFUGING ABOVE ONGC OIL BASED SLOP

OILS

~ST1DESCRIPTION TEST TEST TEST TEST

No. 12 3 4

Step:l Centrifuging of Slop Oil at 4,500 RCF with NIL residence time at peak

RCF value

-^"Turb^ 5,911 >10,000 >10,000 >10,000 2 JJJ^y0f S1°P0il *lst Centri&8e ^ 2^ 2^ 4,682 ;_ Turbidity of Slop Oil after 2nd Centrifuge 0O1 ,n.(i, -10inna;(NTU) l,/4o 1,3 lo .5,y/o ;. Turbidity of Slop Oil after 3rd Centrifuge 011 , , _ ;(NTU) ijOjy ijZou ;TABLE 22. 3- PRODUCTION OF COCONUT OIL BASED SLOP OIL USING ;HIGH SHEAR MIXING MACHINE ;"SL~| DESCRIPTION I TEST I TEST I TEST I TEST ;JNO. 12 3 4 1 Total Mass of Slop Oil (kg) 0.49 0.49 0.50 0.49 ;2 Mixing Time (min) 15 15 3 RPM of Mixing 10,000 10,000 10,000 10,000 4 Oil content in Slop Oil (ppm) 2,496 2,499 4,975 4,990 ; It was seen that the turbidity values of slop oils prepared from Free Flowing ONGC Oil was always higher than that of Coconut Oil based slop oils prepared under similar conditions. The turbidity of Coconut Oil based Slop Oils increased both with mixing time employed for their preparation and also with concentration of hydrocarbons present wherein the concentration of hydrocarbons present was håving greater impact than mixing time. ;Time adjusted impact of centrifuge was found to be substantially dependent on starting turbidity values. It progressively reduced turbidity with every successive operation. It was seen that impact of first round of centrifuge was large. In successive rounds, the impact kept diminishing. It was observed that the centrifuge was lot more effective in removing large sized oil droplets since the impact of drag was less on the droplets. It was seen that force of buoyancy worked berter with large sized droplets with substantial reduction in turbidity in the first round. It was seen that the centrifuge became ineffective due to one or more of the following reasons. ;Firstly, centrifuge could have become ineffective once size variations of dispersed oil droplets became narrow. Secondly, centrifuge could hav ;e become ineffective once population density of dispersed droplets falls with increasing mean free path. Thirdly, centrifuge could have become ineffective as initial turbidity values were too large. Fourthly, centrifuge could have become ineffective due to dispersed oil droplets that might have electrically charged. Lastly, centrifuge could have become ineffective due to small density difference between oil and water. ;It was established that narrowing of variations in droplet size could have resulted in movement of all droplets with same velocity and acceleration. This could have resulted in fewer collisions and slower rate of coalescence. Also, efficacy of centrifuge could have dropped down with absence of sweeping effect of large sized oil droplets. Further, uniform size of dispersed droplets could have impaired the centrifuge lot more than their small population density with large mean free path. It was seen that with too high initial turbidity value or initial population density of ultra-fine oil droplets, the centrifuge slowed down and that then impacted its efficacy. It was seen that, residual turbidity after 3rd attempt at centrifuge was invariably large when initial turbidity values were high. ;It was concluded that the centrifuge cannot reduce turbidity of slop oils to the required value of 1 to 4 NTU. In fact, the limiting turbidity values of the centrifuge were lot higher. This was more so in cases of colored slop oils. It was further concluded that the density difference between oil and water and also the RCF and residence time inside the centrifuge play significant role in this regard. ;EXAMPLE- 23 ;TIME-SOLVENT-CENTRJFUGE ADJUSTED COMBINED EFFECT OF CENTRIFUGE AND SOLVENT ALONE, ON REDUCING TURBIDITY OF SLOP OILS ;Combined use of Solvent and Centrifuge on reducing Turbidity of Slop Oils was studied after removing individual effects of time, centrifuge and also that of solvent, from all reported turbidity results. Accordingly, slop oils were prepared under conditions given in table nos. 23.1 and 23.3. Subsequently, the turbidity values of slop oils were measured. Thereafter, these slop oils were centrifuged twice with nil residence time at maximum RCF of 4,500. Further, the solvents were added by mixing them into slop oils for 1 minute at 10,000 RPM. Thereafter, the contents were centrifuged once again with nil residence time at maximum RCF of 4,500. Subsequently, residual solvent from slop oil was boiled out in temperature range of 95 °C to 98 °C with help from free water present in slop oils after entirely removing the top layer of solvent cum oil. After cooling, make up water was added that was lost through vigorous boiling. Then, the remaining material was tested for turbidity values and also the time was noted. To remove impact of time, we added to above results the amount by which turbidity values would have reduced if we had retained them in vessels for same periods of time since their production. Next to remove the impact of solvent alone, the time adjusted amount by which turbidity values went up on addition of solvents into slop oils by mixing them in for 1 minute at 10,000 RPM was subtracted. Finally, to remove the impact of centrifuge alone, we added to above results the time adjusted amount by which turbidity values of slop oils had got reduced after centrifuging them thrice with nil residence at maximum RCF of 4,500. It was seen from test Nos. 2,3 and 4 in table 23.2 and test Nos. 3 and 4 in Table 23.4 that we could not get values because we could quantify the impact of adding solvents to slop oils for these tests as can seen from table Nos. 21.2 & 21.4. However, without quantifying the impact of using solvents, we cannot remove the impact of solvent for these tests. ;However, from test no. 1 for 2,500 ppm ONGC Oil based Slop Oil and from test no. 1 and 2 for 1 and 5 minutes mixed, 2,500 ppm Coconut Oil based Slop Oils, it was found that these two unit operations reduced turbidity of slop oils only when combined. The table nos. 23.2 and 23.4 show that there was a synergetic effect in combining the use of Solvent with that of centrifuge. Use of Solvent alone actually increased the turbidity of Slop Oils by a large margin. Use of centrifuge by itself succeeded well, only when initial turbidity values were not large. But when solvent was combined with centrifuge, it not only wiped out the entire negative impact of using solvent alone, but it additionally benefited in cases where initial turbidity values where large like ONGC slop oils. ;It was ascertained that the centrifuge must preferentially be used for removing large oil droplets while solvents must be used for removing ultra fine droplets. Solvents must be added only after centrifuge has ceased to be effective for want of wide droplet size distribution or low population density of fine droplets or small density difference between oils and water. This combination was found must when initially turbidity of slop oils was large. ;EXAMPLE-24 ;EFFECT OF USING ALUM ON REDUCING TURBIDITY OF SLOP OILS ;Impact of alum addition on reduction of turbidity of slop oils was studied. Accordingly, slop oil samples were prepared with both low and high turbidity values as per conditions mentioned in below mentioned tables 24. IA and 24.2A. Alum was added and settling time was provided as per figures mentioned in tables 24. IB and 24.2B. Alum was added in 3 different proportions for high turbidity samples and turbidity values were evaluated over 4 days with and without adjusting the effect of time. ;Effect of Alum on low ppm slop oil- ; ; Effect of Alum with different compositions on slop oil- ; It was observed that impact of Alum on reducing turbidity of slop oils in 24 hours was more when initial turbidity values were large. As seen in table 24.2B, on removing the impact of time, one can see that Impact of Alum alone on reduction of turbidity values of slop oils was about 1.5 times more than that of time itself. ;As seen from table 24.3B, addition of 0.05 wt. % alum is not adequate when initial turbidity values are more than 10,000 NTU. Addition of Alum must be increased to 0.1 wt. %. However, beyond addition of 0.1 wt. % alum there was no further improvement seen. Hence, it was ascertained that amount of Alum added was important only when one was interested to get quick results in a day or two. Combined impact of alum and time was more than adequate to reduce turbidity values from greater than 10,000 NTU to about 5.5 NTU if given 24 hours. However, then removal of the oil layer contaminated with Alum from water was found rather difficult. Besides, calorific value of oil was reduced by 2% as shown below in Example-29. Also, it was observed that alkali content of oil went up with contamination from Alum. It was also observed that viscosity of oil dramatically changes per wt. % of Alum present therein. ;EXAMPLE-25 ;EFFECT OF COMBINED USE OF ALUM, HEAT AND TIME ON REDUCING TURBIDITY OF SLOP OILS ;It was an aim to evaluate the impact of combined use of Alum, heat and time on reducing turbidity of slop oils and comparing that with just the use of alum with time alone. Accordingly, low turbidity slop oil samples were prepared as per conditions mentioned in table-25.1. Thereafter, Alum was added and kept part of samples at ambient conditions and their initial and final turbidity values were tested over varying time from 3 hours to 5.8 hours. The remaining part of samples were heated in oven at 80 °C over varying time from 1 to 4 hours and even these were tested for initial and final turbidity values. Subsequently, make up water was added for heated samples to replenish evaporated water. ; As can be seen from table 25.2, the combined impact of alum, heat and time was found to be far berter than that of just alum and time alone, on reduction of turbidity values of low turbidity ONGC and Coconut Oil based Slop Oils. In Test-1, it was observed that turbidity value fell down by 73% in 5.04 hours in case on non-heating of Alum added slop oil. However, Alum added slop oil when heated at 80 °C for 4 hours, the turbidity of the slop oil fell down by 93% in 5.11 hours. In tests 2, 3 and 4 when not heated turbidity values were in fact found to be increased by 2.3%, 35.3% and 9.6% in 5.84, 3.44 and 4.56 hours respectively. The turbidity values of slop oils actually went up even more than their initial values with time when Alum added slop oil was not heated with lower initial turbidity and lesser settling time. ;However, the turbidity value fell down by 67% instead in case where Alum added slop oil sample when heated at 80°C even with low initial turbidity value of 56.1 NTU and even with less time of 1 hour. Also, with initial turbidity value of 42.1 NTU and with 4 hours of heating at 80°C the fall was 93% in 5.11 hours. It ascertained that more the length of time over which samples were heated faster was the fall in turbidity values. This experiment established the fact that treatment with Alum could be speeded up to reduce our overall processing time if needed by applying low intensity heat. ;EXAMPLE-26- ;EFFECT OF FILTRATION ON REDUCING TURBIDITY OF SLOP OILS ;In order to evaluate impacts of fast and slow filtration rates on reduction of turbidity values of high and low initial turbidity slop oils, the slop oil samples were prepared as per conditions mentioned in table 26.1. These samples were filtered repeatedly four times using 40 and 41 Grade Whatman cellulose Filter Papers. In one set of readings the same filter paper was repeatedly used while in the other set of readings new filter papers were used each time. The turbidity values were noted before and after each filtration. The time tåken for filtration of a given weight of slop oil was also noted each time to arrive at the rate of filtration. ; It was seen that 40 Grade Whatman filter paper håving 8 micron pore size gave much lower turbidity values after each filtration however found to be slow while filtering. It was even slower when the same paper was repeatedly used each time. It was also found to be far slower in case of high turbidity slop oils. It was observed that the process slowed down but the quality of filtrate was improved with repeated use of same filter paper in order to get lower turbidity values. It was seen that filtration failed to gjve consistent results each time. The rate of filtration changed each time and reduction in turbidity values also changed accordingly. It was seen that efficacy of filtration was dependent on the nature of hydrocarbon in the slop oil. For instance, as can be seen from Table 26.2 that filtration was lot less effective for Coconut Oil based slop oils than ONGC Oil based slop oils. ;However, it was seen that other than as finishing step for reduction of last bits of turbidity values it was found to be a desirable industrial process because of one or more of the following reasons. Firstly, the filtration process was found to be very slow process. Secondly, the filtration process was found to be an inconsistent process. Thirdly, the filtration medium was found to be blocked fast when pore size was small thereby making further process even slower. Fourthly, the hydrocarbon present in slop oil cannot be recovered easily or in saleable form. Lastly, presence of solids in slop oils further impaired this process in terms of its efficacy and flow rates. ;EXAMPLE-27 ;EFFECT OF COMBINING USES OF ALUM AND FILTRATION ON REDUCTION OF TURBIDITY OF SLOP OILS ;In order to evaluate impact of combined use of both Alum and filtration on reduction of turbidity of slop oils håving both low and medium turbidity values, slop oil samples were prepared under conditions mentioned in below tables 27. IA and 27.2A. Alum was added to these samples after testing for initial turbidity values 0.05 wt. %. The turbidity values of these samples were tested again after close to 24 hours. Further, the samples were successively filtered with Grade 41 and then with Grade 40 Whatman Cellulose Filter Papers and after each filtration reduction in turbidity values were recorded. ;Effect of Alum and filtration on Turbidity of Low ppm Slop Oils- ; ^DESCRIPTION™ TE2ST TE3ST ;1 Turbidity of Slop Oils before adding Alum (NTU) 4,755 4,675 484 2 Wt.% Alum added to Slop Oils 0.05 0.05 0.05 3 Time permitted for Settling (Hrs) 23.08 24.00 25.08 . Turbidity Values without adjusting impact of Time 1 „ 7 „ , ;4 ( NTU ) ;- Turbidity Values after adjusting impact of Time 170? 1 cm (NTU) i,/uz i,yzj _ ;, % Reduction in Turbidity of Slop Oils by adding on n, on „ O0 00 o 41 yy.uj yy.ou yo.zz ;Alum ;7Turbidity of Filtrate after using 41 Grade1,7„ . ? Whatman Filter Paper ( NTU) ;„ Turbidity of Filtrate after using 40 Grade „ „ „ 1 ;I Whatman Filter Paper ( NTU ) | U 38 | U // | 1U3 ;It was observed that percentage impact of Alum was lot more, in same time span and with same dosage, for slop oils with large initial turbidity values as can be seen by comparing table nos. 27. IB and 27.2B. It was further seen that Alum could make use of centrifuge and solvent redundant. But it was hold untrue. This was because Alum took the same time and dosage to reduce turbidity of slop oil from 4,755 to 45 NTU as much as it took to reduce it from 45 to 4.5 NTU. Alum was needed to reduce turbidity up to 2-5 NTU. Therefore, it was ascertained that starting turbidity for Alum must be below 60 to 70 NTU. Once turbidity values were brought down from 2-5 NTU then even fast filtration was observed to be very effective for delivering water with around 1 NTU and also the load on or blocking of filtering media was observed to be small. Secondly, Alum was found to be adversely affecting the quality of oil collected from slop oils. Accordingly, it was ascertained that if quality of oil collected is not important and if time tåken for filtration and saturation of filtering media can be ignored, then alum cum filtration can make the use of centrifuge and solvent redundantly as far as processing of slop oils is concerned. ;EXAMPLE- 28 ;OVERALL EFFECT OF COMBINING THE USE OF CENTRIFUGE, SOLVENT, ALUM & FILTRATION WITH VARYING SOLVENTS ON REDUCING TURBIDITY OF VARIOUS SLOP OILS ;It was an aim to evaluate combined effect of centrifuge, solvent, alum and filtration and also the effect of various solvents on reducing turbidity of slop oils prepared from various oils/hydrocarbons. Accordingly, slop oils were prepared as per conditions mentioned in table nos. 28.IA, 28.2A, 28.3A, 28.4A, 28.5A, 28.6A and 28-7A. Procedures of preparation were also mentioned in table nos. 28.IB, 28.2B, 28.3B, 28.4B, 28.5B, 28.6B and 28.7B. Subsequently, solvents like Toluene and Xylene were used mixed in different proportions. The solvents were mixed with the slop oils using high shear mixer at 8,090 RPM for 1 minute. The oil content in slop oils was varied from 5 PPM to 4, 99,052 PPM. The various oils used were selected from one or more of the following Coconut Oil, Furnace Oil, Diesel, ONGC Free Flowing Oil and ONGC viscous hydrocarbons. Subsequently, all four processing steps involving the use of Centrifuge, Solvent, Alum and Filtration were employed in sequential manner. Accordingly, following observations were made. ;Coconut oil based slop oils- ; ; It was observed that when water insoluble solids are present in slop oils, like those containing ONGC viscous hydrocarbons, it was necessary to incorporate filtration after addition of alum to get low turbidity values as filtration was found to be more effective in removing very fine ash particles. This could be seen from Table 28.7B. It was further ascertained that the diesel slop oils were the easiest to process. ;Further, it was seen that incorporation of all four unit operations like centrifuge, addition of solvent, addition of alum followed by filtration in process made processing of the slop oil faster with least operative problems and with excellent results. Further, it was seen that the pollution problem was found to be entirely mitigated. Besides, it was found that said operations entirely recover almost excellent quality hydrocarbons and water for use or sale. Energy consumption was found to be very small. Also, the solvent employed was fully recovered in its original form for re-use. ;It was seen that the quantity of solvent required and mode of solvent addition were dependent on quantity of hydrocarbons present in slop oils. The quantity of solvent required was more when hydrocarbons were lot more and least agjtation was needed while adding solvent. It was seen that mere hand shaking was preferred mode of adding solvent when hydrocarbon content in slop oils was high as can be clearly seen from test 4 in table 28.6B. It was also seen that even mild hand shaking was equally effective. It was also seen that with collection of hydrocarbons became very easy with the use of solvent. The weight percent collected also went up. Finally, it was seen that often solvent cum oil layer was håving very little water therein. ;EXAMPLE-29 ;EFFICACY OF THE PROCESS OF PRESENT INVENTION WITH SLOP OILS CONTAINING VERY HIGH HYDROCARBON CONTENT ;It was an aim to study efficacy of the combined process with slop oils håving very high hydro-carbon content inclusive of recovery of hydrocarbons and solvent. Accordingly, the slop oils were prepared with Coconut Oil under conditions as mentioned below in table 29.1. These slop oil samples were retained in a separating flask for 48 hours that lead to formation of three layers. The top layer obtained was containing pure oil. The middle layer obtained was containing oil and water both while the bottom layer was containing mostly water with little Oil therein. The bottom layer was removed and treated as slop oil along with slop oil coming from middle layer as explained below. ;The middle Layer was treated with Alum and retained in Separating Flask for another 48 hours that lead to further formation of three layers, i.e. top layer containing pure oil, middle layer containing oil and alum with water and bottom layer of slop oil. The layer containing alum was dried and tested for Calorific Value. The weight percent recovery of pure coconut oil from top and middle layers and calorific value of dried alum layer can be seen in table 29.2 while results of treatment of slop oil along with weight percent recovery of coconut oil cum solvent can be seen in table 29.3. ; It was observed that, for a given hydrocarbon, higher the quantum of hydrocarbons in Slop Oils; easier it was for pure hydrocarbons to separate out with settling. Also, it was observed that presence of Alum in coconut oil reduced its calorific value by 3.2 wt.% apart from making it viscous and increasing its alkali and ash contents. ;EXAMPLE-30 ;QUALITATIVE AND QUANTITATIVE RECOVERY OF HYDROCARBONS, SOLVENT AND WATER FROM LARGE SAMPLES OF SLOP OILS USING ENTIRE PROCESS OF THE PRESENT INVENTION ;It was an aim to study efficacy of the process of present invention with large scale slop oils by evaluating the quantity and quality of hydrocarbons, solvent and water recovered. Accordingly, the slop oil samples were prepared as per conditions mentioned in table 30.1. The slop oils were then treated as per procedure mentioned in table 30.2. Subsequently, hydrocarbons and solvent layer removed from step-3 in table 30.2 was next treated as per procedure mentioned in Example-15 and Example-16. The results obtained can be clearly seen in table 30.3. ; ; It was observed that the qualitative cum quantitative recoveries of solvent and water from above slop oils were extremely good. It was further seen that small fractions of hydrocarbons were boiled out with solvent thus depressing its weight percent recovery. Finally, it was seen that moisture in ONGC hydrocarbons could have been lower if said process had opted for hot settling over 48 hours. Finally, it was observed that it was lot more difficult to remove free water from viscous hydrocarbons. ;The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and verifications are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detail ed description, but rather by the claims appended hereto. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention described herein. *

Claims

1. A process for treatment of a sludge mixture håving hydrocarbons with bound water, unbound water, dissolved and un-dissolved solids therein, the process for treatment of the sludge mixture comprising the steps of: a) Centrifuging the sludge mixture in a first centrifuge provided the sludge mixture splits into various components, the first centrifuge being a batch or Multi-Pass centrifuge, the said centrifuge forming a viscous hydrocarbon layer, a slop oil layer and a free flowing hydrocarbon layer; b) Desalting the viscous hydrocarbon layer from step a)in a first desalter followed by optional treatment thereof in a heat based low volatiles stripping vessel for removing vapors of low boiling liquid hydrocarbons therefrom; c) Condensing the vapors of low boiling liquid hydrocarbons from step b) in a first condenser for obtaining low boiling liquid hydrocarbons along with water for use; d) Optionally desalting crude hydrocarbons coming from a group collection center in a second desalter for obtaining desalted product crude and removal of abound water containing hydrocarbon layer followed by mixing the bound water containing hydrocarbon layer with the viscous hydrocarbon layer from the first centrifuge; e) Desalting the free flowing hydrocarbon layer from step a) in a third desalter for entire removal of salts therefrom; f) Homogenizing the viscous hydrocarbon layer from step b) in a homogenizer by adding a first predefined amount of solvent for forming a volatiles free non-viscous homogenized stream therefrom; g) Performing BTX and Ash tests of the non-viscous homogenized stream from step f) followed by treatment thereof in an agitator cum homogenizer thereby adding a second predefined amount of solvent therein in accordance with the BTX and Ash tests results; h) Centrifuging the non-viscous homogenized stream from step g) in a second centrifuge for separating a bound water dominant hydrocarbon stream, an unbound water dominant or water free hydrocarbon stream and the slop oil therefrom; i) Optionally treating the non-viscous homogenized stream from step g) in a hot insulated settling tank for removal of water free solvent along with hydrocarbons therefrom; j) Heating the unbound water dominant or water free hydrocarbon stream from step h) in a first heating vessel thereby optionally adding a predefined amount of free water therein, the first heating vessel operating at a first predefined temperature range thereby forming a first residual phase and a first vapor phase therein; k) Heating the bound water dominant hydrocarbon stream from step h) in a second heating vessel at a second temperature range thereby optionally adding a third predefined amount of additional solvent therein, the second heating vessel forming a second residual phase and a second vapor phase therein; 1) Centrifuging the first residual phase from step j)in a hot centrifuge at a second predefined temperature for obtaining volatiles free desalted product hydrocarbons in a range of about 96 wt% to 100 wt% along with unbound water håving turbidity at least below 20 NTU; m) Treating the second residual phase from step k) in the first heating vessel; and n) Condensing the first vapor phase from step j) and the second vapor phase from step k) through a second condenser for obtaining almost 100% solvent, the bound water in a range of about 99 wt% to 100 wt % wherein the free water in a range of about 94 wt. % to 100 wt. % is collected through entire process, the solvent being reused in said process.

2. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first centrifuge substantially reduces quantum of the sludge mixture with bound water that facilitates further processing with reduced cost and time in downstream processing of said process.

3. The process for treatment of the sludge mixture as claimed in claim 1, wherein the free flowing hydrocarbon layer is about 41 wt% typically håving 3,864 ppm water and 0.88 wt.% ash with calorific value ofl0,635 kcal/kg.

4. The process for treatment of the sludge mixture as claimed in claim 1, wherein the viscous hydrocarbon layer is håving at least 42.21 wt.% water typically håving 8.61 wt.% Ash with CV of 5,210 kcal/kg.

5. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first centrifuge enhances separation between the components present in the sludge by extending a period of residence time of the sludge thereby gradually varying revolutions per minute of the batch centrifuge enabling collection of slop oil behind the viscous hydrocarbon layer.

6. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first desalter, the second desalter and the third desalter retain the quality of hydrocarbons coming from different process streams and hence improve commercial value thereof.

7. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first desalter, the second desalter and the third desalter prevent needless repetition of identical processes being done in group collection center for removal of bound and unbound water from crude again into refineries after desalting of the crude.

8. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first desalter, the second desalter and the third desalter prevent ingression of water into various product hydrocarbon streams in refineries thereby preventing accumulation of sludge in downstream of said process and in vessels utilized in refinery onward processes.

9. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first desalter, the second desalter and the third desalter allow the group collection center to dispatch crude without salts and without håving to worry about either disposal or processing of crude containing bound water.

10. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first desalter, the second desalter and the third desalter prevent possibility of corrosion of pipelines and tankers during transportår!on.

11. The process for treatment of the sludge mixture as claimed in claim 1, wherein the heat based stripping vessel separates the low volatiles from the viscous hydrocarbon layer for preventing co-distillation of the low volatiles with the solvent during removal of the bound water with solvent in downstream of said process.

12. The process for treatment of the sludge mixture as claimed in claim 1, wherein removal of the bound water from the hydrocarbon layer allows removal of heavy metal, Ash and salts therefrom for effectively improving commercial value.

13. The process for treatment of the sludge mixture as claimed in claim 1, wherein the BTX and Ash tests help assist in determination of an optimum amount of solvent to be added in said process.

14. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent reduces viscosity for removal of bound water from topmost layer of the non-viscous homogenized stream on account of viscosity.

15. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent help assists in homogenization of the sludge that in turn helps in sampling and accurate determination of water and Ash content.

16. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent is added in said process only for viscous portion of the hydrocarbons which substantially reduces overall use of solvent in said process.

17. The process for treatment of a sludge mixture as claimed in claim 1, wherein the solvent is selected from the group of Benzene, Toluene, Xylene and similar Azeotropes of water.

18. The process for treatment of the sludge mixture as claimed in claim 14, wherein the solvent removes the bound water from the top most layer with least possible thermal damage to the product hydrocarbon stream in said top most layer.

19. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent stream and the second centrifuge mutually remove substantial bound water from the viscous hydrocarbon layer at an ambient temperature.

20. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent depresses the boiling point of the bound water.

21. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent is added in a range of about 1.8 to 100 times the weight of water present in the sludge for entire removal of the bound water.

22. The process for treatment of the sludge mixture as claimed in claim 1, wherein the solvent has a left over weight ratio of solvent to hydrocarbon in a minimum range of 2.00 to6.00 for entire removal of the bound water at least temperature.

23. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first predefined temperature of the first heating vessel is in a range of about 90°C- 105°C.

24. The process for treatment of the sludge mixture as claimed in claim 1, wherein the hot centrifuge has a temperature in a range of about 80 °C to 94°C.

25. The process for treatment of the sludge mixture as claimed in claim 1, wherein the hot centrifuge is a hot settling tank that ensures adequate reduction in viscosity of hydrocarbons thereby allowing settling of free water therein over a predefined period of time.

26. The process for treatment of the sludge mixture as claimed in claim 25, wherein the hot settling tank is operated under high pressure for increasing the operating temperature range for further reducing the viscosity of the hydrocarbon thereby facilitating faster removal of free water without leading to boiling of water therein.

27. The process for treatment of the sludge mixture as claimed in claim 1, wherein the second heating vessel is preferably a multi effect evaporator preferably with a thermal vapor recompression to avoid thermal cracking of the product hydrocarbon stream.

28. The process for treatment of the sludge mixture as claimed in claim 1, wherein the second heating vessel includes a foam breaker and an entrainment separator adapted to avoid entrainment of hydrocarbons in condensate.

29. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first heating vessel includes a foam breaker and an entrainment separator adapted to avoid entrainment of hydrocarbons in the condensate.

30. The process for treatment of the sludge mixture as claimed in claim 1, wherein the second heating vessel maintain a controlled rate of heating with an optimum ratio of residual solvent to dehydrated Hydrocarbon for entire removal of bound water from the hydrocarbon.

31. The process for treatment of the sludge mixture as claimed in claim 1, wherein the bound water obtained is high quality usable water that requires minimal treatment for being used as a drinking water.

32. The process for treatment of the sludge mixture as claimed in claim 1, wherein the first and second heating vessels are provided with waste heat for reducing cost of energy in said process.

33. A process for treatment of slop oil containing water, solids, salts and hydrocarbons with or without bound water, the process for treatment of slop oil comprising steps of: a) Centrifuging the slop oil through a fourth centrifuge for obtaining the slop oil with low turbidity by connecting most oil present in a thin top layer; b) Treating the above slop oil from step a) in a high speed shear mixer by adding a solvent to form a mixture followed by centrifuging thereof in a fifth centrifuge for obtaining a water dominant hydrocarbon layer and a solvent dominant hydrocarbon layer therefrom; c) Performing BTX and Ash tests of the solvent dominant hydrocarbon layer from step b)for bound water therein followed by a heat treatment thereof in a third heating vessel and a fourth heating vessel, the third vessel håving a predefined amount of solvent added therein, the fourth vessel håving a predefined amount of free water added therein, the third heating vessel and fourth heating vessel separating a vapor phase from a liquid phase, the vapor phase håving entire remaining solvent and part of free water therein, the liquid phase håving hydrocarbons with limited solids, limited salts, free water and alum therein; d) Centrifuging the liquid phase from step c)through a sixth centrifuge operating at a predefined temperature for separating a product hydrocarbon layer from a water layer, the water layer håving limited salts, limited solids and alum therein; e) Treating the water layer from step d)through a first reverse osmosis plant for obtaining water for use and a reject stream therefrom; f) Condensing the vapor phase from step c)through a third condenser for obtaining solvent for being reused in the high speed shear mixer and water for use therefrom; g) Heating the water dominant hydrocarbon layer from step b) in a fifth heating vessel for separating vapors of solvent therefrom followed by condensing thereof in the third condenser to obtain solvent for reuse and water for use therefrom, the fifth heating vessel producing a liquid phase håving remaining water, limited hydrocarbons, salts and solids with a substantially low turbidity; h) Treating the liquid phase from step g) in a settling tank followed by addition of a predefined amount of alum therein, the settling tank forming a water dominant alum layer and a gelatinous oil bearing layer therein; i) Filtering the water dominant alum layer from step h) in a filtration unit, the filtration unit separating the water dominant alum layer into a filtrate stream and a residual stream, the filtrate stream håving water, alum and salts therein, the residual stream håving wet solids with traces of hydrocarbons, salts and alum therein; j) Treating the filtrate stream from step i) in a second reverse osmosis plant for recovering usable water therefrom; k) Mixing the residual stream from step i) with the gelatinous oil bearing layer followed by drying thereof in a first hot dryer for obtaining a viscous liquid containing hydrocarbons, alum, solids and salts; 1) Agitating the viscous liquid from step k) in an agitator cum de-oiling unit by adding a predefined solvent therein followed by treatment thereof through a seventh centrifuge for obtaining a water layer, a cake layer and a solvent layer thereby adding water therein, the water layer håving alum, salts and limited solvent therein, the cake layer håving cake of de-oiled solids with solvent, limited salts and limited alum therein; m) Treating the water layer from step 1) in a sixth heating vessel for obtaining vapors of solvent and water followed by treatment thereof through a fourth condenser for obtaining solvent for reuse and water for use or further treatment in said process; n) Treating the solvent layer from step 1) in the fourth heating vessel for recovery of solvent therefrom; and o) Treating the cake layer from step 1) in a second hot dryer for recovery of solvent through the condenser, the second hot dryer producing dried de-oiled solids håving traces of alum and salts therein.

34. The process for treatment of the slop oil as claimed in claim 33, wherein the slop oil with more than 10,000ppm hydrocarbon content is subjected to a pre-treatment comprising the steps of: a) Feeding the slop oil in a first settling tank for phase separation thereby forming a substantially unbound water-free hydrocarbon layer with or without salts, a water dominant hydrocarbon layer, and a slop oil layer håving hydrocarbon content less than 10,000 PPM; b) Treating the water dominant layer in a second settling tank by adding a predefined amount of alum therein, the second settling tank forming a substantially unbound water-free hydrocarbon layer, a gelatinous oil bearing layer and an alum containing slop oil håving hydrocarbon content less than 10,000 PPM; and c) Optionally centrifuging the gelatinous oil bearing layer from step b) in a third centrifuge by adding a predefined amount of solvent therein, the third centrifuge forming a solvent layer containing Alum along with solid coated with hydrocarbons, the solvent layer containing Alum is separated into solvent and residual hydrocarbons by azeotropic boiling with water in said process.

35. The process for treatment of the slop oil as claimed in claim 33, wherein the third heating vessel is preferably a multiple effect evaporator preferably with a thermal vapor recompression adapted to avoid thermal cracking of the product hydrocarbon.

36. The process for treatment of the slop oil as claimed in claim 33, wherein the third heating vessel has a temperature in a range of about 70°C- 150°C.

37. The process for treatment of the slop oil as claimed in claim 33, wherein the fourth heating vessel has a temperature in a range of about 90°C to 105°C.

38. The process for treatment of the slop oil as claimed in claim 33, wherein the fifth heating vessel has a temperature in a range of about 90°C to 105°C.

39. The process for treatment of the slop oil as claimed in claim 33, wherein the sixth centrifuge is a hot centrifuge that has a temperature of about 80 °C to 94°C.

40. The process for treatment of the slop oil as claimed in claim 33, wherein the sixth centrifuge is a hot settling tank that has a temperature of about 80 °C to 94 °C.

41. The process for treatment of the slop oil as claimed in claim 40, wherein the hot settling tank is operated under high pressure such that an operating temperature is further increased to reduce the viscosity of hydrocarbon for faster removal of free water without leading to boiling of water present therein.

42. The process for treatment of the slop oil as claimed in claim 33, wherein the BTX and Ash tests help assist in determination of amount of solvent to be added in said process.

43. The process for treatment of the slop oil as claimed in claim 33, wherein the solvent is selected from the group of Benzene, Toluene, Xylene and other azeotropes of water.

44. The process for treatment of the slop oil as claimed in claim 33, wherein the first hot dryer has a temperature of about 108°C.

45. The process for treatment of the slop oil as claimed in claim 33, wherein the first reverse osmosis plant removes alum, salts and solids to produce water of usable quality.

46. The process for treatment of the slop oil as claimed in claim 33, wherein the sixth heating vessel is an evaporator.

47. The process for treatment of the slop oil as claimed in claim 33, wherein the sixth heating vessel has a temperature in a range of about 90°C to 105°C.

48. The process for treatment of the slop oil as claimed in claim 33, wherein the second hot dryer has a temperature of about 200°C.

49. The process for treatment of the slop oil as claimed in claim 33, wherein the third centrifuge helps to quickly separate the solvent cum hydrocarbon layer and the gelatinous oil bearing layer from slop oil.

50. The process for treatment of the slop oil as claimed in claim 33, wherein addition of alum in the second settling tank neutralizes surface charge. It facilitates speedy separation of the hydrocarbons through flocculation and formation of the gelatinous oil bearing layer.

51. The process for treatment of the slop oil as claimed in claim 33, wherein the fourth centrifuge is a multi-pass centrifuge that reduces turbidity value of slop oil to a limiting value beyond which centrifuge is unable to produce any further value addition due to size variations of dispersed oil droplets becoming narrow, population density of dispersed oil droplets falling with increase in mean free path and a plurality of residual droplets being electrically charged along with very small density difference between phases.

52. The process for treatment of the slop oil as claimed in claim 51, wherein said lacuna of the fourth centrifuge gets magnified when starting turbidity value of the slop oil is very high.

53. The process for treatment of the slop oil as claimed in claim 51, wherein the solvent is added through the high shear mixer when the fourth centrifuge reaches its limiting value.

54. The process for treatment of the slop oil as claimed in claim 51, wherein addition of solvent enhances the operating range of the centrifuge by bringing in large variation in droplet size and also by increasing the population density of droplets along with increasing density difference between oil and water.

55. The process for treatment of the slop oil as claimed in claim 51, wherein the fourth centrifuge again reaches a limiting value after addition of the solvent and at that point the residual solvent present therein is boiled out with free water in a temperature range of about 90 °C to 99 °C.

56. The process for treatment of the slop oil as claimed in claim 33, wherein addition of alum in third settling tank when the slop oil is håving turbidity below 90 NTU to electrically discharge finest droplets of the hydrocarbons and flocculate them thereby reducing turbidity by 90 %- 99 %.

57. The process for treatment of the slop oil as claimed in claim 33, wherein settling with addition of alum is a slow process by itself but it can be speeded up by applying heat such that effectiveness of alum treatment is dependent on temperature and time.

58. The process for treatment of the slop oil as claimed in claim 33, wherein the filtration unit brings down the turbidity value of the slop oil below 1 NTU.

59. The process for treatment of the slop oil as claimed in claim 33, wherein the filtration unit has an effectiveness that substantially depends on pore size of filtering media of the filtration unit and nature of hydrocarbons present in the slop oil.

60. A process for treatment of a sludge mixture comprising of a centrifuge, the process for treatment comprising the steps of: Centrifuging the sludge containing hydrocarbons, bound and unbound water, salts and solids in a centrifuge to break the binding between the components present by increasing residence time of the sludge in the centrifuge thereby forming a viscous hydrocarbon layer with bound water, salts and solids, a free flowing hydrocarbons layer with limited salts and solids and a free water layer with limited solids and salts, the centrifuge repositioning the viscous hydrocarbon layer from a back side to a middle side therein by slowly increasing revolutions per minutes thereof, the centrifuge slowly decreasing an angle between a vertical axis of a container and a horizontal plane thereof thereby gradually reducing but not allowing said angle to become 0°.

61. The process for treatment as claimed in claim 60, wherein the quantity of sludge mixture with bound water is reduced thereby saving further processing cost and time.

62. The process for treatment as claimed in claim 60, wherein the centrifuge itself gives a large amount of marketable product hydrocarbons, namely free flowing hydrocarbons.

63. A process for treatment of sludge mixture with combined effect of centrifuge and solvent, the sludge mixture containing bound and unbound water, salts and solids therein, the process for treatment comprising the steps of: a) Adding a predefined amount of solvent in the viscous hydrocarbon emulsion, followed by mixing thereof, the solvent reducing the viscosity of the viscous hydrocarbon layer. b) Centrifuging the solvent dominant viscous hydrocarbon layer from step a) in the centrifuge to obtain a large layer of solvent and hydrocarbon, a layer containing hydrocarbons and bound water and a free water layer, the centrifuge håving an extended residence time for getting less of sludge with bound water therein; c) Treating the large layer of solvent and hydrocarbon in step b) for recovering solvent by boiling through free water in a temperature range of 90 °C to 99 °C at an atmospheric pressure.

64. The process for treatment as claimed in claim 63, wherein the mass of sludge mixture with bound water is reduced thereby saving further processing cost and time.

65. The process for treatment as claimed in claim 63, wherein this centrifuge gives further amount of marketable product hydrocarbons, namely free flowing hydrocarbons.