WO1995021902A1 - Removal of contaminants from oil - Google Patents

Abstract

A process comprising combining the heavy oil still residue and propane in conduits (146) and pumping mixture through static mixer (300). The mixture is then passed through heat exchanger (301) and flows via (302) to an extraction vessel (304). The residum/oil mixture then leaves via outlet (308) and asphalt pump (309).

Description

REMOVAL OF CONTAMINANTS FROM OIL BACKGROUND

Field of Invention This invention is concerned with the removal of contaminants from crude or processed mineral oils and in particular, is concerned with the removal of contaminants from used motor oils. The invention is concerned with a method and apparatus for removal of contaminants from mineral oils.

Prior Art A large number of processes for removal of contaminants from mineral oils and waste lubricating oils are known in the art. Indeed, this plethora of prior art references is illustrative of continuing endeavours to find a cost effective method of removal of contaminants from oils.

Undesirable contaminants in crude oils typically comprise a complex mixture of high molecular weight hydrocarbons (including polycylics) known as asphaltenes. Asphaltenes are recovered as a viscous residuum in the vacuum distillation of petroleum and are known to interfere with the efficiency of the distillation process. Prior art processes for the removal or reduction of asphaltenes by solvent extraction of crude oil with a liquid solvent such as propane or butane are well known.

Used motor oils contain a variety of undesirable contaminants such as carbon, some asphaltenic compounds and an additive "package" comprising organo- metallic compounds in the form of rust inhibitors, antioxidants, antiwear agents, a detergent-dispersant and antifoaming agents as well as synthetic polymeric pour-point depressants and viscosity index improvers. Soluble and insoluble metal values in used motor oils include lead (from gasoline), iron (from engine wear) and varying amounts of calcium, phosphorous, sulfur, zinc, sodium and magnesium from the additive "package" in addition to nitrogen containing organic compounds.

Removal of additive "packages" from used motor oil is very difficult as the organo-metallic and polymeric compounds are soluble in solvents used for solvent extraction reclaiming processes and distil at similar temperatures to the lubricant base oil.

In the recovery of bunker oil slops from ships bilges, water and stable oil/water emulsions are contaminants which are not readily removed on an economical basis. Accordingly, bunker oil slops are not employed as a refinery feed stock due to the risk of refinery operating problems and traditional propane extraction is not economical in view of the relatively low volumes for processing.

United States Patent No. 2196989 describes a process for separating asphaltic compounds from crude oil to produce a lubricating oil. In this process the crude oil is mixed with a light hydrocarbon solvent such as liquid propane or butane and an inert gas such as methane, ethane, hydrogen, carbon dioxide, nitrogen or ammonia, the gases acting as a precipitant for oil materials dissolved in the liquid solvent. Asphaltic oil is contacted, at elevated temperature and pressure with a liquid solution of the oil and propane whereupon a large proportion of the oil dissolves in the liquid propane solution and small droplets of undissolved asphaltic impurities fall to the bottom of the reaction vessel. A gas, soluble in liquid propane but insoluble in the mineral oil is introduced into the oil/propane liquid solution near the top of the vessel under elevated pressure. The precipitant gas is soluble in and dilutes the propane solution, thereby decreasing the solubility of the resinous asphaltic impurities and finally precipitates the asphaltenes and a substantial proportion of the oil from solution.

The precipitation of the oily impurities from the propane solution by precipitant gas is said to be effected by the principle of difference in solubilities of the various components in one another. A process for de-asphalting of residues from the vacuum distillation of petroleum is described in United States Patent No. 3870625. This process may also be applied to reclaiming of used lubricating oils.

The used oil or distillation residue is injected under pressure into liquid propane in a pulsed manner to facilitate dispersion of the oil material in the solvent as fine droplets. The pulsed oil feedstock flows countercurrent to the liquid propane which dissolves the fraction of oil capable of being used as a lubricant and allows precipitation of the insoluble materials. The application of mechanical vibrations to the apparatus is said to improve the output of the apparatus.

United States Patent No. 4265734 concerns improvements to the process of aforesaid Patent No. 3870625. As a preliminary step, polluted oil is injected into reservoirs containing liquid propane to form a mixture in the ratio of volume of polluted oil to liquid propane of from 0.25:5 to 1:5. This mixture is allowed to stand for about an hour to permit the major part of the impurities in the polluted oil to precipitate to the bottom of the reservoir. The oil/propane solution is then withdrawn and treated as described in earlier Patent No. 3870625.

United States Patent No. 5286380 to Mellen, a co- inventor of the subject patent application, deals with removal of contaminants from used motor. In the '380 patent, used motor oil is fed into an empty reaction vessel and a liquid aliphatic solvent such as liquid propane is allowed to enter the reaction vessel at the bottom thereof to mix with the oil in the ratio of one part by volume of oil to ten parts by volume of solvent whereupon the contaminants precipitate. The oil/solvent solution is then percolated down through a bed of activated charcoal to remove lead and other metal contaminants. A glass or plastics reaction vessel is preferred.

Traditional methods of propane extraction of asphaltenes from crude oil stocks rely on a large product upgrade, such as the production of light stock, to justify high capital costs and high operating overheads.

Processes employing propane as a solvent in both crude oil asphaltene extraction and reprocessing of used motor oils must use propane to oil ratios of from between 10:1 and 15:1 in order to reduce the solution viscosity and specific gravity sufficiently to permit suspended microscopic solids to settle under the influence of gravitational forces. This requirement for high propane to oil ratios necessitates very high energy requirements for propane recovery and large settling vessels to permit sufficient residence times for the settling of very fine particles.

Another method for reprocessing of used motor oils which is currently employed in the United States is a vacuum distillation process followed by hydrotreating.

In this process, the waste oil is heated to about

150°C to remove any water as well as light hydrocarbons. The dewatered oil, containing the additive package, is then heated to about 260°C to remove any diesel fractions.

The oil/additive package mixture is then heated to about 370°C in a distillation column operating at about 5mm Hg absolute to separate the base oil from the additive package and the base oil distillate is then hydrotreated to improve colour and odour. The hydrotreating step also removes a proportion of a residual polycyclic aromatics.

While generally effective for its purpose, the above described thin film vacuum distillation process nevertheless suffers from a number of disadvantages.

The main problem with such distillation processes is that the components of the additive package are not removed until the last distillation step. At this stage the oil (and additives) have been heated to over 370°C at which temperatures, thermal cracking of the polymeric compounds and thermal decomposition of the organo-metallic compounds occurs resulting in severe coking and corrosion in the distillation column and ancillary plant. Coking and corrosion of the plant not only interferes with throughput efficiencies but also results in a poorer quality lube oil distillate than otherwise might have been the case.

Although it is possible to pretreat the waste oil with sodium hydroxide to reduce coking and corrosion in the downstream region of the plant, this requires expensive upgrading of the metallurgy in the upstream region of the plant to reduce corrosion in this region.

Even in the intermediate diesel distillation column, plant maintenance is extremely costly due to the need to replace the column packing every six to eight months.

Generally speaking, thin film evaporators of the type employed in the process described above are expensive to construct and operate on a per unit throughput capacity. Moreover, in this process, about 2% of the light oil (diesel) fraction is lost in the water removal stage and about 3% of the available base oil is lost in final distillation stage due to retention in the asphaltic still bottoms.

United States Patents 4624763, 4624764, 4661226, 4634510, 4627901, 4622119 and 4622118 all deal with the removal of waxes from lubricating oil by the induction of a high voltage charge into oil/solvent mixes to obtain nucleation of wax particles before precipitation. Australian Patent No. 605288 describes a process for extraction of oil from stable oil/water emulsions by adding a liquefied hydrocarbon solvent to the emulsion, separating portion of the oil which, on standing forms an oil solvent phase, and then reducing the pressure of the residual two phase system to allow the pressurised liquid solvent to vaporise whereupon the emulsion splits into oil and water phases.

Brief Summary and Objects of the Invention

It is an aim of the present invention to provide a novel process and apparatus which overcome or substantially alleviate at least some of the problems associated with prior art methods and/or apparatus for removal of contaminants from oil.

According to one aspect of the invention there is provided a method of removal of contaminants from oil, the method comprising the steps of:- forming a solution of contaminated oil in a liquid aliphatic solvent in the presence of a flocculation enhancing reagent in a first pressure vessel; introducing in a lower region of said first pressure vessel a gas in the form of fine bubbles whereby said solution is agitated by the bubbles rising through the solution and contaminants are caused to separate from solution by a flocculation reaction; separating flocculated contaminants from the liquid solution; and, separating the solvent from the solution to obtain an oil substantially free of contaminants.

Suitably the solvent comprises a Cj to C₇ alkane. Preferably the solvent comprises liquid propane or butane or a mixture thereof.

The flocculation enhancing reagent may be selected from water and/or an electrolyte solution.

Suitably at least 2% v/v of water is present in the solution of oil and solvent during the flocculation reaction.

Preferably at least 3% v/v of water is present in the oil and solvent solution of oil and solvent during the flocculation reaction. Most preferably water is present in the oil and solvent solution at a concentration in the range of from about 3% to 6% v/v.

Alternatively or in addition to water as a flocculation enhancing reagent, an electrolyte is employed as a flocculation reagent.

Suitably the electrolyte comprises a strong acid or alkali.

The electrolyte may be selected from H₂S0₄, HCl, NaOH or KOH. If required the flocculation reaction may be carried out with an electrically conductive member in physical contact with the oil and solvent solution.

The gas may comprise a polar or non polar gas.

Suitably the gas is selected from Co₂, N₂ or a C, to C₄ alkane.

Preferably the gas comprises propane or butane or a mixture thereof.

Most preferably the gas comprises propane when the aliphatic solvent is propane. The flocculation reaction is carried out at a temperature of between 15°C and 45°C.

Suitably the flocculation reaction is carried out at a temperature of between 15°C and 30°C.

Most preferably the flocculation reaction is carried out at a temperature between 18°C and 25°.

The method of removal of contaminants from oil may comprise the further step of: transferring, from the first pressure vessel to a second pressure vessel, an oil and solvent solution from which contaminants have been flocculated; allowing any residual contaminants to settle from the oil and solvent solution; transferring from the second pressure vessel to a solvent stripping vessel an oil and solvent solution substantially free of contaminants; and stripping solvent from the oil and solvent solution to obtain a substantially contaminant free oil fraction.

If required the substantially contaminant free oil fraction may be further purified by a distillation process. Preferably the distillation process is carried out under reduced pressure.

Before distillation, the substantially contaminant free oil fraction may be subjected to a stripping process to remove any residual solvent and any light petroleum fractions therefrom.

If required, contaminant residues from the first and/or second pressure vessels are subjected to a stripping process to remove water and any residual solvent. Preferably, contaminant residues from which water and any residual solvent have been removed are mixed with a hot oil to obtain a flowable asphalt extender.

Most preferably the hot oil comprises a distillation residue from the distillation process. The contaminated oil may comprise automotive drain oil.

Alternatively the contaminated oil may comprise crude petroleum oil.

The contaminated oil may comprise residues from a petroleum cracking and/or distillation process.

Alternatively the contaminated oil may comprise bunker oil slops from ship's bilges. As a further alternative the contaminated oil may comprise oil/water mixtures and or oil/water emulsions obtained in petroleum drilling operations.

According to another aspect of the invention there is provided a method of refining crude oils to obtain a bright oil product, the method comprising removal of contaminants from a crude oil feedstock according to a first aspect of the invention and subjecting the substantially contaminant free oil feedstock to a subsequent refining process.

According to a further aspect of the invention there is provided a method of beneficiating distillation residues in a petroleum refining process, the method comprising the steps of treating a distillation residue in accordance with a first aspect of the invention and separating lighter fractions from a contaminated residue formed thereby.

In yet another aspect of the invention there is provided a method of beneficiating water containing oil residues from petroleum drilling operations, the method comprising treatment of the water containing residues according to the first aspect of the invention to extract substantially contaminant free oil fractions therefrom. In still another aspect of the invention there is provided a method of beneficiating bunker oil slops comprising the treatment of bunker oil slops in accordance with the method according to the first aspect of the invention to extract substantially contaminant free fuel oil fractions therefrom.

Preferably, in the beneficiation of water containing oil residues from petroleum drilling operations and/or bunker oil slops, the water content of the oil containing residue to be treated is first subjected to a water extraction process to reduce, the water content of material to be treated to less than 10%. According to a second aspect of the invention there is provided an apparatus for removal of contaminants from oil, said apparatus comprising:- a first pressure vessel in fluid communication with a source of contaminated oil and a solvent and, selectively, a source of flocculation enhancing reagent comprising water and/or an electrolyte; a source of pressurised gas selectively introducible via an inlet port adjacent a lower portion of said first pressure vessel to disperse fine gas bubbles through an oil/solvent/flocculation reagent contained therein; an outlet port in fluid communication with said inlet port to circulate gas introduced into said first pressure vessel; a decanting port to selectively remove an oil/solvent solution substantially free of contaminants from said first pressure vessel; and a contaminant outlet port adjacent a lower region of said first pressure vessel to selectively remove flocculated contaminants settled in said lower region.

Suitably said apparatus includes a second pressure vessel to accumulate a decanted substantially contaminant free oil solvent solution from said first pressure vessel, said second pressure vessel including an outlet port for substantially continuous withdrawal of a substantially contaminant free oil/solvent solution therefrom and an outlet port in a lower region of said second pressure vessel for removal of accumulated flocculated contaminants settling therein.

The apparatus may include a solvent stripping vessel to strip solvent from said substantially contaminant free oil/solvent solution extracted from said first and/or second pressure vessel, the solvent so extracted being returned to said source of solvent.

Suitably said apparatus includes a further stripping vessel to remove from a solvent stripped material delivered from said stripping vessel any residual solvent and light fuel oil fractions.

If required said apparatus may include a distillation column to remove a base oil product from said solvent stripped and light fuel oil stripped fractions delivered from said further stripping vessel.

Preferably said apparatus includes a residuum collection vessel to collect contaminants from said first and for said second pressure vessels.

Suitably said residuum collection vessel is adapted to separate water and/or residual solvent from residuum so collected.

If required said apparatus may further include a residuum treatment vessel including heating means to provide a flowable residuum material.

Suitably said residuum treatment vessel includes a mixing apparatus to mix an oil with said residuum to provide a flowable product. Preferably said apparatus is in fluid communication with said distillation column to provide an oil distillation residue for mixing with said residuum.

According to yet a further aspect of the invention there is provided an apparatus for production of bright oil from crude oil, said apparatus comprising a decontamination apparatus according to a second aspect of the invention for pretreatment of crude oils upstream of a conventional crude oil processing apparatus.

According to another aspect of the invention there is provided an apparatus for processing of distillation residues in a conventional petroleum distillation apparatus said apparatus including an apparatus according to a second aspect of the invention to extract valuable petroleum fractions from petroleum distillation residues. The invention provides yet another apparatus for the beneficiation of water containing crude oils obtained from petroleum drilling operations.

Still further the invention provides an apparatus for beneficiation of bunker oil slops obtained from ship's bilges.

If required, the invention in another aspect provides an apparatus for treatment of oil containing residues from commercial and public utilities for oil separation from waste and/or storm water sources.

The present invention overcomes or substantially alleviates the aforementioned prior art problems by further providing a novel apparatus for removing contaminants such as asphalts, additive packages and other contaminants from drain oils; asphaltenes from crude oils; asphaltenes, water and other contaminants from bunker oil slops and the like.

In one embodiment, oil from an oil storage tank is pumped by a pump into a solvent mix tank. This oil is mixed with an aliphatic solvent such as methane, ethane, propane, butane, pentane, hexane, heptane or the like coming from a solvent storage tank via another pump and an appropriate quantity of a flocculation enhancing reagent is also added. Advantageously, the solvent, reagent and oil are mixed just prior to entering the solvent mix tank to form an oil, reagent and solvent mixture at ambient or an elevated temperature between 25°C and about 40°C. Thereafter, gas, preferably propane, is dispersed into the bottom of the solvent mix tank thus agitating the mixture. This agitation is allowed to proceed for a specified period of time after which the gas is shut off and the mixture is allowed to separate via gravity. The oil/propane solution is then transferred to a second tank using the pressure differential between the two vessels as the driving force. Water, asphalt residuum and some solvent are transferred from the solvent mix tank into a residuum and water separation tank.

When all of the material, both the oil/solvent/reagent solution and the water and residuum, have been transferred from the solvent mix tank, it is once again ready to receive another batch of, say, drain oil and propane solvent. The oil/solvent solution in the solution feed tank allows any residuum that may not have separated in the solvent mix tank to separate out but primarily the solution feed tank is a holding tank to allow a continuous feed of oil/solvent solution into the solvent oil recovery area, explained hereafter, so that a continuous run is accomplished. The oil/solvent solution is pumped via a stripper charge pump which also increases the pressure up to the solvent stripper operating pressure. Any residuum settling out in the solution feed tank is transferred to an asphalt mix tank. This transfer is accomplished by the pressure differential between the two vessels.

The residuum and water separator is designed to separate any oil/solvent solution that is transferred from the bottom of the solvent mix tank from the residuum and also from the water. Thus, this is a three phase (oil, water and residuum) separator. The interface of each phase is determined by pumping from a specific level via a pump through a gage glass with a viewport by detecting the difference in the colour between the water and the residuum or by any other suitable detection means. Once the level is detected, then the water is taken off and disposed of, or if required, portion of this water may be employed as a flocculation enhancing reagent. The residuum which is a solid with some propane and water trapped in the solid is then transferred to the asphalt mix tank where it is heated and mixed with the heavy oil from the bottom of the vacuum distillation column.

The solvent stripper recovers in excess of 95 percent of all of the propane solvent that was injected into the solvent mix tank. The remainder of the propane solvent will be recovered in the distillation preflash or light petroleum flash tank. The oil/solvent solution from the solution feed tank enters the solvent stripper at an increased pressure because of the vane pump which facilitates the transfer. The oil/solvent solution is then introduced into a packed column in the solvent stripper, wherein the oil and propane mixture flows across a packed bed where propane vapours from the reboiler portion of the solvent stripper strip out the propane solvent from the oil. The propane then leaves the top portion of the column and is subsequently condensed by a condenser. From the condenser this propane solvent is reintroduced into the solvent storage tank for future reuse as needed. The oil falls to the bottom of the solvent stripper into the reboiler. This reboiler uses a hot oil stream from the bottom of the distillation column, heat being provided by the furnace, and the hot oil stream is pumped through the reboiler heating the mixture of oil to approximately 260°C.

This hot oil is then transferred to the light petroleum flash tank operating at a much lower pressure. In the light petroleum flash tank the lower pressure and high temperature allows light petroleum fractions and whatever propane might remain in the oil to vaporise.

The light petroleum fractions and propane solvent that vaporises goes into an overhead condenser where all of the light petroleum fraction condensed. The light petroleum fraction and propane mixture then goes to a light petroleum separation drum from where the light petroleum is pumped to the light petroleum storage facility via a pump. The propane vapour goes to a two stage compressor with an intercooler where the propane solvent is compressed and sent back to the solvent storage tank. The oil that did not flash in the light petroleum flash tank is transferred to the vacuum distillation column. By reducing the pressure on the oil, the diesel and lubrication oil that remain in the liquid state are vaporised and go into the upper part of the distillation column. The liquid that does not vaporise at that time, falls to the bottom of the tower where it is heated to a temperature of approximately 350°C where further vaporisation happens causing more of the oil to vaporise. The oil that does not vaporise is transferred via a pump into the hot oil loop where it provides the heat for both the solvent stripper as described earlier and the asphalt mix tank. When the oil has been cooled off by rendering these services in the hot oil loop, it is returned to the furnace where it is heated up to approximately 350°C and returned back to the bottom of the distillation column.

A certain amount of heavy oil product that does not vaporise in the distillation column is pumped to the asphalt mix tank. It is this hot oil that dissolves the residuum from the solvent mix tank and solution feed tank.

The oil that vaporises in the distillation column goes through the column and proceeds up to the section of the column where it is condensed and drawn off by a pump into the oil storage. A light petroleum fraction which is still vaporising rises to the top packed section of the column where it is condensed and drawn off by a pump. Any noncondensibles that remain at this time are pumped via a sliding vane vacuum pump to a furnace where those vapours are burned.

These and other objects and features of the present invention will be apparent from the detailed description and accompanying drawings.

Brief Description of the Drawings In order that the various aspects of the invention may be more fully understood and put into practical effect, reference is made to preferred embodiments illustrated in the accompanying drawings in which:- FIG 1 is a schematic view of a settlement reaction vessel.

FIG 2 is a flow diagram representing an apparatus for removal of contaminants from oil in accordance with both method and apparatus aspects of the invention.

FIG 3 is an enlarged schematic view of the asphalt extraction system illustrated in FIG 2.

Detailed Description of the Illustrated Embodiments FIG 1 illustrates a laboratory scale reaction vessel employed in the generation of experimental data discussed hereinafter.

In FIG 1 the vessel 201 comprises a clear cylindrical acrylic plastics wall 202 with a top closure member 203 and a generally frusto-conical bottom closure member 204. Removably located within vessel 201 is an expanded mild steel mesh tube 205, the purpose of which will be explained later.

At the base of vessel 200 is an asphalt valve 206 to remove asphaltic residuum 207 which collects in this region and a further valve 208 is provided in a conduit 209 connected to a source of waste oil and other additives (not shown) .

A two way valve 209 is connected to conduit 210 providing a source (not shown) of liquid propane or a pressurised gas such as C0₂ or N₂. Valve 209 is also connected to a gas recirculation system comprising conduit 211 in fluid communication with the upper region of vessel 1, an isolating valve 212, a gas compressor 213 and a heat exchanger 214. Gas is dispersed in the vessel 201 via a sparging manifold 217 having a plurality of nozzles 218 to disperse the gas as fine bubbles.

A take off conduit 215 with isolating valve 21.6 is connected to a solvent stripper/recovery system

(not shown) . The process according to a preferred aspect of the invention involves mixing contaminated oil, containing water and/or an electrolyte, with liquid propane in the ratio of between 1:3 to 1:6 and then sparging the mixture with fine bubbles of propane for a period of 10 to 20 minutes at ambient temperature and thereafter allowing the mixture to settle for about 10 to 20 minutes.

The mixture separates into three distinct layers, a clear oil/propane layer, a water layer and a residue layer. Each of these layers are collected and propane is removed from the clear oil fraction.

Examples

The reactor of FIG 1 was charged with 1000 ml of oil and mixed with liquid propane in the ratio 1:6. The propane/oil mix was agitated by pumping propane vapour in fine bubbles through the liquid mixture for a period of 10 minutes.

The sparging resulted in a high flow rate of gas bubbles having a diameter of between 1 and 3mm which provide a relatively gentle but turbulent mixing action. After agitation for 10 minutes, the mixture was allowed to settle and the rate of settling was measured.

When the suspended solids had completely settled, the clear oil/propane mixture layer was removed and the propane was extracted therefrom under reduced pressure. The remaining residue was removed and entrained propane was allowed to boil off at atmospheric pressure.

The oil used in the tests was automotive drain oil which had an initial water content of 3.8%. This oil was dehydrated by heating up to 140°C to obtain an oil with a water content of less than 0.2% and a specific gravity of 0.887 kg/m³.

The clarity of the oil removed was measured by diluting the oil in hexane in a 1:10 ratio of oil to solvent and then measuring with a colour meter.

The residues from the tests were weighed and visually compared with respect to viscosity and flow characteristics and the water contents of the residue was determined by standard ASTM methods.

All liquid additions to the oil such as H₂0, 97% H₂S0₄, 35% HCl and red water were on a volume to volume basis whereas the additions of 45% KOH, CH₃C00H, clay and sodium hexametaphosphate were on a weight to volume basis.

In all tests carried out the floe formation appeared to occur during agitation with the stream of gas bubbles. There may be some continued floe growth after gas sparging is ceased at which time gentle mixing of the liquid mixture/floc suspension occurs due to entrained gas bubbles moving through the liquid.

The following tables illustrate the effects of varying concentrations of water in the oil/propane mixture and the effects of electrolytes and other chemicals in the settling properties of the treated oil and the residue.

Table I

Effect of Water Content in Dehydrated Oil

(Metal Screen Present)

CONTENT SETTLING RATE OIL COLOUR RESIDUE (gm) H₂0 in H,0 (%) (MINUTES) residue (%) <0.2 Very slow 8.0 No solid N/A 14-18 residue 25mm oil/sludge

1.0 Slow 7.5 No solid N/A 8-9 residue 12mm oil/sludge

2.0 Slow 7.0 Traces of N/A 8-9 residue 12mm oil/sludge

3.0 Medium 7.0 40-51 40 5-6

5.0 Medium 7.0 45-66 47 5-6

20.0 Medium 7.0 7200 64 5-6

TABLE IA

EFFECT OF WATER CONTENT IN DEHYDRATED OIL (METAL SCREEN REMOVED)

H₂0 SETTLING OIL COLOUR RESIDUE (gm) H₂0 IN

CONTENT RATE RESIDUE

(%) (MIN) ⁽%⁾

5.0 V.V. Slow 7.5 No Solid Residue N/A >30 50 mm oil/Sludge

TABLE II

EFFECT OF KOH IN THE DEHYDRATED OIL

(METAL SCREEN PRESENT)

KOH SETTLING RATE OIL COLOUR RESIDUE H₂0 IN RESIDUE (%) (MIN) (gm) (%)

0.2 V. Fast 5.5 28 12 2-3 Viscous

0.5 V. Fast 4.5 36 16 2-3 Viscous

0.5 Fast 5.5 39 30 3-4 Sticky TABLE I IA

EFFECT OF KOH IN THE DEHYDRATED OIL

(METAL SCREEN REMOVED)

KOH (%) SETTLING RATE OIL COLOUR RESIDUE H₂0 RESIDUE (MIN) (gm) (%)

0.5 V. Fast 7.5 65 12 2-3 Viscous

TABLE III EFFECT OF ACIDS IN THE DEHYDRATED OIL

CONCENTRATION SETTLING OIL RESIDUE H₂0 IN (%) RATE (MIN) COLOUR (gm) RESIDUE

(%)

0.2 H₂S0₄ (98%) V. Fast 2-3 4.5 21 6 V.V. Viscous

0.5 H₂S0₄ (98%) Fast 3-4 4.5 30 9 V.V. Viscous

0.5 HC1 (35%) Medium 8-10 4.0 39 21 V.Viscous

0.5 CH_jCOOH Slow 10-12 6.5 29 3.5 Sticky

TABLE IV EFFECT OF VARIOUS CHEMICALS IN THE DEHYDRATED OIL

CONCENTRATION SETTLING OIL RESIDUE H₂0 in

RATE COLOUR (gm) RESIDUE (MIN) (%)

1% Calgon + 1%H₂θ Fast 5.5 120 Sticky 30 3-4

0.5% V. Slow 34 Sticky 27

Hexametaphosphate 20-25

+ 2% H₂0

5% red water Slow 7.5 47 Sticky - 8-10

5% CH_jOH V. Slow 10 No Solid N/A 10-25 Residue

5% Clay Slow 7.5 65* 13 8-10

Some clay settled first followed by a mixture of clay and residue as soft lumps.

The results show that a number of factors contribute to the formation of large particles which are capable of settling quickly in the propane/oil mixture. Also it appears that there may be a number of competing mechanisms which are responsible for the formation of the large flocculant particles.

Without wishing to be bound by any particular hypothesis as to the nature of the various competing mechanisms, the following discussion is an attempt to explain the basis of the various phenoma observed. The stability of complex mixtures/dispersions of surface active materials may, in addition to van der Waals attractive forces and electrical double layer repulsive forces, be influenced by a variety of additional factors involving desorption energy, entropic and bridging effects.

Given that there is no noticeable coagulation or precipitation of the contaminants when drain oil is simply mixed with liquid propane in the ratio of from about 1:3 to 1:4 volume/volume of drain oil to liquid propane, the introduction of the gas bubbles, particularly in the presence of water or an electrolyte, gives rise to circumstances which destabilise the solution/dispersion. This is in stark contrast to prior art propane treatment methods which require oil/liquid propane ratios in the range 1:10 to 1:15 to reduce the viscosity and specific gravity of the solution to permit precipitation of fine particulate solids and insoluble oils with prolonged settling periods.

In the process according to the invention, there is no appreciable change in the oil/liquid propane ratio with the introduction of propane gas bubbles as the propane gas is withdrawn from the upper region of the reaction vessel and recirculated.

Trials with other gases such as Co₂ and N₂ have shown that although nowhere near as effective as propane, agitation of the oil/liquid propane mixture, in the presence of water and/or an electrolyte, with these gases will also initiate a coagulation or flocculation reaction. Accordingly, the dispersion of fine gas bubbles through the oil/propane mixture may involve the generation of a triboelectric charge on the surface of the bubbles in the form of an electrical double layer.

As drain oil is a mixture of ionic species such as organo-metallic compounds and non-ionic macro- molecular species such as synthetic polymeric viscosity index modifiers as well as polar and non- polar molecular species, it is believed that drain oil behaves as a mixture of lyophilic and lyophobic colloidal systems. This is borne out by the inexplicable contribution of the metal screen to solids formation and the contribution of strong electrolytes to the process. On balance, the system behaves like a lyophobic colloid system in which the addition of a relatively small amount of electrolyte causes flocculation. Although, strictly speaking, water is not an electrolyte, it is believed that contaminated oils contain water soluble impurities which behave as electrolytes.

By examining the behaviour of the coagulation/flocculation reaction, the settling rate of the solids and the nature of the solids obtained with the various chemicals added to dehydrated oil, some insight into the complexity of the process may be obtained. WATER In the absence of any other chemical, water plays a vital role in the formation of large residue particles. When the oil is dry (<0.2%) the insoluble residue that is formed is very small in size, does not flocculate and settles very slowly. The settled residue does not form a viscous material that stays in the bottom of the column, but remains concentrated in the oil/propane mix and tends to redissolve in the oil when the propane is removed.

With a propane to oil ratio of 6:1 at least 3% water is required in the oil before a significant change in the settling rate is achieved. At this concentration larger residue particles are formed and the residue can be easily separated from the oil/propane mixture. The residue is viscous, and tends to have a tar like structure. No viscosity measurements were undertaken. The rate of settling of the residue remains approximately constant with increasing water contents above 3%, but the quantity of residue increases with increasing water content. This is mainly due to an increase in the water bound up in the residue.

For the formation of these larger particles sufficient water in the form of droplets needs to be available so that the precipitated insolubles can be attached to them. The minimum water content found in this work is probably due to the solubility of water in the propane-oil mixture and sufficient nuclei are not available until the water content of the oil reached about 3.0%. Although triboelectrically charged gas bubbles may provide nuclei in their own right, it is believed that a charge transfer may occur between the gas bubbles and the water particles which would explain the improved flocculation rates with water/electrolyte nuclei.

However, without a metal mesh in the reactor an oil containing 5.0% water did not form the large particles and tended to settle in a manner similar to dry oil. The particle size was small, it . was very slow in settling and did not produce a residue that was readily separated from the oil-propane mixture.

It is believed that the metal screen provides an electrically conductive matrix in an otherwise non- conductive medium which assists in transference of the electric charge from the gas bubbles to the aqueous electrolyte or ionic and polar molecular species in the mixture. Since the insoluble residue produced in the dry oil did not produce a fast settling residue the presence of water and metal mesh whether iron or copper, are necessary to form the large particles. The most probable mechanism is that the turbulent mixing created by the propane sparge creates a triboelectric charge on the water droplets that enables the precipitated residue to be attracted and attached to it or that the gas bubbles are charged and transfer this charge to the water droplets. The mixing also provides greater droplet-particle contact and this would assist in overcoming any double layer repulsion. The residue will contain significant ionic charges due to the presence of metal organics but these alone do not explain the need for a metal surface for the mixture to contact.

The metal mesh remains inert during the process and there are no visible signs of it reacting or eroding. The pilot plant described with reference to FIGS 2 and 3 herein comprises mild steel reaction vessels and operates in the same way as the laboratory test with the metal mesh present. ALKALIS

In the absence of water a 45% potassium hydroxide solution added to the dry oil created large, fast settling residues. Compared with the oil produced in the process using water above, the colour was significantly improved, the settling was much faster and the viscosity of the settled residue increased significantly.

The presence of 3% water with the 0.5% potassium hydroxide slightly reduced the settling rate (but better the 3% water only) and made the residue less viscous. The amount of water in the residue appears to have been reduced by the presence of potassium hydroxide.

The formation of a fast settling residue was independent of the presence of a metal mesh when KOH was used. This shows that a different mechanism to that for water alone is affecting the formation of the large residue particles. The increase in viscosity of the residue indicates greater bonding and cross- linking may be occurring.

The strong alkali is reacting with the residue so that when the particles come in contact with each other due to the strong mixing they readily attach to one another. The exact reaction is not known but both potassium and sodium hydroxide work equally well whereas ammonium and calcium hydroxide do not.

The test without the screen produced larger amounts of residue and the colour of the oil was darker.

ACIDS

In the absence of water a 0.2% or 0.5% sulphuric acid solution created a large settling residue. The colour of the oil was equal to that of 0.5% KOH. The residue, however, was by far the most viscous indicating considerable cross-linking. The presence of water in the oil reduced the severity of the reaction.

Similarly when 0.5% hydrochloric acid was used the settling rate was moderate but faster than when only water was present. However, the colour of the oil was the best of all the tests. The water content for this work was 2% due to the acid being a 35% solution. From the previous work this would reduce the settling rate.

A weak acid, such as acetic acid, produced a slow settling residue that was difficult to separate from the oil-propane mixture.

The strong acids tend to act in a similar manner to strong alkalis by reacting with the residue to form a material that attaches readily to other residue particles or to create a cross-linking reaction between the particles. The acids and alkalis may also enhance the amount of insoluble material by precipitating metal hydroxides and sulphates.

For this type of system the sparging by propane or another gas may not be crucial and similar results could be achieved by mechanical mixing. DISPERSANT

Calgon, a commercial additive for water treatment, and sodium hexametaphosphate showed different effects. The calgon in high concentration (1%) with 5% water produced a rapid settling residue and an oil of moderate colour. The sodium hexametaphosphate in 2% water produced a slow settling residue which, unlike the 2% water only test, could be separated from the propane-oil mixture.

Both of these compounds act as particle dispersant in an aqueous system and they were tested in an attempt to keep the water from being tied up in the residue. This was only partially successful and the presence of highly charged ions appears to have enhanced the growth of the residue particles. This may be due to the precipitation of metal phosphates. OTHER CHEMICALS

The addition of clay or red water did not significantly change the particle size or the settling rate of the residue. The clay improved the settling characteristics by adsorbing some of the residue onto its surface. The residue was drier and had poor flow characteristics.

Whether used on automotive drain oils, raw crude oil, petroleum distillation residues, bunker oil slops or the like, the process according to the invention has been found to remove up to 95% of contaminants, including water, at the initial flocculation stage. In the subsequent stripping and/or distillation stages the light fuel fraction and the base oil fractions are found to be substantially free of contaminants. FIG 2 illustrates schematically a commercial apparatus for the removal of contaminants from oils.

In FIG 2, the apparatus comprises a first pressure vessel 10 for receiving solvent and contaminated oil to form a solution, the first pressure vessel 10 having top and bottom portions 12 and 14, respectively, the bottom portion 14 being adapted for dispersing gas into the solution in the first pressure vessel 10 through a line 15, and recovery means in the form of a solvent stripper 16 whereby the solution is separated into a vaporised solvent and oil, the vaporised solvent being reintroduced by sparging through the bottom portion 14 of the first pressure vessel 10 through the line 15.

The apparatus also comprises a supply of contaminated oil such as drain oil 18 in fluid communication with the first pressure vessel through a drain oil inlet line 20 and valve 22, a drain oil charge pump 24 pumping the drain oil to the first pressure vessel 10. Further, the apparatus includes a supply of liquid solvent 26 which is introduced into the first pressure vessel 10 through a liquid solvent line 28 and a valve 30, a liquid solvent pump 32 being provided for pumping the liquid solvent from the supply 26 to the vessel 10.

Advantageously, the feed lines 20 and 28 intersect to form a third line 34 which leads to the vessel 20 such that the third line 34 introduces liquid solvent and drain oil simultaneously into the vessel 10 to form a solution. An inlet port 152 permits selective introduction of a flocculation enhancing reagent. Additionally, the apparatus comprises a second pressure vessel 36 in fluid communication with the first vessel 10 through line 38, the second vessel 36 including top and bottom portions 40 and 42 respectively. Advantageously, the solvent and oil in solution are removed from the first vessel 10 and introduced into the second vessel 36 by a pressure differential between the vessels.

The apparatus further includes a solution, asphalt residuum and water separating tank 44 which includes an inlet 46 in fluid communication with the vessel 10 whereby solvent and oil in solution, asphalt residuum and water are transferred from the bottom portion 14 to the separating tank 44 by a pump 48. The separating tank 44 also includes a first outlet 50 whereby water is removed from the tank 44, a second outlet 52 whereby asphalt residuum is removed from the tank 44, and a third outlet 54 whereby solvent and oil in solution are returned to the first vessel 10. Inside the tank 44 is found a weir 56 (not shown) over which solvent and oil flows and also a water outlet 50. The apparatus further comprises an asphalt residuum mix tank 60 which includes an inlet 62 in fluid communication with the second outlet 52 of the tank 44 through which asphalt residuum is received through line 64 and also an outlet 66 from which asphalt product is removed. Advantageously, the bottom portion 42 of the vessel 36 is in fluid communication through line 68 with the inlet 62 of the mix tank 60, whereby additional asphalt residuum is removed from the vessel 36. As mentioned, the apparatus includes a solvent stripper 16 which serves as recovery means which is in fluid communication through line 70 with the second vessel 36. A charger pump 72 is included in the line 70 to facilitate transport of the solvent and oil solution to the stripper 16. Also, the charger pump 72 increases the pressure differential between the vessel 36 and the stripper 16. Preferably, the stripper 16 comprises a packed column 74 into which solvent and oil solution flows, the column 74 having top and bottom portions 76 and 78 respectively, the top portion 76 including an outlet 80 through which most of the heated vaporised solvent is removed from the stripper 16. The stripper 16 further comprises a reboiler 82 integrally connected to and in fluid communication with the bottom portion 78 of the column 74, the reboiler 82 including an outlet 84 through which the oil and any remaining solvent are removed from the stripper 16.

The apparatus further comprises a condenser 86 which is in fluid communication both with the top portion 76 of the packed column 74 and with the supply of solvent 26 through a line 88, whereby heated vaporised solvent can be condensed into liquid form and replaced into the solvent supply 26 for future use.

The apparatus further comprises a gasoline flash drum 90 having top and bottom portion 92 and 94 respectively, the top portion 92 including an outlet 96 and the bottom portion 94 including an outlet 98, the drum 90 being in fluid communication through line 100 with the reboiler 82, such that oil and any remaining solvent are transported from the solvent stripper into the gasoline flash drum 90.

The apparatus also comprises another condenser 102 in fluid communication through line 104 with top portion 92 of the drum 90, whereby the vaporised gasoline is condensed into a liquid. The apparatus further comprises a gasoline collection drum 106 having top and bottom portions 108 and 110 respectively, the top portion 108 including an outlet 112 for solvent and the bottom portion 110 including outlet 114 for liquid gasoline, the drum 106 being in fluid communication through line 116 with the condenser 102, such that gasoline and solvent are transported from the condenser 102 into the drum 106. The apparatus further comprises a gasoline pump 118 in fluid communication 120 with the outlet 114 of the drum 106, whereby finished gasoline product is pumped into a gasoline supply (not shown).

The apparatus further comprises a two stage compressor and interstage cooler 122 in fluid communication through line 124 with the outlet 112 in the drum 106, such that the solvent in the drum 106 passes therethrough to be further compressed and cooled. The compressor and cooler 122 are in fluid communication through line 126 with the condenser 86, such that solvent that has passed therethrough is condensed and returned to the solvent supply 26 for further use. An interstage suction scrubber (not shown) is adjacent to and in fluid communication with the cooler and compressor 122 such that liquid condensed therein is returned to the drum 106.

The apparatus also comprises a vacuum distillation column 128 having top, middle and bottom portions 130, 132 and 134 respectively, the top portion 130 including an outlet 136 for finished diesel fuel product, middle portion 132 including an outlet 138 for finished lubrication oil product and the bottom portion 134 including an outlet 140 for heavy oil and distillation residues, the column 128 being in fluid communication through line 142 with the outlet 98 in the drum 90. The apparatus further comprises a furnace 144 for heating the oil in the column 128. Also, the column 128 is in fluid communication through line 146 with the inlet 62 to the tank 60, whereby heated heavy oil distillation residues are introduced into the tank 60 to mix with the asphalt residuum to create a final asphalt product. An asphalt pump 148 preferably circulates the residuum and oil to facilitate mixing. Line 150 is also provided between the tank 60 and the condenser 102 such that excess solvent vapour and water are removed from the tank 60. A flocculation enhancing reagent may be introduced into the first pressure vessel 10 via an introduction port 152 from a suitable storage means (not shown). The flocculation enhancing reagent may comprise water, an aqueous solution of a strong electrolyte such as a strong acid or an alkaline earth metal hydroxide or other suitable reagent or a mixture thereof.

Sodium or potassium hydroxide solutions may, if required, be introduced via either or both of ports 152 and 156 in an endeavour to improve the colour of the finished base oil product.

Pilot scale operations conducted over prolonged periods of operation have shown no reduction or change in efficiency of any of the separating, stripping, reboiling or vacuum distillation vessels and there is little or no evidence of coking or corrosion in any of the components of the apparatus other than the asphalt mix tank which shows mild tar stains.

FIG 3 shows an alternative embodiment of the asphalt residuum processing system shown generally as 60 in FIG 2 and for the sake of clarity, where applicable, the same reference numerals have been employed.

As the residuum from the propane extraction unit 44 is, under normal conditions when cooled, a solid mass containing both water and entrained propane gas, it would otherwise be unsuitable for sale as a byproduct and generally difficult to handle for disposition.

The process according to the invention combines the heavy oil still residues from vacuum distillation column 128 with the viscous residuum, water and propane mix from propane extraction vessel 44 and vessel 36 via conduits 146 and 64/68 respectively by pumping both streams through a static mixer 300. The mixture is then passed through a heat exchanger 301 where the temperature of the mix is raised to about 150°C.

The heated mixture then flows via conduit 302 to an inlet 303 associated with an extraction vessel 304. A spray head 305 in fluid communication with inlet 303 sprays the mixture in a thin film over shed trays 306 to enhance the separation of propane and water vapours from the mixture. An outlet 307 is in fluid communication with conduit 150 (FIG 2) to recover and separate the propane and water vapours. The residuum/oil mixture then leaves vessel 304 via outlet 308 and asphalt pump 309 and is dispensed from conduit 310 as a viscous liquid, free of water and propane in the form of a saleable product as an asphalt extender for roofing or paving applications or the like.

Although the process and apparatus according to the invention have been illustrated with reference to the removal of contaminants from used motor vehicle lubricating oils or "drain oils", it will be readily apparent to a skilled addressee that the process and apparatus, with no modification or some modifications, are applicable to decontamination of other oils.

For example the process may be employed as an upstream function in a petroleum cracking/distillation plant to remove from the feedstock asphaltenes and other contaminants which may reduce cracking efficiencies by catalyst poisoning or the like and otherwise reduce the efficiency of the vacuum distillation process and lead to premature coking and corrosion in the distillation column.

Similarly, still residues from conventional cracking/distillation processes may also be treated in accordance with the present invention to extract valuable lighter fractions which otherwise cannot be extracted economically from still residues and the like. The invention also permits the economic recovery of valuable hydrocarbons from bunker oil slops obtained from ship's bilges, oily wastes and emulsions generated in tertiary crude extraction processes and oil wastes and emulsions produced in sea bed extraction of crude oils.

The byproduct of the process according to the process according to the invention is a vendible product in the form of an asphalt extender and where heavy metals and other toxic materials are extracted from the contaminated oils, the asphalt extender material provides a safe, non water leachable binding matrix which avoids the necessity and high costs and risks associated with other means for disposing of toxic contaminants .

If required, the base oil product produced in accordance with the invention may be upgraded even further by a known hydrotreatment process.

It will be equally apparent to a skilled addressee that many modifications and variations may be made to the process and apparatus according to the invention without departing from the spirit and scope thereof.

Claims

1. A method of removal of contaminants from oil, the method comprising the steps of:- forming a solution of contaminated oil in a liquid aliphatic solvent in the presence of a flocculation enhancing reagent in a first pressure vessel; introducing in a lower region of said first pressure vessel a gas in the form of fine bubbles whereby said solution is agitated by the bubbles rising through the solution and contaminants are caused to separate from solution by a flocculation reaction; separating flocculated contaminants from the liquid solution; and, separating the solvent from the solution to obtain an oil substantially free of contaminants.

2. A method as claimed in claim 1 wherein the solvent comprises a C, to C₇ alkane.

3. A method as claimed in claim 2 wherein the solvent comprises liquid propane or butane or a mixture thereof.

4. A method as claimed in any one of claims 1 to 3 wherein the flocculation enhancing reagent is selected from water and/or an electrolyte solution.

5. A method as claimed in claim 4 wherein at least 2% v/v of water is present in the solution of oil and solvent during the flocculation reaction.

6. A method as claimed in claim 5 wherein at least 3% v/v of water is present in the oil and solvent solution of oil and solvent during the flocculation reaction.

7. A method as claimed in claim 6 wherein water is present in the oil and solvent solution at a concentration in the range of from about 3% to 6% v/v.

8. A method as claimed in any preceding claim wherein an electrolyte is employed as a flocculation reagent .

9. A method as claimed in claim 8 wherein the electrolyte comprises a strong acid or alkali.

10. A method as claimed in claim 9 wherein the electrolyte is selected from H₂S0₄, HC1, NaOH or KOH.

11. A method as claimed in any preceding claim wherein the flocculation reaction is carried out with an electrically conductive member in physical contact with the oil and solvent solution.

12. A method as claimed in any preceding claim wherein the gas comprises a polar or non polar gas.

13. A method as claimed in claim 12 wherein the gas is selected from C0₂, N₂ or a Cj to C₄ alkane.

14. A method as claimed in claim 13 wherein the gas comprises propane or butane or a mixture thereof.

15. A method as claimed in claim 14 wherein the gas comprises propane when the aliphatic solvent is propane.

16. A method as claimed in any preceding claim wherein the flocculation reaction is carried out at a temperature of between 15°C and 45°C.

17. A method as claimed in claim 16 wherein the flocculation reaction is carried out at a temperature of between 15°C and 30°C.

18. A method as claimed in claim 18 wherein the flocculation reaction is carried out at a temperature between 18°C and 25°C.

19. A method as claimed in any preceding claim wherein the method of removal of contaminants from oil comprises the further step of: transferring, from the first pressure vessel to a second pressure vessel, an oil and solvent solution from which contaminants have been flocculated; allowing any residual contaminants to settle from the oil and solvent solution; transferring from the second pressure vessel to a solvent stripping vessel an oil and solvent solution substantially free of contaminants; and stripping solvent from the oil and solvent solution to obtain a substantially contaminant free oil fraction.

20. A method as claimed in any preceding claim wherein the substantially contaminant free oil fraction is further purified by a distillation process.

21. A method as claimed in claim 20 wherein the distillation process is carried out under reduced pressure.

22. A method as claimed in claim 20 or claim 21 wherein before distillation, the substantially contaminant free oil fraction is subjected to a stripping process to remove any residual solvent and any light petroleum fractions therefrom.

23. A method as claimed in any preceding claim wherein contaminant residues from the first and/or second pressure vessels are subjected to a stripping process to remove water and any residual solvent.

24. A method as claimed in claim 23 wherein contaminant residues from which water and any residual solvent have been removed are mixed with a hot oil to obtain a flowable asphalt extender.

25. A method as claimed in claim 24 wherein the hot oil comprises a distillation residue from the distillation process.

26. A method as claimed in any preceding claim wherein the contaminated oil comprises automotive drain oil.

27. A method as claimed in any one of claims 1 to 25 wherein the contaminated oil may comprise crude petroleum oil.

28. A method as claimed in any one of claims 1 to 25 wherein the contaminated oil comprises residues from a petroleum cracking and/or distillation process.

29. A method as claimed in any one of claims 1 to 25 wherein the contaminated oil comprises bunker oil slops from ship's bilges.

30. A method as claimed in any one of claims 1 to 25 wherein contaminated oil comprises oil/water mixtures and or oil/water emulsions obtained in petroleum drilling operations.

31. A method of refining crude oils to obtain a bright oil product, the method comprising removal of contaminants from a crude oil feedstock according to any one of claims 1 to 25 and subjecting the substantially contaminant free oil feedstock to a subsequent refining process.

32. A method of beneficiating distillation residues in a petroleum refining process, the method comprising the steps of treating a distillation residue in accordance with any one of claims 1 to 25 and separating lighter fractions from a contaminated residue formed thereby.

33. A method of beneficiating water containing oil residues from petroleum drilling operations, the method comprising treatment of the water containing residues according to any one of claims 1 to 25 to extract substantially contaminant free oil fractions therefrom.

34. A method of beneficiating bunker oil slops comprising the treatment of bunker oil slops in accordance with the method according to any one of claims 1 to 25 to extract substantially contaminant free fuel oil fractions therefrom.

35. A method according to claim 33 or claim 34 wherein in the beneficiation of water containing oil residues from petroleum drilling operations and/or bunker oil slops, the water content of the oil containing residue to be treated is first subjected to a water extraction process to reduce the water content of material to be treated to less than 10%.

36. An apparatus for removal of contaminants from oil, said apparatus comprising:- a first pressure vessel in fluid communication with a source of contaminated oil and a solvent and, selectively, a source of flocculation enhancing reagent comprising water and/or an electrolyte; a source of pressurised gas selectively introducible via an inlet port adjacent a lower portion of said first pressure vessel to disperse fine gas bubbles through an oil/solvent/flocculation reagent contained therein; an outlet port in fluid communication with said inlet port to circulate gas introduced into said first pressure vessel; a decanting port to selectively remove an oil/solvent solution substantially free of contaminants from said first pressure vessel; and a contaminant outlet port adjacent a lower region of said first pressure vessel to selectively remove flocculated contaminants settled in said lower region.

37. An apparatus according to claim 36 including a second pressure vessel to accumulate a decanted substantially contaminant free oil solvent solution from said first pressure vessel, said second pressure vessel including an outlet port for substantially continuous withdrawal of a substantially contaminant free oil/solvent solution therefrom and an outlet port in a lower region of said second pressure vessel for removal of accumulated flocculated contaminants settling therein.

38. An apparatus - according to claim 37 further including a solvent stripping vessel to strip solvent from said substantially contaminant free oil/solvent solution extracted from said first and/or second pressure vessel, the solvent so extracted being returned to said source of solvent.

39. An apparatus according to claim 38 including a further stripping vessel to remove from a solvent stripped material delivered from said stripping vessel any residual solvent and light petroleum fractions.

40. An apparatus according to claim 39 including a distillation column to remove a base oil product from said solvent stripped and light petroleum stripped fractions delivered from said further stripping vessel.

41. An apparatus according to any one of claims 37 to 40 including a residuum collection vessel to collect contaminants from said first • and for said second pressure vessels.

42. An apparatus according to claim 41 wherein said residuum collection vessel is adapted to separate water and/or residual solvent from residuum so collected.

43. An apparatus according to claim 42 wherein said residuum treatment vessel includes heating means to provide a flowable residuum material.

44. An apparatus as claimed in claim 43 wherein said residuum treatment vessel includes a mixing apparatus to mix an oil with said residuum to provide a flowable product.

45. An apparatus as claimed in claim 44 wherein said residuum treatment vessel is in fluid communication with said distillation column to provide an oil distillation residue for mixing with said residuum.

46. An apparatus for production of bright oil from crude oil, said apparatus comprising a decontamination apparatus according to any one of claims 37 to 45 for pretreatment of crude oils upstream of a conventional crude oil processing apparatus.

47. An apparatus for processing of distillation residues in a conventional petroleum distillation apparatus said apparatus comprising an apparatus according to any one of claims 37 to 46 to extract valuable petroleum fractions from petroleum distillation residues.

48. An apparatus according to any one of claims 337 to 45 for the beneficiation of water containing crude oils obtained from petroleum drilling operations.

49. An apparatus according to any one of claims 37 to 45 for beneficiation of bunker oil slops obtained from ship's bilges.

50. An apparatus according to any one of claims 37 to 45 for treatment of oil containing residues from commercial and public utilities for oil separation from waste and/or storm water sources.