SK86396A3 - Separation method of hydrophobic liquid fraction from aqueous suspension and device for carrying out this method - Google Patents

Abstract

Process and device for separating the hydrophobic fraction from watery suspension, esp. crude oil or its distillates, etc., from the watery suspension containing hydrophobic liquide fraction from 10 to 40 % of wt., esp. from 15 to 25 % of wt., eventually from 18 to 22 % of wt. and sediment fraction, e. g. stone powder from 25 to 40 % of wt. where the watery suspension, eventually with adding water, is placed in the vessel, esp. in waste vessel, and the hydrophobic liquide fraction is removed from the water surface and water is removed from the watery suspension. The suspension in the vessel is mixed several times with water and hydrophobic liquide fraction is removed from the water surface and from the suspension containing small part of hydrophobic liquide fraction the water is removed. The remaining hydrophobic content fraction is broken down again in the suspension. Dicslosed is also device for realization of this process.

Description

A method for separating a hydrophobic liquid fraction from an aqueous suspension and an apparatus for carrying out the method

Technical field

The invention relates to a process for separating a hydrophobic liquid fraction from an aqueous suspension and to an apparatus for carrying out the process.

When opening oil fields and extracting oil, mixtures of fine-grained stone meal, sand, various grains and similar substances with oil and water are eliminated. These mixtures are commonly referred to as sludges and are processed in various ways. One such mixture exhibits a characteristic solid to oil ratio ranging from 1.5 to 1.7 parts by weight. The remainder of the mixture is water, with a relatively high content of petroleum products present at least 8% by weight. Such sludges, which may be referred to as suspensions, contain up to 40% by weight of a hydrophobic liquid fraction, for example petroleum.

BACKGROUND OF THE INVENTION

In the United States, such sludges had previously been mixed with agricultural land to reduce their total crude oil content, with the degradation of oil products into carbon dioxide and protein. However, the use of such a method was essentially limited to areas with small rainfall where there is no risk of groundwater contamination.

In order to minimize drilling fluid or similar waste sludge, the sludge is returned to the wells after separation of the coarse fractions, for example by sieving or centrifuging. Closed or near-closed systems are particularly energy and labor intensive, so they can only be used at some special sites.

The usual practice of treating drudge sludge and similar fluids is to subject these sludge to slow separation of oleophilic and hydrophilic components in large waste tanks, while achieving a far-reaching separation of water. In this treatment, the sludge is introduced into a tank, which is for example a multiple-insulated and controlled waste tank, and in this waste tank it is overlaid with water, possibly from an analogous treatment that has taken place in another waste tank. In the waste tank gravitational sedimentation of the sludge occurs, while in the sediment itself finely divided petroleum products are still enclosed. Due to the surface tension of the petroleum products, larger drops of petroleum products are formed over time, which, due to the difference in the specific weights of the petroleum products and the water, flow to the surface. This ascent of larger droplets of petroleum products to the surface is further supported by anaerobic fermentation in the sediment to produce mining gas (methane) or similar gases which, due to the large difference between their specific gravity and specific gravity of water, easily rise just like petroleum products as well as pores or channels through which petroleum products can more easily rise to the surface. On the surface (at the level of the waste tank) the oil is sucked off, then it is freed from adhering water and introduced into industrial oil processing. If desired, such deposition may take a longer period of time, for example years, with the hydrophobic phase becoming increasingly slower in the sludge or sediments. Also, if necessary, after the analysis of the average sediment composition, the superimposed water can be withdrawn and the sediment, which generally has a content of at least 15% by weight of petroleum products, is then deposited in a separate depot. Such a depot must meet specific requirements. For example, these landfills must not communicate with the groundwater level in the surrounding area. For example, salt mines meet these conditions because salt deposits have existed for centuries merely as a result of not being associated with any water source that would otherwise leach these salt deposits in a relatively short time.

The invention itself is based on the aforementioned prior art.

The prior art further relates to US-A-4851123, which describes the treatment of an oil refinery waste product, wherein the waste product contains 13 wt% solids, 8 wt% oil, lubricating fat and the like, and the remainder being water. The mixture is stirred vigorously and the suspension above the solid is decanted. A flotation liquid having a foaming nature is added to the decanted fraction thus obtained and compressed air is introduced into the mixture. Foam accumulating at the surface contains a large proportion of the oil present in the sludge.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for separating a hydrophobic liquid fraction from an aqueous suspension, and an apparatus for carrying out the process, using which the hydrophobic phase can be separated from the aqueous suspension at low equipment, energy and labor costs. it could be deposited without jeopardizing the ocular environment and possibly simply exposed to further natural microbiological degradation.

SUMMARY OF THE INVENTION

A method for separating a hydrophobic liquid fraction, in particular petroleum, petroleum distillates or the like, from an aqueous suspension having a hydrophobic liquid fraction of from 10 to 40% by weight and 18 to 22% by weight, respectively, and sediment from the fraction, e.g. up to 40% by weight, whereby the aqueous suspension is deposited, optionally with the addition of water, into a tank, in particular a waste tank, and the hydrophobic liquid fraction is withdrawn from the water surface and water is removed from the aqueous suspension according to the invention. The hydrophobic liquid fraction is drawn off on the surface of the water several times, water is then removed from the suspension containing a small proportion of the hydrophobic liquid fraction and, if necessary, the hydrophobic liquid fraction in the suspension is further removed.

Such aqueous suspensions fall off in the oil industry at various stages of operation and have a typical solid to oil ratio of 1.5 to 1.7. Such means are dispensed with, for example, in the opening of oil fields, both for drilling wells and for drilling wells during oil extraction or oil well rinsing, but also in oil processing operations. The sediment fraction, such as stone meal, petroleum coke, washed soil and the like, is generally no longer extractable by water or is no longer highly extractable so that the inert substance can be recycled without danger. The proportion of water normally reduced by natural evaporation can be substantially recirculated for further treatment of the waste products. Only the sludge portion, which has a too high proportion of hydrophobic liquid components, must be subjected to further treatment. Due to the excessively high amount of such sludge fraction, only one method of treating the sludge which is as simple as possible and with low labor costs is conceivable. While such sludges can be thermally inerted, such processing is so expensive in terms of total energy consumption and downstream waste gas treatment that there is a need to worry about considerable environmental burdens, such as untreated filter ash, filter residues and the like. There is also the possibility of extracting sludges containing the hydrophobic liquid fraction with organic solvents, but then the hydrophobic components separated from the organic solvents must be extracted again. Such a process is particularly expensive and cannot be used with a large number of slurries containing a hydrophobic liquid fraction. It was very surprising that a few simple process steps could lead to a high degree of separation of the hydrophobic liquid fraction, namely that the suspension in the tank was mixed several times with water and then the washed-out fractions of hydrophobic liquid fractions were withdrawn to the water surface and finally dehydrated . The friable suspension thus obtained or the remainder of the suspension containing a small amount of water can be degraded, for example microbiological, due to their low hydrocarbon content.

If the slurry is mixed with water using gas jets, in particular air, then particularly good mixing is achieved, and at the same time, as a result of rising gas bubbles, pores with a minimum cross-section corresponding to about gas bubbles are formed in the suspension. further separating the hydrophobic liquid fractions. Air as a stirring gas provides the additional advantage that fermentation can take place, for example optional aerobic fermentation, whereby, as a matter of exchange products, also gases are formed which, together with the hydrophobic liquid fractions, can rise to the surface of the superimposed water.

If air is pulsed into the suspension in a pulsed manner, preferably at a pressure of 0.5 to 1 MPa for a certain period of time, in particular for 1 to 5 seconds, then a particularly good and simple mixing of the suspension with water may occur due to different pressure. due to the time limitation, the oleophilic droplets can disintegrate so that the droplets can join more quickly and thus float to the surface of the water without hindrance.

If the gas, especially air, is introduced into the suspension and / or below the suspension via a gas line, then pores are formed in the suspension in a simple manner which, due to the possibility that the gas may also have only slight overpressure, favorably bind the hydrophobic droplets. suspension.

If the gas, in particular air, is heated prior to introduction, in particular to a temperature of 40 to 50 ° C, this will increase the buoyancy of the gas in the slurry or in the water while simultaneously heating the slurry and thereby substantially increasing the fermentation rate of the microorganisms. further reducing the surface tension of the individual oleophilic droplets in the suspension, so that the speed of their mutual bonding and thus the rate of their exit to the water surface is increased.

If the gas, in particular air, is suspended in a water-borne carrier, preferably by means of a plunger, the desired discontinuous gas supply is achieved even with large tanks or waste tanks, while maintaining particularly low set-up costs, so that the desired mixing in the over the entire range of the tank or waste tank in a particularly simple manner.

If the washed-out suspension is recycled to the bottom of the tank, for example by means of a sludge pump and possibly together with air, a particularly high degree of separation of the suspension into hydrophilic and hydrophobic components can be achieved, while increasing the mixing rate as a result again to the bottom of the driven suspension.

If, after completion of the separation of the hydrophobic liquid fraction, the water is drawn off, in particular by means of a liquid pipe arranged below the suspension, a particularly efficient dehydration of the water suspension can be carried out so that the total weight of the fraction to be subjected to post-treatment can be kept at a particularly low value. at the same time, it ensures favorable water management.

If the slurry from which the water has been withdrawn is deposited in the graves which are turned, in particular mechanically, aerobic fermentation of the already partially dried suspension can be carried out, using conventional techniques such as turning the graves by mechanical means, storing the graves on waterproof substrates, soils and similar substrates.

If the slurry from which the water has been withdrawn is mixed with structuring materials, for example straw, bark or the like, the oxygen-containing air is thereby particularly easily accessed and the exchange of the products of exchange is also ensured in a particularly simple and efficient manner, carbon dioxide, mining gases and the like, from said mixture due to its permeable structure.

If the suspension is mixed with microorganisms, in particular with carrier substrates of microorganisms, for example wooden drilling plates of production equipment which microorganisms degrade liquid hydrophobic substances, advantageous decomposition of specific petroleum or similar products can thus be achieved, using microorganisms specialized in these specialty. hydrocarbons.

A particularly preferred embodiment of the invention consists in mixing the suspension with a green mower, for example with mowed grass or cut bushes. This generally contains thermophilic microorganisms which cause accelerated decomposition of the green matter at elevated temperature. On the one hand, advantageous drying of the substrate can be carried out and, due to the elevated temperature, accelerated decomposition of the oleophilic components by the same degrading microorganisms can be carried out, provided that only the islet circuits, namely those in contact with green matter, have to 70 ° C.

If a nitrogen source is added to the slurry, it is particularly preferable to take into account the excess carbon supply related to the degradation of microorganisms and the construction of the body's own substances.

The invention also relates to an apparatus for the environmentally friendly treatment of petroleum-containing substances and the like which is capable of containing large volumes of said petroleum-containing substances and which allows the treatment of large amounts of suspensions contaminated with hydrophobic substances with minimal energy and labor requirements.

An apparatus according to the invention for separating a hydrophobic liquid fraction, in particular oil, petroleum distillates and the like, from an aqueous suspension having a waste tank having at least one waterproof layer of clay, plastic or the like, which is coated with crushed gravel and / or coarse sand, and a surface-layer withdrawal device, consists in providing in the crushed gravel and / or coarse sand a liquid withdrawal line and / or a gas supply line. Such a device permits a particularly simple and environmentally friendly method for storing suspensions containing petroleum products, while also allowing the liquid, i.e. water, to be withdrawn from the substrate, and also providing a gas supply to assist the coupling of the oil droplets or the like.

If it is envisaged to use a plunger that is movable on the surface of the water and which carries the gas injection device and / or the sludge pump, then mixing of the suspension with the water in the whole tank can be achieved without high installation costs, further allowing by recirculating the sludge to achieve a deep spray of the bottom slurry, whereby the sludge brought to the surface is recycled to the slurry and contact with other oleophilic particles.

If the gas injection device comprises a pressure boiler, then a large amount of gas under high pressure can be taken off in a short time, which causes a particularly good mixing of the suspension with water.

In the case where the sludge pump comprises a suction that opens close to the water level, a slurry which, for example, contains gas bubbles, can be returned to the bottom slurry in a particularly simple manner.

In the following, the invention will be elucidated with reference to the accompanying drawings, in which: FIG

FIG. 1 shows a cross-section of a waste tank and FIG

2 shows a cross-section of two adjacent graves.

The waste tank shown in FIG. 1 has a plastic film 1, in this case polyethylene, with a film thickness of 2 mm. Below and next to the film is a layer of clay 2 with an average thickness of 60 cm. Suction tubes 2 are provided below the foil 1 and the clay layer 2, which serve to indicate the liquid accidentally escaping from the waste tank 4. At the bottom 5 of the waste tank 4 there is a coarse sand layer 6 in which the water suction line 7 is arranged. This conduit has perforations along the surface lines so that water can be sucked out all over the bottom 5 of the waste tank 4. Above the coarse sand layer 6 there is another fine-grained layer 8 in which an air conduit 9 is also provided, which also has perforations. Above these two layers. and a thickness of 25 cm (each) is a suspension 10 having a height of about 300 cm. At the water level 11, a rafter 12, which can be pulled along the water surface by means of a rope traction device (not shown), floats. An air blowing device 12 and a sludge pump 14 are provided on the slat 12. The air blowing device 13 has an air tank of 150 liters in which air is stored in an airtight manner, which can be radially discharged to the bottom within a second. The valve opens automatically when the pressure inside the air tank reaches 1 MPa. Such air-blowing devices are known from silo equipment where they serve, for example, to separate cereal grain aggregates from the silo walls. The sludge pump 14 sucks off the sludge swirled by the air blowing device from the surface and pushes it back into the slurry 10. The coating layer pulling device 15 has a hose 16 having a hydrophobic design and which, as it moves along the water level 11, withdraws the washed-out hydrophobic fraction. The hose is pushed between the two rollers 17 and the hydrophobic phase, generally formed by oil, is discharged via line 18 to the buffer reservoir. From the buffer reservoir, the sucked-off liquid is fed to a separation tank in which further separation into an oleophilic phase and a hydrophilic phase takes place. The oleophilic phase thus separated is then fed to a refinery for further conventional processing. For example, the waste tank described above has the capacity to hold 15,000 m ^{3 of} liquid, wherein, as already mentioned, the height of the sludge or suspension layer is about 300 cm and the height of the water layer is about 100 cm.

Fig. 2 shows the graves 19 from a slurry depleted in a portion of an oil fraction that already has a crumbly consistency and into which straw and bark have been mixed. These tombs have a width b of 300 cm and a height h of 170 cm. If desired, easily rotting substances such as mowed green from farmland and parks, in particular grass and shrubbery, can be incorporated into these tombs in order to raise the temperature for subsequent fermentation. The tombs are arranged so that conventional tedders can be used.

In the following, the invention is illustrated by means of specific examples of its implementation, and these examples are illustrative only and are not intended to limit the scope of the invention, which is clearly defined by the definition of the claims.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

10,000 cm @ ^{3 of} suspension are introduced into the waste tank according to FIG.

18,0% by weight of crude oil (2 135,2 t),

30,0% by weight of stone meal (3 558,6 t) and

52.0% by weight of water (6,170.0 t).

This mixture is then overlaid with about 3,000 m ^{3 of} water that has been withdrawn from the adjacent waste tank.

In the slurry layer, insignificant anaerobic fermentation occurs during slurry deposition, and about 390 tons of crude oil can be withdrawn in ten years. After the water has been drawn off, the suspension is deposited on the slope of the waste tank and has the following composition:

15.2% by weight of oil,

31,0% stone meal and

53.8% by weight of water.

Only about 20% by weight of crude oil from the total amount of crude oil present in the slurry was separated over a decade.

Example 2

A 10,000 cm ³ slurry according to Example 1 is introduced into a waste tank, which is constructed analogously to the waste tank of Example 1 and has the same size. This slurry was then overlaid with 3,000 m ^{3 of} water. Then, a rafter is placed above the waste tank, which has a surface area of 25 x 120 m, on which air blowing devices and a sludge pump are arranged. The air blowing device was led in the transverse direction of the waste tank back and forth at a rate of 2 meters per minute, with intensive mixing of water with the slurry located at the bottom of the waste stream during pulse air blowing at 1 m ³ per minute and under 1 MPa. tank. During the storage of the slurry in the waste tank, air is further supplied via an air duct located at the bottom of the waste tank in an amount of 60 m ³ / m ³ / h. The air was heated to 40-50 ° C. The slurry washed up to the water level is recirculated together with the air back to the slurry.

In sixty days, 1,801 tons of oil were withdrawn from the surface. The water above the slurry was then withdrawn through the conduit below the slurry and the slurry was subjected to drying by supplying air, in particular air heated to 40-50 ° C. The thus obtained pre-dried suspension has the following composition:

6.0% by weight of oil, 64.0% by weight of stone meal and 30.0% by weight of water.

This suspension is then mixed with about 1 wt% straw and about 4 wt% cut slurry. Wood sawdust cuttings containing microorganisms were also added to the cut stock. Such wood panels are used in boreholes. The mixture thus obtained now has the following composition:

5.70% by weight of oil,

60,95% by weight of stone meal,

28,55% by weight of water,

0.95% straw and

3.85% by weight green cutter.

This mixture, which is still flowable at the outset and which becomes friable over time, is placed in graves, 300 cm wide and 170 cm high. After five weeks, the composition has the following composition:

2.4% by weight of oil,

69,5% by weight of stone meal,

25.2% by weight of water; and

2.9% straw and green cutter.

During the fermentation, the mixture was inverted at intervals of 3 days to achieve homogenization and aeration.

The mixture was fermented for a further eleven months, with the graves being turned over at weekly intervals and moistened to a water content of about 15% by weight as needed. The mixture then has the following composition:

0.8% by weight of oil,

84,8% stone meal and

15.4% by weight of water.

In this way, about 98.5% by weight of oil was regenerated or converted by microorganisms to carbon dioxide.

If the nitrogen content is too low, other nutrients may be added to the sludge or the graves.

The crude oil content of the individual fractions was determined by extraction with n-heptane. The fraction of the sediment product was determined by filtration and subsequent firing of the residue on an oxygen inlet filter at 650 ° C. At this temperature, both microorganisms, as well as straw and green grass are oxidized. The green cutter and straw are determined by filtration, and the pore ratio of the filter must be chosen such that sediments are passed into the filtrate in addition to the oil and water.

Instead of air, other gases can also be used, for example, combustion gases but also oxygen-enriched air or other gases.

Although mixing of the slurry with the injected gas streams results in a particularly intense mixing of the slurry with water, whilst at the same time facilitating the connection of the oleophilic droplets, other mixing devices, such as mechanical stirrers, can also be used. into the waste tank.

Although the invention has been elucidated by means of petroleum products, the invention is also suitable for other oleophilic substances which are present in a mixture with a solid and an aqueous phase, typically water. It is a prerequisite for the use of the process according to the invention that the suspension has a high viscosity, so that the oleophilic droplets can hardly coalesce. Examples of such oleophilic substances are linseed oil, peanut oil and the like. Examples of sediments are, for example, carbon black, chalk, clay, solid ion exchangers, dust and the like.

Claims (17)

A method for separating a hydrophobic liquid fraction, in particular petroleum, petroleum distillates and the like, from an aqueous suspension having a hydrophobic liquid fraction of from 10 to 40% by weight, in particular from 15 to 25% by weight or 18 to 22% by weight, and sediment fraction, for example, stone meal, from 25 to 40% by weight, in which the aqueous suspension, optionally with the addition of water, is stored in a tank, in particular a waste tank, and hydrophobic liquid fraction is withdrawn from the water surface; by water and fraction, whereby the suspension in the tank is mixed several times with the surface of the water, the hydrophobic liquid is withdrawn from the suspension containing a small fraction of the hydrophobic liquid fraction and the fraction of the hydrophobic liquid fraction in the suspension is optionally further removed. Method according to claim 1, characterized in that the slurry is mixed with water by means of gas streams, in particular air. Method according to claim 1 or 2, characterized in that the gas, in particular air, is introduced into the suspension in a pulsed manner, preferably under a pressure of 0.5 to 1 MPa, for a period of preferably 1 to 5 seconds. Method according to claim 1, 2 or 3, characterized in that the gas, in particular air, is introduced through a gas line which is arranged in suspension and / or under suspension. Method according to one of Claims 1 to 4, characterized in that the gas, in particular air, is heated to 40 to 50 ° C in particular before being introduced. Method according to one of claims 1 to 5, characterized in that the gas, in particular air, is introduced into the suspension by means of a carrier, preferably a plume, guided along the surface of the water. Method according to any one of Claims 1 to 6, characterized in that the flooded suspension is returned to the water surface, for example by a sludge pump, optionally together with air, to the suspension located at the bottom of the tank. Method according to one of Claims 1 to 7, characterized in that after the hydrophobic liquid fraction has been separated off, water is drawn off, in particular by a liquid line arranged below the suspension. Method according to one of Claims 1 to 8, characterized in that the slurry from which the water has been withdrawn is deposited in the graves which are turned, in particular mechanically. Method according to one of Claims 1 to 9, characterized in that the slurry from which the water has been withdrawn is mixed with structuring materials, for example straw, bark or the like. Method according to one of Claims 1 to 10, characterized in that the suspension is mixed with microorganisms, in particular with carrier substrates of microorganisms, for example wooden drilling plates which degrade the hydrophobic liquid fraction. Method according to one of claims 1 to 11, characterized in that the suspension is mixed with a mowing of green vegetation, for example grass or shrubbery. Process according to one of Claims 1 to 12, characterized in that nitrogen sources are added to the suspension. Apparatus for separating a hydrophobic liquid fraction, in particular petroleum, petroleum distillates and the like, from an aqueous suspension, in particular according to any one of claims 1 to 13, with a tank having at least one waterproof layer, for example clay, plastic or the like, which is coated with crushed gravel and / or coarse sand and having an apparatus for drawing off the surface layer for the aqueous surface layer and / or the layer thereon, characterized in that a drainage line is provided in the crushed gravel and / or coarse sand liquid and / or gas supply line. Apparatus according to claim 14, characterized in that it comprises a cane which is movable along the surface of the water and which carries a gas injection device and / or a sludge pumping device. Apparatus according to claim 14 or 15, characterized in that the gas injection device comprises a gas pressure boiler. Apparatus according to claim 14, 15 or 16, characterized in that the sludge pumping device has an exhaust which opens near the surface of the water.