HRP950461A2 - Process and device for separating a hydropholic liquide fraction of an aqueous suspension - Google Patents

Description

This invention relates to a process for separating a hydrophobic liquid fraction from an aqueous suspension, as well as a device for carrying out this process.

When oil fields are opened, as well as during oil extraction, mixtures of fine-grained substances such as stone flour, sand, grains, etc. with oil and water appear. These mixtures can exist as sludge for a long time and are introduced into various processing procedures. One mixture of this type contains a characteristic proportion (ratio) of solid particles in oil by weight. ratio from 1.5 to 1.7. The rest of the mixture is water, with a relatively high content of petroleum products of at least 8% by weight. Sludge of this type, which can be described as a suspension, contains up to 40% by weight of a hydrophobic liquid fraction, eg petroleum.

In the USA, sludge of this type was previously mixed with agriculturally usable land, in order to reduce the total oil content, which resulted in the decomposition of oil products into CO2 and protein by the action of aerobic microorganisms. The use of such procedures is, in principle, limited to those areas that have only small amounts of precipitation, in order not to endanger groundwater.

In order to reduce the total amount of sludge that settles when washing a well or the like, it is separated from coarse particles, for example through a sieve. a centrifuge or the like drains back. Closed or almost closed systems are very expensive in terms of energy consumption, so they are used only in exceptional cases and in rare locations.

The proven practice for the treatment of mud (sludge) or the like consists in the fact that the mud in large basins begins to be separated from the oleophilic and hydrophilic components by a slow process and simultaneously achieves the separation from the water. This is done in such a way that the sludge is placed in tanks, for example in sealed and controlled tanks, and then covered with a layer of water, which is also brought from another basin through analogous processing. Due to the force of gravity, sedimentation of the sludge takes place, and the sediment still contains finely divided oil products. Due to the surface tension of oil products, larger drops are formed over time, which, due to the difference in specific gravity compared to water, will float to the surface. Such separation is also carried out by anaerobic fermentation in the sediment, whereby pit gas or the like is formed, which, due to the particularly large difference in specific gravity compared to water, can rise more easily than oil droplets and thus creates pores or channels along which they can climb oil products. On the surface, the oil is sucked off and freed from water, and is brought to industrial plants for oil processing. Depending on the requirements, storage can be carried out for a long period of time, even years, whereby the hydrophobic phase in the sludge or in the sediments is always gradually separated. Likewise, depending on the requirements, after analyzing the average composition of the sediments, the water that is above can be separated, and the sediments, which as a rule have a minimum content of 15 wt. % of oil products are taken to special landfills. Such landfills must meet special requirements. So, for example, they must not be connected to the groundwater level in the area. These conditions are particularly fulfilled by salt mines, because such salt deposits have been durable (permanent) for millennia due to the fact that there was no connection to water sources, which would cause salt leaching in a shorter time.

The subject invention is based on the above-mentioned state of the art.

The next phase of the technique is stated in US-A-4,851,123, which describes the processing of waste materials from an oil refinery, where these waste materials contain 8% by weight of oil, lubricating grease, etc., and the rest is water. A mixture of this kind is intensively stirred, and the suspension that stands above the solid substance settles. A flotation liquid is added to the decanter, which creates foam, after which compressed air is introduced. The foam that collects on the surface contains a large part of the oil from the sludge.

The aim of the present invention is to obtain a process and a device for separating a hydrophobic liquid fraction from an aqueous suspension, whereby, despite a small investment in machinery as well as a small energy and personal investment (effort), the separation of the hydrophobic phase of the suspension can be carried out, so that it can lead to a landfill harmless to the environment and where further natural microbiological decomposition would take place.

The method according to the present invention for separating the hydrophobic aqueous fraction, especially oil, petroleum distillates or the like, from an aqueous suspension with a hydrophobic liquid fraction content of 10 wt.% to 40 wt.%, especially 15 wt.% to 25 wt.%, if necessary 18 wt.% to 22 wt.% and sedimentary fractions, e.g. stone flour from 25 wt.% to 40 wt.%, where the aqueous suspension is stored in one tank with the addition of water as necessary to the pool, and hydrophobic liquid is extracted from the surface of the water fraction, and water is removed from the aqueous suspension, consists mainly in mixing the suspension with water again in the tank, and extracting the hydrophobic liquid fraction from the surface of the water, after which water is removed from the suspension that has a small portion of the hydrophobic liquid fraction , and also the content of the hydrophobic liquid fraction is broken down again in the suspension.

Aqueous suspensions of this type are formed within the oil industry at various stages of the process and have a typical ratio of solids to oil or similar from 1.5 to 1.7. Compounds of this type are created, for example, during the opening of oil fields, at wells or also at transport openings during oil transport, washing of oil probes, but also in operation during oil processing.

The sedimentary fraction, eg stone flour, petroleum coke, silty earth or the like, can no longer be extracted as a rule, or at least not to a large extent, so that this inert substance can be brought back without danger. The proportion of water, which due to natural reduction is constantly decreasing due to evaporation due to water vapor pressure, can as a rule be used in a circular flow (circulation) for further processing of waste material. Only the part of the sludge, which has an excessive content of hydrophobic liquid constituents, must be subjected to further processing. Due to the large quantities of sludge particles of this type, a relatively simple procedure can be carried out with relatively low costs. Sludge of this type can be thermally inertized, but the overall cost for energy and subsequent purification of gases is so high that there is a fear of major pollution of nature, for example by removing filter ash, filtering residues, etc. There is also the possibility of extracting the sludge with the content of the hydrophobic liquid fraction with organic solvents, whereby the hydrophobic components must then be freed from the organic solvents. Such procedures are quite expensive and cannot be used for larger amounts of resulting suspensions. It was found that through simple stages of the procedure, i.e. by re-mixing the suspension with water in the tank and finally extracting from the hydrophobic liquid fractions that floated to the surface, and in the last stage by carrying out the dehydration process of the suspension, it can eventually lead to an extremely strong separation of the hydrophobic liquid fraction. The thus obtained granular suspension, which in principle has a low water content or the rest of the suspension, can for example be microbiologically degraded due to the low hydrocarbon content.

If the suspension is mixed with water with a jet of gas or especially air, very good mixing can be achieved, while at the same time due to gas bubbles, for example in the suspension, pores with the smallest cross-section approximately corresponding to the gas bubble are formed, which can be used for further separation from hydrophobic liquid components. Air also gives the advantage that fermentation can be carried out, for example facultative aerobic fermentation, whereby gases are also usually formed as products of substance exchange, which, together with hydrophobic liquid constituents, can rise to the surface of the water above.

If the gas, especially air, is introduced into the suspension in pulses, preferably with a pressure of between 5 and 10 bar, lasting preferably from 1 to 5 seconds, a simple mixing of the suspension with water can occur, and due to the time limitation, melting of oleophilic drops, so that they can join together faster and thus float unhindered on the surface of the water.

If gas, especially air, is introduced through gas lines placed in the suspension and/or under the suspension, a simple and flow-friendly pore formation in the suspension can occur, which, due to the fact that the gas can escape even with low pressure, favorably affects the connection of hydrophobic drops in suspension.

If the gas, and especially the air, is heated to 40°C to 50°C before introduction, this increases the buoyancy of the gas within the suspension or water, while at the same time the suspension can be heated, and thus a significant increase in the fermentation of micro- organisms in suspension, whereupon the surface tension of individual oleophilic droplets within the suspension falls, so that their connection occurs, and thus they climb to the surface more quickly.

If the gas, especially air, is introduced into the suspension via supports placed along the surface of the water, preferably via rafts, then only in the case of large tanks or basins can a discontinuous supply of gases occur, whereby a small construction cost must be kept, in order to be able to achieve necessary mixing in all areas of the tank or pool in a very simple way. If the suspension that floats to the surface of the water is returned to the suspension located at the bottom of the tank, e.g. via a mud pump, together with air if necessary, a strong separation of the suspension between the hydrophilic and hydrophobic components can occur, while at the same time through the repressed of the suspension enhances mixing.

If, after the separation of the hydrophobic liquid fraction is completed, water is withdrawn, especially through the liquid lines placed under the suspension, the release of the suspension from water can be carried out, whereby the total weight of the fraction subjected to post-treatment can be kept small, thus ensuring the recommended water regime.

If the suspension, from which water has been extracted, is deposited in embankments that can be turned, preferably mechanically, aerobic fermentation of the partially dry suspension can occur, whereby modern technologies can be used, such as turning (plowing) embankments with mechanical devices, placing embankments on watertight beds, floors or the like.

If the suspension, from which the water has been extracted, is mixed with structural materials, e.g. with straw, bark or the like, a fairly simple supply of oxygen-containing air can be ensured due to the existing structures, whereby the products formed by the exchange of substances are effectively exposed, e.g. CO2, pit gases, etc.

If the suspension is mixed with microorganisms, especially with supporting substrates of microorganisms, e.g. wooden panels of transport devices or the like, where microorganisms break down liquid hydrophobic substances, the recommended decomposition of specific oil or the like can be achieved, whereby as a rule, microorganisms specially intended for special hydrocarbons are used.

A particularly recommended form of performance consists in mixing the suspension with greenery, eg grass, twigs of bushes. As a rule, green plants have thermophilic microorganisms that lead to accelerated decomposition at elevated temperatures. In this way, the recommended drying of the substrate can be carried out on the one hand, where, due to the elevated temperature, the accelerated decomposition of oleophilic components is carried out using the same decomposing microorganisms, assuming that only the separate surfaces that are connected to the greenery, have an elevated temperature of 60°C to 70ºC.

If nitrogen sources are mixed into the suspensions, then there is an excessive supply of carbon with regard to decomposition by microorganisms and the creation of its own substance in the body in a particularly suitable way.

The device according to this invention is based on the task of constructing an ecological device for the processing of substances containing oil and which could accept larger volumes, and with which, with a low consumption of labor and energy, large quantities of suspensions polluted by hydrophobic substances could be processed.

The device according to this invention for separating the hydrophobic liquid fraction, especially oil, oil distillates or the like, from the water suspension with the pool, which has at least one waterproof layer with loam, plastic material or the like, which has layers of gravel and/or flint sand and the device for removing the surface layers consists mainly in the fact that there is a line for extracting liquid and/or a line for supplying gas in the gravel and/or flint sand. A device of this type can, in a very simple way and in a way that does not pollute the environment, enable the storage of suspensions containing petroleum products, while also enabling the extraction of liquid in a simple way, that is, the extraction of water from the substrate and the introduction of gas, which enables the coalescence of oil droplets or similar

If a raft is provided, which is mobile along the surface of the water and which carries a gas injection device and/or a mud pump, it is possible to mix the suspension evenly with water over the entire tank without large investments, whereby the mud circulation enables a deeper injection of the suspension with the bottom, and the decomposition sludge that floated to the surface is returned to the suspension and used to combine with other oleophilic suspension droplets.

If the gas injection device has a gas pressure vessel, then larger quantities of gas can be expelled in a short time under high pressure, which achieves particularly good mixing of the suspension with water.

If the mud pump device has an extraction device, which plunges into the water surface, then very simply the suspension that has surfaced, which for example contains gaseous particles, can be returned to the suspension located at the bottom.

Furthermore, the device will be explained in more detail using drawings and examples.

The pictures show:

Sl. 1 section through the basin i

Sl. 2 section between two adjacent embankments.

The pool shown in Fig. 1 has a synthetic foil 1 made of polyethylene with a thickness of 2 mm. Below and on each side of that foil is a layer of clay 2 with an average thickness of at least 60 cm. Under the foil 1 and the clay layer 2, suction pipes 3 are placed, which serve to indicate the eventual release of liquid from the pool 4. At the bottom 5 of the pool 4, a layer of gravel 6 is placed, in which lines 7 for water suction are provided. These lines have perforation along their entire length, so that water can be sucked out along the entire bottom 5 of the pool 4. Above the gravel layer 6, a fine-grained layer 8 is placed, in which the air pipes 9, which are also perforated, are placed.

Above both of these layers 6 and 8, which have ca. 25 cm layer thickness, deposited suspension 10 was placed, and that in a layer thickness of approx. 300 cm. A raft 12 floats on the surface of the water 11, which can be dragged along the surface by means of pulleys that are not shown. An air injection device 13 (injector) and a mud pump 14 are provided on the raft 12. The air injection device 13 has a pressure vessel with a capacity of 150 l filled with air compressed to 10 bar, which is discharged towards the bottom in the form of a jet within one second. The valve opens automatically when a pressure of 10 bar is reached. Air injection devices of this type are known from storage technology in silos, for example for separating piles of grain from the silo wall.

The mud pump 14 sucks in the surface area the mud stirred up by the air injection device and then presses it back into the suspension 10. The surface separation device 15 has a hose 16, which is hydrophobic and which moves on the water surface 11 and accepts the hydrophobic fraction that has floated out. Between the two rollers 17, the hose is crushed (squeezed out), and the hydrophobic phase, usually oil, is fed through the pipeline 18 to the intermediate tank. After the buffer, the extracted liquid is led to a separator, where further separation of the oleophilic and hydrophilic phases is carried out. The oleophilic phase is then taken to the usual processing in the refinery. A pool of this type usually has a capacity of, for example, 15,000 m3, where the sludge layer or suspension layer amounts to approx. 300 cm, and the water layer is approx. 100 cm.

Fig. 2 shows embankments 19 made from oil-enriched suspension, which has a granular composition and into which straw and bark are mixed. These embankments have a width b of 300 cm and a height h of 170 cm. If desired, substances, such as green plants, etc. from agricultural goods, from parks, such as grass, leaves of bushes, can be easily mixed into these mounds, in order to achieve an increase in temperature for further fermentation. The embankments are placed in such a way that modern overturning devices can be used.

Example 1

10,000 m3 of suspension with the following composition is placed in the pool according to Fig. 1:

18.0 wt.% oil (2,135.2 t)

30.0 wt.% stone flour (3,558.6 t)

52.0 wt.% water (6,170.0 t)

This mixture is covered with ca. 3,000 m3 of water from the neighboring pool, from which the water was extracted.

During storage, a weak anaerobic fermentation occurs in the suspension layer, whereby ca. can be extracted during 10 years. 390 tons of oil. After extracting the water, the suspension is stored on the sloping side of the pool and has the following composition:

15.2 wt.% oil

31.0 wt.% stone flour

53.8 wt.% water.

In the course of 10 years, only approx. 20 wt.% of oil from the subject suspension.

Example 2

10,000 m3 of suspension according to example 1 is placed in a pool constructed analogously to that in example 1 of the same capacity and dimensions. This sludge is covered with a layer of 3,000 m3 of water. Then above the pool, which has a surface area of 25m x 120m, a raft is placed on which the air injection device and mud pump are mounted. The air injection device moves forward and back in the transverse direction of the pool at a speed of 2 m per minute, during which the pulsed air injection of 1 m3 per minute at a pressure of 10 bar intensively mixes the water with the suspension deposited on the bottom. During the storage of the suspension in the pool, air is supplied through the air ducts located at the bottom in the amount of 60 m3 per m2 and hour. The air warmed to 40°C to 50°C. The suspension that has floated to the surface of the water is drained via a circulation pump together with air into the suspension.

In 60 days, 1,801 t of oil is extracted from the surface. Then the water that is above the suspension is extracted by lines placed below the suspension and dried with the supply of heated air, especially at 40°C to 50°C. The pre-dried suspension thus obtained has the following composition:

6.0 wt.-% oil

64.0 wt.-% stone flour

30.0 wt.-% water.

This suspension is mixed with ca. 1 wt.% of straw and approx. 4 wt.% of green leaves of bushes. Pieces of wood from the drilling boards, which have microorganisms, were also mixed into the green plants. Wooden boards of this type are used for well openings. This thus obtained mixture has the following composition:

5.70 wt.% oil

60.95 wt.% stone flour

28.55 wt.% water

0.95 wt.% straw

3.85 wt.% of green plants.

This mixture, which was initially completely liquid and became granular over time, is deposited in embankments measuring 300 m wide and 170 m high. After five weeks, the mixture had the following composition:

2.4 wt.% oil

69.5 wt.% stone flour

25.2 wt.% water

2.9% by weight of straw and green plants.

During fermentation, the mixture is transformed at three-day intervals, due to which homogenization and ventilation occur.

Fermentation is carried out for the next eleven months, during which the material is converted in the mound at weekly intervals and moistened for approx. 15% by weight of water, if necessary. The mixture then has the following composition:

0.8 wt.% oil

84.8 wt.% stone flour

15.4 wt.% water.

Again, approx. 98.5 wt.% oil or it turns into microorganisms and carbon dioxide.

If there is too little nitrogen, both in the sludge and in the embankment, other substances can be added.

The oil content in certain fractions is determined by extraction with n-heptane. The proportion of sedimentary substances is determined by filtration and annealing of waste substances (residues) under the influence of oxygen at 650°C. At that temperature, microorganisms as well as straw and green plants are oxidized. Green plants and straw are determined by filtration, where the filter pore diameter is so dimensioned that, in addition to oil, water and sediments also reach the filtrate.

Instead of air, other gases can be used, such as those produced during combustion, as well as oxygen-enriched air.

Although mixing the suspension with a gas jet enables intensive mixing of the suspension with water and at the same time facilitates the binding (joining) of oleophilic droplets, other mixing devices are also used, e.g. mechanical mixers, as well as mammoth pumps, with which the suspension is extracted from the bottom and fed into swimming pool.

Although the invention is explained using petroleum products, it is also suitable for other oleophilic substances, which appear in a mixture with a solid substance and an aqueous phase, usually water. The assumption for the use of the present invention is that the suspension has a high viscosity, so that it is difficult for the oleophilic droplets to coalesce. Examples of such oleophilic substances include linseed oil, peanut oil, etc. For sediments, examples include soot, chalk, clay, solid ion exchangers, dust, etc.

Claims (17)

1. The method according to this invention, for separating the hydrophobic aqueous fraction, especially oil, petroleum distillates or the like from an aqueous suspension with a hydrophobic liquid fraction content of 10 wt.% to 40 wt.%, especially 15 wt.% to 25 wt.% , if necessary 18 wt.% to 22 wt.% and sedimentary fractions, e.g. stone flour from 25 wt.% to 40 wt.%, where the aqueous suspension is stored in one tank, preferably a basin, from the surface of the water with the addition of water extracted by the hydrophobic liquid fraction. and water is removed from the aqueous suspension, indicated by the fact that the suspension is again mixed with water in the tank, and that the hydrophobic liquid fraction is extracted from the surface of the water, after which the suspension, which has a small portion of the hydrophobic liquid fraction. it takes away water, and also the content of the hydrophobic liquid fraction is broken down again in the suspension. 2. The method according to claim 1, characterized in that the suspensions are mixed with water using a gas jet, preferably an air jet. 3. The method according to patent claim 1 or 2, characterized in that the gas, especially air, is pulsed into the suspension, preferably with a pressure of 5 to 10 bar, for a duration of 1 to 5 seconds. 4. The method according to patent claims 1, 2 or 3, characterized in that gas, especially air, is introduced through gas lines placed in the suspension and/or under the suspension. 5. The method according to one of the patent claims 1 to 4 characterized in that the gas, especially the air, is preferably heated to 40°C to 50°C before introduction. 6. The method according to one of patent claims 1 to 5, characterized in that the gas, preferably air, is introduced into the suspension via carriers that pass along the surface of the water, preferably rafts. 7. The method according to one of the patent claims 1 to 6, characterized in that the suspension that floats to the surface is returned to the suspension located at the bottom of the tank using, for example, a mud pump, if necessary together with air. 8. The method according to one of the patent claims 1 to 7, characterized in that after the completion of the separation of the hydrophobic liquid fraction, water is extracted via liquid lines placed under the suspension. 9. The method according to one of the patent claims 1 to 8, characterized in that the suspension, from which the water has been extracted, is deposited on embankments, which are moved mechanically. 10. The method according to one of claims 1 to 9, characterized in that the suspension from which the water is extracted is mixed with structural materials, for example with straw, bark or the like. 11. The method according to one of the patent claims 1 to 10, characterized in that the suspension is mixed with microorganisms, especially with supporting substrates of microorganisms, e.g. wooden boards, which break down the liquid hydrophobic fraction. 12. The method according to one of claims 1 to 11, characterized in that the suspension is mixed with green plants, eg grass, bushes. 13. The method according to one of claims 1 to 12, characterized in that nitrogen sources are supplied to the suspension. 14. Device for separating the hydrophobic liquid fraction, especially oil, oil distillates or the like, from an aqueous suspension, especially according to one of claims 1 to 13, with a tank (4) having at least one waterproof layer (1, 2), e.g. with loam, plastic material or the like, on which a layer (6) of gravel and/or flint sand is placed and a device (15) for removing surface layers for layers on the surface of the water and/or one layer that floats on them, indicated by that a line for liquid suction (7) and/or gas supply (9) is placed in the gravel and/or flint sand. 15. Device according to claim 14, characterized in that a raft (12) is provided, which is movable along the surface of the water (11), and which carries a device for gas injection (13) and/or a mud pump (14). 16. Device according to patent claim 14 or 15, characterized in that the gas injection device (13) has a gas pressure vessel. 17. Device according to claim 14, 15 or 16, characterized in that the sludge pumping device (14) has a suction device that immerses in the water near the surface.