EA005875B1 - Oil sands separation process - Google Patents

Abstract

Oil bearing sands recovery process is described comprising a main separation stage. The oil bearing sands is slurried in the main separation stage with water to produce an enriched fraction and a dilute aqueous clay waste. The aqueous clay waste is sedimented in a waste sedimentation stage in one or more settling lagoons to provide a substantially solid clay sediment and supernatant. The dilute aqueous clay waste is fed into a well and flocculated by addition of a polymeric flocculant. The flocculated dilute aqueous clay sediments to provide a pumpable thickened clay sediment layer in the base of the well.

Description

The present invention relates to a method for extracting valuable components from tar sand, comprising a main separation step and a waste sedimentation step. The purpose of the invention is to find a new and effective approach to the treatment of waste generated in the form of sediment in the installation for the processing of bituminous sandstone.

Bituminous sandstones (also called oil sands or tar sands) are sandy sediments saturated with dense, viscous oil. Bituminous sandstones are found throughout the world, often in the same geographical areas in which conventional oil deposits are located. The largest and only commercially interesting tar sands deposit is located in Canada in the Athabasca region in the northwestern part of Alberta province. The reserves of bitumen in this field are estimated at between 700 billion and 1 trillion barrels. Most of the deposits of these tar sands are located on the surface of the earth or very close to the surface of the earth, where their extraction and processing into synthetic petroleum feedstock does not present any particular problems. Commercial large-scale extraction and processing of tar sands is carried out near Fort McMurray, Alberta.

Athabasca tar sands are a three-component mixture of bitumen, minerals and water. A valuable component of this mixture is bitumen, for the extraction of which the tar sands are actually being developed and processed. The content of bitumen in tar sands found in this region varies around an average of about 12% by weight, but can vary from 0 to 18% by weight. The water content in the above mixture usually ranges from 3 to 6 wt.% And generally increases with a decrease in the content of bitumen in this mixture. The content of mineral components in the mixture is at a relatively constant level and ranges from 84 to 86 wt.%.

Currently, there are several main methods used for many years to extract bitumen from sands containing it, the most important of which is the hot water treatment method. It should be noted that the present invention is not limited to any particular method of separating bitumen from sands containing it, and therefore the following description of one of these processes is for illustrative purposes only. The hot water treatment method for the primary extraction of bitumen from tar sand consists of three main technological stages (fourth stage, final extraction stage, used to clean the extracted bitumen during the sequential processing of raw materials). In the first stage, called conditioning, tar sand is mixed with water and heated with live steam to form a suspension with a solids content of from 70 to 85% by weight. Then, sodium hydroxide or other reagents are added to the resulting suspension in the required amounts to establish and maintain its pH at a level of 8.0-8.5. In the second stage, called separation, the conditioned suspension is further diluted, due to which it can be stratified. At the same time, the predominant part of the mineral components precipitates quickly, the particles of which have a size characteristic of sand particles and which are removed in the form of sandy tails. Much of the bitumen quickly floats to the surface of the water (as a result of separation of the suspension), forming a solid mass, known as a foamy product, which is removed from the remaining liquid in the sedimentation tank (sometimes also called the primary separation tank or separation chamber). Thereafter, a third stream, called the contaminated medium or separation phase, can be removed from the settling tank and treated in a third stage, the purification stage, to extract additional quantities of suspended bitumen.

As indicated above, the conditioning of tar sands to extract bitumen from them consists in heating the initial mixture of tar sand with water to an operating temperature (180–200 ° E), in physically mixing the suspension to obtain a homogeneous mass and a uniform consistency, and in spending chemical reaction) of caustic soda or other reagents added to the suspension. When processing in such conditions, bitumen is desorbed from individual grains of sand and mixed into the suspension in the form of discrete droplets, the size of which is of the same order of magnitude as the size of the grains of sand. It was found that the same operating or technological conditions are also optimal for the deflocculation of fine particles, in particular clay particles, which is a natural impurity present in the original bituminous sand. In this case, by deflocculation, or dispersion, is meant the destruction of the natural aggregates formed by clay particles, with the formation of a suspension of individual particles. In accordance with this, at the conditioning stage, a uniform dispersion of a significant part of the clay particles occurs and they are mixed with the suspension in its entire volume.

Thus, it is obvious to those skilled in the art that in the conditioning process tar sand, which is a fundamental step in preparing the raw material containing bitumen to efficiently extract bitumen from it at subsequent technological stages, clay particles also go into suspension, which pose significant problems. upon subsequent removal of tailings containing them.

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The second technological stage, called separation, is essentially a stage for the extraction of bitumen, since its separation from the tar sand occurs at the conditioning stage. At this second stage, the suspension of conditioned tar sand is first passed through a sieve to separate large pieces of rock and unconditioned lumps of tar sand and clay from it and the rejected material (lump material) is sent to waste. Then, the suspension passing through the sieve is further diluted with water in order to speed up the process of separation of the suspension into two main phases, one of which is formed by droplets (globules) containing almost no mineral bitumen components, which rise to the surface of the water in the separation chambers and form a solid mass of foamy product on it, and the second is formed by particles of mineral components, in particular particles of mineral components, the size of which corresponds to the typical size of sand particles and which, after settling to the bottom of the sand zdelitelnoy chamber is removed therefrom in the form of tailings. The medium that remains between these two phases, resulting from the separation of the suspension, and through which, during the separation of the suspension, these two phases move (one up and one down), is called the middle or separation phase. This middle phase consists mainly of water with finely dispersed solid particles and bitumen particles suspended in it.

Sand and bitumen have relatively constant particle sizes and densities. The parameter that has the main influence on the suspension stratification process is the viscosity of the middle or separation phase, and its viscosity in turn directly depends on the content of fine particles in it. Usually, with an increase in the content of such fine particles above a certain threshold value, which varies depending on the composition of these fine particles, the viscosity of the middle or separation phase quickly reaches high values, as a result of which the suspension stratification process almost stops. Such a working condition of the separation chamber is figuratively called its disorder. In this working state of the separation chamber, the amount of bitumen extracted from tar sand is insignificant or even zero, and all the flows coming out of the separation chamber have approximately the same composition as the feedstock loaded into it. For this reason, in order to maintain the viscosity of the medium or separation phase within the allowable limits for effective delamination of the suspension as the content of fine particles in the feedstock increases, the amount of water used in the process must be increased.

The third stage of the hot water treatment method is cleaning. The content of fine particles in the feedstock determines the need for the water used in the suspension process, which is necessary to maintain the viscosity of the middle or separation phase within the required limits, which (viscosity) depends on the ratio between clay and water. To maintain the material balance in the separation chamber, it is necessary to remove from it a stream of contaminated medium or separation phase, which can be further cleaned to extract additional quantities of bitumen from it. An effective method of cleaning such a stream of medium or separation phase is flotation in a pneumatic flotation machine.

The final extraction or purification of the froth product is usually carried out by centrifugation. In this case, the foam product obtained during the initial extraction of bitumen from tar sand is diluted with ligroin and then the diluted foam product is subjected to a two-stage centrifugation. As a result of this process, a practically pure product is obtained which is diluted bitumen. Separated from the foam product at this stage, water and mineral components form a stream of additional tailings that must be removed.

Such tails represent, if we use the terminology adopted in the technology of extraction processing, the material unsuitable for further use, which is formed in the process of extracting valuable materials from ore. The tails formed during the processing of tar sands consist of the whole ore body of tar sand and the total amount of water added during the process, with the exception of only the product extracted from the sand, which is bitumen. The tails formed during the processing of tar sand can be divided into three categories, namely: (1) for oversize material, (2) for coarse-grained or sandy tails (fast settling fraction) and (3) for sludge consisting of fine particles or tails (slowly settling fraction). Hite material is usually collected and removed from the process as a separate stream.

Currently, given the high level of environmental awareness in Canada, the United States and other countries, increasing attention is being paid to finding an industrial solution to the problem of removing tailings formed during the development and processing of tar sands, as well as to various other processes associated with the mining and processing of ores . Removal of tailings formed during the processing of tar sands does not cause any particular difficulties. When extracting one cubic foot of tar sand in the rock, a cavity remains, the volume of which is also equal to one cubic foot. As a result of the subsequent processing of the ore to extract from it the fraction containing bitumen, a residue is formed, which consists of technological materials and waste rock and which represents tails that do not represent any value and which must be eliminated. In the processing of tar sands, the main technological material

- 005875 Scrap is water, and waste rock is mainly sand with some silt and clay. From a physical point of view, the tails (with the exception of the suprate material) are partly composed of solid material (sandy tails) and partly of more or less liquid material (sludge). The optimum location for such waste is, obviously, the same cavity of one cubic foot, which remains in the rock as a result of tar sand extraction. However, the sandy tails alone, remaining after processing one cubic foot of ore, occupy a volume that is also approximately equal to one cubic foot. The amount of sludge in the waste varies depending on the quality of the ore and process conditions, but is usually about 0.3 cubic feet. Thus, the tails simply do not fit in full in the same cavity that remained in the rock after extracting tar sand from it.

The data obtained during the commercial development of tar sands suggests that a layer of sludge gradually accumulates at the tailings storage site, the process of sedimentation and compaction of which proceeds, if at all, proceeds, exceptionally slowly and lasts several years. For a variety of reasons, such a layer of sludge, which has much in common with similar layers of sludge accumulating in tailing ponds, where tailings formed in a wide variety of mineral extraction and extraction processes, takes on special significance and is difficult to handle. One of the methods for removing tailings is the construction of dams from them, for which they are hydraulically transported to the place of their storage and dumped onto the top of a sand dam built as a kind of dam for fluid accumulating in the space confined by it. On the dam, sand quickly settles, and a suspension of fine particles, water and small amounts of bitumen flows into the tailing pond. The settling sand is mechanically compacted to strengthen the dam as its height increases. Suspension, which flows into the tailing pond, begins to stratify, which can take from several months to several years.

Another method for removing tailings is to dump them directly into the liquid in the tailing pond by throwing them over the top of a sand dam. In this case, fast and slow precipitation processes can occur, but the differences between them are not as clearly expressed as when removing the tailings by building dams from them, and the tails are not subjected to mechanical compaction. The sand present in the tails quickly settles to form a layer of gentle alluvial material that extends from the point of tailings discharge to the inside of the tailing pond. After the sand has settled in the tailing pond, a long process of separation of the suspension into fine particles and water begins.

Tails formed during the processing of tar sand with hot water are a dilute suspension of fine particles in water, which, together with the sand, is discharged into the storage pond. The formation of sludge as a result of the separation of such a suspension of tails is due primarily to the presence of clay minerals dispersed in them. The sedimentation rate of these clay minerals, as well as the properties of the resulting sludge, depend on many factors determined by the conditions of tailings discharge into the tailings pond. Such factors include the initial clay concentration (the ratio between clay and water), the relative ratio between different types of clay minerals, the size of clay particles, the state of the surface of clay particles, and the chemistry of pore water. Experiments and laboratory studies show that all these factors are subject to significant periodic fluctuations depending on the composition of the tar sands and on the technological conditions of the process of their processing.

Usually, when they are dumped, the tails fall on the surface of the alluvial material (either directly or as a result of slipping from the dam), where most of the sand settles. At the same time, the waste continuously flows into the liquid-filled pond-tailings pond or sump, from which water is simultaneously taken as recycling material, which is returned back to the extraction process of bituminous sands to extract bitumen from them. At the same time, a number of additional important factors influence the nature of the sludge deposition process. These factors include the flow rate in the pond-tailing and the discharge from it in terms of the area of the reservoir ponds, the volume of clarified water, the depth of the tailing pond and the degree of mixing of its contents, which occurs under the influence of input or output exposure to wind. In this regard, it should be noted that, unlike the initial temperature, which is characteristic of tailings flows into the settling tank and which has a more or less constant value, the temperature of the contents of the tailings pond depends, obviously, on many different factors.

In the case when the partially settled sludge remains in a relatively deep prudovostoyazvoditelny in a calm state for a period of time ranging from several months to about two years, it is divided into two distinct layers, namely, a layer of almost pure water on top and located under it is a layer of sludge. The density of the sludge layer gradually increases in the depth of the tailing pond, which is mainly due to the increase in the number of sand and silt particles in the depth of the tailing pond. Because of the high yield strength of the stagnant sludge, such particles do not settle to the bottom of the tailing pond at all or only

- 3 005875 very slowly. The ratio between clay and water increases along the depth of the ponds of the storage pond only slightly in its upper part and practically does not change in its lower part. After one or two years, the volume of the sludge layer subsequently changes only slightly. The process of sediment compaction at the bottom of the tailing pond proceeds so slowly that it is quite difficult to analyze the amount of compacted material. Formed in such conditions, the sludge remains almost unchanged for several years or even decades, and from the point of view of its possible practical application can be considered as a completely formed sludge.

A more complex system is an active tailing pond with a continuous flow into it and the selection of streams from it. After the tailings are dumped into such a tailing pond, the aging of the clay particles present in them begins, which can last from several days to several weeks. Clay particles do not settle to the bottom of the tailing pond until the completion of such an aging process. However, having begun, the process of sedimentation of clay particles proceeds fairly quickly in accordance with Stokes’s law until the ratio between clay and water reaches approximately 0.13: 1, after which other factors clearly begin to prevail over Stokes’s law. As a result of similar effects in the uppermost part of the tailing pond, operated in compliance with all established rules and requirements, an upper layer of more or less pure water and a layer of relatively diluted sludge with a more or less clearly defined boundary between them are formed. Such a layer of diluted sludge can be called a sedimentation zone, the volume of which is determined by the flow of clay entering the tailings pond and the necessary average time for its aging. With a decrease in the ratio between the volume of the water layer and the flow of clay entering the pond-tailing, the amount of water taken from it and the aging time of clay to a too small value in the upper part of the tailing pond there is an overload, the layer of pure water almost disappears, and the sedimentation zone increases significantly volume, since in this case the clay begins to recycle through the whole process.

The sludge located in the lower part of the deep active pond-tailing, operated for several years, is similar to the sludge formed in an inactive pond storage facility, i.e. it can be considered as a finally formed sludge. The space located below the sedimentation zone and above the layer of finally formed sludge can be designated as a transition zone that does not have a clear upper and lower boundaries. The presence of such a transition zone, which is characterized by a gradual decrease in the ratio between clay and water along the depth of the tailing pond, is due to the long period of time necessary for the slurry to reach the state of a finally formed slime. The thickness of this transition zone is mainly proportional to the average consumption of clay flowing into the pond-tailing, referred to the volume.

In general, in the active tailing pond with its proper operation, there is usually a top clearly defined layer of pure water, which, however, disappears during the above-described overload. Under this layer of water is a layer of sludge, the density of which increases along the depth of the tailing pond. Usually there are no clearly defined boundaries over the thickness of this sludge layer, except for the case when a layer of released bitumen is present near the interface between the sludge layer and the water layer. At the same time, the sludge layer can be considered as consisting of three zones, the duration of measurable sludge dewatering in each of which gradually increases by an order of magnitude with the distance from the surface of the tailings pond and for each of which the prevalence of various sludge dewatering parameters is characteristic. These three zones can be designated respectively as a sedimentation zone, a transition zone and a zone of finally formed sludge.

Taking into account all the above, the need to search for long-term, economically and environmentally acceptable measures to remove sludge deposits, minimize their number or keep them permanently continues in this area. Solving this problem requires a versatile approach, in accordance with which the present invention proposes one of the possible ways to solve this problem, which consists in more thorough and effective dewatering of the sludge layer, which in turn eliminates the need to use active ponds at the same time as a solid waste disposal site. and as a place of water purification and thus allows you to store semi-solid or pasty waste in the place of their initial placement.

One of the well-known from the prior art and widely used in practice methods to improve the characteristics of the process of settling of tailings in industrial ponds-tailings is flocculation of tails flow. In the process of flocculation, individual particles are combined into relatively weakly bound agglomerates or flakes. The degree of flocculation is determined by the probability of collision of particles and their tendency to stick together when colliding between themselves. At the same time, the probability of collision of particles increases with mixing, and the addition of flocculant to the medium containing them increases their tendency to stick together.

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The action of reagents with flocculant properties is based on one of the three main mechanisms or on their combination, which consist of: (1) in neutralizing electrical repulsive forces in the space surrounding small particles, so that after their collision the particles are held in an interlocking state der-Waals forces, (2) in the deposition of bulky flakes, such as metal hydroxides, which trap fine particles, and (3) in the binding of particles due to the formation of bridge bonds using Natural or synthetic long chain high molecular weight polymers. The action of such polyelectrolytes is presumably based on the absorption (as a result of ester formation or hydrogen bonding) of hydroxyl or amide groups on the surface of solid particles, as a result of which each polymer chain bridges several solid particles together in suspension.

In accordance with the prior art, flocculating agents were used in various industrial processes for the deposition of solid particles in tailing ponds, as well as in wastewater treatment plants. However, significant progress in this area was achieved with the use of hydrolyzed corn and potato starch as flocculants. Such special flocculants based on hydrolyzed starch (obtained by hydrolysis of starch under the action of water in the presence of one or more metal salts), taking into account, in particular, the economic aspects associated with flocculation on a large scale, are highly effective means capable of providing rapid sedimentation of solid particles with bringing their state to a state substantially corresponding to the state of the finally formed sludge. This property of these flocculants is particularly valuable for their use in those processes in which the need to return purified water back to the production cycle is important and as an example of which the process of extracting bitumen from tar sand with its hot water treatment can be called. However, experience shows that the simple use of such flocculants based on hydrolyzed starch or any other flocculant known for its use for the same purpose only leads to a very slight improvement in the final degree of dehydration of the sludge layer, or even does not lead to such an improvement. In other words, the sludge layer in its final state with the use of flocculant does not substantially differ from the sludge that would have formed over a longer period of time as a result of the natural sedimentation process, and in this final state has unsatisfactory properties that are too high. its content of water, its too large volume and too high its instability.

At the same time, it would be incorrect to state that all the properties of the sludge layer resulting from flocculation using the above-described flocculants based on hydrolyzed starch completely coincide with the properties of the sludge layer resulting from the natural process of settling or using other flocculants. In fact, the use of flocculating agents based on hydrolyzed starch makes it possible to impart several very useful properties to the resulting sludge layer, which cannot be obtained when a sludge layer is formed as a result of a natural sedimentation process or when other currently known flocculants are used, and therefore the present invention is based on the recognition and use just these facts. During the creation of the invention, it was found, in particular, that when using special flocculants, the permeability of the sludge layer and its shear resistance increase significantly, which makes it possible to use for compaction and stabilization of the sludge layer, as well as to extract additional quantities of purified water technology of its dehydration, the use of which was previously impossible.

Another previously proposed approach to solving the problem of water purification in the ponds of the tailings ponds is based on the storage of fine fractions in the voids between the grains of sand in the material used for the construction of dams. A similar method is described in patent CA 1063956, entitled MS11yub οί 81ibds B18ro8a1 B1a1sb Yu 11c But! \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ ί 8 Tag 8Aybz and issued on October 9, 1979, and in the corresponding patent I8 4008146, issued on February 15, 1977 The problem that was addressed by the method described in these publications is that the height , to which a dam can be poured, is to a certain extent limited, however, when used to prepare material for the construction of a dam mixed with sludge sand, processed by the above-mentioned flocculants based on hydrolyzed starch, the strength of the material obtained is significant increases, thus increasing the height of the poured material of the dam, and as a result, not only increase the depth prudahvostohranilischa surrounded by a dam, but also to store a greater amount of sludge in the voids between the grains which make up this dam.

The literature describes many proposals aimed at accelerating the process of sedimentation by flocculation of clay waste, as well as proposals aimed at improving the structure of solid clay sediment by adding sand or other materials to clay waste. As an example of publications that describe similar processes of extraction of minerals that use flocculating agents, we can mention the patents I8 3418237, I8 3622087, I8

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3707523, IZ 4194969, IZ 4224149, IZ 4251363, IZ 4265770, IZ 4342653, IZ 4555346, IZ 4690752, IZ 5688404, IZ 6077441 and IZ 6039189, each of which is included in the present description by reference.

Despite numerous proposals for the use of flocculants in practice, it was found that their use is often not effective in terms of the costs involved. Even when using a flocculant to intensify the process of sedimentation and to obtain a reusable supernatant, its quality remains unsatisfactory because of its tendency to contamination by non-flocculating clay particles.

Thus, in particular, the main stage of separation of materials into individual phases or components often involves the use of processing chemicals, such as flocculants or, above all, flotation reagents, the effectiveness of which increases (and therefore the consumption required to achieve the desired result decreases) when used in separation of the flotation process or other similar water processes with clay particles suspended in it.

In order to minimize the contamination of the supernatant and increase its transparency, it is advisable to carry out sedimentation under conditions that ensure the formation of sediment at a considerable depth and thus the formation of a layer of supernatant liquid sufficiently large to allow it to be taken at a point remote to the maximum possible distance from the level of the sediment below it. However, to ensure compliance with such conditions in settling ponds is quite difficult, since they usually have a relatively small depth. This problem is further aggravated, in particular, as the settling pond is filled with practically solid clay sediment over many years and, accordingly, as its thickness increases continuously.

Another problem is connected with the necessity of optimal use of the areas occupied by already existing sedimentation ponds in order to avoid undesirable creation of new sedimentation ponds. For this reason, one should strive to continue using settling ponds until they are completely filled with solid clay sediment, and also to use as much as possible practically completely settled ponds filled with solid clay sediment that have become too small for efficient sedimentation. In other words, in this area there is an ever-increasing need for more efficient use of the areas occupied by already existing settling ponds.

The prior art is known the use of settling columns, for example cylindrical metal tanks, located above ground level. In principle, such a column with a sufficiently large height capable of ensuring the formation in it of a layer of supernatant liquid of the required thickness. However, in the process of extracting bitumen from tar sands, aqueous clay waste can be formed in such large volumes, at which the use of settling tanks, even of such a column type, becomes practically impractical.

It is also well known that the service life of the settling pond can be prolonged by scooping up solid clay sediment from it, but this method is laborious and does not directly solve the problem associated with the need to improve the efficiency of the bitumen extraction process from tar sands and to obtain a good quality supernatant.

The present invention was based on the task of developing such a method of extracting valuable components and, above all, of bitumen from tar sands, which would make it possible to obtain a higher quality supernatant sent for flotation or other separation stages, and would also allow more efficient use of settling ponds and allow would extract additional quantities of valuable hydrocarbons, usually lost during the process of sedimentation.

The method for extracting valuable components from tar sands proposed in the invention includes the main separation step, in which the tar sand is suspended in water and separated into an enriched fraction and clay waste diluted with water, and a waste sedimentation step, in which clay waste diluted with water is deposited in one or more sediment ponds with obtaining a practically solid clay sediment and supernatant liquid, which is returned to the main separation stage, at the same time at the stage of sedimentation from Odds of water-thinned clay waste are fed to a settler formed in the ground, water-rich clay waste is subjected to flocculation in a septic tank by mixing thereto a polymer flocculant and flocculated clay waste diluted with water is subjected to sedimentation in a septic tank to obtain a pumped thick, silky clay. return back to the main stage of separation, and thickened clay sediment from located in the sump below the supernatant zone liquids are pumped into one or several final settling ponds, in which further sedimentation of this thickened clay sediment takes place with the formation of a practically solid clay sediment.

The solution proposed in the invention as a whole can be used in any processes in which to separate valuable components contained in tar sands from mined raw material.

- 6 005875 or other material of its, respectively, it is suspended in water with the formation of large volumes of clay waste diluted with water, which is then subjected to settling (sedimentation) in settling ponds. In general, clay waste is similar in properties to extremely slow-hardening clay minerals, such as kaolinite, illite, chlorite, smectite, montmorillonite, attapulgite, or other typical clay minerals found in nature. Clay waste that is diluted with water may also contain fine particles of other minerals, such as sand, quartz, or other minerals, which are initially present in the tar sands deposits.

In a preferred embodiment, the method of extracting valuable components from tar sands of the invention is used to extract oil or bitumen from tar sands in a manner similar to, for example, the processes used to develop and process tar sands in Western Canada. At the same time, the solution proposed in the invention can also be used in the extraction and extraction of other minerals by any other methods, resulting in which the waste, due to the relatively low rate of natural sedimentation of the suspended particles, is advisable to be directed to settling in settling ponds, and The sedimentation process of such suspended particles can be accelerated by the addition of flocculant. As a particularly preferred example, bauxite development and purification systems can be cited.

If the method proposed in the invention is used in the process of extracting valuable components from tar sands, then at the main separation stage any separation methods traditionally used in such processes can be used. As an example, we can mention the separation of a suspension into separate phases in a cyclone separator, as well as by flotation. Often, the same material can be repeatedly or repeatedly returned to one or more stages of separation. The advantage of the method according to the invention is to obtain a recycle material stream with a reduced content of solid particles suspended therein. Recycling material flow with a relatively high degree of pollution can adversely affect the viscosity of the medium in the primary separation tank, and lead to excessive losses in the bottom discharge and excessive solids content in the extracted bitumen or extracted oil.

Clay waste that is diluted with water is a suspension, which mainly consists of clay particles suspended in water. However, a certain amount of useful coarse-grained mineral components or residual bitumen may also be present in such a suspension of clay particles or waste. The waste may be waste resulting from the initial separation of clay, and in this case usually contain from 6 to 20% solids and a certain amount of valuable mineral components or bitumen, or may be waste generated from secondary separation of clay, and In this case, a smaller amount of solid matter and a smaller amount of valuable coarse-grained mineral components or bitumen are usually contained. The suspension of clay particles or waste often represents or contains, in particular, the waste generated during the secondary separation of clay, i.e. waste generated by flotation or separation by another method. In some cases, wastes resulting from the primary and secondary separation of clay are processed separately, while in other cases they are processed in a mixed form.

In general, the total solid content of clayey matter in clayey waste diluted with water is no more than 20%, usually no more than 10% by weight, however, as a rule, the total solid content of clayey substance in such waste is at least 0.1% by weight, usually at least 0.5 wt.%. The solid is usually completely or predominantly composed of clay fine particles, but it may also contain some amount of waste or larger valuable mineral components that can be separated from clay by sedimentation, leaving the fine particles in suspension. The proportion of fine clay particles usually accounts for at least 20% by weight, usually at least 10% by weight, based on the dry weight of the waste. Fine clay particles, which can make up the bulk of the dry matter of the waste, have physical and chemical properties typical of clay waste, which, in particular, are such that, in practice, the only way to transfer fine particles to practically solid sediment is usually in the direction of such waste for settling in settling ponds and in their evaporation.

If the clay waste diluted with water contains coarse-grained valuable mineral components or other coarse-grained materials capable of natural sedimentation, such materials can be separated by sedimentation from the rest of the waste mass when they flow along the chute going to the settler (as described, for example, I85688404) or these valuable components can be separated by sedimentation in a settling pond prior to waste treatment in a settling tank in accordance with the method of the invention. So, in particular, waste containing valuable mineral components can be sent to the entrance zone of the settling pond, where the flow rate of waste at the entrance to the settling pond drops sharply, resulting in valuable mineral components settle down

- 7 005875 substantially in this entrance zone. After that, the deposited valuable mineral components can be removed from the bottom of the entrance zone or, if necessary, from the bottom of the whole settling pond by excavation.

Then, a stream of clayey waste diluted with water, optionally after preliminary separation from them by sedimentation of coarse-grained materials, enters a settler formed in the ground. Such a settling tank can be located in or near the primary settling pond, existing mines, canals, emergency spillway or in the zone of the secondary containment or in an empty (virgin) territory. In the preferred embodiment, the sump is proposed to be located in any convenient place, for example within the primary settling pond, more preferably at its bottom or at the entrance of waste. The sump can be created by excavation, digging a sufficiently deep hole in the ground, for example, a square, rectangular, round or oval shape around the perimeter. If necessary, the walls of the sump can be strengthened to avoid their erosion and shedding (erosion), however, there is usually no need for this.

The use of such a settling tank instead of a settling column allows, at extremely low costs, to obtain a settling zone of a sufficiently large volume and a sufficiently large depth. The clay waste diluted with water entering such a sedimentation tank is separated in it as a result of settling the supernatant liquid and the thickened sediment layer on the layer. The supernatant can be drained, pumped out or in any other way removed from the upper part of the settler, provided that its removal does not disrupt the integrity of the layer of thickened sediment formed at the bottom of the settler. Typically, the supernatant automatically overflows over the edge of the sump due to its overflow with almost continuous admission to it, waste. It is possible to divert the supernatant overflowing the sump basin in any appropriate way, for example, withdrawing it through the channel and feeding it through the pipeline back to the separation stage, in which case the sump can be excavated at any convenient place.

As indicated above, it is preferable to dig up the settling tank in the place where it has easy access, simplifying the delivery of clay waste into it and the selection of purified water returned to the process cycle, and it can be placed at the bottom of the primary settling pond so that the settling tank overflows the supernatant could spread over the open bottom of the primary settling pond. Typically, a primary sedimentation pond is already used to collect solid clay sediment during the extraction of minerals, and therefore the supernatant in this case will spread along practically solid clay sediment in the primary sedimentation pond.

The flow of the supernatant liquid pouring out of the settling tank over the surface of the sludge formed in the settling pond prior to its return to the main separation stage creates the effect of its purification and as a result allows increasing its transparency and also reducing the solid particles suspended in it and only after that return it to flotation or other major separation stage.

Typically, it is preferable to create a settling tank in a settling pond, which is already essentially completely filled with practically solid clay sludge. Thus, when implementing the present invention, it becomes possible to use a settling pond, which is already essentially completely filled with sediment, for a new and extremely important purpose, consisting in digging a settling tank in it for waste treatment and in subsequent use of the sediment contained in it for the purification of the supernatant flowing from the clarifier. fluid. The rate of increase in sediment volume in the settling pond as a result of such additional purification of the supernatant is extremely small, which allows extending the life of the settling pond for almost an unlimited time.

The expression essentially filled means that the settling pond is too shallow to be effectively used to separate the clean supernatant from the sediment when, for example, the horizontal component of the flow rate of the supernatant significantly exceeds the vertical component of the sedimentation rate of solids.

In the method according to the invention, it is advisable to use a sump with a depth of from about 6 to about 60 feet or more, preferably from about 25 to about 60 feet, and with such an upper surface area (approximately square or circular shape) at which the flow through the sump is from 0.01 to 1, preferably from 0.1 to 0.5 US gallons per minute per square foot. The required area of the upper surface of the sump depends on the flow of clay waste entering it.

The area of the traditional primary settling pond is from about 50 to about 2000 acres, usually from 250 to 1000 acres. The distance traveled by the supernatant when it flows over the surface of the practically solid clay sediment in the primary sedimentation pond is generally at least 300 feet, usually at least 700 feet, for example, from 1000 to 5000 feet. The flow parameters of the supernatant all the way from the moment of overflow over the edge of the settler to the exit from the primary sedimentation pond are preferably set in such a way as to have a minimal disturbing effect on the clay deposited in the supernatant on the almost hard clay sediment located at the bottom of the settling pond . Preferably, the flow of the supernatant moved over the settled clay and over the solid clay sediment.

- 8 005875 in a layer whose thickness is at least about 6 inches, more preferably at least about 1 foot, most preferably at least about 3 feet, and which, with such a thickness, is perceived by the naked eye as transparent. The supernatant flow should move at such a rate that favorable conditions for sedimentation are created, and the risk of disturbing the settled clay is reduced to a minimum and which, accordingly, should be approximately 0.000001 to 0.1 gallons per minute per square foot.

In the sump, the clay waste diluted with water is subjected to flocculation by mixing thereto a polymer flocculant in an amount that should ensure an optimal flow of the flocculation process with a minimum consumption of this polymer flocculant. Polymer flocculant can be added in solid form, but more often it is added in the form of a solution previously prepared using conventional technology, the concentration of polymer in which is usually from about 0.1 to 2 wt.%. Polymer flocculant can be added to the waste either after or before it enters the septic tank, or it can be added to the recycled supernatant before it is mixed with the contents of the septic tank. The point of addition of the polymer flocculant can be located directly in front of the entrance to the settling tank or much further from the entrance to the settling basin, as described, for example, in patent I8 5688404.

Typically, a polymer flocculant is added to the waste as it flows through a mixing device, from which the waste is discharged into a sump. Such a mixing device can be a pipeline or other device suitable for this purpose, for example a tank, or a small well dug in the ground, when flowing through which in the waste stream creates enough turbulence to mix them thoroughly with the flocculant. Turbulence in the waste stream can also be created solely by passing the stream through the pipeline at a sufficiently high speed or by using turbulizers or other devices that give the flow a turbulent flow of devices or by injecting water into the pipeline. For effective mixing of waste with polymer flocculant, which is necessary for almost uniform flocculation, if necessary, mechanical rotors or other mixing devices with a mechanical stirrer can be used.

As a polymer flocculant, you can use any water-soluble polymer flocculant, which is able to activate flocculation and thereby the separation of water-diluted waste into a supernatant and thickened clay sediment. Usually, a water-soluble polymer formed from one or more ethylenically unsaturated monomers is used as a polymer flocculant. Such monomers may be non-ionic, anionic or cationic. Similarly, the polymer may be non-ionic, anionic or cationic, or amphoteric.

Acceptable anionic monomers include ethylenically unsaturated carboxyl or sulfone-containing monomers, such as acrylic acid, methacrylic acid, or 2-acrylamido-2-methyl propane sulfonic acid (AMPS) (a US registered trademark owned by Euipho1 Mortar! Ο η) An example of an acceptable non-ionic monomer is acrylamide. Cationic monomers suitable for use in the purposes of the invention are dialkylaminoalkyl (meth) acrylates and -acrylamides, usually in the form of their quaternary ammonium salts or acid addition salts, or diallyldimethylammonium chloride.

Preferred anionic polymers are copolymers of 5-70% by weight, usually 10-50% by weight, of anionic monomers, for example acrylic acid (usually in the form of sodium acrylate) and / or AMPS, with other monomers, usually acrylamide. Particularly preferred anionic copolymers are Regso1 336, Regso1 727 and Regso1 358, manufactured by C1A 8ress1 Syyetuac, Aalcc TegaEnieE 1ps. Acceptable cationic polymers are copolymers of 1-50 wt.%, Usually 2-15 wt.%, Of a cationic monomer, for example dimethylaminoethyl acrylate or methacrylate in the form of its acid-addition or quaternary ammonium salts, with other monomers, usually acrylamide. Particularly preferred cationic polymers are the products of Regso1 455 and Regso1 352, also produced by C1Ba 8restil Syytuyak, Alater TregaPeE 1ps.

Typically, the polymer has a molecular weight at which its characteristic viscosity (VI) (measured using a viscometer with a suspended level using 1N sodium chloride, buffered to pH 7 at 20 ° C) is at least 4 dl / g, usually at least 8 dl / g. In the case of an anionic polymer, its IV is usually from 10 to 30 dL / g, and in the case of a cationic polymer, its IV is usually from 8 to 15 dL / g.

Polymer flocculant can be obtained by known technology, gel polymerization, suspension polymerization with reversed phase or reversed phase emulsion polymerization or any other acceptable method.

The optimum dosage of the polymer flocculant is selected by the traditional method of sedimentation, and is usually from 0.01 to 1, preferably from about 0.0255 to about 0.75 pounds of polymer per ton of solids contained in the flocculated waste.

- 9 005875

The specific polymer flocculant and its amount can be selected by known methods in such a way as to achieve the optimum ratio between the purity of the supernatant and its layer thickness and the optimal sedimentation rate, on the one hand, and to ensure the formation of pumpable thickened clay sediment, on the other hand .

The theoretical residence time of the clay waste diluted with water in the settling tank is usually from 5 minutes to 5 hours, preferably from 10 minutes to 3 hours, for example from 45 to 120 minutes.

To accelerate the process of flocculation to the clay waste diluted with water, diluting water can also be mixed with the flocculant solution, since the solids content of the waste entering the septic tank often exceeds the value at which the settling process proceeds at the optimum rate. The optimal amount of dilution water can be determined experimentally. An additional advantage of this option, which implies the treatment of wastes at the optimum degree of their dilution, is the ability to optimize the use of polymer flocculant, which is manifested in the formation of a visible oil film floating on the surface of the supernatant. Over time, a significant amount of bitumen gradually accumulates in such an oil film, which can ultimately be removed from the surface of the supernatant by any acceptable method, thereby increasing the total yield of bitumen extracted during the implementation of the method proposed in the invention.

The thickened clay sediment is removed from the settling tank at a point located well below the supernatant liquid layer and / or at a time at which such removal of sediment from the settling tank does not adversely affect the quality of the supernatant. It is possible to select thickened clay sediment from the settling tank in continuous or batch mode. Typically, the solids content in the sediment increases towards the bottom of the sedimentation tank, and therefore, in order to minimize the risk of gradually filling the settling tank with thickened clay sediment, it is advisable to select it from the clarifier at a point that should be located as close as possible to the bottom of the settling basin.

The solids content in the sludge removed from the settling tank is usually at least 2 or 3 times, and often even up to 10 times the solids content in the initial stream of clay waste diluted with water, subjected to flocculation. Typically, the solids content in the thickened sediment is from about 10 to about 30 wt.% In terms of the weight of dry solids. To measure these parameters, a sample of a thickened precipitate of a known mass is taken and the liquid component or moisture is evaporated from it at a known temperature (usually 105 ° C) from it under standard laboratory conditions. The solids content in the sludge should preferably be as high as practical from a practical point of view, but at the same time it should not be too high at which the sediment becomes unsuitable for pumping.

Thickened clay sediment is preferably removed from the sump by pumping out, for example, using a stationary pump that is installed on the ground near the sump wall and from which ends a pipe that ends at the sump bottom, through which thickened clay sediment is sucked out or by means of a floating pump that floats the surface of the supernatant and from which the pipe extends downward, ending at the bottom of the sump.

The thickened sediment taken from the sedimentation tank is sent to one or several final settling ponds, where it is distributed over the area of the settling pond and left to sediment and evaporate volatile components from it with the formation of a finally formed practically solid clay sediment. Since the solids content in the thickened sediment taken from the settling tank is much higher than in conventional clay waste, its settling and evaporation of volatile components from it, which is necessary for the formation of a finally formed solid sediment, occurs much slower compared to traditional methods and is accompanied by the formation of such a small amount of supernatant that it is simply not economically feasible to return it back to the technological cycle (given that significant time s returned back to the work cycle of the supernatant was taken from settler). In line with this, one or more of the final settling ponds should not have an equally great depth, which is usually considered necessary for upholding large volumes of waste. As a result, it becomes possible to pump thickened sediment into settling ponds, which are already partially or almost completely filled with sediment.

One of the main advantages of the solution proposed in the invention is, therefore, the ability to achieve a high yield of supernatant (often of very high purity) and at the same time the possibility to continue the operation of settling ponds, which would previously be considered unsuitable for their further multipurpose use - due to too high degree of their filling with sediment and too shallow depth.

Below the invention is illustrated by example.

Example. In order to extract valuable components from tar sands in accordance with the method proposed in the invention, tar sand was suspended in water and bitumen was separated from the resulting suspension in a primary separation tank, from the output of which mainly bitumen was collected,

- 10 005875 coarse sand tails and fine clay tails. These fractions were subjected to additional separation at subsequent stages (including flotation) to obtain fractions containing bitumen and clayey waste diluted with water, the solids content of which varied from 0.2 to 20% and which contained the residual amount of valuable bitumen.

Claims (13)

CLAIM 1. The method of extracting valuable components from tar sand, including the main separation stage, in which tar sand is suspended in water and separated into an enriched fraction and clay waste diluted with water, and a waste sedimentation step, in which clay waste diluted with water is precipitated in one or more sediment ponds to obtain a practically solid clay sediment and supernatant, while at the stage of sedimentation of waste, clay diluted with water is fed into a sump, diluted With water, clay waste is subjected to flocculation by mixing polymer flocculant thereto and flocculated water-diluted clay waste is subjected to sedimentation to obtain a pumpable thickened clay sediment in the sump. 2. The method according to claim 1, in which also at least part of the thickened clay sediment is removed from the settling tank and the thickened clay sediment removed from the settling basin is sent to one or more final settling ponds, where as a result of its further sedimentation and evaporation of volatile components from it almost solid clay sediment. 3. The method according to claim 1, in which use the sump dug in the primary sedimentation pond, which is almost solid clay sediment formed during the development and extraction of minerals. 4. The method according to claim 3, in which the flow of the supernatant before passing to the main stage of separation passes on the surface of a practically solid clay sludge located in the primary sedimentation pond. 5. The method according to claim 1, in which at the main stage of separation is carried out at least one-stage flotation process, in which the supernatant is returned. 6. The method according to claim 1, in which the solids content in the thickened clay sediment is 5-100 times higher than the solids content of the clay waste diluted with water. 7. The method according to claim 1, in which the content of solid clay particles in clay-diluted waste water is from 0.1 to 15%, and the solids content in the thickened clay sediment is from 10 to 60%. 8. The method according to claim 4, in which as the primary use a settling pond, which is essentially completely filled with almost solid clay sludge formed during the development and extraction of minerals. 9. The method according to claim 2, wherein one or more primary settling ponds and one or more final settling ponds are used, which are substantially completely filled with practically solid clay sediment formed during the development and extraction of minerals. 10. The method according to claim 1, in which the clay waste diluted with water contains particles of valuable mineral components, which are separated by sedimentation from the rest of the clay waste diluted with water before they enter the sump. 11. The method according to claim 1, in which bitumen is extracted from tar sands. 12. The method according to claim 11, wherein a water-soluble cationic polymer with a characteristic viscosity of at least 4 dl / g is used as a flocculant. 13. The method according to claim 11, in which flotation is carried out at the main separation stage using an amine flotation agent, clayey waste diluted with water is treated with mineral acid, and a water-soluble anionic polymer is used as a flocculant.