RU2275338C2 - Treatment of mineral material - Google Patents

Abstract

FIELD: polymers, chemical technology.

SUBSTANCE: invention relates to treatment of mineral material, in particular, waste in processes of aluminum oxide extraction by a method of Bayer firm involving treatment of red oxide of iron slime waste in order to improve their easy transporting. Material involving an aqueous liquid with dispersed solid particles is pumped as fluid medium followed by standing and hardening. Hardening is improved in simultaneous retention of material to pumping by combination of this material with polymeric particles in the process or before pumping the material. Polymeric particles involve water-soluble polymer with intrinsic viscosity value at least 3 dl/g wherein polymers particles are in form of an aqueous dispersion including: (a) liquid dispersion medium consisting of mainly saline solution that comprises at least 25 wt.-% of inorganic salt as measure for the total mass of dispersion medium, and (b) water-soluble non-ionogenic or anion-active polymer of vinyl poly-addition that is insoluble in saline solution wherein this polymer is prepared from ethylene-unsaturated monomers comprising acrylic acid or salts, optionally (meth)acrylamide and optionally at least one cross-linking monomer comprising at least two polymerizing ethylene-unsaturated groups and wherein inorganic salt represents metal of group II halide, or wherein particles of polymer are in form of solid powder that is added to the material directly. Treatment method provides effective pumping the material and its hardening as waste useful for stacking, essential decrease of liquid in the material.

EFFECT: improved method for treatment of materials.

11 cl, 3 tbl, 2 dwg, 4 ex

Description

The present invention relates to the processing of mineral material, in particular waste from the Bayer alumina recovery process, including the treatment of red mud, to make it more easily disposed of.

Ores processing processes to extract valuable minerals from them usually result in waste. Often the waste is a thick aqueous suspension or slurry, including particles of mineral material, such as clay, sand, fine solid particles, metal oxides, etc. Before placing in a suitable area from the slurry or slurry discharged into the waste, water must be removed.

In some cases, waste material, such as mineral enrichment waste, can be successfully placed in the mine as backfill. Typically, backfill waste as a significant proportion includes coarse particles, large particles, together with other smaller particles; a thick suspension is pumped into the mine, where they provide it with the opportunity for dehydration, leaving the solid particles of sludge in place. To facilitate this process, in normal practice, resort to the use of flocculants.

In other cases, waste disposal in the shaft or shaft is not possible. In these cases, the waste material can be transported to slurry basins, dumps or piles. There is serious concern about the pressure on the environment, the need to minimize the need for new parcels of land for waste disposal, and to use existing waste disposal zones more efficiently. One way is to place the waste in a plurality of layers, thereby forming higher stacks of waste. However, this makes it difficult to ensure that waste material that is able to spread over the surface of previously hardened waste remains within acceptable boundaries and hardens to form a stack, and the waste becomes dense enough to support multiple layers of hardened material without the risk of destruction or collapse. Thus, the requirements for the disposal of waste material having the characteristics of the desired type for stacking are generally different from the requirements for materials for other disposal options, such as backfill.

In the process of extracting alumina from bauxite according to the Bayer method, bauxite is treated in an aqueous alkaline solution to obtain sodium aluminate, which is separated from the insoluble residue. This residue consists mainly of ferric oxide particles and is known as red mud.

The red mud is washed in several successive washing steps, in which this red mud is contacted with the wash liquid, and then flocculated by the addition of a flocculant. Next, the settled liquid is treated to isolate the aluminate. After the final washing step, the slurry suspension is thickened as much as possible, and then placed as waste. Thickening in the context of the present description means that the solids content in the red mud is increased. The final treatment of the thickened material may include only settling the flocculated thick suspension or sometimes includes a filtration step. Alternatively, or additionally, sludge waste can be subjected to prolonged sedimentation in a sludge basin.

Sludge waste can be placed and / or further dried for subsequent placement in the stacking zone of sludge waste. In order for the slurry waste to be stackable, it must have a high solids content and, when stacked, should not spread, but should be relatively solid to such an extent that the angle of inclination of the stacked layer is as large as possible, thanks to why the stack at a given volume occupied the smallest possible area. The requirement for a high solids content contradicts the need for the material to remain pumpable as a fluid, so that even though it is possible to prepare slurry waste having a high solids content necessary for stacking, the slurry waste may become unsuitable for pumping.

EP-A 388108 describes the addition of a water-absorbing water-insoluble polymer to a material including an aqueous liquid with dispersed solid particles, such as red mud, before pumping and then pumping this material, after which the material is left to stand and then allowed to harden and become stackable solid material. The polymer absorbs the aqueous liquid of the sludge, which contributes to the binding of solid particles and, therefore, the solidification of the material. However, this method has a disadvantage in that a high consumption of an absorbent polymer is required to achieve appropriate solidification. To obtain sufficiently hardened material, it is often necessary to use a polymer with a high flow rate of 10 to 20 kg / t of sludge waste. Although the use of a water-swellable absorbent polymer to solidify a material can apparently result in an apparent increase in solids, the aqueous liquid is actually retained in this absorbent polymer. This is a disadvantage in that since the aqueous liquid from the hardened material is not actually removed, subsequently, under certain conditions, the aqueous liquid could be desorbed, which could create a risk of re-fluidization of the waste material with the inevitable risk of destabilization of the stack.

Thus, there is a need to develop a method, the implementation of which would allow with great efficiency and convenience as easy as a fluid to pump material, which, when standing, hardens in the form of solid waste suitable for stacking. There is also a need to achieve this effect by substantially reducing the amount of aqueous liquid contained in the material.

The present invention provides a method in which a material comprising an aqueous liquid with dispersed solid particles is pumped as a fluid, and then left to stand and solidify, wherein the solidification is improved while maintaining the pumping ability of the material by combining the polymer particles with the material during or before pumping this material, where the polymer particles include a water-soluble polymer that has an intrinsic viscosity of at least 3 dl / g.

Adding polymer particles, which are a water-soluble polymer, to the material allows the material to maintain its fluidity and ability to easily be pumped, but to form a solid mass when standing, which has sufficient strength to support subsequent layers of hardened material. It was found that the presence of water-soluble polymers used in the form of particles does allow the material to remain fluid and able to be pumped during the pumping stage, but when standing it leads to a rapid loss of fluidity and hardening. Moreover, the target result of this treatment is the allocation of the material when standing aqueous liquid. Obviously, the consequence of treating the material with such a powdery water-soluble polymer is a gradual increase in viscosity, but not so significant as to prevent the possibility of pumping the material. It has also been established that the addition of a water-soluble polymer does not immediately dehydrate the material before it is delivered to the location, which could cause blockage in the pipeline.

Acceptable polymer flow rates are in the range of 10 to 10,000 g / t solid material particles. In general, the corresponding flow rate can vary depending on the specific material and the solids content therein. The preferred flow rate is in the range from 100 to 3000 g / t.

The method according to the invention is suitable for processing a material in which the dispersed solid particles are very small in size, in particular when the size of almost all particles is less than 100 microns, and even materials whose size of almost all particles is less than 50 microns. It is especially important when the size of at least 90% of the particles is less than 20 microns, mainly when it is impossible to easily or economically reduce the proportion of liquid in the waste stream.

Typically, the particles of the material are inorganic and / or, as a rule, mineral. Although the proposed method may be effective in relation to other materials that need to be pumped and then stacked, mainly the materials that make up filter cake, concentrate waste, condensed concentrate products or non-condensed factory waste streams, for example other mineral beneficiation waste or flotation tailings, including flotation tailings of phosphate, diamond, gold ores, flotation tailings in the processing of copper, silver, uranium ores, in the enrichment of coal or iron ore, main vnoe it finds application with final processing hub material or with washing steps in the process by the method of the company Bayer. Thus, the red mud can be solid particles deposited in the final concentrator or at the washing stage by adding only a flocculant, or, optionally, the filter cake from the filtration stage can be used as a material (for example, pressure filtration, vacuum filtration, etc. .) a thick suspension obtained at the final stage of washing.

The solids content of the red mud or other material that is pumped may be in the range of 15 to 80% by weight. Often their content in red mud is in the range from 20 or 30 to 70 wt.%, For example from 45 to 65 wt.%. The sizes of almost all particles in a typical sample of red mud are less than 25 microns. So, for example, the size of about 95 wt.% Particles of sludge waste is less than 20 microns and about 75% are less than 10 microns and at the same time, the size of about 95 wt.% Particles exceeds 3 microns.

When creating the present invention, it was found that even better results are achieved when the material is relatively concentrated and homogeneous. It may also be necessary to introduce polymer particles in combination with other additives. So, for example, the properties of the outflow of material through the pipeline can be improved by the inclusion of a dispersant. In cases where the inclusion of a dispersant is provided, it is usually administered in conventional amounts. However, when creating the present invention, it was found that the presence of dispersants or other additives does not impair the solidification of the material when standing.

Thus, in the present invention, polymer particles are added directly to the aforementioned material. The polymer particles may be wholly or partially composed of a water-soluble polymer. Therefore, the powder polymer may be a mixture of a crosslinked, water-insoluble, water-insoluble polymer swellable with a water-soluble polymer. They can be a physical mixture of a water-swellable polymer with a water-soluble polymer or, alternatively, a slightly crosslinked polymer, in particular such as described in EP 202780. Although the polymer particles may include some amount of a crosslinked polymer, it is essential to carry out the present invention. the amount of water soluble polymer. When the polymer particles comprise some swellable polymer, it is necessary that at least 80% of the polymer is in a water-soluble polymer. Preferred polymer particles are completely or at least substantially water soluble. The water-soluble polymer can be branched in the presence of a side-chaining agent, for example as described in WO-A 9829604, in particular in claim 12, or in another embodiment, the water-soluble polymer is substantially linear.

The preferred molecular weight of the water-soluble polymer is in the range from moderate to high. Its intrinsic viscosity should be at least 3 dl / g, and usually at least 5 or 6 dl / g, although the polymer can be substantially high molecular weight and exhibit an intrinsic viscosity of 25 or 30 dl / g or even higher. The preferred intrinsic viscosity of this polymer is in the range of 8 to 20 dl / g, more preferably 11 or 12 to 16 or 17 dl / g.

The water-soluble polymer may be a natural polymer, for example polysaccharides, such as starch and dextran, or a semi-natural polymer, such as carboxymethyl cellulose and hydroxyethyl cellulose. A synthetic polymer is preferred, and a polymer derived from an ethylenically unsaturated water-soluble monomer or a mixture of monomers is more preferred.

The water-soluble polymer may be cationic, nonionic, amphoteric, but preferably anionic. Particularly preferred anionic polymers are derived from monomers selected from ethylenically unsaturated carboxylic acid and sulfonic acid monomers, preferably selected from (meth) acrylic acid, allyl sulfonic acids and 2-acrylamido-2-methylpropanesulfonic acid, optionally in combination with nonionic comonomers, preferably selected from ( meth) acrylamide, hydroxyalkyl esters of (meth) acrylic acid and N-vinylpyrrolidone.

According to the invention, a water-soluble polymer can be obtained by any suitable polymerization method. The polymers can be obtained, for example, in the form of gel polymers by solution polymerization, a suspension in water in oil, or in an emulsion of water in oil. When gel polymers are prepared by solution polymerization, initiators are usually introduced into the monomer solution. It is possible, but not necessary, to use a thermal initiator system. A thermal initiator typically includes any suitable initiator compound that liberates radicals, such as azo compounds, such as azobisisobutyronitrile, at elevated temperatures. During polymerization, the temperature must be raised to at least 70 ° C, but preferably to a level below 95 ° C. In another embodiment, the polymerization can be carried out with irradiation (ultraviolet rays), exposure to microwave energy, heat, etc., with the optional use of also suitable initiating radiation sources. After completion of the polymerization and sufficient cooling of the polymer gel, this gel can be processed in the usual way, first by grinding the gel into smaller pieces and drying until the polymer is practically dehydrated, followed by grinding into a powder. Alternatively, polymer gels can be used in the form of polymer gels themselves, for example, in the form of gel polymer rods for neutron scattering. Such polymer gels can be prepared using an acceptable polymerization technology, as described above, for example with irradiation. The gels can be cut into pieces of the appropriate size, which are necessary, and then, when used, mixed with the material in the form of particles of a partially hydrated water-soluble polymer.

The polymers can be obtained in the form of beads by suspension polymerization or in the form of an emulsion or dispersion of water in oil by polymerization in an emulsion of water in oil, for example, in accordance with the method described in EP-A 150933, EP-A 102760 or EP-A 126528.

In another embodiment, particles of a water-soluble polymer may be prepared as a dispersion in an aqueous medium. It can be, for example, a dispersion of polymer particles of at least 20 microns in an aqueous medium containing a balancing agent, as described in EP-A 170394. It can also include, for example, an aqueous dispersion of polymer particles prepared by polymerization of aqueous monomers in the presence of an aqueous medium containing dissolved polymers with low IV (intrinsic viscosity), such as polydiallyldimethylammonium chloride and optionally other dissolved materials, for example, an electrolyte and / or polyhydroxy compounds, including polyalkylene glycols as described in WO-A 9831749 or WO-A 9831748.

In one embodiment of the invention, the polymer particles can be added to the material (for example, red mud) in the form of particles of a water-soluble polymer in an aqueous dispersion.

In a particularly preferred embodiment, the polymer particles are in the form of an aqueous dispersion, for example as set forth in the patent application of the authors of the present invention (case number MP / W-22308 / P1 / AC 557). In this embodiment, the aqueous dispersion includes (a) a liquid dispersion medium consisting essentially of a saline solution that contains at least 25 wt.% Inorganic salt, calculated on the total weight of the dispersion medium; and (b) a water-soluble non-ionic or anionic vinyl polyaddition polymer that is practically insoluble in saline, where the polymer is derived from ethylenically unsaturated monomers including acrylic acid (or salts), optionally (meth) acrylamide and optionally at least one crosslinking monomer containing at least two polymerizable ethylenically unsaturated groups, and wherein the inorganic salt is a Group II metal halide.

In this embodiment, the liquid dispersion medium should consist primarily of dissolved inorganic salt, and although small amounts of other materials may be acceptable, they are not necessary to carry out the invention. Moreover, materials that serve to increase the viscosity of the dispersion medium may be undesirable if the viscosity increases to such an extent that it prevents the flow or the possibility of pumping the dispersion.

The salt solution may include other dissolved salts, but must contain a group II metal halide in an amount that is sufficient to prevent polymer dissolution. Saline solutions prepared entirely using group I metal salts, for example sodium chloride or potassium iodide, do not interfere with polymer hydration. Even saturated solutions of such salts do not provide an acceptable polymer dispersion. Thus, in the presence of other inorganic metal salts in the salt solution, it is essential that the group II metal halide be the main salt component. A preferred dispersion medium includes only an inorganic salt, which consists entirely of a group II metal halide, since this results in the formation of an acceptable dispersion in which the polymer remains practically unhydrated for an unlimited time or at least for long periods of time during which storage is possible. The polymer can become partially hydrated and partially swell, as long as the polymer particles remain discrete and dispersible.

Preferred polymer particles remain unhydrated and not swollen to any noticeable degree. When the dispersion is not stirred or not stirred, the polymer particles tend to settle. However, unexpectedly, these particles practically do not hydrate and do not form agglomerates, so that they can be easily redispersed to obtain a dispersion.

The preferred halide salt of a Group II metal is beryllium, magnesium, calcium, and strontium halide, since they appear to provide the best results in reducing or preventing the hydration of the polymers in the dispersion.

Acceptable results are obtained when the halide of the Group II metal halide is fluoride, chloride or bromide.

It is possible to use a mixture of different Group II metal halides, although usually one of these salts is sufficient.

When the aqueous dispersion comprises a dispersion medium, which is an aqueous saline solution of at least one of the following Group II metal halides: magnesium chloride, magnesium bromide, calcium chloride and calcium bromide, improved results are obtained. Best results are achieved when the inorganic salt is calcium chloride.

Typically, a dispersion medium of an aqueous dispersion includes a group II metal halide in high concentrations. The salt concentration in the dispersion medium should be at least 25% by weight, whereby the choice of salt usually depends on the solubility of the salt. Preferred results are obtained when the salt concentration is at least 30 wt.%, And usually at least 35%. Improved results are noted when the salt concentration is not less than 36 wt.%. However, in a more preferred embodiment, much improved results are achieved, as was found when the inorganic salt is contained in an amount of from 39 to 45 wt.%.

When creating the present invention, it was found that the dispersion may include relatively large amounts of polymer, for example at least 30 wt.% Such a polymer per unit volume of the dispersion medium. However, usually the amounts of polymer contained in the dispersions are much larger. So, for example, an aqueous dispersion may include a polymer in the range from 40 to 60 wt.% Per unit volume of the dispersion medium.

In one preferred embodiment, an aqueous dispersion is provided, the bulk viscosity of which, when determined at pH 7.0 and 25 ° C., is less than about 10 cP, comprising (a) a dispersion medium, which consists of a saline solution, calculated with respect to a total weight of the dispersion medium of from about 35 to about 45% by weight of an inorganic salt selected from the group consisting of calcium chloride, calcium bromide, magnesium chloride and magnesium bromide; and (b) at least 30 wt.% non-ionic or anionic water-soluble or water-swellable vinyl polyaddition polymer per unit volume of dispersion medium, where this polymer is obtained from ethylenically unsaturated monomers, including acrylic acid (or salts) and / or (meth ) acrylamide and optionally at least one crosslinking monomer containing at least two polymerizable ethylenically unsaturated groups.

The polymer particles used in this embodiment of the invention can be obtained in any conventional manner. The polymer particles can be prepared in the form of dry free-flowing particles. So, for example, they can be prepared in the form of an aqueous gel, which is dried and crushed to particles of a suitable size, or in the form of beads using the method of suspension polymerization with a reversible phase. Alternatively, the polymer particles can be prepared by reversible-phase emulsion polymerization and optional subsequent vacuum distillation to partially dehydrate the dispersed phase of the polymer particles. Further, these particles can be separated from the continuous oil phase by conventional technology, and then re-dispersed in an aqueous dispersion medium.

Typically, the viscosity of the dispersion is less than 10 cP, for example only 5 cP or less. In some cases, the viscosity may be as little as 1 or 2 cP or less.

Thus, an aqueous polymer dispersion can be prepared by performing the steps

(a) preparing a liquid dispersion of a material that includes an aqueous saline solution containing at least 25 wt.% inorganic salt, which is a group II metal halide;

(b) combining this dispersion medium with a water-soluble non-ionic or water-swellable non-ionic or anionic vinyl polyaddition polymer which is insoluble,

where this polymer is obtained from ethylenically unsaturated monomers, including acrylic acid (or salts), optionally (meth) acrylamide and optionally at least one crosslinking monomer containing at least two polymerizable groups, to obtain a mixture of polymer and dispersion medium,

where this dispersion medium is mixed during and / or after the formation of the mixture in order to prepare the dispersion.

Typically, the dispersion medium is mixed and polymer particles are sent to this medium using, for example, a screw feeder. Particles can also be filled or blown into the medium. Often the medium is contained in a tank with a stirrer and the polymer is directed into this mixed medium. The mixed medium may also be a liquid flowing down the pipe into which the polymer is fed.

In another embodiment, the polymer can be sent to a dispersion medium, which is practically not mixed. For example, the polymer can be allowed to precipitate in a dispersion medium, and then the dispersion can be prepared by subsequent stirring, for example, stirring with a stirrer or passing through a pipe.

An aqueous dispersion of polymer particles in saline as a dispersion medium comprising a Group II metal halide can be introduced into the material by any conventional route. So, for example, this dispersion can be pumped directly into the pipeline through which the material flows. Alternatively, the aqueous dispersion can be introduced in a state of final sedimentation before transporting the condensed material through the pipeline. When the material is red mud from a Bayer process, for example, any of these technologies is acceptable.

In another embodiment, the average size of the polymer particles added to the material is less than 10 microns. These polymer particles can be added in the form of a reverse phase emulsion comprising the dispersed phase of a water-soluble polymer dispersed in a water-immiscible liquid. Alternatively, the particles can be added in the form of a reversed phase dispersion, which is preliminarily prepared by dewatering the reverse phase emulsion under reduced pressure to remove most of the water from the dispersed phase. Dispersions or emulsions with a reversed phase often contain polymer particles, the sizes of at least 90% of which are less than 2 microns, usually less than 1 micron, and the average particle size can be, for example, in the range from 500 to 750 nm. The polymer particles can also be added in the form of a microemulsion in which the average particle size is less than 200 nm, for example from 50 to 100 nm.

Thus, in this embodiment, the reverse phase emulsion or dispersion can be pumped directly into the pressure pipe through which the material is transported, for example, in the same manner as in the first embodiment. Simultaneously with the introduction of the emulsion or dispersion with a reversed phase, it may be necessary to add an activator. The activator can be any ordinary activator, which is usually used to activate emulsions or dispersions with reversed phase. The activator can be added in any acceptable amount, usually in the range from 1 to 5 wt.% In terms of the emulsion, for example in the range from 2 to 4%.

In another embodiment, such polymer particles may be agglomerates or aggregates of primary particles, the average size of which is less than 10 microns, while the size of the aggregated particles exceeds 20 microns. Thus, the particles can exist in the form of bonded brittle aggregates, the sizes of at least 90 wt.% Of which exceed 50 microns. When added to aqueous material, aggregates are destroyed to primary particles.

In a preferred embodiment of the method of the invention, the polymer particles are added to the material in the form of substantially individual particles, the size of which exceeds 20 μm, preferably exceeds 50 μm. The best results are obtained when the polymer particles are much larger than, for example, at least 100 microns, in particular when the sizes of at least 90% of the particles exceed 200 microns. The size of the preferred polymer particles can be up to 2.5 mm, for example up to 2 mm. In general, the sizes of the polymer particles are in the range from 500 μm to 1 or 1.5 mm. In this preferred embodiment, the polymer particles can be added in the form of a powder, which is formed during polymerisation in solution, or a bead, which is formed during suspension polymerisation.

The polymer particles are combined directly with the material by any suitable method using conventional metering equipment. So, for example, when the particles exist as a dispersion in an acceptable liquid (aqueous or reverse phase), this dispersion can be metered directly into the material that is pumped through the pipeline. When the polymer particles are in the form of free-flowing particles, they can be fed from the hopper using a screw feeder and directly mixed with material moving through the pipeline. The polymer particles can also be directed into the material by air flow. In some situations where the material is transported through a pipeline under high pressure, it may be necessary to force the direct introduction of dry polymer particles into the material using any suitable means. They can be, for example, a high pressure pump, in particular a screw feeder or a pump with increasing cavitation (progressive cavity pump). In some cases, the polymer particles are fed into the material using a high pressure pump in combination with air purging.

When creating the present invention, it was found that particularly good results are achieved when particles of a water-soluble polymer are rapidly distributed in the mass of material. This can be achieved by combining the polymer particles with a powder diluent. Typically, the polymer particles are apparently mixed with a diluent so that these polymer particles are distributed in the mass of the diluent. The desired diluent may be sodium chloride or, alternatively, sucrose. An acceptable ratio between polymer and diluent may range from 10:90 to 90:10.

In a preferred embodiment of the invention, in order to reduce the likelihood of an uneven distribution of polymer particles in the entire mass of material, for example, delamination with a release of a layer of polymer particles, these particles are quickly mixed with the material. The mixing of polymer particles can be achieved using an in-line mixer or, preferably, by draining a portion of the material into a mixing device in which polymer particles (for example, in the form of a powder, emulsion or dispersion) are thoroughly mixed with the material, after which the processed material is returned into the main pressure pipe.

In one preferred embodiment, the polymer particles in the form of a solid are combined with the material using new polymer injection equipment. In this embodiment, the material (which is processed) moving through the pipeline, is sent to the mixing chamber. Polymer particles are also fed into this mixing chamber and mixed with the material. It is advisable to feed the polymer particles from a suitable storage container, such as a hopper, using a screw feeder. A preferred mixing chamber is provided with a circular wall, the radius of the upper part of which is greater than the radius at the base. A more preferred chamber is conical in shape. The material and polymer particles are fed into the chamber at a rate that allows the polymer particles to be distributed in the mass of material. Nevertheless, in a more preferred embodiment, the material is directed into the conical mixing chamber at such a speed that a vortex funnel is created into which free-flowing polymer particles are poured, which allows the material and polymer particles to be thoroughly mixed together. The treated material should be removed from the mixing chamber using suitable means, such as a single screw pump. It is advisable to divert only part of the material (being processed) into the mixing chamber, in which it is combined with polymer particles, and then returned to the main pressure pipe through which the material is transported. In a preferred embodiment, the proportion of material discharged into the mixing chamber is less than 50%, more preferably from about 5 to 20%, preferably 10%.

When implementing the method in accordance with the invention, a product is formed that unexpectedly hardens much better than products of other treatments, for example, using water-swellable water-insoluble polymers or pre-prepared solutions of water-soluble polymers. It is also unexpected that particularly good results are achieved using polymers in the form of solid powder products, including a polymer in the form of a solid substance containing individual large polymer particles, as described herein. The implementation of the method according to the invention allows to more effectively reduce to a minimum the area occupied by a stack of material of a given volume. This is achieved while maintaining the ability of the material to pump.

An essential feature of the present invention is the characteristics of the restructured sludge. After the addition of a water-soluble polymer, the energy due to pumping, mixing, or friction in the transport pipeline causes the mixture to solidify to the maximum extent and gradually become less rigid. To permit satisfactory pumping, in a preferred embodiment, the slurry mixture has a plastic flow stress of less than 200 Pa, preferably less than 150 Pa, and more preferably from 20 to 120 Pa. One advantage of the powdered additives is that the viscosity does not increase or decrease as quickly as when adding solution-based products.

Another unexpected distinctive feature of the present invention is that after the material is transported to a preferred location and left in a calm state, an aqueous liquid is released from the solidified material. The advantage of releasing the aqueous solution from the material is that the slurry stack has a higher actual solids content and does not contain large amounts of trapped solution, as in the case of the use of a water-swellable, water-insoluble polymer. This creates advantages in that the destabilization of the stacked material becomes unbelievable, as well as in the fact that the released solution can be used again, for example, to extract all the remaining valuable substances. In the case of red mud from the Bayer process, the liberated solution can be returned to the Bayer process (for example, at the washing, thickening or recovery stage) to use the alkaline component, as well as all residual traces of aluminate.

When carrying out the invention, the material is pumped to the outlet, where it is allowed to spread over the surface of the previously hardened material, after which the material is left to stand and harden to form a stack. Since this process is repeated, many layers of hardened material are formed with the formation of a stack. Thus, the present invention also provides a product which, in a preferred embodiment, is in the form of a stack formed by the implementation of the method according to the invention, in particular according to any of the specific options listed.

According to another aspect of the present invention, there is provided a device for treating a suspension of material in the form of particles with a solid powder processing chemical substance, comprising means for removing the suspension from the pressure pipe and a mixing chamber that has a circular wall, openings in the upper part and base, and the radius of the upper part exceeds the radius of the base, the means for supplying the powdered processing chemical substance to the mixing chamber and the means of transportation processed suspensions from the mixing chamber.

The means for supplying the powdery processing chemical substance to the mixing chamber may be a suitable feeding mechanism or particle blowing means operating using a gas stream, such as air. Preferred means for supplying the powdered processing chemical to the mixing chamber include a screw feeder. A preferred device includes mechanical means for transporting the treated slurry from the mixing chamber. They can be any suitable pump, but in the preferred embodiment, it includes a single screw pump.

A schematic representation of a preliminary embodiment of this new device is presented in figure 2, for which the following key designations are used:

1 - pipeline for transporting material;

2 - pipe for material removal;

3 - flow control valve;

4 - mixing chamber;

5 - a container for a polymer;

6 - polymer particles;

7 - screw feeder;

8 - single screw pump;

9 - return pipe.

In the diagram, a material, such as red mud, is transported through line 1. A portion of this material is discharged through pipe 2 to divert material to the mixing chamber 4. The flow control valve 3 controls the flow of material sent to the mixing chamber. The polymer particles 6 contained in the polymer container 5 are fed into the mixing chamber using a screw feeder 7. The polymer particles and material are thoroughly mixed with each other, and then pumped out from the base of the mixing chamber using a single-screw pump 9, after which they are returned to the pipeline 1 through the return pipe 10.

In a preferred embodiment, the suspension is treated with a powdery processing chemical. The suspension may be any suitable suspension comprising dispersed particles and a liquid, for example, any material in accordance with the first aspect of the invention. A preferred suspension is an aqueous suspension of mineral particles containing at least 15% solid particles, for example from 20 to 80% solid particles. A more preferred slurry is a red slurry waste generated during the Bayer alumina recovery process. Thus, a method is provided in which the suspension is treated by mixing with a powder processing chemical substance, comprising transporting the suspension through a pressure pipe, withdrawing part of the suspension and feeding it into the mixing chamber, in which it is combined with the powder processing chemical substance, and then returned to the pressure pipe , characterized in that the suspension enters the mixing chamber and forms a vortex funnel into which the powder processing chemical th substance.

The implementation of the method in accordance with this object of the invention allows to overcome the difficulties of the technological order when mixing powdered processing chemicals directly into the processed suspension. This method is particularly effective for high solids content and / or high viscosity suspensions, when otherwise it would be difficult to ensure uniform distribution of the powdered processing chemical in the suspension mass.

This method is applicable by mixing any suitable powdered processing chemical into a highly viscous base. Preferred processing chemicals include a water-soluble polymer, for example, such as that described in the description of the first object of the invention. The particle size of the preferred processing chemicals is at least 20 microns, more preferably at least 50 microns.

The following examples serve to illustrate the invention.

Example 1

Before the centrifugation step from the last washing step, 1000 ml samples of condensed red mud are collected from the Bayer method in the aluminum oxide recovery process. The solids content of this sludge waste is 28.66%. A solid, powdery, water-soluble copolymer of acrylamide and sodium acrylate with a high intrinsic viscosity (about 10 dl / g) is added to these red mud slurry samples with different flow rates. In order to simulate a process with a normal duration of stay, due to the need to transport red slurry waste through the pipeline to the location, the treated slurry waste is carefully mixed for one hour in a laboratory tumbling drum. Next, samples of the treated slurry waste are poured onto a horizontal surface to obtain a sediment layer. This allows you to simulate the ability of slurry waste to form stacks. The diameter of the sludge is measured, the height of the sludge at its center, the height of the sludge at its edge, the slope of the edge of the sludge and the viscosity of the sludge; The results obtained are presented in table 1.

Table 1 Polymer consumption in grams of polymer / ton of sludge waste Diameter of sediment layer (mm) The height of the sediment layer in the center (mm) Sediment layer height along its edge (mm) Slope edge slope angle (%) Slurry Viscosity (cP) 0 205 7 four 2.92 142.6 fifty 190 8 4,5 3.68 142.6 one hundred 182 9 5 4.39 147.1 200 165 10 6 4.85 160,5 300 160 eleven 6 6.25 169.4 400 155 eleven 6 6.45 173.4

The data of this experimental work effectively confirm the overall results even at relatively low costs. So, for example, at a flow rate of 100 g / t, the angle of inclination of the edge of the sediment layer is greater than 3 °. It should also be noted that such a high angle of inclination of the edges of the sediment layer is achieved without any noticeable increase in the viscosity of this slurry waste.

Example 2

The test method of example 1 is carried out repeatedly using 1000-milliliter samples of a suspension of Australian slurry waste with a concentration of 35 wt.% At 10 g / l NaOH, conditioning for different periods of time using a Gate stirrer at a speed of 200 rpm and using constant 18 ppm each of a water-soluble copolymer of acrylamide and sodium acrylate with a high intrinsic viscosity (about 10 dl / g) in the form of a solid (with a particle size of about 1 mm) and a polymer as a product from braschennoy phase in the form of an oil dispersion of a water soluble copolymer of acrylamide and sodium acrylate of high intrinsic viscosity (about 10 dl / g), average particle size of 750 nm (at different conditioning periods). The angle of inclination of the edge of the sediment layer is measured for each conditioning period in cases of both a liquid dispersion and a polymer in the form of a solid.

The results are summarized in table 2.

table 2 Conditioning time (min) The angle of inclination of the edge of the sediment layer when using the dispersion of the polymer in oil (%) The angle of inclination of the edge of the sediment layer when using a polymer in the form of a solid (%) 0 3 3 one 9 four 2 fifteen 17 3 fifteen 19 5 fifteen 13 10 7 8 fifteen 6 7 twenty 5 5 thirty four four

The results in a graph are presented in figure 1.

It can be clearly seen that both the particles of the water-soluble polymer in the oil dispersion and the particles of the water-soluble polymer in the form of a solid provide effective results. You can also see that the use of the product in the form of a solid gives much improved results.

Example 3

The experiment of Example 1 is repeated using different amounts of a water-soluble copolymer of acrylamide and sodium acrylate in the form of a powdery solid with a high intrinsic viscosity (product A) introduced into 1000 milliliter samples of red mud (30.09% solids) at different rates, and using as a comparative test a powder of water-insoluble, water-swellable absorbent (product B). The stress of the plastic flow of the sediment, the angle of inclination of the edge of the sediment layer, the diameter of the sediment layer, the height of the sediment layer along its edge and the height of the sediment layer in its center are determined; the results obtained are presented in table 3.

Table 3 Product Consumption, g / t Plastic stress The angle of inclination of the edge of the sediment layer (%) Diameter of sediment layer (mm) Edge height of sediment layer (mm) The height of the sediment layer in the center (mm) Control 0 12.9 2,5 200 4,5 7 BUT 40 13.5 3,5 200 4,5 8 BUT 80 13,4 3,7 190 4,5 8 BUT 120 14.2 3.6 195 4,5 8 BUT 200 14.5 2.9 170 5.5 8 BUT 300 14,4 3.4 175 5 8 B 3800 16.8 3.3 180 5.5 8.5 B 1900 14.8 3,7 190 5 8.5

These results show that at least 3% effective slope of the edge of the sediment layer can be achieved by using only a moderate flow rate (40 g / l) of a water-soluble powder polymer, in contrast to an absorbent that is required in large quantities for this purpose (1900 g / t).

Example 4

The polymer A of example 3 is dispersed in a solution of calcium chloride with a concentration of 39 wt.% As an aqueous dispersion medium. Being in dispersion, polymer particles do not hydrate. It was found that the aqueous dispersion of polymer A is as effective as the particulate product.

Claims (11)

1. A method in which a material including an aqueous liquid with dispersed solid particles is pumped as a fluid, and then left to stand and solidify, and the solidification is improved while maintaining the ability of the material to pump by combining polymer particles with or during this pumping material, where the polymer particles include a water-soluble polymer that has an intrinsic viscosity of at least 3 dl / g and in which the polymer particles are in the form an aqueous dispersion comprising (a) a liquid dispersion medium, consisting mainly of a saline solution, which includes at least 25% inorganic salt, calculated on the total weight of the dispersion medium, and (b) a water-soluble non-ionic or anionic vinyl polyaddition polymer, which is insoluble in saline, where the polymer is derived from ethylenically unsaturated monomers, including acrylic acid or salts, optionally (meth) acrylamide and optionally at least one crosslinking monomer containing at least two polymerizable ethylenically unsaturated groups, and wherein the inorganic salt is a group II metal halide, or in which the polymer particles are in the form of a solid powder, which is added directly to the material. 2. The method according to claim 1, in which the water-soluble polymer is anionic and preferably derived from ethylene-unsaturated water-soluble monomer or a mixture of monomers, including (a) anionic monomers selected from ethylene-unsaturated carboxylic acid and / or sulfonic acid monomers, and optional (b ) nonionic comonomers, preferably selected from the group consisting of (meth) acrylamide, hydroxyalkyl esters of (meth) acrylic acid and N-vinylpyrrolidone. 3. The method according to claims 1 and 2, in which the average polymer particle size is less than 10 microns. 4. The method according to claim 3, in which the polymer particles are added to the material of the associated brittle aggregates of primary particles, the sizes of which are less than 10 microns, and the sizes of at least 90 wt.% Of these aggregates exceed 50 microns. 5. The method according to claim 1 or 2, in which the polymer particles are added to the material in the form of essentially individual particles, the sizes of which exceed 20 microns, preferably exceed 50 microns. 6. The method according to any one of claims 1 to 5, in which the dispersed solid particles of the material are mineral. 7. The method according to any one of claims 1 to 6, in which the sizes of the dispersed solid particles of the material are less than 100 microns, in which the preferred sizes of at least 80% of the particles are less than 20 microns. 8. The method according to claim 1, in which the group II metal halide is calcium chloride and the concentration of calcium chloride in the dispersed medium is at least 35%, preferably about 39%. 9. The method according to any one of claims 1 to 8, in which the solids content in the material is in the range from 15 to 80 wt.%, Preferably in the range from 40 or 50 to 70 wt.%, More preferably from 55 to 65 wt. .%. 10. The method according to any one of claims 1 to 9, in which the material is a red mud from the process of extraction of alumina according to the method of Bayer. 11. The method according to any one of claims 1 to 10, in which the material is pumped to the outlet, where it is allowed to spread over the surface of previously hardened material, after which the material is left to stand and harden to form a stack.

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