RU2266152C1 - Method of clarification of foam-containing suspensions - Google Patents

Abstract

FIELD: chemical technology, hydrometallurgy, treatment of waste water and industrial water containing surfactants, extracting agents and petroleum products.

SUBSTANCE: proposed method of clarification consists in filtering in downward direction under hydrostatic pressure through layer of fibrous charge followed by regeneration through loosening sludged layer by upward delivery of starting suspension and compressed air. Density of charge in loosened filtering layer is set within 35-50 kg/m³. During filtering, rarefaction is created above hydrostatic column of suspension within 6860-68600 Pa (0.07-0.7) kgf/cm² without use of evacuating units.

EFFECT: increased mud capacity; increased productivity of process; enhanced cleaning of solutions.

5 cl, 1 dwg, 2 tbl

Description

The invention relates to the field of chemical technology, hydrometallurgy, wastewater and industrial water treatment technology and can be used to clarify foam-containing low-concentration suspensions contaminated with organic impurities.

A known method of clarification of suspensions, including filtering at high speeds (up to 70 m / h) through a layer of fiber loading from the bottom up and regeneration of the sludge layer by loosening by feeding the bottom of the original suspension together with air (AS No. 1215212, class B 01 D 37 / 00).

The disadvantage of this method is that, despite the relatively high dirt capacity of the load, it is characterized by a low efficiency of clarification of the suspension. This method can be recommended for pre-clarification of suspensions or in cases where there is no need to obtain clear solutions.

A known method of clarification of industrial wastewater, including filtering through a layer of granular load from top to bottom and regeneration of the sludge layer by loosening by supplying bottom wash water and compressed air (AS No. 936963, class B 01 D 24/46). A distinctive feature of the known invention is that in order to increase the efficiency of loosening before regeneration for a short period of time, a high vacuum of at least 6 · 10 ⁴ Pa (0.61 kgf / cm ² ) is created above the clogged loading layer to isolate dissolved in water gases, and the filtering process is carried out under pressure.

The disadvantage of this method is that it is characterized by low rates of dirt capacity and the efficiency of cleaning from carbon-containing impurities (surfactants, oil products and extractants). The disadvantage of this method also lies in the fact that to create a vacuum use expensive equipment - a vacuum pump and receiver, which are in operation for a very limited time.

The closest in its technical essence and the achieved effect to the proposed invention is a method of clarification of suspensions, including filtering through a layer of fibrous load under hydrostatic pressure in the direction from top to bottom and regeneration by loosening the fibrous load by supplying washing water and compressed air from below. This method is implemented in a known device (AS No. 787061, class B 01 D 23/24) and is considered as a prototype.

The disadvantage of this method is that it is characterized by relatively low dirt capacity and performance (filtering speed up to 5 m / h), as well as low efficiency in the cleaning of foam suspensions, including oil products, extractants and surfactants (surfactants).

The problem solved by the invention is to increase the dirt capacity and productivity of the process of clarification of foam-containing suspensions and increase the efficiency of cleaning solutions from extractants, surfactants and petroleum products.

The technical result is achieved in that the loading density of the fibrous material in the loosened filter layer is set within 35-50 kg / m ³ , and when filtered over a hydrostatic suspension column, a vacuum is created within 6860-68600 Pa (0.07-0.7 kgf / cm ² ). To create a vacuum and a hydrostatic column, the message with the atmosphere of the space filled with the suspension above the loading layer is closed and at the same time open a free outlet for the clarified solution.

The initial (ΔР ₀ ) and final (ΔРτ) rarefaction values are selected taking into account the concentration of the gas phase in the suspension and foam stability, and the permissible change in the height of the hydrostatic column (ΔН _hydr. , M) is determined by the formula:

where H ⁽⁰⁾ _hydr. and H ^(τ) _hydr. - values of the height of the hydrostatic column of the suspension at the initial moment of filtration and at the current time;

N _g.s. - the height of the rarefied gas layer formed by filtering the suspension in the upper part of the clarifier, m;

g = 9.8 m / s ² - acceleration of gravity;

ρ _s - the density of the suspension, kg / m ³ .

For a given height (N _os. , M) and area (S _oc. , M ² ) of the clarifier apparatus, the height of the loosened filter layer (N _f.s. ) and the mass of the fibrous load (m _zag. , Kg) are set based on the permissible change rarefaction during the filtering process (ΔΔР = ΔР ₀ -ΔР _τ ) and the indicated density values of the loosened filter layer (δ _f.s. , kg / m ³ ) according to the formula:

For coalescence of organic contaminants, polypropylene fiber is used as the loading material.

In industrial practice, in most cases, the task arises of clarifying precisely foam-containing suspensions and wastewater, in which foam is formed due to the presence of surfactants, extractants and oil products in it. When such suspensions are mixed and pumped by centrifugal pumps, due to the dispersed air getting into them, a foam forms, which makes it difficult to carry out the processes following the clarification operation (for example, evaporation or extraction). When clarifying wastewater, in addition to cleaning from suspensions, the content of these harmful impurities should also be minimized to achieve the total necessary treatment before discharging treated water into a sewer or fisheries.

In order to achieve highly efficient cleaning of foam-containing suspensions from both solid suspensions and carbon-containing (including organic) impurities, it is proposed to use the loosening of the fibrous material in the upward flow of the suspension, air or water vapor to a loading density in the loosened filter layer of 35-50 kg / m ³ . The need for the operation of loosening the filter layer to the indicated density values is associated with the heterogeneity of the fibrous material, in which, along with the active zones (fine-fiber clumps-collectors of suspensions), relatively ineffective fiber bundles are present. This makes it possible to achieve a uniform distribution of fine-fibrous clumps over the filtering layer, fixing in themselves suspensions and organic impurities, and thus increase the dirt capacity with high quality filtrate. On the other hand, when loosening using compressed air or water vapor, the loading of fibrous material from contamination is regenerated.

Increasing the dirt capacity of the filter layer increases the total time of the filtering cycles and reduces the number of regeneration (loosening) cycles, that is, the performance of the clarification process increases. Simultaneously with a high clarification effect, the suspension of carbon-containing impurities is improved if during the entire filtering cycle a vacuum is created above the suspension layer to destroy the foam under vacuum. When the initial suspension enters the vacuum space above the suspension column, a flotation process occurs, partial destruction of the foam, the release of air bubbles, as well as associated particles of surfactants, extractants and oil products that remain in a floating state on the surface of the suspension. Carbon-containing products coarsen and coalesce on a fiber charge and are retained with greater efficiency in it. In practice, it is advisable to maintain the current vacuum (ΔP _τ ) within 6860-68600 Pa (0.07-0.7) kgf / cm ² . Air bubbles entering the fiber nozzle reduce filtration efficiency. Therefore, contact of the rarefied gas layer with the filter layer is unacceptable, and air supply is advisable only in the nozzle regeneration cycle.

Unlike analogues, the clarifier under consideration combines two interconnected parts of the clarification process: removal of the gas phase from the suspension into the foam layer (flotation) with its subsequent destruction and filtration-coalescence of contaminants on the fibrous material of the filter layer. To achieve the main objectives of the invention, it is necessary to select the spatial distribution parameters in the apparatus of the corresponding working areas and the optimal regulation parameters of these parts of the clarification process.

The optimal volume of rarefied gas in the apparatus is determined by the permissible change in rarefaction from the initial (ΔР ₀ ) to the final (ΔР _τ ), which ensures that the contaminated foam layer or rarefied gas phase does not come into contact with the loosened filter layer. The latter sticks together and loses homogeneity under the influence of the gas medium and organic impurities, due to which a slip of the solid phase occurs and the resistance of the fibrous material rapidly increases. The values of (ΔP ₀ ) and (ΔP _τ ) are selected from the indicated interval, the larger, the higher the concentration of gas in the clarified suspension and the higher the stability of the foam. In this case, the formula is used:

where ΔΔР _τ = ΔР ₀ -ΔР _τ is the change in vacuum when filtering the suspension, Pa;

g is the acceleration of gravity, m / s ² ;

ρ _s - the density of the suspension, kg / m ³ ;

X is the volume fraction of the gas phase in the suspension;

V _c. - flow rate of clarified suspension, m ³ / h;

τ is the process time, hour;

S _os. - area of clarifier, m ² .

The limitation here is the acceptable dimensions of the equipment, as with increasing (ΔР ₀ ), the initial height of the hydrostatic column of the suspension increases in accordance with the formula ΔP ₀ = g · ρ _s. · N ⁰ _hydr. . Therefore, in industry more often (preferably) they work in a narrower range of rarefaction values of 9800-29400 Pa (0.1-0.3 kgf / cm ² ). The selected initial height of the hydrostatic column sets the position of the upper level of the U-shaped drain pipe (see drawing). The height of the loosened filter layer, spatially highlighted by the restrictive mesh, is determined by the formula:

and depends on the selected height of the gas layer:

The high efficiency of the filtering operation is ensured by the optimal height of the filter layer and its density in the range of 35-50 kg / m ³ . For this, the optimal loading mass of fibrous material is calculated by the formula:

The proposed method is as follows (see drawing).

Before starting the filtration, the calculated amount of fibrous material, for example, made of polypropylene, is placed in layer 1 on the distribution grid 4 in the housing 2 of the clarifier apparatus, closed on top by a cover 13 with pipelines 9, 11 and valves 8, 10. A vacuum gauge 12 is also installed on the cover. Further open the valves 8, 10 and close the valves 3, 7, 14, 19 and briefly turn on the centrifugal pump 18 to supply the initial suspension from the tank 17. After filling the clarifier apparatus with a suspension and starting to pour it back into the tank 17, it is loosened a layer of fibrous material by feeding from below the initial suspension at a speed of 20 m / h and compressed air with a flow rate of 120-150 m ³ / m ² · h (water vapor can be supplied instead of air). To do this, shut off valves 8, 10 and open valves 3, 14 and 19. When a slurry and compressed air are supplied from below, the layer of fibrous material expands and is evenly distributed with an optimal density of 35-50 kg / m ³ over the entire volume from the distribution grid 4 to the boundary grid 15, which prevents the entrainment of fibrous material and separates the filter layer from the volume of rarefied gas in the filtration cycle.

Next, after expanding the fiber layer, close valves 3, 14 and 19 and open valves 8 and 10, turn on the centrifugal pump 18, close valve 10 and open valve 7 to allow the solution to flow freely through the space 5 under the grate 4 and the U-shaped pipe 6. At the same time, under the cover of the clarifier in the space above the suspension column, a vacuum is created, which is recorded and measured using a vacuum gauge 12. The upper part of the U-shaped pipe 6 is placed below the level of the restrictive grid 15 so that the value is rarefied Iya balanced the pressure of the hydrostatic column of the suspension, determined by the lower mark of the vacuum space and the upper mark of the U-shaped pipe 6.

Then, an initial suspension is fed to the clarifier by means of a centrifugal pump 18 through a vacuum space 16 with a certain flow rate not exceeding the flow rate of self-draining. When the suspension moves through the fibrous layer under the hydrostatic pressure of the suspension column, suspension is suspended, and the clarified solution exits through a U-shaped pipe 6. As the filter is filtered, a foam layer forms on the surface of the suspension column, which partially breaks up under the influence of vacuum. With the destruction of the foam layer and the release of air bubbles, a decrease in rarefaction occurs, and the particles of graphite, extractants, surfactants, and oil products released from the foam float on the surface of the liquid column.

During filtering, the fibrous material is clogged, the layer is heavier and its height is reduced. The height of the hydrostatic column of liquid also decreases. In the case of a high foam content in the initial suspension and a relatively rapid decrease in vacuum for a short period of time, open the valve 10, close the valve 7 and fill the remaining free space with the initial suspension, i.e. restore the hydrostatic column. Next, using valves 10 and 7 again create a vacuum. As you filter, slurry layer 1 and increase its resistance, a decrease in the performance of the clarifier. In this case, the feed of the initial suspension is turned off, valves 7, 8 are closed, valves 3, 14, 19 are opened and the fiber layer is regenerated by supplying the initial suspension and compressed air from below. Carbon-containing products floating on the surface are removed first, the layer is intensively mixed, expanded, and suspensions are removed from the layer through a pipeline through valve 14 to a receiving tank for further processing. After regeneration of the layer, the filtering cycle is repeated.

An example of the process on a model installation.

The study of the regularities of the clarification process was carried out on a model clarifier apparatus with a diameter of 60 mm and a height of 1.35 m, made of transparent plexiglass. A production suspension with a density of 1.25-10 ³ kg / m ³ formed in the uranium technology and characterized by the presence of oil products, surfactants and extractants was used as the initial one. The average suspension content in the suspension is 50 mg / dm ³ , and the concentration of gas bubbles in the suspension is about 0.1 vol.%, And the foam layer becomes unstable in 1-2 minutes at atmospheric pressure. Under such conditions, a large vacuum was not required, therefore, they worked in the range of vacuum values of 6860-9800 Pa (0.07-0.1 kgf / cm ² ). The upper level of the U-shaped discharge of the clarified solution is located at a height of 0.6 m, then the initial height of the hydrostatic column is:

N ⁽⁰⁾ hydr. = 1.35 m -0.6 m = 0.75 m, and the initial vacuum is:

ΔP ₀ = 9.8 m / cm ² · 1.25 · 10 ³ kg / m ³ · 0.75 m ≈9200 Pa (0.094 kgf / cm ² ).

The height of the gas layer N _g was set equal to 0.15 m, and the height of the loosened filter layer under the restriction grid was equal to 1.20 m, which corresponds to the permissible final vacuum ΔР _τ = 7350 Pa (0.075 kgf / cm ² ). With this value of ΔР _τ , it is guaranteed that the fibrous material during the filtration process will be below the liquid level and will not stick together under the influence of air and organic contaminants. The obtained value of ΔР _τ is sufficient for the effective collapse of gas bubbles entering the pulp. Polypropylene fiber was used as the fiber loading layer (technical specifications TU 2272-007-576624-93).

The dependence of the filtration process productivity, dirt capacity, clarification efficiency, the duration of the filtration cycle and the content of organic impurities in the filtrate on the loading density of the fibrous material in the loosened filtering layer was investigated. To do this, in an empty apparatus in a layer of constant height of 0.6 m was loaded fiber material with different densities, from 50 to 140 kg / m ³ . A denser load was created by forced compression, less dense - by freely laying the fibers on the distribution grid. With these different loads, complete filtration and regeneration cycles were performed.

Filtration in all experiments was carried out with the same maximum speed of 20 m / h. An increase in this parameter to values greater than 20 m / h led, on the one hand, to the passage of solid suspensions through the filter layer (in the filtrate more than 10 mg / dm ³ ), and on the other hand, worsened the regeneration of the fibrous nozzle due to its excessive compaction under squeezing the flow and sticking of contaminated fibers.

The initial suspension flow rate was 56.4 dm ³ / h, the compressed air flow rate was 120-150 m ³ / m ² · h, the compressed air pressure was 68600 Pa (0.7 kgf / cm ² ), the regeneration time was 1 hour. The rarefaction value in the apparatus was set at 6860 ÷ 9800 Pa (0.07 ÷ 0.1 kgf / cm ² ). In industrial filtering, the rarefaction value is set with large values - 9800 ÷ 68600 Pa (0.1 ÷ 0.7 kgf / cm ² ).

Filtering cycle: the time of the steady-state filtration process with a constant pulp flow rate of 56.4 dm ³ / h (table 1 - 18.1 ÷ 30.5 h / cycle). With a noticeable increase in the concentration of suspensions in the filtrate and / or a decrease in consumption due to an increase in the resistance of the contaminated fiber nozzle, the above regeneration was carried out for 1 hour, then the filter was prepared for a new filter cycle up to 0.5 hours. The total cycle of regeneration and preparation was about 1.5 hours. When calculating for 1 month, 30 working days and 8 working hours per day were taken, i.e. the period of the total filtration and regeneration-preparation cycle is 3–4 days / cycle, and the number of such cycles is 7.5–10 cycles / month.

In the process of regeneration and loosening of the layer in a transparent apparatus, a uniform distribution of fiber in the layer over its entire height was clearly observed with a density of the loosened layer from 35 to 50 kg / m ³ . At a density of more than 50 kg / m ^{3, the} filter layer loosened unevenly: the lower layers of the charge did not expand, were characterized by greater compaction and included suspensions that were poorly removed from the layer during regeneration. When the density of the loosened filter layer is less than 35 kg / m ^{3 the} subsequent formation of the filter layer does not allow to obtain the uniformity of the layer necessary for effective filtering, because in these cases, there is the possibility of axial rotation, twisting into strands of the stretched fiber, which leads to a decrease in dirt capacity and the passage of polluting particles with a clarified solution.

From the data of table 1 it follows that when loosening the fibrous material in the layer to a density of 35 to 50 kg / m ^{3 the} maximum dirt capacity was achieved, the operating time of the clarifier was the greatest and, accordingly, the performance of the clarifier in case of continuous operation for a long period (1 month ) was maximum. At a density of less than 35 kg / m ^{3, the} layer after regeneration and expansion was characterized by high porosity, as a result of which its ability to retain suspensions decreased (the average content of suspensions in the clarified liquid increased to 7–10 mg / dm ³ ). At a density in the loosened state of more than 50 kg / m ^{3, the} lower layers of fibrous material during regeneration expanded to a lesser extent than the upper ones, the porosity of the layer in the lower part was also lower, and suspensions from such a denser layer are less tolerated. In the case of denser packing, the loosening of the fiber layer did not turn out to be uniform over its entire height. When creating a fiber layer with a density of 35 ÷ 50 kg / m ^{3, the} expansion of the layer over its entire height during regeneration turned out to be relatively uniform, while the layer was characterized by a high retention ability. The average suspension content in the filtrate was 3 ÷ 4 mg / dm ³ .

We also studied the process of clarification of the suspension without creating a vacuum over the fiber layer (as in the prototype) and compared with the proposed method. The research results are presented in table.2.

table 2 The results of the process of cleaning the solution from carbon-containing impurities when filtering the initial suspension through a layer of fibrous material (average content in the initial suspension, mg / dm ³ : oil products - 40; extractants - 47; surfactant - 23) Filter conditions The content in the filtrate, mg / DM ³ oil products extractants Surfactant The known method (prototype): layer density - 40 kg / m ³ ; material - lavsan. 31 33 eighteen The proposed method: filtering under vacuum; layer density - 40 kg / m ³ ; material - polypropylene. 19 twenty 14

From the data of Table 2 it follows that the creation of rarefaction over the layer of fiber loading allowed to reduce the content of carbon-containing impurities in the filtrate. The choice of the lower rarefaction boundary of 6860 Pa (0.07 kgf / cm ² ) is due to the fact that, at lower rarefaction values, the efficiency of the release of gas bubbles into the foam layer sharply decreased, especially at maximum filtration speeds of about 20 m / h. The upper boundary of the rarefaction was chosen at the level of 68600 Pa (0.7 kgf / cm ² ) due to the fact that higher values led to a significant enlargement of the dimensions of the clarifier, and the cost of its operation increased. Really:

those. the total height of the clarifier can be more than 10 meters. As already noted, the interval of rarefaction values 9800 ÷ 29400 Pa (0.1 ÷ 0.3 kgf / cm ² ) was mainly used.

It should be noted that the distinguishing features of the invention - "the loading density in the loosened filter layer is set within 35 ÷ 50 kg / m ³ , and when filtered over the hydrostatic column of the suspension create a vacuum ..." - are interconnected and are in unity when obtaining a common positive effect . The height of the space which is under vacuum _g.sl. H , affects the choice of the optimal height of the loosened filter layer (N _f.s. ) in accordance with the above formulas, as well as its porosity and retention ability. With increasing rarefaction, the height of the space for collecting rarefied gas increases, and the height of the layer of fibrous material decreases, which at a given loading density of the fiber in the expanded state leads to a decrease in the loading mass and, as a result, to the passage of impurities through the clarifier together with the filtrate.

From the data of table 2 it is seen that at the same density of the fibrous load, the best results for cleaning from organic contaminants were obtained in the case of using polypropylene fiber, rather than lavsan (polyester) as in the prototype. The reason for this phenomenon is that the density of the polypropylene fiber (material) is 0.91 ÷ 0.92 g / cm ³ and the lavsan is 1.38 g / cm ³ [Brief chemical encyclopedia. M., 1965, v. 4]. At the same fiber loading density (for example, 40 kg / m ³ ), the volume of polypropylene in the loading is greater than the polyester. At close values of fiber diameters, this means that the surface area of polypropylene fibers is higher, and therefore the adsorption activity is greater. Thus, the coalescence of organic droplets is in this case an essential factor in the purification of suspensions.

An example of industrial implementation.

The suspension formed in the uranium technology was clarified after the process of dissolution of solid uranium-containing materials with nitric acid, thickening of the pulp, control filtration of the top thickener discharge on sheet filters and subsequent control sedimentation of the filtrate. This resulting suspension contains petroleum products, extractants and surfactants, which are used in the preparation of the starting solid material in previous technologies.

The initial suspension can be classified as difficult to clarify, because due to the high salt composition of the liquid phase and the wide variety of suspension composition when flocculants are added, complete flocculation and sedimentation of the solid phase does not occur. Part of the solid does not bind to flocs. Even after three operations — sedimentation, control filtration and control sedimentation — the average suspension content in suspension is 25–50 mg / dm ³ , and the foam content is 0.1–1.0 vol%.

When the solid material was dissolved in nitric acid, the phenomenon of foaming was observed due to the presence of surfactants in the pulp, carbon-containing products, and its frequent pumping and mixing. Since the clarified solution should be supplied to the extraction operation according to the technology, they achieved its maximum clarification and purification from carbon-containing impurities and surfactants. Otherwise, in the extraction operation upon contacting contaminated solutions, hard-to-exfoliate emulsions formed.

When clarifying the suspension, a clarifier was used with a diameter of 0.8 m (S _os. = 0.5 m ² ) and a height of H _os. = 4.0 m. The apparatus was loaded with fibrous material from polypropylene, creating an initial dry charge density of 97 kg / m ³ . The initial height of the loading layer before filtering is 1.5 m.

After filling the apparatus with a suspension with a density of 1.25 · 10 ³ kg / m ³ and expanding the loading layer by supplying a suspension and compressed air from below, an initial rarefaction ΔР ₀ = 24500 Pa (0.25 kgf / cm ² ) was established by opening a free exit filtrate through a U-shaped pipeline and closing the communication with the atmosphere of space above the liquid in the apparatus. The initial height of the hydrostatic column of the suspension is:

The upper mark of the U-shaped pipeline was at a height of 2.0 m from the bottom of the apparatus. The loading density of the fibrous material after loosening was 48.5 kg / m ³ . The final vacuum ΔР _τ was taken equal to 12,250 Pa (0.125 kgf / cm ² ), which allowed us to establish the optimal ratio of the heights of the rarefied gas layer (N _g.s. ) and the loosened filter layer (N _f.s. ) under the restrictive mesh with an optimal load weight fibrous polypropylene:

The flow rate of the initial suspension into the apparatus was set at 10 m ³ / h. The filtration rate was 20 m / h. At such a constant speed, the filtration cycle time reached ~ 300 hours before regeneration. The restoration of the hydrostatic column (dilution) was performed 1 time in 1-2 days, depending on the amount of foam in the pulp.

или 40÷90 кг/м³, что в целом выше, чем в прототипе. После окончания цикла фильтрования проводили регенерацию зашламленного волокнистого материала подачей снизу исходной суспензии и сжатого воздуха в течение 1 часа. Расход исходной суспензии при регенерации составлял 7 м³/ч, расход сжатого воздуха при давлении 68600 Па (0,7 кгс/см²)-150 м³/м²·ч. В результате процесса фильтрования исходной суспензии с концентрацией твердых взвесей 25÷50 мг/дм³ получали прозрачный раствор со средним содержанием взвесей 3÷4 мг/дм³. Одновременно с осветлением раствора происходило существенное снижение содержания в нем углеродсодержащих примесей. При исходном среднем содержании в суспензии нефтепродуктов 40 мг/дм³, экстрагентов - 47 мг/дм³, ПАВ - до 23 мг/дм³ среднее содержание этих примесей в осветленном растворе составляло, соответственно, 18÷19, 20÷22 и 12÷14 мг/дм³. Получающийся при фильтровании осветленный раствор удовлетворял требованиям последующего процесса экстракции.The dirt capacity, which was controlled by determining the content of suspensions in the initial and final solutions, was

or 40 ÷ 90 kg / m ³ , which is generally higher than in the prototype. After the completion of the filtering cycle, the regeneration of the sludge-like fibrous material was carried out by feeding from below the initial suspension and compressed air for 1 hour. The flow rate of the initial suspension during regeneration was 7 m ³ / h, the flow rate of compressed air at a pressure of 68600 Pa (0.7 kgf / cm ² ) -150 m ³ / m ² · h. As a result of the filtering process of the initial suspension with a concentration of solid suspensions of 25 ÷ 50 mg / DM ³ received a clear solution with an average content of suspensions of 3 ÷ 4 mg / DM ³ . Simultaneously with the clarification of the solution, there was a significant decrease in the content of carbon-containing impurities in it. At the initial average content of 40 mg / dm ^{3 of} oil products in the suspension, 47 mg / dm ^{3 of} extractants, and surfactants up to 23 mg / dm ^{3, the} average content of these impurities in the clarified solution was 18 ÷ 19, 20 ÷ 22, and 12 ÷, respectively 14 mg / dm ³ . The clarified solution obtained by filtration met the requirements of the subsequent extraction process.

When analyzing the scientific, technical and patent literature, methods for clarifying foam-containing suspensions having the entire set of essential features of the claimed invention were not identified.

Moreover, the set of related distinctive features does not explicitly follow from the prior art, especially since the relationship between some parameters of the clarification process regulation (δ _f.s. , _{ΔР 0} , ΔР _τ , m _zag. ) And structural (overall) parameters (N _hydr , N _f.sl. , N _{OS .} , S _{OS .} ) Is presented in the form of mathematical dependencies obtained in the process of creating the invention.

The method is introduced into commercial operation in the process of hydrometallurgical processing of uranium-containing raw materials at the stage of preparation (clarification) of the initial solutions for extraction. EFFECT: increased dirt capacity and productivity of the process, as well as the degree of purification of solutions from organic impurities and the efficiency of subsequent extraction, respectively, and product quality.

Claims (5)

1. A method of clarifying foam-containing suspensions, including filtering them under hydrostatic pressure from top to bottom through a loading layer of fibrous material and subsequent regeneration by loosening the slurry fiber by supplying the initial suspension and compressed air from below, characterized in that the loading density is set within the loosened filter layer within 35 ÷ 50 kg / m ³ , and when filtering over a hydrostatic column of a suspension, a vacuum is created within 6860 ÷ 68600 Pa (0.07 ÷ 0.7 kgf / cm ² ). 2. The method according to claim 1, characterized in that in order to create a vacuum and a hydrostatic column, the communication with the atmosphere of the space filled with the suspension above the loading layer is closed and at the same time open a free outlet for the clarified solution. 3. The method according to claim 1, characterized in that the initial and final vacuum values are selected from the specified interval taking into account the concentration of the gas phase in the suspension and the stability of the foam, and the permissible change in the height of the hydrostatic column when filtering the suspension is established by the formula

where ΔН _hydr is the permissible change in the height of the hydrostatic column; N ⁽⁰⁾ _hydr and H ^(τ) _hydr - values of the height of the hydrostatic column of the suspension at the initial moment of filtration and at the current time, m; ΔР ₀ -ΔР _τ - change in vacuum when filtering the suspension, Pa; g = 9.8 m / s ² - acceleration of gravity; ρ _{with the} density of the suspension, kg / m ³ ; N _g.sl - the height of the rarefied gas layer formed by filtering the suspension in the upper part of the clarifier apparatus, m 4. The method according to claim 1, characterized in that for a given height and area of the clarifier apparatus, the height of the loosened filter layer and the mass of the fibrous load are set based on the allowable change in vacuum during the filtering process and the indicated values of the density of the filter layer according to the formula

where N _OS - the height of the apparatus-clarifier, m; N _f.sl - the height of the loosened filter layer, m; m _zag - the optimal loading mass of fibrous material, kg; S _OS - the area of the apparatus-clarifier, m ² ; δ _f.sl - the density of the loosened filter layer, kg / m ³ . 5. The method according to claim 1, characterized in that for the coalescence of organic pollutants, polypropylene fiber is used as the fibrous material.