RU1838238C - Method for hydrochemical processing of alunite - Google Patents

Abstract

Usage: in the processing of alumina-containing raw materials, in particular - alunite. SUBSTANCE: raw or reduced alunite is treated with a working alkaline solution, the elunite sludge is separated and washed, the aluminate solution is desalinated and subjected to control filtration. The solution was evaporated to isolate sulphate salts and separated from the one stripped off, the latter was diluted with a blank of alunite sludge. The aluminate solution is decomposed to obtain aluminum hydroxide, promoters of aluminum hydroxide and the mother liquor used as a working alkaline solution in the processing of alunite. The resulting aluminum hydroxide is calcined. An aluminum hydroxide promoter with a concentration of 5-35 g / l Na-20k is treated with lime in an amount of 4.2-17.7 g / l CaO to obtain a phosphorus-containing precipitate and feed it to wash alunite sludge by mixing it with pulp having a concentration of the liquid phase TH - 30 g / l according to Na20K. 7 tab. SB with

Description

The invention relates to hydrochemical methods for processing alumina-containing raw materials, in particular alunite.

The practical processing of aluminate solutions supersaturated with sodium phosphate on alumina involves the crystallization of sodium phosphate also on the walls of technological equipment and pipelines, which causes increased labor costs for cleaning the equipment with the removal of phosphorus salt build-up on the sludge field.

Using the method of geochemical correlation, it was found that phosphorus in alunites is contained in the form of the phosphosiderite mineral FeP04-2H20. In the process of leaching of alunite, phosphorus partially passes into the solution by the reaction:

FeP04-2H2O + 3NaOH

 No. ZR04 + Re (OH) s + 2H2O (1)

With the degree of extraction of phosphorus in the aluminate solution, 40.3% of the content in alunite containing 0.169 wt.% P20s and the specific consumption of crude alunite per 1 t A 20 sfd. at the level of 7483.7 kg, the loss of caustic alkali due to leaching of phosphorus is 6.71 kg of NaizO per 1 ton of production alumina or about 1.9 thousand tons per year of MaOH with an annual capacity of 220 thousand tons of alumina, which is is significant. This amount of caustic alkali is irretrievably lost.

The purpose of the invention is to reduce the cost of caustic alkalis and to reduce the impurity content of phosphorus oxide in production alumina.

with

w u

CA

CA)

This goal is achieved in that in a method for the hydrochemical processing of alunite, comprising treating raw or recovered alunite with a reverse alkaline solution, separating and washing the alunite sludge to obtain an aluminate solution and introducing waste alunite sludge, demineralization of the aluminate solution and control filtration with subsequent evaporation and the allocation of sulfate salts, separating them from one stripped off solution, dilution of the latter with the help of waste alunite. sludge and decomposition with the production of aluminum hydroxide, promotions of aluminum hydroxide and the mother liquor directed to the processing of alunite, calcination of aluminum hydroxide to obtain production alumina, according to the invention, the production of aluminum hydroxide obtained after decomposition of the aluminate solution, with a concentration of 5 - 35 g / l of 1 ArOK are treated with lime introduced in an amount of 4.2 - 17.7 g / l of CaO, and the phosphorus-containing precipitate obtained is sent to an alunite sludge washing system for mixing with a pulp having an end ntration of the liquid phase 10-30 g / l according to N320.

The laboratory studies, the results of which are confirmed by industrial data, established the dependence of the content of phosphorus (V) oxide in calcined alumina on the concentration of phosphorus in the solution fed to decomposition during processing of alunite raw materials (Table 1). The concentration of the main components in the initial solution entering the decomposition was: 100-125 g / l NaaOK; 30 - 50 g / l ZOz; “To 2.0 - 2.1; % mol, K of the amount K + No. 18-35.

A sharp increase in the phosphorus content in alumina at a concentration of the initial solution of 4.0-4.5 g / l PaO3 is associated with the onset of crystallization of sodium orthophosphate together with aluminum hydroxide. When the concentration of phosphorus oxide in the aluminate solution of the decomposition sphere is less than 4.3 - 4.1 g / l, high-quality alumina is formed containing less than 0.002 wt.% PaOs. .

It was found that the alumina hydroxide wash obtained after decomposition of the aluminate solution at the stage of washing the production aluminum hydroxide with water is most enriched in sodium phosphate, relative to the concentration of MaaOc, in comparison with alkaline aluminate solutions at any stage of alunite hydrochemical processing.

Aluminum hydroxide promoter is a weak alkaline aluminate solution with

concentration of 5-50 g / l according to No. AOK and a caustic module of 3.9 - 4.1, which is formed during the processing of alunite raw materials in an amount of about 1 - 2 m3 per 1 t A Ozprod. Concentration of P20s in the promoter is 1.5-5 g / l.

The mass ratio of the concentrations of phosphorus oxide and No. 20k in the alumina hydroxide promoter is 3–4 times higher than in the mother liquor after decomposition, which is caused by the dissolution of sodium phosphate released together with aluminum hydroxide and the desorption of orthophosphate ion adsorbed during decomposition.

It was experimentally established that by treating promoters of aluminum hydroxide with a concentration of 5-35 g / l according to No. 20k with lime, introduced in an amount of 4.2 - 17.7 g / l according to CaO, phosphorus can be isolated into the solid phase simultaneously

by caustification of sodium phosphate according to the reaction:

2№зР04 + ЗСа (ОН) 2

 Saz (P04) 2 + 6NaOH (2)

At the same time, there is a reaction of formation of calcium hydroaluminate:

35

2№А (ОН) 4 + ЗСа (ОН) 2

 ZSaO-A120z-6N20 + 2MaON (3)

The processing temperature is 70 - 90 ° C, the duration is 2 to 4 hours. At a lower temperature and duration, the process of phosphorus precipitation does not proceed fully, and at a higher temperature the degree of phosphorus precipitation does not increase, but the specific investment is increased due to the complexity and increase in the number of equipment.

5 using the crystal-optical research method and electron microscopy method, it was found that precipitates obtained after treatment with lime promoted aluminum hydroxide are represented

0 particles having dense outer shells, consisting mainly of calcium hydroaluminate, shielding reactive calcium hydroxide located in the center of the particles from the surrounding solution. Calcium phosphate is located mainly in the inner sphere of the particles. Due to this, when phosphorus is deeply precipitated to a concentration of 0.05 - 0.2 g / L PaOs, at the end of the process, the phosphate ion does not diffuse to the particle center due to the low concentration of phosphate ion and due to the presence of a protective layer of calcium hydroaluminate. As a result, the full effective use of the reagent does not occur, and the phosphorus-containing precipitate obtained contains a significant amount of alumina; (4-7 wt.%).

Studies have shown that when processing a phosphorus-containing precipitate obtained by treating lime with an aluminum hydroxide promoter with a weak aluminate solution with a concentration of 10-30 g / L at No. 20k containing sodium phosphate, there is an exchange interaction of calcium hydroaluminate contained in the precipitate with phosphate sodium present in the solution, as a result of which aluminum from the precipitate passes into the solution, and phosphorus from the solution goes to the precipitate with simultaneous caustification of sodium phosphate by the reaction:

ZSaO-A120z-6N20 + 2N32P04

 Saz (P04) 2 + 2NaAI (OH) 4 + 4NaOH (4)

This process is accompanied by the destruction of the dense shells of calcium hydroaluminate on the particles of the phosphate precipitate, as a result of which the effective diffusion of the phosphate ion from the solution to the center of the particles, represented by reactive calcium hydroxide, begins with the formation of calcium phosphate according to reaction (2). At the same time, the degree of useful use of lime significantly increases, losses of aluminum with a phosphorus-containing precipitate are reduced to a minimum, the amount of phosphorus in the precipitate increases, and an additional amount of caustic alkali is formed.

The amount of lime added and the concentration of caustic alkalis in the reaction sphere are of decisive importance for the efficient progress of phosphorus precipitation reactions (2), (4).

The processing temperature of the phosphorus-containing precipitate with a weak aluminate solution of 50 - 90 ° C, the duration of 4 - 12 hours.

It is advisable to treat the phosphorus-containing precipitate obtained after the lime treatment with the aluminum hydroxide promoter with a weak aluminate solution containing sodium phosphate by directing the precipitate or pulp into the alunite sludge washing system. In alumina production technology, a six-fold countercurrent washing of alunite sludge is usually carried out with water supplied to the washing in the last stage and thickened alunite sludge in the first. The liquid phase of the slurry pulp has different concentrations at different washing stages, respectively,

 60 to 1.5 - 2 g / l and a concentration of P20s. according to the mass ratio of the concentrations of P20g: Na20K 0.03-0.04, caustic module 2 2.2. It is advisable to direct the phosphorus-containing precipitate (or

0 pulp) in the third to fourth stages of washing alunite sludge with a concentration of the liquid phase of 10-30 g / l

No. 20k.

Thus, the conclusion

5 of the total amount of phosphorus entering the aluminate solution during the leaching of alunite from the hydrochemical cycle of alumina production. Moreover, about 55% of the total amount of precipitated phosphorus is removed from the aluminum hydroxide promo- ses at the stage of lime treatment, and about 45% at the stage of the interaction of the phosphorus-containing precipitate with the liquid pulp phase in the alunite sludge washing system. The implementation of the removal of phosphorus from alkaline aluminate solutions of the hydrochemical cycle of obtaining alumina from alunite leads to the establishment of new, lower than in the known method, concentrations of oxide

0 phosphorus in solutions at all stages of the technological process. In this case, a solution with a concentration of P20b of less than 4 g / l is supplied to the decomposition of the aluminate solution, which is below the limit of its saturation with phosphate

5 sodium. The exclusion of saturation of solutions with sodium phosphate ensures guaranteed production of high-quality alumina with a phosphorus oxide (U) content of less than 0, 002% wt.%.

0 As a result of caustification of sodium phosphate by reactions (2), (4), 3 mol N320 per 1 mol of phosphorus oxide is formed, contained in the final phosphorus-containing precipitate, sent together with

5 waste alunite sludge to the sludge field.

With a degree of extraction of phosphorus into the solution from alunite, 41.2% can be regenerated, according to the invention, 6.2 kg

0 No. 20k per 1 ton of A120zprod or about 1800 tons of NaOH per year with minimal aluminum losses of about 0.07 kg A120z per ton of production alumina, and the cost of about 1800 tons of CaO per year at an annual capacity of

5 alumina 220 thousand tons At wholesale prices for lime and caustic soda, respectively 34.5 and 345 rubles. per 1 ton, the annual economic effect of reducing losses of caustic alkalis will amount to 559 thousand rubles. Additional economic effect will be obtained due to

to remove fines for the increased phosphorus content in alumina, which amounted to about 210 thousand rubles in only 4 months of 1991, according to reports from the Gdzhinsky Alumina Refinery, or about 600 thousand rubles. in year. The total annual economic effect will be about 1.1 million rubles.

The choice of the claimed parameters of the process of treatment with lime promoters of aluminum hydroxide obtained after decomposition of the aluminate solution, namely, the concentration of NazOic B is 35 g / l and the amount of lime introduced is 4.2 - 17.7 g / l CaO, due to that at a concentration of more than 35 g / l according to No. NaOK, the degree of phosphorus precipitation sharply decreases, the amount of regenerated caustic alkali decreases accordingly, and the loss of aluminum with a phosphorus-containing precipitate increases, and production alumina with a high content of phosphorus oxide is obtained; the lower limit of the concentration of Me20k - 5 g / l is due to the lower limit of the concentration of aluminum hydroxide promotes formed in the production cycle of aluminite hydrochemical processing. At a dosage of lime of more than 17.7 g / l, losses of aluminum with a phosphorus-containing precipitate sharply increase, while the degree of phosphorus precipitation increases slightly; at a dosage of lime of less than 4.2 g / l by CaO, the degree of phosphorus precipitation decreases, as does the amount of phosphorus removed from solutions of the hydrochemical cycle for producing alumina, and the amount of regenerated caustic alkalis is reduced, and the obtained alumina is contaminated with phosphorus oxide in excess of permissible norms.

The choice of the claimed parameters of the process of mixing the phosphorus-containing sludge in the rinsing system of alunite sludge with pulp having a concentration of the liquid phase of 10-30 g / L according to No. NaOK is due to the fact that at a concentration of less than 10 g / L noNaaOx phosphorus does not precipitate from the solution, but the amount of aluminum present in the precipitate does not decrease, and as a result, the loss of alumina increases, the amount of regenerated caustic alkali decreases, and alumina contaminated with phosphorus oxide is formed; at a concentration of more than 30 g / l NaaOx, there is practically no interaction of calcium hydroaluminate, which is present in the phosphorus-containing precipitate, with sodium phosphate, but an additional amount of calcium hydroaluminate is formed, as a result of which aluminum losses with the phosphorus-containing precipitate sharply increase, the amount of regenerated caustic alkali decreases and the formation of alumina contaminated with phosphorus oxide is above acceptable levels.

5 At a concentration of 5-35 g / l of aluminum hydroxide in NaaO, the amount of lime introduced into the treatment of 4.2 - 17.7 g / L in CaO, and also when the obtained phosphorus-containing precipitate is sent to the alunite sludge washing system for mixing with pulp having a concentration of a liquid phase of 10-30 g / by Na20K, practically all phosphorus is removed from the hydrochemical cycle of alumina production.

5 entering the aluminosilicate solution during the leaching of alunite. In this case, a lower level of concentration of phosphorus oxide in production solutions is established, far from

0 level of sodium phosphate saturation, and the resulting alumina contains less than 0.002 wt.% PaOs; at the same time, caustification of sodium phosphate is performed to obtain caustic alkali in an amount of about

5 5.2 - 6.2 kg of MaaOk per 1 ton of production alumina.

The economic effect of reducing losses of caustic alkalis and decreasing the content of phosphorus oxide in alumina around

0 1.1 million rubles per year with an annual alumina capacity of 220 thousand tons. An additional economic effect is the reduction in the cost of cleaning technological equipment.

The claimed technical solution differs from the prototype in that it removes the total amount of phosphorus entering the aluminate solution during the leaching of alunite from the hydrochemical cycle of processing alunite in two stages: first, by treating the aluminum hydroxide with lime at a certain concentration of the dosage of lime, moreover, simultaneously with phosphorus at this stage, a certain amount of aluminum in the form of calcium hydroaluminate passes into the precipitate5, and then - by processing phosphorsoder of burning sediment obtained in the first stage by the discharge of dump alunite

0 sludge in the system for washing it at a certain concentration of the liquid phase of the pulp, during this treatment, aluminum from the precipitate passes into the solution, and phosphorus from the solution into the sludge. By precipitating phosphorus with calcium hydroxide and hydroaluminate, causticization of sodium phosphate is carried out, which results in the recovery of about 90% of caustic alkali spent on leaching of phosphorus from alunite.

By removing phosphorus from the hydrochemical alunite processing cycle, the concentration of phosphorus in all solutions is lowered below the solubility level of sodium phosphate. An alumina not contaminated with phosphorus oxide is obtained, and sodium phosphate is clogged with technological equipment.

In the prototype method, caustic alkali spent leaching phosphorus from alunite is irretrievably lost. The concentration of phosphorus in technological aluminate solutions is at the limit of solubility of sodium phosphate under decomposition and evaporation processes, and the alumina obtained is contaminated with sodium phosphate (phosphorus oxide) due to crystallization of sodium phosphate together with aluminum hydroxide during the decomposition of the aluminate solution.

EXAMPLES In a steady-state equilibrium process, to produce 1000 kg of Production alumina, 7483.7 kg of crude alunite were processed with a content of 18.2% 1.4% NaaO; 3.5% CaO; 19% 50h; 44% S “02; 6.5% NaOb s; 0.4% H20external; 0.169% PaOs: 6.83%, etc.

Crude alunite was subjected to dry grinding, calcining at a temperature of 500-520 ° C to dehydrate the alunite ore, followed by reduction at 550-560 ° C with elemental sulfur, to obtain 6159.8 kg of reduced alunite with a content of 22.1% 10% 5Oz; 53.5% SI02; 1.7% Na20; 4.2% KrO; 0.206% P205; 8.29% Then, alunite was treated at a temperature of 50 - 55 ° C for 2 hours with 23.7 m3 of a working alkaline solution with a concentration of 124.5 g / l at 3.52 g / l of P20b; caustic module - 3.99. The reverse solution was prepared by mixing 21.33 m of the mother liquor after decomposition with a concentration of 3.83 g / l of P20s and 2.37 m3 of the solution after the conversion of sulfate salts of potassium hydroxide with a concentration of 0.71 g / l of P20s obtained in the previous alunite processing cycle.

In the leaching process, the phosphorus contained in & reduced alunite in videphosphosiderite (RePCm), interacts with caustic alkalis by reaction (1). The degree of phosphorus recovery in the aluminate solution was 41.2%. and the loss of caustic alkali for the extraction of phosphorus is 6.9 kg Na20ic kg per 1 ton of production alumina.

After leaching, the pulp was separated by a hydroseparator into silty and sand fractions. The sand fraction was filtered on a bulk filter and washed with water on a filter. The mud fraction was sent to thickening. The resulting aluminate solution was deoxidized at a temperature of 100 - 105 ° C for 6 hours in the presence of a white slurry seed. Received 20.2 m siliceous aluminate solution containing 100 g / l No. 20k; 83.5 g / l A120z;

0 69.1 g / l 50c; 3.46 g / l P205.

The thickened alunite sludge was supplied from the six-time countercurrent washing system to the washers, where the thickened sludge enters the first stage, and

5th sixth is flushing water. At each stage of the six-time countercurrent washing, the pulp contains about 9.8 m of the liquid phase with a concentration of about 55 g / L according to Na2OK in the first stage and about 1.6 g / L of Ma20k 0 at the last stage with an intermediate Na20x concentration of 55 to 1.6 g / l in the remaining stages of sludge washing. The liquid phases of the pulps of the alunite sludge washing system contain, as well as the aluminate solution.

5 sodium phosphate, as they are an aluminate solution diluted to varying degrees, initially present in the liquid phase of the thickened alunite sludge.

0 In the third stage of washing with a concentration of the liquid phase of 15 g / l Na20io 12.3 g / l A120z; 0.51 g / L P20s (volume 9.8 m3) fed a pulp of a phosphorus-containing precipitate obtained by treating with lime a promo 5 of aluminum hydroxide in the previous cycle. The amount of liquid phase of the added pulp is 1 m3, its concentration: 27.4 g / l Na20K: 9.5 g / l 0.14 g / l P2Os. The amount of solid phase added pulp

0 14.02 kg, content of mass fractions: 53.7% CaO: 17.6% P20s 5% 14.4% pp (1000 ° C); 5.7% Together with aluminite sludge, a phosphorus-containing precipitate was treated with weak aluminate

5 with a solution containing phosphate for 6 hours at this stage of washing at a temperature of 55 ° C. The concentration of the liquid phase of the pulp of alunite sludge after interaction with phosphorus-containing sediment:

0 16.3 g / l Na20K: 12.1 g / l 0.26 g / l P20s (volume 10.8 m. Next, the phosphorus-containing precipitate, together with alunite sludge, entered the remaining washing stages (fourth to sixth). received

5 4450.3 kg of solid phase of dump sludge, including 4435.8 kg of dump alunite sludge with a content of 7.8% A120z; 1.8% Na20; 0.8% KiO; 0.29% 50h; 74.4% SI02; 3.1% Н2ОСВЯЭ; 0.168% P20s; 11.64%, and also 14.5 kg of the final phosphorus-containing precipitate with a content of 55.4% CaO; 33.8% PzOs; 0.5% 5.7% pp; 5.6% (others include silicon dioxide, alkali metal oxides, etc.). Loss of alumina with phosphorus-containing sludge amounted to 0.08 kg per 1 ton of A1gRzprod. The sludge was sent to the sludge field in the form of a pulp containing 5.52 m3 of the liquid phase with a concentration of 1.6 g / l NaaOtc, 0.04 g / l PzOs. After washing, we received 10.8 m of waste alunite sludge with a concentration of 58 g / l MaaOk, 1 1.52 g / l.

In the alunite sludge washing system, calcium hydroaluminate, contained in the circulating phosphorus-containing precipitate, reacts with sodium phosphate present in the pulp liquid phase according to reaction (4) with the formation of sodium phosphate and the regeneration of aluminum / present in the precipitate, as well as with the formation of caustic alkalis. In addition, the destruction of dense calcium hydroaluminate films results in the interaction of excess calcium hydroxide located in the center of the phosphorus-containing precipitate particles with sodium phosphate according to reaction (2). The amount of caustic alkali formed in the alunite sludge washing system by reactions (2), (4) was 3 kg Na20K. The amount of phosphorus extracted from the solution is 45.3% of the total amount of phosphorus contained in the final phosphorus-containing sludge sent to the sludge field together with alunite sludge.

The aluminate solution was evaporated to a concentration of 150 g / L by Na2OK, obtaining 13.07 m3 of an evaporated solution with a concentration of 5.2 g / L P205 and 1340 kg, by dry, of potassium sulfate salts, sodium with a moisture content of about 20 wt.% (Sulfate salts separated from one stripped off solution by thickening, followed by filtration on a drum vacuum filter). Sodium phosphate does not crystallize with sulfates during evaporation and separation of sulfate salts, since the concentration of sodium phosphate is lower than its solubility in the evaporated solution at the separation temperature of sulfate salts (75 ° C). The content of PaOs in sulfate salts is x 0.14 wt.%.

Potassium and sodium sulfate salts were sent to a two-stage countercurrent conversion with a solution of caustic potassium at a temperature of 50 ° C. 1275.1 g of potassium sulfate were obtained with a content of 0.01% 2Ob and 2.37 m3 of a solution after conversion with a concentration of 147.5 g / l Ma20k; 0.71 g / l PaOs, which was used in the alunite leaching step,

The evaporated solution was diluted with washing of dump alunite sludge to obtain 23.9 m3 of a solution with a concentration of 108.2 g / l NaaOK; 3.53 g / l P20s, which was sent for decomposition. The decomposition was carried out for 70 h with a gradual cooling of the solution to a temperature of 40 - 45 ° C. During decomposition, sodium phosphate does not crystallize together with aluminum hydroxide, i.e. the concentration of sodium phosphate in the solution is below the solubility level at the temperature of the decomposition process. The precipitated aluminum hydroxide was separated by thickening with filtration of the thickened pulp on a drum filter. The precipitate was washed on a filter with 1 m3 of water. Received 1525.7 kg of production aluminum hydroxide, after calcination of which formed 1000 kg of production alumina with a content of A1aOz - 99%; PiOs - 0.0015 wt.%. Product alumina is not contaminated with phosphorus oxide above acceptable levels.

After separation of the aluminum hydroxide, a 21.33 m stock solution was obtained with a concentration of about 122 g / L according to Ma20k: 3.83 g / L P20s, which was sent to leach alunite.

After washing with aluminum hydroxide, about 1 m of aluminum hydroxide was formed with a concentration of 24.2 g / l Na20K; 10.2 g / l 2.6 g / l P20s (caustic module - 3.9).

The aluminum hydroxide promoter was treated with lime at a temperature of 80 ° C for 2 hours. The amount of lime added was 8.04 g, calculated as CaO, which corresponds to a dosage of 3.09 kg CaO per 1 kg of P20s in the promv. After treatment, the liquid phase of the pulp has a concentration of 27.4 g / l 9.5 g / l AO3; 0.14 g / l P20s (caustic module 4.74). The content of mass fractions in the solid phase of the pulp: 53.7% CaO; 17.6% P20s; 5% 14.4% pp; 5.7%, other .. the amount of solid phase is 14.02 kg. During the treatment with lime, the promoters of aluminum hydroxide precipitate phosphorus and aluminum by reactions (2), (3). The degree of phosphorus precipitation is 94.6% of the content of aluminum hydroxide in the initial promoter or 54.7% of the total amount of phosphorus removed to the sludge field as part of the dump alunite sludge in the form of a final phosphorus-containing precipitate. The amount of precipitated aluminum 0.7 kg ABO3. At the same time, caustification of sodium phosphate occurs, as a result of which 3.2 kg of caustic alkali are formed in

ME20k.

The pulp obtained after treatment with lime of an aluminum hydroxide feed containing phosphorus sludge was sent to the alunite sludge washing system of the subsequent alunite processing cycle for mixing with pulp containing 15 g / l Na20K in the liquid phase.

Thus, by treatment with lime, the hydroxides of aluminum hydroxide, followed by the transfer of the obtained phosphorus-containing precipitate to the alunite sludge washing system, were isolated into the solid phase and more than 90% of the phosphorus in the waste alunite sludge from the quantity entering the aluminate solution during the alunite leaching was removed. The steady-state concentrations of phosphorus oxide in technological solutions of all stages of hydrochemical processing of alunite are below the solubility level of sodium phosphate. Due to this, sodium phosphate does not crystallize either during decomposition or at the stage of evaporation and thickening of sulfate salts, which takes place in the prototype method. The resulting alumina is not contaminated with phosphorus oxide above its permissible levels. Caustic alkalis are formed in an amount of about 6.2 kg per 1 ton A Ozprod. for MaaOK or about 1800 tons per year for NaOH with an annual alumina capacity of 220 thousand tons which are irrevocably lost in the prototype method.

Table 2, for further clarification, shows the balance of phosphorus distribution in the above example of processing alunite per 1 ton of production alumina.

Alunite was further processed in a manner analogous to the example described above. In contrast to the above example, an alumina hydroxide promoter contains varying amounts of phosphorus oxide (5-1.5 g / L P20s). The promoter was treated with lime introduced in various amounts from 18.5 to 3 g / L CaO under the same conditions. The results are presented in Tables 3, 4. When the amount of lime added is more than 17.7 g / l, the loss of alumina with the final phosphorus-containing precipitate increases by a factor of 5, and when the amount of lime is less than 4.2 g / l by CaO, the degree of phosphorus precipitation from the wastes sharply decreases aluminum hydroxide, and the resulting alumina is contaminated with phosphorus oxide above acceptable standards. When the amount of lime is 17.7 - 4.2 g / l CaO, alumina is obtained with a phosphorus oxide content of less than 0.002 wt.%. the loss of alumina with a final phosphorus-containing sludge removed to the sludge field is a negligible amount of 0.06-0.10 kg per 1 ton of A120prod., and at the stage of lime treatment, 2–6 kg of NaaO per 1 ton are regenerated

A120zprod.

5 In addition, alunite was processed similarly to the example described above, in contrast to which the promotion of aluminum hydroxide at the same concentration of phosphorus oxide contains different

0 the amount of Na2UK is from 5 to 45 g / l (OK 3.9), The dosage of lime for the treatment of aluminum hydroxide promotes was also .8.04 g / l for CaO. The results presented in table 5 indicate that

5, at a concentration of more than 35 g / l Na20 "the equilibrium of reaction (1) begins to shift to the left, in this case the reaction of formation of calcium hydroaluminate is activated and aluminum losses sharply increase with a finite phosphorus-containing precipitate. The degree of phosphorus precipitation decreases sharply, and the resulting alumina is contaminated with phosphorus oxide. At a concentration of 5 to 35 g / l, the degree of phosphorus precipitation is 5 to 82 to 96% of the content of aluminum hydroxide in the promoter, and the loss of aluminum with the final phosphorus-containing precipitate is minimal.

At a concentration of promvu 5-35 g / l

0 to No. 20k, the resulting alumina is not contaminated with phosphorus oxide.

As an additional example, the promotion of aluminum hydroxide with a concentration of 45 g / l Na20K; 2.6 g / l P20b (volume 5 1 m) was diluted with water to a concentration of 35 g / l according to No. 20k. 6.2 g / l of CaO was introduced into the diluted dressing and then the technological process was carried out, similarly to the above-described example of alunite processing.

0 The degree of precipitation of phosphorus from the industrial line was 82.5%, the loss of alumina with a final phosphorus-containing precipitate was 0.08 kg per 1 ton of A120z, the mass fraction of phosphorus oxide in the production alumina was less than 0.002%,

5 the amount of regenerated caustic alkali - 6.2 kg Na20 per 1 ton of production alumina.

Similarly to the example described above, alunite was processed with lime treatment to produce aluminum hydroxide with an initial concentration of 24.2 g / l Na20K: 10.2 g / l A120z: 2.6 g / l P20s under the same conditions, respectively, obtaining a pulp containing 1 m of a liquid phase with a concentration of 27.4 g / l Na20K; 9.5 g / l A120z; 0.14 g / l P20s and 14.02 kg of the solid phase of a phosphorus-containing precipitate with a content of 53.7% CaO; 17.6% P205; 5.0% 14.4% pp; 5.7% off The obtained phosphorus-containing precipitate was sent as pulp to the system

washing alunite sludge to mix with pulp, which, in contrast to the above example, has a different concentration of the liquid phase from 5 to 35 g / l according to NazO. The results, presented in Tables 6, 7, indicate that a concentration of less than 10 g / l by MaaO-Phosphorus does not transfer from solution to precipitate, while the achieved degree of phosphorus precipitation is insufficient to produce high-quality alumina. The resulting alumina is contaminated with phosphorus oxide to a content of 0.004 May. %, and the amount of regenerated caustic alkali is sharply reduced. At a concentration of more than 30 g / l according to No. AOK, phosphorus also does not precipitate from the solution, but an additional enrichment of the phosphorus-containing precipitate occurs with aluminum, as a result of which the loss of aluminum with the final phosphorus-containing precipitate increases to 1.3 kg per 1 ton of production alumina. The resulting alumina is contaminated with phosphorus oxide, and the amount of regenerated caustic alkali is also sharply reduced. At a concentration of 10 .- 30 g / l, NazOie produces production alumina with a phosphorus oxide content of less than 0.002 wt.%, The loss of aluminum with a phosphorus-containing precipitate is minimal, and the amount of regenerated caustic alkali is 5.2 - 6.2 kg LAGOK per 1 ton of production alumina.

Thus, the claimed technical solution allows to reduce the content of phosphorus oxide in production alumina by removing phosphorus entering the aluminate solution during the leaching of alunite from hydrochemical

alumina production cycle, as well as to reduce the cost of caustic alkali due to the regeneration of caustic alkali spent on the extraction of phosphorus from alunite to aluminate solution, the amount of which is significant, due to the specific properties of alunite raw materials.

Claims (1)

SUMMARY OF THE INVENTION A method for the hydrochemical processing of alunite, including treating raw or reduced alunite with a reverse alkaline solution, separating and washing alunite sludge, deoxidizing an aluminate solution and controlling filtration, followed by evaporation and separation of sulfate salts, separating them from one stripped off solution, diluting the latter with waste alunite sludge and decomposition of aluminate solution to obtain aluminum hydroxide, promoters of aluminum hydroxide and mother liquor, is used as a working alkaline solution in the processing of alunite, calcination of aluminum hydroxide to produce production alumina, characterized in that, in order to reduce the consumption of caustic alkalis and to reduce the content of phosphorus oxide impurities in production alumina, an aluminum hydroxide passage with a concentration of 5-35 g / l MaaOk is treated with lime in an amount of 4.2 -17.7 g / l CaO to obtain a phosphorus-containing precipitate and feed it to wash alunite sludge by mixing with pulp having a liquid phase concentration of 10-30 g / l NaaO. Table 1 The dependence of the content of phosphorus oxide in alumina on the concentration of PaOs in solution, coming to decomposition table 2 The balance of the distribution of PaOs in the process of hydrochemical processing of alunite by the proposed method per 1 ton of A120zprod, Table 3 The effect of the amount of lime introduced on the processing of aluminum hydroxide promoters on the performance of alunite hydrochemical processing Table 5 Influence of NaAOK concentration in an aluminum hydroxide promoter upon treatment with lime on indicators of hydrochemical processing of alunite Table 6 The effect of Na concentration in the liquid phase of the pulp of the alunite sludge washing system when mixed with a phosphorus-containing precipitate at the hydrochemical processing indicator  aluiita T table 7 The chemical composition of precipitation and concentration of solutions to examples 8-12 (table.6}