SU1054298A1 - Method for producing phosphoric acid - Google Patents

Abstract

1. A method for producing phosphoric acid, which includes mixing circulating phosphoric acid, circulating pulp and sulfuric acid, decomposing the phosphate raw material with the mixture at 95-115 ° C, pas-i dividing the pulp into two streams, one of which is sent to recirculation and the other - Ne separation of the product from calcium sulfate hemihydrate, characterized in THAT; in order to increase the degree of extraction into the product and reduce the loss of fluorine with calcium sulfate hemihydrate, 60-85% of the total sulfuric acid is fed to the mixing stage while maintaining its concentration in the O mixture, 5-1, the remaining amount is fed directly to the decomposition stage. 2. The method according to claim 1, in which the concentration of calcium oxide in the liquid phase at the decomposition stage is g = 0.6-1.5%. 3. The method according to claims 1 and 2, p tl and (Concerning that the mixture is kept at 95-105 C for 2-5 minutes with stirring. 4. The method according to PPL-3, characterized in that the phosphate surium and the mixture is fed to decomposition countercurrent.

Description

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This invention relates to a technique for the production of phosphoric acid by sulfuric acid decomposition of a phosphate raw material.

A known method for producing phosphoric acid, which includes decomposition of phosphate raw materials at b5-95 ° C with circulating phosphoric acid and a mixture of circulating pulp and sulfuric acid containing 2-10% H2SO4, separating parts of the pulp for recycling And filtering the rest of the part with separation of the Acid. From the hemihydrate Calcium Sulphate JTI ..

The disadvantage of this method is the isolation of an unstable hemihydrate and, accordingly, gypsum filtering after 7-10 days of operation of the filter.

 A method for producing phosphoric acid is excluded, including the decomposition of phosphate raw material at 104-115C with a mixture of circulating phosphoric acid, circulating pulp and sulfuric acid containing 5-15% HjSO, separating a part of the pulp for recycling and filtering the rest of the acid with separating the acid from calcium sulfate 2T calcium hydrate .

The disadvantages of the known method are a decrease in the degree of extraction into the solution with an increase in the concentration of phosphoric acid from 32 to 42%, as well as an increase in the loss of fluorine due to an increase in its content in the waste sediment of the calcium sulfate hemihydrate.

The aim of the invention is the by-product and reduction of fluorine losses with calcium sulfate hemihydrate.

The goal is achieved by the fact that according to the method of obtaining phosphoric acid, which includes mixing of circulating phosphoric acid, circulating pulp and sulfuric acid, decomposition of the phosphate raw material at 95-115 With the mixture, feeding part of the pulp for recycling, and the rest for acid separation. from calcium sulphate hemihydrate, 60-85% of total acid from the total amount is fed at the ne stage of mixing while maintaining its concentration in the mixture of 0.5-1.8%, and the remaining amount is fed directly to the decomposition stage.

It is advisable at the decomposition stage to maintain the concentration of calcium oxide in the liquid phase equal to 0.6-1.5%, to maintain the mixture while stirring for 2-5 min at 95195 ° C, and to transfer the phosphate raw material and the mixture to countercurrent decomposition.

The upper and lower limits of the amount of sulfuric acid added to the mixture and its concentration are due to the achievement of a significant increase in the degree of extraction in the solution by 0.6–1 abs.%) While simultaneously reducing the fluorine content in calcium sulfate hemihydrate by 15–40 rel.%.

Table 1 shows the effect of the proportion of sulfuric acid supplied to the mixture on the process performance.

CaO content in the liquid phase of the circulating suspension 0.6% 3.1 Content. 96.8. The content of fluorine 0.5 in the solid phase The content of CaO in the liquid phase The content of 2.6 96.3 K ", V.P205 The content of fluorine 0.48 in the solid phase

0.4

96,8

0.28

O., 35 96.5

0.32 2.3 1.9 1.8 0.8 0.6 0.5 96.7 96.8 97.4 97.8 97.6 97.4 0.5 0.48 0.42 0, 3 0.3 0.28 circulating suspension 1.5% 2.0 1.8 1.5 0.6 0.6 0.5 0.5 0.4 96.5 97.2 97.2 97.7 97.3 96.6 0 , 46 0.38 0.35 0.32 0.34 0.32

An additional difference is the concentration of calcium oxide in the liquid phase of the pulp during the decomposition stage, which is maintained at b, 6-lf5%. The lower limit of CaO content is determined by reducing the degree of extraction into the solution to a level close to the prototype (96.3%) due to the sludging of phosphate raw material grains with fine calcium sulphate, the upper one by slowing down the decomposition rate and the need to increase the duration of pulp exposure in the reaction zone for more than 2 hours. The supply of phosphate raw material and the mixture to countercurrent decomposition almost completely eliminates local supersaturation and allows for a more complete recovery of the product. P. 1. Example 1. In the first section of the reactor (the mixing zone serves 230 parts by weight of reverse phosphoric acid (31.9%, 0.8% of Ng304, 3000 parts by weight of circular pulp) (W: T 2 : 1) and 60 parts by weight of sulfuric acid at a concentration of 92% (60% of its total consumption). Blending is carried out for 5 minutes at 102 s. A mixture containing 0.5% of H "SO is introduced into the second section of the reactor ( decomposition zone) where 100 parts by weight of apatite concentrate (39.4%, 52% CaO) and 32 weight of sulfuric acid are fed, maintaining the content of CaO in the liquid phase of the suspension 1.5%. 3000 parts by weight of the reaction mass from the second section is used as qi pulping, and the remaining pulp is transferred to the third section of the reactor (decomposition zone), where 8 parts by weight of sulfuric acid is added. Preferably, the mixture is kept at 95-105 seconds for 2-5 minutes with stirring. The lower limits of temperature and time are determined by the need to ensure uniform mixing and removal of calcium sulfate supersaturation, as well as the efficiency of decomposition, the upper — some (by 0.05%) increase in the fluorine content — in the solid phase,

Table 2 shows the effect of the mixing temperature on the process performance.

Tables 2 you. Decomposition temperature 102 ° C, time 30-90 minutes. The degree of extraction of P2O5 to the solution was 98%. The suspension is filtered, the precipitate. Calcium sulfate calcium sulfate hemihydrate is subjected to countercurrent npoNWBKe and 95 parts by weight are obtained. production phosphoric acid (40%), 165 weight.h. wet calcium sulfate half-arydrate, containing 0.28% fluorine, and 230 parts by weight circulating phosphoric acid. When carrying out the process according to the prototype, the degree of extraction into solution is 96.0%, and the wet sediment contains 0.42% fluorine. Example 2. In the first section of the reactor serves 230 weight.h. circulating phosphoric acid (31.9%, 0.8%), 3000 parts by weight circulating bullets, dust (L: T "2: 1) and 85 weight.h sulfuric | acid concentration 92% 85% of its total consumption). Mixing is carried out for 2 minutes at 95 ° C. A mixture containing 1.8% H-jSQf is introduced into the second section of the reactor, to which 100 weight.h of apatite concentrate (39.4 PjOy, 52% CaO) and 12.5 weight are fed. .h

sulfuric acid, the CaO content in the liquid phase of the suspension is 0.6%, 3000 parts by weight. The reaction mass from the second section is used as a circulating pulp, and the remaining pulp is transferred to the third section of the reactor, where 2.5 parts by weight are introduced. acid acid. Decomposition temperature, time 30-90 min. The degree of recovery to the solution is 97.8%. The suspension is filtered, the precipitate of calcium sulfate hemihydrate is subjected to an Anti-Rinse and 94.8 parts by weight are obtained. production phosphoric acid (40% Pr, 0, 170 parts by weight of wet sludge calcium sulfate hemihydrate, containing 0.26% fluorine, and 230. of recycled phosphoric acid.

Froze In the first section of the reactor, served 230 weight.h. circulating phoophoric acid (31.9% 45304) 3000 parts by weight of circulating pulp (g: T 2: 1) and 80 parts by weight sulfuric acid concentration of 92% H, 2SOj (80% of its total consumption). Mixing is carried out for 4.5 min. A mixture containing 1, 4% is introduced into the second section of the reactor, where 100 parts by weight are fed. apatite concentrate. (39.4%, 52% CaO) and 16 weight.h. sulfuric acid, maintaining the CaO content in the liquid phase of the suspension of 0.8% 3000 parts by weight. The reaction mass from the second section is used as a circulating pulp, and the remaining pulp is transferred to the third section of the reactor, where 4 parts by weight are introduced. sulfuric acid. Decomposition temperature, time 30-90 min. The degree of extraction of PjOf to the solution is 98.3%. The suspension is filtered, the precipitate of calcium sulfate hemihydrate is subjected to countercurrent washing and 96 parts by weight are obtained. production phosphoric acid (40%), 165 weight.h. wet precipitate hemihydrate calcium sulphate containing 0.25% fluorine, and 230 weight.h, circulating phosphoric acid (31.9% .P, 0,) .. Example 4. The process is carried out, similarly to example 3 with the only 5 difference that natural phosphates and the mixture are introduced into the decomposition zone in countercurrent. Remove to the solution of 98.5%, get 96.2 weight.h. production phosphoric acid

(40% PrtOg-) and 165 weight.h. wet wasp, calcium sulfate hemihydrate containing 0.25% fluorine.

EXAMPLE 5 The process is carried out as in Example 3 with the only difference that mixing is carried out at 97.degree. The fluorine content in the sediment is 0.23%.

Thus, the proposed method, compared with the known method, allows 0.6–1 abs.% To increase the yield of PjjOj in solution and 20–45 relative% to reduce the fluorine content in the calcium sulfate hemihydrate precipitate and, accordingly, reduce the loss of this valuable component.

Claims (4)

1. METHOD FOR PRODUCING PHOSPHORIC ACID, including mixing phosphoric acid, circulating pulp and sulfuric acid, decomposing the phosphate feed with the mixture at 95-115 ° С, splitting ⁴ pulp into two streams, one of which is sent for recycling, and the other Ne separation of the product from calcium sulfate hemihydrate, characterized in that, in order to increase the degree of extraction of P ^ Oj 'in the product and reduce fluorine losses with calcium sulfate hemihydrate, 60-85% of the sulfuric acid of the total amount is fed to the mixing stage while maintaining Its concentration in the mixture is 0.5-1.8% ^ and the remaining amount is fed directly to the decomposition stage. 2. The method of pop. 1, characterized in that, at the stage of decomposition, the concentration of calcium oxide in the liquid phase is maintained equal to 0.6-1.5%. § 3. The method according to claims 1 and 2, characterized in that the mixture is kept at 95-105 ° C for 2-5 minutes with stirring. 4. The method according to ppL-3, with the exception of the fact that the phosphate sire and the mixture are fed to the decomposition “countercurrently. 10542 OE> 1 1054298