SU1399266A1 - Method of producing phosphoric acid - Google Patents

Abstract

The invention can be used for the production of phosphoric acid from phosphorites. The purpose of the invention is to intensify the process by reducing the duration of recrystallization of the hemihydrate into gypsum. 06opoTHjTo phosphoric acid is mixed with sulfuric acid, the phosphate raw material is decomposed with this mixture at a temperature of 80-100 ° C, the calcium sulfate hemihydrate formed is recrystallized into a dihydrate at 70-75 ° C and the ratio of G: T (1.8-3): I, is separated the precipitate is filtered, washed and the washings are returned to mixing with the raw material. In this case, circulating phosphoric acid is mixed with sulfuric in a P20i: H20 mass ratio equal to (0.08-0.13) l, calculated to 100%, decomposition of the phosphate raw material is carried out for 5-15 min at W: T (0 6-1.1): 1, the remaining circulating phosphoric acid is added to the recrystallization stage until the required G: T is reached. 4 tab. i (L

Description

one

The invention relates to a method for the extraction of phosphorite extraction foss {yuric acid used in the manufacture of mineral fertilizers and other phosphate salts.

The purpose of the invention is to intensify the process by reducing the duration of recrystallization of the hemihydrate to dihydrate while maintaining a high yield of P-, 0 when processing low-quality raw materials.

Example I. 270 hours of circulating phosphoric acid concentration of 22.1% Pj O is mixed with 770 parts of 93% sulfuric acid (ratio) L: –0.08: 1, the ratio of flows - 0.35: 1) ; in this case 10 parts of water vapor are removed into the gas phase and 1030 parts of the mixture are formed. The mixture is sent to the reactor, where 1000 hours of Karatau phosphorite containing,%, are simultaneously served: P 24.1; CaO 39; MgO 3.7; A1.0s 0.8. The treatment of phosphate was solubilized at 90 ° C for 15 minutes. G: T in pulp 0.6: 1, At the semi-hydrate stage, 70 parts of water vapor, carbon dioxide and fluoride compounds are added to the gas phase. 1960 h. Hemihydrate pulp is sent to the hydration stage, where

cooled to 40 ° C (310 parts of water vapor are removed to the gas phase) and the rest is added (4070 hours of circulating phosphoric acid of 22.1% Pr concentration OJ -l to maintain the target. Full hydration of calcium sulfate hemihydrate is completed in 7 -7.5 h, which is 2.3 times faster than the prototype.

5720 parts of the suspension of calcium sulfate dihydrate in phosphoric acid with a concentration of 28% Pr, Oy is separated on a vacuum filter (the conventional filtration capacity is 3.3 tons / hour). The precipitate is washed with 1350 parts of water and 820 parts of production phosphoric acid of concentration of 28% P2 0, p are obtained. 4340 h. Of 22.1% phosphoric acid circulating, which was returned

1910 hours of waste phosphogypsum (moisture 25%) are deposited in the extraction process. Kwa. 95.3%.

In the prototype, high-quality phosphorite (33–34% P) is decomposed with a mixture of acids (P.jO., - / H2SO (1, 25–20) g 1 at 8–100 s for 60–90 min with a weight ratio W: T, equal to (1.8-3): 1 with the formation of hemihydrate sul5

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calcium carbonate, which is hydrated to form calcium sulfate dihydrate at 70-75 0 for 12-36 h. The condensate is separated from the product by filtration.

When processing low grade Karatau phosphorite containing high yield magnesium, it can be achieved at a shorter recrystallization stage or with an intermediate separation of calcium sulfate hemihydrate. However, filtration of the hemihydrate pulp is accompanied by equipment inlay and plastering of filter cloth.

Table 1 shows the effect of the ratio of H280) when mixing acids on process performance.

When the ratio is less than 0.08: 1, the filtration capacity and the yield of P2.0 decrease, with a ratio of more than 0.23 :), the recrystallization time increases and the output decreases by 7 0.

In the invention, reducing the proportion of circulating phosphoric acid supplied to the mixture with sulfuric, allows to obtain an easily hydrating hemihydrate. This phenomenon is due to a decrease of

fraction of fluorine bound to fluorocomplex AlF ions. , as well as the amount of anhydrite released during acid mixing.

And p m ime p 2. The process is carried out as described in example 1, but 1 part of oleic acid (0.1 parts per 100 parts of phosphate) is fed to the stage of mixing of circulating phosphoric and sulfuric acids. After separation of the suspension of calcium sulfate dihydrate in phosphoric acid on a vacuum filter and washing the precipitate with 1300 parts of water, 820 parts of production phosphoric acid are obtained with a concentration of 28% 4340 parts of 22.1% phosphoric acid and 1860 hours waste phosphogypsum (moisture - 23%), the conditional filtration rate is 3.9, which is 1.25 times higher than with estvlenii process without the addition of oleic acid.

Table 2 presents data on the effect of the ratio of G: T at the hemihydrate stage on process indicators.

From the data of Table 2 it follows that a decrease in the ratio below 0.6: 1 leads to a decrease in the mobility of the pulp and, as a consequence, to a decrease in production of 1399266

filtration and release of phosphoric and sulfuric acids, processing

due to a lower ratio.

Increasing the ratio of more than 1.1: 1 does not provide the required temperature for Mr. (not lower than 80 ° C) of the hemihydrate stage.

Table 3 presents data on the effect of processing time on the hemihydrate stage.

the mixture of phosphate raw material at 80-1OO C to form calcium sulfate hemihydrate precipitate, its subsequent recrystallization to calcium sulfate dihydrate at 70-75 C

and the mass ratio W: T (1.8–3.0): 1, separation of the product from the precipitate. water to phosphoric acid for less than 5 minutes as a process phosphoric acid is accompanied by a significant decrease in acid, characterized by the degree of extraction. (by 2.4, for the purpose of intensification, about 4.5%). An increase in the duration of T5 due to the reduction in the duration of the indicated mixture of phosphate raw material at 80-1OO C to form calcium sulfate hemihydrate precipitate, its subsequent recrystallization into calcium sulfate dihydrate at 70-75 C

treatment of phosphate with a mixture of acids over I 5 minutes leads to a slower process of hydration.

Claims (1)

As can be seen from Table 4, an increase in the hydration temperature from 50 to 70-75 under the conditions of the proposed method leads to an increase in the duration of hydration from 6.5 to 8-10 hours, and during the implementation of the process according to the prototype, the duration of hydration at 70- 75 ° reaches 40 hours or more. Invention Formula A method of producing phosphoric acid, comprising mixing the reverse Effect of the ratio P Of / E2QO in a mixture of circulating phosphoric and sulfuric acids on the hydration of the hemihydrate at 50 ° C  The hemihydrate was precipitated at 90 by treatment for 10 minutes of a sample of phosphorite. Karatau, the composition of which is given in example 1, with a mixture of acids. The concentration in the liquid phase of the production pulp is 28%. recrystallization of the hemihydrate into calcium sulfate dihydrate while maintaining a high yield of P2 05 when processing low-quality raw materials, a part of the circulating phosphoric acid is mixed with sulfuric to a mass ratio, respectively (0.08-0.23): calculated on the 100% content, the raw material is treated with this mixture 5-15 min while maintaining the mass ratio W: T in the pulp (0.6-1.1): and the rest of the phosphoric acid is added to the recrystallization. Table 1 513992666 Table 2 The effect of G: T upon decomposition of the raw material on hydration hemihydrate (0.14: 1; 90) The effect of the duration of the treatment of phosphate raw materials with a mixture of sulfuric and part of the circulating phosphoric acid (iOf / H SO 0.14: 1, W: T 0.75: 1 at the hemihydrate stage)  1399266 Table4 Effect of Hydration Hydration on Hydration of Calcium Sulfate Hemihydrate (W: T at the Hemi-Hydrate Stage 0.75: 1) 15 16.5 25 6.5 7.5 40 Not hydrated for 2 days. 8 10 Not hydrated for 2 days.