SU1171419A1 - Method of producing phosphoric acid - Google Patents

Abstract

DREAMING FOR PHOSPHORIC ACID PRODUCTION, including processing phosphate feedstock with recycled phosphoric acid, separating the insoluble residue by filtration, treating the filtrate with sulfuric acid, crystallizing the calcium sulfate precipitate, followed by separating the calcium sulfate precipitate by filtration, washing it and returning the wash water to the treatment stage as turnover phosphoric acid, characterized in that, in order to reduce the content of impurities of iron and aluminum in the product and increase productivity filtration of the insoluble residue, phosphate sfye pre-mixed with silicon dioxide in a mass ratio of SiO and P205- in raw materials

Description

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CO 1 The invention relates to a method for producing phosphoric acid used for the production of mineral fertilizers, and can be used in the processing of poor phosphate raw materials. The aim of the invention is to reduce the content of iron and alumina impurities in the product and increase the filtration performance of the insoluble residue. Example 1. In the first reactor serves 800 kg of flotation concentrate containing 24% PjO, 37 ° C 18%, 200 kg of quartz sand (silica), the ratio of SiO and 1.8: 1 and 9535 kg, circulating phosphoric acid concentration 15-16 % PjOj-. The decomposition is carried out for 50 minutes with the formation of a solution of monocalcium phosphate in phosphoric acid. Next, the suspension is disassembled, a section of 400 kg of indecomposable residue along with quartz sand. containing 0.5% PjOj, which is stored in a dump, the filtration capacity is 1000, and the liquid phase in the amount of 9900 kg is sent to the second reactor, where 582 kg of 93% sulfuric acid is fed. The crystallization time of calcium sulfate dihydrate is 1-2 hours. The pulp goes to filtration where 8542 kg of extraction phosphoric acid is obtained, with a concentration of 17–18% P2.05 of which 7577 kg are returned to the first reactor together with 1518 kg of the second filtrate, and 965 kg output in the form of production acid. Phosphogypsum on the filter is washed with countercurrent three times with intermediate filtrates. At the last wash, 818 kg of hot water is supplied. Waste Phosphogypsum, in the amount of 1.240 kg, containing 22% hygroscopic moisture, is stored. The specific removal of phosphogypsum is 500 kg / m2 h. The yield in the product is 98%. Production acid contains 0.6% and 0.8% AljGj. 45% of impurities contained in the raw material are transferred to the solution. Example 2. In the first reactor, 1000 kg of washed phosphate concentrate of coarse grinding (75% of particles of more than 100 mesh in size) containing are fed. 18-19%, PjOy, 3%, 4% COi 19 28% SiOg, the ratio of SiO and, 55: 1 and 9535 kg of circulating phosphoric acid with a concentration of 15-16% PjOy. Decomposition is carried out for 40 minutes at. The resulting suspension is filtered, filtration capacity is 1400 kg / m "h ;; the solid phase — 400 kg of the uncomposed residue containing 0.5% is stored, and the liquid phase in the amount of 9900 kg is sent to the second reactor, where 582 kg of 93% sulfuric acid is fed. The crystallization time of calcium sulfate dihydrate is 1-2 hours. The pulp goes to filtration, where 854% of extraction phosphoric acid is obtained with a concentration of 17-18% of which 7577 kg is returned to the first reactor along with 1518 of the second filtrate, and 965 kg is output as production acid. Phosphogypsum is washed on the filters with a countercurrent three times with intermediate filtrates; 818 kg of hot water is fed to the last wash. Waste gypsum containing 99% 2H.20 in the amount of 1240 kg can be used as a filler in the manufacture of paper. The yield of P2: 05 in the product is 98%. Removal of phosphogypsum 650. Production acid contains 0.7% and 0.85%. 50% of impurities contained in the raw materials pass into the solution. Example Z. In the first reactor, 1000 kg of unrefined phosphate raw material of coarse grinding (75% of particles larger than 100 mesh) containing 18-19%, 3%, 24% SiOj, the ratio of SiO and PjjOj of 1.3: 1 and 9536 kg of circulating phosphoric acid concentration of 15-16% P2.0j-. Decomposition is carried out for 30 minutes at. Next, 400 kg of an uncomposed residue containing 0.5% is separated from the suspension by filtration, the filtration capacity 1500 and the liquid phase in the amount of 9900 kg are sent to the second reactor, where 582 kg of 93% acid are fed. The crystallization time of calcium sulfate is 1-2 hours. The pulp enters the filtration, where it receives 8542 kg of extraction phosphoric acid with a concentration of 17-18% of which 7577 kg is returned to the first reactor together with 1518 kg of the second filtrate, and 965 kg is output as production acid. Phospho-. filter gypsum is flushed countercurrently three times with intermediate filters. At last, the washing is supplied with 818 kg of hot water. Waste gypsum in the amount of 1240 kg, containing 99% CaSO -21120 can be used as a filler in the manufacture of paper. Specific schemes of phospho-gypsum 800. The yield of the product is 99%. Production acid contains 0.8% and 0.9%. 55% of impurities contained in the raw material are transferred to the solution.

Co-crystalline silicon dioxide with a particle size of 0.5-1.0 mm is used, which creates a spatial grid when filtering into which fine particles of non-phosphate minerals containing iron and aluminum fall. Under these conditions, the filter cloth is not clogged and these particles do not pass through it. Filtration performance increases. The ratio of the content in the product The mass ratio of the extraction of SiO and PjOy P, 0f,%

In tab. Figure 1 shows the effect of Si02 mass ratio and process indicators ().

From the data given in Table 1, it follows that in the absence of silicon dioxide additive (under the conditions of a known method), iron and alu minum impurities are almost completely dissolved in the product, and the filtration rate of insoluble sludge is low. With a weight ratio of SiO and more than 1.8, the filtration performance decreases due to an increase in the precipitate layer.

Table 2 gives the effect of the treatment temperature of cf recycle phosphoric acid (1.5).

From the data given in table. 2, it follows that at a temperature below 40 ° C, the filtration capacity is dependent on {the high viscosity of the suspension. At temperatures above the solubility of the compounds of iron and aluminum increases and their content in the product increases.

Table 1 Filtration performance of insoluble precipitate,

1.8

70 80 95 97 97 98 99 97 1.6.

1.1 0.7 0.6 0.6 0.6

25

300

1100

1500

1400

1200

1000

700

a b and c a 2

Claims (1)

METHOD FOR PRODUCING PHOSPHORIC ACID, including treating phosphate feedstock with reverse phosphoric acid, separating the insoluble residue by filtration, treating the filtrate with sulfuric acid, crystallizing the calcium sulfate precipitate, followed by separating the product solution from the calcium sulfate precipitate by filtration, washing and returning the washing water to the treatment stage as a reverse phosphoric acid, characterized in that, in order to reduce the content of impurities of iron and aluminum in the product and increase productivity filter tion of insoluble residue, raw phosphate are premixed with silica in a weight ratio of SiO ₂ § PjOj- and the feedstock (1,31,8): 1 and the reverse processing of phosphoric acid is carried out at 40-70 ° C.