METHOD OF PRODUCING WET-PROCESS PHOSPHORIC ACID Russian patent published in 2016 - IPC C01B25/00 C01B25/22 C01B25/231 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing wet-process phosphoric acid from high-quality phosphorites and apatite concentrates. Method includes decomposition of phosphate material with a mixture of phosphoric acid and sulphuric acid in presence of recoverable in decomposition zone pulp with frequency of 10-85 with crystallisation of calcium sulphate dihydrate, cooling 30-100 vol% of circulating pulp with air in mode of foam layer at temperature gradient between cooled and delivered for cooling pulp 0.5-4.0 °C, aging dihydrate pulp, separation of acid from calcium sulphate precipitate by filtration, recrystallisation of calcium sulphate dihydrate to hemihydrate by adding concentrated sulphuric acid at a temperature of 85-95 °C for 0.5-2.0 h, separation of obtained pulp by filtration with water washing of precipitate of α-hemihydrate of calcium sulphate in counter-flow mode, return of recycled phosphoric acid to step of decomposition of phosphate material, drying and regrinding washed α-hemihydrate of calcium sulphate and further use thereof as gypsum binder. According to method decomposition of phosphate raw material is carried out in presence of acid-soluble additives of aluminium compounds with content in phosphoric acid solution of 30.5-34.0 wt% P₂O₅, 0.75-1.2 wt% Al₂O₃ and temperature of 85-95 °C, after ageing dihydrate pulp is divided into two streams, one of which is in an amount of 25-50 vol% of total volume of pulp is separated by filtration into product phosphoric acid and unwashed calcium sulphate dihydrate, latter is directed to step of recrystallisation, mixing it with second stream of dihydrate pulp and sulphuric acid, taken in amount required to maintain in pulp liquid phase 7-11 wt% H₂SO₄, and to hemihydrate of calcium sulphate is added modifying additives in amount of 0.1-0.5 wt CaO and 0.4-2.0 wt% K₂SO₄ to mass α-hemihydrate.

EFFECT: production of phosphoric acid.

1 cl, 1 tbl, 2 ex