METHOD OF PRODUCING PHOSPHORIC ACID TO OBTAIN ALPHA-HEMIHYDRATE GYPSUM BY WAY OF A WET METHOD AS A BY-PRODUCT Russian patent published in 2019 - IPC C01B25/226 C01F11/46 

FIELD: technological processes.

SUBSTANCE: invention relates to a method of producing phosphoric acid and obtaining, at the same time, alpha-hemihydrate gypsum as a by-product. Method comprises adding a phosphate rock powder and a portion of diluted sulfuric acid to an extraction tank, carrying out an extraction reaction therein, separating the clear liquid from the obtained mixed suspension, supplying the transparent liquid as the end product – phosphoric acid – to the acid storage tank and feeding the separated solid phase together with the rest of the mixed suspension into the crystalline form conversion vessel; adding crystalline forms of sulfuric acid and an additive for controlling conversion of crystalline forms into the crystalline form conversion vessel for 1.5–7.5 hours at 60 °C–130 °C and separation of solid and liquid phases of obtained mixed acid suspension, wherein solid phase can be dried to produce powdered gypsum or can bypass drying step, be used to produce gypsum products, such as gypsum panels, gypsum building blocks and gypsum elements, by direct addition of water.

EFFECT: invention provides reduced content of phosphorus in phosphogypsum.

17 cl, 1 dwg, 2 tbl, 4 ex