METHOD OF PRODUCING ARTIFICIAL GYPSUM STONE WHEN PROCESSING PHOSPHOGYPSUM Russian patent published in 2025 - IPC C04B11/26 C04B11/28 C04B18/04 C04B22/00 C04B103/14 

FIELD: construction.

SUBSTANCE: invention relates to processing industrial wastes of phosphogypsum to obtain construction materials and can be used to produce artificial gypsum stone used as a cement setting time regulator when adding it to clinker, and binding materials instead of natural gypsum stone. Initial phosphogypsum is purified from impurities in the form of phosphorus, fluorine and rare-earth metals by washing in two steps: at the first step - with water with extraction of water-soluble impurities, at the second stage - with mineral acid with additional extraction of water-insoluble salts of phosphorus, fluorine and rare-earth metals. Obtained paste is neutralized with lime, gypsum binder is added, the obtained mixture of hemi- and dihydrate of calcium sulphate is homogenised, after which the mixture is granulated and the obtained granules of artificial gypsum stone are dried. At the first stage, washing from water-soluble impurities is carried out with water, preferably at S:L = 1:(1.5–2) for 15–30 minutes. Washing from water-insoluble impurities is carried out at the second stage with a solution of sulfuric acid with concentration of 15–165 g/l at S:L = 1:(1.5–4.5) for 60–120 minutes. Neutralization with lime to pH 6–8, mixing with gypsum binder and homogenisation of the paste obtained from washed phosphogypsum are carried out in a mixer, for example, a bowl, for 5–30 minutes.

EFFECT: method of producing artificial gypsum stone when processing phosphogypsum enables to replace natural gypsum stone in production of cement and construction materials with artificial stone obtained from industrial wastes.

3 cl, 2 tbl, 3 ex