METHOD OF RESIDUAL PRODUCTS CONTAINING PHOSPHORIC ACID PROCESSING TO CALCIUM PHOSPHATES Russian patent published in 2008 - IPC C01B25/32 

FIELD: chemistry.

SUBSTANCE: method of processing of residual products containing phosphoric acid to calcium phosphates comprises its mixing with calcium-containing compounds, separation of derived slurry with filtration and drying. The limestone is used as calcium-containing compound, initially it is fed for mixing in quantity necessary for monocalcium phosphate, then derived slurry is divided to two flows in ratio 1:(1.5-4), the major flow is mixed with lime taken in quantity necessary for dicalcium phosphate formation, derived slurry is separated with filtration and minor flow of monocalcium phosphate slurry is added to separated dicalcium phosphate before drying and granulating. Preparation of monocalcium phosphate slurry is carried out in two stages, at first stage the phosphoric acid is mixed with limestone up to mixture pH =2.9-3.1, at second stage - up to mixture pH =3.5-3.7, during mixing of monocalcium phosphate slurry with lime pH is maintained in the range 5.4-5.6. Drying and granulating are carried out at the same time in drum granulator-dryer.

EFFECT: method enables to process the residual products to granulated calcium phosphates with usage the lowest-cost raw materials.

3 cl, 1 tbl, 1 ex