METHOD FOR ACID TREATMENT OF POOR PHOSPHORITES Russian patent published in 2010 - IPC C05B11/00 

FIELD: chemistry.

SUBSTANCE: invention relates to fertiliser industry, specifically to production of compound fertilisers through acid decomposition of natural phosphates. The method for acid treatment of phosphorites involves preliminary calcination of mineral raw material, acid decomposition, separation of phosphoric acid solution from insoluble residue with its subsequent processing into phosphorous compound fertiliser. After calcination the mineral material is crushed to 3.1-5 mm particles. The crushed material undergoes acid decomposition at 10 - 30°C using hydrochloric acid, nitric acid or a mixture of nitric acid and sulphuric acid. The crushed material undergoes acid decomposition using hydrochloric acid containing 10-20% hydrogen chloride, or nitric acid containing 45-55% nitric acid, or a mixture of nitric acid and sulphuric acid containing up to 25 wt % sulphuric acid. The phosphoric acid solution is separated from the insoluble residue through filtration at 50-60°C.

EFFECT: method increases output due to acceleration of filtration of insoluble residue, removal of iron and aluminium impurities from phosphoric acid, exclusion of steps for diluting and evaporating phosphoric acid solution.

3 cl, 8 tbl, 10 ex