METHOD OF PREPARING NITRIC ACID SOLUTION OF RARE PHOSPHATE MATERIAL Russian patent published in 2010 - IPC C05B11/06 

FIELD: chemistry.

SUBSTANCE: invention relates to fertiliser industry, specifically to production of compound fertilisers based on nitric acid decomposition of rare phosphorites. The method involves preparing nitric acid solution of rare phosphate material through its decomposition with nitric acid taken in super-stoichiometric excess of calcium or magnesium compounds in the phosphate material at temperature 40 - 60°C, and filtration of the formed suspension on a filter under pressure in order to separate the insoluble residue. The suspension subjected to filtering is held in a decomposition reactor for 3-5 hours. Filtration is carried out at pressure of 5-15 atm. The rare phosphate material used is crushed phosphorite with P₂O₅ content equal to 24.6 wt % or crushed phosphorite with P₂O₅ content equal to 21.0 wt %, pre-calcined at 900 - 1000°C. Nitric acid consumption is kept at stoichiometric 110-130 % of the calcium and magnesium compounds in the rare phosphate material.

EFFECT: method increases efficiency of filtering the suspension.

5 cl, 1 tbl, 4 ex