METHOD FOR PRODUCTION OF COMPLEX FERTILIZERS Russian patent published in 2006 - IPC C05B11/06 C05B7/00 

FIELD: chemistry, agriculture, fertilizers.

SUBSTANCE: invention relates to method for production of complex fertilizers by decomposition of apatite concentrate with nitric acid by using low-grade phosphate raw materials are used. Claimed method includes decomposition of apatite concentrate with nitric acid, calcium nitrate isolation from nitrophosphate extract, crystallization followed by conversion thereof in ammonium nitrate; neutralization of separated nitrate-phosphate solution with ammonia, vaporization, blending of evaporated pulp with low-grade phosphate raw materials, ammonium nitrate and potassium salt; granulation and drying of finished product. According to this invention low-grade phosphate raw materials are preliminary treated with conversion ammonium nitrate solution at S:L = 1:1-3 to produce in slurry ratio of P₂O_5digestible:P₂O_5total = 35-45 %. PH of conversion solution is maintained preferably either 0.3-1.5 or 7.5-9, with the proviso, that when pH is 0.5-1.5 ratio of apatite and low-grade phosphate raw materials calculated as P₂O₅ is (1.5-3):1; and when pH is 7.5-9 abovementioned ratio is (4.2-5):1.

EFFECT: product of prolonged action, simplified process without losses of product quality.

2 cl, 1 tbl