METHOD FOR PRODUCTION OF COMPLEX FERTILIZERS

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 P2O5digestible:P2O5total = 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