METHOD OF PREPARING COMPLEX FERTILIZERS Russian patent published in 2000 - IPC

FIELD: nitric acid processing of phosphate ores to complex fertilizers. SUBSTANCE: method comprises decomposition of apatite concentrate with nitric acid, isolation of calcium nitrate by crystallization, neutralization of nitrogen phosphate extract with ammonia, evaporation, mixing with ammonium nitrate meet and potassium salt, granulation and drying of final product. After separation of calcium nitrate, nitrogen phosphate extract is mixed with low- grade phosphorite stock at P₂O₅ phosphorite to P₂O₅ apatite ratio of 0.05-0.8: 1 prior to or after ammonization or after evaporation. EFFECT: lower consumption of apatite concentrate per 1 ton of fertilizer and P₂O₅ and lower consumption of nitric acid without reduced content of assimilable forms of phosphorus in fertilizer and without reduced production of ammonium nitrate by-product. 5 ex, 1 tbl