METHOD FOR PREPARING COMPLEX FERTILIZER Russian patent published in 2004 - IPC

FIELD: chemical technology, fertilizers. SUBSTANCE: invention relates to methods for preparing complex nitrate-phosphate fertilizers with the prolonged effect used widely in agriculture. Method involves decomposition of apatite concentrate with nitric acid, isolation of calcium nitrate by crystallization, treatment of carbonate-containing low-grade phosphate raw for two stages. Method involves using nitratephosphate solution neutralized with ammonia preliminary, additional ammonization of the prepared suspension, its evaporation, mixing evaporated pulp with ammonium nitrate melt and potassium salt and drying the ready product. On the first stage for decomposition of carbonate-containing low-grade phosphorus raw preliminary neutralized solution is fed in the amount to provide the ratio liquid : solid at this stage = (2.5-3.5):1. Remained part of nitrate-phosphate solution is fed to the second treatment stage and process is carried out in dispersing nitric acid-containing liquid reagent in the amount 5-7% as measured for HNO₃ of stoichiometry for apatite CaO. Preliminary neutralization of part of nitrate-phosphate solution with ammonia is carried out to pH 0.6-2.5. Nitric acid or part of nitrate-phosphate solution is used as liquid reagent fed for dispersing. Method provides reducing foam formation in the process, to enhance utilization coefficient of equipment volume and to retain quality of product. EFFECT: improved preparing method. 2 cl, 4 ex