METHOD FOR PREPARING CHLORINE-FREE NPK-FERTILIZER Russian patent published in 2004 - IPC

FIELD: chemical technology, fertilizers. SUBSTANCE: invention relates to technology for preparing complex mineral fertilizers, in particular, chlorine-free fertilizers by method of nitric acid decomposition of natural phosphates. Method involves the following stages. Ammonization of nitrate-phosphate solution is carried out firstly to pH 2.5-3.0 and then to pH 5.8-6.0. Prepared solutions are evaporated to the residual moisture value 0.4÷1.0% to obtain homogenous melts with a low viscosity index. NPK-fertilizer is granulated by prilling method using potassium sulfate as a potassium component that is added before prilling stage immediately. Method provides preparing NPK-fertilizer containing water-soluble sulfur and displaying the high agrochemical effectiveness. EFFECT: improved preparing method. 3 tbl, 1 ex