PRODUCING NITROGEN-PHOSPHORUS-POTASSIUM OR NITROGEN-PHOSPHORUS MATERIALS CONTAINING POLYPHOSPHATES Russian patent published in 2012 - IPC C05B11/06 C05B13/06 

FIELD: chemistry.

SUBSTANCE: nitrogen-phosphorus-potassium (NPK) or nitrogen-phosphorus (NP) material from nitrophosphate process contains at least 5 wt % condensed phosphates (polyphosphates), preferably at least 8% and more preferably at least 10 wt % phosphates in form of condensed phosphates (polyphosphates). The total amount of phosphorus-containing compounds in NPK or NP material contains 50-95 wt % water-soluble phosphates and more than or equal to 93 wt % citrate-soluble phosphates. The method of producing nitrogen-phosphorus-potassium (NPK) or nitrogen-phosphorus (NP) material involves a step (1) for decomposing apatite in nitric acid, a step (2) for crystallisation on which temperature is controlled in a range from -10 to +10°C, a step for filtering calcium nitrate, a step (3) for neutralisation with ammonia, a step (4) for evaporation and a step for adding potassium after step (4). Pressure is lowered at step (4) for evaporation such that content of water in the evaporated NP liquid is approximately less than or equal to 1.0 wt %. Temperature is raised at step (4), and controlled at step (2) for crystallisation, which results in formation of polyphosphate.

EFFECT: invention enables to obtain solid NPK fertiliser containing polyphosphates.

19 cl, 7 tbl, 4 ex, 1 dwg