Complex Nitrogen-phosphorus-sulfur-containing Fertilizers Based on Ammonia Salt, Phosphate Rock and Phosphogypsum

Abstract

The chemical industry of Uzbekistan has all the prerequisites for creating the production of complex (nitrogen-phosphorus, nitrogen-phosphorus-potassium, nitrogen-phosphorus-sulfur-containing and others) fertilizers based on ammonium nitrate (AN). Phosphogypsum (PG), a waste product from the production of extraction phosphoric acid (EPA), can serve as an additive to AN. About 80 million tons of PG have been accumulated on the territory of Ammofos-Maxam JSC alone. There is no acceptable technology for its disposal yet. And as a phosphate additive – phosphate rock (PR) of Kyzylkum. The production of granular complex fertilizers by direct mixing of AN melt with PR followed by the addition of PG is the most promising from the point of view of low cost and manufacturability, it is also environmentally friendly. In this case, PR phosphorus transforms into a form that is assimilated by plants. And PG in the AN melt undergoes conversion with the formation of soluble ammonium sulfate. When obtaining samples of NPS fertilizers, the mass ratio of AN:PR varied from 100:3 to 100:50. And the PG additive was taken in amounts of 5, 10 and 15% of the total mass of the mixture of AN and PR. To granulate the nitrate-phosphate-gypsum melt, the pelletizing method was used. It has been shown that melted nitrate activates PR, that is, it converts the P2O5 form that is indigestible in it into a form that is digestible for plants. In this case, PG undergoes conversion with the formation of ammonium sulfate. The addition of both FM and PG to AN significantly increases the strength of the latter's granules. If for pure AN it is equal to 1.32 MPa, then for a fertilizer with a mass ratio of AN:PR = 100:20 with the addition of 5% PG this figure is already 8.54 MPa.