Investigation of rheological properties of ammonized suspensions in the NH₄⁺–PO₄^3-–SO₄^2-–H₂O system

Abstract

The results of studies of rheological properties of ammonized suspensions in the NH4+–PO43—SO42-–H2O system in the temperature range of 80–95 °С and the NH3 : H3PO4 mole ratio from 0.6 to 1.6 are presented. The results of the studies made it possible to establish that differences in the content of sulfate and phosphate ions in the NH4+–PO43—SO42-–H2O system lead to a significant change in the solubility and position of the crystallization fields and, as a result, to a change in viscosity. To ensure the necessary mobility of the suspension after the first neutralization step, an optimal H3PO4 : H2SO4 mole ratio interval must be maintained for each fertilizer grade. Maximum viscosity values are characteristic of fertilizers, for which this ratio is close to the equimolar and decreases as it increases. It has been found that each grades and molar ratio of NH3 : H3PO4 correspond to a certain range of excess moisture values, which can be removed while maintaining sufficient mobility of the system. The highest rates in terms of the possible amount of moisture removed are brands with a lower ratio of N : P2O5. With an increase in the degree of ammonization, there is an increase in viscosity and a sharp decrease in excess moisture, which can be removed for all tested grands. The obtained results will be used in the development of new technology for obtaining complex fertilizers such as sulfoammophos and NPK fertilizers based on staged ammonization of acids.