Preparation of Multifunctional Fused Magnesium Phosphate Fertilizer from Low-Grade Phosphate Ores

Low-grade phosphate ores are the main phosphorus resources in China, and it’s difficult to upgrade owing to most ores belonging to collophanite with fine-grained dissemination. These inferior ores with high silicon and magnesium contents are favorable raw materials to produce fused magnesium phosphate fertilizer (FMP) for the crop growth. However, high temperature of Ca3(PO4)2–SiO2–MgO system for the smelting of phosphorite resulted in the energy-extensive consumption. In current study, the effect of K2O addition on the smelting of phosphorite was investigated via thermodynamic calculations and experiment validation to reduce the smelting temperature. It has been found that 3–5% K2O can reduce the melting temperature of the Ca3(PO4)2–SiO2–MgO ternary system by about 80 °C. Moreover, K2O addition can enhance the activities of various nutrients such as potassium and magnesium in the FMP products after smelting and water quenching, and the effective conversion of the nutrients is increased by 5% compared with that without K2O addition.