Physical and Mechanical Properties of Np-Fertilizers Derived from Ammonium Nitrate and Guliob Phosphorite

Abstract

This study examined the production of NP fertilisers by incorporating Guliob phosphorite (GP) into molten ammonium nitrate (AN) at AN weight ratios ranging from 99.5:0.5 to 65:35. The phosphorite-nitrate melt was granulated by prilling, and the chemical composition and selected physicochemical properties of the resulting products were evaluated. Increasing GP content decreased total nitrogen from 34.74% to 22.73%, whereas total P2O5 and CaO increased from 0.052% to 3.673% and from 0.12% to 10.31%, respectively. The interaction of GP with the AN melt at 170-175°C promoted partial activation of phosphate and calcium compounds, increasing the proportion of assimilable P2O5 and CaO. The most suitable compositions were identified as AN = 97.5:2.5 for non-caking AN and AN = 80:20 for thermally stabilised nitrate. These samples contained Ntotal., P2O5total. and CaOtotal. at 34.05%, 0.24% and 0.69%, and 28.0%, 2.05% and 5.90%, respectively. Their granule strengths were 4.09 and 9.69 MPa, exceeding that of conventionally produced magnesite-modified ammonium nitrate (1.58 MPa). GP addition also reduced adhesion, porosity and diesel fuel absorption, indicating improved structural density and handling safety. The findings show that GP can function as both a phosphate-bearing additive and a structural modifier for producing NP fertilisers with improved physical and mechanical properties.