Mineralogical and processing features of Khibiny apatitenepheline ores

Abstract

This article discusses various process intensification factors for the processing of Khibiny apatite-nepheline ores . It includes an overview of the available intensification solutions for the stages of crushing, grinding, and flotation. According to the authors, finer crushing is advisable. With the ore strength varying between 22 and 160 MPa, finer crushing would allow the plant feed to be sorted by physical properties and apatite grades. At the grinding stage, apatite liberation should be monitored with due account of its genetic feature: it is present in the ore in two forms, as free coarse-grained particles and as bound fine-crystalline particles in poikiloblasts in rock-forming minerals. The strength values are 32 MPa for the free apatite and 180–190 MPa for the poikiloblasts; therefore, apatite liberation is a two-stage process. Apatite flotation is negatively affected by higher concentrations of Sr and REE, which replace CaO in the apatite structure and contribute to the formation of Na on the surface of the crystal lattice. Changes in the lattice cell structure may inhibit apatite flotation. The total concentration of SrO + REE2O3 varies in the Khibiny Mountains apatite between 1 and 57 wt%. A change in the apatite properties possibly occurs at Σ (5.36SrO + 2.05REЕ2O3) = 7.41 wt% with Na2O at approximately 0.5 wt%.The authors would like to thank S. A. Bogdanov, Chief Mineral Engineer at NWPC JSC, and A. S. Maslyakov, Mineralogist at the Quality Control Department of NWPC JSC, for their most valuable comments.The work has been completed in the framework of Research Topic No. 0226-2019-0053 of the Geological Institute of the Kola Science Center of the Russian Academy of Sciences.