Prospects of green extraction of iron from waste dumped flotation tailings by H2: A pilot case study

Abstract

Flotation tailings are a secondary iron ore resource with abundant reserves and recycling value. In this study, low-grade flotation tailings (TFe = 21.86%) with silica of 57.85% has been studied by the hydrogen-based suspension magnetization roasting (HSMR) and magnetic separation varying the roasting temperature, reductant concentrate, total gas flow, and feeding rate to evaluate their effect on iron grade and iron recovery in magnetic concentrate. According to the pilot case study, the best iron concentrate (Fe grade of 66.65% and recovery of 80.11%) was obtained at a temperature of 500 °C, H2 concentration of 14.4%, the total gas flow of 18.0 m3/h, and feeding rate of 100 kg/h. After HSMR, the phase transformation results indicated that the weakly magnetic of hematite in flotation tailings were transform to the stronger magnetic magnetite, and the iron in magnetite increased from 17.57% in flotation tailings to 97.73% in magnetic concentrate. Microstructure analysis is presented which shows that the HSMR process destroys the structure of the iron minerals particles, making them form more pores and microcracks, which greatly reduces the structural strength of the particles and helps to reduce the energy consumption of the grinding operation. This study provides a pilot case of HSMR for the green and low-carbon development of the iron and steel industry.