Iron recovery from refractory limonite ore using suspension magnetization roasting: A pilot-scale study

Abstract

Limonite ore is a potentially important iron resource and widely distributed in the world. However, it is difficult to process by traditional methods due to the high water content and fine dissemination of aluminum and silica. In this paper, typical refractory limonite ore was studied by suspension magnetization roasting and magnetic separation technology. According to the pilot-scale study, optimum roasting conditions were determined as a capacity of 120 kg/h, CO dosage of 6.5 m3/h, N2 dosage of 9.5 m3/h, roasting temperature of 460 °C, and gas flow of 16.0 m3/h. An iron concentrate with Fe grade of 64.97% and recovery of 94.53% was obtained using a suspension magnetization roasting – grinding – magnetic separation process. The material and roasted products were characterized by X-ray diffraction (XRD), mineral liberation analyzer (MLA), and backscattered electron (BSE) analyses. The results indicated that the iron oxide phase transformation was as follows goethite → hematite → magnetite → maghemite. The mineral dissemination analysis showed that fine grinding and magnetic separation was favorable to improve the quality of iron concentrates. However, some Al and Si were difficult to remove due to the isomorphism. The suspension magnetization roasting is feasible in economic terms, and the cost of magnetization roasting is $8 per ton. This technology will not only increase the available iron ore resource reserves but also alleviate the imbalance between supply and demand of iron ore in China.