A pilot study on recovery of iron from sulfur-bearing hematite ore using hydrogen-based mineral phase transformation followed by magnetic separation

Abstract

Sulfur is a harmful impurity in iron ore, which seriously affects the subsequent smelting process and product quality. In this study, a novel process of hydrogen-based mineral phase transformation followed by magnetic separation was proposed to treat sulfur-bearing refractory iron ore. The results of pilot-scale experiments showed that in the oxidation heating stage, the sulfur element in the ore was oxidized to form SO2. During the reduction roasting stage, the hematite within iron ore powder was almost entirely transformed into magnetite at a reduction temperature of 520 °C using a gas combination of 45 % H2- 15 % CO- 40 % N2, which significantly enhanced the magnetism of the particles. At this time, iron minerals could be effectively recovered by a grinding and low-intensity magnetic separation process. Under the optimum roasting and magnetic separation conditions, the iron grade of magnetic concentrate reached 66.40 %, the iron recovery was 92.44 %, and the sulfur content decreased significantly from 0.547 % to 0.038 %. The hydrogen-based mineral phase transformation technology showed unique technical advantages and environmental potential in treating sulfur-bearing refractory iron ores.