Research On The Biomass/Charcoal Magnetic Roasting-Magnetic Separation Of Low-Grade Limonite

Abstract:In recent years, China’s steel production continued to rise with high dependence on foreign iron ore resources, which made the utilization of its own low-grade iron ore resources necessary. Limonite in China has proven reserves of approximately1.23billion tons, most of which have not been effectively utilized. Magnetic roasting is one of the most effective limonite processing methods. However, using coal or coal gas as reducing agents, traditional magnetic roasting process leads to high consumption of fossil raw materials and serious pollution. In this dissertation, biomass/charcoal in place of coal were used as reducing agents in the magnetic roasting and magnetic separation of low-grade limonite.The elemental analysis、industrial analysis and thermal analysis of the reductants showed that anthracite had the lowest volatile content, followed by hard charcoal、black charcoal, while peanut shells and straw had the highest volatile. With much higher volatile than anthracite, biomass is easier to burn and the combustion reaction temperature is much lower. The combustion reaction temperature for hard charcoal and black charcoal is100℃lower than anthracite, while for peanut shells and straw, the temperature is200℃lower than anthracite.With biomass and biomass charcoal as reducing agent respectively in the magnetic roasting, under the conditions of roasting temperature of750℃, roasting time of15minutes, good magnetic results was achieved. Grinding and magnetic separation of the roasted ore showed that using biomass and biomass charcoal as reducing agents, the resultant iron ore concentrates had relatively high iron grade(>60%) than anthracite as reductant(58.66%).Thermodynamic analysis showed that limonite can be reduced to magnetite by the reducing gas generated during the combustion、 pyrolysis of anthracite or biomass at750℃, but CO、CO2generated by the combustion or pyrolysis of biomass are much more than that of anthracite. The biomass has stronger ability to produce reducing gas than anthracite, which is conducive to the magnetization process. XRD patterns of the roasted ore and microstructure analysis showed that the main iron material after roasting is magnetite.