Pilot-scale study on enhanced carbothermal reduction of low-grade pyrolusite using microwave heating

Abstract

Microwave heating through materials' dielectric loss endows energy saving and consumption reduction and production clean characteristics. Pilot-scale study was initiated to evaluate the enhanced effect of microwave heating on carbothermal reduction process of pyrolusite. Results indicated that carbothermal reduction process for low-grade pyrolusite was divided into three stages identified by temperatures: <145 °C, 145 °C–400 °C, >400 °C. Meanwhile, ƞMn value of 95.38% can achieve at 650 °C for 60 min with 15% coal addition, with low Fe2+ content, indicating efficient pyrolusite reduction by microwave heating. Moreover, MnO2 peaks disappeared and MnO peaks were detected and product surface became loose and porous with numerous cracks and holes, meanwhile grain shape became more regular with a smaller particle size after further microwave treatment. The study highlights that the non-conventional technology by microwave heating to reduce low-grade pyrolusite is very promising and could be considered for full scale applications.