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

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, ƞ_Mn 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.