Key Laboratory of Unconventional Metallurgy, Ministry of Education, Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, PR China; Key Laboratory of Green-Chemistry Materials in University of Yunnan Province, Yunnan Minzu University, Kunming 650500, PR China; Hunan Provincial Key Laboratory of Efficient and Clean Utilization of Manganese Resources, Central South University, Changsha 410083, Hunan, PR China. Electronic address: [Email]
In this work, dielectric properties and thermochemical characteristics of mixtures of walnut shell and manganese ore were systematically investigated. Results indicated that reducing manganese ore by walnut shell was divided into four stages identified by temperatures: <150 °C, 150 °C-300 °C, 300 °C-480 °C, greater than 480 °C. Higher than 200 °C, the dielectric constants (εr'), dielectric loss factors (εr″) and loss tangent coefficients (tan δ) of mixture at a ore/biomass mixing ratio of 10:1.2 were observed to suddenly drop to low levels, with 5.107 (F/M), 8.5 × 10-4 (F/M), 1.66 × 10-4 (F/M), respectively; which were attributed to the MnO2 reduced by the reductive volatiles produced by biomass pyrolysis. Meanwhile, the volatiles rendered a decrease in density and dielectric properties of the mixture. The work highlights the possibility of reducing manganese ore by walnut shell with microwave heating.