Dielectric characterisation and reduction properties of the blending mixtures of lowgrade pyrolusite and waste corn stalks in the microwave field
Du, Jinjia; Gao, Lei; Yang, Yong; Guo, Shenghui; Omran, Mamdouh; Chen, Jin; Chen, Guo (2021-07-30)
Du, J., Gao, L., Yang, Y., Guo, S., Omran, M., Chen, J., & Chen, G. (2021). Dielectric characterisation and reduction properties of the blending mixtures of low-grade pyrolusite and waste corn stalks in the microwave field. Fuel, 305, 121546. https://doi.org/10.1016/j.fuel.2021.121546
© 2021 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/.
https://creativecommons.org/licenses/by-nc-nd/4.0/
https://urn.fi/URN:NBN:fi-fe2021081843560
Tiivistelmä
Abstract
Recently, pyrometallurgical reduction of low-grade pyrolusite is one of the potential techniques for expanding the resources for manganese. However, the process has a high cost on fossil energy and produces a large amount of greenhouse gases. This work proposed a novel method of using biomass, namely corn stalks, to reduce and roast low-grade pyrolusite under microwave field to provide positive alternatives for fossil energy. The microwave-assisted reduction was studied systematically, and the corresponding mechanism was also studied by thermodynamic analysis and dielectric properties analysis. Results indicated that co-pyrolysis reduction characteristics of the mixtures were mainly divided into three stages: the pre-reaction stage (25 °C–196 °C), activated pyrolysis reduction stage (196 °C–480 °C), and carbonisation stage (>430 °C). The mechanism of MnO₂ reduction is attributed to reductive volatiles (H₂, CO, CH₄) and the fixed carbon (C) produced by biomass pyrolysis. Meanwhile, the reduction efficiency of Mn can achieve 97.2% at 650 °C for 60 min with 25% corn stalks, indicating efficient pyrolusite reduction by microwave heating. These results enrich the fundamental knowledge on the corresponding industrial technology development.
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