Dielectric characterisation and reduction properties of the blending mixtures of low-grade pyrolusite and waste corn stalks in the microwave field. (1st December 2021)

• Record Type: Journal Article
• Authors: Du, Jinjia; Gao, Lei; Yang, Yong; Guo, Shenghui; Omran, Mamdouh; Chen, Jin; Chen, Guo
• Is Part Of: Fuel. Volume 305(2021)
• Publication Date: 2021-12-01
• Subjects: Biomass -- Low-grade pyrolusite -- Dielectric properties -- Reduction efficiency (Mn) -- Microwave pyrolysis reduction; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2021.121546
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Process analysis of pyrolusite reduction by waste corn stalks is reported. The thermodynamic analysis confirmed the pyrolusite reduction by biomass pyrolysis. The dielectric properties of low-grade pyrolusite mixed corn stalks were studied. Determination of the microwave dielectric properties of pyrolusite mixed corn stalks for the first time. 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.