Kinetics characteristics and microwave reduction behavior of walnut shell-pyrolusite blends
Li, Kangqiang; Jiang, Qi; Chen, Guo; Gao, Lei; Peng, Jinhui; Chen, Quan; Koppala, Sivasankar; Omran, Mamdouh; Chen, Jin (2020-09-28)
Kangqiang Li, Qi Jiang, Guo Chen, Lei Gao, Jinhui Peng, Quan Chen, Sivasankar Koppala, Mamdouh Omran, Jin Chen, Kinetics characteristics and microwave reduction behavior of walnut shell-pyrolusite blends, Bioresource Technology, Volume 319, 2021, 124172, ISSN 0960-8524, https://doi.org/10.1016/j.biortech.2020.124172
© 2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license by http://creativecommons.org/licenses/by-nc-nd/4.0/.
https://creativecommons.org/licenses/by-nc-nd/4.0/
https://urn.fi/URN:NBN:fi-fe202201209581
Tiivistelmä
Abstract
Combining biomass pyrolysis with microwave heating technologies provides a novel and efficient approach for low-grade pyrolusite reduction. The microwave reduction behavior and pyrolysis kinetic characteristics of walnut shell-pyrolusite blends were explored. Results indicated the optimal reduction parameters were: reduction temperature of 650 °C, holding time of 30 min, Mbio/More of 1.8:10, and microwave power of 1200 W. The co-pyrolysis characteristics of the blends included four stages: dehydration, pre-pyrolysis, intense pyrolysis and reduction, and slow pyrolysis and reduction. Fitting analysis based on Coats-Redfern method revealed that chemical reaction was the control step of the process of reducing pyrolusite by biomass, which the finding matched to the isothermal kinetic analysis results determined through unreacted shrinking nuclear model. The activation energies and pre-exponential factors were determined at 5.62 kJ·mol⁻¹–16.69 kJ·mol⁻¹ and 0.0426 min⁻¹–0.515 min⁻¹. The work provides sound references for promoting the industrial application of the combined method on minerals reduction.
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