Microwave drying of a low-rank sub-bituminous coal |
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| Affiliation: | 1. Faculty of Chemical Engineering, Universiti Teknologi Malaysia, UTM 81310, Skudai, Johor Bahru, Johor Darul T’azim, Malaysia;2. Department of Thermodynamics and Fluid Mechanics, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, UTM 81310, Skudai, Johor Bahru, Johor Darul T’azim, Malaysia;3. Faculty of Engineering and Architecture, Department of Chemical Engineering, Balochistan University of Information Technology, Engineering and Management Sciences, Quetta, Balochistan, Pakistan;1. School of Resource, Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan, Hunan 411201, China;2. School of Energy and Safety Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001, China;3. College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China;1. National Energy Technology Laboratory, U.S. Department of Energy, Morgantown, WV 26507-0880, United States;2. AECOM, 3610 Collins Ferry Rd., Morgantown, WV 26507-0880, United States;3. Florida State University, Department of Chemistry, Tallahassee, FL 32306-4390, United States;1. Faculty of Engineering, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom;2. JKTech Pty Ltd, 40 Isles Road, Indooroopilly, QLD 4068, Australia;1. Robert M. Buchan Department of Mining, Queen’s University, Kingston, Ontario K7L 3N6, Canada;2. Department of Materials Science & Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada;3. Microwave Properties North, RR#1 Deep River, Ontario K0J 1P0, Canada |
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| Abstract: | The moisture contents of coals are often too high and need to be reduced before further processing. In this study, the application of microwave radiation as an alternative energy source for the drying of a sub-bituminous coal was investigated. Firstly, the permittivities of the coal were evaluated as a function of temperature and frequency. Secondly, the drying kinetics were studied in a 2.45 GHz microwave system and the effects of incident microwave power, sample mass and initial moisture contents were determined. The results demonstrated that microwave drying had several advantages over conventional drying such as increased drying rates and lower final moisture contents. In some tests, magnetite was added as a susceptor to increase the drying rates. Thirdly, the drying data were fitted to ten exponential decay models, and although reasonable agreement was observed with all the models, the best fit was obtained with the Midilli–Kucuk model. Finally, the effective diffusion coefficients of moisture and also the activation energy of the diffusion process were estimated and used to further elucidate the mechanism of microwave drying. |
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| Keywords: | Microwaves Drying Low-rank sub-bituminous coal Permittivities Models Effective diffusion coefficients |
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