Responses of physico-chemical properties and CH4 adsorption/desorption behaviors of diverse rank coal matrices to microwave radiation.

To assess feasibility of microwave radiation in CH 4 production, temperature rise of coals under microwave field and resultant alterations in physico-chemical properties were addressed. Results indicated that the temperature rise of coals is dominated by mineral compositions. The bulk temperature of coals containing strong microwave-absorbing minerals such as pyrite, smectite, and kaolinite rises markedly. The elevated temperature breaks alkyl side chains and aromatic rings of coals. Moreover, the total oxygen-containing functional groups decrease by radiation. Generally, the radiation reduces the micro- and mesopores of coals. Besides, the pore surface of low-rank coals after radiation becomes smooth, whereas that of medium- and high-rank coals becomes rough. Finally, the radiation decreases CH 4 maximum adsorption capacity by 6.74–36.69%. The radiation also diminishes CH 4 adsorption/desorption hysteresis for low-rank coals, while an opposite trend exists in medium- and high-rank coals. Such variations rely on pore structure responses to microwave. Overall, microwave radiation could promote CH 4 recovery. [Display omitted] • Temperature rise of coals under microwave field depends on mineral compositions. • Microwave radiation breaks alkyl side chains and aromatic rings of coals. • CH 4 adsorption/desorption on coals relies on pore structure responses to microwave. • Microwave radiation could enhance coalbed methane recovery. [ABSTRACT FROM AUTHOR]

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