Non-pyrolysis microwave heating as coal pretreatment for in-situ combustion: reactivity and microstructure

Abstract

ABSTRACT Microwave heating without pyrolysis is a promising technology as coal pretreatment for in-situ combustion. In order to study the reactivity of the modified coal from non-pyrolysis microwave heating, Shenmu bituminous coal was subjected to microwave at 700 W for limited time (90 s and 180 s) and the samples were tested by the thermal analyzer, NOVAtouch analyzer and X-ray diffractometer in this work. The weight loss curves of original coal and modified coals are similar, but the weight loss rate is faster for combustion stage when t m is longer. As t m increases, ignition temperature barely changes, while burnout temperature dramatically decreases. Both the specific surface area and pore volume decrease with increasing t m. When t m increases from 0 to 90 s, the microcrystalline structure is less ordered, while aromaticity is larger; when t m increases from 90 s to 180 s, the microcrystalline structure is more ordered, while aromaticity is smaller. When t m increases, the side chains decrease first and then increase, while the reactive oxygen-containing groups keep increasing. This work is essential for grasping the effect of microwave pretreatment on the ISC performance.