Mechanism of the controlled microwave field enhancing gas desorption and diffusion in coal

HU Guozhong; ZHU Yiran; XU Jialin; QIN Wei

Abstract：Using the self-developed experimental device of coal-rock gas desorption under controlled microwave field (CMF) and the scanning electron microscopy (SEM),the effect of CMF to methane desorption and diffusion characteristic,temperature and surface structure morphology of coal were investigated.The mechanism of CMF enhancing gas desorption and diffusion in coal was explored by analyzing electromagnetic radiation heat effect and damage effect of CMF to coal.The results show that the power loss come into being as a result of microwave propagation in coal,leading to converting electromagnetic energy of CMF into thermal energy of coal and the sharp increase of temperature of coal,which present a feature of going up firstly and then keeping general linear growth.The surface structure morphology of coal is changed as a result of penetrability and selectivity action of CMF to coal,represented as a series of failure mode of coal such as shrinkage by water loss,peeling and crushing of minerals interface,formation of cracks and pores.The electromagnetic radiation heat effect and damage effect of CMF to coal improved the interaction potential of coal and methane gas molecules,methane gas molecules kinetic energy and methane diffusion channel of coal,which resulted in the improvement of the methane desorption capacity and diffusivity.