A coupled thermal-force-chemical-displacement multi-field model for underground coal gasification based on controlled retraction injection point technology and its thermal analysis

Underground coal gasification is an essential means of meeting the growing energy needs of some countries. In this paper, a new numerical simulation method of thermal-force-chemical-displacement multi-field coupling is developed, and in order to better adapt to the actual working conditions, taking Shanjiaoshu Coal Mine as the geological background, the first gasification working face of No. 12 coal seam is simulated based on the controlled retraction injection point technology. This method is used to simulate the heating of coal body by the ignition device at the initial stage of UCG, the chemical-thermal changes triggered by spontaneous combustion of the coal body under the continuous backward movement of the injection point, and the simulation of the formation of the cavity after the coal gasification reaction. Finally, the evolution of temperature and displacement fields in No.12 coal seam after gasification reaction is analyzed. Therefore, this study aims to simulate the actual working conditions more realistically, optimize the UCG technology, and produce more clean energy syngas to improve the energy situation in China.