The invention discloses a gas
injection point retreating type
coal underground gasification
system and process. The gas
injection point retreating type
coal underground gasification
system comprises an
airway arranged in a
coal layer and multiple coal underground gasification units, wherein the
airway is connected to the multiple coal underground gasification units; and the technical steps are sequentially as follows: a step of cold-state testing, a step of ignition on a gasification working surface, a step of debugging of the gasification working surface and a step of gasification normal production process. According to the invention, mud can be prevented from blocking the gas
injection point efficiently, and the coal layer can be exploited to the maximum extent, so that possibility of thoroughly
cutting off the leakage of a gasification agent to a
combustion space area is realized while safe retreating in the coal underground gasification process is realized, filling of the
combustion space area is realized, collapse of the ground surface caused by the gasification is removed, stability of the gasification channel structure is guaranteed, problem of the
short circuit of the gasification agent caused by a channel which is resulted from collapse of a coal layer plate in the gasification area in the early stage and the gasification channel at the later stage of the underground gasification is solved, the quality of the
coal gas is improved, and safe and reliable
coal gas production and high gasification rate are achieved.