Improvement of resource recovery rate for underground coal gasification through the gasifier size management

Abstract

Underground coal gasification is one of the most vital technical directions for the future development of the coal industry. Currently, numerous small-scale underground coal gasification industrial tests of different processes have been successively conducted, which has laid a solid foundation for further large-scale experiment and production. However, with the expansion of underground coal gasification experiment scale and promoting application, the surrounding rock stability and surface subsidence must be considered. Moreover, there exists a bottleneck problem, which should be solved urgently, that how to design underground gasification production for different geological conditions to improve resource recovery rate. To solve this issue, this paper analyzed the existing situation of resource recovery rate of industrial experiment for underground coal gasification without shaft. Also, the improvement method for resource recovery rate of underground coal gasification with considering of the gasifier safety and surface subsidence was proposed in combination with the technology characteristics of underground coal gasification. Meanwhile, the influence rule of gasifier parameters on the coal pillars stability and surface subsidence was revealed. From the findings in this research, it can be expected that the resource recovery rate of underground coal gasification without shaft can be increased from about 40% to more than 60% under the both conditions of the safe production of underground gasifiers and surface subsidence control. These research results are of great significance for enhancing the economic benefits of underground coal gasification and promoting its industrialization and large-scale production.