Study on the Method of Two-Phase Underground Coal Gasification with Unfixed Pumping Points

Abstract

In light of the unstable coal gas heating value in the underground gasification of steep coal seam, the method of two-phase underground gasification with unfixed pumping points is proposed. The structure of the multifunctional model experimental platform and the experimental system are illustrated. Additionally, the method of two-phase underground gasification with unfixed pumping points is explained. We also studied the time ratio of the first phase to the second one, the resulting coal gas heating value, and its composition and gasification velocity, and analyzed the experimental results. The results of the model experiment indicate that the H2 and CH4 content is high in the composition of the gases produced via the method of two-phase underground coal gasification with unfixed pumping points. The heating value of the gas virtually ranges from 12.0 MJ/m3 to 15.0 MJ/m3. On top of that, the method can improve the average temperature of the underground gasifier effectively and shorten the switch time of 2 phases. The method also prolongs the period of time of producing high heating-value gases by 0.67–1.5 times, as opposed to that of the mode of pumping wind (steam) with fixed points. According to the experimental results, the moving speed of the flame working area is 1.49 m/d, with the expansion speed of the channel of the coal seam 6–12 mm/h. The findings of this article will lay an important theoretical foundation for the design of the production and technological parameters in the process of field testing underground coal gasification.