On the issue of the rational planning of mining operations for underground coal gasification

Purpose. To substantiate the spatial layout parameters of underground gasifiers, considering the operational losses of coal within the mine field. Methods. The underground coal gasification process was studied under laboratory conditions through physical modeling of a coal seam using a specialized stand-based setup. This approach enables reproducing key elements and parameters of the gasification process in a controlled environment. The setup simulates the characteristics of coal seam occurrence, within which operational boreholes are formed – one for supplying the blast mixture (air, oxygen, or steam) and another for extracting the producer gas. Results. The study examined the formation parameters of the gasified cavity of the underground gasifier at the late stage of mining during coal gasification via vertical boreholes. Quantitative indicators of coal conversion were established for the gasification of thin coal seams. A comparative analysis of operational coal losses within the mine field was conducted for two development systems: one with the parallel placement of underground gasifiers and another involving zonal distribution of losses within the gasifiers. Originality. It has been established that the maximum width of the underground gasifier (13.9–15.4 m) and the length of the combustion front (33.6–37.3 m) at the final stage of gasification directly depend on the thickness of the coal seam (0.7–1.2 m). It was revealed that the gasifier width follows an exponential growth pattern while the combustion front length changes according to a logarithmic relationship. These dependencies are essential for predicting the dynamics of gasified cavity development in underground gasifiers and determining optimal locations for operational boreholes. Practical implication. A coal seam development system that includes zonal distribution of losses within underground gasifiers’ boundaries is proposed based on the cavity formation parameters at the late mining stage. An algorithm is also proposed to estimate operational coal losses during underground gasification.