Estimation of the cavity volume in the gasification zone for underground coal gasification under different oxygen flow conditions

In this study, the impact of oxygen flow rate on the cavity of the gasification zone was analyzed through two experiments using a coaxial hole model. The oxygen flow rate was controlled between 3 L/min and 5 L/min for experiment one and between 7.5 L/min and 15 L/min for experiment two. For the estimation of the cavity volume of the gasification zone in UCG, the stoichiometric method, the Delaunay triangulation approach, and the voxelization method were used. The actual gasification zone cavity volume change was obtained by dividing the coal consumption monitored by electronic mass balance by the apparent density of the coal. After analyzing and comparing the cavity volumes of the gasification zone obtained by the three estimation methods with the actual cavity volume of the gasification zone, the results showed that the stoichiometric method had an estimation error of less than 6.5 %. The Delaunay triangulation approach could reduce the estimation error for the convex cavity volume of the gasification zone to within 10 %. The voxelization method could reduce the estimation error for the cavity volume of the gasification zone to below 8 % and accurately describe the shape of the cavity.