Model experimental study on underground gasification process with reverse combustion of bituminous coal

Reverse combustion gasification is a method where the combustion working face moves against the direction of the airflow with no need for repeated ignition, facilitating continuous gasification. This study conducted a model experiment of underground coal gasification (UCG) using this technique to verify the feasibility of the reverse combustion gasification process. Experimental results show that hot oxygen, with a flow rate of 3 m³/h and a temperature of 170-180 ℃, could ignite the coal seam. As oxygen volume fraction rose from 40% to 100%, effective components exhibited initial increase and subsequent decrease, peaking at 80% of oxygen volume fraction. Rising oxygen volume fraction resulted in decreasing gas yield, while the efficiency of cold gas showed initial increase and subsequent decrease. Oxygen volume fraction exerted little effect on the moving velocity of the reverse combustion working face: with oxygen volume fraction of 42.99%, 60.24% and 79.03%, the moving velocities in the reverse direction (transverse) were 4.28 cm/h, 4.78 cm/h and 4.69 cm/h, while those in the coal seam (longitudinal) were 2.69 cm/h, 1.11 cm/h and 1.09 cm/h respectively. Reverse combustion could continuously form new gasification working faces, thus maintaining a continuous and stable gasification process.