Experimental simulation of hard coal underground gasification for hydrogen production

The main objective of this study was the assessment of the feasibility of applying the underground hard coal gasification in the production of a hydrogen-rich gas. In the course of the experiment the so-called two-stage gasification process in which oxygen and steam were supplied to the reaction zone separately in alternate stages was investigated. For this purpose a special surface reactor has been constructed, in which the underground conditions were to be imitated both in respect to the coal seam and the surrounding rock layers. The surface simulation of the underground gasification was carried out on extra large coal samples, which allowed the recreation of near real underground conditions. In the reactor an experiment lasting almost 7 days has been performed, with the average hourly gas yields of 7.8 m³/h and 9.2 m³/h for the oxygen and the steam gasification stages, respectively. The average hydrogen concentration during the oxygen stage (heating up) was 15.28% with the maximum of 54.4%. The average hydrogen concentration during the steam stage was 53.77% with the maximum of 62.90%. Thus the feasibility of hydrogen-rich gas production in the process of underground gasification of hard coal has been demonstrated. During the course of the surface experiment an original and unprecedented database of temperature profiles has been acquired which now constitutes an invaluable source of thermodynamic information for the prospective underground gasification activities.