Estimation of hydrogen release and conversion in coal-bed methane from roof extraction in mine goaf

In order to effectively utilize the coal bed methane (CBM) resources extracted from underground coal mines, an evaluation method of hydrogen production capacity from CBM is established by means of experiments and theoretical models. The main components of CBM collected from coal working face are measured by gas chromatography, and the release law of trace hydrogen is obtained. Considering gas extraction technology in goaf roof, a computational fluid dynamics model for seepage problem in porous media is presented. The law of gas migration in goaf under extraction conditions is obtained by simulation, and the extraction rate of CBM and methane/hydrogen content are predicted. The technology of producing hydrogen from CBM extracted from goaf under low gas concentration is discussed, and the effect of methane content on auto-thermal conversion efficiency is analyzed. Under the condition of this study case, the theoretical estimation of pure hydrogen produced from goaf extraction can reach more than 10,000 m³ per day. The presented results could provide a new route for the utilization of CBM by underground extraction.