Energy analysis on Coalbed Methane (CBM) coupled power systems

Coalbed Methane (CBM) contains 97% of CH4 and very less amount of sulphur. Methane is a very high calorific value (≅55.7 MJ/kg) gas as well as a greenhouse gas, which gets adsorbed on coal beds during coalification. Hence, capture of this CBM gas prior to coal mining not only prevents fire hazard but also the emission of greenhouse gas into the atmosphere. As the CBM gas is enriched in chemical energy, it is a promising source for power generation. In the present study, Raniganj (Jharkhand, India) Coal Field (RCF) properties are considered for CBM case study. A detailed energy analysis for the CBM and ECBM integrated carbon neutral power generating systems such as steam turbine, combined cycle (CC) and fuel cell systems is presented and the net thermal efficiency of each power plant with carbon capture and storage is estimated. High pressure coal seam is considered for combined cycle and solid oxide fuel cell (SOFC) cycle operation. Integration of power plant with CBM is studied for various coal seam operating pressures in the range of 3-1 MPa and a high net thermal efficiency of 68.3% is found at 30 bar with carbon capture and storage (CCS) for CBM integrated fuel cell cycle. In case of CBM integrated combined cycle and steam turbine system, a net thermal efficiency of 45% and 41% is estimated, respectively. An increase in 0.5% net thermal efficiency is calculated for ECBM case as compared to CBM under identical operating conditions of coal seam.