The Efficiencies of Internal Reforming Molten Carbonate Fuel Cell Fueled by Natural Gas and Synthetic Natural Gas From Coal

摘要

When synthetic natural gas (SNG) is produced from coal and used as a fuel in the internal reforming molten carbonate fuel cell (ir-MCFC), electric efficiency can be no greater than 31%. This is because there are several exothermic reactions in the processes of converting coal to SNG, so that a maximum 64% of coal's energy is converted into SNG energy. This results in a lower efficiency than when the ir-MCFC with the electric efficiency of 48% is fueled by natural gas (NG). To increase electric efficiency with SNG, it is necessary to recover the exothermic heat generated from the processes of converting coal to SNG as steam, which can then be used in a steam turbine. When steam produced in the gasification, water gas shift (WGS), and methanation processes is used in a steam turbine, the gross electric efficiency will become 41%. If the steam and auxiliary power for CO_2 capture process is consumed more, the net efficiency will be 27%. Use of additional steam from the exhausted gas of fuel cell can increase the total net efficiency to 49%.