Exergy analysis of a coal/biomass co-hydrogasification based chemical looping power generation system

Power generation from co-utilization of coal and biomass is very attractive since this technology can not only save the coal resource but make sufficient utilization of biomass. In addition, with this concept, net carbon discharge per unit electric power generation can also be sharply reduced. In this work, a coal/biomass co-hydrogasification based chemical looping power generation system is presented and analyzed with the assistance of Aspen Plus. The effects of different operating conditions including the biomass mass fraction, R_b, the hydrogen recycle ratio, R_hr, the hydrogasification pressure, P_hg, the iron to fuel mole ratio, R_if, the reducer temperature, T_re, the oxidizer temperature, T_ox, and the fuel utilization factor, U_f of the SOFC (solid oxide fuel cell) on the system operation results including the energy efficiency, η_e, the total energy efficiency, η_te, the exergy efficiency, η_ex, the total exergy efficiency, η_tex and the carbon capture rate, η_cc, are analyzed. The energy and exergy balances of the whole system are also calculated and the corresponding Sankey diagram and Grassmann diagram are drawn. Under the benchmark condition, exergy efficiencies of different units in the system are calculated. η_te, η_tex and η_cc of the system are also found to be 43.6%, 41.2% and 99.1%, respectively. - Highlights: • A coal/biomass co-hydrogasification based chemical looping power generation system is setup. • Sankey and Grassmann diagrams are presented based on the energy and exergy balance calculations. • Sensitivity analysis is done to understand the system operation characteristics. • Total energy and exergy efficiencies of this system can be 43.6% and 41.2%, respectively. • About 99.1% of the carbon contained in coal and biomass can be captured in this system.