Thermodynamic and exergoeconomic evaluation of coal and biomass co-gasification as solid oxide fuel cell feed coupled with supercritical carbon dioxide and organic Rankine cycle

Abstract

Coal-biomass cogeneration technology can not only diversify energy supply, but improve the combustion characteristics of coal and enhance system performance. This work developed a power generation system for co-gasification of coal and biomass to supply solid oxide fuel cell, and coupled with a dual system of supercritical carbon dioxide cycle and organic Rankine cycle to achieve energy cascade utilization. A comprehensive thermodynamic analysis was conducted to evaluate and optimize this system more intuitively. Constrained optimization algorithms elucidated the optimal parameters, identifying an oxygen-to-fuel mass ratio of 0.48 and a steam-to-fuel ratio of 0.18. These conditions led to a higher gasification temperature and optimal syngas yield. And sensitivity analysis on three biomass types confirms that dry and carbon-rich biomass is ideal for system doping. With a 20% doping amount, the system achieves 59.18% maximum thermal efficiency and 2.43 kg/MWh net carbon emission, outperforming the single fuel cell system by 11.14% and 4.79% respectively. The discount rate has the greatest impact on system costs in economic analysis, with a 30% fluctuation causing system costs to vary by about 14.31%. In addition, the exergy and exergoeconomic analyses identify cost formation, propose efficiency measures, and enhance cost-effectiveness.