Thermodynamic analysis of an integrated gasification fuel cell-combined cycle power plant using Indian coal

Abstract

In the present study, a detailed thermodynamic analysis of an integrated gasification fuel cell-combined cycle (IGFC-CC) power plant is carried out wherein gasification technology is coupled with solid oxide fuel cell (SOFC) with Brayton and Rankine cycles as bottoming cycles. The proposed power plant is modelled and simulated using a computer flowsheet program called ‘Cycle-Tempo’. The thermodynamic analysis of the cycle with Indian coal as fuel suggests that the steam at higher temperature coming out from the exit of an anode of the SOFC can be used as a potential source for the endothermic gasification reactions in the gasifier. Steam with a flow rate of about 5.43 kg/s extracted from the anode exhaust of SOFC is supplied to the gasifier. The variations of syngas compositions, H2/CO ratios and heating values of syngas with different steam–fuel ratios (SFR) at different gasifier reaction temperatures among three different commercially available gasifiers, viz. fixed bed, fluidized bed and entrained flow gasifiers have been presented in the results. With an increase in SFR, it has been observed that the H2 composition in the syngas increases, whereas the heating value of the syngas decreases. With an increase in SFR from 0.1 to 0.7 at gasifier reaction temperature of 800 °C, H2/CO ratio has increased from 0.613 to 1.707, whereas at 1300 °C, this ratio has increased from 0.46 to 0.95 since lower temperatures favour steam reforming reaction. The net overall plant energy and exergy efficiencies are observed to be maximum in case of entrained flow gasifier with SFR of 0.7 and the values are 46.55% (HHV basis) and 42.65%, respectively. The exergy analysis of the plant indicates that the maximum exergy destruction takes place in the gasifier component with a value of 24.85% suggesting a detailed study for its design optimization.