Thermodynamic performance assessment and comparison of IGCC with solid cycling process for CO2 capture at high and medium temperatures

Solid sorbents can be used to capture CO₂ from pre-combustion sources at various temperatures. MgO and CaO are typical medium- and high-temperature CO₂ sorbents. However, pure MgO is not active toward CO₂. The addition of Na₂CO₃ increases the operating temperature and significantly increases the reactivity of sorbents to capture CO₂. Na₂CO₃-promoted MgO is a promising medium-temperature CO₂ sorbent. In this study, the thermodynamic performance of integrated gasification combined cycle (IGCC) systems with Na₂CO₃–MgO-based warm gas decarbonation (WGDC) and CaO-based hot gas decarbonation (HGDC) is evaluated and compared with that of an IGCC system with methyldiethanolamine (MDEA)-based cold gas decarbonation (CGDC). Assuming that the average CO₂ capture capacities of solid sorbents are one-third of their theoretical maxima, we reveal that the IGCC system undergoes approximately 2.8% and 3.6% improvement on net efficiency when switching from CGDC to WGDC and to HGDC, respectively. The net efficiency of the system is increased by improving the CO₂ capture capacity of the sorbent. The IGCC with Na₂CO₃–MgO experiences more significant increase in efficiency than that with CaO along with the improvement of sorbent average CO₂ capture capacity. The efficiency of the IGCC systems reaches the same value when the average CO₂ capture capacities of both sorbents are 53% of their theoretical levels. The effects of gas turbine combustor fuel gas inlet temperature on IGCC system performance are analyzed. Results show that the efficiency of the IGCC systems with HGDC and WGDC increases by 0.74% and 0.53% respectively as the fuel gas inlet temperature increases from 250 °C to 650 °C.