Exergy and economic analysis of a CaO-looping gasifier for IGFC–CCS and IGCC–CCS

• Modeled a CaO–CaCO3 chemical looping gasifier and CO2 regenerator.
• Gasifier was coupled to either a pressurized SOFC or B–R combined cycle.
• Conducted complete exergy and economic analysis of both systems.
• Conducted capital cost estimation of all major equipment in IGCC and IGFC systems.
• Conducted IRR economic analyses of IGCC and IGFC systems with sensitivity analysis.

We present exergy and economic analyses for two potential advanced coal-based power plants with CO2 capture and sequestration. Each system generates three products: electricity, carbon dioxide compressed to 15 MPa, and pre-calcined feedstock for cement kilns. First, we analyzed a system that integrates a CaO-looping gasifier with a solid oxide fuel cell (SOFC), labeled here as IGFC–CCS. The SOFC is modeled based on a commercial pressurized SOFC system. Second, we analyzed a system that integrates a CaO-looping gasifier with a Brayton–Rankine combined cycle, labeled here as IGCC–CCS. The exergy analyses evaluated both the power generation/consumption and the exergy destruction in each of the major sub-systems within the power plant. The economic analyses evaluated the internal rate of return on investment (IRR), including the upfront construction costs and the yearly net revenue. Using recent capital cost estimates, we performed a parametric study of this IGFC–CCS system to determine the effect on the IRR on the four key SOFC parameters: current density, air pressure, fuel utilization, and air stoichiometric ratio. For this IGFC–CCS configuration, the calculated exergetic efficiency was 60% at the parameters values that maximized the IRR. For the IGCC–CCS system with same gasifier specifications, the efficiency was 46%; although, this configuration often achieved a higher value of IRR than the IGFC–CCS configuration, depending on the assumptions made on gas turbine and fuel cell equipment costs. We conducted a sensitivity analysis to determine how the IRR was affected by assumptions, such as capital costs and the sale price of CO2. Most importantly, we analyzed the effect of the coal gasification kinetic rate and CaO capture degradation rate on the IRR so that experimental researchers have goal posts as far as required rates for this CaO-looping process. From our sensitivity analysis, we conclude that the addition of alkali catalysts to CaO-looping gasification process can increase the IRR compared with a CaO-looping process without the addition of alkali catalysts, such as KOH.