Thermodynamic and economic investigation of a novel combined cycle in coal-fired power plant with CO2 capture via Ca-looping

Abstract

CO2 capture from coal-fired power plants (CFPP) with low cost is crucial for China to achieve carbon peaks in 2030. The manuscript proposes a novel combined cycle of supercritical CO2 Brayton cycle (SCBC) and organic Rankine cycle (ORC) in CFPP with CO2 capture. The novelty of the proposed scheme lies on its high-level thermal integration which can efficiently complete the conversion of heat to electricity, waste heat recovery, and CO2 capture. Exergy analysis and levelized cost of electricity (LCOE) are employed to respectively evaluate the thermodynamic and economic performance. The simulation results show that the exergy efficiency of the combined cycle is 39.74% as considering CO2 capture, resulting in a 3.41% of efficiency penalty. The introduction of ORC improves the exergy efficiency by 1.05%. The LCOE of the combined cycle is 79.03$/MWh, almost 19.3$/MWh (32.29%) more expensive than the base plant, and the costs of CO2 captured and avoided are respectively 21.81$/tCO2 and 26.25$/tCO2. The results indicate that the proposed combined cycle has the potential to compete with other carbon capture technologies from the views of exergy efficiency and cost. Coal combustion in the S–CO2 boiler and the calciner is responsible for the maximum internal exergy destructions, and increasing the cycle maximum temperature may reduce the exergy destruction. The largest cost contributor to LCOE is associated with capital expenditures (41.55%), and the cost reduction efforts should be aimed at capital expenditures.