Modelling and comparison of calcium looping and chemical solvent scrubbing retrofits for CO₂ capture from coal-fired power plant

Carbon capture and storage (CCS) is expected to provide a cost-effective means of CO₂ emission reduction from the power sector. Amine scrubbing, which is the closest CCS technology to the market, is a suitable option for coal-fired power plants in retrofit scenarios. However, the energy requirement for solvent regeneration in chemical absorption CO₂ capture processes causes a substantial reduction in the power plant efficiency and power output. Therefore, novel technologies with lower efficiency penalties need to be developed. One promising option is calcium looping (CaL) which is based on the reversible carbonation/calcination reaction of calcium-based sorbent that takes place at high temperature. For the purpose of this study, the CaL process was model was developed and then linked to a high-fidelity model of a reference 580MW_el supercritical coal-fired power plant. A secondary steam cycle was also modelled for recovery of high-grade heat from the CaL process. The results of the process analysis revealed that the efficiency penalty imposed in the CaL plant retrofit scenario was 6.7-7.9% points. Such performance compares favourably to the monoethanolamine and chilled ammonia scrubbing retrofit scenarios, which have efficiency penalties of 9.5% and 9.0%, respectively. Moreover, the retrofit of the CaL process was found to be less complex, and would result in two times higher net power output compared to the chemical solvent scrubbing scenarios. This is an important advantage of the CaL plant over the more mature CO₂ capture technologies, especially for the power plant operators who are looking to increase the system capacity to meet the increasing electricity demand and, at the same time, to reduce the CO₂ emissions.