A novel Ca-Ni looping with carbonation heat thermochemical regeneration method for post-combustion CO2 capture: System integration, energy-saving mechanism, and performance sensitivity analysis

Thermal coupling between the calcium looping (CaL) process and chemical looping combustion (CaL-CLC) offers advantages to avoid electricity consumption of air separation, and the CaL-CLC has presented superior performance realizing CO2 capture. However, in these CaL-CLC and CaL configurations for post-combustion CO2 capture, the carbonation heat is recovered for steam generation with a significant temperature difference, leading to considerable irreversible loss. To prevent the temperature mismatch during carbonation heat recovery, this paper proposes the concept of Ca-Ni looping with the carbonation heat thermochemical regeneration method. Additionally, a novel system integrating with a combined cycle is introduced to effectively decarbonize flue gas. Results show that the proposed system has superior performance compared with the reference system based on the Ca-Cu looping method. The specific energy consumption for CO2 avoided (SPECCA) decreased from 2.13 MJ/kg CO2 in the reference system to 1.43 MJ/kg CO2. Exergy analysis indicates that a total 6.3 % exergy destruction reduction is realized by replacing the Cu-based chemical looping combustion with the Ni-based oxidation reaction for calcination heat supply. Furthermore, the energy utilization diagram (EUD) reveals the mechanism of exergy destruction reduction caused by the thermal coupling between reaction processes. Besides, the impact of key operating parameters on the proposed system performance is investigated. Overall, the proposed Ca-Ni looping with carbonation heat regeneration method enhances the utilization of mid-temperature carbonation heat by converting it into high-grade thermal energy suitable for combined cycles, thereby offering a promising alternative for low-energy-consumption CO2 capture.