Thermo-economic analysis and multi-objective optimization of cryogenic CO2 capture systems based on liquefied natural gas cold energy utilization

Utilizing liquefied natural gas (LNG) cold energy is a novel idea to reduce energy consumption of cryogenic CO2 capture. Two innovative configurations, pre-cooling system and post-expansion system, are introduced and compared with basic system to efficiently and economically harness cold energy. The thermo-economic performance, evaluated from environment, energy and economy perspectives, is thoroughly investigated under a limited LNG flow rate on various design conditions. The thermo-economic performance of three systems in actual operation is optimized by Non-dominant Sorting Genetic Algorithm-II. Results indicate that post-expansion system exhibits the most favorable thermo-economic performance, achieving process simplification, CO2 recovery, exergy efficiency and levelized cost of CO2 capture of 95.64 %, 32.05 % and 82.41 $/tCO2, respectively. Comparison with other technology pathways reveals that cryogenic capture is conducive to cleaner production under similar CO2 concentration levels. The methodology and results will contribute to future academic research and industrial design in the field of cryogenic CO2 capture.