4E analysis of the cryogenic CO2 separation process integrated with waste heat recovery

Carbon dioxide capture, utilization, and storage (CCUS) is an attractive method to reduce carbon dioxide (CO2) emissions originating from fossil fuels burned from large single-point sources. CO2 separation from a CO2-laden gas stream is the first stage of CCUS. In this investigation, a cryogenic distillation-based CO2 separation process (CCSP) is developed. CCSP is modified to utilize waste heat obtained in the process for reducing the energy consumption of CO2 separation. Two modifications are carried out in the process which include (i) heat integration (HI) with CCSP (CCSP + HI) of the reboiler with the heat from hot streams available in the process and further, (ii) energy recovery by using the organic Rankine cycle (ORC) operating between gas compressor temperature and ambient temperature (CCSP + HI + ORC). The parametric and 4 E (energy, exergy, economic, and environmental) analysis results obtained for the CCSP + HI, CCSP + ORC, and CCSP + HI + ORC processes are compared with those of CCSP. The net electrical energy required to operate the compressor for CCSP is 2.7%, 7%, and 21.8% higher than that for CCSP + HI, CCSP + ORC, and CCSP + HI + ORC, respectively.