CO 2 liquefaction is an essential process for long-distance ship transportation. The conventional CO 2 liquefaction process employs either an external coolant or liquid expansion followed by multistage compression to obtain liquefied CO 2 at low pressure. However, these processes consume considerable amounts of energy, which presents an obstacle to commercialization. Thus, the CO 2 liquefaction process needs to be carefully researched and designed to reduce the operating energy. In this study, two alternative CO 2 liquefaction processes are proposed and evaluated. These alternative processes use multistage expansion and multistream heat exchangers to lower the input stream temperature for the compressor. In addition, the system is operated in a more efficient manner by operating the process with an optimized compression ratio. Evaluation of the economic feasibility was performed in this study for a complete assessment of the alternative processes. As a result, about 98.1 kWh/t of CO 2 was consumed for alternative process 2, which is only 91.8% of the total operating energy of existing CO 2 liquefaction processes, and the CO 2 liquefaction costs for alternative process 2 were reduced by 5.5%.
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