This study proposes a CO2 re-liquefaction system utilizing the cold energy of LNG and liquid hydrogen (LH2) to efficiently manage boil-off gas in alternative fuel-based CO2 carriers. Process simulations using Aspen HYSYS V11 under 100% and 70% propulsion loads evaluated the Specific Energy Consumption (SEC), Coefficient of Performance (COP), UA of heat exchangers, and Specific Life Cycle Cost (SLCC). The results demonstrate that under both 100% and 70% propulsion load conditions, the utilization of cold energy decreases the SEC by 24.5% and improves the COP by approximately 34% compared to the reference model without cold energy utilization. Sensitivity analysis on the minimum temperature approach indicates limited impact on performance. The UA of the heat exchangers decreased by up to 83% (LNG) and 87% (LH2), offering significant downsizing advantages. Economically, SLCC was reduced by up to 14.8% and 15.9% for the LNG and H2 models, respectively, due to lower Capital Expenditure (CAPEX) and Operating Expenditure (OPEX). Consequently, this study demonstrates that exploiting the cold energy of alternative fuels significantly improves both the thermodynamic performance and economic feasibility of CO2 re-liquefaction systems, providing foundational data for future optimization.
Park et al. (Mon,) studied this question.