Hydrogen liquefaction process using carbon dioxide as a pre-coolant for carbon capture and utilization

Abstract

With the increasing demand for hydrogen (H2), producing liquefied H2 with a high energy density (10.1 MJ/L) has become essential. Research on the H2 liquefaction process, specifically, the effects of various refrigerants and cooling cycles has been conducted. Yet, large-scale use of carbon dioxide (CO2) in H2 liquefaction hasn't been achieved. In this study, a cooling cycle that uses captured CO2 as a refrigerant in large quantities was selected for a 100 tpd H2 liquefaction process. Optimization minimized the specific energy consumption (SEC), leading to SEC of 7.3 kWh/kgLH2, a coefficient of performance of 0.17, a figure of merit of 0.33, a specific exergy efficiency (SEE) of 33 %, and an overall exergy efficiency of 82.2 %. Performance indicators were compared with other processes, showing that the SEC and SEE were improved by 43 % and 50 % compared to commercial processes and by 4 % and 6 % compared to previous studies using CO2. This study used 5.7 times more CO2 at the same capacity, utilizing 47.8 Mt of CO2, representing 14 % of the CO2 utilization amount of the total carbon capture and utilization (CCU) project. Thus, the results should facilitate the development of hydrogen liquefaction processes for use in CCU applications in the future.