A novel hydrogen liquefaction process using dual mixed cryogenic refrigeration system: Energy, exergy, and economic analysis

Abstract

In conventional hydrogen liquefaction plants, the liquefaction process consumes high portion of about 30 % of the liquid hydrogen (LH2) energy content. In addition, existing LH2 technology uses pure or single mixed refrigerants, which are susceptible to freezing problems. To address these challenges, this study introduces an innovative hydrogen liquefaction process utilizing dual mixed refrigeration (DMR) system. This process incorporates two interactive mixed refrigerants in two integrated refrigeration loops, offering flexible capability to handle large-scale capacities with minimal energy consumption and free of freezing problems. The proposed process achieved extremely low specific energy consumption (SEC) of 3.732 kWh/kgLH2, 48 % lower than the average SEC of the large-scale single mixed refrigerant (SMR) systems (7.128 kWh/kgLH2). Also, its exergy efficiency (59.65 %) is 33 % higher than the average exergy efficiency of the SMR-based systems (44.89 %). Furthermore, the proposed DMR-based process reduces the levelized cost of liquid hydrogen production to 1.89 $/kgLH2, which is 70 % lower than the small-scale processes and 21 % lower than the average cost of the large-scale SMR-based systems. This study of the dual mixed cryogenic refrigeration approach provides new methodology and guidelines for future research to significantly improve the technical and economic feasibility of LH2 production, making it competitive with other energy storage and transportation options.