Simulation and Optimization of Mixed Refrigerant Hydrogen Liquefaction Process

Abstract

Hydrogen liquefaction is critical for enabling long-distance transport and storage of hydrogen, a key enabler of the global energy transition. However, its high energy demand, with conventional mixed refrigerant cycles consuming 10–13.58 kWh/kg of liquid hydrogen (LH₂), poses significant challenges. This study presents an optimized hydrogen liquefaction process modeled in Aspen HYSYS V11 and enhanced using the Teaching-Learning-Based Optimization (TLBO) algorithm in MATLAB. The proposed process employs a three-stage refrigeration cycle (precooling, cooling, and liquefaction) with tailored mixed refrigerants (methane, ethane, propane, nitrogen, helium, and hydrogen) to minimize exergy losses and improve thermodynamic efficiency while converting the hydrogen from ortho-para during the process. Optimization results yield a specific energy consumption (SEC) of 7.37 kWh/kg LH₂, a 25–30% reduction compared to conventional Claude- based cycles (10–13 kWh/kg), alongside an exergy efficiency of 65.32%, nearly double that of base case defined in comparison to this study i.e. 34%. Cost analysis at 1 ton per day (TPD) capacity estimates a unit liquefaction cost of 3.86 $/kg, with compressors contributing 90% of equipment costs. These findings demonstrate the potential of the proposed process to enhance the energy and economic viability of hydrogen liquefaction, supporting its role in sustainable energy systems. Future work integrating renewable energy sources could further reduce SEC and operational costs.