Energy-Efficient Hydrogen Liquefaction Process with Ortho-Para Conversion and Boil-Off Gas Recovery

Abstract

Hydrogen liquefaction is essential for the efficient storage and transportation of hydrogen. In the liquefaction process, catalytic ortho-para conversion is crucial to achieve a product with at least 95 % para-hydrogen to reduce boil-off losses. The proposed hydrogen liquefaction process using a catalyst-filled heat exchanger for continuous ortho-para conversion is modeled through steady-state thermal simulations in Aspen HYSYS. Additionally, an ejector is integrated to reliquefy boil-off gas. The proposed design achieves a specific energy consumption (SEC) of 10.50 kWh ($$)⁻¹ and an exergy efficiency (EXE) of 30.1 %, which is 18 % lower in SEC compared to processes with separate converters. The integrated approach enhances energy utilization and offers references for future hydrogen liquefiers.