Hydrogen re-liquefaction Process for Boil-off Gas Handling on a Large-scale Liquid Hydrogen Carrier

Abstract

With the recent focus on hydrogen, seaborne shipping is considered an option for the large-scale transport of liquid hydrogen (LH2). For efficient shipping, boil-off gas (BOG) from the cargo tanks needs to be optimally utilized. This work suggests a BOG handling system (BHS) producing fuel for an LH2 carrier and liquefying excess BOG in a hydrogen Claude cycle. The process offers a simple configuration that does not require a refrigerant makeup facility. The simulation results of the BHS also show relatively low specific power consumption (5.7 to 2.6 kWh/kgLH2) with a good utilisation of cold energy in BOG. The sensitivity analysis with the BOG to fuel (BtF) ratio shows that a higher BtF gives a simpler configuration and a smaller size liquefier, saving capital costs. However, the optimal capacity of the BHS needs to be determined based on the techno-economic performance of the entire system of the LH2 carrier. Keywords: Hydrogen, Liquefaction, Liquid hydrogen carrier, Transport, Boil-off gas, Claude cycle