A novel approach to simulate ortho-para conversion in hydrogen liquefaction based on the van’t Hoff equation

Liquid hydrogen (LH 2 ) is a promising solution to transport green hydrogen to countries lacking domestic energy resources. One challenge in simulating the liquefaction process is the exothermic ortho-para conversion (OPC). Orthohydrogen is converted to parahydrogen during the process to prevent the liquid hydrogen from evaporating due to the exothermic conversion in the LH 2 tank. This paper introduces a new method to simulate the OPC based on the van’t Hoff equation and provides an analytical expression for the molar heat of conversion. This van’t Hoff approach is assessed by comparing its results to literature data and an existing equilibrium reactor approach. Both approaches are validated against an existing industrial plant. Both methods show good agreement with the literature data with relative errors of 0.5 % and 0.4 %, respectively. After successfully validating both approaches, these methods enable dynamic simulations of hydrogen liquefaction as they can simulate the OPC across the entire temperature range. • New method presented to simulate the ortho-para conversion in hydrogen liquefaction. • Method is based on van’t Hoff equation, named van’t Hoff approach. • Van’t Hoff approach has a relative error of 0.5% compared to literature data. • Equilibrium approach from literature (MBWR equation) has a relative error of 0.4%. • Both methods are successfully validated against the Linde Leuna plant.