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Analysis of Vapour-Liquid Equilibrium Behaviour of Cryogenic Hydrogen-Deuterium Mixtures Using Cubic Equation of State-based Method

Rupsha Bhattacharyya


A comparative analysis of the vapour liquid equilibrium behaviour of the cryogenic hydrogen-deuterium system calculated under the assumption of an ideal solution using pure component vapour pressure data versus that of a real solution using Peng-Robinson cubic equation of state has been presented in this work. It is found that assumption of ideal solution leads to over prediction of the relative volatilities by 14% to 57% depending on the mixture composition and pressure. The variation in predicted performance of a single stage cryogenic flash chamber for separating a hydrogen-deuterium mixture when estimated using ideal and real solution characteristics has also been studied using a form of the Rachford-Rice algorithm and variations of 33% to 1759% have been calculated. The method has been implemented through codes developed in-house and it can be extended to multi-component hydrogen isotope mixtures (or any other mixtures described adequately by cubic equations of state) likely to be encountered in fusion energy systems or other isotopic separation methods based on the formation of vapour-liquid phases. Assumption of real solutions is expected to provide more accurate performance assessment of separation systems since at the very low temperatures required for cryogenic hydrogen systems, the vapour phase in particular will deviate greatly from ideal mixture characteristics.

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