Speaker
Description
The purity of recovered hydrogen from geological storage is controlled by persistent interactions between the injected hydrogen and the cushion gas. Here, we present the first thermodynamic analysis of hydrogen-cushion gas interactions under reservoir conditions. By quantifying changes in Helmholtz free energy associated with mixing, we show that hydrogen recovery purity depends on the combined effects of the thermodynamic driving force for mixing and the molar density contrast between hydrogen and cushion gas. This thermodynamic framework consistently explains numerical predictions based on experimentally measured diffusion coefficients. Among the representative cushion gasses examined, nitrogen and methane exhibit similar behavior and yield higher hydrogen purity than carbon dioxide, although the differences diminish with increasing depth. This indicates that field-scale storage performance is fundamentally governed by intrinsic thermodynamic tendencies.
| Country | China |
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