Cushion Gas Selection for Hydrogen Storage in a Lined Rock Cavern: A Feasibility Study Using Maxwell–Stefan Equations

The selection of cushion gas type for hydrogen storage in lined rock cavern (LRC) is very important. Accordingly, a multicomponent gas diffusion model for LRC hydrogen storage is developed based on the Maxwell–Stefan diffusion equation and the mass, momentum, and energy conservation equations, while accounting for the real gas compressibility of gas. The COMSOL Multiphysics software is used to calculate the spatial distribution of the mixed gases during cyclic injection and production. The feasibility of various gases as cushion gas for hydrogen storage is analyzed. The results show that argon as a cushion gas yields higher hydrogen purity and recovery rates, with the recovery rates reaching 97.6%, compared with nitrogen and methane. The longer the storage time, the lower the recovery rate of hydrogen. Increasing the recovery rate will increase the recovery rate of hydrogen. However, increasing the recovery rate will reduce the purity of hydrogen.