Hydrogen separation from hydrogen-compressed natural gas blends through successive hydrate formations

Abstract

With hydrogen gaining prominence as a future decarbonization tool, the practice of "Hydrogen Blending" - the integration of hydrogen into natural gas pipelines - has swiftly emerged to curb carbon emissions. However, before hydrogen pipelines become widespread, in-depth research into "Hydrogen Deblending" - the separation of hydrogen from HCNG (Hydrogen-Compressed Natural Gas) - is essential to ensure the availability of pure hydrogen when required. In this context, our study introduces an innovative gas separation technique based on clathrate hydrates. Clathrate hydrates are crystalline inclusion compounds in which guest molecules are accommodated within the cage of water-framework constructed by hydrogen bonding. The water-based nature of clathrate hydrates enables a scalable and sustainable process for gas storage and separation. We propose an innovative gas separation system that utilizes successive hydrate formations to store natural gas within hydrates, while enhancing the purity of hydrogen in the vapor phase. Employing in-situ gas chromatography, we analyzed gas compositions at stage 1 of hydrate formation and quantified gas storage capacities (mmol/mol of water) for individual guest species. Our study confirmed that the designed successive hydrate formation could achieve around 79.32% of hydrogen recovery with a purity of 98.73%, demonstrating the viability of hydrate-based separation process.