Identification of early opportunities for simultaneous H2 separation and CO2 storage using depleted coal seams

•The feasibility of H2 separation from an H2/CO2 mixture in coalbed methane (CBM) is outlined.•Over 90% separated CO2 gas is stored in the coalbed methane reservoir during the separation process.•Multicomponent, multi-phase flow, coal swelling/shrinkage, diffusion, and sorption factors are considered in the simulation model.•Careful consideration of the injected gas composition is crucial due to potential impact of coal swelling. Hydrogen (H2) production by steam methane reforming (SMR) is an economically viable technique on a commercial scale. However, this process produces large amounts of carbon dioxide (CO2), which eventually negates the benefits of employing H2 as an industrial input and clean energy carrier. This issue has led to increasing interest in capturing CO2 emissions from SMR to produce H2. This study proposes and investigates the use of coalbed methane (CBM) resources for separating the mixture of H2 and CO2 gases. The competitive adsorption mechanism in CBM not only can separate the H2 gas from the mixture but also results into the geological storage of CO2 at the same time. The idea is to inject the mixture of H2 and CO2 into a depleted coal seam gas and produce gas from another well offset by a distance. This work studies the proposed idea using a multi-physics simulation model based on the available data in the literature. The model accounts for multicomponent, multi-phase flow, coal swelling/shrinkage, diffusion, and sorption. Several simulations were performed to investigate the feasibility of H2 separation and CO2 storage in CBM. Proof-of-concept simulations showed over 80% H2 separation and over 90% CO2 storage. This result shows that H2 separation and CO2 storage can be performed simultaneously with high efficiency.