Separation of methane-nitrogen mixtures by pressure swing adsorption using a carbon molecular sieve

A 60%-40% and a 92%-8% methane nitrogen mixture were separated in a two-bed pressure swing adsorption (PSA) unit using a carbon molecular sieve (CMS) adsorbent. The CMS adsorbent used in this separation is a dual resistance type comprising a barrier resistance on the crystal surface and diffusion resistance in the crystal interior. This dual resistance is modelled using the linear driving force (LDF) PSA model. The parameter Ω of the LDF model, which relates the theoretical and experimental results, was found to be significantly different from that for conventional diffusion-controlled processes. This difference is attributed to the presence of a barrier resistance in the CMS.