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 Omega 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.