Modeling of nitrogen separation from natural gas through nanoporous carbon membranes

This work presents a theoretical investigation of the use of nanoporous carbon membranes for the separation of nitrogen from natural gas. A mathematical model to predict the performance of the membrane is developed. The model is a combination of the well known dusty gas model, which describes the transfer of multi-components mixture in porous media, together with a surface diffusion model. The model is first validated using the literature results for the separation of hydrogen from hydrocarbons mixture. The model is then applied to the nitrogen-hydrocarbons system. The membrane performance is evaluated in terms of nitrogen recovery, methane loss, nitrogen purity, as well as hydrocarbons compositions in both permeate and retentate sides. The model calculation methods are applied for both co-current and counter-current flow configurations. A parametric study is also carried out to investigate the effects of membrane parameters such as feed and permeate pressures and porosity on the membrane performance. The developed model is general and can be applied to various nanoporous membrane flow patterns.