Kinetic separation by pressure swing adsorption: Method of characteristics model

A theoretical model using the method of characteristics is presented for a Skarstrom‐type pressure swing adsorption (PSA) cycle using carbon molecular sieve for the kinetic separation of nitrogen/methane mixtures. Good agreement with experimental results was obtained. The solution of the reduced nonlinear ordinary differential equations along characteristics, a variable computational grid from the changing bed velocity, and a constant product flow boundary condition are complications that prohibited using the method of characteristics in favor of finite difference or orthogonal collocation methods. These complications have been overcome in the present study to develop a theoretical model, incorporating nonlinear isotherms and a linear driving force rate for diffusion, which requires less computer time and is particularly amenable for studying transient bed dynamics. The effects of feed pressure and concentration, half‐cycle time, and product flow rate on kinetic PSA performance are also illustrated.