(49f) Analysis of Concentration Swing (Magnitude of Concentration Change during a Cycle) in Pressure Swing Adsorption

Pressure swing adsorption is a time-dependent cyclic process. Although the average product concentration is primarily important information, the concentration swing, i.e. magnitude of concentration change during a cycle, is another important index of performance. The present author analyzed the latter topic by a “short cycle time approximation” in an old paper [1] and gave the result in a closed analytical form in case of a linear isotherm of adsorption. The same approach was extended to the case of a non-linear isotherm [2] and the result was given in terms of a first-degree linear differential equation with variable coefficients with respect to the average concentration. In this presentation, a concept of HETP (height equivalent to a theoretical plate) [3] is applied to evaluate the integrating factor involved in the original linear differential equation. The final result of the concentration swing in a non-linear isotherm case is expressed in terms of a summation of the corresponding result of linear isotherm weighted by the average gradient of the isotherm over each theoretical plate. The present closed form result is discussed in comparison with more rigorous numerical simulation and experimental results for dehumidification and CO2 removal.

[1] T.Hirose, T.Minoda, J. of Chem. Eng. Japan, 19, 300(1986)

[2] T.Hirose, J. of Chem. Eng. Japan, 20, 270(1987)

[3] T.Hirose, M.Yoshida, A.Kodama, M.Goto, Fundamentals of Adsorption, 7, 724(2002)