A Dynamic Model of a Molecular Sieve Bed With Nonlinear and Coupled Isotherms

A mathematical model of the O₂-N₂ separation process in a molecular sieve bed was developed and experimentally verified. Oxygen and nitrogen breakthrough experiments were performed on a single bed packed with molecular sieve 5A. In these experiments, the bed had initially adsorbed either pure oxygen or nitrogen and then a constant inlet flow of nitrogen or oxygen was switched on the bed. The outlet oxygen mole fraction and mass flowrate were then recorded. This was done at several pressures and flowrates. The model predictions agreed with the experimental data when a linear oxygen isotherm and a nonlinear Langmuir isotherm for nitrogen were used and when these were coupled. The numerical scheme presented in this study to solve the system equations makes efficient use of computation time.