Adsorption and Desorption Characteristics of Air on Zeolite 5A, 10X, and 13X Fixed Beds

Abstract

Adsorption and desorption experiments for the binary mixture (N2/O2; 79:21 vol%) on zeolite 5A, 10X, and 13X beds were performed to study the dynamic characteristics of air separation adsorption processes. Because the breakthrough and desorption curves showed a tail by temperature variance in the beds, a nonisothermal dynamic model incorporating mass and energy balances was applied to the simulation of adsorption dynamics using the Langmuir–Freundlich model and the LDF approximation. The breakthrough and desorption results were compared among three different beds with respect to the breakthrough and desorption times, tailing effect, and temperature variation with the effects of pressure and flow rate. On the basis of the similar bed density, the order of breakthrough time and desorption time was zeolite 10X, 13X, and 5A beds. Also, the O2 MTZ of the zeolite 10X bed was slightly sharper than those of the zeolite 5A and 13X beds due to more favorable N2 isotherm of zeolite 10X. Furthermore, the breakthrough curve of the zeolite 13X bed showed a relatively long tail. In addition, the breakthrough curves of the zeolite 5A and 13X were similar to adiabatic behavior, whereas that of the zeolite 10X bed showed an isothermal behavior. The N2 desorption experiments were performed by O2 purge under the high pressure conditions. The desorption behaviors were very similar to the results of the breakthrough study, while the thermal effect on the desorption curve was negligible at the beds. The tails of the desorption curves were prominent with a change in the purge flow rate and desorption pressure. In all the beds, the feed and purge rates were more important factors for deciding the breakthrough and desorption times than the adsorption and desorption pressures in the experimental range.