Comparison of vacuum swing adsorption process for air separation using zeolite 10X and 13X

The five-step two-bed vacuum swing adsorption (VSA) process for air separation was investigated both experimentally and theoretically. The adsorption characteristics and dynamics of the bed packed with zeolite 10X or 13X were compared and the performance of the VSA process with each adsorbent was presented. A non-isothermal dynamic model incorporating mass and energy balances was applied to predict the process dynamics using the linear driving force (LDF) model and the loading ratio correlation (LRC) isotherm. The adsorption amount of N₂ and O₂ on zeolite 13X was higher than that on zeolite 10X while the selectivity of both adsorbents was similar. However, the high bed porosity of zeolite 13X bed had a detrimental effect on the process performance. The step-time of adsorption and pressure equalization steps in the VSA affected significantly the O₂ purity and recovery while that of pressurization step was negligible. In addition, the vacuum pressure during desorption step step proved to be one of the key factors in the process performance. Finally, the VSA using zeolite 10X produced a purity level of 92% O₂ with 70+% recovery while the VSA using zeolite 13X produced a O₂ product with 90% purity and 50+% recovery due to the high bed porosity. However, the productivity of both VSA processes was similar to each other because the net loading of zeolite 13X in the bed was relatively small.