The effects of a readily adsorbed trace component (water) in a bulk separation PSA process: The case of oxygen VSA

This paper investigates the thermal profiles that arise in oxygen VSA, whic h is a prominent example of a PSA bulk gas separation process. Experimental ly, it is demonstrated that the severe axial thermal profile or "cold spot" that frequently characterizes oxygen VSA can only arise if there are multi layered adsorption beds or if there are readily adsorbed trace components ( such as water) that create a de facto multilayered bed. A qualitative expla nation is offered to explain how this cold spot is formed. This paper also details a technique for predicting the penetration of a water-loaded zone i nto an oxygen VSA adsorption bed based on the method of characteristics. Th e results of this technique compare well with experimental and numerically simulated results. Finally, this paper demonstrates that a water-loaded zon e and an inert zone of activated alumina result in very similar cyclic stea dy-state thermal profiles, even though the transient behaviors are markedly different.