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International Scholarly Research Network ISRN Chemical Engineering Volume 2012, Article ID 982934, 13 pages doi:10.5402/2012/982934 Review Article Advances in Pressure Swing Adsorption for Gas Separation Carlos A. Grande Department of Process Chemistry, SINTEF Materials and Chemistry, P.O. Box 124, Blindern, 0314 Oslo, Norway Correspondence should be addressed to Carlos A. Grande, carlos.grande@sintef.no Received 25 September 2012; Accepted 18 October 2012 Academic Editors: T. M. Aminabhavi, D. Cazorla-Amoros, and X. Feng Copyright © 2012 Carlos A. Grande. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Pressure swing adsorption (PSA) is a well-established gas separation technique in air separation, gas drying, and hydrogen purification separation. Recently, PSA technology has been applied in other areas like methane purification from natural and biogas and has a tremendous potential to expand its utilization. It is known that the adsorbent material employed in a PSA process is extremely important in defining its properties, but it has also been demonstrated that process engineering can improve the performance of PSA units significantly. This paper aims to provide an overview of the fundamentals of PSA process while focusing specifically on different innovative engineering approaches that contributed to continuous improvement of PSA performance. 1. Introduction Adsorption is the name of the spontaneous phenomenon of attraction that a molecule from a fluid phase experi- ences when it is close to the surface of a solid, named adsorbent. There are several pristine works that explain this phenomenon in detail [1–18]. Adsorbents are porous solids, preferably having a large surface area per unit mass. Since different molecules have different interactions with the surface of the adsorbent, it is eventually possible to separate them. When the adsorbent is put in contact with a fluid phase, an equilibrium state is achieved after a certain time. This equilibrium establishes the thermodynamic limit of the adsorbent loading for a given fluid phase composition, tem- perature, and pressure [3]. Information about the adsorption equilibrium of the different species is vital to design and model adsorption processes [19–27]. The time required to achieve the equilibrium state may be also important, particularly when the size of the pores of the adsorbent are close to the size of the molecules to be separated [28–43]. In an adsorption process, the adsorbent used is normally shaped into spherical pellets or extruded. Alternatively, it can be shaped into honeycomb monolithic structures resulting in reduced pressure drop of the system [44–54]. The feed stream is put into contact with the adsorbent that is normally packed in fixed beds. The less adsorbed (light) component will break through the column faster than the other(s). In order to achieve separation, before the other (heavy) component(s) breaks through the column, the feed should be stopped and the adsorbent should be regenerated by desorb- ing the heavy compound. Since the adsorption equilibrium is given by specific operating conditions (composition, T and P), by changing one of these process parameters it is possible to regenerate the adsorbent. When the regeneration of the adsorbent is performed by reducing the total pressure of the system, the process is termed pressure swing adsorption (PSA), the total pressure of the system “swings” between high pressure in feed and low pressure in regeneration [55, 56]. The concept was patented in 1932, but its first application was presented thirty years later [57]. Over the years it has been demonstrated that PSA technology can be used in a large variety of applications: hydrogen purification [58–72], air separation [57, 73– 80], OBOGS (on-board gas generation system) [81], CO2 removal [82–84], noble gases (He, Xe, Ar) purification [85– 87], CH4 upgrading [31, 34, 37, 40, 42, 88–96], n-iso paraffin separation [5, 97–99], and so forth. The PSA processes are normally associated to low energy consumption when compared to other technologies [12, 55, 100–102]. As a rule of thumb, pressure swing adsorption is preferred to other processes when the concentration of the components to be removed is quite important (more than a few per cent). In such conditions, loading the column withPDF Image | Advances in Pressure Swing Adsorption for Gas Separation
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