Modeling and Simulation of Pressure Equalization Step Between a Packed Bed and an Empty Tank in Pressure Swing Adsorption Cycles

Abstract

Background:It is of paramount importance to pay a great attention when modeling pressure equalization step of pressure swing adsorption cycles for its notable effect on the accurate prediction of the whole cycle performances. Studies devoted to pressure equalization between an adsorption bed and a tank have been lacking in the literature. Many factors could affect the accuracy of the dynamic simulation of pressure equalization between a bed and an empty tank. Methods:The method used for the equilibrium pressure evaluation has a significant impact on simulation results. The exact equilibrium pressure (P eq ) obtained when connecting an adsorption column and an empty tank could only be obtained by numerical simulation given the complexity of the set of partial differential equations. Results:It has been shown that, with some simplifying assumptions, one can analytically determine Peq with satisfactory precision. The analytical solution proposed permits to assess rapidly the equilibrium pressure and the equilibrium mole fraction of the adsorbable species in the tank (Y eq ) and without the need to resort to a cubersome modeling. Conclusion:Based on the comparisons presented, one can conclude that the agreement between the experimental and numerical results relative to P eq and Y eq is very satisfactory.

Equilibrium Theory Analysis of Pressure Equalization Steps in Pressure Swing Adsorption

“…Nevertheless, the trends predicted from this equilibrium theory analysis in Figures 4−7 are considered to be qualitatively correct. To quantify these intriguing trends, rigorous numerical analyses must be done, as recently inferred by Chahbani et al 19…”

“…Of the literally thousands of publications and patents on PSA processes, only a paucity considers the use of a tank as a temporary gas storage medium between two beds undergoing a pressure equalization step, with nearly all of them being in the patent literature. − Ebner et al provided perhaps the first review of this literature, with several new references cited herein. ,,,,,,, Of this PSA process literature that mentions utilizing one or more pressure equalization tanks, only the works of Zhou et al and Chahbani et al carried out mathematical analyses of such use and only the works of Ebner et al and Ebner et al carried out graphical analyses of such use.…”

“…3−20 Ebner et al 20 provided perhaps the first review of this literature, with several new references cited herein. 3,5,8,9,12,14,18,19 Of this PSA process literature that mentions utilizing one or more pressure equalization tanks, only the works of Zhou et al 16 and Chahbani et al 19 carried out mathematical analyses of such use and only the works of Ebner et al 2 and Ebner et al 20 carried out graphical analyses of such use.…”

“…Experimentally, with tank volume to adsorption bed volume ratios of 3 and 1.5, they showed that a larger ratio resulted in a higher light product recovery with little effect on the light product purity. Chahbani et al 19 developed a numerical model that describes the pressure equalization down step between an adsorption bed and an empty tank of equal volumes. They also derived analytic expressions that predict the final pressure for the equalization down step between the adsorption bed and the empty tank.…”

Evaluation of simplified pressure swing adsorption cycles for bio-methane production

“…An alternative to improve the PSA recovery and keep the process continuity is to use a tank to receive and provide pressure equalization (Chahbani et al 2017;Krishnamurthy et al 1989;Santos et al 2011). The "equalization tank" can also be used to provide a purge flow with the intention of improve the recovery of PSA process (Krishnamurthy et al 1989).…”