On thermodynamic separation efficiency: Adsorption processes.

A simplified thermodynamic analysis of adsorption processes in temperature swing adsorption (TSA) and pressure swing adsorption (PSA) modes as a function of adsorbate concentration and the adsorbent-adsorbate interaction strength is presented in this article. The thermodynamic separation efficiency of a TSA process is optimal at dilute feed conditions, and becomes more thermodynamically efficient with increasing adsorbate affinity even though the energy of separation increases. The adsorption process is spontaneous, and for a strong isotherm, the energy required to reverse the adsorption is nearly independent of the adsorbate concentration as adsorbate loading in nearly-saturated materials is essentially constant with feed concentration. PSA units are efficient thermodynamically and the efficiency increases with the concentration of the desired adsorbate. This thermodynamic treatment has implications for separation processes that address carbon emissions. TSA systems operate more efficiently (thermodynamically) in the 'air capture' case because they apply work to the concentrated product rather than the dilute feed. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3699-3705, 2016 [ABSTRACT FROM AUTHOR]