Temperature Swing Adsorption for the Recovery of the Heavy Component: An Equilibrium-Based Shortcut Model

Abstract

Temperature swing adsorption (TSA) processes are considered as an interesting option for the capture of CO2 from flue gases. In this work, a shortcut model is developed for a four step cycle aimed at recovering the more retained component at high purity from a binary mixture, e.g. CO2 from CO2/N2. The model equations, which assume local adsorption equilibrium but take into account heat transfer kinetics, enable a direct semianalytical solution of the cyclic steady state. For fixed temperatures of the indirect heating and cooling fluid, interstitial velocity, and feed composition, the remaining operating conditions can be reduced to the high and low temperature levels achieved during the cycle, which control the thermodynamic states defining the effective cyclic capacity. This model is used to investigate the CO2/N2 separation by TSA on a commercial zeolitic adsorbent. Important trends are revealed by performing a parametric analysis of the operating conditions on the relevant quantities, that is, purity, recovery, specific thermal energy consumption, and productivity. Optimal operating conditions are localized within the region of feasible operating conditions and a trade-off between productivity and specific energy consumption is presented and discussed. Besides providing insight into TSA processes for the recovery of the heavy component, this tool could be used for rapid yet robust sorbent screening.