A Simple Combined Dynamic-Equilibrium Model Of Co2 Capture By A Pelleted Zeolite Sorbent

Carbon dioxide (CO2) can be effectively captured from gas mixtures by adsorption on zeolite pellets in fixed-bed columns. In this paper we start from an experimental analysis of CO2 adsorption on a sample of few pellets, to end up with a simulation model for an adsorption column filled with a large number of pellets. The initial experimental analysis is based on dedicated isothermal tests carried out with a gas adsorption analyzer. For the relation between the measured amount of adsorbed CO2 per unit sorbent mass and the input adsorption pressure and temperature, an equilibrium Three-Site Langmuir (TSL) equation is here adopted. Its unknown parameters, namely the saturation capacities, the affinities and the adsorption energies, are estimated by minimizing the error between the equation and the measures. Then, for a whole adsorption column, a simple dynamic model is worked out, based on one-dimensional partial differential equations along the column axial direction: these account basically for mass and energy conservation, for the bulk gas flow and for the porous sorbent. The overall description obtained by combining the TSL equation with the rest of the model is validated against experimental tests, consisting of inlet CO2 molar fraction steps, on a laboratory-scale column. Copyright (C) 2021 The Authors.