A Dynamic Model of CO2 Adsorption by Zeolite 13X Pellets

Novel techniques to capture carbon dioxide (CO2) from gas mixtures include physical adsorption on pelleted solid substrates. In this paper, the behaviour of spherical zeolite pellets is modelled, by resorting to one-dimensional partial differential equations, along the pellet radial direction, to express CO2 mass and energy conservation inside the porous material. One of the innovative contributions is that a dynamic description is adopted also for adsorption/desorption kinetics. The uncertain parameters in the model can be identified with a two-step procedure thanks to real data collected in two different sets of experiments. First, static isothermal tests carried out on few pellets by means of a gas adsorption analyzer allow to identify the available sorbent active sites (saturation capacities) and the ratio of the desorption and adsorption kinetic coefficients. Then, dynamic tests carried out with the same analyzer with small progressive CO2 injections allow to estimate desorption and adsorption kinetic coefficients separately. The pellet dynamic model thus tuned can be adopted in future work as a core element to mathematically describe a whole adsorption column filled with many pellets.