CO2 adsorption in a geopolymer-zeolite composite: Experimental dynamic tests and modelling insights on related thermal effects

CO2 adsorption process in a composite geopolymer/zeolite 13X material has been analysed for post combustion carbon capture application, in dynamic conditions for a CO2/N gas mixture. Such composite material represents a valid alternative to conventional sorbents owing to the affinity and synergy between zeolite and the geopolymer binder as well as improved mechanical resistance and lower cost. Experimental analysis has been focused both on complete adsorption tests to determine the material maximum adsorption capacity and on breakthrough tests in transient conditions in (cyclic adsorption/desorption). Particular care has been devoted to thermal effects associated to adsorption and their effect on adsorption capacity and kinetics. Experimental data have been employed to support the development of a novel numerical model, based on Sips adsorption approach for sorbent capacity, and capable to describe the adsorption process, accounting for both mass and energy transport in the sorbent bed. The model proved able to describe well the experimental data at different CO2 feed concentration, and thus it has been employed in a predictive way to inspect process operating parameters and sorbent bed design on the resulting adsorption capacity, breakthrough time, and temperature profile. In particular, the model compared the results obtained in a scaled-up configuration (suitable to an industrial application) with those of the lab-scale system.