Measurement of competitive CO2 and N2 adsorption on Zeolite 13X for post-combustion CO2 capture

Single component CO2 and N-2 equilibrium loadings were measured on Zeochem Zeolite 13X from 0 to 150 degrees C and 0-5bar using volumetry and gravimetry. CO2 equilibrium data was fit to a dual-site Langmuir (DSL) isotherm. The equilibrium data for N-2 was fit using four isotherm schemes: two single site Langmuir isotherms,the DSL with the equal energy sites and the DSL with unequal energy site pairings. A series of single and multicomponent CO2 and N-2 dynamic column breakthrough (DCB) experiments were measured on Zeolite 13X at 22 degrees C and 0.98bar. The adsorption breakthrough experiments were able to provide accurate data for CO2 competitive adsorption, while failing to provide reliable N-2 data. It was shown that desorption experiments from a bed fully saturated with the desired composition provides a better estimate of the competitive N-2 loading. A detailed mathematical model that used inputs from the batch equilibrium experiments was able to predict the composition and thermal breakthrough curves well while underpredicting the single component N-2 loading. The DSL isotherm with unequal energy sites was shown to predict the competitive loading and breakthrough curves well. The impact of the chosen adsorption isotherm model on process performance was evaluated by simulating a 4-step vacuum swing adsorption process to concentrate CO2 from dry post-combustion flue gas. The results show that the purity, recovery, energy and productivity are affected by the choice of the competitive adsorption isotherm.