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

Abstract

Single component CO2 and N2 equilibrium loadings were measured on Zeochem Zeolite 13X from 0 to 150 °C and 0–5 bar using volumetry and gravimetry. CO2 equilibrium data was fit to a dual-site Langmuir (DSL) isotherm. The equilibrium data for N2 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 N2 dynamic column breakthrough (DCB) experiments were measured on Zeolite 13X at 22 °C and 0.98 bar. The adsorption breakthrough experiments were able to provide accurate data for CO2 competitive adsorption, while failing to provide reliable N2 data. It was shown that desorption experiments from a bed fully saturated with the desired composition provides a better estimate of the competitive N2 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 N2 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.