(347j) Measurement of Competitive CO2, H2o and N2 Adsorption on Zeolite 13X for Post-Combustion CO2 Capture

Single component CO₂ and N₂ equilibrium loadings were measured on Zeochem zeolite 13X from 0 to 150⁰C and 1 mbar to 5 bar using volumetry and gravimetry [1, 2]. H₂O equilibrium data was collected from 22 to 100⁰C and 1 to 21 mbar using thermogravimetric analysis. A series of single and multicomponent CO₂, H₂O and N₂ dynamic column breakthrough (DCB) experiments were measured on zeolite 13X at 22⁰C and 0.98 bar. The adsorption breakthrough experiments were able to provide accurate equilibrium data for the heavy component (CO₂ in CO₂/N₂ mixtures and H₂O in H₂O/CO₂/N₂ mixtures), while failing to provide reliable light component (N₂ in H₂O/CO₂/N₂ mixtures and CO₂ in H₂O/CO₂ mixtures) data. It was shown that desorption experiments from a bed fully saturated with the desired composition provides the best estimate of the competitive light component loading. H₂O and CO₂ equilibrium data was fit to a dual-site Langmuir (DSL) isotherm. The equilibrium data for N₂ was fit using four DSL isotherm schemes: the perfect positive, the perfect negative, the equal energy site and the unequal energy site pairings. A detailed mathematical model that used input from the batch equilibrium experiments was able to predict the composition and thermal breakthrough curves well. The dual-site Langmuir isotherm with unequal energy sites was shown to predict the competitive loading and breakthrough curves well for CO₂ and N₂. The impact of the chosen adsorption isotherm model on process performance was evaluated by optimizing a 4-step vacuum swing adsorption process to concentrate CO₂ from dry post-combustion flue gas. The results show that the energy and the productivity are significantly affected by the choice of the adsorption isotherm proving the need to measure competitive adsorption data for reliable process design and optimization.