Modeling of CO2 Adsorption on Activated Carbon and 13X Zeolite via Vacuum Swing Adsorption

摘要

Due to carbon dioxide role in global warming, low CO2 emission limits have been established in recent years. This has led to a variety of studies on CO2 removal approaches. In this study, a VSA cycle consisting of two packed beds is considered for CO2 removal from flue gas. An atmospheric stream containing 20% CO2 and 80% N2 is fed to the beds at 50°C. Two adsorbents, namely Zeolite 13X and activated carbon were selected to compare their performance. Due to the monolayer adsorption of CO2 and N2 on these adsorbents, the Toth isotherm was used for equilibrium adsorption estimation. A quasi-second order model was considered for the mass transfer rate prediction due to low CO2 concentration. The modeling results showed that the average absolute deviation for equilibrium adsorption capacity prediction was 2%, and the CO2 breakthrough time curve was predicted with less than 2.5% deviation. Based on the results, the VSA cycle time for zeolite 13X bed will be 3.5 times of the activated carbon bed. Another advantage of Zeolite 13X is that in each process cycle, 80% of adsorbent will be used, while only 74% of activated carbon in beds is used. The advantage of activated carbon bed is its better regeneration capability, since the activated carbon will be regenerated 5% more than zeolite 13X at a vacuum pressure of 0.02bar.