Comparison of Equilibrium Adsorption of Different Adsorbents in the Separation of Carbon Dioxide from Nitrogen

Behnam Rezazadeh1, Amin alamdari2*

1- Ph. D. Student of Chemical Engineering, Faculty of chemical Engineering, sahand University of Technology, Tabriz, Iran
2- Assistant Professor, Faculty of Engineering, Department of Chemical Engineering, Urmia University, Urmia, Iran
*Corresponding Author Email: a.alamdari@urmia.ac.ir
Abstract
There are various adsorbents for the separation of nitrogen and carbon dioxide gases with different adsorption capacity and selectivity. A comprehensive comparison should be made between different adsorbents to select the appropriate adsorbent for a desired process. In this paper, the equilibrium adsorption value and selectivity of different adsorbents have been investigated using the Ideal Adsorption Solution Theory (IAST) to determine the appropriate adsorbent for the separation of nitrogen and carbon dioxide gases. The (IAST) model has been used to compare adsorbents at different pressures (1 to 100 kPa) and in a 50-50 percent composition to compare adsorbents in different gas percentage compositions (0.9-0.1) at a total pressure of 100 kPa. The results showed that the activated carbon/zeolite adsorbent has the highest selectivity at a temperature of 298 K and the KIT-6 adsorbent has the highest total adsorption. The studies showed that the Zeolite 13X adsorbent has lower selectivity and adsorption capacity than other adsorbents. Finally, a new trade-off diagram was prepared based on the adsorption rate versus selectivity of different adsorbents to guide researchers for use in industrial applications.
Keywords
Adsorption, Nitrogen, Carbon oxide, Ideal Adsorption Solution Theory (IAST)












EXTENDED ABSTRACT
Introduction
CO2 emission from fossil fuel combustion is considered as one of the main issues of environmental problems and global warming has actuated the researches on CO2 separation from flue gas. However, various methods have been used to removing CO2 from natural gas and flue gas, among which the adsorption is considered as a more cost-effective technical solution, along with low energy consumption, simple design, environmental efficient method. On the other hand, there is no simple comparison between the performances of the adsorbents. In this regard, a method it can be used to select an appropriate adsorbent with high selectivity, coupled with the effect of operating conditions on performance, the ideal adsorption solution theory (IAST). Theory (IAST) is one of the most reliable methods for predicting adsorption equilibrium of gas mixtures, which is often used to predict the equilibrium of mixture of gas mixture and only uses pure component adsorption. for CO2/N2 separation, various adsorbents were reported .In this research, CO2/N2 adsorbents were compared with the calculations of two - component mixture adsorption by use (IAST) under pressure of 1-100 kpa .At the end, a new commercial design of the adsorption values as a simple guide for researchers for industrial applications for the selection of high-performance adsorbents for the separation of CO2/N2 has been prepared.
Theory and modeling: IAST method
This method is one of the most widely used models to predict the balance in multicomponent mixtures. the advantages of this method are high speed, simple calculations, thermodynamic stability, and the ability to use all existing equilibrium isotherms. This theory assumes that the adsorbed mixture is an ideal solution, where there is no interaction between the components present in the adsorption phase. This theory is based on thermodynamic solutions which is independent of the real adsorption model. Different versions of this theory have been proposed that are continued by prausnitz that are extended for fast systems and other versions such as vermeilen have been developed by Luan which can be used to improve the speed of calculations in this research, by using ideal adsorption solution and related MATLAB program, two - component mixture adsorption modelling was investigated. Variations in selectivity versus pressure changes as well as the difference between the adsorbents in the selectivity and the total uptake for different adsorbents were introduced. For the two-component adsorption calculations, the adsorption data of pure component is required.
Results and discussion
By changing the operating pressure in the range of 1-100 kPa for the gas mixture (50 - 50) CO2/N2, different adsorbents were investigated. The results show that by increasing the pressure on the adsorbent type, the amount of carbon dioxide adsorbed increases with further increase or is not significantly changed. Also, it is shown that the effect of increasing pressure leads to an increase in adsorption rate. Also, for the activated carbon - AQSOA FAM Z02 - KIT‑6 adsorbent, a very little change in the adsorption rate is created. Also, by increasing the selectivity of MIL 100 (Fe) - Activated carbon/zeolit, as expected, we see more selectivity at low temperatures the selectivity of adsorbent is more than other adsorbents. In this adsorbent, the adsorbent has a selectivity at 303 K and the adsorbent KIT‑6 has the maximum total uptake. On the other hand, MOF-505@GO adsorbent has less selectivity and less adsorption capacity than other adsorbents. However, the choice of the adsorbent should be based on economic calculations.
Conclusion
The performance of different adsorbents was investigated for CO2/N2 separation using the idea of al adsorption solution. Among all the adsorbents MIL-100(Fe) and Activated carbon/zeolite and activated/zeolite adsorbents have selectivity to CO2/N2, respectively. Among the selected adsorbents, the highest CO2 adsorption belongs to KIT‑6 the obtained diagram of CO2 adsorption in the presence of CO2 selectivity for different adsorbents is prepared which is a suitable guide for selecting appropriate adsorbent for industrial applications of these adsorbents.
Abstract
There are various adsorbents for the separation of nitrogen and carbon dioxide gases with different adsorption capacity and selectivity. A comprehensive comparison should be made between different adsorbents to select the appropriate adsorbent for a desired process. In this paper, the equilibrium adsorption value and selectivity of different adsorbents have been investigated using the Ideal Adsorption Solution Theory (IAST) to determine the appropriate adsorbent for the separation of nitrogen and carbon dioxide gases. The (IAST) model has been used to compare adsorbents at different pressures (1 to 100 kPa) and in a 50-50 percent composition to compare adsorbents in different gas percentage compositions (0.9-0.1) at a total pressure of 100 kPa. The results showed that the activated carbon/zeolite adsorbent has the highest selectivity at a temperature of 298 K and the KIT-6 adsorbent has the highest total adsorption. The studies showed that the Zeolite 13X adsorbent has lower selectivity and adsorption capacity than other adsorbents. Finally, a new trade-off diagram was prepared based on the adsorption rate versus selectivity of different adsorbents to guide researchers for use in industrial applications.