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Abstract(s)
In the last few decades of industrialization, there has been a significant increase in the concentration of carbon dioxide (CO2) and other greenhouse gases in the atmosphere, which has a visible harmful effect on the environment we live in today. Regarding that, many organizations around the world have invested heavily in research activities towards CO2 capture and storage. Adsorption processes are characterized with low energy costs and can involve low investment in terms of both initial cost and space required.
In this work, the adsorption equilibrium of CO2 and N2 in commercial binder-free beads of KY zeolite has been studied between 313 K and 423 K and pressure up to 3.5 bar using a gas chromatographic technique (frontal chromatography/breakthrough technique). At the temperature of 313 K, the results showed that the amount adsorbed of CO2 in binder-free KY is up to 6.42 mol.kg-1 with heats of adsorption of 41.4 kJ.mol-1. The amount adsorbed of N2 at similar conditions is much less compared to CO2 where it doesn’t exceed 0.68 mol.kg-1 being the heat of adsorption around 21.1 kJ.mol-1. The adsorption equilibrium data were fitted with the Langmuir and the dual-site Langmuir (DSL) models and compared with other Y zeolites modified by cation exchange available in literature. The comparisons showed that the commercial binder-free KY studied in this work is a good alternative adsorbent for the adsorption CO2, being also characterized by a high adsorption capacity at low pressure (below 1 bar) when compared to other cation exchanged materials. In addition, the binder-free type KY was responsible for an improvement for up to 20 % in CO2 loading compared to the standard binder beads of KY zeolite.
Binary-component experiments CO2/N2 were also carried out under typical post-combustion conditions (15% CO2 / 85% N2) at 313, 373 and 423 K. At 313 K, the selectivity of CO2 over N2 goes over 105 at low pressures below 0.1 bar. At 298 K, the competitive working capacity between 0.03 and 1 bar is equal to 4.52 mol.kg-1, which is a relatively high value when compared with materials such as: Mg-MOF-74 and zeolite 13X. Generally, the results show that binder-free KY works best in the low-pressure region and therefore, is a promising adsorbent for the recovery of CO2 from post-combustion streams. Also, the binary breakthrough curves CO2/N2 onto the binder-free zeolite KY were simulated using a numerical technique developed in MATLAB. The results showed that the zone spreading of the breakthrough curves in the bed are completely dominated by axial dispersion. The effect of the flowrate of N2 to clean the bed was also studied by simulation and the results showed that it is possible to reduce the total volume of N2 used in the desorption step by at least 13% while reducing the N2 purge time up to 71%.
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Keywords
Sorption of CO2 Sorption of N2