4. Conclusions
This study reports on CO2 adsorption behavior of zeolite 13X monoliths and beads under dry and humid conditions using both clean and contaminated simulated flue gas feeds. As reported herein, zeolite beads and monoliths experienced substantial drop in CO2breakthrough time after being saturated with humidity, on account of the competitive adsorption which exists between CO2 and water. On the other hand, a cooperative effect was observed when SO2 and NO were introduced alongside the presence of water. In those experiments, water led to the formation of NaOH clusters which reacted with the acid contaminants to produce chemisorbents. In turn, this gave rise to enhanced CO­2 adsorption capacity via carbonate formation on the additional active sites. This being stated, all samples exhibited broader breakthrough fronts in the contaminated runs compared to the clean-mode experiments, as a result of added chemisorption because, although it did provide additional sites for CO2 adsorption, the mechanism for chemisorption was likely slower than that of physisorption, as it relied on the reaction kinetics instead of mass transfer alone. Therefore, this study concluded that zeolite materials – including binderless beads and 600 cpsi, and 800 cpsi monoliths – perform better under multicomponent flue gas conditions from an adsorption capacity standpoint, but exhibit slightly slower mass transfer kinetics. Moreover, this study indicated the importance of examining adsorbent materials under realistic conditions for successful implementation in scaled-processes and emphasized the need for performing cyclic adsorption-desorption experiments using multicomponent streams.