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The Nature of Adsorbed CO2 and Amine Sites on the Immobilized Amine Sorbents Regenerated by Industrial Boiler Steam

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journal contribution
posted on 04.09.2013, 00:00 by Mathew Isenberg, Steven S. C. Chuang
The nature of adsorbed CO2 on immobilized amine sorbents regenerated with utility boiler steam was studied by in-situ infrared spectroscopy. The use of industrial boiler steam is the key factor lowering the overall operating cost of the immobilized amine CO2 capture process for megawatt-scale coal-fired power plants. The industrial steam is known to contain trace amounts of Cu, Fe, and Zn species. The present study was undertaken to understand the chemistry occurring between the Cu contaminants in the steam and the amine sites on the sorbent. Cu-containing steam from the utility boilers resulted in a 91% loss of CO2 capture capacity over 30 continuous CO2 capture and regeneration cycles. UV–vis and in-situ IR studies suggest that the degraded sorbent contained CuII ions coordinated with nitrogen atoms of an imine species. These imine species are incapable of adsorbing CO2. The remaining amine species could bind weakly with CO2, mainly in the form of carbamic acid. The formation of ammonium ion species was inhibited by adsorbed Cu species on the degraded sorbent. Cu-free steam is required for stripping adsorbed CO2 from the amine sorbent in the CO2 capture process. The findings presented here should be considered before implementing a pilot-scale CO2 capture process from coal-fired power plant flue gas.