Effect of Syngas Constituents on CdO- and MgO-Based Sorbents for Pre-combustion CO2 Capture

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• 作者：Christian Vogt ; Gregory P. Knowles ; Alan L. Chaffee
• 刊名：Energy & Fuels
• 出版年：2015
• 出版时间：September 17, 2015
• 年：2015
• 卷：29
• 期：9
• 页码：5909-5918
• 全文大小：612K
• ISSN：1520-5029

文摘

Magnesium oxide/cesium carbonate composites as well as cadmium oxide/sodium halide mixtures have been previously described as potential candidates for pre-combustion carbon dioxide capture. Here, the effects of water and hydrogen alongside CO₂ were examined in simulated partial pressure swing experiments analyzed by thermogravimetric means. It was shown that the magnesium/cesium sorbents are tolerant to hydrogen at a temperature of 370 掳C and that their working capacities over 25 cycles are enhanced by the addition of water to the sorption gas stream. The cadmium/sodium iodide sorbent showed a stable working capacity for 23 sorption cycles at 285 掳C, but tended to lose working capacity after that point. At 305 掳C, a significant loss in capacity was observed during sorption cycling. As reduction in an inert gas/hydrogen mixture was not found to commence below 400 掳C, a halide promoter disintegration mechanism is assumed to be the cause of the decay. The sorption of hydrogen sulfide was also examined. Both Cd- and Mg-based materials showed a significant uptake of H₂S, which was hard to desorb. It appears that H₂S sorption competes alongside CO₂ sorption, causing a reduction in working capacities over multiple cycles. Powder X-ray diffraction showed that the Cd-based sorbent forms CdS upon H₂S sorption, whereas the MgO phase of the Mg-based sorbent is not changed. A new Cs phase was formed from cesium carbonate with H₂S, which is probably a previously unreported magnesium鈥揷esium sulfide mixed phase.