The effects of using structurally less-stable raw materials for the support of a spray-dried oxygen carrier with high NiO content

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• 作者：Jeom-In Baek ; Chong Kul Ryu ; Ji Hyun Lee ; Tae Hyoung Eom ; Joong Beom Lee ; Ho-Jung Ryu ; Jungho Ryu ; Jongheop Yi
• 关键词：Chemical-looping combustion ; Oxygen carrier ; Nickel oxide ; Spray-drying method
• 刊名：Fuel
• 出版年：2012
• 出版时间：December, 2012
• 年：2012
• 卷：102
• 期：Complete
• 页码：106-114
• 全文大小：1160 K

文摘

An oxygen carrier for chemical looping combustion (CLC) requires high mechanical strength, high reactivity, and other physical properties suitable for fluidized-bed processes. Spray-dried NiO oxygen carriers prepared using structurally stable raw materials such as ¦Á-Al₂O₃ and MgAl₂O₄ as support have required a calcination temperature above 1400 ¡ãC to obtain sufficient mechanical strength applicable to fluidized-bed process, and their oxygen transfer capacity has been less than 10 wt % . Here, we present a spray-dried oxygen carrier prepared using high NiO content (70 wt % ) and structurally less-stable raw materials (20 wt % ¦Ã-Al₂O₃, 5 wt % pseudoboehmite, and 5 wt % bentonite), which resulted in reducing a calcination temperature and enhancing the performances of the oxygen carrier. The prepared oxygen carrier showed excellent physical properties, especially high mechanical strength and spherical shape, suitable for fluidized-bed applications and high reactivity. The calcination temperature to obtain sufficient mechanical strength was lowered to 1100 ¡ãC. At the reaction temperature of 950 ¡ãC, the oxygen transfer capacities determined by a thermogravimetric analyzer were 13.9 and 12.4 wt % for the oxygen carriers calcined at 1100 and 1250 ¡ãC, respectively, indicating more than 82 % of the total oxygen in the raw NiO was transferred to the fuel. The excellent physical properties were still maintained after ten cyclic redox tests in a bubbling fluidized-bed reactor. On the other hand, the oxygen carrier prepared with ¦Á-Al₂O₃ had sufficient mechanical strength when calcined at 1400 ¡ãC, and showed much lower performance in reactivity and physical properties. This work confirms that the use of high NiO content and structurally less-stable raw support materials composed of ¦Ã-Al₂O₃ mixed with a small amount of pseudoboehmite and bentonite can reduce the calcination temperature to obtain sufficient mechanical strength and improve the performance of a spray-dried NiO oxygen carrier for the CLC of gaseous fuels.