Role of char in NO_x formation during coal combustion at a regenerator temperature of calcium looping process

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• 作者：Caiyun Gao ; Takanori Higuchi ; Ayato Yoshizawa ; Tadaaki Shimizu ; Heejoon Kim ; Liuyun Li
• 关键词：Fluidized bed ; Solid circulation ; Nitric oxide ; Carbon monoxide ; Carbon dioxide
• 刊名：Fuel
• 出版年：1 April, 2014
• 年：2014
• 卷：121
• 期：Complete
• 页码：319-326
• 全文大小：717 K

文摘

Coal of three kinds was burned in an oxygen-enriched atmosphere using two types of reactor both of which had the same fast fluidized bed for coal combustion. One was a dual-fluidized bed system (dual-FB), simulating Calcium Looping process comprised a fast fluidized bed regenerator and a bubbling bed carbonator. The other was a conventional single circulating fluidized bed combustor (single-CFBC). In both systems, coal combustion in oxygen-enriched atmosphere was carried out under regenerator temperature condition of Calcium Looping process. Inert quartz sand was used as the bed material to evaluate carbon consumption in the carbonator of dual-FB. Formation of NO_x in the fast fluidized beds was measured for both reactors. For dual-FB, formation of CO and CO₂ in the carbonator was also measured. High-volatile matter coal was found to be favorable to reduce CO and CO₂ formation in the carbonator, but conversion of the fuel-N to NO_x of high-volatile matter coal was higher than that from low-volatile coal. The emissions of NO_x from single-CFBC were less than those from the regenerator of dual-FB under the same combustion condition. From the emissions of CO and CO₂ from the carbonator, the decrease in char combustion in the regenerator of dual-FB was calculated. An empirical relationship between the conversion of fuel-N to NO_x in the fast fluidized bed and the ratio of fixed carbon to volatile matter of the fuel was obtained.