Preliminary Research on the Effects of Coal Devolatilization and Char Combustion Processes on the Emission of Particulate Matter during Lignite Combustion under Air and Oxy-fuel Conditions

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• 作者：Chang WenBin Fan ; Wenyu Wang ; Xianpeng Zeng ; Ge Yu ; Weizhi Lv ; Minghou Xu
• 刊名：Energy & Fuels
• 出版年：2017
• 出版时间：January 19, 2017
• 年：2017
• 卷：31
• 期：1
• 页码：224-230
• 全文大小：428K
• ISSN：1520-5029

文摘

The pulverized coal combustion in both air and oxy-fuel conditions generally experiences successive coal devolatilization and char combustion processes. The effects of these two processes have important influence on the emission characteristics of particulate matter. With some different characteristics of lignite from the higher rank coal, including the high contents of organically bound cations and the apparent char–CO<sub>2sub> gasification reaction upon oxy-fuel combustion, the effects of both coal devolatilization and char combustion processes on the emission characteristics of particulate matter during oxy-fuel combustion of lignite would accordingly be distinctive. A typical Chinese lignite was devolatilized in a N<sub>2sub> or CO<sub>2sub> atmosphere to generate N<sub>2sub>–char and CO<sub>2sub>–char, respectively. Raw coal and the two chars were burned in a drop-tube furnace under both air and oxy-fuel conditions. Afterward, the yields and inorganic compositions of segregated PM<sub>10sub> were carefully analyzed. The results have shown that the devolatilization in the N<sub>2sub> condition promotes the emission of sub-micrometer particles (PM<sub>0.5sub>) and coarse particles (PM<sub>1–10sub>) but the devolatilization process in CO<sub>2sub> inhibits their emission. N<sub>2sub>–char and CO<sub>2sub>–char present entirely different combustion behavior and, thus, reflect the discrepant emission characteristics of PM<sub>10sub>. The rough higher yields of PM<sub>0.5sub> and PM<sub>1–10sub> from N<sub>2sub>–char combustion compared to raw coal combustion may be driven by the higher particle combustion rate and/or temperature of N<sub>2sub>–char. Furthermore, the quite severe gasification reaction of CO<sub>2sub> with char during char preparation results in an inhibited combustion rate of CO<sub>2sub>–char, which can explain the case in which much less PM<sub>0.5sub> and PM<sub>1–10sub> are generated from CO<sub>2sub>–char combustion than those from raw coal and N<sub>2sub>–char combustion. The apparent effects reveal that more detailed work can be continued to further explore this research.