Combustion characteristics of lignite char in a fluidized bed under O-2/N-2, O-2/CO2 and O-2/H2O atmospheres
Combustion characteristics of lignite char in a fluidized bed under O-2/N-2, O-2/CO2 and O-2/H2O atmospheres
复制标题
O-2/N-2、O-2/CO2、O-2/H2O气氛下褐煤焦在流化床中的燃烧特性
DOI：
10.1016/j.fuproc.2018.12.007
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发表时间：
2019
影响因子：
7.5
通讯作者：
Anthony Edward John
中科院分区：
文献类型：
--
作者：
Li Lin;Duan Lunbo;Tong Shuai;Anthony Edward John
O2/H2O燃烧作为全氧燃烧研究的一个新热点，具有O2/CO2燃烧无法比拟的诸多优点，逐渐受到人们的重视。H2O独特的物理化学性质（热容、扩散性、反应性）对煤焦的燃烧特性有重要影响。在流化床反应器中，研究了不同O2浓度（15%~ 27%）和床温（Tb，837-937 °C）下，N2、CO2和H2O气氛下褐煤焦颗粒的燃烧和动力学特性。结果表明，在低O2浓度下，褐煤半焦在H2O气氛中的平均反应速率和峰值反应速率均比在CO2气氛中慢。但随着O2浓度的增加，H2O气氛下褐煤焦的热解速率和热解速率均显著提高，并超过CO2气氛下的热解速率和热解速率。基于缩核模型的活化能计算结果表明，不同气氛下的活化能大小顺序为：O2/CO2（28.96 kJ/mol）> O2/H2O（26.11 kJ/mol）> O2/N2（23.31 kJ/mol）。此外，气化反应在O2/CO2和O2/H2O燃烧中都起着不可忽视的作用。随着Tb的增加，气化剂所占的活性位显著增加，而氧所占的活性位相应减少。
As a possible new focus of oxy-fuel work, O2/H2O combustion has many advantages over O2/CO2combustion, and has gradually gained increasing attention. The unique physicochemical properties (thermal capacity, diffusivity, reactivity) of H2O significantly influence the char combustion characteristics. In the present work, the combustion and kinetics characteristics of lignite char particle were studied in a fluidized bed (FB) reactor under N2, CO2and H2O atmospheres with different O2concentrations (15%–27%) and bed temperatures (Tb, 837–937 °C). Results indicated that the average reaction rate (raverage) and the peak reaction rate (rpeak) of lignite char in H2O atmospheres were slower than those in CO2atmospheres at low O2concentrations. However, as the O2concentration increases, therpeakandraverageof lignite char in H2O atmospheres significantly improved and exceeded those under CO2atmospheres. The calculation result for the activation energy based on the shrinking-core model showed that the order of activation energy under different atmospheres is: O2/CO2(28.96 kJ/mol) > O2/H2O (26.11 kJ/mol) > O2/N2(23.31 kJ/mol). Furthermore, gasification reactions play an important role in both O2/CO2and O2/H2O combustion, and should not be ignored. As theTbincreased, the active sites occupied by gasification agent were significantly increased, while the active sites occupied by oxygen decreased correspondingly.