Effects of steam and CO2 on the characteristics of chars during devolatilization in oxy-steam combustion process
Effects of steam and CO2 on the characteristics of chars during devolatilization in oxy-steam combustion process
复制标题
富氧蒸汽燃烧过程中蒸汽和CO2对脱挥炭特性的影响
DOI：
10.1016/j.apenergy.2016.08.121
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发表时间：
2016-11-15
期刊：
影响因子：
11.2
通讯作者：
Xiang, Jun
中科院分区：
文献类型：
--
作者：
Xu, Jun;Su, Sheng;Xiang, Jun
煤主要在O-2/H2O气氛中燃烧，全氧蒸汽燃烧被认为是下一代全氧燃料燃烧的有前途的技术之一。本研究旨在研究煤在全氧蒸汽燃烧过程中的脱挥发特性，阐明蒸汽和CO2对煤焦特性的潜在影响。在1050℃的固定床反应器中，在不同的蒸汽/CO2/N-2气氛下制备了中国褐煤的焦炭，并用FT-IR/拉曼光谱仪和热重分析仪对其进行了表征。结果表明：氧蒸汽燃烧脱挥发过程中炭的产率低于N-2气氛，水蒸气气化反应起关键作用；高浓度的蒸汽会显著加速焦炭中芳香环的缩聚，与N-2气氛相比，氧蒸汽燃烧脱挥发过程中会形成更多的缩聚焦炭。高浓度蒸汽中的CO2对炭产率影响不大，但能参与炭表面的交联反应，在一定程度上降低了脱挥发过程中炭的缩聚。蒸汽和CO2气化反应不仅加速了煤中原有含氧官能团的消耗，而且在焦炭中增加了一些含氧官能团。氧蒸汽燃烧脱挥发过程中形成的炭的反应活性低于N-2燃烧。拉曼带面积比I((Gr+VI+V)r/I- d与焦炭反应性呈良好的线性关系，证实了焦炭反应性的降低主要是由于焦炭的缩聚引起的。(C) 2016 Elsevier Ltd.版权所有。
Oxy-steam combustion is considered as one of promising technologies for the next generation oxy-fuel combustion, in which coal mainly burns in O-2/H2O atmosphere. This work aims to investigate the devolatilization characteristics of coal in oxy-steam combustion and clarify the potential effects of steam and CO2 on the char characteristics. Chars of a Chinese lignite were prepared in a fixed-bed reactor at 1050 degrees C under various steam/CO2/N-2 atmospheres and characterized by a FT-IR/Raman spectrometer and thermogravimetric analyzer. The results indicate the char yield during devolatilization in oxysteam combustion was lower than that in N-2 atmosphere, and the steam gasification reaction played the key role. The high concentration of steam would significantly accelerate the condensation of aromatic rings in the char, and more condensed char would form during devolatilization in oxy-steam combustion compared to that in N-2 atmosphere. CO2 in high concentration of steam had little effects on the char yields but it could participate in the cross-linking reactions on the char surface and partly reduce the condensation of the chars during devolatilization. Steam and CO2 gasification reactions can not only speed up the consumption of the original O-containing functional groups in the coal but also bring some additional O-containing functional groups in the char. The reactivity of the char formed during devolatilization in oxy-steam combustion was lower than that in N-2. A good linear relationship between the Raman band area ratio I((Gr+VI+V)r/I-D and char reactivity confirmed the decrease of the char reactivity was mainly attributed to the condensation of the char. (C) 2016 Elsevier Ltd. All rights reserved.