Mass transfer coefficients considering effects of steam in oxy-fuel combustion of coal char
Mass transfer coefficients considering effects of steam in oxy-fuel combustion of coal char
复制标题
煤焦富氧燃烧中考虑蒸汽影响的传质系数
DOI：
10.1016/j.fuel.2013.04.027
复制
发表时间：
2013-09
期刊：
影响因子：
7.4
通讯作者：
Ou, Wei
中科院分区：
文献类型：
--
作者：
Yu, Juan;Zhou, Kuan;Ou, Wei
考虑到Stefan流和水蒸气在煤焦富氧燃烧中的影响，推导了O2、CO2和H2O气体反应物传质系数的修正因子。通过与实验数据、刚性连续膜模型和未修正的单膜模型的比较，可以得出结论，修正大大改善了颗粒温度、燃烧速率和燃尽时间的预测。校正因子与气体组分、反应数和速率比有关。一般来说，表面反应次数和速率的增加会导致Stefan流的增强，从而降低传质系数。但在典型的富氧燃烧条件下的讨论表明，不同的反应对反应气体的传质有不同的影响。在水蒸气存在下，由于H_2O气化速率低，O_2在H_2O和H_2中扩散传递加速，对O_2的修正与忽略水蒸气的情况基本相同。由于H2O的气化速率仅略高于CO2的气化速率，CO2的校正值略微增加了约3%。相反，O2和CO2反应的参与对H2O的传质系数起着相当大的作用。特别是O2氧化等高速率反应对气体反应物的传质影响更为显著。因此，在煤焦富氧燃烧过程中，当O2氧化反应占主导地位时，传质系数将发生很大变化，应注意对传质系数的修正。
Considering the effects of Stefan flow and steam in the oxy-fuel combustion of char, correction factors for the mass transfer coefficients of gas reactants, O2, CO2, and H2O, are derived in the present work. By comparisons with the experimental data, the rigid continuous-film model, and the uncorrected single-film model, it is concluded that the corrections greatly improve the predictions of the particle temperature, combustion rates and burnout time. The correction factors are related to the gas components, reaction numbers and rate ratios. Generally, the increase of number and rate of surface reaction will result in the enhancement of Stefan flow and hence decrease the mass transfer coefficients. But discussion under the typical conditions of oxy-fuel combustion shows that different reaction has different impacts on the mass transfer of reactive gases. In the presence of steam, the correction for O2is nearly the same as cases neglecting the steam, owing to the low gasification rate of H2O and the accelerative diffusion transfer of O2in H2O and H2. The correction for CO2increases slightly by about 3% because the gasification rate of H2O is only a little higher than that of CO2. On the contrary, the participation of O2and CO2reactions plays considerable role in the mass transfer coefficient of H2O. Especially, the high rate reaction, like O2oxidation, has more remarkable effects on the mass transfer of gas reactants. Therefore, more attention should be paid to the modification of mass transfer coefficients when the O2oxidation reaction is prevailing in the char oxy-fuel combustion, for the transfer coefficients will be greatly changed.
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DOI：
10.1016/b978-0-12-669550-2.50019-1
发表时间：
1980
期刊：
--
影响因子：
--
作者：
N. Amundson;E. Mon
通讯作者：
N. Amundson;E. Mon
影响因子：
5.3
作者：
Juan Yu;M. C. Zhang
通讯作者：
Juan Yu;M. C. Zhang
影响因子：
5.3
作者：
Juan Yu;Mingchuan Zhang
通讯作者：
Juan Yu;Mingchuan Zhang
影响因子：
5.3
作者：
R. Essenhigh
通讯作者：
R. Essenhigh
影响因子：
4.4
作者：
A. Hayhurst
通讯作者：
A. Hayhurst