The role of char surface structure development in pulverized fuel combustion
The role of char surface structure development in pulverized fuel combustion
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DOI：
10.1016/s0016-2361(99)00259-8
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发表时间：
2000-08-01
期刊：
影响因子：
7.4
通讯作者：
Haas, J
中科院分区：
文献类型：
--
作者：
Lorenz, H;Carrea, E;Haas, J
目前的工作涉及不同烟煤焦孔表面结构对其燃烧行为的影响。在 2.5 MW 热输入的半工业喷煤火焰中对炭进行取样。将来自喷射火焰的固体样品与在等温活塞流反应器中测试的样品进行比较。对于表面表征，应用了 Nz 吸附和扫描电子显微镜。对于在两个燃烧设施中收集的炭样品，观察到 BET 表面积的差异高达一个数量级。结论是，活塞流反应器炭样品的较大表面积是由于脱挥发分过程中形成的微孔结构造成的。初始颗粒加热速率越高，微孔结构越大，从而导致孔表面积越大。因此，预计炭会表现出不同的内在反应性。然而，由于内部结构对炭消耗的控制随着温度的升高而降低，因此尝试利用从活塞流反应器实验得出的动力学参数来模拟喷射火焰中的炭烧尽。理论燃尽曲线与实验数据非常吻合，表明多孔结构可能在粉状燃料燃烧过程中发挥次要作用。扩散传输和反应速率处于同一数量级。因此，体扩散可能发挥重要作用，控制整体速率，使得内部多孔结构不会显着参与燃烧过程。 (C) 2000 Elsevier Science Ltd. 保留所有权利。
The present work is concerned with the effect of different bituminous coal chars pore surface structure on their combustion behavior. The chars were sampled in a semi-industrial coal jet flame of 2.5 MW thermal input. The solid samples from the jet flame were compared with samples tested in an isothermal plug flow reactor. For surface characterization, Nz-adsorption and scanning electronmicroscopy were applied. Differences in the BET-surface area up to one order of magnitude were observed for char samples collected in both combustion facilities. It was concluded that the larger surface area of the plug flow reactor char samples was due to a micropore structure, which was developed during devolatilization. The higher the initial particle heating rate was, the larger was the micropore structure and thus larger pore surface area resulted. Thus chars were expected to show different intrinsic reactivities. Nevertheless, since the control of internal structure on char consumption decreases as the temperature grows, an attempt was made to model char burnout in the jet flame making use of the kinetic parameters derived from the plug flow reactor experiments. Theoretical burnout curves fit remarkably well the experimental data, revealing that the porous structure may play a minor role in pulverized fuel combustion processes. Diffusive transport and reaction rates were of the same order of magnitude. Thus bulk diffusion may play a significant role, governing the global rate so that the internal porous structure is not significantly involved in the combustion process. (C) 2000 Elsevier Science Ltd. All rights reserved.