Numerical simulation of the devolatilization of a moving coal particle
Numerical simulation of the devolatilization of a moving coal particle
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DOI：
10.1016/j.combustflame.2008.10.004
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发表时间：
2009-05
影响因子：
4.4
通讯作者：
F. Higuera
中科院分区：
文献类型：
--
作者：
F. Higuera
采用热解竞争反应模型对孤立的煤粒相对于周围气体运动的脱挥发过程进行了数值模拟，并假定释放的挥发分在颗粒周围无限薄的扩散火焰中燃烧或完全不燃烧。假定颗粒温度均匀，忽略了热解热、颗粒内传质阻力和颗粒半径变化的影响。研究了颗粒的大小和速度、气体的温度和氧气质量分数对颗粒和火焰的温度历史、脱挥时间和轻、重挥发分产率的影响。颗粒的运动可能对挥发分火焰的形状和位置有重要影响，但对于煤粉燃烧典型的粒度来说，它对挥发分的脱除过程只有轻微的影响。这种效应对于大粒子或在没有辐射的情况下会增加。相对运动增强了颗粒与气体之间的换热，导致气体温度较高时的脱挥时间缩短，气体温度较低时的脱挥时间延长。数值计算结果与该过程传热模型中常用的吹气修正Nusselt数关联式进行了比较。
The devolatilization of an isolated coal particle moving relative to the surrounding gas is numerically simulated using a competing reaction model of the pyrolysis and assuming that the released volatiles burn in an infinitely thin diffusion flame around the particle or not at all. The temperature of the particle is assumed to be uniform and the effects of the heat of pyrolysis, the intraparticle mass transfer resistance, and the variation of the particle radius are neglected. The effects of the size and velocity of the particle and of the temperature and oxygen mass fraction of the gas on the particle and flame temperature histories, the devolatilization time and the yield of light and heavy volatiles are investigated. The motion of the particle may have an important effect on the shape and position of the flame of volatiles, but it has only a mild effect on the devolatilization process for the particle sizes typical of pulverized coal combustion. This effect increases for large particles or in the absence of radiation. The relative motion enhances the heat transfer between the particle and the gas, causing the devolatilization time to decrease at high gas temperatures and to increase at low gas temperatures. The numerical results are compared with a blowing-corrected Nusselt number correlation often used in heat transfer models of the process.