A mathematical model of ash formation during pulverized coal combustion
A mathematical model of ash formation during pulverized coal combustion
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DOI：
10.1016/s0016-2361(01)00166-1
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发表时间：
2002-02
期刊：
影响因子：
7.4
通讯作者：
L. Yan;RajenderKumar Gupta;T. Wall
中科院分区：
文献类型：
--
作者：
L. Yan;RajenderKumar Gupta;T. Wall
本文建立了高煤种煤粉燃烧过程中灰分形成的数学模型。该模型基于计算机控制的扫描电子显微镜(CCSEM)对煤粉中矿物的表征。从与煤碳基质的共生关系来看，煤粒中的单个矿物颗粒可分为包裹型和排除型。包裹体矿物是指被碳基质紧密包围的离散矿物颗粒。被排除的矿物是那些不与煤碳物质或至少与煤碳物质相关的被释放的矿物。在模型中，包含矿物和排除矿物被分开处理。根据煤和矿物粒度分布，假定夹杂矿物随机分散在单个煤粒之间。单个煤粒中夹杂矿物的部分聚结机理与脱挥发分过程中形成的焦粒结构有关。用泊松分布的随机方法模拟了排外矿物的破碎，这对于排外矿物比例很大的煤来说尤其重要。在与锅炉相似的操作条件下，在滴管炉中燃烧了澳大利亚烟煤的窄尺寸样品。将实验灰粒度分布和化学成分与模型预测值进行了比较。结果表明，该模型基本反映了高煤阶煤灰分形成的两种重要机制--包裹体矿物的聚结和排外矿物的碎裂的综合作用。
A mathematical model of ash formation during high-rank pulverized coal combustion is reported in this paper. The model is based on the computer-controlled scanning electron microscope (CCSEM) characterization of minerals in pulverized coals. From the viewpoint of the association with coal carbon matrix, individual mineral grains present in coal particles can be classified as included or excluded minerals. Included minerals refer to those discrete mineral grains that are intimately surrounded by the carbon matrix. Excluded minerals are those liberated minerals not or at least associated with coal carbon matter. Included minerals and excluded minerals are treated separately in the model. Included minerals are assumed to randomly disperse between individual coal particles based on coal and mineral particle size distributions. A mechanism of partial-coalescence of included minerals within single coal particles is related to char particulate structures formed during devolatilization. Fragmentation of excluded minerals, which is important particularly for a coal with a significant fraction of excluded minerals, is simulated using a stochastic approach of Poisson distribution. A narrow-sized sample of an Australian bituminous coal was combusted in a drop-tube furnace under operating conditions similar to that in boilers. The particle size distribution and chemical composition of experimental ash were compared to those predicted with the model. The comparisons indicated that the model generally reflected the combined effect of coalescence of included minerals and fragmentation of excluded minerals, the two important mechanisms governing ash formation for high-rank coals.