GENERAL-MODEL OF COAL DEVOLATILIZATION
GENERAL-MODEL OF COAL DEVOLATILIZATION
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DOI：
10.1021/ef00010a006
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发表时间：
1988-07-01
期刊：
影响因子：
5.3
通讯作者：
DESHPANDE, GV
中科院分区：
文献类型：
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作者：
SOLOMON, PR;HAMBLEN, DG;DESHPANDE, GV
提出了煤脱挥发分的通用模型，该模型结合了气体逸出的官能团模型和焦油形成的统计模型。焦油形成模型包括解聚、交联、外部传输和内部传输。交联与CO 2 和CH 4 的演化有关，每个演化分子形成一个交联。该模型的预测结果与匹兹堡煤层煤和北达科他州 (Beulah) 褐煤脱挥发分的各种数据相比较，包括挥发物产量、萃取物产量、交联密度和焦油分子量分布。准确预测了压力、脱挥温度、等级和加热速率的变化。该模型与采用传输替代假设的几组数据的比较表明，假设颗粒充分混合（即焦油分子的表面浓度与本体浓度相同）会高估传输速率。对于 50 mhi 粒子，假设内部传输限制占主导地位（即忽略外部传输），可以很好地拟合数据。焦油形成、提取物产率、交联和粘度的等级依赖性似乎可以通过CO 2 产率及其相关交联的等级依赖性来解释。低阶煤中的高CO 2 产率在低温下产生快速交联，并因此产生热固性行为、低焦油产率、低萃取物产率、溶剂溶胀性能的损失和高粘度。然而，与断键相比，交联的相对重要性对加热速率敏感，并且模型预测了这种效应。改进模型的领域包括（1）细化内部和外部传输假设，（2）考虑除乙烯之外的氢芳香族结构和桥结构，以及（3）包括聚亚甲基“客体”分子。
A general model for coal devolatilization, which combines a functional group model for gas evolution and a statistical model for tar formation, has been presented. The tar formation model includes depolymerization, cross-linking, external transport, and internal transport. The cross-linking is related to the evolutions of C02 and CH4, with one cross-link formed per molecule evolved. The model predictions compare favorably with a variety of data for the devolatilization of Pittsburgh Seam coal and North Dakota (Beulah) lignite, including volatile yields, extract yields, cross-link densities, and tar molecular weightdistributions. The variations with pressure, devolatilization temperature, rank, and heating rate were accurately predicted. Comparison of the model with several sets of data employing alternative assumptions on transport suggests that assuming that the particle is well mixed (ie the surface concentration of tar molecules is the same as the bulk) overpredicts the transport rate. For 50-mhi particles, assuming that the internal-transport limitation dominates (ie neglecting the external transport) provides a good fit to the data. The rank dependence of tar formation, extract yields, cross-linking, and viscosity appears to be explained by the rank dependence of C02 yields and its associated cross-linking. High C02 yields in low-rank coals produce rapid cross-linking at low temperatures and hence thermosetting behavior, low tar yields, low extract yields, loss of solventswelling properties, and high viscosities. The relative importance of cross-linking compared to bond breaking is, however, sensitive to heating rate, and this effect is predicted by the model. Areas for improving the model include (1) refinement of the internal and external transport assumptions,(2) accounting for hydroaromatic structures and bridge structures besides ethylene, and (3) including polymethylene “guest” molecules.