PROGRESS IN COAL PYROLYSIS
PROGRESS IN COAL PYROLYSIS
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DOI：
10.1016/0016-2361(93)90570-r
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发表时间：
1993-05-01
期刊：
影响因子：
7.4
通讯作者：
PUGMIRE, RJ
中科院分区：
文献类型：
--
作者：
SOLOMON, PR;FLETCHER, TH;PUGMIRE, RJ
煤的非均质性质和热解过程的复杂性使得很难进行明确的实验来确定煤的热解速率和机理。然而，近年来出现了许多新的实验和理论方法，为这一课题提供了新的线索。本文综述了煤的动力学、挥发分形成、网络模型、交联度、级数效应以及煤结构的‘双组分’模型的最新进展。最近的实验测量了高升温速率下的煤颗粒温度，对动力学速率常数提供了合理的一致性。这些速率也与在低升温速率下的实验结果相一致。在焦油的形成和输送中，人们就焦油分子的挥发性在解释操作条件(压力、升温速度、颗粒大小等)变化方面的核心作用达成了共识。焦油的数量和分子量分布。通过最近开发的大分子煤网络裂解模型，焦油和焦炭产量的定量预测正在取得进展。这些模型定量描述了煤的化学结构与热解产物(气体、焦油、烟尘和焦炭)的物理化学性质之间的关系，是对热解过程理解的一个令人兴奋的进步。这些模型将煤中塑性相的出现与热解过程中形成的“液体”碎片联系在一起。关于倒退的交联化反应，包括溶剂溶胀和n.m.r。测量结果证实了反应速率随等级变化的重要差异；这些差异似乎与氧官能度有关。在低升温速率下测量得到的动力学速率随煤级的变化也有合理的一致性。实验表明，最近重新提出的煤结构双组分假说适用于低煤阶煤，这种煤是由两种不同组分组成的混合物：聚亚甲基和一个更芳香的网络。然而，烟煤看起来要同质得多。尽管实验可以区分松散结合组分和紧密结合组分，但这些组分似乎由相似的材料组成，并且主要是在它们的分子量和与网络的连接程度方面有所区别。这些煤的行为似乎符合网络分解模型所描述的方式。
The heterogeneous nature of coal and 'the complexity of the pyrolysis process have made it very difficult to perform unambiguous experiments to determine the rates and mechanisms in coal pyrolysis. However, recent years have seen a number of new experimental and theoretical approaches which shed new light on the subject. This paper considers the recent progress on kinetics, the formation of volatile products, network models, cross-linking, rank effects, and the 'two-component' model of coal structure. Recent experiments which measured coal particle temperatures at high heating rates provide reasonable agreement on kinetic rate constants. These rates also agree with those derived from experiments at low heating rates. In tar formation and transport, a consensus is being reached on the central role of the volatility of tar molecules in explaining the variation with operating conditions (pressure, heating rate, particle size, etc.) of the amounts and molecular weight distributions of tars. Progress in the quantitative prediction of tar and char yields is being made through recently developed models for the fragmentation of the macromolecular coal network. These models, which provide quantitative descriptions of the relations between the chemical structure of the coal and the physical and chemical properties of the pyrolysis products (gas, tar, soot, and char), are an exciting advance in the understanding of the pyrolysis process. Such models are linking the occurrence of the plastic phase of the coal with the 'liquid' fragments formed during pyrolysis. On the subject of retrogressive cross-linking reactions, both solvent swelling and n.m.r. measurements confirm important rank-dependent differences in reaction rates; these appear to be related to the oxygen functionalities. Reasonable agreement is also seen for variations with coal rank of kinetic rates derived from measurements at low heating rates. Experiments suggest that the recently revived 'two-component' hypothesis of coal structure has application to low-rank coals, which are mixtures of two distinct components: polymethylenes and a more aromatic network. Bituminous coals, however, appear far more homogeneous. Although experiments can distinguish loosely and tightly bound fractions these fractions appear to consist of similar materials and are differentiated primarily in their molecular weight and degree of connection to the network. These coals appear to behave in a manner that is described by the network decomposition models.