基于有机显微组分的煤非平均化学结构模型构建及热解机理研究

Deeply understanding the coal pyrolysis mechanism is not only the key to improve the efficiency and environment protecting of traditional coal conversion process, but also the theoretical basis for exploring new ways of clean and efficient coal utilization way. This project is based on coal heterogeneous chemical structure, and the coal will be regarded as consist of typical organic components with special chemical structure in micrometer scale and the coal pyrolysis process will be decomposed into typical organic components pyrolysis themselves and the interactions between them, to further study the coal structures and coal pyrolysis mechanism. This project will firstly reveal the chemical structure characteristics of typical organic components and their cross-linking structures in micrometer scale with the key help of micro-Raman spectroscopy and Raman mapping technology, and the non-average coal chemical structure model will be built. Secondly, the pyrolysis experiments of typical organic components alone and their quantitatively mixed components will be carried out. The characteristics of their pyrolysis products will be analyzed in multi-angle and multi-scale. The reasonable correlations between the chemical structures of typical organic components and their pyrolysis characteristics will be set up, and the interactions mechanism between typical organic components during coal pyrolysis will also be revealed. Finally, the pyrolysis model based on the analysis of non-uniform structure will be established in this project, giving an efficient way to predict the products characteristics of coal pyrolysis more precisely and providing important theoretical basis for the clean and efficient utilization of coal.

深刻理解煤热解机理，不仅是传统煤转化过程清洁高效化的关键，也是探索煤清洁高效利用新途径并进行有效指导必不可少的理论基础。本项目基于煤化学结构非均匀特性，将煤视为微米尺度下具有典型化学结构特性的有机显微组分组成，将煤热解过程分解为特征显微组分独立热解与显微组分间交互作用两个关键单元，深入开展煤结构及其热解机理研究。重点借助显微共焦拉曼光谱分析与拉曼成像等先进微米尺度化学结构表征技术，探究微米尺度下煤特征显微组分化学结构及其交联特性，建立基于有机显微组分的煤非平均化学结构模型；其次，对特征显微组分独立及其定量混配组分进行热解实验，多角度、多尺度定量表征煤热解产物特性，建立煤显微组分化学结构与热解反应性的关联关系，揭示煤热解过程中特征显微组分间的交互作用机制；最终，建立基于非均匀结构体解析的煤热解模型，实现对煤热解产物的准确预测，为煤的清洁高效利用提供重要理论基础。

本项目深入开展了煤非平均化学结构及其热解特性研究。项目团队首先结合显微拉曼光谱分析技术，构建了基于显微拉曼化学成像的煤化学结构定量表征方法。并利用该方法，研究了煤特征显微组分化学结构特性。结果表明在微米尺度下，煤化学结构具有显著非均匀性，且化学结构差异主要体现在小芳香环，C-H，O-H，C-O等取代结构上。在空间上，结构差异组分具有明显区域可分性，不同煤种其结构统计分布特性差异明显，且不呈正态分布。进一步，通过对典型煤种热解过程中微米尺度颗粒化学结构特征及演化特性研究，提出了量化煤焦非均匀度的化学指标，并探讨了煤非平均热解过程。结果表明煤在热解过程中，微米尺度颗粒的结构演化特性各不相同，尤其在热解初期。热解过程中，微米尺度煤焦颗粒化学结构逐渐趋于一致，不均匀程度降低。热解条件越剧烈，所形成煤焦非均匀性越大。项目团队进一步采取特征显微组分分离再热解，探讨了显微组分化学结构与热解反应性间定量关系。结果表明显微组分的热解反应性与其H/C以及小环与大环比等化学结构参数存在明显数学关联。项目团队进一步对比研究了三种典型煤种酸洗原煤分离镜质组、酸洗原煤分离惰质组以及由两种显微组分定量混配组分的热解特性。结论表明镜质组与惰质组在热解过程中存在着明显交互反应，会抑制气体产物的释放，且对于低阶煤，镜质组含量越大，抑制效果越明显。镜质组与惰质组共热解时，含杂原子的脂肪族类化合物释放明显减少，脂肪烃类释放明显增加。两者热解释放的含氧等杂原子的脂肪族类化合物会相互作用，在煤焦碳骨架大分子结构中形成以氧杂原子为中心的交联结构，并更多的以脂肪烃释放出来。最后通过耦合上述煤结构特性及反应机理模型，构建了煤非平均化学结构模型及完整的非线性煤热解反应动力学。另外，项目团队在此项目研究基础上，提出了基于激光拉曼的煤质在线检测技术，并开展了工程示范，检测效果较好，显著提高了煤质分析速率，是一种有应用前景的新技术。