热提质过程中褐煤物化结构的演变及其与反应性关联的探究

The lignite resources in China are relatively abundant, and have the potential of main energy and chemicals feedstocks under the tendency of insufficient supplies of high quality coal. However, the high moisture content in lignite limits its large-scale utilization, thus the upgrading treatments are the key techniques for its efficient conversion. During upgrading processes, the physical and chemical structures of lignite would change along with, which will directly affect the stability of lignite's surface and its following conversion reactions. In this research proposal, the lignites with different moisture and ash contents will be selected, and then upgraded by hot gas upgrading under different atmospheres, microwave drying and hydrothermal dewatering processes. The main purposes are to insight the collapse, development and transformation of the pore structure of lignite, and the decomposition, generation and conversion of CHx and O-containing groups; to investigate the moisture re-adsorption behavior, pyrolysis reactivity, combustion reactivity, and the tendency of surface oxidation and spontaneous combustion; to find the relationships between the conversion reactivity of upgraded lignite and the composition properties, pore structure, and evolution of all function groups based on these; to make comparisons in the energy efficiency of different water forms removing during different upgrading processes based on the reasonable classification and quantitative analysis of water forms in lignite; and at last but not least to provide the basically theoretical support on the low energy consumption and high energy efficiency coupling of different upgrading process and the clean conversion and utilization of lignite.

我国褐煤资源相对丰富，在优质煤资源供应紧张的趋势下具有作为能源与化工主原料的潜力，但高水分含量限制了其大规模开发利用，干燥提质也成为褐煤有效转化的关键。褐煤提质过程中，物化结构会随之发生改变，这与其表面稳定性、后续转化反应具有直接的关联。选取水分含量和灰分含量不同的褐煤为研究对象，采用不同气氛下热气干燥、微波干燥和水热脱水等方法进行褐煤的热提质处理，重点考察提质过程中褐煤孔隙结构的坍塌、发育、转变以及各CHx基团和不同含氧基团的分解、生成与转化规律；揭示褐煤的水分复吸特性、热解反应性、燃烧反应性、表面氧化和自燃倾向性在提质前后的变化行为，并基于此关联煤种特性、孔隙结构和各类基团的演变与提质煤转化的反应性；在对褐煤中水分存在形式合理归类和定量分析的基础上，对比分析不同干燥方式下褐煤中不同形态水分脱除的能效，为不同褐煤干燥方式的低能耗、高能效耦合和褐煤的清洁高效利用提供基础理论支撑。

针对褐煤高水分含量制约其高效清洁利用的问题，采用固定床热气干燥、微波干燥和水热脱水等技术对褐煤进行提质处理，重点关注了该过程中褐煤孔隙结构和表面基团的演变，揭示了褐煤水分复吸、自燃倾向和燃烧反应性的变化规律，并对干燥提质过程的能耗和能效进行了优化分析。以含水量不同的云南褐煤和内蒙褐煤为实验原料，通过低温差示扫描量热仪对褐煤中水分赋存形态和含量进行了表征测定，进一步分析了不同类型水分的理论脱水能耗；利用微波和固定床干燥装置对褐煤进行干燥实验，考察了操作条件对褐煤干燥特性及脱水能耗的影响。对不同温度和操作时间下不同方法制得的干燥提质煤样进行孔结构特性表征，获得了褐煤比表面积、孔体积、孔径在固定床干燥、微波干燥和水热提质过程中的演变规律；对干燥提质煤样采用传统化学滴定和原位漫反射红外光谱进行表面化学结构分析，考察煤样表面官能团在热提质过程中的变化，揭示了褐煤中脂肪族CHx(CH3、CH2、CH)和含氧官能团的分解转化规律；进一步分析获得了内蒙褐煤和云南褐煤不同温度下水热提质过程中，煤样中C、H、O、N和S元素的迁移路径。以不同干燥提质方式所得褐煤作为研究对象，进行水分复吸和低温氧化实验，对比分析三种干燥提质方式所得褐煤的平衡含水量和自燃倾向性，探索了煤样物化结构对其表面稳定性的影响实质。考察不同干燥提质方式对褐煤燃烧反应性的影响，获得了水热提质比其它两种提质方式能够更好地改善褐煤的燃烧行为；通过分析水热提质煤的燃烧反应性参数，探索了褐煤芳香度和孔结构的改变对其燃烧阶段的影响机制。本研究取得的结果可为褐煤的高效清洁利用提供基础理论指导，具有较为广泛的应用前景。项目的实施，已培养硕士研究生5名、在培养博士研究生2名，研究结果申报和授权国家发明专利3项，发表期刊论文11篇、会议论文3篇。