水热处理过程中伊敏褐煤微观结构的演变规律

褐煤水热处理可以脱除有害元素,降低n(O)/n(C)比,提高煤阶,有利于煤的洁净利用。利用高压反应釜对褐煤进行水热处理,采用拉曼光谱(Raman)和傅立叶红外光谱(FTIR)对处理后的煤样的化学结构进行分析,探索了不同温度水热处理后煤样微观结构的演变规律。结果表明:150℃水热处理时部分含氧官能团脱除,同时,部分脂肪族侧链断裂及不稳定大分子芳环结构分解形成小分子芳环结构,部分CO分解形成各类醚和羟基;当水热温度升至200℃,处理后褐煤的芳香度指数(R)和芳香结构稠合指数(DOC)上升,表明煤内缩合结构增加,同时,缺陷结构和杂环被去除,大分子芳环结构相对增加,CO大量分解;水热温度继续升高至250℃,褐煤发生氢转移反应导致脂肪族侧链增加;当水热温度达到300℃时,褐煤的芳环结构被破坏,交联结构和无定形碳增加。

Yimin Lignite Microstructural Transformation During Hydrothermal Treatment Process

Lignite hydrothermal treatment(HT)could remove the potential undesirable elements and reduce n(O)/n(C)ratio parameter,which is conducive to the clean utilization of the coal.In this test,the HT of lignite was conducted in an autoclave at different temperatures.FTIR and Raman spectroscopy were used to explore the microstructure changes of the lignite treated under different hydrothermal treatment temperatures.The experimental results show that some oxygen-containing functional groups are removed at 150℃.During the low temperature HT process,the aliphatic groups of the lignite are destroyed and the unstable macromolecule aromatic ring decompose into smaller molecular aromatic matters and CO decompose into ethers and hydroxyl groups.As HT temperature increases to 200℃,the aromaticity index(R)and the degree of condensation(DOC)increase,which indicates that the internal condensation structure of the coal increases,while the defect structure and heterocyclic ring are removed,the macromolecular aromatic structure increases,and a large amount of CO are destroyed.Under HT process of 250℃,due to the reaction of hydrogen transferring,the amount of the aliphatic groups increases.When HT temperature reaches 300℃,the aromatic structure of the lignite is destroyed.Simultaneously,the crosslinked structure and amorphous carbon increase.