煤结构演化与生气过程关系研究

Study on the relationship between chemical structure evolution and gas generation of coal

利用傅里叶红外光谱分析技术对煤化程度(R_O)范围为0.35%~5.32%的19个煤样进行了结构分析。分析结果表明:随着R_O值的增加,煤结构中不同的官能团具有不同的演化规律。芳环结构中C-H键在红外谱图中先增加,当R_O>3.0%后逐渐减小。含氧侧链与脂肪族侧链随着R_O值增加,吸收峰强度总体呈减弱的趋势。含氧官能团的含量在逐渐的减少,R_O>2.5%时,煤结构中基本不再含有含氧侧链;脂肪族侧链R_O<2.0%时,脂肪侧链随着煤化程度的增加快速减少,R_O>2.0%时脂肪族侧链在煤结构中缓慢减少,当R_O>2.5%时,在煤结构中检测到的脂肪侧链已经很少。煤结构的上述演化规律预示着煤在不同的演化阶段具有不同的生气特征。R_O<0.8%含氧侧链在煤结构的快速减少说明CO_2气的生成主要发生在相对低的演化阶段;脂肪侧链两段式的演化规律说明煤的主要生气(烃类气体)阶段发生在R_O<2.0%,而煤生气结束的煤化程度界限为R_O>5.0%。煤在石墨化过程中从芳环上脱落的氢与煤在演化阶段生成的CO_2之间发生的费—托反应可能是过成熟阶段煤成气碳同位素倒转(反转)的一个重要因素。

The chemical structure of 1 9 samples with maturities ranging from 0.35 % to 5.32 % Ro was meas- ured by Fourier transform infrared spectroscopy（FTIR）.The results show that with the increase of Ro ,dif- ferent functional groups in coal structure have different evolution rules.The C-H bond on the aromatic ring structure increases first,when Ro〉2.5 %, decreases in the infrared spectrum. With the increase of Ro, the overall trend of absorption peaks intensity of the oxygen side chain and aliphatic side chain weakened.The content of oxygen-containing functional groups decreased gradually. When Ro 〉 2.5 %, the coal structure basically no longer contains oxygen side chain;When Ro〈2.0% ,the aliphatic side chain increased rapidly with increasing coalifieation;when R c〉2.0%, the aliphatic side chain in the coal structure slowly reduced; when Ro〉2.5 % ,nearly no fat side chain was detected in the coal structure.This demonstrates that coal has different gas generation features at different stages.The rapid reduction of coal content in the oxygen-con- taining side chain indicates that the formation of CO2 gas mainly occurs in the relatively low evolution stage.The two-stage evolution aliphatic groups indicated that the main gas generation period of coal was at the stage with thermal maturity 〈2.0%Ro,however,the upper limit of thermal maturity for gas genera tion from coal was 〉 5.0%Ro. The Fischer-Tropsch reaction, which happened between hydrogen atom cleaved from aromatic rings at graphitization （Ro 〉 3.0%） and CO2 gengerated by oxygen-containing groups cleavage from coal at Ro〈2.0% ,should be one of the important reasons causing carbon isotopic re- versal of coal derived gases at over maturity.