胜利褐煤热解过程中结构演变及气体生成机理分析

褐煤的热解反应是褐煤利用的重要研究方向之一。为了分析褐煤热解过程中结构演变及气体生成机理，首先将胜利褐煤（SL）在固定床上进行热解制焦，利用800 ℃时SL热解气体生成速率曲线选取半焦终温，同时用气相色谱在线检测其所生成的热解气；其次结合煤焦傅里叶变换红外光谱（FT-IR）的表征进行分析，将半焦的FT-IR分峰拟合计算；最后将计算参数结合热解气生成规律，提出了热解升温过程中各反应阶段生成气体机理和气体生成过程中煤体结构的演变规律。结果表明，SL具有羟基、脂肪烃、芳环、羰基、醚键等丰富的官能团，热解温度低于350 ℃，胜利褐煤中主要官能团未发生明显变化；350~450 ℃，脂肪族侧链含氧官能团分解，热解温度450 ℃比350 ℃时煤焦中C〖CDS1〗O相对含量（C1）降低78%；560~800 ℃，热解反应主要以芳香烷基侧链含氧官能团裂解为主，热解温度800 ℃时煤焦中C-O相对含量（C2）比560 ℃时降低27%；热解温度710~800 ℃时，煤热解以缩聚反应为主，热解温度800 ℃煤焦中芳香稠和度（D2）比710 ℃时升高65%。对4种热解气生成过程进行研究分析，CO2主要来源于中低温区煤中不同结构的羧基官能团分解；高温区生成CO，来源于煤中酚类、醚类、含氧杂环等结构的分解；CH4主要由芳环侧链的甲基、亚甲基或连接芳环结构亚甲基的分解；高温区产生的约60%H2主要来自于煤中芳香结构的缩聚反应。

Analysis of structural evolution and gas generation mechanism during the py rolysis of Shengli lignite

Pyrolysis reaction of lignite is one of the important research directions in lignite utilization.Firstly,Shengli Lignite (SL) was pyrolyzed on a fixed bed for coking in order to analyze the structure evolution and gas formation mechanism of lignite during pyrolysis.The final temperature of semi coke was determined by using the curve of SL pyrolysis gas generation rate at 800 ℃.The pyrolytic gases was detected on line by gas chromatography.Secondly,the characterization of Fourier transform infrared spectroscopy (FT IR) of coal char is analyzed.And the FT IR peak of semi coke is fitted and calculated.Finally,combining the calculation parameters with the law of pyrolysis gas generation,the mechanisms of gas generation in each reaction stage during pyrolysis heating and the evolution law of coal structure in the process of gas generation were proposed.The results show that SL has abundant functional groups such as hydroxyl,aliphatic hydrocarbon,aromatic ring,carbonyl and ether bond.And the main functional groups in lignite have not changed,when the pyrolysis is below 350 ℃.Aliphatic oxygen containing functional groups are decomposed between 350 and 450 ℃.The C〖CDS1〗O relative content (C1) at the pyrolysis final temperature of 450 ℃ is 78% lower than that of 350 ℃.When the pyrolysis temperature is between 560 and 800 ℃,the pyrolysis reaction is mainly based on the decomposition of oxygen containing functional groups of aromatic alkyl side chains.And the C-O relative content (C2) at the pyrolysis final temperature of 800 ℃ is 27% lower than that of 450 ℃.At 710-800 ℃ range,the main pyrolysis reaction is polycondensation.The aromatic condensation (D2) of chars at a final pyrolysis temperature of 800 ℃ is 65% higher than that at 710 ℃.Four kinds of pyrolysis gas generation processes were studied and analyzed that CO2 is mainly derived from the decomposition of carboxyl functional groups of different structures in the middle and low temperature zone.CO is generated in the high temperature,which is derived from the decomposition of the structures of phenol,ether and oxygen containing heterocyclic rings in coal.The decomposition of CH4 is mainly from the aromatic ring or methylene connecting the aromatic rings.The approximate 60% H2 mainly comes from the polycondensation reaction of aromatic structures in coal at a high temperature zone.