不同变质程度煤在胶质体阶段的碳结构演变探究

Study on carbon structure evolution of coal with different metamorphism degrees in colloidal stage

煤炭清洁高效利用对实现双碳目标具有重要意义。利用自制焦炉对5种炼焦煤(观音堂焦煤、马头焦煤、五沟肥煤、萧县肥煤和兖州西气煤)进行热解成焦,并提取了不同温度段的煤样。结合傅立叶变换红外光谱(FTIR)和X射线衍射(XRD)等表征手段对煤样的碳结构进行了探究。FTIR结果显示,5种原煤的芳香结构以苯环二取代和四取代为主,相对含量均达到50%以上,随着温度升高,5种煤样的苯环二取代相对含量均有不同程度降低,而苯环四取代和五取代相对含量变化则呈现两段性。5种原煤的脂肪结构以甲基和亚甲基为主,随温度升高,观音堂焦煤、马头焦煤、五沟肥煤和萧县肥煤中的亚甲基相对含量分别降低了18.85%、13.75%、16.50%和12.65%,而兖州西气煤的亚甲基相对含量在450℃达到最低,其次甲基相对含量在450℃后迅速从42.11%降低至22.87%。计算了5种煤样的FTIR结构参数,发现450~550℃阶段煤样的芳碳率、芳氢率均明显增加,脂肪支链长度迅速减短。XRD结果显示,随着温度升高,焦煤和肥煤的层间距减小至0.344~0.346 mm,而气煤的层间距只减小了0.007 nm,5种煤样的横向尺寸呈现先减小后增加的趋势,而堆垛高度则呈现增加的趋势。焦煤和肥煤的碳结构参数变化明显,焦煤的芳香度提高至0.82左右,肥煤的提高至0.73左右,而气煤的芳香度仅有0.57。

The clean and efficient utilization of coal is of great significance for achieving the dual carbon goals.Five types of coking coal(Guanyintang coking coal,Matou coking coal,Wugou fat coal,Xiaoxian fat coal and Yanzhouxi gas coal)were pyrolyzed into coke using a self-made coke oven,and coal samples at different temperature ranges were extracted.The carbon structures of coal samples were investigated by combining characterization methods such as Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD).The FTIR results show that the aromatic structures of the five types of raw coal are mainly benzene ring disubstituted and tetrasubstituted,with relative contents exceeding 50%.As the temperature increases,the relative content change of benzene ring disubstituted in the five types of coal samples decreases to varying degrees,while the relative content of benzene ring tetrasubstituted and pentasubstituted shows a two-stage pattern.The fatty structures of five types of raw coal are mainly composed of methyl and methylene.As the temperature increases,the relative contents of methylene in Guanyintang coking coal,Matou coking coal,Wugou fat coal and Xiaoxian fat coal decrease by 18.85%,13.75%,16.50%and 12.65%,respectively.The relative content of methylene in Yanzhouxi gas coal reaches the lowest at 450℃,followed by a rapid decrease in methenyl content from 42.11%to 22.87%after 450℃.The FTIR structural parameters of the five coal samples were calculated,and it is found that the aromatic carbon and hydrogen rates of the coal samples significantly increase during the stage from 450℃to 550℃,while alkyl chain length rapidly decreases.The XRD results show that as the temperature increases,the interplanar spacings of coking coal and fat coal decrease to 0.344 nm to 0.346 nm,while the interplanar spacing of gas coal only decreases by 0.007 nm.The lateral dimensions of the five coal samples show a trend of first decreasing and then increasing,while stacking heights show an increasing trend.The carbon structure parameters of coking coal and fat coal show significant changes,with the aromaticity of coking coal increasing to around 0.82,fat coal increasing to around 0.73,and gas coal having an aromaticity of only 0.57.