To deepen understanding of the evolution of coal char microstructural properties of coal char during the co-pyrolysis of coking coal with additives,this study incorporated two typical additives,coal tar pitch(CTP)and ...To deepen understanding of the evolution of coal char microstructural properties of coal char during the co-pyrolysis of coking coal with additives,this study incorporated two typical additives,coal tar pitch(CTP)and waste plastic(HDPE),into a blended coal sample and carried out pyrolysis experiments.The pyrolysis process and the microstructure of char were systematically characterized using various analytical techniques,including thermogravimetric analysis(TGA),X-ray diffraction(XRD)and Raman spectroscopy.Data correlation analysis was performed to reveal the mechanism of carbon structural ordering evolution within the critical temperature range(350−600℃)from colloidal layer formation to semi-coke conversion in coking coal,and to elucidate the regulatory effects of different additives on coal pyrolysis pathways.The results indicate that HDPE releases free radicals during high-temperature pyrolysis,accelerating the pyrolysis reaction and increase the yield of volatile components.Conversely,CTP facilitates pyrolysis at low temperatures through its light components,thereby delaying high-temperature reactions due to the colloidal layer’s effect.XRD results indicate that during the process of pyrolysis,there is a progressive decrease in the interlayer spacing of aromatic layers(d002),while the aromatic ring stacking height(L_(c))and lateral size(L_(a))undergo significant of carbon skeleton ordering.Further comparative reveals that CTP partially suppresses structural ordering at low temperatures,whereas HDPE promotes the condensation and alignment of aromatic clusters via a free radical mechanism.Raman spectroscopy reveals a two-stage reorganization mechanism in the microstructure of the coal char:the decrease in the I_(D)/I_(G)ratio between 350 and 550℃is primarily attributed to the cleavage of aliphatic side chains and cross-linking bonds,leading to a reduction in defective structures;whereas the increase in ID/IG between 550 and 600℃is closely associated with enhanced condensation reactions of aromatic structures.Correlation analysis further demonstrates progressive graphitization during pyrolysis,with a significant positive correlation(R^(2)>0.85)observed between d002 and the full width at half maximum of the G-band(FWHM-G).展开更多
采用气相色谱-质谱法(GC/MS)、傅立叶变换红外光谱法(FTIR)和热裂解气质联用仪(Py-GC/MS)等先进表征仪器,探究了不同溶剂(CS_(2)、丙酮和等体积丙酮/CS_(2)混合溶剂)萃取焦油渣(coal tar residue,CTR)后,萃取物的组成特征及萃余物(分别...采用气相色谱-质谱法(GC/MS)、傅立叶变换红外光谱法(FTIR)和热裂解气质联用仪(Py-GC/MS)等先进表征仪器,探究了不同溶剂(CS_(2)、丙酮和等体积丙酮/CS_(2)混合溶剂)萃取焦油渣(coal tar residue,CTR)后,萃取物的组成特征及萃余物(分别记为RCTR1、RCTR2和RCTR3)的热解产物分布规律。进一步结合热重分析(TG-DTG)与Coats-Redfern动力学模型,探究CTR萃余物热解过程中的潜在反应路径。结果表明:相比于CTR,三种萃余物中苯环类官能团含量减少且具有较好的热稳定性。萃取物中可检测的化合物以芳烃为主,相对含量分别为37.06%、32.86%和33.61%。表明以上三种溶剂可选择性破坏芳环间的π—π作用、强氢键作用和氢键/π—π复合作用,从而削弱分子量较小的多环芳烃(1~5环)与CTR中较大分子(如稠环芳烃,≥6环)间的作用力,使得分子量较小的芳烃类化合物更易被提取。此外,三种萃余物在460°C下的热解产物以烷烃为主,其中RCTR1和RCTR3热解产物中主要是C_(21)~C_(30)的正构烷烃,而RCTR2热解产物中的烷烃以C11~C20为主。最后,动力学模型随温度升高呈现从D1型向F2型的渐进转变,表明萃余物热解过程中存在物理扩散与化学键断裂的协同作用机制。展开更多
基金Supported by National Natural Science Foundation of China(22378180,22078141)Education Department Foundation of Liaoning Province(JYTMS20230960)。
文摘To deepen understanding of the evolution of coal char microstructural properties of coal char during the co-pyrolysis of coking coal with additives,this study incorporated two typical additives,coal tar pitch(CTP)and waste plastic(HDPE),into a blended coal sample and carried out pyrolysis experiments.The pyrolysis process and the microstructure of char were systematically characterized using various analytical techniques,including thermogravimetric analysis(TGA),X-ray diffraction(XRD)and Raman spectroscopy.Data correlation analysis was performed to reveal the mechanism of carbon structural ordering evolution within the critical temperature range(350−600℃)from colloidal layer formation to semi-coke conversion in coking coal,and to elucidate the regulatory effects of different additives on coal pyrolysis pathways.The results indicate that HDPE releases free radicals during high-temperature pyrolysis,accelerating the pyrolysis reaction and increase the yield of volatile components.Conversely,CTP facilitates pyrolysis at low temperatures through its light components,thereby delaying high-temperature reactions due to the colloidal layer’s effect.XRD results indicate that during the process of pyrolysis,there is a progressive decrease in the interlayer spacing of aromatic layers(d002),while the aromatic ring stacking height(L_(c))and lateral size(L_(a))undergo significant of carbon skeleton ordering.Further comparative reveals that CTP partially suppresses structural ordering at low temperatures,whereas HDPE promotes the condensation and alignment of aromatic clusters via a free radical mechanism.Raman spectroscopy reveals a two-stage reorganization mechanism in the microstructure of the coal char:the decrease in the I_(D)/I_(G)ratio between 350 and 550℃is primarily attributed to the cleavage of aliphatic side chains and cross-linking bonds,leading to a reduction in defective structures;whereas the increase in ID/IG between 550 and 600℃is closely associated with enhanced condensation reactions of aromatic structures.Correlation analysis further demonstrates progressive graphitization during pyrolysis,with a significant positive correlation(R^(2)>0.85)observed between d002 and the full width at half maximum of the G-band(FWHM-G).
文摘采用气相色谱-质谱法(GC/MS)、傅立叶变换红外光谱法(FTIR)和热裂解气质联用仪(Py-GC/MS)等先进表征仪器,探究了不同溶剂(CS_(2)、丙酮和等体积丙酮/CS_(2)混合溶剂)萃取焦油渣(coal tar residue,CTR)后,萃取物的组成特征及萃余物(分别记为RCTR1、RCTR2和RCTR3)的热解产物分布规律。进一步结合热重分析(TG-DTG)与Coats-Redfern动力学模型,探究CTR萃余物热解过程中的潜在反应路径。结果表明:相比于CTR,三种萃余物中苯环类官能团含量减少且具有较好的热稳定性。萃取物中可检测的化合物以芳烃为主,相对含量分别为37.06%、32.86%和33.61%。表明以上三种溶剂可选择性破坏芳环间的π—π作用、强氢键作用和氢键/π—π复合作用,从而削弱分子量较小的多环芳烃(1~5环)与CTR中较大分子(如稠环芳烃,≥6环)间的作用力,使得分子量较小的芳烃类化合物更易被提取。此外,三种萃余物在460°C下的热解产物以烷烃为主,其中RCTR1和RCTR3热解产物中主要是C_(21)~C_(30)的正构烷烃,而RCTR2热解产物中的烷烃以C11~C20为主。最后,动力学模型随温度升高呈现从D1型向F2型的渐进转变,表明萃余物热解过程中存在物理扩散与化学键断裂的协同作用机制。
