基于铁基载氧体的煤化学链气化还原过程中氮元素迁移行为
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摘要
采用热重-质谱-红外联用技术(TG-MS-FTIR),Ar气氛下对煤进行化学链气化实验,实时分析还原过程热解阶段和水蒸气气化反应阶段的过程中固体质量变化和生成气体成分。使用X射线光电子能谱对固相产物进行表面元素分析,探究化学链气化还原过程不同阶段固相产物中氮赋存形态的变化。研究结果表明:载氧体对化学链气化还原过程不同阶段含氮气体释放均有影响。热解阶段载氧体促进自由基的生成,加速了一次热解阶段含氮气体的释放,高温下,载氧体促使NH3转化为HCN;气化阶段载氧体的加入使半焦的石墨化程度降低,含氮气体释放速率增加。对固相产物中氮的赋存形态而言,载氧体会抑制热解阶段吡咯型氮的分解与转化,高温下,半焦的石墨化和有序化程度降低的同时,镶嵌在煤大分子里面的质子化吡啶裸露出来,质子化吡啶含量降低,吡啶型氮和吡咯型氮的含量大大提升。
The combined thermo gravimetric-infrared-mass spectrometry(TG-FTIR-MS) analysis was used to conduct chemical-looping gasification experiments of coal under Ar atmosphere, and the mass change and gas composition during pyrolysis stage and steam gasification reaction stage of reduction process were monitored in real time. The surface element analysis of the solid phase was carried out by Xray photoelectron spectroscopy, when the change of nitrogen functional groups in the solid phase at different stages of chemical-looping gasification reduction process was investigated. The results showed that the oxygen carrier had an effect on the release of nitrogen-containing gas in different stages of the chemical-looping gasification reduction process. During the pyrolysis stage, the oxygen carrier promoted the generation of free radicals, which accelerated the release of nitrogen-containing gas in a pyrolysis stage. At high temperature, the oxygen carrier favored the conversion of NH3 to HCN, and the addition of the oxygen carrier during the gasification stage reduced the degree of graphitization of the semi-coke and increased the release rate of the nitrogen-containing gas. For the nitrogen functional groups in the solid phase, the oxygen carrier promoted the decomposition and conversion of pyrrole nitrogen in the pyrolysis stage. At high temperature, as the graphitization and ordination degree of semi-coke decreased, the protonated pyridine embedded in coal macromolecules was exposed, the content of protonated pyridine decreased, and the content of pyridine nitrogen and pyrrole nitrogen increased greatly.
The combined thermo gravimetric-infrared-mass spectrometry(TG-FTIR-MS) analysis was used to conduct chemical-looping gasification experiments of coal under Ar atmosphere, and the mass change and gas composition during pyrolysis stage and steam gasification reaction stage of reduction process were monitored in real time. The surface element analysis of the solid phase was carried out by Xray photoelectron spectroscopy, when the change of nitrogen functional groups in the solid phase at different stages of chemical-looping gasification reduction process was investigated. The results showed that the oxygen carrier had an effect on the release of nitrogen-containing gas in different stages of the chemical-looping gasification reduction process. During the pyrolysis stage, the oxygen carrier promoted the generation of free radicals, which accelerated the release of nitrogen-containing gas in a pyrolysis stage. At high temperature, the oxygen carrier favored the conversion of NH3 to HCN, and the addition of the oxygen carrier during the gasification stage reduced the degree of graphitization of the semi-coke and increased the release rate of the nitrogen-containing gas. For the nitrogen functional groups in the solid phase, the oxygen carrier promoted the decomposition and conversion of pyrrole nitrogen in the pyrolysis stage. At high temperature, as the graphitization and ordination degree of semi-coke decreased, the protonated pyridine embedded in coal macromolecules was exposed, the content of protonated pyridine decreased, and the content of pyridine nitrogen and pyrrole nitrogen increased greatly.
引文
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[20] LIU Lina, LI Wenpei, XIONG Zesen, et al. Synergistic effect of iron and copper oxides on the formation of persistent chlorinated aromatics in iron ore sintering based on in situ XPS analysis[J]. Journal of Hazardous Materials, 2019, 366:202-209.
[21] YU Yang, WEI Huangzhao, YU Li, et al. Catalytic wet air oxidation of m-cresol over surface modified sewage sludge derived carbonaceous catalyst[J]. Catal. Sci. Technol., 2016(6):1085-1093.
[22]?ZTA?N A, OZTAS N A, YüRüM Y, et al. Effect of catalysts on the pyrolysis of turkish zonguldak bituminous coal[J]. Fuel&Energy Abstracts, 2000, 43(4):58.
[23] HOLSTEIN W L, BOUDART M. Transition metal and metal oxide catalysed gasification of carbon by oxygen, water, and carbon dioxide[J]. Fuel, 1983, 62(2):162-165.
[24] SADEZKY A, MUCKENHUBER H, GROTHE H, et al. Raman microspectroscopy of soot and related carbonaceous materials:Spectral analysis and structural information[J]. Carbon, 2005, 43(8):1731-1742.
[25]姚明宇,刘艳华,车得福.宜宾煤中氮的形态及其变迁规律研究[J].西安交通大学学报, 2003, 37(7):759-763.YAO Mingyu, LIU Yanhua, CHE Defu. Study on the form and change law of nitrogen in Yibin coal[J]. Journal of Xi'an Jiaotong University,2003, 37(7):759-763.
[26] WANG Cuiping, GONG Mingxin, LI Yongpeng, et al. Side reactions of coal tar pyrolysis products with different reduction states of iron-based oxygen carriers[J]. Energy&Fuels, 2018, 32(2).
[27]鞠付栋,陈汉平,杨海平,等.不同变质煤热解和气化中燃料氮的转化规律[J].煤炭转化, 2011, 34(3):21-26.JU Fudong, CHEN Hanping, YANG Haiping, et al. Conversion law of fuel nitrogen in pyrolysis and gasification of different metamorphic coals[J]. Coal conversion, 2011, 34(3):21-26.
[2] SONG Tao, GUO Wanjun, SHEN Laihong. Fuel nitrogen conversion in chemical looping with oxygen uncoupling of coal with a CuO-based oxygen carrier[J]. Energy and Fuels, 2015, 29(6):3820-3832.
[3]常丽萍.煤热解、气化过程中含氮化合物的生成与释放研究[D].山西:太原理工大学, 2004.CHANG Liping. Study on the formation and release of nitrogencontaining compounds during coal pyrolysis and gasification[D].Shanxi:Taiyuan University of Technology, 2004.
[4]刘钦甫,徐占杰,崔晓南,等.不同煤化程度煤的热解及氮的释放行为[J].煤炭学报, 2015, 40(2):450-455.LIU Qinfu, XU Zhanjie, CUI Xiaonan, et al. Release behavior of nitrogen in different rank coals during pyrolysis[J]. Journal of China Coal Society, 2015, 40(2):450-455.
[5] GONG B, BUCKLEY A N, LAMB R N, et al. XPS determination of the forms of nitrogen in coal pyrolysis chars[J]. Surface&Interface Analysis, 2015, 28(1):126-130.
[6] GORBATY M L, KELEMEN S R. Characterization and reactivity of organically bound sulfur and nitrogen fossil fuels[J]. Fuel Processing Technology, 2001, 71(1/2/3):71-78.
[7]刘海明,张军营,郑楚光,等.煤中吡咯型和吡啶型氮热解稳定性研究[J].华中科技大学学报(自然科学版), 2004, 32(11):18-20.LIU Haiming, ZHANG Junying, ZHENG Chuguang, et al. Study on pyrolysis stability of pyrrole and pyridine nitrogen in coal[J]. Journal of Huazhong University of Science and Technology(Natural Science Edition), 2004, 32(11):18-20.
[8] WóJTOWICZ M A, PELS J R, MOULIJN J A. The fate of nitrogen functionalities in coal during pyrolysis and combustion[J]. Fuel, 1995,74(4):507-516.
[9]孟韵,居学海,肖鹤鸣.密度泛函理论研究煤中有机氮的热解机理[J].南京理工大学学报(自然科学版), 2008, 32(2):241-247.MENG Yun, JU Xuehai, XIAO Heming. Density functional theory study on pyrolysis mechanism of organic nitrogen in coal[J]. Journal of Nanjing University of Science and Technology(Natural Science Edition), 2008, 32(2):241-247.
[10]葛涛,马祥梅.炼焦煤中碳、氧、氮、硫赋存特征的XPS研究[J].煤炭技术, 2018(3):293-295.GE Tao, MA Xiangmei. XPS study on the occurrence characteristics of carbon, oxygen, nitrogen and sulfur in coking coal[J]. Coal Technology,2018(3):293-295.
[11] PHIRI Z, EVERSON R C, NEOMAGUS H W J P, et al.Transformation of nitrogen functional forms and the accompanying chemical-structural properties emanating from pyrolysis of bituminous coals[J]. Applied Energy, 2018, 216:414-427.
[12] PHIRI Z, EVERSON R C, NEOMAGUS H W J P, et al. The effect of acid demineralising bituminous coals and de-ashing the respective chars on nitrogen functional forms[J]. Journal of Analytical&Applied Pyrolysis, 2017, 125:127-135.
[13] GUO Qingjie, CHENG Yu, LIU Yongzhuo, et al. Coal chemical looping gasification for syngas generation using an iron-based oxygen carrier[J]. Industrial&Engineering Chemistry Research, 2014, 53(1):78-86.
[14]胡月,王伟,花秀宁,等.不同负载铁基载氧体的制备与性能研究[J].应用化工, 2014(6):979-981.HU Yue, WANG Wei, HUA Xiuning, et al. Preparation and reactivity performance of iron-based oxygen carriers supported on different inert carriers[J]. Applied Chemical Industry, 2014(6):979-981.
[15] MIECZYSLAW K. XPS study of reductively and non-reductively modified coals[J]. Fuel, 2004, 83(3):259-265.
[16] ZHANG Yongchun, ZHANG Jun, SHENG Changdong, et al. X-ray photoelectron spectroscopy(XPS)investigation of nitrogen functionalities during coal char combustion in O2/CO2and O2/Ar atmospheres[J]. Energy&Fuels, 2011, 25(1):240-245.
[17]谢克昌.煤炭结构与反应性[M].北京:科学出版社, 2002.XIE K C. Coal structure and its reactivity[M]. Beijing:Science Press,2002.
[18]公旭中,郭占成,王志. Fe2O3对高变质程度脱灰煤热解反应性与半焦结构的影响[J].化工学报, 2009, 60(9):2321-2326.GONG Xuzhong, GUO Zhancheng, WANG Zhi. Effect of Fe2O3on pyrolysis reactivity and semi-coke structure of highly metamorphic deashing coal[J]. CIESC Journal, 2009, 60(9):2321-2326.
[19]王筱留.钢铁冶金学[M].北京:冶金工业出版社, 2006:200-250.WANG X L. Iron-making metallurgy[M]. Beijing:Metallurgy Industry Press, 2006:200-250.
[20] LIU Lina, LI Wenpei, XIONG Zesen, et al. Synergistic effect of iron and copper oxides on the formation of persistent chlorinated aromatics in iron ore sintering based on in situ XPS analysis[J]. Journal of Hazardous Materials, 2019, 366:202-209.
[21] YU Yang, WEI Huangzhao, YU Li, et al. Catalytic wet air oxidation of m-cresol over surface modified sewage sludge derived carbonaceous catalyst[J]. Catal. Sci. Technol., 2016(6):1085-1093.
[22]?ZTA?N A, OZTAS N A, YüRüM Y, et al. Effect of catalysts on the pyrolysis of turkish zonguldak bituminous coal[J]. Fuel&Energy Abstracts, 2000, 43(4):58.
[23] HOLSTEIN W L, BOUDART M. Transition metal and metal oxide catalysed gasification of carbon by oxygen, water, and carbon dioxide[J]. Fuel, 1983, 62(2):162-165.
[24] SADEZKY A, MUCKENHUBER H, GROTHE H, et al. Raman microspectroscopy of soot and related carbonaceous materials:Spectral analysis and structural information[J]. Carbon, 2005, 43(8):1731-1742.
[25]姚明宇,刘艳华,车得福.宜宾煤中氮的形态及其变迁规律研究[J].西安交通大学学报, 2003, 37(7):759-763.YAO Mingyu, LIU Yanhua, CHE Defu. Study on the form and change law of nitrogen in Yibin coal[J]. Journal of Xi'an Jiaotong University,2003, 37(7):759-763.
[26] WANG Cuiping, GONG Mingxin, LI Yongpeng, et al. Side reactions of coal tar pyrolysis products with different reduction states of iron-based oxygen carriers[J]. Energy&Fuels, 2018, 32(2).
[27]鞠付栋,陈汉平,杨海平,等.不同变质煤热解和气化中燃料氮的转化规律[J].煤炭转化, 2011, 34(3):21-26.JU Fudong, CHEN Hanping, YANG Haiping, et al. Conversion law of fuel nitrogen in pyrolysis and gasification of different metamorphic coals[J]. Coal conversion, 2011, 34(3):21-26.