升温速率对准东褐煤热解特性及煤焦孔隙结构的影响
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摘要
为了简化活性焦的制备工艺流程,降低其生产成本,同时拓宽准东褐煤利用途径,需要对准东褐煤热解过程进行更深入的研究。利用热重(TGA)技术考察了准东褐煤在不同升温速率(10,20,30,40和50℃/min)热解失重特性并采用等转化率法分析了其动力学参数,同时利用程序升温和快速热解在终温为800℃条件下制备出活性焦SC1和SC2。采用氮吸附仪(BET)获得煤焦的孔隙结构参数,利用红外吸收光谱仪(FT-IR)和拉曼仪光谱仪(Raman)分别获取煤焦大分子结构中的官能团和碳骨架结构信息。研究结果表明,基于热重法分析出准东褐煤热解动力学参数,活化能和指前因子变化范围为38. 89～229. 13 kJ/mol和108. 26～1. 18×109s-1。升温速率为30℃/min时,有足够热量促进煤焦内部有机结构分解生成大量挥发分,煤焦内部形成合理的温度梯度,阻碍了热缩聚反应造成孔隙阻塞,挥发分顺利释放促进了孔隙结构形成。程序升温热解焦SC1烧失率为46. 5%,比表面积为312. 91 m~2/g,孔容为0. 178 cm3/g,平均孔径为2. 271 nm;而快速热解焦SC2烧失率为37. 3%,比表面积达到424. 25 m~2/g,孔容为0. 189 cm3/g,平均孔径2. 342 nm,以微孔为主,结构参数明显好于SC1。快速热解炭化制备活性焦前驱体,促进煤焦生成大量无定形结构和缺陷结构,利于活化阶段微孔孔隙结构的构筑。
It is necessary to research thoroughly on the pyrolysis process of Zhundong lignite coal,in order to simplify the preparation process of activated coke,cut the production cost and improve the utilization of the lignite coal.The pyrolysis characteristics of Zhundong lignite coal were investigated by thermos-gravimetric analysis( TGA) at different heating rates of 10,20,30,40 and 50 ℃/min.Meanwhile,two kinds of activated carbons( SC1 and SC2) were respectively prepared at 800 ℃ by rapid-pyrolysis and temperature-programmed pyrolysis. To obtain the information of char on pore structure parameters,organic functional groups and carbon skeleton structures,the chars were characterized by BET,FT-IR and Raman.Results showed that the variation range of activation energy and pre-exponential factor were38.89-229.13 kJ/mol and 108.26-1.18×109 s-1,which were analyzed by TGA data for the pyrolysis of Zhundong lignite coal.The efficiency energy was transmitted to promote the decomposition of organic molecules and produce a large amount of volatile during the pyrolysis process with a heating rate of 30 ℃/min.Simultaneously,a reasonable temperature gradient inside the coal char prevented the pore structure blocking caused by thermal condensation reaction.Also,the smooth release of volatiles promoted the formation of pore structure.The char produced by temperature programmed pyrolysis had the specific surface area of 312.91 m~2/g,average pore volume of 0.178 cm3/g and average pore size of 2.271 nm at a burning-off rate of 46.5%.The char produced by rapid-pyrolysis had the specific surface area of 424.25 m~2/g,average pore volume of 0.189 cm3/g and average pore size of 2.342 nm at a burning-off rate of 37.3%.A large number of amorphous structures and defect structures were generated in precursor char during the rapid-pyrolysis process,which were conducive to the construction of microporous pore structure at activation stage.
It is necessary to research thoroughly on the pyrolysis process of Zhundong lignite coal,in order to simplify the preparation process of activated coke,cut the production cost and improve the utilization of the lignite coal.The pyrolysis characteristics of Zhundong lignite coal were investigated by thermos-gravimetric analysis( TGA) at different heating rates of 10,20,30,40 and 50 ℃/min.Meanwhile,two kinds of activated carbons( SC1 and SC2) were respectively prepared at 800 ℃ by rapid-pyrolysis and temperature-programmed pyrolysis. To obtain the information of char on pore structure parameters,organic functional groups and carbon skeleton structures,the chars were characterized by BET,FT-IR and Raman.Results showed that the variation range of activation energy and pre-exponential factor were38.89-229.13 kJ/mol and 108.26-1.18×109 s-1,which were analyzed by TGA data for the pyrolysis of Zhundong lignite coal.The efficiency energy was transmitted to promote the decomposition of organic molecules and produce a large amount of volatile during the pyrolysis process with a heating rate of 30 ℃/min.Simultaneously,a reasonable temperature gradient inside the coal char prevented the pore structure blocking caused by thermal condensation reaction.Also,the smooth release of volatiles promoted the formation of pore structure.The char produced by temperature programmed pyrolysis had the specific surface area of 312.91 m~2/g,average pore volume of 0.178 cm3/g and average pore size of 2.271 nm at a burning-off rate of 46.5%.The char produced by rapid-pyrolysis had the specific surface area of 424.25 m~2/g,average pore volume of 0.189 cm3/g and average pore size of 2.342 nm at a burning-off rate of 37.3%.A large number of amorphous structures and defect structures were generated in precursor char during the rapid-pyrolysis process,which were conducive to the construction of microporous pore structure at activation stage.
引文
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[19]韩峰,张衍国,蒙爱红,等.云南褐煤结构的FTIR分析[J].煤炭学报,2014,39(11):2293-2299.HAN Feng,ZHANG Yanguo,MENG Aihong,et al.FTIR analysis of Yunnan lignite[J]. Journal of China Coal Society,2014,39(11):2293-2299.
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[23] SHENG Changdong.Char structure characterized by Raman spectroscopy and its correlations with combustion reactivity[J]. Fuel,2007,86(15):2316-2324.
[24] SFORNA M C,ZUILEN M A V,PHILIPPOT P.Structural characterization by Raman hyperspectral mapping of organic carbon in the3.46 billion-year-old Apex chert,Western Australia[J].Geochimica et Cosmochim Acta,2014,124(1):18-33.
[2]杨丽,陈贵峰.洁净煤技术评价模型及应用[J].煤炭学报,2007,32(6):630-633.YANG Li,CHEN Guifeng. The clean coal technology model and its application[J]. Journal of China Coal Society,2007,32(6):630-633.
[3] SHU Geping,ZHANG Yuzhuo.Research on the maceral characteristics of Shenhua coal and efficient and directional direct coal liquefaction technology[J].International Journal of Coal Science&Technology,2014,1(1):46-55.
[4]张守玉,吕俊复,岳光溪,等.煤种及炭化条件对活性焦孔隙结构的影响[J].煤炭学报,2003,28(2):167-172.ZHANG Shouyu,LJunfu,YUE Guangxi,et al. The effects of coal type and carbonization condition on the porous texture of activated chare derived[J]. Journal of China Coal Society,2003,28(2):167-172.
[5] BHATIA S K,PERLMUTTER D D.A random pore model for fluidsolid reactions:I Isothermal,kinetic control[J]. AICHE Journal,1980,26(3):379-386.
[6]刘振宇,郑经堂,王茂章,等.多孔炭的纳米结构及其解析[J].化学进展,2001,13(1):10-18.LIU Zhengyu,ZHENG Jingtang,WANG Maozhang,et al. Nanostructure and analysis of porous carbons[J].Progress in Chemistry,2001,13(1):10-18.
[7] GUO Jia,CHONG LuaAik. Microporous activated carbons prepared form palm shell by thermal activation and their application to sulfur dioxide adsorption[J].Journal of Colloid and Interface Science,2002,251(2):242-247.
[8] SUN Fei,GAO Jihui,LIU Xin,et al. A systematic investigation of SO2 removal dynamics by coal-based activated cokes:The synergic enhancement effect of hierarchical pore configuration and gas components[J]. Applied Surface Science,2015,357(B):1895-1901.
[9]张守玉,王洋,吕俊复,等.煤种及炭化条件对活性焦脱硫性能的影响[J].燃烧科学与技术,2003,9(5):430-433.ZHANG Shouyu,WANG Yang,LJunfu,et al. Effects of coal type and carbonization condition on the desulfurization capability of activated char[J]. Journal of Combustion Science and Technology,2003,9(5):430-433.
[10]刘冬冬,高继慧,吴少华,等.闪热解对烟煤焦结构及活化过程孔隙生成的影响[J].煤炭学报,2016,41(11):2867-2875.LIU Dongdong,GAO Jihui,WU Shaohua,et al.Effect of flash pyrolysis on bituminous char structure and pore development during activation[J]. Journal of China Coal Society,2016,41(11):2867-2875.
[11] SENNECA O,URCIUOLO M,CHIRONE R,et al.An experimental study of fragmentation of coals during fast pyrolysis at high temperature and pressure[J].Fuel,2011,90(9):2931-2938.
[12] TIAN Bin,QIAO Yingyun,TIAN Yuanyu,et al.Investigation on the effect of particle size and heating rate on pyrolysis characteristics of a bituminous coal by TG-FTIR[J]. Journal of Analytical and Applied Pyrolysis,2016,121:376-386.
[13] KISSINGER H E.Reaction kinetics in differential thermal analysis[J].Analytical Chemistry,2002,29(11):1702-1709.
[14]江国栋,魏利平,滕海鹏,等.基于热重法的准东煤等转化率热解动力学模型[J].化工学报,2017,68(4):1415-1421.JIANG Guodong,WEI Liping,TENG Haipeng,et al.A kinetic model based on TGA data for pyrolysis of Zhundong coal[J].Journal of Chemical Industry and Engineering(China),2017,68(4):1415-1421.
[15] TANNER J,KABIR K B,MULLER M,et al.Low temperature entrained flow pyrolysis and gasification of a Victorian brown coal[J].Fuel,2015,154(6):6364-6367.
[16] OKUMURA K,HANAOKA T,SAKANISHI K. Effect of pyrolysis condition on gasification reactivity of woody biomass-derived char[J]. Proceeding of the Combustion Institute,2009,32(2):2013-2020.
[17]段春雷.低中变质程度煤的结构特性及热解过程中甲烷、氢气的生成机理[D].太原:太原理工大学,2007,14-16.DUAN Chunlei. Structure characteristics of low-middle rank coal and generation mechanisms of methane and hydrogen during pyrolysis[D]. Taiyuan,Taiyuan University of Mining and Technology,2007:14-16.
[18]王俊宏,常丽萍,谢克昌.西部煤的热解特性及动力学研究[J].煤炭转化,2009,32(3):1-5.WANG Hongjun,CHANG Liping,XIE Kechang.Study on the pyrolysis and kinetics of coal of western China[J]. Coal Conversion,2009,32(3):1-5.
[19]韩峰,张衍国,蒙爱红,等.云南褐煤结构的FTIR分析[J].煤炭学报,2014,39(11):2293-2299.HAN Feng,ZHANG Yanguo,MENG Aihong,et al.FTIR analysis of Yunnan lignite[J]. Journal of China Coal Society,2014,39(11):2293-2299.
[20] LIN Xiongchao,WANG Caihong,KEIKO Ideta. Insights into the functional group transformation of a Chinese brown coal during slow pyrolysis by combining various experiments[J]. Fuel,2014,118:257-364.
[21] RHIM Y R,ZHANG D,FAIRBROTHER D H,et al. Changes in electrical and microstructural properties of microcrystalline cellulose as function of carbonization temperature[J]. Carbon,2010,48(4):1012-1024.
[22] 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.
[23] SHENG Changdong.Char structure characterized by Raman spectroscopy and its correlations with combustion reactivity[J]. Fuel,2007,86(15):2316-2324.
[24] SFORNA M C,ZUILEN M A V,PHILIPPOT P.Structural characterization by Raman hyperspectral mapping of organic carbon in the3.46 billion-year-old Apex chert,Western Australia[J].Geochimica et Cosmochim Acta,2014,124(1):18-33.