升温速率对生物质热解的影响

第36卷第2期燃料化学学报Vol 36 No. 208年4月Joumal of Fuel Chemistry and Technol文章编号:0253-2409(2008)0223204升温速率对生物质热解的影响任强强,赵长遂(东南大学洁净煤发电及燃烧技术教育部重点实验室,江苏南京2009%6)关键词:生物质;热解特性;升温速率;气体产物中图分类号:TK6文献标识码:AEffect of heating rate on biomass pyrolysisREN Qiang-qiang, ZHAO Chang-suiKey Laboratory of Clean Coal Power Generation and Combustion Technology of Ministry of Education, Southeast University,Nanjing 210096, China)Abstract: The pyrolysis behavior of three typical agricultural residues including rice husk, rice straw and wheatstraw, was studied at different heating rates(15 C/min, 40 C/min and 100 C/min)in a dynamic nitrogen flowof 80 mL/min by TG analysis coupled with Fourier Transform Infrared Spectroscopy( FT-IR). The variousgaseous products released during biomass pyrolysis were examined. The kinetic parameters under differentheating rates were acquired by kinetics analysis. The correlation coefficients are above 0. 99. The results showthat as heating rate increases the tG curve shifts to low temperature zone and the peak of dtg curve goes to lowtemperature area accordingly, but the total weight loss and activation energy of pyrolysis fluctuate little. Thereleasing behavior of gaseous products during pyrolysis of the three samples is similar. CO, CO2, H2O, CH, andorganics are the main gaseous products during biomass pyrolysis. When the heating rate increases, the yield ofgaseous products released increases, so does the releasing rateKey words: biomass; pyrolysis characteristic; heating rates; TGA-FTIR; gaseous products稻壳、稻秆及麦秆是中国主要的农业废弃物,如力学及热解气体产物的析出规律进行实时在线何综合、有效地利用这些农业废弃物进行资源化研分析。究显得十分必要。热解是热化学转化中最为基本的实验部分过程,是气化、液化及燃烧过程的初始和伴生反应对热解的分析有助于热化学转化过程控制及高效转1.1实验仪器实验采用的仪器为法国TGA92型常压热重分析仪及德国 BRUKER公司 VECTOR化工艺的开发。目前,国内外对生物质及其组分的22型傅里叶变换红外光谱仪。热解已有大量的研究6,但对中国主要的农业废1.2实验条件实验选用稻壳、稻秆及麦秆三种南弃物稻壳、稻秆及麦秆的研究较少。本研究利用热京生物质,其基本性质见表1。重和红外联用技术深入研究了升温速率对三种典型生物质热解气体产物的影响,并对生物质的热解动表1生物质的元素分析及工业分析Table 1 Proximate and ultimate analyses of biomassProximate analysis w,/%Ultimate analysis w,/%MAFCCHNS/Mkg-Rice husk9.8512.3663.39144038.244.1134.720.580.1414.28Rice straw6.8810.5878.544.0037.814.7834.630.710.0913.59Wheat straw8148:90n204109245721343480600251357每次实验取样品7mg粒径小于0.2mm;高纯为室温-800r停留10min采用三种升温速率氮气作为载气流量为80mL/min;热分析温度范围即15中国煤化工/min。实验时热CNMHG收稿日期:20070804;修回日期:2007-11-27联系作者:赵长遂,Tel:02583793453,Fax:02583793453,E-mail:rizhao@seu.edu.cn作者简介:任强强(1983-),男,江苏宿迁人,硕士研究生,从事生物质能利用研究。Emal:rengo2006@163.com第2期任强强等:升温速率对生物质热解的影响天平自动记录质量的变化信号。每个实验完成后,及麦秆明显失重,有大量气体(包括焦油)析出,物做一个相同条件的空白实验以消除系统误差。TG料质量急剧下降。研究表明3,此阶段发生的热的出囗气体通过导管引人到FrR的气体池中实解是纤维素、半纤维素及木质素等生物质有机组成时跟踪检测,并获得失重时间(与温度对应)-析出气成分热解叠加的结果。纤维素主要热分解区域在体的红外光谱分析结果,以期同时获得样品的热失250℃~50℃,热解后碳量较少,热解速率很快;而重特性和析出特性木质素较难热解,热解速率在400℃以后出现峰2结果与讨论值。。在热解温度高于500℃,半纤维素和纤维素2.1生物质TG.DTG分析的热分解基本结束,此时以木质素热解为主。由于21.1热解特性实验图1为三种生物质在升温木质素热解时形成较多的碳因此稻壳、稻秆及麦速率为15/m、40℃/mim及100m下的热秆热失重曲线和热解速率曲线在高温区趋于平缓。解曲线。由图1可知,在200℃~500℃,稻壳、稻秆8至3Temperature n/C800Temperature t℃图I不同升温速率下生物质热解特性曲线Figure 1 TG-DTG curves of biomass pyrolysis at different heating rates,a:l5℃/mn;b:40℃/mn;c:100/min(a): rice husk;(b): rice husk;(c): rice straw:(d): wheat straw由图1还可知随着升温速率的升高,热解速率曲线向低温区偏移达到最高热解速率(-dw/dr)所对应的温度向低温区偏移。不同升温速率下三种式中:m为样品初始质量、mr为实验结束时的质量生物质达到最大热解速率时所对应的温度有所不同,m为样品任一时刻的质量。根据质量作用定律可以稻壳为320℃~350℃,稻秆为295℃-325℃,麦秆得到样品热解速率方程:为发生在300℃-35℃。这主要是由于三种生物质心-Lf1(2)化学组成不同,导致热解速率不同式中中国煤化工212热解动力学参数根据热解曲线,可以求解CNMHG生物质热解的反应动力学参数。样品在实验中的总-E/RT质量变化为式中:A为频率因子、E为活化能R为气体常数、T为燃料化学学报第36卷绝对温度。EX则有研究表明”,秸秆类生物质的热解反应可视为级反应。将式(3)代入式(2)积分并整理得(:Y=a+bx(5)-10)=141-2)-R()根据实验结果,可以计算出样品不同工况下XY值进而求得a、b值,即可求得反应的表观活化能E式中d为升温速率,亦。令y=h[、l(1-g)和频率因子A,计算结果见表2。各拟合方程的相关系数都大于0.99,说明线性回归比较合理表2生物质的热解动力学参数Table 2 Kinetic parameters of biomass pyrolysisSample Heating rate/Cmin" t/CFitting equationE/kJ.mol-1A/minRice husk15238~366Y=3.4873-5878X-0.994248.883.60×10°242-375Y=3.3589-5988X-0.995749.795.91×10°236~361Y=1.9917-6649X0.998955.298.26×10°Rice straw234-346Y=2.5464-6292X-0.992142.751.48×10°239-352Y=4.3705-5142X0.990151.107.52×10°216-336Y=2.2939-6146X522.10×10236-358Y=1.5199-6935X-0.997749.635.72x103232~363Y=2.8370-6127X-0.997350.945.17×10°217~356Y=2.7531-5969X-0.9982.2生物质热解FTR分析体没有红外光谱吸收峰,因此,利用傅里叶红外光谱热解产物分析图2分别为稻壳稻秆及麦不能检测出这些气体成分。但是H2是生物质热杆在40℃/mn升温速率下热解气体产物的典型谱解的重要气体组成作者将在以后利用质谱检测分图。由图2可知CO2CO0H2OCH及有机物是生析。下面以稻壳为例,深人了解升温速率对生物质热物质热解主要气体产物。有机物主要是烃类、醛类醇类羧酸类等大分子物质。此外H2N2及O2等气解气体产物的影响。acids C=Oacids c-o alkanesCo月HHOCH, coW\40001000wavenumber dcmWavenumber a/cm-l图2生物质热解产物谱图Figure 2 Typical IR spectra of the products from three biomass pyrolysis at 40 C/min(a): rice husk(34℃);(b): nce straw(37℃);(e): wheat straw(323℃)222升温速率对热解气体产物影响图3为稻壳出值对应的温度提高分别为350℃415℃及458℃在升温速率l5℃/mn40℃/min及00℃/min下热而在升温速率15℃/mn40℃/min及100℃/min下解时主要气体产物的析出过程。由图3可知稻壳热CH4达到最大析出值对应的温度为437℃、600℃及解过程中,水的析出有两个峰,CO2、CO及CH4的气458℃,并不是随着升温速率提高而相应增加,这与体释放都为单峰曲线。1中国煤化工高于200℃时,CO2的析出量随着热解温度的升CNMHGJ IR吸收曲线有高而明显增加,达到最大值后迅速减小高于00相似的释放规律,不同的是CO及有机物的释放温度时析出量很少。随着升温速率升高,CO2达到最大析稍高大部分在300℃以上析出。第2期任强强等:升温速率对生物质热解的影响0.30§025300405002005000意0004200400600800Temperature t/CTemperature t/℃Temperature t℃0040.1500300200l000配矿图3稻壳热解气体产物的析出过程■:15℃/min;o:40℃/min;▲:100℃/min结语稻秆由于含有较高的挥发分热解达到最大热解速率生物质热解主要发生在200℃~500℃。随着升时所对应的温度低于稻壳及麦秆。温速率的升高样品热解的TG曲线向低温区偏移,CO2、CO、H2OCH4及有机物是生物质热解的主DrG曲线峰值位置也相应地移向低温区。稻壳、稻秆要气体产物;随着升温速率提高,气体产物析出量增及麦秆热解达到最大热解速率时所对应的温度分别加,释放的速率加快;CO2及H2O的释放温度较低,为320℃~350℃、295℃~325℃、300℃~335℃。CO、CH4及有机物的释放温度稍高。参考文献:[]杨海平陈汉平,晏蓉,张世红,郑楚光油棕废弃物热解的TGFR分析[].燃料化学学报,200,34(3):309314(YANG Hai-ping, CHEN Han-ping, YAN Rong, ZHANG Shi-hong, ZHENG Chu-guang. TG-FTIR analysis of palm oil wastes pyrolysis[ J]Joumal of Fuel Chemistry and Technology, 2006, 34(3): 309-314.)[2]程世庆,尚琳琳,张海清生物质的热解过程及其动力学规律(刀].煤炭学报,200,031(4):501-505( CHENG Shi-qing, SHANG Lin-lin, ZHANG Hai-qing. The pyrolysis characteristics of biomass and its dynamics law[J]. Joumal of China CoalSociety,2006,31(4):501505.)[3]段佳,罗永浩,晏乃强,陈伟,陆方,王清成.生物质气化再燃特性实验研究[].燃料化学学报,2007,35(2):245248( DUAN Jia, LUO Yong-hao, YAN Nai-qiang, CHEN Yi, LU Fang, WANG Qing-cheng. Experimental study on characteristics of biomassgasification-reburning[J]. Joumal of Fuel Chemistry and Technology, 2007, 35(2): 245-248.)[4] WORASUWANNARAK N, SONOBE T, TANTHAPANICHAKOON W. Pyrolysis behaviors of rice straw, rice husk, and comeob by TG-MStechnique[ J]. J Anal Appl Pyrolysis, 2007, 78(2):265-271[5] YANG H P, YAN R, CHEN HP, LFE DH, ZHENGCG. Caracteristics o hemicellulose, cellulose and lignin pyrolysis[J]. Fuel, 21, 8(12-B): I8l-17886]姚燕,王树荣,郑赟,骆仲泱,岑可法.基于热红联用分析的木质素热裂解动力学研究[J燃烧科学与技术,200,13(1):5054(YAO Yan, WANG Shu-rong, ZHENG Yun, LUO Zhong-yang, CEN Ke-fa. Kinetic research of lignin pyrolysis by TGA-FTIR analysis[ J]Joumal of Combustion Science and Technology, 2007, 13(1): 50-54.)[7 ANTAL M J Jr, VARHEGYI G. Cellulose pyrolysis kinetics: The current states of knowledge[J]. Ind Eng Chem Res, 1995. 34(3):703-717[8]廖艳芬,王树荣,马晓茜.纤维素热裂解反应机理及中间产物生成过程模拟研究[刀].燃料化学学报,2006,34(2):184190.LIAO Yan-fen, WANG Shu-rong, MA Xiao-qian. Simulation of cellulose pyrolysis mechanism and formation process of intermediate products[]. Jourmal of Fuel Chemistry and Technology, 2006, 34(2): 184-190.)[9]赖艳华,吕明新,马春元,施明恒.秸秆类生物质热解特性及其动力学研究[学棉,2002.23(2)203-206.( LAI Yan-hua, LU Ming-xin, MA Chun-yuan, SHI Ming-heng. Study on the中国煤化工 s process agriculturalresidues[ J]. Acta Energiae Solaris Sinica, 2002, 23(2):203-206[10] MOGHTADERI B, MEESRI C, WALL T F. Pyrolytic characteristics of blendCNMHG,83(6):745-750.[11] HAYKIRL-ACMA H, YAMAN S, KUCUKBAYRAK S. Ef o heating rate n the pyrdysis yields o rapeseed[]. Renewable Energy, 216, 31(6):&IB-8IQ[12] YAN R, YANG H P, CHIN T, LIANG D T, CHEN H P, ZHENG C G. Influence of temperature on the distribution of gaseous productsfrom pyrolyzing palm oil wastes[ J]. Combust Flame, 2005, 142(1-2):24-32