水蒸气对煤焦低氧体积分数燃烧砷释放的影响
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摘要
煤燃烧过程中痕量元素排放的研究已成为燃煤污染中的一个新兴前沿领域。特别是一些易挥发元素或化合物,它们排放进入大气,成为环境污染的一个重要来源。其中最易挥发的痕量元素砷引起人们的广泛关注。选取清水沟煤焦,利用自制的恒温燃烧实验台,研究了5%氧体积分数下煤焦在800,1 000和1 200℃燃烧过程中水蒸气对砷释放的影响。通过改变不同停留时间,并进一步探究水蒸气在不同温度、不同粒径下对砷释放特性的影响,得出煤焦燃烧过程中砷释放比例随时间的变化曲线。实验结果表明:水蒸气对煤和煤焦中砷释放的影响是同步的,水蒸气主要是与焦炭发生气化反应促进了煤焦中砷释放进而影响了煤中砷释放;燃烧气氛中水蒸气对煤焦燃烧砷释放具有一定的促进作用,原因是低氧下水蒸气与煤焦发生了气化反应,提高了砷的释放速率并增加最终的释放比例,但促进作用随着水蒸气体积分数的增加逐渐减弱;不同温度下,水蒸气对煤焦燃烧砷释放的促进存在差异,1 000℃下水蒸气对煤焦燃烧砷释放的促进作用较800℃和1 200℃下更明显;在同一条件(温度和气氛)下,煤焦粒径越小,砷的最终释放比例越大,且砷释放峰值对应的温度随着粒径的减小向低温区移动;气氛中含20%水蒸气时,煤焦燃烧砷释放的表观活化能和频率因子均大于气氛中不含水蒸气。
The study of trace element emissions has become a new frontier field in coal combustion pollution.Especially some volatile elements or compounds which are discharged into the atmosphere become an important source of environmental pollution.The most volatile trace element arsenic has attracted wide attention.Qingshuigou char was selected for investigating the effect of steam on the release of arsenic in combustion at 800,1 000 and 1 200 ℃ with 5% oxygen concentration in a customized isothermal combustion system.By changing the residence time,and further exploring the influence of steam on the arsenic release characteristics at different tem-peratures and particle sizes,the variation curve of arsenic release ratio with time during coal char combustion was obtained.The results show that the effect of steam on arsenic release from coal and coal char is synchronous,and the gasification reaction between steam and coke promotes arsenic release from coal char and then affects arsenic release from coal char.The presence of steam in the combustion atmosphere can promote the release of arsenic during the coal char combustion.The cause is that the steam reacted with coal char and accelerated the coal com-bustion. The promotion effect decreases with the increase of steam concentration.The promotion effect of steam on the release of arsenic at 1 000 ℃ is more obvious than that at 800 and 1 200 ℃.Under the same temperature and atmosphere,the smaller the particle size is,the greater the final release ratio of arsenic is.The temperature corre-sponding to the release peak of arsenic will move along the low temperature region with the decrease of particle size.The apparent activation energy and frequency factor of arsenic release with 20% steam are greater than those without steam.
The study of trace element emissions has become a new frontier field in coal combustion pollution.Especially some volatile elements or compounds which are discharged into the atmosphere become an important source of environmental pollution.The most volatile trace element arsenic has attracted wide attention.Qingshuigou char was selected for investigating the effect of steam on the release of arsenic in combustion at 800,1 000 and 1 200 ℃ with 5% oxygen concentration in a customized isothermal combustion system.By changing the residence time,and further exploring the influence of steam on the arsenic release characteristics at different tem-peratures and particle sizes,the variation curve of arsenic release ratio with time during coal char combustion was obtained.The results show that the effect of steam on arsenic release from coal and coal char is synchronous,and the gasification reaction between steam and coke promotes arsenic release from coal char and then affects arsenic release from coal char.The presence of steam in the combustion atmosphere can promote the release of arsenic during the coal char combustion.The cause is that the steam reacted with coal char and accelerated the coal com-bustion. The promotion effect decreases with the increase of steam concentration.The promotion effect of steam on the release of arsenic at 1 000 ℃ is more obvious than that at 800 and 1 200 ℃.Under the same temperature and atmosphere,the smaller the particle size is,the greater the final release ratio of arsenic is.The temperature corre-sponding to the release peak of arsenic will move along the low temperature region with the decrease of particle size.The apparent activation energy and frequency factor of arsenic release with 20% steam are greater than those without steam.
引文
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[14] YAN R,GAO R X.Multi-scale enveloping spectrogram for vibration analysis in bearing defect diagnosis[J]. Tribology International,2009,42(2):293-302.
[15] MAHULI S,AGNIHOTRI R,CHAUK S,et al.Mechanism of arsenic sorption by hydrated lime[J]. Environmental Science&Technology,1998,31(11):3226-3231.
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[17] TSENG R L.Physical and chemical properties and adsorption type of activated carbon prepared from plum kernels by Na OH activation[J].Journal of Hazardous Materials,2007,147(3):1020.
[18]刘慧敏,王春波,张月,等.温度和赋存形态对燃煤过程中砷迁移和释放的影响[J].化工学报,2015,66(11):4643-4651.LIU Huimin,WANG Chunbo,ZHANG Yue,et al.Effect of temperature and occurrence form of arsenic on its migration and volatilization during coal combustion[J]. Journal of Chemical Industry and Engineering,2015,66(11):4643-4651.
[19]雷鸣,黄星智,王春波.O2/CO2气氛下CO2和H2O气化反应对煤及煤焦燃烧特性的影响[J].燃料化学学报,2015,43(12):1420-1426.LEI Ming,HUANG Xingzhi,WANG Chunbo.Effect of CO2and H2O gasification on the combustion characteristics of coal and char under O2/CO2atmosphere[J].Journal of Fuel Chemistry and Technology,2015,43(12):1420-1426.
[20]邹晓鹏,盛羽静,陆海峰,等.粒径对不同煤阶煤焦气化反应活性的影响研究[J].燃料化学学报,2017,45(4):408-417.ZOU Xiaopeng,SHENG Yujing,LU Haifeng,et al.Effect of particle size on gasification of char with different coal ranks[J]. Journal of Fuel Chemistry and Technology,2017,45(4):408-417.
[21]周俊虎,匡建平,周志军,等.黑液水煤浆焦C-H2O气化反应特性研究[J].中国电机工程学报,2007,27(14):41-45.ZHOU Junhu,KUANG Jianping,ZHOU Zhijun,et al. Research on C-H2O gasification reaction characteristic of coal black liquor slurry char[J].Proceedings of the CSEE,2007,27(14):41-45.
[22]冯万国,楼国锋,王淦.不同气氛下焦炭燃烧动力学实验研究[J].化工进展,2017,36(2):487-493.FENG Wanguo,LOU Guofeng,WANG Gan. Experiment investigation on combustion characteristics and kinetics of coke under different atmosphere[J]. Chemical Industry and Engineering Progress,2017,36(2):487-493.
[23]韩军,王光辉,徐明厚,等.煤燃烧和热解过程中As和Se的挥发实验[J].华中科技大学学报(自然科学版),2009,37(5):113-115.HAN Jun,WANG Guanghui,XU Minghou,et al.Experimental study of As and Se’s vaporization during coal combustion and pyrolysis[J]. Journal of Huazhong University of Science and Technology(Natural Science Edition),2009,37(5):113-115.
[24]刘国伟,董芃,韩亚芬,等.富氧条件下煤燃烧特性的热重分析实验研究[J].哈尔滨工业大学学报,2011,43(1):104-108.LIU Guowei,DONG Peng,HAN Yafen,et al. Experimental study on combustion characteristics of coals under enriched-oxygen condition by thermo-gravimetric analysis[J]. Journal of Harbin Institute of Technology,2011,43(1):104-108.
[2]邹潺,王春波,郭辉,等.燃煤过程中砷的赋存形态及其挥发特性[J].化工学报,2018,69(4):1670-1677.ZOU Chan,WANG Chunbo,GUO Hui,et al.Volatilization characteristics and mode of occurrence of arsenic during coal combustion[J].Journal of Chemical Industry and Engineering,2018,69(4):1670-1677.
[3]周家平.气氛对煤燃烧和SO2/NOx迁移的机理及动力学特性影响的研究[D].重庆:重庆大学,2010:27-49.ZHOU Jiaping.Research of ambience effect on mechanism and kinetics of coal cobustion and SO2/NOxtransfer[D]. Chongqing:Chongqing University,2010:27-49.
[4]姜中孝,段伦博,陈晓平.水蒸气对O2/CO2气氛下煤焦燃烧特性的影响[J].煤炭学报,2013,38(3):466-472.JIANG Zhongxiao,DUAN Lunbo,CHEN Xiaoping. Effect of steam on char combustion characteristics under a O2/CO2atmosphere[J].Journal of China Coal Society,2013,38(3):466-472.
[5] HECHT E S,SHADDIX C R,GEIER M,et al. Effect of CO2and steam gasification reactions on the oxy-combustion of pulverized coal char[J]. Combustion&Flame,2012,159(11):3437-3447.
[6]王春波,李超,雷鸣.水蒸气对煤焦恒温下燃烧特性的影响[J].中国电机工程学报,2013,33(32):8-13.WANG Chunbo,LI Chao,LEI Ming. Effects of water vapor on the isothermal combustion characteristics of coal char[J]. Proceedings of the CSEE,2013,33(32):8-13.
[7] YAN R,GAUTHIER D,FLAMANT G.Possible interactions between As,Se,and Hg during coal combustion[J]. Combustion&Flame,2000,120(1):49-60.
[8]王贺飞,王春波,邹潺,等.燃煤过程中水蒸气对砷释放特性的影响[J].洁净煤技术,2017,23(4):53-57,62.WANG Hefei,WANG Chunbo,ZOU Chan,et al. Effect of steam on arsenic volatile characteristics during coal combustion[J]. Clean Coal Technology,2017,23(4):53-57,62.
[9] WANG C,LIU X W,LI D,et al.Effect of H2O and SO2on the distribution characteristics of trace elements in particulate matter at high temperature under oxy-fuel combustion[J]. International Journal of Greenhouse Gas Control,2014,23,51-60.
[10] WANG C,XING Z,JIA L,et al. Sintering of limestone in calcination/carbonation cycles[J]. Industrial&Engineering Chemistry Research,2014,53(42):16235-16244.
[11]邹潺,王春波,王贺飞,等.燃煤过程中砷挥发特性及动力学特性的研究[J].动力工程学报,2017,37(5):349-355.ZOU Chan,WANG Chunbo,WANG Hefei,et al. Volatilization and kinetic charactistics of arsenic during coal combustion[J].Chinese Journal of Power Engineering,2017,37(5):349-355.
[12] MARTN-GULLN I,ASENSIO M,FONT R,et al. Steam-activated carbons from a bituminous coal in a continuous multistage fluidized bed pilot plant[J].Carbon,1996,34(12):1515-1520.
[13] JAS'IEN KO-HAAT M,KEDZIOR K.Comparison of molecular sieve properties in microporous chars from low-rank bituminous coal activated by steam and carbon dioxide[J].Carbon,2005,43(5):944-953.
[14] YAN R,GAO R X.Multi-scale enveloping spectrogram for vibration analysis in bearing defect diagnosis[J]. Tribology International,2009,42(2):293-302.
[15] MAHULI S,AGNIHOTRI R,CHAUK S,et al.Mechanism of arsenic sorption by hydrated lime[J]. Environmental Science&Technology,1998,31(11):3226-3231.
[16] LINARES-SOLANO A,MARTIN-GULLON I,LECEA S M D,et al.Activated carbons from bituminous coal:Effect of mineral matter content[J].Fuel,2000,79(6):635-643.
[17] TSENG R L.Physical and chemical properties and adsorption type of activated carbon prepared from plum kernels by Na OH activation[J].Journal of Hazardous Materials,2007,147(3):1020.
[18]刘慧敏,王春波,张月,等.温度和赋存形态对燃煤过程中砷迁移和释放的影响[J].化工学报,2015,66(11):4643-4651.LIU Huimin,WANG Chunbo,ZHANG Yue,et al.Effect of temperature and occurrence form of arsenic on its migration and volatilization during coal combustion[J]. Journal of Chemical Industry and Engineering,2015,66(11):4643-4651.
[19]雷鸣,黄星智,王春波.O2/CO2气氛下CO2和H2O气化反应对煤及煤焦燃烧特性的影响[J].燃料化学学报,2015,43(12):1420-1426.LEI Ming,HUANG Xingzhi,WANG Chunbo.Effect of CO2and H2O gasification on the combustion characteristics of coal and char under O2/CO2atmosphere[J].Journal of Fuel Chemistry and Technology,2015,43(12):1420-1426.
[20]邹晓鹏,盛羽静,陆海峰,等.粒径对不同煤阶煤焦气化反应活性的影响研究[J].燃料化学学报,2017,45(4):408-417.ZOU Xiaopeng,SHENG Yujing,LU Haifeng,et al.Effect of particle size on gasification of char with different coal ranks[J]. Journal of Fuel Chemistry and Technology,2017,45(4):408-417.
[21]周俊虎,匡建平,周志军,等.黑液水煤浆焦C-H2O气化反应特性研究[J].中国电机工程学报,2007,27(14):41-45.ZHOU Junhu,KUANG Jianping,ZHOU Zhijun,et al. Research on C-H2O gasification reaction characteristic of coal black liquor slurry char[J].Proceedings of the CSEE,2007,27(14):41-45.
[22]冯万国,楼国锋,王淦.不同气氛下焦炭燃烧动力学实验研究[J].化工进展,2017,36(2):487-493.FENG Wanguo,LOU Guofeng,WANG Gan. Experiment investigation on combustion characteristics and kinetics of coke under different atmosphere[J]. Chemical Industry and Engineering Progress,2017,36(2):487-493.
[23]韩军,王光辉,徐明厚,等.煤燃烧和热解过程中As和Se的挥发实验[J].华中科技大学学报(自然科学版),2009,37(5):113-115.HAN Jun,WANG Guanghui,XU Minghou,et al.Experimental study of As and Se’s vaporization during coal combustion and pyrolysis[J]. Journal of Huazhong University of Science and Technology(Natural Science Edition),2009,37(5):113-115.
[24]刘国伟,董芃,韩亚芬,等.富氧条件下煤燃烧特性的热重分析实验研究[J].哈尔滨工业大学学报,2011,43(1):104-108.LIU Guowei,DONG Peng,HAN Yafen,et al. Experimental study on combustion characteristics of coals under enriched-oxygen condition by thermo-gravimetric analysis[J]. Journal of Harbin Institute of Technology,2011,43(1):104-108.
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