燃煤锅炉SCR对颗粒物排放特性影响
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摘要
我国电厂多数采用选择性催化还原(SCR)脱硝技术降低电厂NOx排放,目前关于电厂中SCR对颗粒物排放特性的影响研究十分匮乏。本研究对一热电联产锅炉SCR前后颗粒物和飞灰进行取样,分析颗粒物质量粒径分布以及化学成分。采用计算机控制扫描电镜(CCSEM)对飞灰进行分析,获得颗粒物单颗粒成分。结果表明SCR前后PM10均呈双峰分布。经过SCR后,PM0.21浓度降低约62%(质量),而PM_(0.21-1)浓度升高19%(质量);PM1中SO_2相对含量增加约6%(质量),SiO_2和Al_2O_3相对含量降低,而CaO相对含量没有明显变化;经过SCR后,PM_(1-10)浓度降低约17%(质量),成分基本没有变化,但是颗粒成分变得更均一,说明经过SCR后,PM_(1-10)发生交互作用。因此经过SCR后PM_(1-10)浓度降低不仅由于颗粒物在SCR中发生沉积,更有可能是颗粒物之间交互作用导致。
Selective catalytic reduction(SCR) technology is usually used in coal combustion power plant to reduce NOx emission. The effects of SCR De NOx on PM emission are still unclear. In this work, PM and fly ash before and after SCR was sampled. Particle size distribution(PSD) and chemical composition of PM was analyzed. Computercontrolled scanning electron microscope(CCSEM) was used to analyze the fly ash and obtain the composition distribution property of individual PM particles. The effect of SCR De NOx on PM emission characteristic and its mechanism was investigated. The results show that PM is bimodal distribution before and after SCR. After the flue gas flows through the SCR, PM0.21 decreases 62%(mass) and PM_(0.21-1) increases 19%(mass). The relative amount of SO_2 in PM1 increases 6%(mass) and SiO_2 and Al_2 O_3 decrease, while the variation of CaO is insignificant after SCR. The amount of PM_(1-10) decreases 17%(mass) after SCR. Insignificant change of its chemical composition is observed after SCR. However, the chemical composition distribution of individual PM_(1-10) particle becomes more homogeneous after SCR. It suggests that significant interaction between PM10 has happened in or after SCR. Therefore, decrease of PM_(1-10) after SCR is not only because of PM10 deposition in the SCR, but also because of particle interaction.
Selective catalytic reduction(SCR) technology is usually used in coal combustion power plant to reduce NOx emission. The effects of SCR De NOx on PM emission are still unclear. In this work, PM and fly ash before and after SCR was sampled. Particle size distribution(PSD) and chemical composition of PM was analyzed. Computercontrolled scanning electron microscope(CCSEM) was used to analyze the fly ash and obtain the composition distribution property of individual PM particles. The effect of SCR De NOx on PM emission characteristic and its mechanism was investigated. The results show that PM is bimodal distribution before and after SCR. After the flue gas flows through the SCR, PM0.21 decreases 62%(mass) and PM_(0.21-1) increases 19%(mass). The relative amount of SO_2 in PM1 increases 6%(mass) and SiO_2 and Al_2 O_3 decrease, while the variation of CaO is insignificant after SCR. The amount of PM_(1-10) decreases 17%(mass) after SCR. Insignificant change of its chemical composition is observed after SCR. However, the chemical composition distribution of individual PM_(1-10) particle becomes more homogeneous after SCR. It suggests that significant interaction between PM10 has happened in or after SCR. Therefore, decrease of PM_(1-10) after SCR is not only because of PM10 deposition in the SCR, but also because of particle interaction.
引文
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[17]SVACHULA J,ALEMANY L J,FERLAZZO N,et al.Oxidation of SO2 to SO3 over honeycomb De NOx catalysts[J].Ind.Eng.Chem.Res.,1993,33:1644.
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[19]王超,刘小伟,吴建群,等.220 MW热电联产锅炉中痕量元素的迁移及分布特性[J].化工学报,2014,65(9):3604-3608.WANG C,LIU X W,WU J Q,et al.Migration and distribution characteristics of trace elements in 220 MW cogeneration boiler[J].CIESC Journal,2014,65(9):3604-3608.
[20]盘思伟,徐义书,王小朋,等.燃煤锅炉SCR脱硝过程对颗粒物和痕量元素的影响[J].煤炭学报,2015,40:2702-2707.PAN S W,XU Y S,WANG X P,et al.Effects of SCR De NOx on the PM and trace elements[J].Journal of China Coal Society,2015,40:2702-2707.
[21]温昶,燃煤矿物质成灰行为的CCSEM分析与PM10生成特性的研究[D].武汉:华中科技大学,2013.WEN C.CCSEM study on mineral evolution and formation behavior of ash including PM10 during coal combustion[D].Wuhan:Huazhong University of Science and Technology,2013.
[22]WEN C,XU M,ZHOU K,et al.The melting potential of various ash components generated from coal combustion:indicated by the circularity of individual particles using CCSEM technology[J].Fuel Processing Technology,2015,133:128-136.
[23]KATRINAK K A,ZYGARLICKE C J.Size-related variations in coal fly ash composition as determined using automated scanning electron microscopy[J].Fuel Processing Technology,1995,44:71-79.
[24]EDWARDS D A,HANES J,CAPONETTI G,et al.Large porous particles for pulmonary drug delivery[J].Science,1997,276:1868-1872.
[25]YU D,XU M,YAO H,et al.A new method for identifying the modes of particulate matter from pulverized coal combustion[J].Powder Technology,2008,183:105-114.
[26]王杭州.SCR对脱硝效率及SO2转化影响分析[J].电力科学与工程,2008,24(5):17-21.WANG H Z.Analysis of SCR impact on denitration efficiency and SO2translation[J].Electric Power Science and Engineering,2008,24(5):17-21.
[27]姜烨,高翔,吴卫红,等.选择性催化还原脱硝催化剂失活研究综述[J].中国电机工程学报,2013,33(14):18-31.JIANG Y,GAO X,WU W H,et al.Review of the deactivation of selective catalytic reduction De NOx catalysts[J].Proceeding of the CSEE,2013,33(14):18-31.
[28]ZYGARLICKE C J,STEADMAN E N.Advanced SEM techniques to characterize coal minerals[J].Scanning Microscopy,1990,4:579-590.
[29]HUGGINS F E,KOSMACK D A,HUFFMAN G P,et al.Coal mineralogies by SEM automatic image analysis[J].Scanning Electron Microscopy,1980,(1):531-540.
[2]VERANTH J M,SMITH K R,HUGGINS F,et al.M?ssbauer spectroscopy indicates that iron in an aluminosilicate glass phase is the source of the bioavailable iron from coal fly ash[J].Chemical Research in Toxicology,2000,13:161-164.
[3]WEN C,XU M,YU D,et al.PM10 formation during the combustion of N2-char and CO2-char of Chinese coals[J].Proceedings of the Combustion Institute,2013,34:2383-2392.
[4]于敦喜,徐明厚,姚洪,等.燃煤纳米颗粒物的物化特性及其潜在健康危害[J].科学通报,2008,53:2654-2660.YU D X,XU M H,YAO H,et al.The physicochemical characteristics of nanoparticulates and its petential health risk[J].Chinese Science Bulletin,2008,53:2654-2660.
[5]XU M,YU D,YAO H,et al.Coal combustion-generated aerosols:formation and properties[J].Proceedings of the Combustion Institute,2011,33:1681-1697.
[6]杨春雪,阚海东,陈仁杰.我国大气细颗粒物水平、成分、来源及污染特征[J].环境与健康杂志,2011,28(8):735-738+753.YANG C X,KAN H D,CHEN R J.Research on level,composition,source and pollution characteristics of ambient fine particles in China[J].Journal of Environment and Health,2011,28(8):735-738+753.
[7]LIU X,XU Y,ZENG X,et al.Field measurements on the emission and removal of PM2.5 from coal-fired power stations(1):Case study for a1000 MW ultra super critical utility boiler[J].Energy&Fuels,2016,30:6547-6554.
[8]陈晓峰,郭道清,苏翔.燃煤电厂烟气脱硝技术现状探讨分析[J].科协论坛,2012,4:31-33.CHEN X F,GUO D Q,SU X.Status of the flue gas De-NOxtechnologies in the coal-fired power plants[J].Science&Technology Association Forum,2012,4:31-33.
[9]戚春萍,武文粉,王晨晔,等.燃煤电厂废旧SCR脱硝催化剂中Ti O2载体的回收与再利用[J].化工学报,2017,68(11):4239-4248.QI C P,WU W F,WANG C Y,et al.Recycling and reuse of Ti O2 carrier from waste SCR catalysts used in coal-fired power plants[J].CIESC Journal,2017,68(11):4239-4248.
[10]LIU X,XU Y,FAN B,et al.Field measurements on the emission and removal of PM2.5 from coal-fired power stations(2):Studies on two 135MW CFB boilers respectively equipped with electrostatic precipitator and hybrid electrostatic filter precipitator[J].Energy&Fuels,2016,30(7):5922-5929.
[11]王超,刘小伟,徐义书,等.660 MW燃煤锅炉细微颗粒物中次量与痕量元素的分布特性[J].化工学报,2013,64(8):2975-2981.WANG C,LIU X W,XU Y S,et al.Distribution characteristics of minor and trace elements in fine particulate matters from a 660 MW coal-fired boiler[J].CIESC Journal,2013,64(8):2975-2981.
[12]LI Z,JIANG J,MA Z,et al.Influence of flue gas desulfurization(FGD)installations on emission characteristics of PM2.5 from coal-fired power plants equipped with selective catalytic reduction(SCR)[J].Environmental Pollution,2017,230:655-662.
[13]YAN J,BAO J,YANG L.The formation and removal characteristics of aerosols in ammonia-based wet flue gas desulfurization[J].Journal of Aerosol Science,2011,42:604-614.
[14]潘丹萍,郭彦鹏,黄荣廷,等.石灰石-石膏法烟气脱硫过程中细颗粒物形成特性[J].化工学报,2015,66:4618-4625.PAN D P,GUO Y P,HUANG R T,et al.Formation of fine particles in flue gas desulphurization process using limestone-gypsum[J].CIESC Journal,2015,66:4618-4625.
[15]NIELSEN M T,LIVBJERG H,FOGH C L,et al.Formation and emission of fine particles from two coal-fired power plants[J].Combustion Science and Technology,2002,174:79-113.
[16]范红梅,张玉华,束航,等.SCR脱硝过程中细颗粒物排放特性[J].中南大学学报(自然科学版),2016,(1):321-329.FAN H M,ZHANG Y H,SHU H,et al.Characteristics of fine particulates emission from SCR reactor[J].Journal of Central South University,2016,(1):321-329.
[17]SVACHULA J,ALEMANY L J,FERLAZZO N,et al.Oxidation of SO2 to SO3 over honeycomb De NOx catalysts[J].Ind.Eng.Chem.Res.,1993,33:1644.
[18]杨林军,史雅娟,骆律源.燃煤烟气SCR脱硝系统中细颗粒物排放特性综述[J].中国电机工程学报,2016,16(36):4342-4348+4517.YANG L J,SHI Y J,LUO L Y.Review of emission characteristics of fine particles during coal-fired SCR De NOx process[J].Proceedings of the CSEE,2016,16(36):4342-4348+4517.
[19]王超,刘小伟,吴建群,等.220 MW热电联产锅炉中痕量元素的迁移及分布特性[J].化工学报,2014,65(9):3604-3608.WANG C,LIU X W,WU J Q,et al.Migration and distribution characteristics of trace elements in 220 MW cogeneration boiler[J].CIESC Journal,2014,65(9):3604-3608.
[20]盘思伟,徐义书,王小朋,等.燃煤锅炉SCR脱硝过程对颗粒物和痕量元素的影响[J].煤炭学报,2015,40:2702-2707.PAN S W,XU Y S,WANG X P,et al.Effects of SCR De NOx on the PM and trace elements[J].Journal of China Coal Society,2015,40:2702-2707.
[21]温昶,燃煤矿物质成灰行为的CCSEM分析与PM10生成特性的研究[D].武汉:华中科技大学,2013.WEN C.CCSEM study on mineral evolution and formation behavior of ash including PM10 during coal combustion[D].Wuhan:Huazhong University of Science and Technology,2013.
[22]WEN C,XU M,ZHOU K,et al.The melting potential of various ash components generated from coal combustion:indicated by the circularity of individual particles using CCSEM technology[J].Fuel Processing Technology,2015,133:128-136.
[23]KATRINAK K A,ZYGARLICKE C J.Size-related variations in coal fly ash composition as determined using automated scanning electron microscopy[J].Fuel Processing Technology,1995,44:71-79.
[24]EDWARDS D A,HANES J,CAPONETTI G,et al.Large porous particles for pulmonary drug delivery[J].Science,1997,276:1868-1872.
[25]YU D,XU M,YAO H,et al.A new method for identifying the modes of particulate matter from pulverized coal combustion[J].Powder Technology,2008,183:105-114.
[26]王杭州.SCR对脱硝效率及SO2转化影响分析[J].电力科学与工程,2008,24(5):17-21.WANG H Z.Analysis of SCR impact on denitration efficiency and SO2translation[J].Electric Power Science and Engineering,2008,24(5):17-21.
[27]姜烨,高翔,吴卫红,等.选择性催化还原脱硝催化剂失活研究综述[J].中国电机工程学报,2013,33(14):18-31.JIANG Y,GAO X,WU W H,et al.Review of the deactivation of selective catalytic reduction De NOx catalysts[J].Proceeding of the CSEE,2013,33(14):18-31.
[28]ZYGARLICKE C J,STEADMAN E N.Advanced SEM techniques to characterize coal minerals[J].Scanning Microscopy,1990,4:579-590.
[29]HUGGINS F E,KOSMACK D A,HUFFMAN G P,et al.Coal mineralogies by SEM automatic image analysis[J].Scanning Electron Microscopy,1980,(1):531-540.