DOAS方法的多特征谱解析及应用
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摘要
大气质量的优劣直接影响着生态平衡和人类健康,因此监测和控制大气污染源的排放具有相当重要的意义。为了实现对固定污染源中气态污染物(SO2、NOx)和颗粒物的同时在线连续监测,本文对差分光学吸收光谱(DOAS)技术做了进一步的拓展,并设计了基于该方法的固定污染源烟气排放连续监测系统(CEMS)。
本文主要内容如下:
1.提出了DOAS方法的多特征谱解析,对于光谱中包含的各种信息的不同特性进行分析,得出它们对于吸收光谱的影响。吸收光谱依据随波长和时间变化的快慢,可分离为快波、中快波、中慢波和慢波四个部分,分别与仪器噪声、气体污染物的特征吸收、颗粒物扰动和仪器漂移具有很高的相关性,实现了对烟气中气态污染物和颗粒物浓度的同时监测。
2.根据固定污染源中气态污染物及颗粒物的光谱特性,提出了基于DOAS方法的CEMS系统的总体设计,并分别介绍了其中的光学系统、电路系统、机械结构、工控机及软件设计。对于光学系统中的准直系统进行了设计,基于分光系统的参数计算系统光谱分辨力为0.102nm。针对系统工作的恶劣环境,进行了消除杂散光、防潮、防尘、防震及恒温等多方面的设计。最后利用内置角锥镜、遮光板、标准气体样品池及低压汞灯进行了系统的标定。
3.提出了利用DOAS方法监测气态污染物和颗粒物的数据处理方法,分为两条主线:建模实验和实际测量。在建模试验中,利用浓度呈梯度分布的单一气体进行测量,通过Savitzky-Golay数字滤波器从吸收光谱中提取快波,计算出基准吸收系数。利用基准截面计算所得的浓度与实际浓度进行多项式拟合,建立拟合公式。利用已知的气体浓度,排除中慢波中气体的影响,对颗粒物浓度建模。在实际测量中,从预处理后的吸收光谱中得到中快波,利用最小二乘法计算基准截面下的浓度,再代入拟合公式中得到真实的气态污染物浓度。之后排除中慢波中气体的影响,求出颗粒物浓度。应用光谱平移和拉伸校正,使算法具有更好的适用性。
4.分析了系统中影响测量精度的因素,如温度、流速、分辨力等,提出了相应的改进措施。
Air quality directly affects with ecological balance and human health. So it is significant to monitor and control the air pollution sources. In order to continuously monitor the gaseous pollutant(SO2、NOx) and particulates in the stationary sources, this paper designed the Continuous Emission Monitoring Systems(CEMS) based on the theory of Differential Optical Absorption Spectroscopy(DOAS) .
The main content of this paper is listed as follows.
1. Multi-characteristic spectrum analysis of DOAS is an improved theory with the key technology which is the divide of absorption spectrum according to the variation rate follow the wavelength. The absorption spectrum can be divided into four parts which are fast wave, mid-fast wave, mid-slow wave and slow wave, respectively related with the noise, absorption of SO2 and NOx, concentration of particulates and instrument drift. Based on the theory Simultaneous Monitoring of gaseous pollutant and Particulates can be realized by a single instrument.
The CEMS, including the optical system, circuit system, mechanical structure, industrial computer and the software, was designed based on the spectral characteristics of gaseous pollutant. The parameter of optical elements in the collimation system and the spectral resolution of the system were calculated. Aiming at the terrible environment where the CEMS was set a lot of work has done such as eliminate stray light, moisture proof, shock proof, constant temperature and so on. At last calibrate the CEMS with pyramid prism, shading board, low pressure mercury lamp and calibration gases.
There are two clues in the Data Processing Method of DOAS, experimental modeling and practical measuring. During the experimental modeling extract the mid-fast wave by Savitzky-Golay digital filter from the absorption spectrum of gaseous pollutant with different concentration. Calculated the base absorption cross section and fit the measured concentration. In practical measuring calculate the concentration with the base absorption cross and fit the practical concentration with the modeling. Then calculate the concentration of particulates with mid-fast wave. The adaptability of the algorithm can be improved by translation and stretching the absorption spectrum.
The factors which influence the precision of CEMS such as temperature, velocity of flue, resolution and so on are analyzed. And the solutions were also proposed.
本文主要内容如下:
1.提出了DOAS方法的多特征谱解析,对于光谱中包含的各种信息的不同特性进行分析,得出它们对于吸收光谱的影响。吸收光谱依据随波长和时间变化的快慢,可分离为快波、中快波、中慢波和慢波四个部分,分别与仪器噪声、气体污染物的特征吸收、颗粒物扰动和仪器漂移具有很高的相关性,实现了对烟气中气态污染物和颗粒物浓度的同时监测。
2.根据固定污染源中气态污染物及颗粒物的光谱特性,提出了基于DOAS方法的CEMS系统的总体设计,并分别介绍了其中的光学系统、电路系统、机械结构、工控机及软件设计。对于光学系统中的准直系统进行了设计,基于分光系统的参数计算系统光谱分辨力为0.102nm。针对系统工作的恶劣环境,进行了消除杂散光、防潮、防尘、防震及恒温等多方面的设计。最后利用内置角锥镜、遮光板、标准气体样品池及低压汞灯进行了系统的标定。
3.提出了利用DOAS方法监测气态污染物和颗粒物的数据处理方法,分为两条主线:建模实验和实际测量。在建模试验中,利用浓度呈梯度分布的单一气体进行测量,通过Savitzky-Golay数字滤波器从吸收光谱中提取快波,计算出基准吸收系数。利用基准截面计算所得的浓度与实际浓度进行多项式拟合,建立拟合公式。利用已知的气体浓度,排除中慢波中气体的影响,对颗粒物浓度建模。在实际测量中,从预处理后的吸收光谱中得到中快波,利用最小二乘法计算基准截面下的浓度,再代入拟合公式中得到真实的气态污染物浓度。之后排除中慢波中气体的影响,求出颗粒物浓度。应用光谱平移和拉伸校正,使算法具有更好的适用性。
4.分析了系统中影响测量精度的因素,如温度、流速、分辨力等,提出了相应的改进措施。
Air quality directly affects with ecological balance and human health. So it is significant to monitor and control the air pollution sources. In order to continuously monitor the gaseous pollutant(SO2、NOx) and particulates in the stationary sources, this paper designed the Continuous Emission Monitoring Systems(CEMS) based on the theory of Differential Optical Absorption Spectroscopy(DOAS) .
The main content of this paper is listed as follows.
1. Multi-characteristic spectrum analysis of DOAS is an improved theory with the key technology which is the divide of absorption spectrum according to the variation rate follow the wavelength. The absorption spectrum can be divided into four parts which are fast wave, mid-fast wave, mid-slow wave and slow wave, respectively related with the noise, absorption of SO2 and NOx, concentration of particulates and instrument drift. Based on the theory Simultaneous Monitoring of gaseous pollutant and Particulates can be realized by a single instrument.
The CEMS, including the optical system, circuit system, mechanical structure, industrial computer and the software, was designed based on the spectral characteristics of gaseous pollutant. The parameter of optical elements in the collimation system and the spectral resolution of the system were calculated. Aiming at the terrible environment where the CEMS was set a lot of work has done such as eliminate stray light, moisture proof, shock proof, constant temperature and so on. At last calibrate the CEMS with pyramid prism, shading board, low pressure mercury lamp and calibration gases.
There are two clues in the Data Processing Method of DOAS, experimental modeling and practical measuring. During the experimental modeling extract the mid-fast wave by Savitzky-Golay digital filter from the absorption spectrum of gaseous pollutant with different concentration. Calculated the base absorption cross section and fit the measured concentration. In practical measuring calculate the concentration with the base absorption cross and fit the practical concentration with the modeling. Then calculate the concentration of particulates with mid-fast wave. The adaptability of the algorithm can be improved by translation and stretching the absorption spectrum.
The factors which influence the precision of CEMS such as temperature, velocity of flue, resolution and so on are analyzed. And the solutions were also proposed.
引文
[1]徐祥德,周秀骥,施晓晖.城市群落大气污染源影响的空间结构及尺度特征,中国科学,2005,3 (1):1-19.
[2]国家环境保护总局,国家质量监督检验检疫总局.水泥工业大气污染物排放标准[J].中国水泥,2005,2:7-11
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[4] W. Schneider,G. K. Moortgat,Absorption cross-sections of NO2 in the UV and visible region (200-700nm) at 298K,J. Photochemistry and Photobiology A: Chem,1987,40:195~217
[5] Mount G H, Rumburg B, Havig J. Atmospheric Environment, 2002, 36(11): 1799
[6] http://it.sohu.com/20080229/n255452184.shtml
[7]李国刚,环境在线自动监测技术与仪器设备的发展动态,生命科学仪器,2003(11): 21-30
[8]易江,烟气连续排放监测系统,现代科学仪器,2000,49(1):34-39
[9] http://epacems.ctciestc.org.tw
[10] U.Platt,Dry deposition of SO2,Atmos.Environ, 1978,12:363~367
[11] F.Evangelisti,A.Baroncelli,P.Bonasoni,G.Giovanelli and F.Ravegnani, DOAS spectrometer for measuring tropospheric pollutants, Applied Optics, 1944, 34:2737~2744
[12]谢品华,刘文清,郑朝晖等,差分光学吸收光谱(DOAS)技术在烟气SO2监测中的应用,光子学报, 2000,29(3): 271~276
[13]郑朝晖,刘文清,宋炳超等,差分光学吸收光谱(DOAS)技术在烟气监测中的应用研究,量子电子学报,2001,18(12): 65~69
[14] Evangelisti F, Baroncelli A, Bonasoni P et al. Differential optical absorptionspectrometer for measurement of tropospheric pollutants [J].1995, 34(15): 2737~2747
[15] W B Grant, R H Kagann,W A M cClenny. Op t ical remo te measurement of toxic gases [J ]. J. of A ir & W aste, 1992, 42 (1): 18~30.
[16]郑朝晖,刘文清,谢品华等,烟道SO2浓度的紫外差分吸收光谱法测量研究,光电子.激光, 2000,11(6): 613~616
[17]崔厚欣,齐汝宾,张文军,差分吸收光谱法大气环境质量在线连续监测系统的设计,分析仪器,2008,1:7-11
[18]苗岩松,段国芳,张爱萍,颗粒物监测方法研究情况综述,测试技术学报,1997, 11(4):48~51
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[20] Platt U, Perner D, Simultaneous measurements of atmospheric CH2O, O3 and NO2 by differential optical absorption. J.Geophys Res,1979,84:6329~6335
[21] Platt U, Perner D, Direct measurement of atmospheric CH2O, NO2,O3 and SO2 by differential absorption in the near UV.J Geophys Res,1980,85:7453~7458
[22] Axelson H, Galle B, A transmitting/receiving telescope for DOAS measurements using retroreflector technique. Dig Top Meet Opt Remote sens Atmos Optical Society of America,1990,(4): 641~644
[23] John M C, Plane, Chia-Fu Nien. Differential optical absorption spectrometer for measuring atmospheric trace gases. Rev Sci Instrum,1992,63(3): 1867~1876
[24] Theo Brauers, Martin Hansmann, Improvement of differential optical absorption spectroscopy with a multi-channel scanning technique. Applied Optics, 1995, 34(21): 4472~4479
[25] Jochen Stutz, Ulrich Platt. Numerical analysis and estimation of the statistical error of differential optical absorption spectroscopy measurements with least squares method[J].Applied Optics,1996,35(30): 6041~6053
[26] Ahilleas N Maurellis, Rudiger Lang. A new DOAS parameterization for retrieval of trace gases with high structured absorption spectra [J].Geophysical Research Letters, 2000, 27(24): 4069~4072
[27] http://www.opsis.se
[28] http://www.hmm.de/DOAS/doas.html
[29] http://www.thermo.com
[30] http://www.enviroment-sa.com
[31] http://www.eridan.mega.ru/
[32] Sung-Hwan Han, Hyeon-Ho Kim, Dae-Sung Kim,A New Method for Analysis of Differential Optical Absorption Spectra using Wavelet Transform and Independent Component Analysis,Instrumentation and Measurement Technology Conference Ottawa, Ontario, Canada, May 17–19, 2005
[33] Christoph Kern, Sebastian Trick, Bernhard Rippel , Applicability oflight-emitting diodes as light sources for active differential optical absorption spectroscopy measurements,Applied Optics,2006,45(9):2077~2088
[34]秦敏,谢品华,刘建国,等,基于二极管阵列PDA的紫外.可见差分吸收光谱(DOAS)系统的研究,光谱学与光谱分析,2005,25(9):1463~1467
[35]邵理堂,汤光华,许传龙,等,差分吸收光谱法(DOAS)测量污染气体浓度的实验研究,锅炉技术,2008,39(2):13~17
[36]邵理堂,汤光华,许传龙,等.利用小波变换消除颗粒物Mie散射对DOAS技术的影响[J].东南大学学报:自然科学版,2008,38(3):444~448.
[37]陈代胜,张莉君,鲍建国,化学发光法和DOAS测定NOx的对比研究,环境科学与技术,2007,30(9):50~52
[38]张学典,黄显,徐可欣,差分吸收光谱反演方法在环境监测系统中的研究,光谱学与光谱分析,2007,27(11):2367~2370
[39]崔厚欣,齐汝宾,张文军,差分吸收光谱法大气环境质量在线连续监测系统的设计,分析仪器,2008,1:7~11
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[2]国家环境保护总局,国家质量监督检验检疫总局.水泥工业大气污染物排放标准[J].中国水泥,2005,2:7-11
[3]曹守仁,煤烟污染与健康,北京:中国环境科学出版社,1992,6~33
[4] W. Schneider,G. K. Moortgat,Absorption cross-sections of NO2 in the UV and visible region (200-700nm) at 298K,J. Photochemistry and Photobiology A: Chem,1987,40:195~217
[5] Mount G H, Rumburg B, Havig J. Atmospheric Environment, 2002, 36(11): 1799
[6] http://it.sohu.com/20080229/n255452184.shtml
[7]李国刚,环境在线自动监测技术与仪器设备的发展动态,生命科学仪器,2003(11): 21-30
[8]易江,烟气连续排放监测系统,现代科学仪器,2000,49(1):34-39
[9] http://epacems.ctciestc.org.tw
[10] U.Platt,Dry deposition of SO2,Atmos.Environ, 1978,12:363~367
[11] F.Evangelisti,A.Baroncelli,P.Bonasoni,G.Giovanelli and F.Ravegnani, DOAS spectrometer for measuring tropospheric pollutants, Applied Optics, 1944, 34:2737~2744
[12]谢品华,刘文清,郑朝晖等,差分光学吸收光谱(DOAS)技术在烟气SO2监测中的应用,光子学报, 2000,29(3): 271~276
[13]郑朝晖,刘文清,宋炳超等,差分光学吸收光谱(DOAS)技术在烟气监测中的应用研究,量子电子学报,2001,18(12): 65~69
[14] Evangelisti F, Baroncelli A, Bonasoni P et al. Differential optical absorptionspectrometer for measurement of tropospheric pollutants [J].1995, 34(15): 2737~2747
[15] W B Grant, R H Kagann,W A M cClenny. Op t ical remo te measurement of toxic gases [J ]. J. of A ir & W aste, 1992, 42 (1): 18~30.
[16]郑朝晖,刘文清,谢品华等,烟道SO2浓度的紫外差分吸收光谱法测量研究,光电子.激光, 2000,11(6): 613~616
[17]崔厚欣,齐汝宾,张文军,差分吸收光谱法大气环境质量在线连续监测系统的设计,分析仪器,2008,1:7-11
[18]苗岩松,段国芳,张爱萍,颗粒物监测方法研究情况综述,测试技术学报,1997, 11(4):48~51
[19] JF NOXON, Dioxide in the stratosphere and trosphere measurement by ground-based absorption spectroscopy. Science, 1975, 189(4202): 547~549.
[20] Platt U, Perner D, Simultaneous measurements of atmospheric CH2O, O3 and NO2 by differential optical absorption. J.Geophys Res,1979,84:6329~6335
[21] Platt U, Perner D, Direct measurement of atmospheric CH2O, NO2,O3 and SO2 by differential absorption in the near UV.J Geophys Res,1980,85:7453~7458
[22] Axelson H, Galle B, A transmitting/receiving telescope for DOAS measurements using retroreflector technique. Dig Top Meet Opt Remote sens Atmos Optical Society of America,1990,(4): 641~644
[23] John M C, Plane, Chia-Fu Nien. Differential optical absorption spectrometer for measuring atmospheric trace gases. Rev Sci Instrum,1992,63(3): 1867~1876
[24] Theo Brauers, Martin Hansmann, Improvement of differential optical absorption spectroscopy with a multi-channel scanning technique. Applied Optics, 1995, 34(21): 4472~4479
[25] Jochen Stutz, Ulrich Platt. Numerical analysis and estimation of the statistical error of differential optical absorption spectroscopy measurements with least squares method[J].Applied Optics,1996,35(30): 6041~6053
[26] Ahilleas N Maurellis, Rudiger Lang. A new DOAS parameterization for retrieval of trace gases with high structured absorption spectra [J].Geophysical Research Letters, 2000, 27(24): 4069~4072
[27] http://www.opsis.se
[28] http://www.hmm.de/DOAS/doas.html
[29] http://www.thermo.com
[30] http://www.enviroment-sa.com
[31] http://www.eridan.mega.ru/
[32] Sung-Hwan Han, Hyeon-Ho Kim, Dae-Sung Kim,A New Method for Analysis of Differential Optical Absorption Spectra using Wavelet Transform and Independent Component Analysis,Instrumentation and Measurement Technology Conference Ottawa, Ontario, Canada, May 17–19, 2005
[33] Christoph Kern, Sebastian Trick, Bernhard Rippel , Applicability oflight-emitting diodes as light sources for active differential optical absorption spectroscopy measurements,Applied Optics,2006,45(9):2077~2088
[34]秦敏,谢品华,刘建国,等,基于二极管阵列PDA的紫外.可见差分吸收光谱(DOAS)系统的研究,光谱学与光谱分析,2005,25(9):1463~1467
[35]邵理堂,汤光华,许传龙,等,差分吸收光谱法(DOAS)测量污染气体浓度的实验研究,锅炉技术,2008,39(2):13~17
[36]邵理堂,汤光华,许传龙,等.利用小波变换消除颗粒物Mie散射对DOAS技术的影响[J].东南大学学报:自然科学版,2008,38(3):444~448.
[37]陈代胜,张莉君,鲍建国,化学发光法和DOAS测定NOx的对比研究,环境科学与技术,2007,30(9):50~52
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