光子学报, 2018, 47 (2): 0230001, 网络出版: 2018-01-30
基于DOAS及统计量的低浓度SO2测量方法
Measurement Method for Lowconcentration SO2 Based on Statistics and DOAS
大气光学 气体监测系统 统计量 二氧化硫 吸收光谱 烟气 差分光学吸收光谱 Atmospheric optics Gas detectors Statistics Sulfur dioxide Absorption spectroscopy Flue gases Differential optical absorption spectroscopy
摘要
为监测燃煤电厂低浓度SO2排放, 达到国家超低排放标准, 提出一种短光程下测量低浓度SO2的方法.在已知温度压强条件下, 利用差分吸收光谱法, 由不同浓度的标准气体构建SO2差分吸收截面数据集; 根据数据集标准差及均值, 结合浓度反演结果, 将测量区间由200~400 nm逐步缩小到294~308 nm.对该区间内137个波长采样点, 用统计学方法, 借助标准差及均值表征差分吸收截面精度, 同时剔除误差较大的采样点, 得到该环境下最优采样点集和差分吸收截面最优数据集.在同等温度压强条件下, 利用该最优数据集和差分吸收光谱法, 能够以较高精度计算出烟气中SO2浓度.实验采用420 cm光程, 气室容积0.5 L, 气室内温度299.05 K, 压强101.33 kPa, 测量范围2~30 μL/L.实验结果表明该方法相对误差低于1.7%, 满量程误差低于1.3%, 零漂0.09 μL/L, 72 h内重复性良好.在420 cm光程条件下, 该方法能够高精度测量30 μL/L内的SO2气体, 解决差分吸收光谱法中浓度与光程之间的冲突, 适用于燃煤电厂超低排放监测仪器的研制.
Abstract
In order to monitor SO2 emission from coalfired power factories and meet national ultralow emission standards, measurement method for lowconcentration SO2 via short optical length is proposed. At known pressure and temperature conditions, dataset of differential absorption cross section was constructed with various concentrations of standard gas, utilizing differential optical absorption spectroscopy (DOAS). In accordance with standard deviation and average of the dataset, combined with results of concentration inversion, spectral window was gradually reduced from 200~400 nm to 294~308 nm. For each point in 294~308 nm, where there are 137 sampling points, statistics and standard deviation were applied to characterize consistency of differential absorption cross section. It was only when standard deviation and average at sampling point met requirements that the point was reserved to optimal point set. So optimal dataset of differential absorption cross section and optimal sampling points were constructed eventually. At same pressure and temperature conditions, SO2 concentration in flue gases can be accurately calculated by the optimal dataset and DOAS. In the laboratory, measurement range is 2~30 μL/L, temperature and pressure are 299.05 K, 101.33 kPa, while optical length and volume of gas cell are 420 cm, 0.5 L correspondingly. Experimental results show that inversion concentration performs superior repeatability within 72 h, relative error is less than 1.7%, full scale error is below 1.3%, and zero drift is 0.09 μL/L. With 420 cm optical length, the method can precisely measure lowconcentration SO2 under 30 μL/L, resolve conflicts between concentration and optical length, which is suitable for study of ultralow emission monitoring system used in coalfired power plants.
张豹, 高潮, 郭永彩, 刘国庆, 陈方. 基于DOAS及统计量的低浓度SO2测量方法[J]. 光子学报, 2018, 47(2): 0230001. ZHANG Bao, GAO Chao, GUO Yongcai, LIU Guoqing, CHEN Fang. Measurement Method for Lowconcentration SO2 Based on Statistics and DOAS[J]. ACTA PHOTONICA SINICA, 2018, 47(2): 0230001.