基于非线性标准差模型的差分光学吸收光谱技术烟气浓度测量

A non-linear standard deviation model for differential optical absorption spectroscopy to determine flue gas concentration

采用差分光学吸收光谱(DOAS)技术测量烟气时,需采用非线性补偿方法来提高测量精度。本文基于自行研制的DOAS技术烟气测量系统,对SO_2和NO标准气体进行了单一气体的建模实验,提出了利用差分光学密度标准差和气体浓度之间关系的非线性模型预测烟气浓度的方法,并以此测量了SO_2和NO单一组分及混合气体的浓度,将实验结果与传统最小二乘法的反演浓度进行了对比。结果显示,测量单一气体时,得到的两种气体非线性模型的判定系数R^2分别为0.999 6和0.999 5,SO_2的满量程误差为±0.7%,最大误差为2.6%和2.8%,明显优于最小二乘法反演最大误差-16.1%和-19.9%;测量混合气体时,最大误差由传统方法的-24.6%和-28.1%减小至-4.8%和5.2%。结果表明,本文方法可提高烟气测量的准确度。

Differential optical absorption spectroscopy （IX）AS） has been w^deJy applied in the flue gas concentration determination based on Lambert-Beerr s law. However, under high concentration poilu- tantts, the bias from Lambert-Beer＇s law increases due to the pollutant molecule interactions, and causes inevitable errors only with least squares regression. Therefore, a non-linear model for flue gas concentra tion determination based on standard deviation of differential optical density is put forward in this paper, proved by both single-component and mixture experiments with standard SO2 and NO, and compared with traditional least-squares （IS） modeling method. The results of nonqinear modeling method indicate that in the single-component experiment,the correlation coefficients （R2 ） of non-linear models are 0. 999 6 for SO2 and 0. 999 5 for NO, and the maximum errors greatly reduce to 2.6% and 2.8% compared with --16. 1% and --19. 9% using traditional LS modeling method;in the mixture experiment, the maximum errors also obviously decrease to --4. 8% and 5.2% compared with --24. 6% and --28. 1% using LS modeling. In all, this non-linear modeling method based on standard deviation of differential op- tical density possesses great potential to be applied to the flue gas concentration determination with an improved accuracy.