算法融合的差分吸收光谱法烟气SO_2浓度在线监测研究

Research on In-Situ Monitoring of SO_2 Concentration in the Flue Gases with DOAS Method Based on Algorithm Fusion

过去几十年中差分吸收光谱技术(differential optical absorption spectroscopy,DOAS)在大气污染物监测方面取得了成功应用。文章提出了根据差分吸光度最大值(OD′m)设定阈值的思想,将传统DOAS算法与基于卡尔曼滤波的DOAS算法相结合,利用两种算法在相同信噪比下具有不同反演精度的特点,在保证测量精度的前提下提高了DOAS系统的检测极限,较好地解决了短光程下低浓度气体的测量精度问题。在常温常压和流动状态下,对烟气中的SO2浓度测量进行了理论和实验研究。研究结果表明,改进的DOAS算法在OD′m<0.0481时,SO2浓度测量精度较高,测量下限可低于28.6mg·m-3,零点漂移低于2.9mg·m-3;传统DOAS算法在0.0481<OD′m<0.9272时,SO2浓度测量精度较高;两种算法对OD′m>0.9272时的SO2浓度测量都存在较大的误差,必须进行线性度校正。

Valuable achievements on differential optical absorption spectroscopy （DOAS） for monitoring atmospheric pollutants gas have been made in the past decades. Based on the idea of setting the threshold according to the maximum value, symbolized as OD＇m, Of differential optical density, the algorithm of traditional DOAS was combined with the DOAS algorithm based on the kalman filtering to improve the detection limit without losing measurement accuracy in the present article. Two algorithms have different inversion accuracy at the same ratio of signal to noise and the problem of inversion accuracy was well resolved by combining two algorithms at short light path length. Theoretical and experimental research on the concentration measurement of SO2 in the flue gases was carried out at the normal temperature and atmospheric pressure. The research results show that with the OD＇m less than 0. 048 1, the measurement precision is very high for SO2 with the improved DOAS algorithrrL The measurement lower limit of SO2 is less than 28.6 mg·m^-3 a and the zero drift of the system is less than 2.9 mg·m^-3. If the OD＇m is between 0. 048 1 and 0. 927 2, the measurement precision is high with the traditional DOAS algorithrm. However, if the OD＇m is more than 0. 922, the errors of measurement results for both two DOAS algorithms are very large and the linearity correction must be performed.