基于差分吸收光谱技术NH_3浓度在线反演方法研究

Study of online concentration retrieval method for ammonia based on difference optical absorption spectrometry

差分吸收光谱法(DOAS)原理简单、检测精度高、响应速度快、可应用于非接触和连续在线监测。本文利用差分吸收光谱法对NH_3浓度进行在线反演。不同于传统的DOAS中选取部分波长点光谱数据反演气体浓度,本文充分利用反演波段内所有实验数据,联立超定方程组,并用最小二乘法求解。为了消除温度对反演结果的影响,利用20℃与其他温度下NH_3分子数密度比的比值和对应温度的关系拟合出温度补偿函数对反演结果进行温度补偿。实验结果表明该方法反演NH_3浓度时具有较高的反演精度。

Differential Optical Absorption Spectroscopy （DOAS） has the advantages of simple principle, fast response, high detection accuracy, non-contact and on-line continuous monitoring. This paper applied difference optical absorption spectrometry （DOAS） to the retrieval of ammonia online concentration. Different from the traditional DOAS which selects the part of the wavelength point spectrum data to retrieve gas concentration, this paper makes full use of the experiment data in all retrieval bands, forming simultaneous over-determined equations, which are solved by using the least square method. In order to eliminate the influence of temperature on the retrieval results, we use the relation of ammonia molecule density ratio in different temperatures to fit temperature compensation function, with which to compensate temperature influence on the retrieval results. The experimental results show that this method has higher retrieval accuracies of ammonia concentration.