Abstract:

Ultraviolet differential absorption spectroscopy technology has been widely used in the monitoring of industrial flue gas emissions. The spectrometer, a core component of the UV flue gas analyzer, is susceptible to wavelength drift caused by temperature changes, which in turn affects the accuracy of pollutants monitoring results. In this paper, a soft wavelength calibration method for spectrometers is proposed. A standard SO₂ absorption spectrum peak wavelength database is established through experiments. When the wavelength drift exceeds 0.02nm, the corresponding function between the spectrometer pixel and wavelength will be re-fitted using the pixel of the SO₂ absorption peak in conjunction with the database. This method enables real-time calibration of the spectrometer wavelength. Experiments are conducted to validate the proposed calibration method. Results showed that with a 10℃ environmental temperature range, this method can reduce the measurement error of 993mg/m³ NO standard gas from 115.2mg/m³ to 21.4mg/m³, with an absolute error reduction of 93.8mg/m³. The best wavelength calibration effect is achieved when the measured SO₂ concentration is 1430mg/m³. For low-concentration measurement sites, the signal-to-noise ratio of the spectral signal can be amplified by increasing the number of spectral averages, thereby improving the effectiveness of the online wavelength calibration method.

Key words: ultraviolet differential absorption spectroscopy, spectrometer, wavelength calibration, absorption spectrum

摘要：

紫外差分吸收光谱技术已被广泛用于工业污染源废气排放浓度监测。光谱仪作为紫外烟气分析仪的核心器件，易受到温度变化而产生波长漂移，进而影响监测结果的准确性。本文提出了一种光谱仪波长“软”标定方法，通过实验建立标准SO₂吸收谱线极值波长数据库，利用SO₂吸光度极值像素点和标准SO₂吸收光谱极值波长，对光谱仪像素点与波长的对应函数进行重新拟合，以实现光谱仪波长实时校准。搭建了实验系统，并开展了光谱仪波长标定方法验证研究。结果表明，当光谱仪所处环境温度变化范围为10℃时，采用本文方法可以使993mg/m³ NO标气的测量误差从115.2mg/m³降低至21.4mg/m³，绝对误差减小了93.8mg/m³；当被测SO₂为1430mg/m³时，测量系统信噪比较高，波长校准效果最佳；针对低浓度测量现场，可通过增加光谱平均次数来增强光谱信号的信噪比，提高波长在线校准方法的效果。

关键词: 紫外差分吸收光谱, 光谱仪, 波长校准, 吸收光谱