烟气组分含量连续监测系统探头设计及标定方法

Probe design and calibration for a continuous flue gas monitoring system

为解决采用紫外差分吸收光谱法对烟气中主要气体污染物SO2和NOx进行测量时不方便和误差较大的问题,该文设计了单边插入式双光路探头,能较好适应烟道内高温对探头形状的影响,工作稳定可靠,现场调整方便。光谱数据的定标和标准量化是以Lambert-Beer定律为基础,针对实际环境中的非线性因素所产生的偏离Lambert-Beer定律的现象,该文提出一套可将气体长度变化等效于浓度变化的标定方法,采用不同长度的单一浓度的标准气体,实现了探头高精度标定。使用标定后的探头对SO2和NO两种气体进行多次测量,平均偏差均小于1.5%。

The concentrations of the main pollutants in flue gas streams, SO2 and NO2, can be measured by differential optical absorption spectroscopy once the spectrum has been calibrated by a standard. A single-side probe with a double light path was designed for stable and reliable measurements. The improved probe significantly reduces the temperature influence on the spectrum shape. The quantization and calibration of the spectrum are based on the Lambert-Beer law with a correction for deviations from the Lambert-Beer law. The calibration is based on changes of the gas path length instead of changes of gas concentration. A single concentration of a standard gas is used with different lengths for high precision probe calibration, and average errors are less than 1.5 %.