Abstract: The current problems of multiple interference factors and slow response time in online detection of low-volume-fraction SO2 gas in flue gas detection.In this case,an online SO₂ detection system based on the non-dispersive infrared absorption principle was designed,which used the characteristic capability of SO₂ to absorb infrared light in a specific band and adopted a single light source and dual channel method. Experiment results show that the zero drift is 0.4%, the response time is 3.86 s, the linear error is 0.3%, and the repeatability error is 0.52%. A comparison of parameters shows that this method can accurately measure SO2 concentration and is more suitable for the current demand of online flue gas detection.

Key words: SO₂, nondispersive infrared absorption, single light source and dual channel, response time