Research On Online Monitoring Of Sulfur Trioxide In Coal-fired Power Plants

The growing problem of environmental pollution has caused great concern in countries around the world.Flue gas emissions from stationary sources such as thermal power plants and chemical plants have become the focus of monitoring and control.With the continuous improvement of environmental protection requirements,SO₃,a pollutant in the flue gas emissions from coal-fired power plants,has gradually attracted attention.SO₃is easily combined with water in the flue gas to form H₂SO₄,which causes low temperature corrosion and plume.The prerequisite for effective treatment of SO₃ in flue gas is the ability to accurately monitor its content.However,due to the active nature of SO₃,its monitoring technology is still problematic in this field.This paper is mainly devoted to the application of ultraviolet absorption spectroscopy and differential absorption spectroscopy to online monitoring of SO₃ emissions from coal-fired power plants.In-depth research and exploration have been made from theoretically and experimentally in this research.The results of experimental studies on the concentration measurement of SO₃ by UV absorption spectroscopy indicate that it is feasible to measure the concentration of SO₃ in flue gas by ultraviolet absorption method and that the experimentally measured characteristics of the UV absorption spectrum of SO₃ are consistent with previous studies.This paper uses the standard curve method combined with the single-wavelength method,the dual-wavelength method and the integral spectrum method to establish three standard curves for the concentration inversion of SO₃in unknown gas.The results show that the standard curve measurement error established by integral spectroscopy is lower than the single wavelength method and the dual wavelength method.The results of experimental studies on the concentration measurement of SO₃ by differential absorption spectroscopy indicate that differential absorption spectroscopy can be used for on-line monitoring of SO₃ and achieve simultaneous monitoring of SO₂ and SO₃ In this paper,two concentration inversion schemes are developed based on the absorption spectra of SO₃ and SO₂.The first option is to first retrieve SO₂ and then retrieve SO₃.The second is simultaneous retrieval of SO₂ and SO₃.The experiment proves that the inversion effect of the second scheme is better than the scheme one as a whole.Therefore,when differential absorption spectroscopy is used to perform SO₃ concentration inversion,simultaneous retrieval of SO₂ and SO₃ in the band of 200²20nm is the preferred solution.In addition,the paper uses three algorithms,such as least squares method,SG smoothing filtering and Fourier transform filtering,for the concentration retrieval of SO₃.The results show that the retrieval error of Fourier transform filtering method is low and the algorithm has good stability.Therefore,utilizing Fourier transform filtering to measure low concentration of SO₃ in flue gas can achieve better results.