On-line Monitoring System Of Flue Gas By UV Differential Optical Absorption Spectroscopy

As a result of the development of industry, environmental pollution becomes more and more serious. The theme of economic development is to reach sustainable development by protecting environment in the new century. It is an available approach to administer the emission of pollutant by on-line monitoring flue gas. In this thesis, a method based on differential optical absorption spectroscopy (DOAS) technique was developed for flue gas monitoring. The results showed that current method can reduce the influences of high temperature, high pressure, high concentration and dust in stack and industrial condition on flue gas monitoring. In this thesis, DOAS technique was applied to the on-line flue gas monitoring system. The fundamentals of DOAS were discussed and the measurement method of flue gas concentraction was introduced. The flue gas monitoring system based on optics, mechanics, electronics and software was performed under the flue gas condition. Especially, the multi-channel optical spectromecter with photodiode array (PDA) as the detector was used in this system. The retrieving concentraction metod using DOAS technique was demonstrated from the following aspects: 1) the principle of DOAS arithmetic; 2) reference spectra processing by using instrument function; 3) wavelength calibration by moving and shifting spectra; 4) the introduction of multiple linear regression model and the least-square method; 5) the analysis of residual structure of spectra. In order to compensate temperature and nonlinearity high concentration, the experiential correction formulae were deduced. Finally, under the condition of the results from pilot experiments indicated that the system can fulfill the requirements of the on-line monitoring for flue gas with a proper measurement accuracy and stability. The results showed that the DOAS could be used in flue gas monitoring. Meanwhile, the application of DOAS in flue gas monitoring extended DOAS technique and provided the technical support to improve low atmosphere pollution monitoring level in China.