Research Of Gas Continuous Emission Monitoring System Based On UV-DOAS

Differential Optical Absorption Spectroscopy (DOAS) is an optical method which uses thegas molecules in the UV/visible absorption band to accurately measure the gas concentration.In the detection of gaseous pollutants, the method has broad application. Monitoring of fluegases is an important basis for environmental protection. Based on UV-DOAS technology, thispaper conducted a study on the theory of the Continuous Emission Monitoring System (CEMS)and technology. Through the DOAS principle, the model of the absorption spectrum,theanalysis of spectral data processing, this paper presents the gas based DOAS measurementsand model calculations. In the system implementation process, the difficulties are mainly:algorithm of CCD pixel positioning; eliminate dust and moisture effects; high-speed spectral dataacquisition; measurement error of the control.The main contents of this article and innovation:1. This paper analyzes the Lambert-Beer’s law of theoretical models and measurementmodels. By studying the Rayleigh scattering and Mie (Mie) scattering for the absorptionspectra,the paper won the the test model which contains Rayleigh scattering and Mie scattering. Bymodifying the measurement model, this can eliminate the Rayleigh scattering and Mie scatteringmeasurements of the gas. we can get accurate spectra through the holographic grating.2. This paper research the application of holographic gratings in the spectral splitting.Meanwhile, for accurate of the test results, we adopted the principles of various opticaldevices and performance of detailed analysis in order to make the appropriate selection. Byderivation, we can determine the holographic grating model, the calculation to determine thespectral position of the CCD.3. Through the hardware design, component-driven timing analysis and interface-driven design, spectrum acquisition module achieved high-speed data acquisition and accuracy,avoided errors and capture errors.4. Based on DOAS principle, this paper presents a suitable flue gas SO2and NOxcalibration methods in order to improve the accuracy of the flue gasmonitoring. Throughcalibrating gas data, the system reached the practical requirements.5. We designed a Continuous Emission Monitoring System. According to the demand, wedesigned the hardware and software of the system. By testing the system, we determine theactual performance of the system.