Study On The Key Technologies Of Continuous Emissions Monitoring System

Air pollution monitoring and controlling issues are given more and more attention in various countries around the world. There are two main reasons for air pollution: First, the coal burning boiler emissions, like dust, sulfur dioxide and nitrogen oxides; the other is the motor vehicle emissions. And the various types of combustion, such as the flue gas emissions of industrial and commercial boilers, cause the serious air pollution problem. In this case, the flue gas monitoring is an important aspect of environmental protection. On the basis of ultraviolet difference spectrum measurement, the key technologies of flue gas emissions measurement technology for real-time monitoring system are analyzed in the aspects of the theoretical and experimental research. The main content and innovation points are as follows:1. The theoretical model of Lambert-Beer Law is studied in the actual measurement condition. When the light emitted from the source transmitting through the flue gas, the attenuation caused by Rayleigh scattering and Mie scattering is larger than that of molecular absorption in the total contribution. These effects will be considered to join the relative measurement model to improve the accuracy of theoretical calculation.2. In comparison with the optical structure of the current measurement probe of SO2 and NOx gas concentration, a new single plug-in double-sided probe is designed to reduce the high temperature deformation of the probe, which can disturb the light path. This design makes the field mounted and fixed more convenient, which also increases the stability of the system. .3. For the nonlinearity of practical condition causes deviation from theoretical law, a new calibration method is introduced. This method transfers the change in gas length to the change in gas concentration. The high-precision probe calibration is realized by this method. A number of proof tests of SO2 and NO are taken with the calibrated probe. The average concentration deviation is less than 2%4. The spectrum self-adapting algorithm is presented. The impact of flue dust to the received light is solved by adjusting the integration time automatically. And the life length of the source is increased. The drift of the spectrum is corrected by analyzing and comparing the wavelength location of the spectrum feature, when extracting the invariants in the spectrum as the features.5. The measurement technologies of the particulate content, oxygen content and flow rate are introduced in detailed. The control circuit of the oxygen content sensor is designed.6. The Continuous Emissions Monitoring System is developed. According to national standards, a monitoring and controlling software system is programmed. The application experiments are taken in two power plants, monitoring the flue gas in these two plants continuously, which adopt the different desulphurization methods. And the monitoring data is analyzed.