Research On Photoelectric Detection Technology Of Flue Gas Mixture With High-precision

With the development of industrial production, the amount of sulfur dioxide (SO2) and nitrogen dioxide (NO2) emissions into the air becomes more and more, which has great harm to the atmospheric environment. The concentration of SO2 and NO2 in flue is one of the important references to measure the level of flue gas pollution. Therefore, it is necessary to accurately and stably measure the concentration of them.In this paper, we firstly investigate and survey the historical progress of differential optical absorption spectroscopy. And then,advantages and disadvantages of the methods for detecting various fields of gas concentration are comparatively analyzed. Finally, the three channels UV differential optical absorption spectroscopy is chosen to detect the concentration of NO2 and SO2-A complete set of experimental test and data acquisition system is established, including: three channels gas measurement device, LED drive circuit, signal reception circuit, microcontroller circuit and Labview display system. The central wavelength of LED ultraviolet light source in each channel of the gas measurement device is not the same. And, detectors are installed at the front and rear of the each channel, which can detect the intensity of the incident and exit lights at the same time. The detected analog signal is acquired by three internal 12 bit AD in MSP430F149 microcontroller after the amplification filter circuit. After that, the original data is sent to the computer through the Zigbee module. In further, the computer calculates the concentration of the measured gas according to the software compiled by Labview, and displays the change curve with time, which means the concentration measurement of flue gas can be realized.Finally,taking the SO2 standard gas as an example,the measurement of the concentration of harmful gases was realized by using the experimental data acquisition system. The measurement results show that the error of SO2 standard gas concentration is relatively small when the device is not controlled. In addition, the influence of temperature on the UV LED and the measurement error is studied. It was found that the central wavelength of LED would be red shifted with the increase of temperature, and the solution of PID temperature control was proposed.