Key Technologies Of Industrial Gas Monitoring Based On Absorption Spectroscopy

With the development of industry, air pollution problems have becomeincreasingly prominent in recent years, which not only seriously affects people’s dailylives, but also greatly restricts the sustainable development of the society. As one of themain polluting gases, carbon monoxide is widespread around people’s livingenvironment, and high level of carbon monoxide can lead to significant damage topeople’s healthy. So it’s urgent to monitor and control the emission of carbonmonoxide.Currently, the detection of carbon monoxide gas is relatively mature, but still cannot meet requirements of on-line monitoring and high-sensitivity in complex industrialsite. Tunable diode Laser absorption spectroscopy has advantages of high selectivity,online measurement, high sensitivity, fast response and so on. After nearly30years,this technology has been widely used in atmospheric chemistry research and pollutinggases monitoring, and become a common atmospheric trace gases monitoringtechnology with high sensitivity. Furthermore, the laser gas analyzers have beenresearched and developed by many well-known instrument manufacturers. This thesisaimed to develop a carbon monoxide detection system based on absorptionspectroscopy technology with independent intellectual property rights, which not onlytheoretically verified the feasibility of gas concentration detection based on absorptionspectroscopy techniques combining with a rigorous mathematical derivation, but alsodesigned experimental system of gas concentration detecting based on absorptionspectroscopy.This research work mainly carried out from three parts. First, theoretical studiesof the gas concentration detection method based on absorption spectroscopy were done,which clarified a mechanism that the laser light intensity signal was absorbed by gasmolecules from the molecular perspective. In this part, the Lambert-Beer law wasdescribed, which is the theoretical basis of absorption spectroscopy. Second, designscheme of carbon monoxide detection system, design concept and the hardwareconfiguration was introduced, this thesis made a detailed presentation on the maincontrol unit and the light source module. As the single central processing unit is slowand difficult to meet requirements of multi-channel sampling and multi-parametercomplex computing in this system, this work used a dual central processor to improve the reliability and speed of the system. The gas concentration was calculated accordingto the recorded second harmonic signal, which was more in line with actualengineering. As the signal to noise ratio of second harmonic is relatively low when thegas concentration is low, this work designed filter algorithm based on Fouriertransform. Moreover, the temperature and pressure compensation algorithm wasintroduced to fit the complex industrial site with high temperature and pressure. Third,the second harmonic signal of carbon monoxide gas was acquired and analyzed by thissystem. Concentration measurement results showed that the designed gas concentrationdetection system based on absorption spectroscopy could accurately measure theconcentration of carbon monoxide gas.This thesis designed a gas concentration detection system of carbon monoxidebased on based on absorption spectroscopy technology. Precision and accuracy of thesystem was detected and manifested by the gas concentration inversion results. Finally,some suggestions were presented on how to complete the conversion fromexperimental verification in the lab to practical application in the industrial site.