Research On Coal Temperature Monitoring In The Goaf Based On Optical Fiber Pyrometer

Fire in goaf is the commonest and the hardest to find, compared with other fire in different underground places. It’s effective to prevent the coal spontaneous combustion when the temperature around the coal is monitored and the outliers of the temperature are found out in the early of spontaneous combustion, which are proved by practice. However, the fire monitors of coal mine are multi-point discrete type, which will leak a lot of information. Optical fiber pyrometer, as a kind of new technique that can realize real time and online continuous temperature monitoring, has been widely used in the transmission lines fire monitoring, and tunnel fire monitoring, and works effectively. Some coal mines also started to monitor the temperature in goaf. But the issues of selection of proper optical fiber pyrometer, proper arrangement of optical fiber in the goaf have not been studied thoroughly.Based on the research of existing widely-used optical fiber pyrometer and the specific requirements of fire monitor in goaf, optical fiber pyrometer for mine, based on Raman scattering technique, is proposed. The principle of Raman optical fiber pyrometer technique was deeply researched, and the existing arithmetic of demodulating information of optical fiber’s temperature was optimized.Based on the analysis of factors of optical fiber pyrometer performance, the three critical indexes that if the system can be used in the goaf were found out: accuracy of locating fire places, accuracy of temperature measuring, and the speed of collecting temperature information to demodulating the information. The performance indexes were studied through the water bath heating experiment, which indicates that the system satisfies requirements of coal mines.Temperature measuring system was designed based on the temperature measuring principle. The relationship among the system parts and the factors influencing on the selection of system hardware were studied. The study results provide a theoretical basis for further optimization of the system. Aiming at the deficiencies of fiber arrangement in goaf, four ways of fiber arrangement were designed. On the basis of comparison of the four ways, the best way for fiber arrangement was selected and used in the mine. The measuring results showed that the selected arrangement way satisfies the need of goaf fire’s monitoring well.