Thermogravimetric and Infrared Spectral Analysis of Candle Coal Pyrolysis Under Low-oxygen Concentration

Abstract For further understanding spontaneous combustion of coal in fire suspectable zone, this paper analyzed coal pyrolysis in low-oxygen conditions by thermogravimetric analysis and online FTIR. The results indicate that the oxidation and pyrolyzation of candle coal occur simultaneously at 3%∼5% oxygen concentration, the intensity of oxidation reaction can still promote the coal self-heating. With the decrease of oxygen concentration and temperature, the C=C on benzene ring decreases while the oxygen-containing groups increase. With oxygen concentration decreasing continuously, the oxygen-containing groups begin to appear surplus. When the temperature rises to 500°C, the content of -COOH and -OH still remains 0.3% under 3% oxygen concentration, but disappears at 5% oxygen concentration. It indicates that 3% oxygen supply cannot provide necessary oxidation conditions for candle coal. Consequently, in order to fully suppress the development and re-burning of underground coal fire, the oxygen concentration should be controlled below 3%.