Influence from Fragmentation,Oxidation and Ultraviolet to Free Radical of Coal

Based on the mechanism of free radical reactions in spontaneous combustion of coal,the concentration of paramagnetic center was measured by electron spin resonance(ESR) spectroscopy at X-band(9.3 GHz) during the process of fragmentizing,low-temperature oxidizing and ultraviolet radiating.The results show that the smaller coal size,the higher oxidation temperature,and the longer oxidation time,the higher concentration of paramagnetic center are able to form free radicals.Oxidation temperature is the leading factor for initiating free radicals of coal,and the effect is more notable after 125℃.The free radicals of coal are also very sensitive to the ultraviolet.The concentration of free radicals increases sharply just in 10 minutes at the beginning and finishing ultraviolet radiation.Furthermore,some phenomena during the process of spontaneous combustion are explained.4figs.,1tab.,11refs.