The variation characteristics of free radicals in coal oxidation

The variation of free radicals concentrations were studied using an electron spin resonance (ESR) spectrograph as dry air passed through the coal samples of the various spontaneous combustion liability at room temperature,meanwhile the variation of free radicals were studied in the changing temperature during oxidation.The test results and oxidbillity of coal samples were also analyzed.The results show that coal takes place reaction of free radical,once contacting with oxygen at room temperature,which results in the increase in the concentration of free radicals,the increment of free radicals concentration enlarges as the concentration of free radicals increase in original coal,but there is no direct correlation with the initial oxidation capacity of coal.In oxidation,the concentration of free radicals in various coals have differing values as the temperature changes,some coal’s free radicals concentration decreases with the increasing of temperature,and then increases;the oxidation capacity of coal can not be simply measured by the free radicals concentration magnitude or the change rate of free radicals during oxidation.