The difference of spontaneous combustion liability of fresh samples (SA) and pre-oxidation samples (SB) of lignite upgraded at different temperature

were tested by the experiment equipment of temperature programming.Free radicals in situ were dynamically analyzed by X-band electron spin resonance spectroscopy (ESR) and the effect of pre-oxidation on spontaneous combustion liability was surveyed.The results showed that the spontaneous combustion liability of SA reduced with rising upgrading temperature.With the storage time extension in natural environment

lignite upgraded at 105-500℃ was effected by pre-oxidation.The spontaneous combustion liability increased in varying degrees

and lignite upgraded at 400℃ became easy to spontaneous combustion as well as raw lignite.During the oxidation process of spontaneous combustion

being different from fresh samples

the free radical concentration for pre-oxidation samples increased with increasing adsorbed oxygen amount.Pre-oxidation not only improved the free radical amount of upgraded lignite

but also made the continuous generation of new free radical and kept the self-heating and temperature rising in the later part of accelerating oxidation phase.But micromolecule free radicals were rapidly consumed and loss 80% for the fresh sample upgraded at 400℃

which made it could not provide new free radicals and maintain oxidation reaction.