Influence of associated metal elements in coal on low-temperature oxidation characteristics of coal

Two kinds of inorganic salts with 7 representative metal ions were selected for studying their inhibition effect on spontaneous combustion of coal.100 g Xutuan bituminous coal was treated by 1g additives.Oxygen consumption,DSC and inhibition rate were compared before and after treatment for evaluating their inhibit effect during low-temperature stage.Oxidation kinetic parameters was calculated.Combined with free radical theory,the mechanism that metal elements influence on spontaneous combustion of coal was presented.The results showed that the inhibition ratios of Mg,Zn,Ca,Al,K and Na were between 9.5% and 57.9%.The maximum activation energy of low temperature during 30～180 ℃ increased by 29.6%.The mentioned metal inorganic salts reacted with coal molecules to form stable complexes and enhanced the stability of active structures.It can also inhibit coal oxidation by capturing active molecules such as hydroxyl radicals.Besides,the electron transfer caused by the conversion of manganese ion under polyvalent states has a certain promoting effect on coal spontaneous combustion.