Effect of water-soluble sodium on combustion characteristics of high-alkali coal and model compounds

Xinjiang Zhundong high-alkali coal has a high content of sodium, calcium and other alkali metals and alkaline earth metals. Sodium in high-alkali coal exists in four forms, namely water-soluble state water-saluble state Na, ammonium acetate state, hydrochloric acid state and insoluble state, in which water-soluble state Na accounts for up to 82% that is easy to remove by water washing. water-soluble state Na has a significant impact on the precipitation rate of the volatiles in the combustion process, as well as on the ignition temperature and burnout temperature.To further study the effect mechanisms of Water-soluble state Na on the combustion characteristics of Zhundang deashed coal（DC）,a differential scanning calorimeter and mass spectrometer （DSC-MS） were used to carry out combustion experiments.The DC and model coal（MH）were employed as comparative samples,and the ignition temperature,burnout temperature,maximum combustion rate,comprehensive combustion characteristic index and other combustion characteristic parameters were analysed.Besides,the reaction kinetics of combustion were calculated and analysed by Coats-Redfern integral method.The results show that the average weight loss rate and comprehensive combustion index of MH and DC are in good agreement,namely that model compounds can be used to replace high-alkali coal to study combustion characteristics and pollution emission characteristics.Secondly,sodium has no significant effect on the volatilization analysis stage of DC and MH,but promotes the combustion of fixed carbon.Thirdly,the kinetic analysis verified that the reaction order of DC and MH are level 1.Fourthly,it can be negligible that the effect of sodium on the devolatilization and ignition stage that correspond to the stage before 490 ℃ and 530 ℃,respectively,but it has a degree of effect on the combustion of fixed carbon.