Study on the co-combustion mechanism of coal gangue and coal gasification fly ash based on thermogravimetric mass spectrometry
The combustion characteristics and gas release characteristics of the Wuhai coal gangue,the Suqian coal gasi-fication fly ash,and their mixtures were revealed by thermogravimetric mass spectrometry analysis.The co-combustion mechanism of the Wuhai coal gangue and the Suqian coal gasification fly ash was studied by combining the physicochem-ical properties of the two fuels.The thermogravimetric analysis results indicate that the Wuhai coal gangue has better igni-tion characteristics than Suqian coal gasification fly ash.The ignition characteristics of the mixtures are improved by the Wuhai coal gangue,while the high-temperature combustion characteristics are improved by the Suqian coal gasification fly ash.The combustion kinetics were analyzed based on the Coats-Redfern(C-R),Flynn-Wall-Ozawa(FWO),and Kis-singer-Akahira-Sunose(KAS)methods.The results show that the apparent activation energy of the Wuhai coal gangue is 48.25-152.22 kJ/mol,and the combustion reaction conforms to the Jander model.The apparent activation energy of the Suqian coal gasification fly ash is 106.34-312.79 kJ/mol,and the reaction conforms to the reaction level model with n=1/4.When the mass ratio of the Wuhai coal gangue to the Suqian coal gasification fly ash was 1∶3,the apparent activa-tion energy was 102.24-301.58 kJ/mol,which corresponds to the synthesis of a nuclear growth model.The interaction of these fuels was examined by comparing the deviation between the theoretical and experimental weight loss rate of mix-tures.The results show that there is a significant coupling effect between the Wuhai coal gangue and the Suqian coal gasi-fication fly ash,mutually enhancing their combustion characteristics.This promoting effect is gradually strengthened with the increasing mass proportion of the Suqian coal gasification fly ash.Based on the comprehensive co-combustion charac-teristics and gas release characteristics,the better mass ratio of the Wuhai coal gangue to the Suqian coal gasification fly ash is 1∶3.NH3 is released during the volatile fraction and fixed carbon combustion process.The temperature corres-ponding to the peak intensity of the NO and NO2 release is essentially consistent with the temperature corresponding to the maximum reaction rate on the thermogravimetric curve.
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