Interaction and kinetics during the co-combustion process of coal slime, coal gangue and slack coal

The combustion and co-combustion characteristics of coal slime, coal gangue and slack coal were studied by thermogravimetric experiments, and the interaction and kinetics during the co-combustion process were analyzed.The results showed that the combustion process of coal slime and slack coal was divided into one stage, corresponding to the combustion of volatiles and char, while the combustion process of coal gangue was divided into two stages: combustion of volatiles and char and decomposition of silicate mineral.The ignition temperature of coal gangue was the highest among the three fuels, while the ignition temperature of coal slime and slack coal were relatively close, but the burnout temperature of the three fuels arranged in descending order was: slack coal>coal slime>coal gangue.In terms of the comprehensive combustion index and the combustibility index, the combustion performance of slack coal was the best, followed by coal slime, and coal gangue is the worst.During co-combustion, the experimental values of the ignition temperature and the burnout temperature of the blended fuels were lower than the theoretical values, while the experimental values of the comprehensive combustion index and the combustibility index were higher than the theoretical values.Besides, there was a positive linear correlation between the comprehensive combustion index and combustibility index of the blended fuels with fuel ratio(Ratio of fixed carbon to volatile matter content).Meanwhile, there existed obvious interaction between the three fuels at 400-800 ℃,when they were mixed in pairs, the interaction between coal slime/coal gangue or slack coal/coal gangue was stronger than that between coal slime and slack coal, when the three fuels were mixed, the interaction became stronger as the proportion of coal gangue or slack coal increased.Kinect analysis indicated that the chemical first order reaction(O1) was the most effective mechanism for the combustion and co-combustion of coal slime, coal gangue and slack coal.For individual combustion, the activation energy of coal slime and slack coal are 69.6 kJ/mol and 63.8 kJ/mol, respectively, while the activation energy of coal gangue is higher, which is 85.3 kJ/mol.The activation energies of the blends are ranging from 63.2 to 76.3 kJ/mol, and the experimental activation energy of the blends were lower than the theoretical one.