Thermal Analysis Kinetics Of Low-rank Coal Spontaneous Oxidation

Spontaneous combustion of coal is a complex dynamic process.It is useful to analyze and master the dynamics of coal oxidation.Three kinds of low rank coal and two kinds of coal with higher degree of metamorphism are taken as the object of study.The Coats-Redfern integral equation is used to deduce the most probable mechanism function of coal spontaneous combustion.The result shows the first stage of low-rank coal belong to the once-order chemical reaction and the second is three-dimensional diffusion mechanism function.It is found that the activation energy of low rank coal is lower than others.With the temperature increasing,activation energy is increased and the preexponential factor also increases.It is found that the low-temperature oxidation of coal has undergone the process of endothermic and exothermic.The rate of heat generation increases with the increasing temperature the initial exothermic temperature of low rank coal is lower,while the total heat release is higher than that of other coal.The test of oxidation simulation and infrared spectroscopy shows that the first gas in the oxidation process is CO with the temperature rising,the CO production gradually increases,and hydrocarbon gas also generates.Most content of low-rank coal molecular structure is aliphatic hydrocarbons and oxygen-containing functional groups,and these two groups also of higher activity.It is inferred that CO is mainly derived from aldehyde group,while the hydrocarbon gas is mainly derived from the breakdown of the fatty chain.Low-order coal is of poor stability,and the structure is complex,it is also easy to break down and generate large amounts of gas.The oxidation of coal is a multi-step reaction,and different steps are competing and interrelated.The reaction rate increases with the increasing temperature.The number of molecules involved in the reaction also increases.