Study On Thermodynamic Characteristics Of Coal Gangue During The Heating Process Of Oxidation

Coal gangue is the associated product in the process of coal mining and processing.China is a big country of coal production.Due to the lack of effective and large-scale utilization of coal gangue,a large number of coal gangue piles have been formed.Once spontaneous combustion occurs,it will seriously endanger the safety of people's lives and property and the environment.At present,there are more researches on coal oxidation and spontaneous combustion,but less on coal gangue,which leads to the lack of sufficient theoretical support for coal gangue fire control.In this paper,the coal gangue collected from Pingshuo east open pit mine is taken as the research object,and the effects of particle size,pyrite content,coal content and water content on the oxidation spontaneous combustion of coal gangue are systematically studied by combining theory with experiment.Firstly,the spontaneous ignition mechanism of coal gangue is theoretically analyzed.In the incubation period,the coal gangue absorbs oxygen physically and chemically,and the combustible materials such as pyrite and residual coal react slowly.When the good heat storage conditions are available,the adsorption heat and the heat released by oxidation make the temperature of coal gangue rise slowly;when the temperature rises to the critical temperature,the gangue enters the self heating period,and the chemical adsorption and oxygen are absorbed The reaction rate increases rapidly and the heating rate is accelerated;when the temperature reaches the ignition temperature,the coal gangue will burn;the porous property of the gangue,the carrying effect of natural convection and the diffusion of gas molecules ensure the sufficient oxygen supply in the reaction area.Next,temperature-programmed experiments were carried out on coal gangue with different particle size,pyrite content,coal content,and water content,and analyzed its oxidation gas product generation concentration,intersection temperature,oxygen consumption rate at 70°C,and a comprehensive judgment index of spontaneous combustion tendency.It is found that the smaller the particle size of coal gangue,the higher the coal content,the greater the concentration of CO gas generation,the lower the temperature at the intersection,the greater the rate of oxygen consumption,and the greater the tendency for spontaneous combustion;as the pyrite content in the gangue increases,The temperature at the intersection first decreases and then increases.The CO gas generation concentration,oxygen consumption rate,and spontaneous combustion tendency increase first and then decrease.The pyrite content reaches an extreme value when the pyrite content is 6%;as the water content in the coal gangue increases,The temperature at the intersection first decreases and then increases,the CO gas generation concentration,oxygen consumption rate,and spontaneous combustion tendency first increase and then decrease,and the extreme value appears when the water content is 7.94%.Finally,the TG-DSC combined technology was used to analyze the characteristic temperature,comprehensive combustion characteristic index,and heat release rate of coal gangue with different particle sizes,pyrite content,coal content,and water content.It was found that the smaller the particle size of coal gangue,the more the coal The higher the content,the lower the characteristic temperature,the increase of the comprehensive combustion characteristic index,the faster the heat release rate,and the increase of heat release.With the increase of the pyrite content in coal gangue,the characteristic temperature first decreases and then increases,the comprehensive combustion characteristic index and heat release rate first increase and then decrease,and the extreme value appears when the pyrite content is 6%;With the increase of water content in the gangue,the characteristic temperature first decreases and then increases,the comprehensive combustion characteristic index and heat release rate first increase and then decrease,and the extreme value appears when the water content is 7.94%;the results of the thermal analysis experiment and the temperature programmed experiment are consistent.This paper has 30 pictures,19 tables and 81 references.