Research On The Safety Mechanism Of Dry Pulverized Coal During Transportation And Storage

In 2016,the total amount of energy consumption in China was up to 43.6 million tons of standard coal,coal was 62%,occupying the absolute main position.In coal staged utilization system,spontaneous combustion accidents happen easily in the process of pulverized coal transportation and storage,which not only cause economic losses and environmental pollution,but also cause casualties.Because the physical and chemical structure of coal is very complex,the spontaneous combustion process involves a variety of physical and chemical changes.So far,the spontaneous combustion characteristics of coal have not been unified.Therefore,the research on the spontaneous combustion of pulverized coal is of great significance and urgency.In order to study the reaction process and mechanism of coal oxidation and spontaneous combustion in coal staged utilization system,the TG-DTG curve of coal spontaneous combustion process was obtained by using thermogravimetric analysis to simulate the whole process of coal spontaneous combustion in the running pipe and the coal bunker of the gasification pyrolyzer.The spontaneous combustion process of coal powder oxidation was studied,and the reaction mechanism of weightlessness during the process of spontaneous combustion of coal was analyzed by Malek method.The results show that the process of coal oxidation spontaneous combustion can be divided into four stages,the stage of water loss,the stage of oxygen absorption and weight gain,the stage of pyrolysis and the rapid combustion stage.The most probable mechanism function of the water loss stage is obtained by using the Malek method,and the correctness of the most probable mechanism function is verified by the drawing method.The reaction mechanism of coal oxidation and spontaneous combustion is studied by parallel competition reaction theory.The TG-DTG curve is fitted by Gauss multimodal fitting and the kinetic parameters of all parallel reactions are determined by peak value analysis.The results indicate that according to the method of Gauss fitting,the spontaneous combustion process is decomposed into 3 fitted peaks,corresponding to the oxidation weight reaction,pyrolysis reaction and rapid combustion reaction,the fitting effect is very good;the peak analysis method is used to determine the activation energy and the reaction order of each parallel competitive reaction.The activation energy increases with the increase of the temperature of each parallel reaction,and the reaction progression of the 3 parallel competitive reactions is less than 1.In order to study the influence of category of coal and particle size on the characteristics of spontaneous combustion in coal staged utilization system,the influence of coal particle size on the characteristic temperature of pulverized coal spontaneous combustion was studied by simulating the pulverized coal spontaneous combustion process in the running pipe and the coal bunker of the gasification pyrolyzer by thermogravimetric experiment.The results indicate that with the coal metamorphism degree deepens,the characteristic temperatures of coal spontaneous combustion process increase.With smaller particle size,the TG curve of the pulverized coal spontaneous combustion moves to lower temperature,but the particle size is less than a critical value,the TG curves of coal particle size are coincidence;spontaneous combustion characteristic temperatures of pulverized coal decrease,but when the particle size is smaller than a certain value,effect of particle size on the characteristic temperature weaken.Using the thermal simulation experiment to investigate the influence of heating rate on the spontaneous combustion characteristics in the coal bunker of the gasification pyrolyzer in the coal staged utilization system,the result shows that the characteristic temperatures of coal spontaneous combustion process increase with higher heating rate;the regression relation between different heating rate and the pulverized coal spontaneous combustion activation energy accord an exponential function,the activation energy decreases rapidly as the heating rate increase.To observe the morphology of coal sample surface by scanning electron microscope,the results show that the surface structure of low metamorphic degree of coal is loose and porous;pulverized coal were oxidated under different temperature of tube furnace,pulverized coal samples obtained after the reaction,the coal samples were tested by FTIR infrared spectra,the law of functional reaction of coal spontaneous combustion process was obtained.