Study On Explosion Characteristics And Micro Reaction Mechanism Of Coal Dust

China’s coal resources are rich and widely distributed,including coal samples with different metamorphic degrees from lignite to anthracite.It is easy to produce suspended coal dust in the transportation,processing,and utilization of coal resources.Under certain conditions,suspended coal dust has the explosion ability.Explosion accidents often cause heavy casualties and property losses.Therefore,the research on the explosion characteristics and reaction mechanism of coal dust is of great significance,providing a theoretical basis for the safe utilization of coal resources and the prevention and control of explosion accidents.In this thesis,various coal samples with different metamorphic degrees were selected.The explosion characteristic parameters of coal dust were tested and analyzed.The changes in surface morphology,elements,and micro functional groups before and after the coal dust explosion were compared and analyzed by SEM,industrial analysis,FTIR,XPS.After the coal dust explosion,the gas composition was tested by gas chromatography,and then the toxic and harmful effects were investigated.The coal dust explosion reaction mechanism was studied from coal dust pyrolysis volatile gas and the structure of the main functional groups in micro macro-molecules.Based on the volatile components obtained from the TG-MS experimental test,Chemkin-Pro simulation software was used to analyze the explosion reaction process of coal dust pyrolysis volatile gas,simplify the key elementary reaction,and construct the reaction path of volatile pyrolysis gas.Based on quantum chemistry theory,the structure of coal macro-molecules was constructed and simplified.The structure,reaction path,and thermodynamic parameters of main functional groups in coal macro-molecules were explored.The macro,meso,and micro four-stage coal dust explosion reaction mechanism was proposed.The main research results are as follows:（1）Coal with different metamorphic degrees has different explosion characteristics related to the coal composition.Combustible components such as volatile and fixed carbon in coal can promote the explosion intensity of coal dust.In contrast,moisture and inert components will inhibit the explosion intensity to a certain extent.In addition,the explosion intensity of coal dust is related to the coal dust reaction concentration.There is an optimal reaction concentration,which corresponds to the maximum explosion pressure of coal dust.If the optimum reaction concentration is exceeded,the explosion intensity of coal dust will show a decreasing trend due to the state of oxygen-poor and fuel-rich.（2）Before and after the coal dust explosion,the particle surface morphology changes from the smooth plate and block structure to a rough,loose spherical hole structure.The main components of gas products after coal dust explosion are CO₂,CO,and CH₄,and there is also a small amount of C₂H₄,C₂H₆,and C₂H₂.The contents of CO and hydrocarbon gases increase gradually with the increase of coal dust concentration.Hypoxia asphyxia and the existence of toxic and harmful gases after the coal dust explosion pose a significant threat to human health and life safety.The distribution of surface elements changed significantly,the fatty chain shortened,the content of C-H decreased,the content of thiophene sulfur decreased.Pyrrole nitrogen（N-5）transformed to pyridine nitrogen（N-6）with higher thermal stability.During the explosion,the absorption peaks of oxygen-containing functional groups,aliphatic,hydroxyl,and aromatic structures weakened.The intensity of absorption peaks of oxygen-containing functional groups weakened significantly,and some even disappeared.The intensity of ash and mineral absorption peaks increased significantly.（3）The coal dust pyrolysis stage’s weight loss characteristics and volatile gas escape process are tested and analyzed.The coal dust pyrolysis process is divided into three stages.The second stage（350-575℃）has the fastest pyrolysis rate,the most considerable amount of volatile gas,and the reaction activation energy is 78.87 kJ/mol.Zero-dimensional constant volume and one-dimensional laminar flow constant pressure simulation were carried out for the mixed explosion process of main volatile gas components produced by the coal dust pyrolysis.The changes in temperature,pressure and reaction components in the coal dust explosion reaction were revealed.Based on the sensitivity and ROP analysis results of reactants,intermediates,and products,22 key elementary reactions were extracted,and a simplified path of volatile gas explosion reaction was constructed.（4）Based on the industrial analysis,elemental analysis,XPS,and solid-state NMR test results,the macromolecular structure of the DY coal sample was constructed and optimized.Frontier orbital analysis was carried out to determine the reaction active sites for the main functional groups in the coal macro-molecular structure.Then,the reaction paths of each functional group were analyzed.Based on quantum chemistry theory and calculation method,the thermodynamic parameters of each reaction were calculated and then determined the reaction order.The macro,meso,and micro four-stage coal dust explosion reaction mechanism was proposed.（5）The key elementary reactions affecting the heat accumulation and reaction process in the process of coal dust explosion were extracted,and the relationship between micro reaction mechanism and macro characteristics was discussed.The key reaction paths of carbon oxide generation were analyzed.CO mainly comes from the aldehyde radical,and CO₂primarily comes from the carboxyl radical.The reaction of fat structure with oxygen to produce peroxide radical is the key elementary reaction of heat accumulation in the early stage and carbon oxide formation.From the perspective of the micro reaction mechanism,according to the characteristics of each reaction stage,the principle of the explosion suppression method combining chemical suppression and physical suppression is proposed.The key active radical carrier in the reaction process is consumed,and the heat transfer between coal particles is blocked to prevent and control the occurrence and development of coal dust explosion accidents.