Research On The Dynamic Of Lignite Coal Dust Explosion Flame Propagation

Energy is the material basis for the survival and development of human society.The energy structure of our country takes coal as the core.However,in recent years,coal mining accidents occur frequently,which seriously threaten the country’s energy security and the safety of people’s lives and property.As one of the main disasters in underground mining,the coal dust explosion has attracted extensive attention because of its strong destructive,and easy to form secondary explosion.To better understand the explosion characteristics and mechanism of the coal dust cloud,and provide a theoretical basis for safe mining and disaster prevention.This paper took the lignite coal dust as the research object,firstly,the particle size analysis,industry analysis,and elemental analysis for coal samples were carried out by modern analysis means.Then,the effects of different influencing factors on the coal dust cloud explosion flame propagation were analyzed through a dynamic test system of dust cloud explosion flame.Finally,the thermodynamic mechanism of coal dust was explored by the Reax FF molecular dynamics simulation method（Reax FF-MD）.The main conclusions are as follows:（1）With the increase of coal dust cloud concentration and ignition delay,the flame propagation height and speed of coal dust cloud explosion firstly increased,and then decreased.With the increase of ignition energy,the flame propagation height and speed of coal dust cloud explosion increased continuously.However,with the decrease of coal dust particle size,the flame propagation height and flame propagation speed of coal dust cloud explosion also increased ceaselessly.（2）In the study of the thermodynamic mechanism of lignite coal dust,it was found that the structure of macromolecular coal was gradually decomposed.The aromatic rings,C-C,C-O,and C-H bonds,etc were fragmented and smaller molecular structures were produced such as H₂,H₂O,CO₂,CH₂O,etc.In the pyrolysis and combustion reaction system,the main products were H₂ and CO₂,respectively.In addition,it was also found that with the increase of temperature,the pyrolysis and combustion reaction of coal molecules were promoted.（3）Through the comparative analysis of the main reaction paths of lignite pyrolysis and combustion,it can be obtained that the most frequent reaction was O₂+H→HO₂,and the main generation path of H₂O was the instability of·HO₂ radical prompted it to react with·HO radical（HO₂+HO→H₂O+O₂）.Besides,the main generation sources of CO₂ were the further decomposition of·CO₃,·CHO₃ free radicals,and the further oxidation of CO.In the pyrolysis reaction system,the most frequent reaction was H₂O+H→H₂+HO,and it was the main generation path of H₂.Besides,the main generation sources of CO₂ were the further decomposition of·CO₃,·CHO₃ free radicals,and the further oxidation of CO.In addition,part of H₂ was the combination of·H formed by·CHO、·CH₃O、·C₂H₃O free radicals and H₂O（H+H→H₂）.