Study On Influencing Factors Of Coal Dust Explosion Based On Zhangshi High Speed Tunnel Accident

With the increasing application of powder technology,dust explosion often occurs in the process of production,processing,storage and transportation of modern industry.Dust explosion is powerful and destructive.Therefore,a thorough understanding of the essence,explosive characteristics and influencing factors of dust explosion accidents will help to prevent the occurrence of related accidents,reduce the harm caused by accidents,and provide a scientific basis for the investigation and evaluation of accidents.Based on the explosion accident of Zhangshi high-speed tunnel and combined with the accident investigation report,this paper takes the coal dust explosion characteristics as the main line of research.The influence of particle size parameters,combustible gas（CH4）,oxidizer（NaClO3）,environmental temperature and humidity on the coal dust explosion were studied by using the 20 L spherical explosion test system.The main work and conclusions are as follows:（1）The influence of particle size parameters on the explosion characteristics of pure coal dust was studied.Under the same dust concentration,the smaller the median particle size is,the larger the P_ex and（dP/dt）_ex values of explosion are,and the optimal concentration of dust explosion is lower（400 g/m³）.For the same median particle size（95 μm）,when the dispersion of particles is larger,the P_ex and（dP/dt）_ex values of explosion are larger,and the power of dust explosion is greater.The relationship between particle dispersion σ_D and explosive characteristic parameters P_max and K_st increases linearly.However,in the case of different particle dispersion σ_D,it is found that the dust particle parameters D_3,2 can more fully describe the variation trend of the coal dust explosion characteristic parameters P_max and K_st than D₅0 and D_4,3.Therefore,the parameters D_3,2 and σ_D should be taken into account when assessing the risk of such dust explosion accidents.（2）The explosion characteristics of coal dust/gas mixture was studied.For pure gas explosion characteristics under different gas concentrations,the P_max and（dP/dt）_max are 0.58 MPa and 80.23 MPa/s,respectively,and the optimal gas concentration is 10 vol.%.At the optimum concentration,the（dP/dt）_max of gas explosion is 9 times that of coal dust explosion,but with the increase of gas concentration,the gas explosion is seriously inhibited.The mixed explosion will be more promoted with the higher the oxygen content.The explosion combustion process of coal dust/gas mixture is actually heterogeneous combustion.The gas reacts with oxygen first to generate heat and heat the preheating area to form devolatilization.And then in the reaction zone,coal dust particles,volatiles of coal dust particles and gas coexist in combustion.（3）The effects of sodium chlorate,ambient temperature,air humidity and gas on coal dust explosion were studied.It is found that the presence of sodium chlorate increases the severity of coal dust explosion to a certain extent,and the P_max value of mixture explosion increases by 23.9%and 20.4%respectively.But the explosive power of the mixture is weakened by the increase of its decomposition product（NaCl）.Appropriate air humidity can promote the reaction between coal dust and water,and improve the explosive power of coal dust/sodium chlorate mixture,but high air humidity can inhibit its explosion.In a certain temperature range,the continuous increase of ambient temperature will always promote the coal dust/sodium chlorate mixture explosion,and improve the explosive power.In addition,the appropriate amount of gas can improve the severity of coal dust/sodium chlorate mixture explosion,while excessive amount of gas can restrain the mixture explosion.The promoting effects of gas on the P_ex and（dP/dt）_ex of coal dust/sodium chlorate mixture explosion were 56.1%and 200%,respectively.Figure[38]table[10]reference[85]...