Study On Dynamic Analytic Ventilation System And The Secondary Catastrophes In Coal Mines

Mine disasters have always been a serious problem in China. Recently, the secondary catastrophes happened frequently and caused more serious consequences, but few studies have investigated it and there is still a big gap to totally understand the secondary catastrophes. It is quite important and meaningful to study on the characteristics so as to develop prevention strategies and save people. The dynamic analytical ventilation system and other relative models were firstly developed. Then, a real coal mine ventilation system was used to investigate the impact of sudden gas emission, coal and gas outburst and fires on the secondary catastrophes. Meantime, Simulations were established to investigate the influence of fires on the secondary catastrophe which is gas explosion in tunnels.Lumped-capacity method and convection-diffusion equation were used to establish the gas flow and diffusion model and the gas diffusion process under different conditions has been described. The single element combustion model simultaneously considering volatile and carbon reaction was developed. Based on the discrete method, the model was then used to develop a new fire model of long stick materials such as belt, wood and cable. The dynamic propogation of flame and all parameters including heat releasing rate and gas concentrations can be described. It provided a new way to study the fire phenomenon. Darcy Law and aerodynamics theory were used to describe the gas flow patterns in the"non-broken"region and"broken"region. The coal and gas outburst model was then established and good connections to ventilation network were achieved. When developing air door model of different kind, the relations between valve position and the relative flow area were analyzed and together with flow dynamics equations, they were used to determine the relations between air flow rate and valve position.The dynamic analytical platform was developed by using the model developed in this study and fluid network calculation method. A small scale experimental system was established to validate the platform. The comparison results show that platform has sufficient accuracy with the biggest error of 5% in both static and dynamic simulation. The platform was then used to investigate the influence of sudden gas emission, gas outburst and fire on secondary catastrophes in real coal mine. The results indicate that when sudden gas emission occurs, the secondary catastrophes can only happen in the tailgate and the duration time in which the secondary catastrophes may happen would be the longest when the highest gas concentration is between 10% and 15%. When gas outburst occurs, the air flows reversely in some tunnels. As the initial pressure increasing, the probability of secondary catastrophes is highest in the regions which are indirectly connected with the gas outburst tunnel. The average volume of tunnel with the gas concentration of 5%~16% was introduced, and it was found to be a quadratic function of the initial pressure. When fires occur, secondary combustion and gas explosion probably happen in the downward tunnel. As to the positions sharing the same tunnel with fires, the risk and duration time of secondary catastrophes increase as the distance from the fire increasing. Additionally, fire positions have direct influence on the distribution of tunnel regions with a high possibility of secondary catastrophes.The air flow patterns and gas and temperature distributions were finally simulated in the tunnel during the fire and the factors which may induce to secondary catastrophes were obtained. The results indicate that fire intensity and position have no significant influence on the gas and temperature distribution and are not the critical factors to secondary catastrophes. When ventilation tube destroyed and gas concentration between 5% and 16% appeared, fires of lower intensity had a higher possibility to induce to the secondary catastrophe as gas explosion.