Research On Thermodynamic Characteristics And Heat Transfer Method Of Uncontrolled Fire In Coal Gangue Dump

Spontaneous combustion on coal refuse piles is a kind of unusual combustion system,with the characteristics of easy spontaneous combustion,self-heat storage,and easy to revive the combustion.Open piled up coal and coal refuse often causes the coal fires,which is a way of waste resources and pollution of the environment.In additional,it may also lead to serious accidents and huge economic losses.Conventional governance means mainly from the"isolated oxygen" point of view to control the spontaneous combustion on coal refuse piles.As the internal accumulation of heat could not be dispersed in time,with the passage of time will cause the re-ignition mostly.Based on the "cooling" of the technical ideas,the theory of spontaneous heat transfer and the method of spontaneous combustion control with heat pipe are put forward for the spontaneous combustion of coal refuse piles.The thermodynamics process and ignition condition of coal gangue spontaneous combustion are analyzed theoretically to study the interrelationship between internal and external factors such as moisture permeability and spontaneous combustion characteristics of coal refuse piles.Compared with the associated coal,the contents of N,C,H,fixed carbon and specific heat contained in the Gongwusu coal gangue are lower than those of the associated coal,but the moisture content,ash content,sulfur content,thermal diffusivity and thermal conductivity are higher than those of associated coal.At the same temperature gradient,the internal temperature of coal refuse piles propagates more rapidly,and the temperature diffusion ability is bigger than the associated coal conduction energy.Heating on the same amount of the heat,coal refuse piles is heating faster and more easy to spontaneous combustion.The comprehensive burning index S_n of coal refuse is positively correlated with(V_ad + FC_ad)/A_ad,the fitting coefficient R² = 0.9759.The higher the content of volatile and fixed carbon in coal refuse piles get the lower the ash content and the better the comprehensive combustion performance.The integrated combustion index S_n,the ignition index Di and the burnout index Dh are positively correlated with FC_ad/V_ad.The linear correlation coefficients were R² = 0.8429,0.9258,and 0.9972 respectively.In the case of sufficient oxygen combustion,the greater the fuel ratio,the better the performance of coal refuse piles burned.Oxygen consumption rate,concentration and production rate of CO,the third fire coefficient R³ can be used as a main indicator of spontaneous combustion of coal refuse piles,and the concentration and production rate of CO₂ and CH₄,the first fire coefficient R1 and the second fire coefficient R² can be used as an auxiliary index.On obtaining then weight loss rate and characteristic temperature parameters,the process of weight loss of coal refuse piles is divided into desorption,oxidant cracking,combustion and thermal activation and phase transition four stages.Achar differential method and Coats-Redfern integral method were used to calculate the kinetic parameters and mechanical function of non-controlled combustion of coal refuse piles.Experimental study shows that the heat pipes affect the thermal field behavior of the internal temperature field.During the trial period,the maximum cooling rate of the single heat pipe is 33.4? and the cooling rate is 39.6%,and the "saddle" temperature field distribution occurs in the coal pile under the action of double root.The mathematical relationship between the cooling radius of the heat pipe within the coal pile is deduced,and the calculation on the heat dissipation of 80 h hot bars were 1.0865,2.1680,and 3.3649 MJ,respectively,and the influence of heat pipe on the internal temperature field of coal pile was verified by ANSYS software.The research shows the cooling effect of the heat pipe on the coal pile is negatively correlated with the distance and is positively related to the internal heat source power.With the passage of time,heat pipe on the coal storage capacity of the cooling capacity will continue on increasing.In addition,the installation technology of the heat pipe is established in this study,and the remote wireless safety monitoring system is established.The characteristics of the axial temperature,the level of coal refuse piles,the vertical temperature distribution and the daily temperature change were studied.Based on the heat pipe in the coal pile heat turnover process,the quantitative criteria such as the cooling rate was evaluated and calculated.This study can provide guidance for the popularization and application of heat pipe technology in the later stage of spontaneous combustion on coal refuse piles and fire prevention.