Study On Measurement Of The Shortest Coal Spontaneous Combustion Period And Spontaneous Combustion Control Technology Of Coal Stockpile

Spontaneous combustion exists in the process of production and transportation commonly. It is a great hidden danger in coal industry. In order to control coal spontaneous combustion effectively, it is necessary to study the characteristics, forecast the shortest period and develop appropriate control technology of coal spontaneous combustion.Accurately measuring basic parameters of coal spontaneous combustion is the precondition to study the regulation of coal spontaneous combustion. According to the theories of heat transfer, mass transfer and seepage mechanics, a set of method and test system of main parameters measurement in the process of coal oxidation at low temperature was developed. The parameters include coal oxidative heat release intensity, heat conductivity, oxygen diffusion coefficient, and filtration coefficient. Moreover, we established the experimental system to measure heat release intensity of coal spontaneous combustion. The system can measure fastly and accurately. Using the measured parameters, the effect of size, temperature and metamorphic grade of coal on those parameters is analyzed. Moreover, the effect functions are also established and it is the base of studying the characteristics of coal spontaneous combustion at different conditions.Based on accurately measured basic parameters of coal spontaneous combustion, a 2D mathematical model of adiabatic coal column to calculate the shortest experimental spontaneous combustion period of coal is developed. Through analyzing the orthogonality relationship of spontaneous combustion period and effect factors, the shortest experimental spontaneous combustion period of coal can be accurately measured. The result is fit for the real performance and the accuracy of the result can be indicadited. The method cosumes less time and is capable of measuring mass coal samples.A 2D numerical model of auto thermal of coal stockpile is developed. The model is calculated by FLUENT to study the regulation of auto thermal of coal stockpile. The data of numerical simulation is measured by experiments. The result shows that air flows into the stockpile from the bottom and out of from the top. Moreover, the distribution of high temperature dot also can be found out. Based on the simulation result, a new appropriate spontaneous combustion control method of coal stockpile, paving fine coal on the surface of the bottom part of stockpile, is developed.In order to study the effect of above method, we make a numerical simulation of coal stockpile covered with fine coal. The numerical simulation analyzes the gas seepage and oxygen distributive regulation inside the coal stockpile covered with fine coal. Compared with coal stockpile without fine coal, the effect of the method can be analyzed comprehensively. At the same time, a coal stockpile temperature rising experimental table is developed. Experimental study of 2D heat and mass transfer regulation of horizontal air diffusion and vertical heat convection of coal stockpile covered with different fine coal in thickness. The experimental and numerical analysis result shows that fine coal covered can prevent oxygen supply to the coal stockpile, so spontaneous combustion can be controlled.Finally, using the control method of covering fine coal on coal stockpile in the field test, the spontaneous combustion of Shenhua coal is controlled. The coal stockpile without fine coal covered can ignite in 18 days. However, the temperature of coal stockpile can only reach 59.9℃during 123 days if it covered with 1 m fine coal. In addition, analyzing the effect of environmental temperature, air flow and sunshine irradiation, the moving regulation of high temperature section of coal stockpile can be found by the field test.79figs., 23tabs., 137refs.