Developing Regularity And Control Techniques Of Opencast Goaf Fire District

Open pit mine fire belong to underground coal fire, which formed mainly by the spontaneous combustion of underground coal. Because of the small coal mines opening indiscriminate, leading to underground seams and rock loose and fractured and causing mine goaf air leak cause seriously, which provide conditions for physical and chemical reaction of coal and oxygen, and trigger a large goaf fire area. Goaf fire area will lead to working face subsidence and seriously threat the security of workers and large operating equipment, and physical and chemical reaction of coal and oxygen will produces high-temperature, poisonous and harmful gases, which will influence the mental and physical health of workers and cause environmental pollution when they escaping the working flat plate. Therefore, we must govern the goaf fire area promptly. The article uses the method of theoretical simulation and site practices to research combustion regularity and control technology of goaf.Underground coal fire is a multi-field dynamic coupling process: spontaneous combustion, due to the change between oxygen consumption and oxygen supply, the concentration of oxygen which participate in coal and oxygen chemical reaction is changing, and the variety and quality of combustion gas product are changing; combustion produces high temperature environment make the surrounding pressure and gaseous products transfer power changes, which lead to the gas transmission rate and oxygen concentration change; the change of gaseous products transfer rate causes the heat exchange rate change between gas and coal or rock, which influences the temperature transfer rate of fire area. The article takes the coupling parameters of pressure, temperature and air leakage strength to deduce kinetics energy conservation, mass conservation and momentum conservation equations of coal oxidation.The article uses the Comsol Multiphysics multi-physics simulation software to simulate and analyze the development law of goaf fire area, and research the goaf fire area transfer law at different pressure, permeability and geological conditions, and research the temperature, pressure, oxygen concentration and so on distribution in fire transfer process. It has highly flexible, powerful solvers and high accuracy, and the results of numerical simulation analysis close to reality. studies have shown that: coal fire transmit to the horizontal and vertical at the same time, and transmission speed transit to the surface direction is faster than to beneath the fire source; coal fire along the air leakage direction irregularly development, and the greater the intensity air leakage, the faster coal fire transfer rate; coal fire pass large cracks or geological formations occurs at large gradient, the greater the porosity, the faster coal fire transfer rate. Through researching the development law of goaf fire area, the article uses fire area rapid filling method, fire extinguishing method of isolation the area and fire area layered decreasing temperature method to govern goaf fire area, which can prevent the spread of fire and fire area resurgence.