Research On Spontaneous Combustion Characteristics And Temperature Field Distribution Law Of Gangue Pile

For a long time,the spontaneous combustion has seriously polluted the ecological environment of mining and surrounding areas,threatened the health of residents.The grouting fire extinguishing method has good effect and economic benefits,which is the most widely used method of gangue hill treatment.In order to improve the"blind grouting"problem and fire extinguishing,and to improve the control effect of spontaneous combustion,it is necessary to carry out research on the spontaneous combustion characteristics and temperature field distribution.Based on the spontaneous combustion mechanism,the combustion characteristics and the distribution of temperature fields in high temperature areas are explored by means of detection technology,experimental analysis,and temperature field distribution simulation,to guide the on-site fire extinguishing slurry ratio,determination of grouting amount,and drilling location layout work.Combining the conclusions thermogravimetric test and the programmed temperature test,the law of temperature and gas release during the oxidation and heating process of the gangue reveals the combustion stage and characteristics,as well as the changes in the spontaneous combustion characteristics under the action of different influencing factors.Numerical simulation of the temperature field distribution law of the spontaneous combustion process of the waste rock.Using the research results of the spontaneous combustion characteristics of gangue and the distribution of temperature field,the grouting fire-fighting plan is formulated in a targeted manner to improve the spontaneous combustion control effect and provide a theoretical basis for engineering practice.The main research results are as follows:（1）Detecting the physical and chemical properties of samples shows that gangue is a combustible mineral with low ash content,high volatile content,high sulfur content,and low deterioration.Combining the results of the adiabatic oxidation test and the temperature programmed test,five characteristic temperature points that indicate changes in the combustion characteristics of coal gangue are determined:critical temperature T1（59.16℃）,dry cracking temperature T₂（275.42℃）,ignition point temperature T₃（469.42℃）,and maximum temperature.Fast weight loss oxidation temperature T₄（551.64℃）and burnout temperature T₅（735.96℃）.The coal gangue combustion process is divided into 4 stages:gas-water desorption stage（room temperature～T₂）,slow combustion stage（T₂～T₃）,full combustion stage（T₃～T₅）and end combustion stage（T₅～1 000℃）.Establish six corresponding relationships between O₂,CO,CO₂,CH₄and C₂H₆,CO₂/CO,CH₄/C₂H₆ gas indicators and temperature,analyze the changing laws and reasons of gas indicators,and determine the spontaneous combustion characteristics of each stage of gangue combustion.（2）Change the parameters of the particle size,water content and sulfur content of the gangue,establish 15 corresponding relations between the gas index and temperature in the gangue hill combustion process,and obtain the gas product release characteristics of the gangue under the conditions of the above three factors.The law of change,perfect the spontaneous combustion characteristics of the waste rock,The smaller the particle size of the gangue,the stronger the oxidative spontaneous combustion characteristics.If the particle size is too small,the oxidation characteristics will be weakened;a small amount of water promotes the spontaneous combustion of the gangue,and too much moisture inhibits the early combustion of the gangue and promotes the later combustion;the greater the sulfur content of the gangue,the spontaneous combustion of the gangue The stronger the characteristics,the more suitable sulfur content can inhibit the burning of gangue hills.（3）Using ANSYS Fluent to simulate the internal temperature field distribution of the gangue hill,the results showed that the ignition point was 9-11m below the slope,the ignition point temperature reached 438.7℃when the hill was accumulated for 210 days,causing the spontaneous combustion.The surface of the gangue hill is the top from the top of the slope within 15m and the slope within 25m from the top of the slope are high temperature areas.The borehole layout plan is designed for the temperature field model of the gangue hill.4rows of grouting holes are set on the top of the gangue hill.The number of holes in rows 1to 4 is 11,11,7 and 6,respectively.The hole spacing is 3m,and the depth is 10m.Using fly ash as the main material of the fire extinguishing slurry,the average grouting volume per hole is 40m³,and each slurry contains 317kg of fly ash,17kg of cement,17kg of admixtures and 833kg of water,based on the spontaneous combustion in each temperature zone.Characteristics,adjust the slurry ratio,can achieve a good governance effect.