Determination And Prediction Of The State Of Coal Spontaneous Combustion Based On Multi-Objective Grey Target Decision

Spontaneous combustion of coal left in the goaf is one of the main disasters faced by coal mines for a long time,especially in the mines where gas and spontaneous combustion disasters coexist,spontaneous combustion of coal left in the goaf can induce secondary disasters such as gas explosion,which seriously threatens the safe production and personnel safety of mines.Therefore,it is important to grasp the oxidation state of coal spontaneous combustion in the goaf to prevent and control the occurrence of coal spontaneous combustion disasters.The current coal spontaneous combustion oxidation state determination model tends to ignore the influence of gas in the goaf on coal spontaneous combustion,which leads to problems such as poor data slip resolution of the model determination index and weakens the application effect of the determination model.In order to improve and solve the above problems,this thesis takes the influence of gas on coal spontaneous combustion characteristics as the entry point,adopts the research method combining experimental research,theoretical analysis and mathematical modeling,analyzes the characteristic point temperature during coal spontaneous combustion and oxidation process,and divides coal spontaneous combustion and oxidation stages.It also constructs a model for determining and predicting coal spontaneous combustion and oxidation status in the goaf,which provides a reference basis for early warning and prevention of coal spontaneous combustion disasters in the goaf of high gas coal seams.The effect of gas on the characteristics of coal spontaneous combustion oxidation was carried out using a coal spontaneous combustion program heating system and electron spin resonance spectroscopy.The results show that the crossover point temperature and the first appearance temperature of signature gas products（CO and C₂H₄）of coal spontaneous combustion oxidation under different gas volume fraction atmospheres are positively correlated with the gas volume fraction,and the generation of signature gas products at the same temperature decreases with the increase of gas volume fraction,and the macroscopic characteristics of spontaneous combustion oxidation show an obvious hysteresis phenomenon.In the process of spontaneous combustion oxidation,the gas volume fraction in the oxidation atmosphere In the process of auto-ignition oxidation,the increase of gas volume fraction in the oxidizing atmosphere decreases the free radical concentration and g-factor value in coal at the same temperature,and the g-factor turning point temperature is obviously shifted to high temperature.The above evolution patterns of gas on the macro and micro properties of coal spontaneous combustion and oxidation indicate that gas has a significant inhibitory effect on coal spontaneous combustion and oxidation,which slows down the process of coal-oxygen complex reaction.The evolution of weight ratio and weight loss rate during the process of coal spontaneous combustion oxidation was studied based on thermogravimetric analysis,and the stages of coal spontaneous combustion oxidation were divided by combining the characteristics of macroscopic changes of gas production and oxygen consumption characteristics.The results show that the oxygen consumption rate,CO and CO₂ show an exponential-like rising trend with the increase of temperature,and the temperatures of the first appearance of hydrocarbon gas products are different,and the temperature of the first appearance of C₂H₄ is significantly higher than that of C₂H₆,and the C₂H₄gas is detected for the first time at about 110℃.Meanwhile,it is found that the composite indexes of CO/CO₂,CO₂/O₂ and CO/ΔO₂ also have a high correlation with the oxidation temperature The characteristic temperature points in the process of coal spontaneous combustion oxidation were determined by combining the macroscopic gas production and oxygen consumption characteristics with the microscopic radical stage change characteristics,and the coal spontaneous combustion oxidation state was divided into six stages:latent stage,thermal storage oxidation stage,critical stage,pyrolytic fission stage,acceleration stage and combustion stage.Based on the characteristics of oxygen consumption and gas production in coal spontaneous combustion and oxidation,a comprehensive evaluation index system with single index CO,composite index CO/CO₂,CO₂/O₂ and CO/ΔO₂ was selected.A model for determining the spontaneous combustion and oxidation status of coal in the goaf was constructed based on gray correlation analysis and multi-objective bull’s-eye distance decision theory,and a bull’s-eye distance correction method was proposed for the mining area of high-gas coal seam to correct the errors in the model calculation results due to the different volume fractions of gas in the oxidation atmosphere and improve the accuracy of the determination results of coal spontaneous combustion and oxidation status.Based on the monitoring data of the fire monitoring system,the bull’s-eye distance sequence data is calculated by applying the coal spontaneous combustion oxidation state determination model,and the HP filtering method is introduced to decompose the bull’s-eye distance sequence data and extract the trend element data to obtain the bull’s-eye distance change trend.The actual measurement data and prediction results in the field verify the prediction accuracy and practicality of the HP-ARIAM model,and the visualization platform based on QT application design platform is developed and designed to clearly show the prediction and determination results of the model,which provides an intuitive,scientific and reliable basis for the prevention and control of coal spontaneous combustion in the goaf.There are 40 pictures,16 tables and 101 references in this thesis.