Study On The Characteristics And Inherent Regularities Of Coal Spontaneous Combustion Indicator Gases

Coal spontaneous combustion has long been not only restricted the mine safety production work,but also wasted valuable coal resources.Prediction of coal spontaneous combustion plays a guiding role on prevention of coal spontaneous combustion in time.The indicator gases which have been produced in the coal spontaneous combustion process play an important role in the prediction of coal spontaneous combustion.On this basis,a study on the the laws and inherent regularities of the formations of the indicator gases is carried out to explore the mechanism of coal spontaneous combustion which in order to provide theoretical basis for prediction and prevention of coal spontaneous combustion and increase the practical value of indicator gases.This paper selects three kinds of metamorphic coal with different degrees of spontaneous combustion tendency as the research objects which including lignite in Ximeng,long flame coal in Shendong and gas coal in Yima.And usethe both temperature-programmed oxidation and isothermal oxidation experimental approaches to studies the release laws of H₂,CO,CO₂ and C₂H₄ in the coal spontaneous combustion with different coalification degrees,temperatures,particle sizes,qualities and reaction volumes.Grey correlation theory and multiple linear regression model are used to study the relationship among the indicator gases.Which lead us to conclude as following:（1）In coal spontaneous combustion process,the formation quantity of H₂ and hydrocarbon gases such as C₂H₄ which increase exponentially with increasing temperature.Their formation process of them is in close accordance with increasing temperature,and they follow the principle of indicator gas.At the same time,the releasing laws of H₂ and C₂H₄ are very similar to each other respectively,and this similarity can work in coordination with the prediction of the phenomenon of coal spontaneous combustion.（2）According to coal spontaneous combustion process,it is found that coal absorbs O₂ to produce CO and CO₂ gas at 30 ℃.With increasing temperature,CO and CO₂ increase exponentially.In the closed-container isothermal oxidation experiments,the growth of CO in low-temperature with time obeys the logistic growth model,which obeys logarithmic growth at higher temperature.For different coal,the transformation temperature of two different growth model are:100 ℃ of lignite,120℃ of long flame coal and gas coal.In coal spontaneous combustion process,the formation of CO₂ obeys logarithmic growth with time at any temperature.（3）In isothermal oxidation experiment,the ratios of the formation rate of CO₂ and CO are stable at different temperatures.And the ratio is affected by the characteristics of coal and oxygen supply.More insufficient the oxygen is,much higher the ratio is.The result shows that CO is more sensitive to the decrease of oxygen,that is to say,oxygen has obvious promoting effect on the formation of CO.The insensitivity of CO₂ to oxygen indicates that the formation of CO₂ is not only produced by the combination of coal and oxygen,but also resulted from the decomposition of intermediate complex or oxygen-containing functional groups（such as carboxyl groups）.（4）By studying law of indicator gases,it is found that the H₂,CH₄,C₂H₄,C₂H₆ and CO₂ are related to each other closely.Using gray correlation analysis method to gets the classification of the indicator gases,classification of indicator gases depends on the law and correlation of indicator gases:（1）H₂,C₂H₄,CO₂;（2）CO,CO₂;（3）CH₄,C₂H₄,C₂H₆.The repeated indicator gases present that some of indicator gases are generated in different ways,this study indicates that there are several reaction sequences in the process of coal spontaneous combustion process.（5）By using the method of multiple linear regression model,we can get the mathematical relationship between the close-linked indicator gases: the production of C₂H₄ can promote the production of CO₂ under different conditions;the effect of the production of H₂ and the consumption of O₂ to the production of CO₂ can be divided into two types: promoting and inhibiting.