Research On Factors Affecting Characteristics Of Coal Low Temperature Oxidation

Nowadays,coal is still one of the main energy sources in China,and its position can not be replaced.Due to the special nature of coal mine,oxidation and even spontaneous combustion will occur,which will not only cause economic losses,casualties,but also waste resources and damage the environment,and these consequences are immeasurable,so it is necessary to reduce the number of coal oxidation and spontaneous combustion accidents.This article mainly explores the factors that affect the low temperature oxidation of coal,and the main results are as follows:（1）The temperature programmed experiments of coal samples（Hami lignite,Xinji gas coal,Zhongliangshan anthracite,Zhaoxian long flame coal and Donglin lean coal）between 60℃and 200℃show that the CO release rate of lignite increases from0.226×10^-6/min to 22.715×10^-6/min,the release rate increases by 100 times,that is,with the increase of temperature,the low-temperature oxidation rate of coal increases gradually;When the degree of coal metamorphism increases,the drying temperature and critical temperature of coal have a certain lag,the gas release rate in the process of low-temperature oxidation of coal gradually decreases,CO/CO₂ shows a decreasing trend with the increase of coal metamorphism,which can be used as an auxiliary index gas in the process of low-temperature oxidation of coal.When the heating rate of coal is higher,it is easier to oxidize,and it will enter the stage of violent reaction earlier;When the oxidation time is 15 min,the coal oxygen complex reaction is the most violent,and the co production is up to 273.65×10^-6;When the oxidation time is prolonged at a fixed temperature,the coal sample will fully contact with oxygen,and the reaction between coal and oxygen will be more sufficient;With the increase of oxidation time,the amount of gas increased first and then decreased,but it still increased as a whole.（2）The distribution of C-H groups and oxygen-containing functional groups in coal samples with different metamorphic degrees was studied by infrared spectroscopy.It was found that with the decrease of volatile matter,the C-H groups in coal decreased.The content of active functional groups in coal with similar volatile matter was similar,which was corresponding to the results of temperature programmed experiment;With the increase of metamorphic degree,the C=C structure and oxygen-containing functional group structure of coal decrease gradually;The IR spectra of lignite after oxidation at different temperatures show that the main groups involved in the reaction are C-H,C=C,C=O and so on.With the increase of temperature,the content of C=C gradually decreases,and the content of C-H first decreases and then increases,but the overall trend is still decreasing;The content of carboxylate–COO and carboxyl COOH increased gradually.（3）The weight loss and activation energy of lignite with different particle size were studied by synchronous thermal analyzer.The results show that with the decrease of particle size,the ignition temperature and maximum weight loss rate temperature of lignite decrease,and the oxidation reaction of lignite is easier;DSC results show that with the decrease of particle size,the endothermic stage of coal will advance to a certain extent,and the exothermic stage shifts to low temperature as a whole;In the low temperature stage,the apparent activation energy of coal decreases with the decrease of coal particle size.The apparent activation energy of coal samples with particle size in the range of 0.425 mm-0.180 mm is 11.97 kJ/mol higher than that of coal samples with particle size less than 0.0750 mm,which can explain the effect of particle size on coal oxidation process.