Oxidation kinetics regularity in spontaneous combustion of gas coal

Availableonlineatwww.sciencedirectcomMINING多到ScienceDirectSCIENCE ANDTECHNOLOGYELSEVIERining Science and Technology 20(2010)0059-0063Oxidation kinetics regularity in spontaneouscombustion of gas coalWANG Lanyun", JIANG Shuguang", WU Zhengyan, SHAO Hao4.2ZHANG Weiging", CHEN Yueqin ZoU Lili.2State Key Laboratory of Coal Resources and Mine Safety, China University of mining TechnologyXuzhou 221008, ChinaSchool of Safety Engineering, China University of Mining Technology, Xuzhou 221008, ChinaAbstract: In order to investigate the oxidation kinetics of gas coal at low temperatures, we derived a rate equation of oxygen con-sumption during low-temperature oxidation of gas coal and deduced an E-c equation, expressing the relation between active energyE and oxygen concentration c. The reaction order n and active energy e were calculated with this equation based on experiments ofstatic oxygen consumption tests. In addition, we proved the rationality of the e-c equation using a kinetic compensation effect andobtained the isokinetic temperature T The results show that: 1)the gas coal oxidizes easily with increasing temperature and theoxidation tends to be spontaneous at higher temperatures: 2)the oxygen concentration c affects oxygen consumption very much atlower temperatures but has only a small effect at higher temperatures; 3)the isokinetic temperature T was 127C which has beenexperimentally validated as the key tuning point during low-temperature spontaneous combustion of gas coalKeywords: static oxygen consumption test system; reaction order; active energy; kinetic compensation effect; isokinetic tempera1 Introductionpyrolysis at a high temperature stage. Additionally,TGA is usually affected by flotage, convection, conLow-temperature oxidation of coal is accompanied densation of volatiles, tested errors of temperaturey oxygen consumption and emission of gaseous and other factors. In the TG experiment, the weight inproducts which suggest that spontaneous coal com- coal loss may be affected by vaporizing water whichbustion is approximately divided into several stages. exacerbates the test errors. Adiabatic oxidation exPrevious work by professor Xu Jingcai et al. on coal periments, providing an insulated reaction surroundoxidation has indicated that oxygen consumption is ing for coal oxidation to investigate the oxidizationan important macroscoproperty reflecting the self-potential of coal, provides data for building aoxidation ability of coal -7. Moreover, this consump- numerical relation between reaction temperature andtion characteristic can also reveal the rules of chemi- heating rate. The active energy E is educed froncal kinetics in low-temperature oxidation of coal, but curves of rising temperature. This method is usuallyit has been never investigatedapplied to predict the susceptibility of spontaneousThermogravimetric Analysis (TGA)and adiabatic coal combustion. In addition, some researchers oboxidation have been used to obtain the chemical ac- tained the average reaction order n in the oxidation oftive energy e of coal oxidation. As well. many other coal on the basis of isothermal experiments and conuseful attributes have been explored with these two cluded results which show that the reaction order nand reaction velocity v are related to temperature T.ItHowever, TGA is usually used to investigate the should be noted that n is seldom equal to 1. The valuepyrolysis kinetics of coal and to analyze different of n increases and the consumption rate v decreasesoxidation mechanisms 57. It is more applicable for with decreasing temperature中国煤化工 oxygen concenReceived 05 March 2009: ag June 2009penneg author. tel:8615952181013trationCNMHGng emperaturesE-mailaddresslanyun,wang@gmail.comters. We applieddoi:10.10l6S16745264(09)60161-7the soct experiment results to analyze the oxidationMining Science and TechnologyVol 20 No. 1kinetics of gas coal. This is the first time that kineticEregularity of spontaneous coal combustion in lowHence-E/ dT=2!3!4!x+x-元mperature stages has been demonstrated on the ba-is of oxygen consumption performancePrevious studies have shown that RT<