Study On The Formation Rule Of Higher-molecular-weight Gaseous Products During The Oxidation Of Coal And Prediction Of Coal Spontaneous Combustion

There is a risk of spontaneous combustion in most coal mines in China.Spontaneous combustion of coal will lead to coal mine fire accidents,affect the safety of coal production,burn down equipment and threaten the life safety of underground workers.Therefore,it is very important to predict the spontaneous combustion.Index gas analysis is an important method for the prediction of coal spontaneous combustion.Lower-molecular-weight gaseous products such as CO,C₂H₄ and C₂H₂ are widely used at home and aboard as index gases for the prediction of coal spontaneous combustion.However,the whole process of coal spontaneous combustion cannot be covered by these index gases,which means there is a blank area in the prediction of coal spontaneous combustion.In this study,it was found that in the process of spontaneous combustion of coal,hydrocarbon gases(including alkanes,olefins and their isomers)with higher-molecular-weight such as C₄-C₆,aromatic hydrocarbons,aldehydes,ketones and benzene would also be produced.These gaseous products of coal spontaneous combustion with relatively large molecular weight will fill the blank area of coal spontaneous combustion prediction and predict coal spontaneous combustion better.This article selects the Qing Dong(QD),Zhun Dong(ZD),Da Lin(DL)three coal samples which have different metamorphic grade as experimental coal samples,higher-molecular-weight gaseous products generated in the oxidation process of experimental coal samples were qualitatively and quantitatively analyzed by Gas Chromatograpgy-Mass Spectrometry(GC-MS),and prediction of coal spontaneous combustion was studied.The following research results were obtained:Firstly,the chromatographic and mass spectrometry condictions for the analysis of higher-molecular-weight gaseous products from coal oxidation by GC-MS were studied and determined.The types of capillary chromatographic columns were optimized,and the heating mode of the column,the solvent delay time,the scanning mass range and the total running time of single injection analysis were determined.Through qualitative analysis,it is found that there are 21 kinds of higher-molecular-weight gaseous products generated by the oxidation of QD coal sample,including 18 kinds of hydrocarbon compounds,mainly C₄-C₆higher-molecular-weight hydrocarbon compounds.In addition,2 kinds of aldehyde compounds and 1 kind of ketone compound which are less reported in literature are also detected.There are 11 kinds of higher-molecular-weight gaseous products generated by the oxidation of ZD coal sample,including 9 kinds of hydrocarbon compounds of C₃-C₅,1 kind of aldehyde compound and 1 kind of ketone compound.There are 3 kinds of higher-molecular-weight gaseous products generated by the oxidation of DL coal sample,including 1 kind of hydrocarbon compound of C₃,1kind of aldehyde compound and 1 kind of ketone compound.Through quantitative analysis and study of the formation rule of higher-molecular-weight gaseous products,it is found in the higher-molecular-weight gaseous products generated by oxidation of QD coal sample,the concentration of gaseous products except acetone gradually increased with the rise of coal temperature,showing a near exponential function growth.In the higher-molecular-weight gaseous products generated by oxidation of ZD coal sample,the concentration of most products increased with the temperature rise to rise after the fall of the coal,but the concentration of some products first decreased amd then increased with the rise of coal temperature,the concentraton of acetaldehyde first increased and then decreased with the rise of coal temperature,the concentration of acetone on the whole increases with the rise of coal temperature,and 2-methylpropylene increases exponentially with the rise of coal temperature.Among the higher-molecular-weight gaseous products generated from DL coal sample,the concentration of acetaldehyde first increased,then rapidly decreased,then slowly increased and finally slowly decreased with the rise of coal temperature,and the concentration of acetone first slowly increased and then slowly decreased with the rise of coal temperature.The prediction of coal spontaneous combustion by higher-molecular-weight gaseous products was studied.The results showed that higher-molecular-weight gaseous products could be used as prediction indexes in addition to lower-molecular-weight index gases to predict coal spontaneous combustion.The detection of higher-molecular-weight gaseous products fills up the blank temperature area existed in the prediction of coal spontaneous combustion with lower-molecular-weight index gases and realizes the prediction of the whole temperature section of coal spontaneous combustion.The results show that the higher-molecular-weight gaseous products of coal oxidation can be used as prediction indexes of coal spontaneous combustion,and be used to predict the coal spontaneous combustion.There are 45 figures,23 tables and 90 references in this paper.