Study On The Evolution Of Oxygen-containing Functional Groups In Coal Pyrolysis And Oxidation

As the main resource of energy and chemical industry in China,the utilization and pollution problems of coal are serious.The efficient and clean conversion and combustion is an important way to control and reduce the waste of resource and environmental pollution in the utilization.Different microstructure of coal results that there is great difference in the mining and utilization of different coal rank,in addition,oxygen functional groups play an important role in coal structure.Therefore the research on the evolution of oxygen-containing functional groups during coal conversion and combustion is of great significance to reveal the mechanism of coal pyrolysis and oxidation.This paper is mainly based on coal functional group structural model and FG-DVC model The microstructure changes and macroscopic product characteristics of coal during thermal reaction were investigated by Fourier transform infrared spectroscopy?FTIR?and thermogravimetry coupled with infrared spectroscopy?TG-FTIR?and the evolution of oxygen-functional groups was revealed.Meanwhile the influence of oxygen-containing functional groups on coal thermal reaction under different conditions was studied,as well as the group reactions.The main contents include as following:Firstly,based on the FTIR characterization method,the distribution of oxygen-containing functional groups in three different coal rank:Shenhua lignite,Binxian bituminous coal and Huangshi lean coal was studied by using the method of peak distribution fitting,and according to the law of Lamber-Beer,the corresponding peak area of the functional groups was used for quantitative analysis.It is found that the occurrence state and content distribution of oxygen-containing functional groups in coal are quite different with the increase of coal rank.By comparing structural parameters of different coal types,it can be found that the coalification process is a process of deoxidation,polycarbonation and de-hydrogenation.Secondly,the horizontal tube furnace was used to simulate the pyrolysis and oxidation of coal,and the FTIR scanning of coal samples with different reaction degrees was carried out to obtain the variation of the content of oxygen-containing functional groups in pyrolysis and oxidation of coal.The result shown the difference in the stability of main oxygen-containing functional groups:C-O>C=O>-OH>COOH.The oxygen-containing functional groups have higher activity,the most of oxygen-containing functional groups almost converse completely in addition to a small amount of hydroxyl groups remaining.In addition,C=O and COOH will appear as transient intermediate products during coal thermal reaction,which is more obvious in the oxidation process.Finally,TG-FTIR was used to study the release of oxygen-containing gas during the pyrolysis and oxidation of coal.And combined with the evolution of oxygen-containing functional groups,the group reactions during coal thermal reaction were deduced.The result shown that The release characteristics of CO₂,H₂O and CO can well explain the evolution of COOH,OH and C=O.Then TG and DSC were used to calculate the characteristic temperature and kinetic parameters of coal thermal reaction.It found that the oxygen functional group mainly affected the low temperature section of coal thermal reaction.Because of the strong activity of oxygen-containing functional groups and the heat released in reaction process,the corresponding characteristic temperature and activation energy of pyrolysis oxidation of low-rank coal are both lower than that of high-rank coal.