Pyrolysis Kinetics And Synchrotron Radiation Mass Spectrometry Analysis Of Medium-and Low-Rank Coals

Coal plays an important role in energy consumption of China.Due to the complexity and heterogeneity of coal,the understanding of coal structure is not sufficient,which limits the clean and efficient utilization of coal.Coal pyrolysis is the first step for the thermal utilization of coal.Coal pyrolysis is an effective method to study the characteristics of coal structure.In this thesis,Cheji?CJ?,Ekuang?EK?and Dongshengli?DSL?coals were selected as the sample to study the pyrolysis process under different experimental conditions.Fourier transform infrared spectroscopy?FTIR?,gas chromatography-mass spectrometry?GC/MS?,high-resolution electrostatic field orbitrap mass spectrometry?Orbitrap-MS?and on-line gas detection technology were used to analyze the products of coal pyrolysis,and the characteristics of product distribution under different pyrolysis conditions were obtained.In addition,the kinetics of coal pyrolysis and gas escape were analyzed.Finally,the on-line analyses of coal pyrolysis products were realized by pyrolysis gas chromatography mass spectrometry?Py-GC/MS?and synchrotron radiation photoionization time of flight mass spectrometry?SVUV-PI-TOFMS?.The experimental results showed that the pyrolysis yield increased with the heating temperature and heating rate,in which the pyrolysis yield of EK-600-10 was 25.2%,while that of EK-1000-20 was 34.2%.With the increase of temperature,the hydrocarbon structure of oxygen-containing functional groups and aliphatic hydrocarbons in coal gradually disappeared,while that of aromatic hydrocarbons gradually increased.Aromatic structure of macromolecules in coal is easier to decompose to form small aromatic free radical fragments at a high temperature.In the mean time,oxygen-containing functional groups are easily removed to generate aromatic free radicals or aliphatic free radicals,which are further condensed to generate aromatic hydrocarbons at a high temperature.The results of on-line gas analysis show that the degree of coalification has a great influence on the distribution and yield of coal pyrolysis gas.Compared with the other two kinds of coal,the amount of CO and CO₂in DSL is 194 and 146 mL,respectively.The amount of CH₄ in EK is 647 mL and the amount of H₂ in CJ is 1078 mL.The results of pyrolysis kinetics show that the average activation energy value of EK is 1230.1 kJ/mol,which is much higher than those of CJ and DSL?752.8 and 45.5kJ/mol,respectively?.The higher the content of organic matter is,the more favorable the formation of gas is.Therefore,the activation energy of pyrolysis of four kinds of gas is the lowest for DSL coal.The activation energy curve of CH₄ in EK proves that EK is rich in fatty hydrocarbons.the trend of activation energy of H₂ in CJ indicates that the polycondensation reaction in coal needs a higher energy.The results of Py-GC/MS showed that the molecular fragments of EK and DSL were mainly benzene,naphthalene and anthracene,and their corresponding alkyl derivatives,and benzopyrene and benzoperylene were the molecular fragments in CJ.The results show that the aromatic carbon bridge bond in coal began to break around450 ^oC.SVUV-PI-TOFMS obtained a large number of compounds information that Py-GC/MS could not detect.Such fragments were mainly generated by the removal of side chains from the macromolecular structure.The types and molecular weight distribution of pyrolysis products change obviously with the increase of temperature.The release time of products for EK is longer than that for CJ and DSL,because the mineral components in EK hinder the release of products and heat transfer during pyrolysis.The paper has 42 figures,9 tables,6 attached figures,2 attached tables and 92references.