Study On Oxidation Exothermic Characteristics And Reaction Mechanism Of High Organic Sulfur Coking Coal

Coking coal has the dual attributes of fuel and raw material,and is a scarce,non-renewable and irreplaceable strategic resource in the short term.Shanxi Province is the country’s largest production base of coking coal.The deep coal seams have high sulfur content,especially high organic sulfur content.Sulfur content is an important internal factor affecting the spontaneous combustion of coal.As the depth of coal mining extends downward,high-sulfur coking coal faces a huge challenge from spontaneous combustion hazards.Spontaneous combustion of coking coal has the three major hazards of coal mine safety,environmental pollution,and loss of scarce coal resources.Therefore,based on the basic idea of structure-reaction-mechanism,combined with the results of oxidation reaction experiment and reaction molecular dynamics simulation,this dissertation jointly reveals the influence mechanism of organic sulfur structure on the spontaneous combustion of coking coal.Using chemical titration and X-ray photoelectron spectroscopy(XPS)technology,the occurrence laws,combined states and structural characteristics of organic sulfur in 22 coking coals with different initial sulfur content and different degrees of metamorphism in Shanxi were studied to analyze the different sulfur content.The oxidation reaction characteristics of coal and the selection of suitable organic sulfur model compounds lay the foundation for the structure of sulfur in coal.Simultaneous thermal analysis combined with mass spectrometry(TG-MS)experiments were used to explain the heat release characteristics of medium and high sulfur coking coals and the evolution of gas phase products.It was found that the degree of deterioration is the same,the content of organic sulfur is high,and the tendency to spontaneous combustion is high;organic sulfur forms And the content affects the initial,inflection point and peak temperature of the gas phase product escape;the highly active sulfur-containing functional group increases the oxidation reaction activity of the coal,and promotes the heat accumulation in the initial stage of coal spontaneous combustion.Using programmed temperature experiment combined with automatic sulfur meter,FTIR and XPS detection technology,the surface morphology,sulfur content,surface functional groups and C of the solid phase product of Shuiyu fat coal(SY)in oxygen/thermal environment under gradient temperature were analyzed.The evolution law of the combined states of,O,N,and S elements shows that as the degree of oxidation deepens,coal weight loss and sulfur loss are linearly positively correlated.Mercaptans/ether sulfur is converted into sulfoxides and sulfones.Sulfate is the final result of organic sulfur oxidation.product.A series of "coal-like substances" with specific organic sulfur structure was prepared by the ultrasonic+impregnation method.The influence of different organic sulfur types and contents on the oxidation heat release of "coal-like substances" was found by using TG-MS."The characteristics of thermal weight loss and the law of gas evolution are mainly affected by the type of organic sulfur and the chemical environment.Oxidation activity:dimethyl sulfoxide>phenyl sulfide>dimethyl sulfone>thiophene>diphenyl sulfoxide>diphenyl And thiophene.The self-developed synchronous temperature compensation adiabatic oxidation experimental system is used to study the oxidation heating rate of "coal-like substances",the heating rate(T70℃):dimethyl sulfoxide>phenyl sulfide>dibenzothiophene.In the lowtemperature oxidation stage,the active sulfur-containing small molecules promote the oxidation temperature rise,and the stable structure and larger molecular weight dibenzothiophene slows down the oxidation temperature rise rate of "coal-like substances".The macromolecular structure model of SY high organic sulfur coking coal was constructed,and the whole process of oxidation-combustion of SY coal was simulated by ReaxFF MD.The change law of main intermediates and products was analyzed,and the main sulfur-containing products were deduced.The generation method and the comprehensive experimental results divide the spontaneous combustion process of coal into three main stages of evolution.This dissertation reveals the reaction characteristics of organic sulfur in coal in the oxidation process and the evolution of sulfur,and clarifies the mechanism of organic sulfur structure affecting coal spontaneous combustion,which is of great significance for protecting scarce coking coal resources and preventing spontaneous combustion in high organic sulfur coal seams.The dissertation has 78 figures,31 tables,and 205 references.