Study On Mechanism Of Antioxidant Foamed Gel For Preventing Spontaneous Combustion Of Coal In Gob

The spontaneous combustion of residual coal in the gob seriously threatens the safety and efficiency of coal mining,employees' occupational health and regional environmental ecology.Injecting anti-spontaneous combustion material into gob is an important technical means to prevent residual coal from spontaneous combustion.In order to improve the performance of the anti-spontaneous combustion materials for the gob,based on the theories and methods of coal spontaneous combustion,hydromechanics,thermodynamics and quantum chemistry,this thesis developed anti-oxidant foamed gel(AFG),and carried out the preparation of composite materials,macroscopic properties testing,microstructure characterization and chemical resistance mechanism research.In this thesis,the preparation of AFG was studied by the methods of intercalation grafting,single factor experiment and response surface methodology.Based on the modification and synergistic effect of key chemical retarding components by intercalation grafting method,single factor experiment and response surface methodology were used to further study the optimum proportioning of gelling agent,crosslinking agent,foaming agent,stabilizing agent and inhibitor,and the AFG was prepared.The preparation method of the composite and the optimal ratio of each component under multi factor and multi-level conditions were obtained.Based on the thermogravimetric experiments of AFG and typical inhibitor,the characteristics for preventing coal from self-ignition of AFG were compared and analyzed,and its effect for preventing coal from self-ignition was verified in laboratory under laboratory conditions.According to the systematic idea of "preparation-performance-structure" of new materials,the properties and structures of AFG were characterized by a series of laboratory tests.AFG's macroscopic properties for preventing coal spontaneous combustion,such as fluidity,space retention,oxygen supply cut-off,water retention and thermal stability were characterized by using the parameters of shear stress-shear rate,flow resistance,water loss rate-temperature and so on.By SEM,XRD,XPS,platinum ring method and the simulation model of glass method,morphology characteristics,the crystal structure of solid particles,surface adsorption,surface tension and microscopic seepage features were characterized.The connection of its macroscopic performance for preventing spontaneous combustion and its microscopic characteristics was analyzed,and its mechanism of preventing coal spontaneous combustion was revealed.In order to further explore the micro-mechanism of AFG inhibiting the oxidation process of coal molecules,ESR and in-situ FT-IR were used to determine and analyze the active radicals and functional groups in lignite,and the distribution characteristics of active groups in lignite were obtained.Based on this,simplified model compounds containing coal molecular active groups were constructed,and the theoretical calculation of the possible chain elementary reaction between model compounds and oxygen was carried out through the quantum chemistry software Gaussian 16.The cross/cycle path of chain reaction propagation in the process of coal active group oxidation and the key active groups affecting the chain reaction propagation path were determined.The changes of coal molecular active groups in the process of low-temperature oxidation were quantitatively analyzed,and the change characteristics of lignite free radical,fatty hydrocarbon functional group and oxygen-containing functional group in the process of temperature rise oxidation were obtained.The effect of AFG on the reactivity of coal molecular active groups during the heating oxidation process was comparatively studied.The chemical retarding mode of AFG inhibiting chain reaction of coal active groups was revealed.In this thesis,AFG has been prepared for preventing spontaneous combustion of residual coal in the gob.The preparation method and optimum ratio of the composite materials has been obtained.The macroscopic performance parameters and the microscopic structure characteristic value of AFG for preventing the residual coal from spontaneous combustion have been characterized,and the chemical inhibition mechanism,which the active groups of coal was prevented from participating in the chain reaction of its spontaneous combustion,was revealed.Through field tests,the performance of AFG on preventing the spontaneous combustion of residual coal in the gob was verified.