Study On Physicochemical Properties And Dustfall Experiments Of Coal Dust With Different Particle Sizes

Coal dust is one of the five major disasters in coal mines,which seriously affects the high-efficiency production of coal mines and the health of workers.Since 2005,there have been 11 coal-dust-related explosions in China,causing 397 deaths,and about 10,000 cases of pneumoconiosis each year,including 1900 deaths.Respirable dust has a significant difference in physical and chemical properties from large particles due to its small particle size,and is more likely to be suspended in the air,resulting in coal dust explosion and pneumoconiosis.Therefore,it is necessary to study the effect of particle size change on the physical and chemical properties of coal dust and the dust reduction process.In this paper,four kinds of coals,namely Liuta lignite,Bulianta long flame coal,Luwa 1/3 coking coal and Huangyanhui anthracite,were selected as experimental coal samples,and the physical and chemical properties,adsorption and wettability of the same coalification degree dust under different particle size conditions were systematically studied.The main influencing factors of coal dust wettability were analyzed by SPSS software.Combined with the spray dust reduction system,the sedimentation efficiency of coal dust with different particle sizes was determined,and the influence of particle size on the dust reduction process was analyzed.The surface morphology,specific surface area and pore structure of coal dust with different particle sizes were studied by SEM and liquid nitrogen adsorption instrument.It was found that coal dust has typical fractal characteristics.With the decrease of coal dust,particle size fractal dimension and surface fractal dimension increases and the surface of the particles is rougher.The coal dust of different particle sizes of the same coal has the same morphology of adsorption and desorption isotherms.With the refinement of the particles,the small-scale pores contained in the coal increase,and the BJH total pores volume and BET specific surface area increase.The effects of particle size on surface functional groups,zeta potential and adsorption of coal dust were studied by FT-IR,electrophoresis and ultraviolet spectrophotometer.The results show that as the particle size decreases,the aromatic hydrocarbons which were represented by aromatic rings and substituted benzenes contained in the coal dust increase,and the hydroxyl groups,carboxyl groups and carbonyl groups of the oxygen-containing functional groups decrease.After the dust is refined,the surface electronegativity increases,and the electrostatic repulsion between the particles increases,making it difficult to agglomerate and settle.As the particle size shrinks,the equilibrium adsorption capacity of coal dust increases,the adsorption kinetic constant decreases,and the longer the time required to reach the equilibrium state,resulting in uncompleted adsorption of particles and reduced dust reduction efficiency.The contact angle method and coal dust sedimentation experiment were used to determine the wetting phenomenon of coal dust with different particle sizes.It was found that with the decrease of particle size,the contact angle and settling time of coal dust increased,and the surface hydrophobicity increased.Combined multivariate stepwise regression analysis,the significant factors that influence the wettability of coal dust are surface fractal dimension,hydroxyl and carboxyl groups.The sedimentation efficiency of coal dust with different particle sizes was studied by spray dust reduction experimental system,and the reasons for the difference of coal dust settlement with different particle sizes were explained.The results show that with the decrease of particle size,the dust reduction efficiency of the same metamorphic coal sample decreases gradually.This is because the microscopic characteristics of coal dust change with the reduction of particle size.On the one hand,changes in zeta potential and adsorption characteristics directly affect the dust reduction process.On the other hand,surface morphology,specific surface area,pore structure,functional groups and other properties use wettability as a medium to indirectly affect the sedimentation of dust.The combination of the two hinders the agglomeration and sedimentation between the particles.