Study On Wettability Mechanism Of Coal Dust

Coal dust hazard is one of major disasters in coal mine. Coal dust explosion causes a large number of casualties and huge economic losses, and long-term inhalation of respirable dust will lead to pneumoconiosis. In order to reduce the coal dust effectively, the key is to improve the wettability of coal dust.In this paper, the coal dust physical and chemical characteristics are systematic analyzed, and puts forward a quantitative characterization of coal dust particle size distribution fractal dimension and surface fractal dimension. There are three types of main groups on the coal dust surface are aliphatic hydrocarbons, aromatic hydrocarbons and oxygen containing functional groups. Large number of aliphatic hydrocarbons, aromatic hydrocarbons and other hydrophobic groups on the coal dust surface are major cause of strong hydrophobicity on the coal dust surface.Drop patterns optical analysis system (DSA100. Krüss Company. Germany) is used to measure the contact angle of water contact with coal dust sample, and study correlation between composition of coal dust, chemical elements, micro-structure, total acid group content, size fractal dimension and surface fractal dimension with wettability of coal dust. The application of SPSS software aims at studying the major effect factors of coal dust wettability. The study testifies that the total acid-functional group and the fixed carbon content are important factors impact the coal dust wettability.FTIR spectroscopy, XPS spectroscopy, surface and pore size analysis, wetting, and other means of experimental are applied to study the respirable coal surface wetting properties and mechanism. The research shows that the coal dust surface structure, chemical composition and elements composition are changed in the coal dust refining process. Compared with large particles coal dust, respirable coal dust has weaker hydrophilic and stronger hydrophobic. The reasons are the smaller the particle sizes of coal dust, the more unsaturated the surface .And the absorption of air is stronger, and easier to form a air film on the coal dust surface; coal dust contact with water is actually the compound contact of liquid contact with solid and gas contact with solid. The smaller the particle size, the larger the pore volume, and the higher the rough degree of surface, the larger area of gas contact with solid, the worse the coal dust wettability.According to the mechanism of water or wetting agent witting coal dust, a dynamic model of liquid wetting coal dust surface is established. And the thesis puts forward K Value to characterize the liquid wettability wetting on the coal dust surface, and uses the dynamic wetting model to study different kinds of surfactant system wettability.Form the micro point of view and molecular level to explore the surfactant adsorption mechanism, the thesis puts forward a new method to determine nonionic surfactant concentration JFC by I₂-KI reagent, and studies theξpotential affected by surfactant. The paper expounds that the mechanism of liquid wetting coal dust is caused by liquid molecular adhesion on surface molecular which is different from liquid cohesion. The interaction of coal dust surface molecule and liquid molecular adhesion is resulted by combined action of molecular short and long range force.