Experimental study of influence of coal dust physical-chemical properties on indirect dust suppression effect

Indirect dust suppression parameters are one of the main indicators for evaluating the performance of dust reduction, and the physical and chemical properties of coal dust are important factors affecting the indirect dust reduction effectiveness. To clarify the influence of coal dust physical and chemical properties on the indirect dust suppression effect, atomic force microscope(AFM), laser particle sizer, infrared spectrometer were used to analyse raw coal dust characteristics (the particle size, roughness, adhesion force and functional groups) sampled from different mines, and sedimentation and agglomeration experiments were used to study the indirect dust suppression effect (the law of wettability and agglomeration) of the coal dust under different characteristics. The results showed that the median particle size of SY and DJH coal dusts was significantly lower than that of HL and YH coal dusts. The average roughness ranged from 1.10 to 2.62 nm, and the maximum roughness ranged from 7.18 to 26.7 nm. The coal dust had a small adherence force, and the agglomeration ability occurred by itself was difficult. Furthermore, the difference of the functional groups structure for four coal dusts was small, but it showed an obvious difference in the proportion of functional groups. As the decrease of particle size, the roughness of coal dusts increased, and its wetting velocity decreasing trend showed a power function. The higher the surface roughness of coal dust, the stronger the hydrophobicity of coal dust. With the hydroxyl proportion percentage increased, the coal dust wetting velocity increased linearly, and the increase of hydroxyl functional group proportion greatly promoted the agglomeration of fine particle coal dust. The agglomeration effect enhanced first and weakened after with coal dust particle size decreased, which reflected the fact that the largesize coal dust was more easily wetted by reagents, but it was difficult to form stable liquid bridges. Furthermore, the smaller size of coal dust showed a poorly wettability, it was unable to form effective agglomerates. Coal dust adhered to the surface of the droplets under the action of the liquid bridging force, and as the water evaporated, the coal dust formed stable solid bridges between them.