Coal dust is a primary threat to underground coal miners. The most common approach to control coal dust is hydraulic methods, such as water spray and coal seam water injection. To improve the dust suppressant efficiency of hydraulic methods, a novel chemical composite dust suppressant, called NCZ, was prepared in this study using calcium chloride (CaCl2), magnesium chloride (MgCl2), and nonionic surfactants using a thermal synthesis method. The water-retaining properties of NCZ powder and its solutions were characterized using the water absorption rate (WAR) and evaporation rate (ER), respectively, and the wetting abilities of the NCZ solutions on coal dust were tested using the initial contact angle (ICA) and sink rate (SR). The results indicate that the NCZ solutions have anti-evaporation effects, and the ER of the solution with a 20.0 wt% NCZ is reduced by 11.7% compared with that of clean water. Furthermore, NCZ solutions have remarkable enhancement effects on the wettability of coal dust. The ICA and SR of clean water and the NCZ solution at 20.0 wt% are 141.9° and 0 mg/s, and 29.3° and 1.46 mg/s, respectively. Finally, quantitative relationships between the solution surface tension and the ICA and IR were established using the least squares method. This study provides a new product for dust suppression in underground mines, which is significant for the optimum applied concentration of dust suppressant in mining operations.
To investigate the factors affecting the wettability of copper mine blasting dust, the primary blasting dust was collected from an open-pit copper mine and separated into hydrophilic blasting dust (HLBD) and hydrophobic blasting dust (HBBD) using water flotation method. The physicochemical properties of HLBD and HBBD were measured and compared with each other. The properties included particle size distributions (PSDs), micromorphologies, pore structures, mineral components and surface organic carbon functional groups. The results show that particle size and pore structure of the blasting dust are the main factors affecting its wettability. Specifically, particle size of HBBD is smaller than that of HLBD, and their respiratory dust (less than 10 µm) accounts for 61.74 vol% and 53.00 vol%, respectively. The pore structure of HBBD is more developed, and the total pore volume of HBBD is 1.66 times larger than that of HLBD. The identical mineral compositions were detected in HLBD and HBBD by X-rays diffraction (XRD); however, the surface organic hydrophobic component of HBBD is slightly larger than that of HLBD, this may be the reason for the poor wettability of HBBD. This study is significant to understand the effects of physicochemical properties of copper mine blasting dust on its wettability.
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