Flotation Of Coal Particles Research Articles

Effect of ultrafine kaolinite particles on the flotation behavior of coking coal

Kaolinite, as a mineral in fine coal, has an important influence on the flotation of coal particles. In this study, the effects of ultrafine kaolinite particles on the flotation recovery of coal particles were investigated. Flotation tests were carried out using a mixture of coal particles and different amounts of ultrafine kaolinite particles. Combined with the Stefan–Reynold theory, the effect of liquid film drainage rate between coal bubbles in a kaolinite suspension was calculated. The yield of flotation clean coal increases quickly with the increasing content of ultrafine kaolinite particles. The ultrafine kaolinite particles can reduce the surface tension of the suspension, weaken the bubble coalescence, and stabilize the structure of the froth layer. In addition, the ultrafine kaolinite particles increase the apparent viscosity of the flotation pulp slightly. It is concluded that the role of ultrafine kaolinite particles on the positive effect of froth properties conceals the negative effect on the liquid film drainage rate between coal particles and bubbles caused by the kaolinite particles, which ultimately leads to an increasing yield of clean coal with an increasing content of kaolinite particles. This study is important for understanding the influence of ultrafine kaolinite on coal particle flotation.

Flotation of coal particles in MgCl 2, NaCl, and NaClO 3 solutions in the absence and presence of Dowfroth 250

Separation of naturally hydrophobic particles, such as coal, by flotation is known to be enhanced with the addition of salt solutions into the system. However, the exact reasons for this enhancement are not clear yet. In this study, flotation of coal particles in MgCl 2, NaCl, and NaClO 3 solutions in the absence and in the presence of a strong frother, i.e., Dowfroth 250, was investigated to clarify the flotation enhancement mechanism and to correlate the flotation recovery with froth stability and bubble size distribution at the froth phase. The results of the flotation experiments showed that the presence of electrolytes in the system clearly enhanced the flotation recovery depending on its type and concentration. During the experiments, MgCl 2 and NaClO 3 solutions showed the highest and the lowest flotation performance improvements, respectively. The froth stability tests indicated that there is a correlation between the flotation recovery and the stability profile of the froth. The most stable froth was obtained with MgCl 2 and the lowest froth stability was obtained with NaClO 3. Additionally, a direct correlation was found between the flotation recovery and the bubble size distribution of the froth phase. The bubble size measurements revealed that increasing the electrolyte concentration decreased the bubble size, which, in turn, increased the flotation recovery. It is concluded that, the addition of salt solutions to a flotation system produces finer bubble size distribution at the froth phase, which enhances the coal flotation kinetics, depending on the type and the concentration of the electrolyte.