Abstract
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.
Highlights
Flotation is the most effective method for separating fine coal from gangue particles (Ni et al 2018a, b; Yoon 2000)
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 leads to an increasing yield of clean coal with an increasing content of kaolinite particles
This paper argues that it is controlled by the coal particle– bubble liquid film drainage rate (Nguyen et al 1998)
Summary
Flotation is the most effective method for separating fine coal from gangue particles (Ni et al 2018a, b; Yoon 2000). These minerals include kaolinite, illite and montmorillonite The presence of these ultrafine minerals in coal flotation leads to a major problem: causing a low recovery but a high ash content of clean coal by the entrainment of fine gangues (Wang et al 2015; Yu et al 2017a, b; Zheng et al 2006). Ultrafine kaolinite particles are hydrophilic and exert less inertial force in the flow field environment, as they barely adhere to the bubble surface selectively in a thermodynamic environment. They hinder the coalescence between the particles and stabilize the suspension. Experimental chemical reagents included 2-octanol (analytical grade), NaCl (analytical grade), and Watsons deionized water with a conductivity of 0.0006 s/m. 1 mM/ L NaCl solution was prepared using deionized water and sodium chloride
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