Effect of ultrafine kaolinite particles on the flotation behavior of coking coal
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Effect of ultrafine kaolinite particles on the flotation behavior of coking coal Yijiang Li1 • Wencheng Xia1
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Yaoli Peng1 • Yanfeng Li1 • Guangyuan Xie1
Received: 19 October 2019 / Revised: 5 December 2019 / Accepted: 19 February 2020 Ó The Author(s) 2020
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. Keywords Coal flotation Surface tension Apparent viscosity Liquid film drainage
1 Introduction Flotation is the most effective method for separating fine coal from gangue particles (Ni et al. 2018a, b; Yoon 2000). There are many ultrafine gangue minerals in the flotation pulp, which are produced by grinding or mudding of the clay minerals. 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). Therefore, it is essential to
& Wencheng Xia [email protected] 1
School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
reduce the mineral matter in clean coal to reach the requirements for coal utilization. In the past 100 years, the negative effects of fine slimes on coal flotation have been extensively studied (Gulsoy 2005; Ni et al. 2015; Zhang et al. 2013). However, in recent years, many scholars have found that in the flotation process, the presence of a small amount of ultrafine particles helps to increase the stability of the froth layer, thereby increasing the recovery rate of the flotation concentrate (Horozov 2008; Ni et al. 2018a, b; Zhang et al. 2008). The essence of coal flotation is that the coal particles collide with the bu
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