Impact of Clay Minerals on the Dewatering of Coal Slurry: An Experimental and Molecular-Simulation Study

Abstract

The cleaning process of coals is challenging due to the existence of clay minerals. The overall objective of this study is to investigate how the dewatering of coal slurry is impacted by the presence of clay minerals, i.e., kaolinite and montmorillonite. Filtration tests were first conducted to investigate the effect of kaolinite and montmorillonite on the dewatering efficiency of coal. Specifically, we measured the filtration velocity, moisture, average specific resistance, and porosity of filter cakes for six slurry samples, in which different amounts of kaolinite and montmorillonite were contained. Filtration tests show that a small amount of kaolinite and montmorillonite leads to a significant reduction in the filtration velocity and porosity, and a big increase in the average specific resistance and the moisture of the filter cake. We observe that most kaolinite existed in the top and middle layers of the filter cake, while most montmorillonite existed in the top layer; on the contrary, little montmorillonite is observed in the middle and bottom layers of the filter cake. Montmorillonite results in a much more deteriorative effect than kaolinite. Considering that the interactions between clay minerals and water may play a key role, we then further investigate the effect of such interactions using molecular simulations. Simulation results show that water molecules could hardly diffuse into kaolinite from the edge, while they could readily penetrate into the montmorillonite layers from the edge surface. This result can be explained by the hydrated cation in montmorillonite. The adsorption density of water on the octahedral surface of kaolinite is higher than that of water on the tetrahedral surface of kaolinite. Furthermore, the adsorption density of water on the double surfaces of kaolinite is higher than that of water on the montmorillonite surface. This research is expected to provide benefits or contributions to the dewatering of clay-rich coal tailings.

Rheological Perspectives of Clay-Based Tailings in the Mining Industry

“…Clays are a consistent focus of research because they negatively impact almost all processes in the mining sector, including leaching, flotation, pulp transport, thickening, etc. [16,30,31]. These phyllosilicates can be classified according to their swelling (e.g.…”

Trends in Modeling, Design, and Optimization of Multiphase Systems in Minerals Processing

“…Ma et al [11] studied the impact of clay minerals (kaolinite and montmorillonite) on the dewatering of coal slurry using a molecular-simulation study, followed by an experimental section to corroborate data accuracy. The molecular simulation results show different adsorptions of water on the side surfaces of kaolinite and montmorillonite.…”

“…Example of an equilibrium snapshot from a molecular dynamics (MD) simulation of water adsorption on the side surfaces of (a) kaolinite and (b) montmorillonite at 298 K and 1 bar[11].…”

Effect of shear-induced breakage and reflocculation on the floc structure, settling, and dewatering of coal tailings

“…In coal preparation plants, wet washing and screening processes produce large amounts of tailings (Hansdah et al, 2017, Li et al, 2020, Lu et al, 2019. Flocculation-based solid-liquid separation is widely employed in the treatment of coal tailings (Ma et al, 2018, Zhang et al, 2017. In industrial production, flocs are always in a dynamic balance of flocculation, breakage and reflocculation under the action of flocculants, hydraulic shear and even mechanical shear in transportation , Ofori et al, 2011.…”