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Received Dec 18, 2017; Revised Mar 6, 2018; Accepted Mar 21, 2018
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1. Introduction
The pipeline transportation of tailings slurries has been a fast, environment-friendly, and economic choice for many mines around the world. The tailings slurries usually contain significant fractions of fine and coarse particles, causing them to exhibit non-Newtonian flow behavior and high frictional pressure gradients [1]. Due to the high capital and operation costs of positive displacement pumps for transporting tailings, it is of great significance to optimize the properties of tailings slurries so that they are sufficiently pumpable and flowable.
Flocculation is an important stage in the filtered tailings disposal process and is a necessary procedure in tailings thickening to enable the rapid settling of fine tailings particles [2]. Commonly used flocculants in tailings thickening include inorganic flocculants, organic polymer flocculants, microbial flocculants, and coagulant agents [3]. Flocculation is a complex physical and chemical reaction and involves charge neutralization, amphipathic adsorption, and selective agglomeration [4]. As a result, most of the flocculants bond with tailings particles and exist in the thickened tailings slurry, which changes the internal structures and affects the rheological characteristics of the slurry during pipeline transportation. Therefore, investigation into the mechanism of the flocculent effect on the characteristics of the thickened tailings slurry is important in order to complete its pipeline transportation theory.
In previous studies, the effects of flocculants on structural stability were ignored, and thickened tailings slurries were simplified as Bingham plastic fluid in pipeline transportation, whose flow properties were time-independent [5]. However, an increasing number of studies have found that this does not appear to be the case. Pornillos found that the yield stress and viscosity of Pd-Zn thickened tailings slurry decrease as the shear time increases and eventually stabilize [6]. Autier analyzed the effect of polycarboxylate on particle dispersion in cement paste using scanning electron microscopy and laser granulometry [7]. Yang et al. evaluated the dynamic damage and recovery process of flocculent structures and derived a high-precision time-varying hydraulic gradient model [8]. The above studies have achieved significant breakthroughs in exploring the effect of...