Rheology for thickened tailings and paste — history, state-of-the-art and future directions

Abstract

A significant development during the evolution of thickened tailings and paste technology has been the increased understanding of the importance of rheology for both design and operation of thickened tailings and paste systems. It is now well accepted that dewatering, pipeline transport and deposition processes are all rheology governed and that the more the rheology is understood, and in some cases manipulated, the more successful the operation will be. This increased knowledge and adoption of rheology has led to a paradigm shift where tailings are engineered to suit the environment rather than engineering the environment to suit the tailings. In the early to mid 1970s when Eli Robinsky first introduced the concept of thickened tailings disposal, the systems were based primarily on empirical flume tests. Since that time, numerous advances in measurement techniques have facilitated the understanding of the influence of variables such as particle size distribution and shape, shear effects (rate and time of shear) and mineralogy on the rheology of tailings. Compressional rheology has also emerged as a whole new area of interest. This progress, coupled with advances in understanding the interrelationship between surface chemistry and rheology, has highlighted methods of exploiting and/or manipulating the dewatering, flow and depositional properties of tailings and backfill. As flocculant and other additive technologies advance, we may begin to see more complex rheological phenomena and new measurement techniques may need to be adopted or developed for a fuller understanding and exploitation of slurry and paste rheology. The paper examines the driving issues faced in the past, now and likely in the future, the testwork that has been developed and its applicability or limitations and how this has progressed thickened tailings and paste technology.

Next generation polymeric flocculants for thickening and dewatering

“…Clay mineralogy and morphology can have a dramatic effect on how polymers flocculate and modify the rheology of mineral slurries. Particle size distribution, surface charge, particulate shape, and chemical composition are some of the factors that are important to consider while designing flocculants and/or trying to modify the rheology of the tailings slurry (Sofra and Boger, 2011). Therefore, it is important that the flocculant design focus on targeting multiple performance criteria tailored to specific mineralogy.…”

“…As mentioned previously, increased water recovery has become very important to large numbers of mining operations throughout the world, and it is essential that this recovered water or overflow is clear and free of suspended particles so that it can be easily recycled back into the main stream (Slottee and Biesinger, 2011;Sofra and Boger, 2011). Therefore, it is important that the flocculants not only help in dewatering, but also generate a clear supernatant during the sedimentation/thickening process.…”

Rheology applied to the environmental management of mineral tailings: focus on safer disposal and water reuse

“…Yield stress (τ 0 ) can be estimated from different rheometry techniques. All τ 0 data presented in this study were obtained using the vane technique, to eliminate slip (Boger, 2009(Boger, , 2013Sofrá and Boger, 2011). Two measurement techniques were used to obtain the τ 0 : direct method and regression method based on the flow curve results.…”

“…Particles smaller than 28.3 µm accounted for 90%, 5.9 µm accounted for 50% and finer than 1.3 µm represented 10% of the total amount of tailings. This particle fineness associated with strong electrostatic repulsion in natural pH (7≤pH≤8) (Figure 2b), impairs the natural sedimentation process (Sofrá and Boger, 2011). However, the presence of fine material is indispensable for paste formation.…”

“…Their characteristics are highly dependent on the type of polymer-slurry interaction and the floc formation process (Dias et al, 2004;Jarvisa et al, 2005). Therefore, the yield stress is strongly dependent on the dosage and polymer structure as well as tailings characteristics, such as particle size and shape, solids concentration, surface charge density, solid density, bulk density and pH (Sofrá and Boger, 2011;Parsapour et al, 2014;Wu et al, 2015).…”