Studying feasibility of paste and thickened tailings at laboratory scale – pilot thickeners

Abstract

Thickening tailings until they reach a paste-consistency configuration is a process involving many factors. Lab scale work is required prior to studying the feasibility of paste thickening technologies for a given tailings. The global objective is to determine if a representative sample of non-thickened tailings can be engineered at laboratory scale to make paste; this work and its results will help determine the feasibility of the thickening process and the potential paste characteristics at industrial scale. This document aims to justify the need for this lab scale work and to provide information regarding lab scale paste thickeners by presenting the experiences obtained with an experimental lab-scale thickener.Studying the feasibility of a paste and thickened tailings (P&TT) alternative for a mine requires different types of laboratory and pilot scale tests. Many parameters and factors will affect the viability of these technologies for a given case. If we examine the most widely accepted theory, it seems that global design should flow 'upstream', starting from the storage area characteristics, stepping back to the piping requirements, and finally defining the thickening process to suit the required characteristics of the underflow.The characteristics of tailings are probably the most important of the factors affecting the viability of the whole process. Location determines the climate, and especially the geological and mineralogical properties of the deposits, but tailings should not be considered as a natural material. They are a waste product of the mining process and are affected by several other parameters: the process used to separate the gangue from the ore, the chemicals added during these processes, the characteristics of the water used, etc. Even during the lifetime of a mine, the tailings characteristics may change due to evolution of the mineral grade and the associated beneficiation process.All these arguments make tailings processing not only site dependant, but also time dependant. The design of a P&TT process to thicken the waste of a mine requires a strong phase of prior research to determine its feasibility; not all tailings are amenable to being 'engineered' to reach paste consistency. Even if they are, there are several parameters that can be modified, such as additives, dosage, solids percentage, rheological properties, etc.Thickener design should adapt to these requirements. However, few reference documents with procedures to design these pieces of equipment are available. It seems clear that producing paste at lab scale is imperative in order to have a first idea of how the tailings will behave after being thickened. In order to do this, having a bench scale thickener seems to be a good alternative. Static settling tests do not seem to resolve the need to determine underflow solid concentrations and overflow water characteristics. There is no reference bibliography to construct pilot units; in this study, an experimental column of 9 cm diameter is tested, operating in batch mode, providi...

Feasibility of High-Density and Non-Segregable Niobium Ore Tailings

“…The bench scale thickening test is widely used to identify the characteristics in the thickener underflow, even if approximately, but it is still recommended to carry out tests on a larger scale for a better approximation [16]. Barrera and Engels [17] also highlighted the limitations of bench scale tests with high density slurries and the importance of pilot tests.…”