The October issue of the magazine takes a detailed look at new ideas and technologies in tailings management and the best way to use them. The ability to pump tailings from the mine to the pond depends on the composition and viscosity of the tailings. To determine if tailings can be pumped with the existing pumping equipment, the viscosity and the yield stress need to be measured. The yield stress value is strongly dependent on solid content of the slurry. Australian company Rheology Solutions defines these important rheological properties as follows:

• Yield stress: a measure of the solids loading of concentrated suspensions, pastes and other multi-phase mixtures. This measurement tells us the minimum force required to initiate movement in a material, and indicate for example the pumpability of the material or enable prediction of beach-slope and the possibility of slip or failure of tailings dams
• Steady shear viscosity: the viscosity is a measure of the resistance of a material to flow. It is a critical input for assessing the pumpability of a material, as well as the probable efficiency of mixing or separation processes
• Viscoelasticity: the viscoelasticity of a material can gently (without damaging the structure) measure the internal structure of a material. In this way the effectiveness of different processes (or process additives) can be observed – e.g. localised testing of the process of flocculation.

Rheological measurements such as viscosity, elasticity, processability, temperature-related mechanical change, and the yield stress value of mining tailings can be extracted easily from a simple measurement using a rheometer. Those values can then be easily correlated with the pumpability of a specific tailing formulation with given solids mass fraction.

The Application Note, Correlating yield stress with pumpability of mining tailings by Jan Philip Plog, Thermo Fisher Scientific, explains that the vane rotor method on the HAAKE Viscotester iQ rheometer “is a quick, simple and accurate approach to measure the yield stress of mining tailings. Those values can then be easily correlated with the pumpability of a specific tailing formulation with given solids mass fraction.”