Determining the Benefits of Online Thickener Underflow Rheology Measurements

The aim of this project is to determine how useful the rheology measurements generated by the Thickener Underflow Monitor (TUM) are to CHPP operations. The TUM is currently able to generate information regarding the rheology of coal thickener underflow but the usefulness of this information is not well understood.  It is the purpose of this project to determine if and how these rheology measurements can be applied to standard thickener operations, paste thickener operations, secondary thickening operations, belt filter presses and other mechanical dewatering devices.

Currently there are no online rheology measurements of thickener underflow and it may be possible, with online measurement, to reduce flocculant dose rates, particularly where flocculant is dosed after the thickener.

The TUM will measure the solids and water loadings and also the dynamic and kinematic viscosity of the tailings slurry. With this information, it may be possible to better understand and optimise both the thickener and downstream tailings processes. These processes may include pumping and handling of tailings, further dewatering of thickener underflow and tailings dam storage.

To efficiently operate a dewatering process, the feed quality must be known. By having a feed stream that is measured and quantified online, it allows for optimisation of both upstream and downstream processes. Variations in thickener output can be monitored online, while the downstream mechanical dewatering equipment can be optimised, along with flocculant dosage, increasing the process efficiency, throughput, and consistency of the dewatered product for disposal. This would allow maximum water recovery and increased handleability of the discharge material. Solids loadings and water loadings readings may also allow improved determination of the amount of dewatering required and the life of tailings dams, as well as fine-tuning of equipment.

Investigation of slurry parameters such as viscosity, slurry density and solids concentration will also be performed. Viscosity, solids loading and volumetric loading are important factors for dewatering equipment and pumping, particularly for mine sites who pump tailings material long distances to tailings dams. The equipment may also be further developed for sites who require better monitoring and control of reject co-disposal systems, as these measured slurry parameters are often crucial in the system either working effectively or not.

The Thickener Underflow Monitor will incorporate measurement devices to measure and investigate:

• Solids flow rate (Solids loading), in both t/h and m³/h;
• Water flow rate (Water loading), in both t/h and m³/h;
• Slurry viscosity - dynamic and kinematic;
• Solids concentration - mass and volumetric basis;
• Slurry density;
• Conductivity;
• pH;
• Particle density.

Use of this supplied online data in an operating CHPP would allow thickener underflow monitoring and optimisation of downstream processes such as dewatering and the pumping of tailings. This would lead to increased process efficiency by maximising water recovery, minimising waste material and reducing operating costs.