Coal Preparation » Dewatering
The aim of this project was to develop an instrument that is capable of accurately and reliably measuring the quality of the thickener underflow in an operating coal preparation plant environment.
Overall the values obtained for viscosity, particle density, slurry density and solids concentration from the TUM versus laboratory results were excellent. The TUM in its current form would be a valuable tool for CHPP operators and tailings processing/monitoring. The viscosity measurement allowed for an accurate calibration of the TUM in regards to solids concentration.
There exists a need to measure viscosity online at much lower shear rates. The online measurement used was using a very high shear rate, due to using a vibrating/oscillating tube to perform the measurement. Although the single point was quite accurate and could be used in plant operation, a full description of the viscosity profile is a very powerful tool. As equipment becomes available, this will be incorporated into future TUM units.
With this information, it may be possible to better understand and optimise both the thickener and downstream processes. These processes may include pumping and handling of tailings, further dewatering of thickener underflow and tailings dam storage.
Dewatering of CHPP fine tailings material is becoming more important due to the high costs associated with construction of tailing dams, the environmental approvals process required for new tailings storage becoming increasingly difficult, the increasing requirement to reclaim and recycle water while minimising waste, tailings dam reclamation bonds and tailings transport and emplacement costs and levies.
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, 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.
The TUM also produced accurate results on the feed to the secondary dewatering equipment (solid bowl centrifuge) during the trial. This data could be used by the plant to optimise parameters such as solids feed rate, water feed rate, flocculant addition and slurry density.