Project Status: Complete
Project Participants: CSIRO, University of Queensland, Murdoch University
Project Leader: Marko Hilden (University of Queensland)
Large banana (multi-slope) screens are widely used in the iron ore industry to perform separation of ore from fines because of their high capacity over the older-style flat-deck screens. However relative to the older screen designs, banana screen efficiency is poorly understood and it is difficult to optimise screen performance because of the large number of factors that affect its performance.
There is a need for modelling capabilities that can be used to predict screen performance with a view to optimising separation efficiency, capacity and wear. This project demonstrated to industry participants the Discrete Element Method (DEM) / Virtual Comminution Machine and scale modelling capabilities of an industrial banana screen application.
Due to lack of access to full-scale site data, the JKMRC pilot screen (of 1m length) was modified to provide high-quality validation data for the DEM modelling. This data was then supplied to CSIRO Mathematics, Informatics and Statistics to match with the DEM modelling.
DEM predictions of flow and separation efficiency using spherical particles were compared to experimental data in order to assess their accuracy. Reasonable agreement was for low feed rates, however at higher feed rates, very significant deviations between the experiment and the simulation emerged.
The DEM study of the separation performance of double-deck banana screens lead to interesting insights. Using realistic non-round particles gave an opportunity to seriously explore industrial-scale screen performance in much more detail than is possible with traditional testing techniques – although good quality survey and wear measurements will be essential for verification of the DEM models.
A full-scale screen was modelled with DEM and then with a combined DEM and Smoothed Particle Hydrodynamics to model both the particles and the fluid flow. At mid-range speed (peak acceleration of 5g), the separation performance of the top deck is good and a deep bed quickly builds up on the bottom deck.
DEM simulation of full-size two deck banana screens is now feasible. Models including the full geometry of the screen, its motion, and the shape of the particles can now be solved with more than 200,000 particles in reasonable computation times, and predictions of separation performance and of the flow through the screen are quite realistic.