Flotation model
24 Jan 2005
A flotation model developed at the University of South Australia can be applied to increase the recovery and quality of minerals from both fine and coarse particles.
Researchers at UniSA's Ian Wark Research Institute developed the model, which can be applied to any mineral system, according to Senior Research Fellow, Dr. Stephen Grano.
"Mining companies using the flotation model have the potential to increase recovery in most plants by about 2-5% because the model gives a better description of the key parameters that need to be optimised to increase recovery," said Grano.
"Flotation is the most extensively used method worldwide to separate minerals from mineral resources. With more efficient flotation, more valuable minerals can be extracted from the ore. Even small improvements of 1 or 2% can equate to millions of dollars in savings, depending on the size of the operation and value of the mineral recovered," Grano added.
To extract the minerals using flotation, finely crushed ore, with water added to form a slurry, is transported to separation tanks where it is vigorously agitated and aerated to create a froth. Chemicals are added to stabilise the froth, while other chemicals selectively coat the minerals, making them hydrophobic or water repellent.
This causes the minerals to collide and attach to the bubbles in the separation tank and float to the surface of the tank, where they overflow into collection launders, while the residue or tailings sink to the bottom for disposal. The recovered minerals are then filtered to remove most of the water before being dried for transportation.
Being able to optimise the valuable mineral recovery from both very fine and coarse particles, as well as being able to recover minerals selectively during flotation, are among the most significant challenges confronting the mining industry.
If the minerals could be recovered efficiently from coarse particles during the flotation process, mining companies could cut costs considerably by reducing the extent of ore grinding, a process that involves high operating costs and is a huge drain on energy resources. Further, coarser grinding may enable fewer chemicals to be used.
The flotation model is a mathematical description of the separation process and can be used as a benchmarking tool and for optimising the separation process. Given the type of mineral particle and its size, an engineer can determine the best slurry flow rate, turbulence level and bubble size, so that the particles not only collide with the bubbles but also attach selectively during collision. The particle size determines how quickly and efficiently they collide and attach to the bubbles. Very fine particles collide with the bubbles infrequently and at a much slower rate than large particles, which collide easily but may also detach more readily because of the instability of the bubble/particle union.
If the model is incorporated into software, mining companies could predict what would happen if any changes were made to the process such as different bubble sizes, turbulence or residence times. They could also access an avenue of technology transfer that does not need lengthy training or explanation, and any new updates could be automatically incorporated into the software.
When building a flotation plant, which requires considerable capital expenditure, the flotation model can be used to determine how many and what size tanks should be built, helping mining industries to reduce the financial risks involved.
Professor John Ralston, Director of the Ian Wark Research Institute, Senior Research Fellow Associate Professor Daniel Fornasiero and Dr. Grano have been conducting research on the flotation model with funding of $2.2 million from AMIRA International and the Australian Research Council.
