If you thought blowing bubbles was child’s play, think again!
For many years now froth flotation has been used in the mineral industry to separate fine particles. Now research at the University of Newcastle, lead by Laureate Professor Graeme Jameson, is looking at a new way to recover even larger particles.
Professor Jameson became well known in the industry for the invention of the Jameson Cell, a radically different flotation device that has since been installed in locations all over the world. Currently, the Jameson Cell injects approximately $4 billion a year into the economy from coal exports. Now he has made a new flotation discovery that has the potential for large savings in energy and water consumption in mineral processing.
Froth flotation requires material to be ground to a size smaller than 100 microns – about the size of a human hair. The crushed particles are suspended in water and air bubbles lift the valuable materials to the surface for collection. Crushing and grinding use a lot of energy, and according to the CSIRO as much as 14 percent of Australia’s annual electricity production is spent crushing rocks for mineral processing. Many mines are found in remote locations and must generate their own energy to crush materials.
Professor Jameson’s invention is a Fluidised Bed Flotation Cell with the potential to recover coarse particles as large as 600 microns, reducing grinding energy by as much as half. The new process is ideal for the recovery of copper, gold, silver, nickel, lead and zinc.
“A device like this will maximise mineral recovery, as well as yield significant savings in both energy and money” said Professor Jameson.
“Another substantial benefit is that reducing the need to produce as much energy also minimises the amount of greenhouse gas emissions created during electricity production.”
As with current designs, the new process begins when air bubbles are introduced to a slurry of ground particles in water, in a vigorously stirred vessel. The valuable minerals attach to the bubbles and rise with them to the top of the vessel to form a froth. The waste material remains in the slurry and is discharged as tailings. With existing cell designs, particles are suspended by a turbulent agitator whereas in the Fluidised Bed Cell they are suspended by a gentle up flow of water.
“What differentiates this new Cell from those being used now is the gentleness of the technique. Currently, larger particle sizes cannot be lifted beyond a certain point because the boisterous action of the agitator knocks the larger particles off the bubbles, and they go to waste with the tailings” said Professor Jameson.
“A gentler environment helps larger particles to stay attached to the bubbles.”
The Fluidised Bed Flotation Cell has been tested in a laboratory pilot plant with high recoveries of minerals of up to 1.4mm in size being achieved.
“This new design can lift particles as large as coarse grains of salt and pepper – particles large enough for you to feel in your shoe! No other technology can handle them” said Professor Jameson.
The design is soon to be trialled on real ores at an operating mine.
Laureate Professor Graeme Jameson AO
Centre for Multiphase Processes
University of Newcastle, Australia
T: (02) 4921 6181
E: Graeme [dot] Jameson [at] newcastle [dot] edu [dot] au
Newcastle Innovation Ltd
T: 02 49218777
E: innovation [at] newcastle [dot] edu [dot] au