As the mining industry continues to grow, mineral recovery has become more challenging. Increasingly, mining companies are moving focus to the previously overlooked nether regions of existing ore bodies, as well as the ultra-fine particles within processed ore.
It’s not uncommon for ultra-fine particles to get sent to the tailings dam as waste material. However, more and more companies are now seeing the benefit of new gravity concentration technology to extract the finest of particles and get as much value from their ore as possible.
This issue is what inspired Steve McAlister, the founder of Falcon Concentrators and director of Sepro, to begin developing our Falcon Gravity Concentrators in his home garage over 30 years ago.
“I was working for a general contractor that did earthmoving, bridge building and subdivision construction in Canada’s Yukon Territory in the Summer of 1978. One weekend, I went for a sightseeing trip down toward Atlin, BC. On this trip, at the side of the road, I came across a brand new Caterpillar D9 tractor with the paint still on the grousers. Later, I came across some guys washing coarse gravel down what I later learned was a sluice box. When I asked them what they were doing, they said they were placer mining. They even showed me some gold. I remember thinking there must be a better way to separate tiny specks of gold from 4” rocks and also thinking that there must be money to be made if the miners can afford new Cat equipment. When I got back to the lower Fraser Valley in the Fall, I looked at various gold recovery technologies, but soon became convinced I could come up with something better. It was the beginning of a very long journey.” – Steve McAlister
A more effective method was needed to increase recovery from all types of mining projects.
Why Gravity Concentration?
Before gravity concentration equipment became so widely valued, other methods were being used to recover fine particles, and not very effectively. Cyanide, for instance, had worked well for gold leaching however most other metals require extensive preconcentration before acid leaching and solvent extraction become practical. This leaves flotation and gravity concentration as the most effective solutions. However, the smaller the particle, the more difficulties experienced during flotation in trying to get the necessary collision and release between bubbles and particles, resulting in either lower recovery or lower concentrate grade. With all of these obstacles in mind, gravity concentration is clearly the most efficient method for processing ultra-fine particles.
How Gravity Concentration Has Advanced
In the past, gravity concentration was primarily used for the recovery of fairly coarse particles but as mineral producers moved their focus to ultra-fine particles, equipment companies had to keep up. Thankfully, the Falcon research and development team have been constantly improving our equipment since its initial design.
In fact, the Falcon gravity concentrators have significantly more power than some first generation centrifuges, such as the Knelson Concentrator (as can be seen below).
|Mineral Spiral||1 G|
|Shaking Table||1 G|
|First Generation Centrifuges (Knudsen, Knelson)||5-60 G|
|Second Generation Centrifuges (Falcon)||100-600 G|
The significant difference in G-force means the Falcon Gravity Concentrators have increased settling velocity of even the finest particles.
Falcon Gravity Concentrator Case Study
Right now, Sepro’s second generation Falcon centrifuges are in operation at sites across the world. Our Falcon Semi-Batch (SB) is ideal for gold, silver and platinum group metal recovery while the Falcon Continuous (C) is perfect for concentration of tin, tantalum, tungsten, chrome, cobalt, iron, fine oxidized coal and uranium. Finally, the Falcon Ultra-Fine (UF) is a prime piece of equipment for recovering particles finer than 45 microns.
A major industrial metal producer saw great success with the installation of the Falcon C and Falcon UF. They conducted trials, analyzing recovery results when the machines were operating at different G forces.
As can be seen from the figure above, increasing from 100G to 300G on the Falcon C, resulted in a recovery increase of approximately 13%, and a relative improvement of almost 50%.
This is just one instance of how our innovative gravity concentration equipment is allowing producers to get more from their ore bodies.