In the last of our posts covering technology used by Polyus at its gold mining operations following IM’s attendance of the company’s Capital Markets Day, we look at improvement it has made to its flotation analysis and automation systems. Polyus has introduced a range of technologies from Outotec including the PSI 300i on-line analyser for mineral slurries; which automatically takes samples from 1-3 process streams and measures P40 to P90 particle size in the range 25-1,000 µm. Preliminary testing using PSI 300 analysis has shown optimised recovery and improvement by 0.28%. The Outotec PSI 300i sensor head directly measures the size of a representative sample of particles. The measurement data is then converted to size fraction readings for each measured stream. Each of these corresponds to a user-definable particle size screen fraction, such as percentage passing at 74 microns. This information is displayed on the analyser’s touchscreen and can be sent to plant process control system using several communications protocols.
Polyus has also installed Outotec’s FrothSense camera imaging of froth and bubble size analysis, which measures froth speed, direction, bubble size and froth stability; providing statistical data related to these variables. LevelSense is another tool that measures the slurry froth and froth air interfaces in a flotation cell. Froth bed thickness can be reliably measured with froth and slurry interfaces provided. Lastly Outotec Advanced Control Tools (ACT) represent a platform that includes interfaces for both engineering and operating customised control applications such as EXACT froth level control and automated control over the froth yield speed.
At Blagodatnoye, Polyus has installed a flash flotation operation designed to remove fine valuable mineral particles otherwise returned to a new processing cycle. The technology, first trialled by Polyus in its R&D centre, minimises overgrinding and improves overall mill throughput and recovery while optimising water cycles. It improves flotation output with more stable feed in the further flotation circuit, increasing metallurgical quality of the concentrate. Flash flotation units can halve the gold content in recirculating flows, increasing direct gold recovery. One Outotec SkimAir flash flotation unit has the same efficiency as six gravitation concentrators but requires much less space and is more economical. At Blagodatnoye, the gold content in the flotation tails in g/t stood at 0.19 before flash flotation was introduced and 0.17 after, a fall of 11%. One SkimAir flash flotation unit has been installed in Blagodatnoye Mill 4, with an additional unit being installed in 2018-2019; and another four ordered as part of the Mills 1, 2 and 3 expansion project, while the technology is also being tested at another mine.
