FLOTATION equipment.
In another IMPC paper, Significance of Exposed Grain Surface Area in Coarse Particle Flotation of Low-Grade Gold Ore with the HydroFloat Technology, J. D. Miller et al note that“ conventional flotation machines are typically limited to a particle top size of 150-200 µ m due to inherent constraints created by the pulp and froth phases. To overcome these limitations, a novel fluidised-bed flotation system called the HydroFloat Separator has been developed specifically for the purpose of floating coarse particles containing only small amounts of exposed hydrophobic minerals. Over the last decade, this technology has been successfully applied to industrial minerals with several fullscale units installed to recover particles up to and exceeding 3,000 µ m diameter.
“ More recently, sulphide-based test work has shown that this novel device is also capable of recovering metalliferous values at a grind size that is much coarser than currently used in industrial concentrators. In the current study, high resolution X-ray micro tomography( HRXMT) was used to experimentally compare the degree of exposed grain surface area necessary to recover coarse particles using the HydroFloat technology to that attainable using a traditional mechanical flotation cell. The data indicate that exposed grain surface area is a critical factor for coarse particle flotation.
“ For the gold-bearing sulphide ore examined in this study, the HRXMT data suggest that near complete recoveries of coarse( 850 x 500 µ m) multiphase particles containing as little as 1 % exposed grain surface area were realistically attainable using the HydroFloat technology. As such, this new technology may offer a unique opportunity for increasing concentrator capacity by increasing the primary grind size needed for rougher / scavenger separations.”
Eriez Flotation Division installed its first FeedAirJet™ on a cleaner column at Capstone Gold’ s Cozamin concentrator in Zacatecas Mexico in late 2016. Nicknamed by the commissioning team as the“ Cavitador,” the FeedAirJet is a simple system for pre-aerating flotation feed streams. It is based on a proprietary configuration of Eriez’ s CavTube™, a sparging system that has been installed on more than 200 columns worldwide.
The CavTube works by inducing hydrodynamic cavitation in the feed slurry, which nucleates fine bubbles selectively on hydrophobic surfaces of the ore. The FeedAirJet turbo-charges the flotation process by starting particle collection before entering the flotation vessel. Results obtained by Capstone have confirmed this. According to Cozamin’ s Plant Manager Rafael Regino,“ The recovery of copper and silver were consistently increased an average of 0.8 % and 3 % respectively when the FeedAirJet was added.
Another impressive result was that recovery increased in all measured size classes. Based on these results, another FeedAirJet has been approved this April for our zinc column.”
According to Eriez representative Oscar Lopez:“ The FeedAirJet is a low risk, low capital way to improve flotation performance, and can be readily installed in existing plants. Five other plants in Mexico are evaluating this technology by installing the Cavitador to increase recovery and reduce the re-circulating load in the flotation cleaner stages. We believe this technology should also improve the performance of forced air and aspirated mechanical cells."
Flotation control
In the concentrator of the great Fresnillo silver mine( Mexico); each flotation cell has outlet valves via which the level of the foam at the top of the bath, and thus the concentration of metal, is controlled. In conventional applications, linear actuators with external displacement encoders and position controllers control the opening and closing of these dart valves. Festo says“ the clear disadvantage of conventional solutions is that the external sensors are extremely susceptible to malfunctions and breakdowns in the dusty and muddy environment. They also go out of adjustment easily and therefore need regular recalibration.”
This costs time and money, since the plant
40 2017
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