Gravity Gold Recovery
Raw Water Usage and Cyanide Recovery
FLSmidth designed a new feed system incorporating E-duc feed dilution technology and our latest revolutionary thickener innovation - Evolute™ feedwell.
Alternate solutions considered
1. New thickener
A new thickener with higher side wall height and a longer mud residence time would enable cleaner overflow water with higher underflow density. This would enable improved gravity gold recovery and maximum water and cyanide recovery. This option would involve a significant capital expense.
2. Process water filtration plant
This option would enable the thickener to operate achieving maximum underflow density, water and cyanide recovery, and the solids removed from the dirty overflow in a filtration plant. Again, this option would involve a significant capital expense.
3. Upgrade the existing thickener
The lowest cost option would be to upgrade the feed system of the tails thickener to enable high underflow density (aiding water and cyanide recovery) and the production of clean overflow water for optimum gravity gold recovery.
Evolute™ feedwell technology
FLSmidth and Carpentaria Gold collaborated at the start of the project to establish measurable performance criteria to determine qualitative and quantitative benefits of the upgrade.
The criteria included:
- Overflow water clarity
- Knelson concentrator feed water pressure
- Knelson concentrator scheduled maintenance intervals
- Flocculant consumption
- Underflow density
- Cyanide recovery
- Raw water usage
- Scale inhibitor usage
The upgrade to the Evolute™ feedwell on the 22mØ tailings thickener at Carpentaria Gold completed in October 2013 brought about immediate improvements in thickener operation.
Process data from the site PI and laboratory data from grab samples have shown:
- The Knelson concentrator process water feed pressure stabilised, indicative of negligible capillary fouling. The result being the security of full plant availability ensuring gravity recovery of gold as well as a reduction in maintenance costs.
- Visibly significantly improved thickener overflow clarity
- Significantly improved solids settling rate, leading to a 40% reduction in flocculant
- Improved settling coupled with the reduction in overflow solids allowed for increased mud bed growth and underflow density
- Reduced pumping costs for tails dam water reclamation
- Reduced raw water intake
- Increased recovery of cyanide that would have been lost to tails
- Lower solids in the process water allowed for a ~35% reduction in scale inhibitor chemical