The commercially operating mechanical flotation cells have entered their first year of operation at Oceanagold’s Macraes gold mine in New Zealand in 2008. Peter Bourke and Alan Berzins from Outotec discuss the installation that involved the TankCell 300 flotation cells.
Macreas has flash flotation cells for sulphide recovery. The concentrate is treated on the pressure oxidation circuit. The key challenges of this circuit include:
1. Restricted throughput due to a lack of flotation capacity
2. Difficulty to operate with two flotation trains
3. Recovery linked to the poor performance of column cells was not optimal
4. Expense to operate and maintain
The circuit capacity was to be expanded simultaneously while returning to a single-flotation train operation. Previous testwork proved that TankCells would increase sulphide recovery by 2%.
Thus a plan was undertaken in which the two flotation trains would be combined by installing a new rougher-flotation stage having 3 x TC-300 cells. Each TankCell, with 300m3 volume, was fitted with the FrothMaster 2 froth imaging system and an overall control platform was supplied for management of air addition, froth speed and level in the new cells.
The circuit configuration was finalised in May 2007. In June 2007, Outotec began work on-site to prepare for the TC-300 cell installation. Works included civil and earthworks, significant upgrades to the electrical system on site and a detailed plan for integrating the cells into the existing circuit, including design of all pumping, piping additional flotation air blowers and the rerouting of existing slurry piping.
The TC-300 rougher-cell introduction achieved the project aims. The circuit is operating on a single-train basis with operator comments confirming the significant improvement in the ease of operation. The targeted 6mtpa-throughput has been demonstrated. Early plant metallurgical results indicate a 4% increase in sulphide recovery.
Further analysis on the performance of the new TC-300 cells is planned, including a full air distribution and bubble size survey, metallurgical surveys and ongoing analysis of operating costs. This analysis will help to improve the existing TankCells.