Newmont Boddington’s ore may be described as a gold ore with a copper problem. The majority of revenue is derived from sale of gold contained in either a gold bearing copper concentrate or doré bars. The copper head grade is below what would typically be considered economic for a copper sulphide flotation circuit. Despite the low copper head grade, the sulphide flotation circuit contributes to increasing overall gold recovery (as some gold is encapsulated in sulphide minerals) and lowers the cyanide destruction costs following leaching by removing up to 80 per cent of the copper beforehand.
Producing a marketable gold bearing copper concentrate from copper head grades as low as 0.06 per cent Cu has necessitated a cleaner circuit, which includes concentrate regrinding and up to three stages of conventional cleaner flotation.
The levels of non-sulphide gangue in the copper concentrate needs to avoid exceedance of a concentration level at which penalties would apply to concentrate sales. The concentrate grade improvement project investigated a number of alternative methodologies to reduce the non-sulphide gangue entrainment. The project outcome was the installation of a cavitation tube flotation column with froth washing. The cavitation tube flotation column was installed in a cleaner scalper flotation duty with a number of alternative circuit configurations either retained or modified to maintain the flexibility of the circuit to treat a wide range of copper head grades. Reducing the non-sulphide gangue entrainment also reduced transportation and treatment costs through the lower mass of concentrate produced. This paper will outline the concentrate grade improvement project from identification through to benefits. The paper will also outline some unique design features that further improve the operability and maintainability of cavitation tube flotation columns with froth washing.