Coarse chalcopyrite recovery in a universal froth flotation machine

A new froth flotation machine has been developed, known as the NovaCell, which can recover mineral particles over a wide particle size range, from the lower limit of flotation, to an upper limit which depends on the liberation characteristics of the ore. In a single device, the collection of the fines and the coarse particles takes place in separate environments. The finest particles are contacted with bubbles in a high-shear aerator, while the coarse particles are captured by bubbles in the gentle environment in a fluidised bed. In this paper, the flotation of a porphyry copper ore in the NovaCell is described. The head grade was 1.0% Cu, and the copper mineral was freed from encapsulation at a relatively coarse size. The initial grind size was 600 mu m. Tests were conducted in a laboratory unit, in both batch and continuous modes, using a conventional reagent suite. The data were analysed, and rate constants were established on a size-by-size basis. The rate constants for the batch and continuous modes were consistent. They were used to predict the performance of a bank of similar cells in series. It was found that with four rougher NovaCells in series, and a cleaner circuit, it would be possible to obtain copper recoveries above 99%. Approximately 80% of the feed is rejected as coarse gangue particles from the roughers, thereby reducing the load on the secondary mills preparatory to the cleaner circuit. The savings in operating costs of grinding energy and media, are estimated to be 40% approximately. The NovaCell delivers two tailings streams, one of which has been de-slimed in the fluidised bed. It can be drawn from the Cell at a high percent solids, and is suitable for dry stacking without further dewatering. The test program uncovered a number of interesting features relating to the distribution of copper in the feed on a sizeby-size basis, and to the maximum recovery at infinite residence time as a function of particle size, which will be described.