The impact of circulating loads on flotation circuit performance

Many workers have observed an inverse relationship between final concentrate grade and valuable component recovery achieved by a flotation circuit, i.e. an increase in either grade or recovery may only be achieved at the expense of the other. The relationship is termed a "grade-recovery" curve and, in theory, limits the separation obtained by the circuit. However, circuit surveys in a nickel concentrator indicate that the operating "grade-recovery" curve of a circuit is not only determined by the nature of the ore and the circuit operating conditions, but also by the circuit design, particularly in terms of stage capacities. The surveys show that different capacity circuits can produce different operating curves for the same ore, and that capacity reallocation between stages has the potential to improve both grade and recovery. In particular, the relationship between circuit design and operating curve position is shown to be a function of the circulating loads generated by the circuit design, balancing the beneficial effects of recycling material against the proportion of plant capacity consumed by recycling.