Laboratory-Scale Analysis of Energy-Efficient Froth Flotation Rotor Design

Abstract

Froth Flotation is an industrial separation process commonly used in the primary enrichment of run-of-mine mineral material. Over the past 100 years, much of the process's development has come from empirical evolution, rather than fundamental understanding. While many of the governing sub-processes are still poorly understood, the primary influential factors lie within the chemical, equipment, and operational variables unique to each flotation system. This investigation focuses on the phenomenological investigation of the equipment variables, particularly the rotor design, at the laboratory scale.

During this study, several small-scale flotation systems were developed, including various rotor and stator designs, tank sizes, and flow conditions. Experimental techniques were also developed to identify operational performance in four criteria: power consumption, gas dispersion, operational robustness, and flotation kinetics. Evaluation of the various rotors was conducted in two campaigns: (1) an exploratory campaign which featured 14 rotors in limited operational conditions (2) a detailed campaign which featured three rotors in an exhaustive set of conditions.

The results show that different rotors exhibited varying degrees of performance when judged by the aforementioned performance criteria. In general, excessive fluid pumping leads to an increase range of stable operation at the expense of greater power consumption. However, this increased power consumption does not necessarily correspond to increased flotation performance, as the data generally confirms the linearly proportional relationship of flotation rate and bubble surface area flux. Consequently, enhanced flotation kinetics can be achieved by rotors which disperse high rates of gas while retaining a small bubble size.