A New Experimental Approach to Evaluate Coal Particles Floatability: Bubble-Particle Attachment and Detachment Kinetics.

Abstract

Coal floatability evaluation is of vital importance in the prediction of flotation results and the design of a flotation flowsheet. In this work, a new experimental approach based on bubble–particle attachment kinetics (BPAK) and bubble–particle detachment kinetics (BPDK) were proposed to evaluate the floatability of coal particles. During attachment and detachment processes, a variation of coating angles θ(t) for different density coal particles were measured and fitted to a first-order model. Modified attachment rate constant ka* and modified detachment rate constant kd* were used as yardsticks of floatability. For comparison, flotation kinetics, induction time, and contact angle measurements were also conducted. A consistent sequence of floatability was obtained as: −1.4 > 1.4–1.6 > +1.6 g/cm3. The modified flotation rate constant k* obtained in flotation kinetics was used as a yardstick to assess the accuracy of floatability evaluation methods. By individually fitting k* to parameters obtained in other tests, a simple and close linear relationship between k* and modified attachment rate constant ka* was established, rather than 1/kd* in BPDK tests, induction time tind, or (1 – cosα) in contact angle measurements. Consequently, ka* is thought to be a better criterion as k* could be quantitatively predicted by BPAK tests. Throughout this work, BPAK is an effective method to evaluate coal floatability.