Bubble spargers in column flotation: Adaptation to precipitate flotation

Abstract

The limiting factor for metal-organic precipitate flotation in a column is the level of aggregate stability under the turbulence created by the rising bubbles. The hydrodynamic conditions in a 75 mm diameter pilot column were optimised by using different bubble spargers (Microcel, Flotaire, Imox) and by varying the gas flow rate into the bubble sparger, feed flow rate in the column, type and concentration of frother and recirculating pump flow rate. With the bubble spargers used, the average bubble diameter ranges from 0.30 and 1.10 mm, with up to 25% gas hold-up. The parameters influencing average bubble diameter are the superficial gas velocity and the recirculating pump flow rate. For optimal concentrations (10 to 20 mg/1), the type of frother has a negligible role. Strong interaction occurs between superficial gas and feed velocities and recirculating pump flow rate for bubble size control. The optimum operating conditions must accordingly be maintained to prevent carryover of small bubbles into the recirculating pump or the purified solution. An example of the Mo precipitate flotation confirms the assumption made for the effect of bubble size and dissipation energy on the separation results. reserved.