The dual outlet device – Key to size-selective flotation

This paper discusses a new method to control particle size distribution in a flotation cell. As known from the literature, fine and coarse particles have different flotation rate constants, hydrodynamic behavior and require different reagent regimes. The device discussed allows separate processing of finer and coarser slurry by the extraction of a third stream, carrying finer slurry, from the flotation cell. By separate treatment of fine and coarse slurry operational conditions, flotation recovery for both can be optimized more efficiently. This dual outlet device (DOD) can be installed in a traditional flotation cell without a need for equipment replacement. Pilot plant tests were conducted in a single 5 m3 Outotec flotation cell and the results show that the DOD can extract a fine slurry from the flotation cell and that the DOD product represents 5–15% of the volume flow rate of the feed. In this paper, the first pilot scale tests of the DOD in a single flotation cell are discussed. The aim is to introduce the method and investigate the effect of different DOD configurations on the extracted DOD product. For more strict evaluation of the influence of the DOD on flotation recovery and froth stability (pilot) plant scale tests for a bank of cells and for the entire circuit will be conducted.