Quantitative NMRI studies of transient washwater addition to rising foam

For the first time, NMR Imaging has been used to provide non-invasive quantitative data for transient washwater addition to rising foam. Washwater is routinely added to flotation froths to aid rejection of unwanted gangue material from the concentrate stream. The results show that washwater added to a mature foam (i.e., one that has attained its equilibrium liquid fraction) travels down the column, whereas washwater added to an immature foam travels up the column. This observation has important implications for flotation plant practise; washwater added too early at start-up will not aid gangue rejection but will instead merely lead to a wetter concentrate stream. This is explained theoretically in the context of the Hydrodynamic Theory of Rising Foam.