Flotation columns may benefit the oil sand industry by improving grade and recovery when processing middlings. Preliminary testing was conducted with a laboratory flotation column for two-phase systems over a bubble size range of 250 to 1100 μm. A correlation between exponent "m" in the drift flux equation, jgf = Ut α g (1 - αg ) m , and bubble Reynolds number was established, where j gf , Ut , αg , and "m" are the drift flux, terminal velocity of a bubble, gas volume fraction, and an exponent depending on flow conditions, respectively. The correlation is valid for a Reynolds number range of 5 to 70. After preliminary testing, the column was tested to ensure little difficulty when processing oil sands. Next, in-plant tests at Suncor Energy Inc. using a feed stream of oil sand middlings were completed to investigate the effects of the feed, recirculation, air, and wash water flow rates on bitumen recovery.