Flotation experiments were carried out in a 76-mm- (3-in.-) diam, 3.55-m- (11.65-ft-) high column equipped with a Mott porous sparger. The variables studied included coal type, particle size, airflow rate and frother type. The column throughput was found to be a function of the airflow rate, frother type and feed size, and it was correlated to the Froude number. The Froude number exponent was found to be a function of frother type and feed size, but it was independent of the froth phase gas hold-up over the range 0.43 to 0.65. MIBC was determined to be a better frother for coal flotation than F-579. For a given frother, the gas velocity exponent for the coarse (70 x 100-mesh) feed was approximately one-half that of the fine (−100-mesh) feed. The use of wash water was also found to increase the dependence of the column carrying capacity on the gas velocity.