Maximum gas velocity in column flotation

Flotation is a surface-based separation process whose rate depends on the availability of bubble surface. The flotation column operational parameter controlling the availability of bubble surface is the gas velocity which emerges as a key design and scale-up parameter. The optimum gas velocity for column flotation has been identified to be in the bubbly flow regime [1,2]. By using dimensional analysis, it is shown here that the maximum gas velocity for the existence of bubbly flow conditions in flotation columns is given by U_g,max = 0.11D_c^0.5. It is shown that all large diameter flotation columns are being operated in the bubbly flow regime but at gas velocities lower than 50% of the maximum predicted values.