Gas dispersion properties: bubble surface area flux and gas holdup

Bubble surface area flux has been related to flotation performance and advocated as a key “machine variable”. Analysis of available data suggests that bubble surface area flux (Sb) and gas holdup (εg) are related by Sb ∼ 5.5 εg. This was the case for flotation columns and mechanical cells, both laboratory and plant scale, over the approximate range Sb < 130s−1 and εg < 25%. A relationship is expected given their similar dependence on gas rate and bubble size (both increase as gas rate increases and bubble size decreases). Reasons that a relationship may be obscured, especially in full size units because of the difficulty in defining the overall Sb and εg, are discussed. The possibility to replace Sb by εg as the machine variable has the advantage that gas holdup is easier to measure.