Bubble coalescence and its effect on dynamic foam stability

The size of bubbles generated using a single-hole sparger, a multi-hole sparger and a flotation cell were measured. While the size of bubbles generated from the single-hole sparger does not depend on frother concentration, the bubble size strongly depends on frother concentration when the multi-hole spargers, or flotation cell, are utilized. The bubble size ceases to depend on frother at the concentrations exceeding the value characteristic for each frother and referred to as the critical coalescence concentration (CCC). All the bubble size vs. frother concentration curves converge on a single curve. Aqueous solutions of the frothers that are characterized by low CCC values form foams quite stable under dynamic conditions. Since bubble coalescence can be inhibited by frother concentrations exceeding the CCC, sparging systems can be studied and compared only at frother concentrations that exceed CCC.