Effect of alcohol, organic acid and potassium chloride concentration on bubble size, bubble rise velocity and gas hold-up in bubble columns

The effect of alcohol, organic acid and potassium chloride concentration on bubble size, bubble stability, terminal bubble rise velocity and gas hold-up in bubble columns was investigated. The addition of alcohols and organic acids to the water reduced the bubble size and the bubble rise velocity significantly. These organic solutes also changed the coalescence behaviour of aqueous solutions drastically, from high coalescence behaviour of pure water to coalescence restrain of the various solutions.

The mechanism of the coalescence suppression behaviour of electrolytic solutions of potassium chloride is discussed on the basis of ionic forces between ions and water molecules. The gas hold-up for low potassium chloride concentration increased owing to the ions reinforcing the liquid film between bubbles against bubble coalescence. For high potassium chloride concentration and low superficial gas velocity, large but unstable bubbles formed at the gas distributor plate. Increasing the gas velocity causes these bubbles to break into many smaller bubbles, thus increasing the gas hold-up.