Determining independent control of dual-frother systems – Gas holdup, bubble size and water overflow rate

In flotation, frothers provide two main functions: control of pulp hydrodynamic properties and control of froth properties. In this paper dual-frother systems (blends) are investigated to determine combinations which provide independence over these two functions. Using a column on an air–water system, Sauter mean bubble diameter (D32) and gas holdup (Eg) were measured as the hydrodynamic properties and water superficial overflow rate (JwO) as the froth property. Blends of Alcohols with Polypropylene Glycols (PPGs) and Polyethylene Glycols (PEGs) were tested. Pre-mixed frother blends did not provide independence. The second approach was to use Alcohols as base and PPGs and PEGs as additives. Candidate blends were eliminated for a variety of reasons: with 1-Hexanol/TetraEG, JwO converged to roughly the same level as TetraEG concentration was increased; with 1-Butanol/PPG, D32 increased upon addition of PPG. The search was eventually successful: 1-Butanol/PEG blends gave independent control provided PEG had four or more EO groups. The increase in D32 noted with 1-Butanol/PPG blends was traced to partitioning of 1-Butanol to the froth which reduced 1-Butanol concentration below the critical coalescence concentration.