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 (D-32) and gas holdup (E-g) were measured as the hydrodynamic properties and water superficial overflow rate (J(wO)) 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, J(wO) converged to roughly the same level as TetraEG concentration was increased; with 1-Butanol/PPG, D-32 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 D-32 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. (C) 2012 Elsevier Ltd. All rights reserved.