Effects of physical environment on induction time of air-bitumen attachment

Induction time is a key parameter in flotation. It is,defined as the time needed for attachment of an air bubble with particles or a layer of bitumen when they are in contact. It has been reported that induction time is a function of many physical parameters. However, no systematic experimental study of these parameters has been reported. A refined induction timer was built to investigate the effects of physical parameters on induction time. The induction time, measured by moving an air bubble toward and then away from a silica particle bed, was found to be affected by the initial gap between the air bubble and the particle bed, the displacement and size of the air bubble, and the velocities of the air bubble approach to and retraction from the particle bed. Air bubble-bitumen attachment in different solutions (de-ionized water, clear process water and process water containing 0.5% fine solids) with or without calcium ion addition was studied at different temperatures. The results showed that induction time decreased with increasing temperature. The induction time was lowest in de-ionized water and highest in process water containing 0.5% fine solids with 50 ppm calcium ions. (C) 2003 Elsevier Science B.V. All rights reserved.