Development and application of an image analysis method for wide bubble size distributions

The wide bubble size distributions (<2 mm to >10 mm) generated by jetting spargers have taxed the McGill bubble size analyser methodology. A revised image processing protocol is proposed (“alternative” filter) which includes selecting bubbles on the basis of the holes (bright centres) characteristic of the bubble images in two-phase systems. This allowed for the inclusion of small and large bubbles, while excluding bubble clusters. For the jetting sparger case, the alternative filter produced more regular distributions than the prior (“standard” filter) procedure based primarily on shape factor. Standard and alternative filters gave essentially the same output for narrow distributions, those typical of mechanical cells. The alternative filter revealed trends in the response of a jetting sparger to frother dosage and gas rate formerly obscured by the standard filter.