The investigation of bubble column and foam processes using electrical capacitance tomography

Foams are important in a variety of industrial processes including mineral production processes such as froth flotation. A variety of techniques have been used for their study such as microscopy, photography, casting–templating techniques, optical tomography and diffusing wave spectroscopy. In many process situations the delicate nature of foams necessitates non-intrusive measurement. In this paper detailed work is reported on applying electrical capacitance tomography (ECT) to low water fraction foams (<0.05). Potential applications are illustrated and discussed, including a demonstration of the ability to distinguish polyhedral foam and annular foam flow by analysis of pixelated images. The use of a method for the identification of flow regimes, which are dependent on surfactant concentration in a bubble column, is reported.