Electrical resistance tomography for monitoring emulsions and foams

There are several techniques available for monitoring emulsions and foams. Early studies usually referred to global measurement of the volumes of the emulsion/foam and of the separated liquid versus time. However, it was soon understood that phase separation is not only a function of time but also of location. With regard to simplicity and fast response, electrical measurements offer a tempting alternative for determining the longitudinal phase distribution in emulsions/foams. A far more challenging application is electrical resistance tomography (ERT) which involves several non-intrusive sensors across a measuring volume to determine the distribution of the conducting regions inside an emulsion/foam from electrical signals taken from all possible views of the sensing electrodes. In particular, a 2-Dimensional ERT which uses ring electrodes (mounted around the circumference of vessels) at different axial positions to yield the instantaneous longitudinal phase distribution will be presented here. The ability of this technique for real time measurement of foam/emulsion destabilization and separation of the constituted phased is examined in the present work. The technique is applied separately in study of a particular foam and a particular emulsion. In both cases, the evolution of the phase distribution is registered in detail. In addition, in case of emulsion, appropriate theoretical tools allow the estimation of the dominant droplet sizes.