A Complementary Study of Ultra-Fast Magnetic Resonance Imaging and Electrical Capacitance Tomography for the Scale-up of Gas-Solid Particulate Systems

The behaviour of multiphase particulate or granular systems (e.g. in fluidised beds and pneumatic conveyors) presents severe experimental problems because they are opaque, largely preventing the use of optical techniques. Also, inserting physical probes inevitably disturbs the system under investigation. Thus, it has been difficult to develop reliable scale up criteria or validate numerical simulations of these systems. We aim to validate and explore the limitations of measurement using two complementary, non-intrusive experimental techniques: Electrical Capacitance Tomography (ECT) and Magnetic Resonance Imaging (MRI), using the combined expertise of Ohio State University (ECT) and Cambridge (MRI). Particular regard will be paid to the applicability of these techniques in the validation of the predictions of Discrete Element Modelling (DEM) and in the development of scale-up criteria in gas-fluidised beds. This is timely, given recent developments in all three of these areas, particularly in the potential that ECT could have in the design of truly industrial-scale fluidised beds, provided it is properly validated.The experimental techniques considered here (MRI and ECT) are complementary in that their strengths lie in measuring different features of multi-phase granular systems. MR enables the bulk solids motion to be visualised, as well as the particle velocity profiles, in both the dense solids phase and the lean (bubble, jet, void) phase . Furthermore, it is possible to determine voidage profiles. We also propose to extend MR to be able to image gas directly for the first time in a multiphase system. ECT has a major advantage in that it does not have any serious restrictions regarding size, although equipment must be non-metallic. As with MRI, it is possible to determine the velocity of voids, i.e. bubbles and slugs, and voidage profiles. The velocity of the bulk solids cannot be determined, however. Importantly, there is an overlap in the variables which can be measured by either technique, the most important ones being voidage profiles and the rise velocity of voids. These measurements will be used for cross-validation of the two techniques.