Author(s)

C. Rautenbach, M. C. Melaaen & B. M. Halvorsen

Abstract

Electrical Capacitance Tomography (ECT) has become a useful measurement tool in process technology applications, especially in fluidized bed research. The ECT system is neither intrusive nor invasive which make the system practically viable for monitoring the internal flow behaviour in a fluidized bed. The sensor is placed on the outside of the non-conductive experimental reactor thus making implementation very convenient. ECT also presents user friendly equipment that is safe and easy to use compared to some of the other tomographic modalities currently available. There has been postulated that the insertion of fines into a powderwill give more uniform flow behaviour in a fluidized bed. Smaller and more evenly distributed bubbles are observed. These conditions lead to better mixing of gas and solids in a fluidized bed and thus improving the reactions in the reactor. These phenomena have been investigated in the present study using ECT and a reconstruction program developed in the present study. This reconstruction program created three dimensional images of the fluidized bed reactor under consideration. The reconstructions allow the user to get a three dimensional visual image of the flow behaviour inside the experimental reactor without disturbing the flow. Bubbleand bed characteristics of several powders with different percentages of fines were investigated. The volume, location and shape of individual bubbles were studied and thus the average bubble size, volume and frequency of a particular experimental set up was calculated. These quantities are of great importance for numerous industrial applications. Applications of these results are in almost all fields involving fluidization. The research is part of ongoing global research in optimizing and understanding fluidized beds better.

Keywords

fluidization, ECT, fines, bubble characteristics