Adaptive Reference Tomography

T. L. Rodgers1 and A. Kowalski2

1School of Chemical Engineering and Analytical Science, University of Manchester, M60 1QD, UK

T.Rodgers@postgrad.ac.uk

2Unilever R & D Port Sunlight, Quarry Road East, Wirral, CH63 3JW, UK

ABSTRACT

One of the most important steps in producing good quality electrical resistance tomography data is the selection of the reference. The selection of an inappropriate reference can provide unusable or even misleading data. As electrical resistance tomography is used on more complex industrial processes the need for better references is a must. In certain situations, adaptive references must be used or useful information, e.g. mixing time or homogeneity, can be swamped by other changes in the system, e.g. temperature or liquid level change.

This paper first examines the effect of an incorrect static reference used in the image reconstruction taking agitation at different speeds of water and examining gas hold-up as examples. We show that an incorrect calculation of gas hold-up and gas distribution is obtained if an incorrect reference is taken. The paper then examines the more complex case of a level change during batch addition of water to a vessel. With a single reference artifacting is seen in the images that makes analysis almost impossible, while using a moving reference, the three-dimensional images can be reconstructed without level artifacting, allowing un-obstructed viewing of the mixing patterns. Finally, in-line mixing is examined with a temperature change in the mixer. With a single reference, the temperature change can affect the measured results, where as with a reference that adapts to the temperature the mixing can be analysed without problem.

Keywords Electrical Resistance Tomography, Adaptive References, Batch Addition, In-line Mixing