Moisture Profiles Determination During Convective Drying Using X-ray Microtomography

A Léonard, S Blacher, P Marchot, J-P Pirard, M Crine

Laboratory of Chemical Engineering, Department of Applied Chemistry, University of Liège, Building B6c – Sart Tilman, 4000 Liège, Belgium, A.Leonard@ulg.ac.be

ABSTRACT

The knowledge of internal moisture profiles is an essential information to gain a better insight into complex mechanisms ruling drying of solid materials. The experimental determination of these moisture profiles is not an easy task. Most often, cheap and destructive techniques or sophisticated but expensive non destructive ones (NMR imaging) are used. This paper shows that X-ray microtomography, in combination with image analysis, provides an accurate, non destructive and easy to use technique to determine moisture profiles. Results reported concern drying of wastewater sludges whose management will become a real challenge in the years to come. An analysis of the development of moisture gradients at the sample external wall shows an influence of drying operating conditions. Gradients are smoother and appear later if air humidity increases or if air superficial velocity decreases.

Keywords Moisture profiles, convective drying, X-ray microtomography, sludges