X-ray microtomography: A new tool to follow soft material shrinkage during convective drying

X-ray microtomography is proposed as a new tool to investigate the shrinkage of soft material which occurs during convective drying. Reliable shrinkage curves are obtained with samples of wastewater treatment sludge. We develop a four zones model to describe the drying kinetics based of the experimental data provided by X-ray microtomography. The observation of the drying and shrinkage curves allows us to determine 3 critical water content values, which define different drying zones where extragranular, intragranular or mixed limitations prevail. When drying is externally controlled, the decrease of the drying rate observed during experiments can be related to the reduction of the external area of the sample. © 2014 International Society for Industrial Process Tomography.