In-Line Monitoring of Drying Kinetics of a Fixed Bed Using an Electrical Imaging Technique

Abstract

The main objective of this study is to determine the drying kinetics of a fixed bed composed of porous particles using the electrical capacitance tomography (ECT) technique. This technique is an imaging modality in which the permittivity distribution inside an object is computed using capacitive measurements from the boundary of the object and mathematical algorithms. An experimental convective drying device equipped with an electrical tomography system is built. An existing relationship between the average moisture content and the dielectric permittivity of the product is determined experimentally from a calibration of the moisture content during the drying process. The tomograms of normalized permittivity distribution are presented. As a result, the distribution of the moisture content of the packed bed is then determined. The drying kinetics of the silica gel is drawn, and the various stages of the drying process are identified. The thermal behavior during the drying process at different levels of the granular bed has been established. The results show the efficiency of electrical tomography technique. This technique can be used to find other parameters such as the evolution of the porosity of the medium during drying as well as other parameters.

Keywords:

• Drying kinetics
• Fixed bed
• Inverse problem
• Electrical capacitance tomography
• Electrical permittivity
• Silica gel