19th International Drying Symposium (IDS 2014) Lyon, France, August 24-27, 2014 CONTACT VACUUM DRYING OF FUNGAL BIOMASSES AND THERMO- SENSITIVE PRODUCTS L. Bennamoun 1 *, A. Léonard 2 1 University of New Brunswick, Department of Mechanical Engineering 15 Dineen Drive, Fredericton, E3B5A3, Canada 2 Department of Applied Chemistry, Laboratory of Chemical Engineering, University of Liège Batîment B6, Sart Tilman, Liège, 4000, Belgium *Corresponding author: Tel.:+1 506 447 3421, E-mail: lyes.bennamoun@unb.ca Abstract: The main objective of this work is to study the behaviour of different polysaccharide products obtained from industry in order to recover their dry matter using contact vacuum drying method. The drying kinetic shows that, during the process, the material passes by: adaptation phase, constant drying rate phase and falling drying rate phase. Temperature, impeller velocity and vacuum rate are determined as parameters influencing the process. The observation of the torque give useful information related to the form change. Mathematical modeling of the moisture is finally performed using semi- empirical pre-defined models. Determining of heat transfer coefficient is also performed. Keywords: Drying kinetic, polysaccharide, yeast, operating conditions, temperature profile INTRODUCTION Due to the particular aspect of the materials and the specific properties required in the final dried product, contact drying is the most practiced drying process for chemicals and pharmaceuticals [1-7] . According to the design used to perform this method, contact drying presents several advantages, such as [8-9] : - No pollution of the heat carrying medium - Steam and odour confinement - Low VOC (volatile components) concentration - Reduction of fire and explosion risks due to the low oxygen level In addition, commonly, contact drying is coupled with mechanical agitation using an impeller. This agitation allows renewing the contact surface between the material and the heated walls which will keep a high transfer exchanges. Adding vacuum to the process can be explored for specific thermo- sensitive products, as drying can be performed at relatively low temperatures [10] . In order to make a good design of drying systems with optimum energy efficiency; knowing the behavior of the material during application of the process, mathematical modeling and simulation play a crucial role. Accordingly, Sahni et al. [11] studied using simulation and continuum mechanics, the behavior of an agitated contact dryer and the solvent dried inside. They simulated the profiles of the different temperatures, solvent concentrations and velocities with determination of heat transfer parameters. Tarhan et al. [12] presented the performances of an industrial contact dryer during drying of peppermint. In order to determine the optimum drying conditions, several scenarios of operating conditions with determination of the energy consumption as well the quality of the final product were then determined. Based on the behavior of sewage sludge during agitated contact drying; it was possible for Arlabosse et al. [13] to design an energetically efficient paddle dryer dotted with a vertical agitator. The study was essentially done by exploring the data coming from the agitator, the evaporation rate and the heat flux density. Ferasse et al. [9] determined the variation of the heat transfer parameters for different operating drying conditions, during agitated contact drying of sludge. They explored the influence of the temperature of the contained, the velocity of the agitator and other specific parameters related to the design of the dryer, such as the distance between the agitator and the walls. In addition, Yan et al. [14] , Hippinen et al. [15] and Bennamoun et al. [10] studied the effect of adding vacuum or partial vacuum on agitated contact drying of different materials, such as yeast and sewage sludge. They found that in addition to the