Résumé
Mechanical energy input during mixing is one of the key stages of the mixer agglomeration process. It allows the distribution of water over the powder, the formation and growth of agglomerates, and homogenization of the agglomerate properties. The objective of the present work is to determine the power consumed by the wet agglomeration process of a reactive granular material, in the specific case of agglomeration of durum wheat semolina under the conditions of couscous grain production. Our study attempts to investigate the effects of process conditions (i.e. blade rotation speed, mass load, and water addition level) on the distribution of the different energy costs consumed by the mixer during the wet agglomeration process. As a baseline, we first measured the energy consumption by the motor for no-load mixing. To evaluate the energy consumption to transport inert load, we measured the energy consumption by the motor after introduction of different masses of durum wheat semolina without adding water. Finally, we study the energy consumption of the agglomeration process during mixing after water addition. Results demonstrate that the energy specifically consumed for agglomeration process increases with water content, from 9% (at 22% water content) to 26.6% (at 42% water content). However, the energy necessary to form and structure the agglomerates only represent at the maximum one third of the total energy consumed by the equipment. (C) 2012 Elsevier BM. All rights reserved.