Theoretical Analysis of the Wall Deposition of Particles in Spray Dryers

Abstract

A spray drying is an important process in food, healthcare and pharmaceutical industries. However, spray dryers normally face a difficulty in operation when some particles with high moisture content (stickiness) have collected contacts with the metal surface of a dryer chamber, which is called a wall deposition problem. In this study, a computational fluid dynamic model of the spray dryer is developed based on momentum, mass and heat equations of the fluid and solid phases and employed to analyze an effect of the addition of a drying agent material on the fluid flow pattern within the spray dryer and the percentage and position of particle deposition. The wall deposition of particles is predicted by considering glass transition temperatures using the sticky-point concept. The feed solution of anthocyanin using maltodextrins as the drying agent material is considered. The simulation results indicate that most particles are deposited on the conical wall more than cylindrical wall. Use of maltodextrin with a higher dextrose equivalent (DE) value lowers the glass transition temperature of particle, causing the particles attached on the wall.