Drying of Solids: Principles, Classification, and Selection of Dryers
Arun S. Mujumdar, A.S. Menon
Abstract
Drying commonly describes the process of thermally removing volatile substances to yield a solid product. Energy transfer as heat from the surrounding environment to the wet solid can occur as a result of convection, conduction, or radiation and in some cases as a result of a combination of these effects. Surface evaporation is controlled by the diffusion of vapor from the surface of the solid to the surrounding atmosphere through a thin film of air in contact with the surface. The moisture contained in a wet solid or liquid solution exerts a vapor pressure to an extent depending upon the nature of moisture, the nature of solid, and the temperature. The drying behavior of solids can be characterized by measuring the moisture content loss as a function of time. Convection is possibly the most common mode of drying particulate or sheet-form or pasty solids.