The purpose of spray drying is to produce powder or a granular product in ONE step by drying 'atomized' liquid feed in heated air or other gaseous medium. By atomizing the feed into fine droplets, a very large surface area per unit mass is generated with a very short path for heat and mass transfer. The heated air supplies latent heat of evaporation to the droplets and brings about rapid drying which in turn brings about rapid cooling of the drying gas. At the same time the particle temperature is kept low by adiabatic cooling. Drying can take place in a very short time, typically 5-20 seconds. Spray dried particles are usually spheroidal, which gives the product excellent flow characteristics. Size of the dried product particle depends on the size of the droplet from the atomizers. Different atomizers produce different particle size distribution and spray patterns. The drying air flow pattern must be carefully selected for optimum performance.