Spray Dryer

Additional Details

Spray drying is transformation of feed from a fluid state into dried particulate form by spraying the feed into a hot drying medium. It is a continuous particle-processing drying operation. The feed can be a solution, suspension, dispersion, emulsion or slip. The dried product can be in the form of powders, granules, or agglomerates depending upon the physical and chemical properties of the feed, the dryer design and final powder properties desired. 

Feed is finely atomized and is introduced in the drying chamber along with hot air. The mixture of atomized feed and hot air moves towards the air exhaust of drying chamber. The time taken by this mixture to travel up to air exhaust is called as residence time of drying. During this residence time, the feed droplets loose its moisture to the hot air and is converted into dry powder particles. Hot air absorbs this moisture, so its absolute humidity increases while its temperature is reduced. The feed droplets while loosing its moisture to hot air, remain at temperatures much below the hot air temperature and it is exposed to hot air for a very short time. Hence spray drying is essentially known as "Low Temperature Drying". The temperature of feed droplet is the wet bulb temperature at the prevailing relative humidity.