Performance Study of Spray Dryer Using Various Salt Solutions

Abstract

Spray drying is an essential unit operation for the manufacture of many products with specific powder properties. It is characterized by atomization of a solution or suspension into droplets, followed by subsequent drying of these droplets by evaporation of water or other solvents. Spray drying is used for the manufacture of many consumer and industrial products such as instant food products, laundry detergents, and pharmaceuticals. It is well suited to continuous production of dry solids in powder, granulate or agglomerate particle form from liquid feed-stocks. Spray drying starts with the atomization of a liquid feedstock into a spray of droplets. Next, the droplets are put in contact with hot air in a drying chamber. The sprays are produced by either rotary (wheel) or nozzle atomizers of different types. Evaporation of moisture from the droplets and formation of dry particles proceed under controlled temperature and airflow conditions. Powder is continuously discharged from the drying chamber and recovered from the exhaust gases using a cyclone or a bag filter. The whole process generally takes no more than a few seconds. Correct atomization and air distribution are the keys to the spray drying process, as both greatly influence the final powder structure and quality. Often, spray dryers are equipped with high-speed centrifugal atomizers ensuring sturdy and reliable operation. High-Pressure nozzle atomization is used especially for products where a rather coarse powder with narrow particle distribution and high bulk density is required. In the nozzle atomizer, fines are returned around one or more central nozzles in order to facilitate optimum agglomeration. Two-Fluid nozzle agglomeration is typically applied in small chambers allowing maximum flexibility in particle design and particle engineering for both super-fine and agglomerated particles.