J K NAIR & COMPANY
MACHINERY DIVISION - Ahmedabad 382445 INDIA

Rotary Atomizer           Nozzle Atomizer            Closed Loop Spray Drier     Sterile Spray Drier                              Fluidized Spray Drier    Applications The process involving conversion of fluid into fine droplets and exposing them to a hot drying media, so as to achieve defined dry particulate matter is spray drying. It is a widely used continuous industrial process which involves particle formation from feed fluid which may be in the form of solution, emulsion or pumpable suspension into either dry powder or granules. Spray drying involves following steps.

ATOMIZATION

Conversion of the feed into fine droplets is achieved by either pumping the feed under high pressure through an orifice or by spraying through a high speed rotating perforated disc. The former is known as Nozzle Atomization and is popularly used to produce coarse droplets resulting in large granular particles of dried products. The latter is known as Rotary Disc Atomization and produces fine droplets resulting in fine powder particles of dried products.

HOT AIR MIXING

Air, which is, normally the drying media used, is heated to a predefined temperature depending upon the characteristics of the feed fluid and dried product either an indirect hot air generator or a direct hot air generator. This hot air is brought in contact with the spray droplets in one of the following ways through the air distributor: Co-current-Air and particles move in the same direction. Counter-current-air and particles move in the opposite direction. Mixed flow - particles are subjected to co-current and counter-current phase. The thermal energy of the hot air is used for evaporation and the cooled air pneumatically conveys the dried particles in the system. The contact time of the hot air and the spray droplets is only a few seconds, during which drying is achieved and the air temperature drops instantaneously. The dried particle never reaches the drying air temperature. This enables efficient drying of heat sensitive materials without thermal decomposition.

POWDER SEPARATION

Dried powder is discharged continuously from the bottom of the drying chamber through rotary valve and the air containing fines is taken to either a cyclone separator or passed through a textile fabric in a bag filter to recover the fines. The air is further scrubbed in a high efficiency venturi scrubber before being exhausted out to the atmosphere. Special powder handling systems are used for industrial applications to either cool the dried powder or toe pneumatically convey the same to a product silo. These systems are tailor designed to suit the specific requirements and layouts. Spray dried is an ideal choice as it offers defined end product characteristics in terms of particle size, moisture content, bulk density and particle shape.