Spray Dryers

Single process conversions of liquids into free-flowing granules as well as transforming product characteristics.

Operation:
Spray drying involves the atomization of feed to a spray of droplets which are contacted with hot air in a drying chamber. Sprays are produced by a rotary atomizer or pressure nozzle atomizers. Evaporation of moisture from the droplets and formation of dried particles proceed under controlled temperature and air flow conditions. There are various dryer configurations. It is possible to meet specified product characteristics (re-hydration, moisture content, particle size, bulk density) by selecting the correct technology and configuration of the dryer.

Feeding / discharge:
Automatic and continuous. Pressure nozzle, two fluid, and rotary atomizers. Depending on the atomizer type may require high pressure pump or low pressure pump.

Feed Characteristics:
Liquids, slurries, low viscosity pastes. Low to high feed rates

Heat Source:
Steam, electrical, coal, liquid fuels, or gas

Exposure:
Mostly Direct. Flow may be co-current, counter current or fountain.

Residence time:
Short residence times. Fine dispersion and low velocities allow effective drying. Residence time can be altered by varying the drying air velocities somewhat.

Extraction:
Normally induced. Systems can have combustion, forced and induced draft fans for operation.

Dust Collection:
Cyclones, baghouses, scrubbers, Electrostatic precipitators. Systems require dust collection.

Control:
PLC, infrequently solid state controllers. System controls on discharge temperature. Can modulate energy and feed.

Benefits:
Can control particle size
Very intimate contact with air/gas stream
Low maintenance - only one moving part (Rotary atomizers can present maintenance headaches)
Can be manufactured from various materials
One step drying - from liquid to solid
Offers unmatched product characteristics

Limitations:
Very energy intensive
High operating costs
May cause nozzles to wear
Costly insulation
Sticky products may build up in the walls of the dryer

 Click here to view our gallery of Spray Dryers.