Spray Dryers
Spray Dryers
Single process conversions of liquids into free-flowing granules as well as transforming product characteristics.
Specification:
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 airflow 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.
- Spray Dryers are designed for drying of slurries and liquids.
- Sprays Dryers can be configured in numerous ways from co-current to counter-current and the slurry or liquid can be introduced to the process via high pressure atomizing nozzles or high-speed wheel atomizers.
- Capacities range from 100 kg/hr to in excess of 30 tph. Moisture contents in excess of 90%.
- Materials of construction can range from painted mild steel, through to various grades of stainless steel to special alloys depending on the processing environments and conditions.
- Heat sources range from steam, thermic oil, electric, gas, liquid fuel burner systems and coal-fired fluid bed combustors.
- All equipment is tailor designed to suit the processing requirements.
- Materials processed: copper or nickel sulphide slurries, iron-based catalysts, pigments, milk, coffee creamer, coffee, washing soap detergents, caramel, cheeses, spirulina to name a few.
Feeding/discharge:
Automatic and continuous. Pressure nozzle, two fluid, and rotary atomizers. Depending on the atomizer type may require a 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, countercurrent 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
