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Flash Dryers

Flash Dryers

High volume, availability and thermal efficiency covering small to extremely large throughputs.

Flash drying uses a heated gas to pneumatically convey the feed up a flash tube and into a primary air separation device; most commonly a cyclone. Air is induced or forced into the feed area through a hot gas generator where it entrains the feed and flashes off the moisture as it conveys. The product is fed into the throat of the feed area in a controlled fashion. The particles attain a velocity in the order of 80% of the conveying velocity. Secondary dust collection such as multiclones, bag houses, scrubbers and electrostatic precipitators are required for fine products.

Feeding / discharge:
Automatic and continuous. Vibrators, screw feeders, rotary airlocks, double flap valves, gravity chutes. Backmixing is most effective on sludge's. Feed introduced into airstream via venturi or use of disintegrator technology.

Feed Characteristics:
Slurries, pastes, and sludges (all with back mixing), friable filter cakes, powders, granules. Feed needs relatively consistent particle size. Very large particles present challenges. Low to high feed rates

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

Mostly Direct. Flow is cocurrent.

Residence time:
Extremely short (seconds). Residence time can be altered by increasing hold up times in cyclone.

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

Dust Collection:
Cyclones, bag houses, scrubbers, Electrostatic precipitators. Systems require significant dust collection since this is the product collection mechanism.

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

  • Very intimate contact with air/gas stream
  • Excellent transfer of energy
  • Ideal for heat sensitive, explosive or reactive products
  • Small real estate requirements
  • Flash tube is flexible, can be routed within plant constraints
  • Low maintenance - few moving parts
  • High temperature operation

  • Loss of power will cause product to fall into dryer base
  • May cause size reduction due to attrition and impact
  • High energy costs for fans and dust collection
  • Products displaying a high degree of bound moisture may not be suitable for this technology
  • May be susceptible to high wear if improperly accounted for

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