Fluid Bed Dryers

Fluid bed dryers range from static fluid bed dryers to vibrated fluid bed systems. Capacity ranges from 100 kg/hr to in excess of 100 tph.

Operation:

Fluid bed drying uses a heated gas to lift and maintain the feed in a fluidized state. Air is introduced into a wind box or plenum via a forced draft fan and is distributed through a distributor plate of solid material via a perforated plate, nozzles, ceramic grid or other distribution mediums. The bed attains fluid-like properties flowing and mixing. The fluidization provides intimate contact between each material particle and the gas stream creating an extremely efficient transfer device. Products that have large particle size variations or high bulk densities can benefit a vibrating bed.

Specification:

  • Fluid Bed Dryers are designed for numerous processing applications but are ideally suited to materials with limited particle size distribution. Static fluid bed dryers operate best at PSDs lower than <2 mm but higher than 40micron.
  • Fluid Bed Dryers have limited moving parts (static) and are highly robust with a low maintenance demand.
  • 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 and liquid fuel burner systems.
  • All equipment is tailor designed to suit the processing requirements.
  • A unique aspect of a Drytech fluid bed dryer is our unique plenum plate design for high-temperature applications.
  • Materials processed: silica sand, chrome sands, heavy mineral sands, calcium propionate to name a few

Description

Feeding/discharge:

Manual, batch, automatic and continuous. Vibrators, screw feeders, rotary airlocks, double flap valves, gravity chutes

Feed Characteristics:

Liquids (only with appropriate technology), powders, granules, non-friable agglomerates. 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

Exposure:

Mostly Direct. Flow is through the bed. Indirect systems (contact) available for certain products.

Residence time:

Controllable. Residence time can be altered by varying the feed and discharge rates. Bed depth can be varied.

Extraction:

Normally induced. Forced draft fans required for fluidization. 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:

  • Very intimate contact with air/gas stream. Good mixing
  • Excellent transfer of energy
  • Gentle handling of product
  • Can be multi-zone units
  • Small real estate requirements
  • Low maintenance on static units
  • High-temperature operation - can be refractory lined.
  • The unit can serve as an agglomerator (Roll tumble agglomeration)
  • The unit can have an integral cooling section.

Limitations:

  • Loss of power will cause the product to build up in wind chamber (backflow)
  • May cause size reduction due to attrition and impact
  • High energy costs for fans and dust collection
  • Dynamic forces from vibrating motion can require substantial structures.