Industrial dryers run the gamut from simple box-like units to complicated multi-phase systems. Here is a brief overview of fluid beds, media slurry and flash dryers.

Fluid bed processing has a number of applications -- the most common in process industries are drying and cooling, agglomeration and air classification. Conventional fluid beds are designed to dry or cool products without vibration. Fluid bed processing passes a gas directly through a bed of solid material via a perforated plate, nozzles or other fluidizing media, thereby lifting and mixing the solids. At a certain gas velocity (the fluidization velocity), the bed will behave much like a boiling liquid. Fluid beds can be multifunctional -- for example, drying, cooling, classifying and sterilizing -- in a single unit with batch or continuous operation.

Like conventional fluid beds, vibrating fluid beds function by passing a process gas directly through a bed of solids via a perforated plate or another type of fluidizing media. Vibration is added to aid in fluidization of more difficult to fluidize materials. Vibrating fluid beds are well suited for the following applications:
  • Processing material that has a wide particle size distribution. Vibration will help to discharge oversize particles that will not fluidize.

  • Processing sluggish or sticky materials.

  • Processing temperature-sensitive materials. A subfluidized condition can be created to produce plug flow and eliminate burning or discoloration.

  • Processing fragile materials. Low amplitude vibration and reduced fluidizing velocity create a gentle bed that causes less degradation.

The media slurry dryer is a cost-effective method in the production of super-fine powders from liquid-phase reaction or wet-grinding operations. High viscosity materials can be pumped directly into the unit without mixing or atomization. Other features include uniform distribution of slurry, high heat capacity coefficients, accelerated drying time for large capacities, and agglomeration is prevented (milling is not required).

Flash dryers are an inexpensive solution to drying powders and granular materials. The dryer can use higher gas temperatures than most other type dryers because the material retention time is very short. A unit is capable of processing high capacities in a relatively small amount of space. A flash dryer often is used as a predryer to expand production capacity on existing lines.

For more information dryers, contact Carrier Vibrating Equipment Inc., Louisville, Ky. Call (502) 969-3171 or visit