In fluidized-bed powder feeders, a bed of powder is continuously agitated by a fluidizing gas, in this case the carrier gas. The intent by design is to suspend a controlled volume of powder in a bed using a controlled volume of gas such that a sample of powder can be drawn off at a uniform rate. To accomplish this, the bed must be in continuous motion—that is, fluidized—and the volumes of gas and powder being removed must be continuously replaced.
Vibrators and/or gravity feed are used to assist and maintain flow from the hopper into the bed. The diagram shows how the powder-laden carrier gas is aspirated through openings in the carrier-gas tube, using the venturi effect created by gas flowing through the tube.
Volume 5A, Thermal Spray Technology ⇒ Thermal Spray Processes and Coatings ⇒ Process Control and Control Equipment ⇒ Material Feed
