Buell dryer
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The Buell dryer (also known as the tray dryer, turbo dryer, or multi hearth dryer) is a multiple hearth direct heated dryer, commonly used in industries handling slurried minerals such as Kaolin which need to be dewatered before they can be shipped to the customer. It's design is very similar to the Herreshoff Kiln, which is a type of calciner commonly used in the Kaolin mining and charcoal manufacturing industries.
The dryer itself is composed of a large upright cylindrical chamber, inside of which are 25 to 30 layers of trays or 'hearths'. Hot air and gasses are distributed throughout the dryer by a series of fans and ducts. At the centre of the dryer is a rotating column, to which the trays are attached and positioned radially within the dryer. Material enters the top of the dryer and lands on one of the top trays. As the central column rotates, fixed arms push the material off of the tray, dropping it down onto the one below it. Gradually the material works it's way down through the dryer in this manner, and exits the bottom of the dryer with the assistance of fans.
Material to be dried usually enters the top of the dryer with a moisture content of around 18%, and exits as a product of around 10 to 8%. Generally these figures all depend on the dewatering processes employed before the material reaches the dryer. Commonly, the Buell dryer handles shredded filter press cakes from standard square plate filter presses.
The Buell dryer is now thought to be a relatively obsolete drying technology since the introduction of Fluid Bed dryers, Spray dryers, Pneumatic (or flash) dryers, and high pressure tube, plate, and filter presses. In many cases, even the much older alternative drying system to the Buell, the Rotary dryer, has been longer lived.
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