Buell dryer
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The Buell dryer is a multiple hearth direct heated industrial dryer (commonly known as a turbo dryer) that has modified for drying china clay. Its design is very similar to the Herreshoff Kiln, which is a type of calciner. The Buell dryer was first developed by English Clays Lovering Pochin & Co. Ltd for their china clay processing plants in Cornwall. The first Buell was installed in the old cooperage in Nanpean, and was the first operating mechanical dryer in the Cornish china clay industry, having started in 1945.
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 the tray, dropping it down onto the one below it. Gradually the material works its 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.
While the Buell dryer is now thought to be a relatively obsolete drying technology, a very similar dryer made by Wyssmont called the TURBO-DRYER is still widely used worldwide.
TURBO-DRYER is the registered trademark of the Wyssmont company, inc. in Fort Lee, NJ USA. it is usually used for a thermal processor consisting of a stack of rotating toroidal shelves with radial slots wrapped around a set of central fans an a vertical axis in a stationary housing.
While essentially like the Buell dryer it has many improvements over that dryer so that it is not considered an outdated dryer. It frequently out-performs other dryers like vacuum dryers, fluid bed dryers, rotary dryers, flash dryers, indirect contact dryers and belt dryers.
Wyssmont was the first company to do closed-circuit solvent-recovery drying and many of its installation are still used for this type of application.
Although most used with hot air drying it is frequently used for inert gas drying of metals and polymers. It is known for its gentle handling, uniform product, easy startup, low maintenance, low power and "turn it on and forget it" operation.