Continuous flow fluid bed dryer

Details Continuous flow fluid bed dryer Continuous flow fluid bed dryer

1999-04-07

2001-02-20

Wilson, Pamela (Department: 3749)

Drying and gas or vapor contact with solids

Apparatus

Gravity flow type

C034S179000, C034S185000

Reexamination Certificate

active

06189234

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention pertains to the field of direct dryers for industrial and commercial use, and in particular to a continuous flow fluid bed dryer. Such dryers are typically used for the drying of delicate free flowing products such as certain grains. Such grains tend to suffer degradation in dryers having rapidly moving mechanical parts that interact with the product. The fluid bed dryer typically has a drum or housing with a plenum region beneath a product drying region and separated from it by a porous screen. Heated air is introduced into the plenum. Particulate matter to be dried is “fluidized”, that is it is suspended above the screen on the heated air rising through the screen. This produces a turbulent mixing action between the target product and the air resulting in the drying of the product without damage to it. The screen openings can be canopied to direct air flow and deter clogging of the screen openings. In such dryers the heated air flow is used both to dry the product and move it along the dryer to a discharge. The amount of air needed to fluidize the product is often greater that the amount of heated air needed to dry it. This results is wasted heat since the amount of heated air supplied is a function of the amount of air needed to fluidize the product.
SUMMARY OF THE INVENTION
The invention pertains to a continuous flow fluid bed dryer wherein portions of the bed are momentarily fluidized for drying purposes. The dryer includes a dryer housing having a dryer drum with a drying chamber, and a plenum section with a plenum chamber located beneath the drying chamber. Hot air is introduced into the plenum chamber. The lower part of the drying chamber is trough shaped with a curved bottom and relatively high side walls. A curved porous screen is located at the bottom of the drying chamber and permits hot air to be transferred from the plenum chamber to the drying chamber. A rotor shaft extends longitudinally through the drying chamber and carries a plurality of paddles. The shaft rotates slowly in the drying chamber to gently mix the product with the heated air and advance it downstream in the chamber. As each paddle sweeps across the screen it moves product away from the screen. This permits a momentary rush of air through the screen, locally fluidizing the product and promoting drying.


REFERENCES:
patent: 3808701 (1974-05-01), Bachmann
patent: 4589215 (1986-05-01), Iwasaki et al.
patent: 4608766 (1986-09-01), Kawai et al.
patent: 5144108 (1992-09-01), Reynolds et al.
patent: 5197205 (1993-03-01), Spada et al.
patent: 5869810 (1999-02-01), Reynolds et al.
Process Drying Practice,Cook & DuMont, 1991, McGraw Hill Inc., pp. 45-48 and 225-229.

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