APV Dryer Handbook - Umbc

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PROCESS DESCRIPTION
The Spin Flash dryer can be described as an agitated fluid bed. As shown in
Figure 23, the unit consists primarily of a drying chamber (9) which is a vertical
cylinder. At the base is an inverted conical bottom, an annular air inlet (7) and
an axially mounted rotor (8). The drying air enters the air heater (4), is typically
heated by a direct fired gas burner (5) and enters the hot air inlet plenum (6)
tangentially. This tangential inlet, together with the action of the rotor, causes
a turbulent whirling gas flow in the drying chamber.
The wet feed material, typically filter cake, is dropped into the feed vat (1) where
the low speed agitator (2) breaks up the cake to a uniform consistency and gently
presses it down into the feed screw (3). Both agitator and feed screw are
provided with variable speed drives.
In the case of a dilatent fluid feed, the agitated vat and screw would be replaced
with a positive displacement pump and several liquid injection ports.
As the feed material is extruded off the end of the screw into the drying chamber,
it becomes coated in dried powder. The powder coated lumps then fall into the
1
3
2
6
8
Figure 23. Standard Spin Flash dryer configuration
9
7
5
10
11
4
12