Dedert's Roto-Flash dryer can be described as an agitated flash dryer. The process results in a fine powder directly from the feed material, without the need to premix with already dried product. The air residence time is just a few seconds, making the dryer cost effective both in terms of investment and running costs.
The drying process accepts cakes, pastes, fluids and powders and produces a fine powder with a uniform moisture content and consistent particle size distribution. Additional benefits include:
- Compact single pass dryer
- No external back-mixing or product reintroduction
- Integrated internal feed agitation for gentle mechanical dispersion
- Inlet temperatures as high as 750 C.
Roto-Flash drying applications are most commonly found in the chemical industry, including materials such as:
- Organic or inorganic pigments
- Titanium dioxide
- Many others
The drying chamber is a vertical cylinder. It has an annular air inlet and an axially mounted rotor. Drying air from a supply fan enters the air heater, most often heated by a direct fired gas burner, and enters the hot air inlet plenum tangentially. This tangential inlet, together with the action of the rotor, causes a whirling gas flow inside the drying chamber.
The feed material is discharged from an upstream process device into the feed vat, which is mounted onto load cells for process control purposes. A low-speed agitator breaks up the cake to a uniform consistency and gently presses it down into a feed screw. As the feed material is extruded off the end of the screw and enters the drying chamber, it becomes coated with dried powder. The powder-coated lumps fall into the Roto-Flash chamber and are kept in motion by the rotor while disintegration takes place. When dry, the friable surface material is abraded off by a combination of particle attrition and the mechanical action of the rotor, resulting in a balanced agitated fluid bed, which contains all phases from raw material to finished product.