TYPES OF DESIGN
There are two basic Thermascrew® designs:
- Conveyor - Type consists of one or more slowly rotating hollow screws mounted in a jacketed pipe or trough.
- Agitated Vessel- Type consists of hollow screw rotors mounted in a jacketed vessel. Material circulates within the unit, agitated by the rotating screws and overflows with residence time determined by feed rate and hold up.
The Thermascrew® indirect drying system is made of carbon or stainless steel as well as other alloys. Body styles include a non-jacketed trough, a jacketed trough, a pipe trough with jacket and a trough with multiple screws.
Optional steam orifices along the trough permit direct as well as conductive heating, making the unit useful in live steam heating, sterilizing, cooking or blanching. Purge gas or air may be injected as well.
Enclosed models isolate the product from airborne contaminants (dust, fumes, water vapor or reactant gases) and eliminate toxic or expensive product dust losses.
Thermascrews® may operate in either a pressure or vacuum environment and can serve as reactors for mixing liquid or gas reactants with the product. Any gases produced during the process can be recovered.
Rotor styles include a hollow screw the same diameter as the trough and a hollow screw with a smaller diameter than the trough. With the first type, optional lifter bars - mounted between screw flights - improve agitation by tumbling the product. With the second style, continuous ribbons or lifter bars - mounted between the outer edge of the screw and flush with the inner surface of the trough - mix the product even more and require higher rotational rates, improving heat-transfer coefficients.
The Thermascrew® indirect drying systems are available in seven trough diameters from 8" to 29" and eight trough lengths from 4' to 30'.