Directly Heated Rotary Dryer
Direct heated Rotary Dryers, Commercial and Pilot Scale,
A directly heated rotary dryer can be arranged with a gas-fired or electrically heated air heater, or utilize hot gas from a heat exchanger or another source. The utilization of a heat exchanger allows the use of a heated gas such as air or nitrogen as the heat transfer media. They can be arranged for parallel flow or counter flow operation. That is the heated gas sweeps in the same direction or opposite direct relative to the material flow.
In a directly heated dryer, the heat transfer rate and process atmosphere composition/volume are dependent, therefore consideration must be given to the gas velocity to avoid entrainment, as well as compatibility of the process material with the drying gas composition.
A process designer needs to consider the implication of process off-gas volume. Process gas and the heat transfer media comingle which effect off-gas treatment equipment sizing.
Directly Heated Rotary Dryers from Thermal Processing Solutions are particularly suited to a variety of applications that:
Tolerate direct contact of the process material with the process gas used as a heating media.
Tolerate hot gas contact with process material, either at the feed end or product end depending on if arranged as parallel-flow or counter-flow
Tolerate a single point source of heat and limited temperature profile control from the feed end to the discharge end as contrasted with an Indirectly Heated Dryer that can be arranged with multiple heating zones.
Indirectly Heated Dryer
An indirectly heated rotary dryer is essentially the same arrangement as the indirectly heated calciner but is designed for operation at much lower temperatures. The indirectly heated dryer can be arranged with multiple heating zones and for parallel flow or counter flow operation. That is the process gas sweeps in the same direction or opposite direct relative to the material flow.
In an indirectly heated dryer, the heat transfer rate and process atmosphere composition/volume are independent, therefore the issue of process material entrainment is less of a consideration
A process designer needs to consider the beneficial effect of the process off-gas volume contrasted with a directly heated dryer relative to the reduced gas treatment equipment sizing.
Indirectly Heated Rotary Dryers from Thermal Processing Solutions are particularly suited to a variety of applications that:
Require isolation of the process material
Benefit from the temperature control of a multizone heating arrangement
Require control of sweep gas velocity relative to entrainment of fine process material
Benefit from relatively smaller off-gas treatment system requirements compared to directly heated dryer alternatives.