The process
Belt dryers circulate heated air through the product bed with recirculation fans in each zone and an exhaust fan removing the moist air. The recirculation fans are plug or axial fans running in warm, humid air.
The gas
Air saturated with moisture from drying, with condensation on any cool surface. Drainage, a shaft seal and a material that tolerates wet running are part of the specification.
Selection for this process
| Impeller | Steel or cast aluminium impeller; PAG is not used above its temperature limit |
| Form | Tube axial for low pressure; vane axial where the pressure or the downstream distribution calls for it; bifurcated where the motor must be out of hot or contaminated air |
| Density at the fan | At about 120°C the gas density is close to 0.90 kg/m³, 75% of standard air. Pressure developed and power drawn fall in the same ratio, so the selection is made at this density and the motor is checked at cold start. |
Types, construction and performance of the axial fans.
Industries
Fans in belt and tray dryers
Axial Fans in other processes
Information needed to select or quote
- Gas volume and temperature. Actual flow at the inlet, normal and upset temperature, moisture.
- Dust or pollutant. Inlet loading, particle size distribution, whether it is abrasive, sticky, hygroscopic or combustible; for gases, the species and concentration.
- Required outlet. The emission limit or clean gas concentration the unit must meet.
- Site. Available space and height, material of construction preferences, and how the collected material is to be discharged.