The process
Fluid bed and endless chain pressure dryers fire the tea with hot air from a heater and exhaust the moist air with leaf fluff through a dust collector. Hot air fan on the supply, exhaust fan on the outlet.
The gas
Warm, humid air through withering troughs and dryers with light leaf dust. Large volume at low pressure; the fan is cleaned often, so access matters.
Selection for this process
| Impeller | Coated aluminium or stainless steel impeller, stainless or coated casing |
| 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 60°C the gas density is close to 1.06 kg/m³, 88% 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 tea 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.