The process
An atmospheric fluidised bed boiler keeps a bed of sand and ash in suspension with a high pressure FD fan under the distributor plate, and the flue gas carries bed fines and fly ash to the ESP or bag filter. The FD fan is a pressure duty, the ID fan a volume duty with abrasive dust, and the PA fan feeds the fuel feeders where they are pneumatic.
The gas at the fan
Fluidised bed combustion carries bed material fines and fly ash in the flue gas. The dust is abrasive and the loading ahead of the collector is high, so the ID fan is placed after the dust collector wherever the layout allows.
Selection for this duty
| Construction | Absorptive annular design in mild steel; stainless steel where the gas is wet or corrosive |
| Density at the fan | At about 160°C the gas density is close to 0.81 kg/m³, 68% 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. |
An absorptive silencer at the fan inlet, outlet or in the duct, cutting fan noise with minimum pressure loss. Client-stated blade types for the Fan Silencer in general: Silencer.
Industries
Other fans in afbc boilers
Fan Silencer 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.