The process
Utility and large industrial boilers fire pulverised coal through mills and burners. The PA fan dries and conveys the coal from mill to burner, the FD fan supplies secondary air through the air heater, the ID fan draws the flue gas through the ESP to the stack, and seal air fans keep coal dust out of the mill and fan bearings. These are the largest fans in the plant.
The gas at the fan
After the ESP or bag filter the flue gas carries a light residual ash load. The ID fan handles large volume at moderate temperature, selected for efficiency with modest wear allowance.
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 140°C the gas density is close to 0.85 kg/m³, 71% 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. |
Cuts the noise from steam or gas expanding from high pressure to atmosphere at safety valve outlets, start-up vents and blow-down lines. Client-stated blade types for the Vent Silencer in general: Silencer.
Industries
Other fans in pulverised coal fired boilers
Vent 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.