The process
Boilers firing wood chips, agricultural residue or briquettes see fuel that varies in moisture and ash from one delivery to the next. The fan set is sized for the worst fuel, with the ID fan handling fly ash that is fibrous and sometimes sticky, and the FD and SA fans giving enough margin to burn wet fuel.
The gas at the fan
Mixed biomass fuels give variable ash and moisture. The fan is sized for the worst fuel in the mix, with wear protection and deposit shedding as for bagasse.
Selection for this duty
| Blade form | Radial tipped with wear liners, or straight radial where the dust is coarse |
| Material of construction | Mild steel with replaceable wear liners on the blades and the scroll at the cut-off, with a casing drain for the moisture |
| Drive and bearings | Direct coupled or belt driven with a shaft cooling disc and bearings outside the casing |
| Also specified | Hard facing or liners on the blade pressure face; casing drain at the lowest point |
| Density at the fan | At about 170°C the gas density is close to 0.80 kg/m³, 66% 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. |
Injects ambient air into a hot flue gas stream to bring it down to a temperature the downstream bag filter or fan can accept. Client-stated blade types for the Dilution Air Blower in general: Backward curved.
Industries
Other fans in biomass fired boilers
ID FanFD FanSA FanPA FanCombustion Air BlowerSeal Air BlowerDust Collector FanBag Filter FanFan SilencerVent SilencerVentilation Fan
Dilution Air Blower in other processes
Bagasse Fired BoilersWaste Heat Recovery BoilersHot Air GeneratorsRotary Lime KilnsSponge Iron Rotary KilnsElectric Arc Furnace SteelmakingSteel Reheating FurnacesFerro Alloy Submerged Arc FurnacesGlass Melting FurnacesWaste IncineratorsBiomedical Waste IncineratorsCrematoriaDistillery Spent Wash Incineration BoilersLead Smelting and Battery Recycling
Information needed to select or quote
- Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
- Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
- Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
- Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.