What the fans do here
A boiler house runs on draft. The FD fan pushes combustion air through the air heater into the windbox, the PA fan carries pulverised fuel from the mill to the burners, and the ID fan pulls the flue gas through the economiser, air heater and dust collector to the stack. The ID fan sees the worst duty: hot gas, fly ash and a pressure that rises as the filter loads. Bag filters or multiclones sit ahead of it, and silencers on the FD inlet keep the boiler house within noise limits.
Applications in this industry
| Application | What it does | Type usually selected |
|---|---|---|
| ID Fan | Sits at the outlet of a boiler, kiln or furnace and draws the flue gas through the plant to the stack. It handles hot, dust-laden gas at large volume, so it is sized at the hot condition and checked at cold start. | Backward curved, backward inclined and radial tipped |
| FD Fan | Supplies combustion air to a boiler or furnace, pushing ambient air through the air heater and into the windbox against the furnace draft. Clean air, so the blade is chosen for efficiency. | Backward curved and backward inclined |
| PA Fan | Supplies the air that dries the pulverised fuel in the mill and carries it to the burners. Runs at higher pressure than the FD fan because it must overcome the mill and the fuel piping. | Backward curved and radial tipped |
| SA Fan | Supplies the secondary combustion air that completes burning above the grate or around the burner. On bagasse and biomass boilers it also carries the over-fire air that controls the fuel bed. | Backward curved and backward inclined |
| Combustion Air Blower | Feeds a burner with air at the pressure the burner register needs. Sized for the burner turndown range, and often fitted with an inlet silencer. | Backward curved and radial tipped |
| Seal Air Blower | Supplies clean air at a pressure above the mill or fan casing pressure to the shaft seals and bearing housings, so pulverised coal cannot enter. | Backward curved and radial |
| Dust Collector Fan | The fan behind a bag filter, cyclone or multiclone on a dust extraction system. Placed on the clean side where possible so the blade can be chosen for efficiency. | Backward inclined and radial tipped |
| Fan Silencer | An absorptive silencer at the fan inlet, outlet or in the duct, cutting fan noise with minimum pressure loss. | Silencer |
| Vent Silencer | Cuts the noise from steam or gas expanding from high pressure to atmosphere at safety valve outlets, start-up vents and blow-down lines. | Silencer |
Processes in this industry
Equipment supplied
Centrifugal Fans
0.3 to 120 m³/s, 25 to 3120 mmWC single stage. Six blade configurations, three drive arrangements.
Bag Filter
Fabric filters in polyester, polypropylene, Ryton and Nomex. Efficiency to 99.9% down to 5 micron.
Multiclone
Bank of small cyclones in one housing. To 90% down to 20 micron, with hopper and rotary air lock.
Silencer
Fan silencers for inlet, outlet and duct. Vent silencers for steam and gas blow-down.
Dampers
Butterfly, multi louver, inlet vane, diverter and guillotine dampers in MS and stainless steel.
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.