Fans and Air Pollution Control for Pulverised Coal Fired Boilers

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

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.

Fans in this process

Duty	What it does here	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.	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.	Backward curved and backward inclined
SA Fan	Supplies the secondary combustion air that completes burning above the grate or around the burner.	Backward curved and backward inclined
PA Fan	Supplies the air that dries the pulverised fuel in the mill and carries it to the burners.	Backward curved and radial tipped
Combustion Air Blower	Feeds a burner with air at the pressure the burner register needs.	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.	Backward inclined and radial tipped
Bag Filter Fan	Pulls the process gas through the filter bags and discharges the cleaned gas to the stack.	Backward curved 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
Ventilation Fan	Moves air through a plant or building for fresh air supply, heat removal and fume dilution where the system is ducted.	Backward inclined and forward curved
Coal Mill Fan	Draws hot gas through the coal mill to dry and convey the pulverised coal to the burner or the fine coal bin.	Backward curved and radial tipped

Industries

Related processes