Fans and Air Pollution Control for Bagasse Fired Boilers

The process

A sugar mill boiler fires bagasse straight from the mill at around half moisture. The fuel bed needs a large volume of under-grate air from the FD fan and over-fire air from the SA fan, and the wet, fibrous fly ash leaving the furnace goes to a multiclone or wet scrubber before the ID fan. The season runs for months without a stop, so every fan on the boiler is sized for continuous hot running and for ash that builds up on the blades.

The gas

Flue gas from bagasse firing carries a heavy load of fibrous fly ash and unburnt char, with high moisture from the wet fuel. The ash is abrasive and tends to build up on blades, so the wheel is chosen to shed deposit and the blades carry wear protection.

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
Dilution Air Blower	Injects ambient air into a hot flue gas stream to bring it down to a temperature the downstream bag filter or fan can accept..	Backward curved

Industries

Related processes