Fan(Induced Draft Fan):
Fan basically pulls out hot flue gas from the furnace of boiler via dust collector. It's located between dust precipitators(ESPs) and Chimney and also handles hot air/dust. The ID Fans serves two main functions:
Creates a negative pressure in the furnace as compared with the outer pressure. If the furnaces have leaks, a positive pressure in the furnaces will cause gases to leak out.Once the furnace flue gases get cool, it increases the flow velocity of the furnace.
FD Fan(Forced Draft Fan):
ID, FD Fan Manufacturer, FD Fan supplies the required amount of hot air into the furnace for smooth and uniform combustion of fuel and also handles air at normal temperatures. The capacity/power rating of Induced Draft Fan will be more than the Forced Draft Fan.