Boiler systems in Thermal Power plants use different types of Centrifugal Fans to supply air required for combustion, deliver fuel to the burners, circulate the gases for better heat transfer and remove exhaust gases. Based on the boiler size and airflow requirement, different types of fans are used with varied capabilities.
Two types of fans used in a boiler power plant are- A. Draft Fans and B. Other Process Fans.
- DRAFT FANS
Draft fans play an important role in thermal power plants because they are responsible for maintaining the flow of gases through the boiler system. Two types of Draft fans are used in the power plants, which are -1. Forced Draft fans and 2. Induced Draft Fans.
Forced Draft Fans: Forced Draft fans used in a power plant are centrifugal fans, utilizing radial airflow blading or variable pitch axial fans. Forced Draft Fans (FD) supply the air necessary for fuel combustion by pushing air through the combustion air supply system and into furnace. These fans are located at the inlet of boiler to push high pressure fresh air into combustion chamber, where it mixes with the fuel to produce positive pressure.
Induced Draft Fans: Induced Draft Fans (ID) exhaust all gaseous combustion products or flue gases from the boiler, through dust collector and delivers it to the chimney into the open atmosphere. Hence the ID fans are usually located at the outlet of the boiler system (between a dust collector and chimney). ID fan creates a negative pressure or suction to discharge the gases out after combustion from the furnace.
- OTHER PROCESS FANS:
Other Process fans used in a boiler power plant are -1. Primary Air fans and 2. Flue Gas Recirculation Fans
Primary Air Fans: Primary air fans or PA fans are high-pressure fans, used in the boiler power plants to supply the air for transportation of coal directly from the pulverizer to the furnace. PA fans give positive pressure upstream of the coal pulverize and handle relatively clean air.
Backward Curved Centrifugal Fan is the most common centrifugal fan used as a PA fan in a boiler power plant.
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