In thermal power plants and industrial boiler systems, maintaining proper airflow is one of the most important factors for safe and efficient operation. Draft fans play a crucial role in controlling air movement, supporting combustion, and removing exhaust gases. Among these, the ID Fan (Induced Draft Fan), FD Fan (Forced Draft Fan), and PA Fan (Primary Air Fan) are the three most essential components of the boiler draft system.
Refcon Engineering is a trusted name in manufacturing high-performance industrial fans designed for thermal power plants, boilers, and heavy industrial applications. In this detailed guide, we will explain the difference between ID Fan, PA Fan, and FD Fan, along with their functions in thermal power plants and boiler systems.
Also Read: FD Fan Vs ID Fan
Understanding the Boiler Draft System
Before discussing the differences, it is important to understand what a draft system is. In a boiler or thermal power plant, draft refers to the flow of air and flue gases through the system. Proper draft ensures:
- Efficient fuel combustion
- Safe removal of flue gases
- Controlled furnace pressure
- Improved energy efficiency
- Reduced pollution
To maintain this airflow, ID, FD, and PA fans work together in coordination.
ID Fan in Thermal Power Plant
The Induced Draft (ID) Fan plays a critical role in thermal power plants. It is responsible for removing flue gases generated during fuel combustion and discharging them through the chimney.
What is an ID Fan?
An ID fan creates negative pressure inside the furnace by drawing out hot gases after combustion. This negative pressure ensures that flue gases do not leak into the plant area and that combustion remains stable.
Location of ID Fan in Thermal Power Plant
In a thermal power plant, the ID fan is installed:
Boiler → Economizer → Air Preheater → Dust Collector/ESP → ID Fan → Chimney
It is positioned near the end of the flue gas path, just before the chimney.
Functions of ID Fan in Thermal Power Plant
- Removes flue gases from the boiler
- Maintains negative furnace pressure
- Controls draft balance
- Supports pollution control equipment like ESP
- Ensures safe discharge of exhaust gases
Without the ID fan in a thermal power plant, flue gases would accumulate inside the furnace, causing unsafe operating conditions.
Boiler ID Fan (ID Fan in Boiler)
The boiler ID fan is specifically designed to handle high-temperature flue gases generated during fuel combustion in boilers.
Role of ID Fan in Boiler
In boiler systems, maintaining proper draft is essential for stable combustion. The ID fan in boiler systems:
- Extracts hot gases from the furnace
- Prevents backflow of flue gases
- Helps maintain proper air-fuel balance
- Supports efficient heat transfer
Since boiler ID fans handle hot and dusty gases, they are manufactured using heavy-duty materials with wear-resistant linings.
Why ID Fan is Important in Boiler Operation?
- Maintains proper negative pressure inside the furnace
- Prevents smoke leakage
- Improves combustion efficiency
- Enhances safety
- Reduces environmental emissions
The ID fan in boiler applications must be carefully designed to handle temperature, dust load, and pressure variations.
FD Fan (Forced Draft Fan)
The Forced Draft (FD) Fan is responsible for supplying fresh air to the boiler for combustion.
What Does FD Fan Do?
Unlike the ID fan, which removes gases, the FD fan pushes atmospheric air into the furnace under positive pressure.
Location of FD Fan
The FD fan is installed at the air inlet side of the boiler, typically before the air preheater.
Functions of FD Fan
- Supplies combustion air
- Maintains proper oxygen levels
- Controls air-fuel ratio
- Supports stable flame
The FD fan ensures that sufficient oxygen is available for complete combustion of fuel.
FD Fan in Boiler
The Forced Draft (FD) Fan in a boiler is responsible for supplying fresh atmospheric air into the furnace to support fuel combustion. It creates positive pressure and ensures that sufficient oxygen is available for efficient and complete burning of fuel.
Main Functions of FD Fan in Boiler:
- Supplies combustion air
- Maintains proper air-fuel ratio
- Supports stable flame formation
- Improves boiler efficiency
The FD fan is installed at the air inlet side of the boiler and works together with the ID fan to maintain proper draft balance. A properly designed FD fan helps in smooth boiler operation, energy efficiency, and reduced emissions.
PA Fan (Primary Air Fan)
The Primary Air (PA) Fan is mainly used in coal-fired thermal power plants.
Role of PA Fan
The PA fan performs two major functions:
- Supplies primary air for combustion
- Transports pulverized coal from the mill to the burner
It plays a vital role in drying coal and maintaining a proper fuel-air mixture.
Location of PA Fan
The PA fan is located near the coal mill section in pulverized coal boiler systems.
Difference Beetween ID Fan, FD Fan and PA Fan
| Feature | ID Fan | FD Fan | PA Fan |
|---|---|---|---|
| Full Form | Induced Draft Fan | Forced Draft Fan | Primary Air Fan |
| Main Function | Removes flue gases | Supplies combustion air | Carries coal + air mixture |
| Pressure Type | Negative pressure | Positive pressure | Positive pressure |
| Location | Boiler outlet side | Boiler inlet side | Near coal mill |
| Application | Exhaust system | Air supply system | Coal-fired boilers |
How ID, FD, and PA Fans Work Together
In a thermal power plant:
- The FD fan supplies fresh air for combustion.
- The PA fan carries pulverized coal and supports primary combustion.
- The ID fan removes exhaust gases and maintains furnace draft.
Together, they create a balanced draft system essential for efficient boiler performance.
Importance of High-Quality Draft Fans
Industrial draft fans operate under extreme conditions such as:
- High temperatures
- Dust-laden gases
- Continuous operation
- Pressure variations
Therefore, selecting a reliable manufacturer is crucial. Refcon Engineering designs and manufactures robust ID fans in thermal power plants, boiler ID fans, FD fans, and PA fans with:
- Heavy-duty construction
- High efficiency impeller design
- Low vibration and noise levels
- Energy-efficient performance
- Long service life
Our fans are engineered to meet the demanding requirements of power plants and industrial boiler systems.
Conclusion
Understanding the difference between ID Fan, PA Fan, and FD Fan is essential for anyone involved in thermal power plant or boiler operations. While the FD fan supplies air and the PA fan handles fuel-air mixture, the ID fan in thermal power plants and boilers ensures safe removal of flue gases and maintains proper furnace pressure.
The ID fan in boiler systems plays a particularly critical role in maintaining negative draft and preventing gas leakage. Without it, safe and efficient combustion would not be possible.
For industries looking for reliable and high-performance draft fan solutions, Refcon Engineering offers advanced and customized systems designed for long-lasting and efficient operation.
If you are planning to install or upgrade an ID fan in thermal power plant applications or boiler ID fans, choosing a trusted manufacturer ensures better performance, safety, and energy efficiency for your plant.
