Boiler Equipped with Primary Air Fan
The primary air fan is one of the three main types of fans in a
coal-fired power plant boiler, forming the core power equipment of
the boiler flue gas system together with the forced draft fan
(secondary air fan) and induced draft fan. Its main task is to
provide sufficient high-pressure primary air to the boiler
combustion system, undertaking key functions such as fuel delivery,
drying, sealing, and combustion support.
The primary air fan outlet air is divided into hot and cold paths:
hot primary air is heated by an air preheater and then sent to the
pulverizing system for drying and carrying pulverized coal; cold
primary air is used to regulate the temperature of the air-coal
mixture. After mixing, both types of air together transport the
pulverized coal to the furnace and provide oxygen for the initial
combustion stage. In circulating fluidized bed boilers, the primary
air also needs to be divided into multiple paths to achieve
functions such as bed fluidization, coal feeding, and sealing.
As of 2026, primary air fans mostly adopt a centrifugal design,
featuring high pressure head, large flow rate, and high stability,
and are widely used in thermal power generation, industrial
boilers, and incineration systems.
Working Principle
Centrifugal primary air fans mainly consist of an impeller, a
volute casing, a main shaft, bearing housings, and a coupling. When
the motor drives the impeller to rotate at high speed through the
coupling, the air between the blades is thrown towards the outer
edge of the impeller under centrifugal force, increasing its
kinetic and pressure energy. After the gas enters the volute
casing, the flow velocity decreases as the flow cross-section
gradually expands, and some of the kinetic energy is further
converted into static pressure energy. The air at the center of the
impeller is discharged, creating a certain degree of vacuum. Air
outside the intake port is continuously drawn in under atmospheric
pressure—as the impeller continues to rotate, air is continuously
drawn in and expelled, achieving continuous gas delivery.
Core Functions
- Pulverized Coal Heating and Drying: Hot primary air (approximately 300-350℃), heated by the air
preheater, is sent to the pulverizing system for preliminary
heating and drying of the pulverized coal, reducing its moisture
content and improving combustion efficiency.
- Pulverizing System Sealing: In some boilers, sealing air is directly drawn from the primary
air header and introduced into equipment such as the coal feeder,
effectively preventing pulverized coal leakage.
- Initial Fuel Combustion Support: After thorough mixing of pulverized coal and primary air in the
burner, the mixture is sent to the furnace, providing the necessary
oxygen for ignition and initial combustion.
Product Parameters
The following data represents partial performance specifications.
If you require specific parameters not listed, please contact us
for customized design service.
| Series no. | 6-06 series | Feature selection |
|---|
| Performance | Impeller diameter | 400-2800mm |
| Rotation speed | ≤3000rpm |
| Pressure range | 1706-8265Pa |
| Flow range | 2752-498507㎥/h |
|
| Structure | Blade type | Backward, Straight, Aerofoil type |
| Impeller support | SWSI, DWDI, Overhung type |
| Lubrication method | Oil bath, grease, lubrication oil station |
| Cooling method | Air cooling, Water cooling, Oil cooling |
| Driven mode | Direct driven, Coupling driven, Belt driven |
Installation & Manufacturing
Our manufacturing facility operates more than 300 sets of
processing and testing equipment with an annual production capacity
of 10,000 units. We maintain strict quality control throughout
production to ensure zero-error manufacturing and can meet
emergency delivery requirements to guarantee your project
timelines.
Packaging & Shipping
Contact Us
Contact Our Engineering Team for Custom Fan Solutions
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