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Dilution Air Fans

Dilution Air Fan Applications

Power plants and other industrial operations that use combustion in furnaces, boilers, incinerators, and cooling systems must clean emissions before releasing them into the atmosphere. A dilution air fan, often paired with an SCR System, injects clean ambient air into the system, diluting the contaminated gas stream, enabling the plant to meet pollution control requirements mandated by the US Environmental Protection Agency (EPA).

The dilution air fan reduces the concentration of contaminating, usually Carbon Dioxide (CO2) or Nitrogen Oxide (NOx), in plant emissions by injecting fresh air into the airstream between the operations and exhaust. To do that, the application requires an industrial dilution air blower to introduce clean forced draft air into the system.

Primary Industries for Dilution Air

Industries that produce Volatile Organic Compounds (VOCs) or Hazardous Air Pollutants (HAPs) like NOx as byproducts of their operations require pollution control mechanisms. Coal and Gas Power Plants and any industrial operation that needs to exhaust dirty air often use Dilution Air for pollution control.

Dilution Air Blower Technology Selection & Specification

Because of the strict EPA emission requirements, pollution control provisions like Dilution Air Fans are essential to many industrial operations. That makes it critical to design the blowers for reliable performance and long life.

One important aspect of the specification is sizing for stability at all required operating points on the fan curve. Due to the variable flow requirements of this application, selecting a fan that operates too far to the left on the static pressure curve could put you at risk of operating in a surge condition, which often leads to premature failure. If you select the right fan, you’ll still be able to operate efficiently even with the extra room on the curve.

Fans Commonly Used to Provide Dilution Air

Fan Arrangements, Accessories, & Design

Fan Arrangements indicate how the motors mount to and drive the fans. For dilution air fans, we typically use direct-drive arrangements, usually an Arrangement 7 for very large blowers, otherwise Arrangement 4 or Arrangement 8.

Industrial Fan Designs Commonly Used for Calciner Rotary Kilns

Arrangement 4 – Belt Drive with an overhung impeller. The fan and motor mount separately to a unitary base.

Arrangement 4V / Top Mount – Direct Drive with an overhung impeller. The wheel also mounts directly on the motor shaft, but in a vertical position.

Arrangement 7 – Direct Drive with a center-hung impeller. The motor is directly coupled to the fan shaft with a bearing on either side of the fan wheel.

Arrangement 8 – Direct Drive with an overhung impeller. The fan shaft is directly coupled to the motor shaft with a flexible coupling.

When it comes to design and accessories, it’s all about protecting and optimizing operations, maintenance, and life of the fan and bearings. Although proximity to high-temperature systems might suggest the need for special materials of construction, the air that goes through the forced draft combustion air blower is room-temperature ambient air, so standard materials usually suffice.

Often, the amount of airflow is regulated by variable frequency drives and/or inlet dampers. Using these components together as a unit, the boiler’s efficiency increases, which results in better system reliability and increased energy savings.

Accessories & Design

When it comes to design and accessories, it’s all about protection, and optimizing operations, maintenance, and life of the fan and bearings. In industrial dilution air applications, we often recommend:

Featured Products

High Pressure Blowers

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Backward Inclined Fans

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Backward Curved Fans

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Case Studies

  • Dilution Air
  • Dilution Air Blowers for Refinery
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Talk with Our Application Engineers

If you feel overwhelmed by all this information, don’t despair! We have a team of application engineers who are happy to talk with you and select the best fan for your application. You can call 715-365-3267, email [email protected], or send us your information, and one of our engineers will connect with you.

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