Selective Catalytic Reduction

Centrifugal Fan Applications for Selective Catalytic Reduction Systems

Selective Catalytic Reduction Systems (SCR Systems), provide necessary pollution control for industrial operations like power plants that generate flue gas laden with Nitrogen Oxide (NOx) as a by-product of the combustion process in boilers, incinerators, and furnaces. This flue gas must be treated to bring down NOx levels before being released into the atmosphere. The process converts harmful nitrogen oxides into safe diatomic nitrogen and water using a reagent (typically ammonia or urea) and catalyst.

Industrial fans & blowers in Selective Catalytic Reduction Systems generate the flow and pressure required to pull a specific amount of gas from a point between the combustion unit and exhaust stack, through the SCR System for treatment and inject the treated air back into the main duct clean enough to exhaust safely within emission standards.

The US Environmental Protection Agency (EPA) tightly governs industrial emissions, and costs of non-compliance are high, not to mention unsafe. That means the stakes are high, and the fan is mission-critical. So much so that we often supply a redundant fan as a backup.

The unique requirements of each Selective Catalytic Reduction System will determine your process fan specifications. Scroll or hyperlink down to find Application Featured Products, Case Studies, and further application details as follows:

Primary Industries for Selective Catalytic Reduction Systems

Pollution control is required across many industries that produce Volatile Organic Compounds (VOCs) or Hazardous Air Pollutants (HAPs) like flue gas as byproducts of their operations. Common industries that employ selective catalytic reduction systems are Coal and Gas Power Plants and any industrial operation that uses combustion to generate steam in their process.

SCR System Fan Technology Selection & Specification

Because of the strict EPA emission requirements, selective catalytic reduction systems are core functions of many industrial operations, and the fan is at the heart of how it works. That means designing to ensure reliable performance and long life through custom engineering.

In selective catalytic reduction systems, the fan is situated downstream of the combustion process, so it’s handling gas at extreme temperatures sometimes exceeding 1000°F. That high temperature is the biggest challenge, requiring high tip speeds to overcome high static pressure and system resistance. A shrouded radial wheel is a frequent go-to for SCR, but there are several models that we use depending on the specific application.

Industrial Fan Designs Commonly Used for Selective Catalytic Reduction Systems

Arrangements, Accessories, & Design

Fan Arrangements indicate how the motors mount to and drive the fans. The Selective Catalytic Reduction System can use both direct drive and belt drive options, but the most common is direct-drive Arrangement 8. These are the arrangement options:

Arrangement 1 – Belt Drive with an overhung impeller. The fan and motor mount separately to a unitary base.

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

Accessories & Design

When it comes to design and accessories, it’s all about protecting and optimizing operations, maintenance, and life of the fan and bearings. In industrial selective catalytic reduction systems, we often recommend:

  • Housing Insulation to protect the bearings from the heat radiating off the fan housing
  • A Shaft Cooler (aka Heat Slinger) to dissipate heat from the fan or blower shaft
  • Increased internal clearances to allow for thermal expansion
  • Purge Shaft Seal helps prevent hot air from getting to the bearings through the shaft hole opening
  • Tunnel-style bearings instead of separate bearings to hold tight alignment and keep temperatures down at high speeds
  • Stainless Steel Shaft to provide a lower rate of thermal conductivity than carbon steel, protecting the bearings from the hot gas stream
  • Vibration, and temperature sensors to monitor bearing and fan health and prevent unplanned outages
  • Proper installation and maintenance to ensure safe startup and operations

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.

Content Related to Selective Catalytic Reduction Systems

Here are related posts and case studies that might be of interest as you think about your application.