Selective Catalytic Reduction (SCR) Fans
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
Due to strict EPA emission requirements, selective catalytic reduction systems are core functions of many industrial operations, and the fan is at the heart of how these systems work.
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
- High-Pressure Radial Open (HPRM / HPRL)
- High-Pressure Radial Shrouded (HPSM / HPSL)
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