SCR — Selective Catalytic Reduction, Reduced NOx Emissions

SCR Boilers

Selective Catalytic Reduction (SCR)

Boiler SCR
Selective Catalytic Reduction (SCR) is a post-flue gas treatment capable of reducing NOx emissions from a wide variety of boiler systems. SCR is one of the most effective ways of reducing NOx in a flue gas stream with reductions up to 95%.

• Industry’s only totally integrated system
• Reduces NOx in excess of 95%, down to 2.5 ppm
• Ammonia transforms NOx into harmless nitrogen
• CFD modeling used to optimize every system
• Firetube, IWT, HRSG & retrofit boiler compatibility

Product Overview

SCR uses ammonia as a reducing agent, which is introduced into the flue gas stream. This mixture then comes in contact with a catalyst, selectively transforming the NOx into harmless nitrogen and water. With the addition of SCR, NOx emissions can be reduced down to 2.5 ppm. It’s a viable option to help meet current or future environmental regulations or your company’s sustainability goal.


Available NOx Reagents (Ammonia Sources)



R.F. MacDonald is the only manufacturer that can offer a complete SCR system integrated with your boiler. That means a single-source solution with a streamlined engineering process and better value, as well as a better system with more flexibility to meet the needs of your application.

Our partners at Cleaver-Brooks manufacture every major component of the boiler system, which enables us to provide an optimal solution for your needs. We use Computational Fluid Dynamics (CFD) and other advanced modeling software to ensure flawless design. Equipment integration allows precise adjustment to the boiler, burner, and controls, resulting in the most cost-effective and efficient SCR system.

R.F. MacDonald Co. receives U.S. Patent for Direct Urea Injection in SCR Systems

Boiler NOx Emissions Reduction with SCR

SCR process when incorporating Urea injection as a reductant, safely reducing NOx levels


  • Designed specifically for your application, with both installation-ready and freestanding stacks available
  • Three types of reduced agent systems are available: Anhydrous, Ammonia, Aqueous Ammonia and Urea
  • Single integrated control system operates the boiler, burner and SCR
  • Catalyst bed geometry is optimized and the highest quality corrugated catalyst is used with vanadium, titanium or tungsten oxides as active agents
  • A custom heater recovery system allows flue gas temperatures to be optimized, resulting in the most effective reduction of NOx emissions and increased efficiency
  • Completely integrated from the ammonia injection grid to the exhaust stack system, including all ladders, platforms and piping


  • Lower Emissions

RFMCO Services:

  • Cold Flow Modeling (CFM) or Computational Fluid Dynamics (CFD)
  • 3D Laser Scanning of boiler room/job site
  • 3D Modeling Design — Integration with 3D scans
  • Custom ammonia flow control unit, ammonia injection grid, and catalyst reactor housing
  • Custom controls integration
  • Emissions control for various fuels
  • Download: SJVAPCD Rules 4306 & 4320 Clear the Air Brochure