Selective Catalytic Reduction

  • R SCR Open 02-FIVES


Reduction of NOx by urea or ammonia occurs naturally at 850-1100°C. Using a catalyst can make this reaction happen at lower temperatures and with a higher performance. Reducing NOx using ammonia within a catalyst is called SCR (Selective Catalytic Reduction).

An SCR at a cement plant must respect the following criterias:

  • Suitable for common dust rates (50-100 g/m3)
  • High reactivity
  • Mechanical and chemical stability
  • Low pressure drop

SCR can be integrated to the downcomer, at the exit of the preheater tower. Around 260 to 350°C this SCR uses the most common catalysts for a lower capex. Compressed air is used for cleaning.

Fives integrates the cement making process expertise with SCR to achieve the lowest NOx emissions.


  • Very high efficiency
  • Negligeable ammonia slip
  • Low compressed air consuption due to the high efficiency of preheater cyclones (< 50 mg/Nm3)
  • Lower Capex due to usage of common catalysts

If required, SCR can be integrated after the main filter. The choice of catalyst is then done with caution as well as respect of temperature requirements is carefully made.