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Rich Reagent Injection (RRI)

APC icon green webRich Reagent Injection (RRI)


SNCRRRI Fuel TechRich Reagent Injection (RRI) is the process of adding NOx reducing agents in a staged lower furnace to reduce the formation of NOx. This is accomplished by injecting urea into the fuel-rich region of a furnace, where the reducing conditions and low oxygen levels in the lower furnace make RRI ideal for NOx reduction. The combustion process is then completed with the use of over-fire air.

RRI technology is licensed through Reaction Engineering International and the Electric Power Research Institute. RRI is similar to Fuel Tech’s NOxOUT® SNCR process, which involves the injection of urea reagent at temperatures between 1700° and 2100°F. However, in the RRI process, reagent injection occurs at significantly higher gas temperatures within the combustion zone of the lower furnace (2400°-3100°F). The flue gas stoichiometric ratio (SR) in the lower furnace will be fuel rich, with the SR less than 1. The RRI process results in little to no ammonia slip in comparison to SNCR. RRI can require up to two times the amount of reagent when compared to an SNCR system, but is a very effective NOx reduction solution on cyclone fired boilers. 

  • Urea Injection in Lower Furnace on Cyclone-Fired Boilers
  • High Injection Rates
  • Minimal to no Ammonia Slip
  • 25% - 40% NOx Reduction
  • Up to 60% NOx Reduction when Combined with SNCR

Fuel Tech Experience

Fifteen commercial installations are in operation on cyclone fired boilers with results that have exceeded commercial performance.