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AIR POLLUTION CONTROL Rich Reagent Injection (RRI) (brochure)
Process
Rich 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 in the lower furnace make RRI ideal for NOx reduction. The combustion process is then completed with the use of overfire air.
RRI technology is licensed from Reaction Engineering International and the Electric Power Research Institute. RRI is similar to Fuel Tech’s NOxOUT® Selective Non-Catalytic Reduction (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 <1. The RRI process results in little to no ammonia slip in comparison to SNCR. The reagent consumption with RRI is higher than SNCR, with a normalized stoichiometric ratio (NSR) of approximately 2 compared to a typical NSR of 1 for SNCR.
Results
Initial full-scale demonstrations of RRI in a cyclone-type furnace have been extremely effective. The first demonstration of RRI was completed in 2001 at Connectiv’s B.L. England Unit #1 (135MW). Connectiv used RRI in combination with Fuel Tech’s NOxOUT SNCR process to lower NOx as much as 60% beyond overfire alone at B.L. England station.
Tests completed in both 2002 and 2005 at AmerenUE’s Sioux Unit 1, a 550MW cyclone furnace, have demonstrated NOx reductions of over 30% and, when combined with SNCR, over 50%. RRI systems can be used alone or in combination with other Fuel Tech NOx reduction technologies, including NOxOUT SNCR and NOxOUT CASCADE®, the latter providing 60% - 80% NOx reduction.
Applications
In addition to the commercially available systems for cyclone fired boilers, Fuel Tech is currently evaluating RRI for use with various types of pulverized coal-fired boilers.
Summary
- Up to 40% NOx reduction with RRI alone
- No ammonia slip
- NOx reductions up to 55% when combined with the NOxOUT SNCR system
- Used in combination with SNCR or other technologies for higher NOx reduction