Selective Non-Catalytic Reduction (SNCR)

EES through our STEP Combustion group supplies Selective Non-Catalytic Reduction (SNCR) systems that reduce NOx by up to 40% on conventional boilers and up to 80% or more on fluidized bed boilers (C/BFB). STEP’s propriety high efficiency SNCR system utilizes urea or ammonia reagent which is injected into the post combustion flue gas stream to react with the NOx and form N₂ and H₂O. STEP’s Selective Non-Catalytic Reduction systems can use anhydrous ammonia, aqueous ammonia, or aqueous urea. SNCR NOx reduction systems can be applied to coal, biomass, fuel oil and gas fired units.

STEP’s SARIS™ Selective Non-Catalytic Reduction SNCR system STEP’s SARIS™ system uses a dual fluid design. The design uses air or steam for atomization and droplet size control. For cooling, a small volume of fluid is used thereby eliminating the need for costly and high maintenance retract equipment. STEP’s custom atomizer designs allow precise control of the reagent distribution and droplet size which maximizes coverage and residence time and reduces the number of injectors required (when compared to competitive systems). The dual fluid approach provides precise drop control in customizable spray patterns designed for each particular application. The STEP SARIS injector design is a significant improvement, over competitive technologies. Control options include feed forward or look up table control; alternatively, systems can use feedback control where NOx emissions are used to control ammonia injection rates.

Case Study 1	Case Study 2
350 MW x 2 20 Wall Fired Coal Burners High Sulfur Bituminous Coal 10 STEP SARIS Selective Non-Catalytic Reduction Injectors 47% NOx Reduction NH₃ Slip < 5 ppm	400 MW x 2 20 T-Fired Coal Burners Sub-Bituminous 35% Ash Coal 4 STEP SARIS Selective Non-Catalytic Reduction Injectors 39% NOx Reduction NH₃ Slip < 5 ppm

The Selective Non-Catalytic Reduction reaction occurs post-combustion, within a temperature range of approximately 1,600 to 2,100°F. The optimum temperature within that range is dependent on residence time and carbon monoxide concentration. Lower temperatures require longer residence times. Elevated carbon monoxide levels shift the temperature curve such that better efficiencies are achieved at lower temperatures.