A Study of NO{sub x} Reduction by Fuel Injection Recirculation

Technical Report · Thu Aug 01 04:00:00 EDT 1996

DOI:https://doi.org/10.2172/6599· OSTI ID:6599

Feese, J J ^[1]; Turns, S R

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1. Albuquerque Operations Office

Flue-gas recirculation (FGR) is a well-known method used to control oxides of nitrogen (NO{sub X}) in industrial burner applications. Recent small- and large-scale experiments in natural-gas fired boilers have shown that introducing the recirculated flue gases with the fuel results in a much greater reduction in NO{sub X}, per unit mass of gas recirculated, in comparison to introducing the flue gases with the combustion air. That fuel injection recirculation (FIR) is more effective than windbox FGR is quite remarkable. At present, however, there is no definitive understanding of why FIR is more effective than conventional FGR. The objective of the present investigation is to ascertain whether or not chemical and/or molecular transport effects alone can explain the differences in NO{sub X} reduction observed between FIR and FGR by studying laminar diffusion flames. The purpose of studying laminar flames is to isolate chemical effects from the effects of turbulent mixing and heat transfer, which are inherent in practical boilers. Numerical simulations of H{sub 2}-air and CH{sub 4}-air counterflow diffusion flames using full kinetics were performed and NO{sub X} emission indices calculated for various conditions. Studies were conducted in which a N{sub 2} diluent was added either on the fuel- or air-side of the flame for conditions of either fixed initial velocities or fixed fuel mass flux. Results from these simulation studies indicate that a major factor in diluent effectiveness is the differential effect on flame zone residence times associated with fuel-side verses air-side dilution. Simulations in which flow velocities were fixed as diluent was added either to the air or fuel stream showed lower NO{sub X} emissions for air-side dilution; however, if instead, fuel mass fluxes were fixed as diluent was added, which results in an increase in the velocity of the streams, fuel-side dilution was more effective. These results were independent of whether H{sub 2} or Ch{sub 4} was used as the fuel.

• Research Organization: Pennsylvania State University, University Park, PA (US)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EE) (US)
• DOE Contract Number: FG04-95AL87310
• OSTI ID: 6599
• Report Number(s): DOE/AL/87310-3
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
33 ADVANCED PROPULSION SYSTEMS
BURNERS
FLUE GAS
FUEL INJECTION SYSTEMS
HEAT TRANSFER
NATURAL GAS