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Show At moderately high flame temperatures, the L N V ™ burner has lower N O x emissions as compared to the EV burner. As the flame temperature drops due to lower air preheat, the extent of FGR or an increase in excess air levels, the performance of the EV burner improves. This reflects the fact that if ultra-low N O x emission levels are needed, premixed combustion may have an advantage over diffusion burner concepts. Furthermore, the combustion zone required for the premixed EV burner is less than that needed in diffusion burner systems. It is noteworthy that at 3 % excess 0 2 the lowest NOx concentrations reached for the EV and L N V ™ burners were 15 p p m at 300°F preheat and 20 p p m at ambient temperatures respectively. CONCLUSIONS Two low NOx burners based on premixed and diffusion combustion concepts were tested at ABB on an industrial scale. The experimental evaluation of these burners has shown that N O x levels below 20 p p m were achieved. The most important parameter which affected the N O x emissions with both burners was the adiabatic flame temperature. At moderately low FGR rates, the L N V ™ burner had lower N O x emissions than the EV burner. However, the EV premixed burner had the lowest niinirnurn emissions. The L N V ™ low N O x venturi burner is ABB's current, commercial, low N O x natural gas burner. ABB C-E Services, Inc. has completed the installation of the L N V burner on two industrial boilers: one a 56,000-lb/hr steam capacity boiler with a single burner register (which will operate with FGR and ambient air); and the other a 230,000-lb/hr, five-burner unit with preheated combustion air and no FGR. The Environmental (EV) burner is under further development for the U.S. market and will be commercially available in the near future. With these products, ABB is addressing the commercial market for low N O x combustion systems in both the low N O x and ultra-low N Ox arenas. REFERENCES 1. Sattelmayer, T. H., Felchlin, M. P., Haumann, J., Hellat, J., Styner, D., "Second Generation Low-Emission Combustors for ABB Gas Turbines: Burner Development and Tests at Atmospheric Pressure" A S M E 90-GT-162,1990. 2. Rini, M. J., Jenning, P. J., "Development of an Advanced High Efficiency Cost Combustor for Boiler Retrofit- Task 3: Demonstration Scale Testing at 50 x 106 Btu/hr,/ U.S. D O E Report, Contract DE-AC 2286PC90275,1989. 3. Sattelmayer, T., Knopfel, H. P., Marling, T., Peter, H., "Ultra Low NOx- Vormischverbrennung von Gas und Ol Kesseln mittlerer Leistung", presented at the VDI (German Flame Days), Germany, 1993. 13 IV-24 |