I.- Ping Chung, PhD, is a senior development engineer in the Technology and Commercial Development Group at
3.9 Summary
The variety of boiler burners described in this chapter is still a small part of the burners used in industrial boil- ers. The diversity of the equipment, fuels, geographical regions, and environmental standards makes the need to custom engineer the majority of combustion systems even when previously developed burner concepts are
Flame shape—2500°F/5000 ppm CO iso-surface 3.60e+03
3.42e+03 3.24e+03 3.06e+03 2.88e+03 2.70e+03 2.52e+03 2.34e+03 2.16e+03 1.98e+03 1.80e+03 1.62e+03 1.44e+03 1.26e+03 1.08e+03 9.00e+03 7.20e+03 5.40e+03 3.60e+02 1.80e+03 –6.66e+03
Contours of static temperature (°F) November 13, 2009
Fluent 6.3 (3d, pbns, spe, rtw)
Z X
Y
Figure 3.43
Conceptual design of low-CO flue-gas reheat system for refinery gas firing.
applied. The customization starts with selecting the most suitable burner type based on the available fuels, capac- ity demand, and environmental requirements. The next typical step is balancing between economics and perfor- mance. During that process, some compromises to the equipment specification can be made. In retrofit applica- tions, the variety of initial options with respect to what to reuse, refurbish, modify, or replace often includes both steps to jointly become an iterative optimization process.
In some cases, none of the prior-developed burner types are sufficiently suited for the application, prompting development of the new concepts.
From this perspective, the issues discussed in this chapter and also in Volume 2, Chapter 2, on combustion controls should help end users and boiler designers to better understand the issues and options that combus- tion engineers face when selecting and designing burn- ers and combustion systems. The days have long passed when a burner and a combustion system were simple and separate.
Changes in burner designs and system applications have been driven primarily by emissions since the pas- sage of the Clean Air Act in the early 1970s. Of necessity, burner designs have become more complex requiring a much deeper technical understanding of the system interactions and required controls.
NOx emissions are typically about 10 times lower, and CO emissions are on the order of 100 times lower than in the 1970s. Each application of a burner has to be evalu- ated based on the details of a particular furnace design.
The performance of boilers and especially their super- heaters and reheaters is heavily impacted by the utilized low-NOx techniques. This chapter discusses custom- engineered solutions. In many ways, every application of a burner is a custom-engineered solution. The only question will be the degree of custom engineering that
is required. Every burner type will perform differently in different furnaces. Each application has technical and economic limitations, especially retrofit projects.
References
1. S. C. Stultz and J. B. Kitto, Steam: Its Generation and Use, 40th edn., Babcock & Wilcox—A McDermott Company, Barberton, OH, 1992.
2. C. E. Baukal, The John Zink Combustion Handbook, John Zink Co LLC, CRC Press, Boca Raton, FL, 2001.
3. C. E. Baukal, V. Y. Gershtein, and X. Li, Computational Fluid Dynamics in Industrial Combustion, CRC Press, Boca Raton, FL, 2001.
4. C. E. Baukal, Industrial Combustion Testing, CRC Press, Boca Raton, FL, 2011.
5. J. M. Beer and N. A. Chigier, Combustion Aerodynamics, Robert E. Krigier Publishing Company, Malabar, FL, 1983.
6. A. K. Gupta, Swirl Flows, Abacus Press, Tunbridge Wells, U.K., 1984.
7. Y. B. Zeldovich, P. Y. Sadonikov, and D. A. Frank- Kamenetskii, Oxidation of Nitrogen in Combustion, Academy of Science, USSR, Institute of Chemical Physics, Moscow-Leningrad, Russia, 1947.
8. C. P. Fenimore, Formation of nitric oxide in pre- mixed hydrocarbon flames, in Thirteenth Symposium on Combustion, The Combustion Institute, Pittsburgh, PA, pp. 373–380, 1971.
9. W. Bartok, A. R. Crawford, H. J. Hall, E. H. Manny, and A. Skopp, Stationary sources and control of nitrogen oxide emissions, in Proceedings of the 2nd International Clean Air Congress, Academic Press, New York, pp. 80–90, 1971.
10. NOx controls for utility boilers, in Proceedings of the Electric Power Research Institute, July 7–9, Cambridge, MA, 1992.
Figure 3.44
Coen ProLine™ burner flames at low- (left) and high-fire (right) operation.
11. Turner, D. Al., R. L. Andrews, and C. W. Siegmund, Influence of combustion modifications and fuel nitrogen oxides emis- sion from fuel oil combustion, AIChE Symp. Ser., 68, 55, 1972.
12. A. H. Rawdon and S. A. Johnson, Application of NOx control technology to power boilers, in presented at the American Power Conference, May 10, 1973.
13. V. Lifshits and S. Drennan, Development of an Ultra Low NOx Burner with widened Stability Limits, American Flame Research Committee, Maui, Hawaii, 1998.
14. Ultra Low NOx Gas-Fired Burner with Air Preheat, CARB Contract Number 94–354, Final Report, Prepared for California Air Resources Board, California Environmental Protection Agency, November 2000.
15. V. Lifshits and S. Londerville, Vibration resistant low NOx burner, U.S. Patent # 5,310,337, issued May 10, 1994.
16. V. Lifshits and S. Londerville, Vibration resistant low NOx burner, U.S. Patent No. 5,460,512, issued October 24, 1995.
17. V. Lifshits, Development of a high performance versa- tile low NOx burner, in presented at AFRC International Symposium, Baltimore, MD, September 1996.
18. S. J. Bortz, Apparatus and method for reducing NOx, CO and hydrocarbon emissions when burning gas- eous fuels, U.S. Patent No. 5,407,347, issued April 18, 1995.
19. V. Lifshits, Low NOx fuel gas burner, U.S. Patent No:
6,027,330, issued February 22, 2000.
20. V. Lifshits, Energy efficient low NOx burner and method of operating same, U.S. Patent No: 7,422,427, issued September 9, 2008.
21. V. Lifshits, Energy efficient ultra low NOx burner with reduced flue gas recirculation, in P16th IFRF Members’
Conference Symposium, Boston, MA, June 2009.
22. D. Giovanni, Atomization and Swirler design tech- niques for improved NOx emissions, NOx Controls for Utility Boilers, in EPRI Meeting, Cambridge, MA, July 7–9, 1992.
23. V. Lifshits and G. Crovato, Experience with high effi- ciency, low emission burners to improve plant opera- tion, in Latin America Power’98, Conference Papers, Buenos Aires, Argentina, pp. 592–601, 1998.
4
Duct Burners
Peter F. Barry, Stephen L. Somers, and Steve Londerville
CONTENTS
4.1 Introduction ... 94 4.2 Applications ... 94 4.2.1 Cogeneration ... 94 4.2.2 Combined Cycle ... 94 4.2.3 Air Heating ... 94 4.2.4 Fume Incineration ... 95 4.2.5 Stack Gas Reheat ... 96 4.3 Burner Technology ... 96 4.3.1 In-Duct or Inline Configuration ... 96 4.3.2 Grid Configuration (Gas Firing) ... 96 4.3.3 Grid Configuration (Liquid Firing) ... 98 4.4 Fuels ... 99 4.4.1 Natural Gas ... 99 4.4.1.1 Refinery/Chemical Plant Fuels ... 99 4.4.1.2 Low Heating Value ... 100 4.4.1.3 Liquid Fuels ... 100 4.5 Combustion Air and Turbine Exhaust Gas ... 100 4.5.1 Temperature and Composition ... 100 4.5.2 Turbine Power Augmentation ... 101 4.5.3 Velocity and Distribution ... 101 4.5.4 Ambient Air Firing (Air-Only Systems and HRSG Backup) ... 101 4.5.5 Augmenting Air ... 102 4.5.6 Equipment Configuration and TEG/Combustion Airflow Straightening ... 102 4.6 Physical Modeling ... 103 4.6.1 CFD Modeling ... 103 4.6.1.1 Wing Geometry: Variations ... 104 4.7 Emissions ... 106 4.7.1 Visible Plumes ... 106 4.7.2 NOx and NO vs. NO2 ... 106 4.7.3 CO, UBHC, SOx, and Particulates ... 107 4.7.3.1 Carbon Monoxide... 107 4.7.3.2 UHCs ... 108 4.7.3.3 Sulfur Dioxide ... 108 4.7.3.4 PM ... 108 4.8 Maintenance ... 109 4.8.1 Accessories ... 109 4.8.1.1 Burner Management System ... 109 4.8.1.2 Fuel Train ...110 4.9 Design Guidelines and Codes ...110 4.9.1 NFPA 8506 (National Fire Protection Association) ...110 4.9.2 Factory Mutual (FM) ... 112 4.9.3 Underwriters Laboratories (UL) ... 112 4.9.4 American National Standards Institute (ANSI) B31.1 and B31.3 ... 112 4.9.5 Others ... 112 References ...115