For many aluminum melting furnaces, natural gas is mixed with air. The ensuing heat from combustion is then used to melt the solid aluminum and heat the liquid metal. Of increasing concern to the industry are the more stringent regulations in regard to NOx emissions from these plants. The formation of NOx mainly depends on the concentration of nitrogen and the temperature of the gas. One problem that affects this formation that has not been adequately addressed is the variability of the local natural gas supply. Natural gas has molecular nitrogen as a portion of its composition. This percentage ranges from approximately one to seven percent of the total mass fraction. In addition, the aluminum industry is investigating methods to reduce NOx emissions. One method is to replace some of the combustion air with pure oxygen. This reduces the amount of nitrogen coming into the furnace, but also raises the combustion temperature which could promote NOx production. This paper details a systematic computational fluid dynamics study on how the variability of the nitrogen concentration coupled with the partial replacement of air with pure oxygen affects heat transfer and pollutant formation in an aluminum furnace. Trends will be discussed as will the ideal oxygen concentration for a given nitrogen mass fraction.

Volume Subject Area:
Power
Topics:
Aluminum, Emissions, Furnaces, Nitrogen, Nitrogen oxides, Oxygen, Combustion, Natural gas, Heat, Temperature, Aluminum industry, Computational fluid dynamics, Heat transfer, Liquid metals, Melting, Pollution, Regulations
1.
FLUENT Inc. FLUENT 6.2 User’s Guide, Lebanon, NH. 2003.
2.
M. D. D’Agostini. High-Efficiency, High Capacity, Low-Nox Aluminum Melting Using Oxygen-Enhanced Combustion. 2000.
3.
MATWEB http://www.matweb.com, consulted 12/14/05.
4.
S. R. Turns. An Introduction to Combustion: Concepts and Applications 2nd ed. McGraw Hill. New York, 1996.
5.
G. K. Batchelor. An introduction to fluid dynamics.Cambridge Univ press, Cambridge, England, 1967.
6.
D. L. Baulch et al. Evaluated Kinetic Data for Combustion Modelling. J. Physical and Chemical Reference Data, 21(3), 1992.
7.
R. W. Bilger and R. E. Beck. In 15th Symp. (Int’l.) on Combustion, page 541. The Combustion Institute, 1975.
8.
J. Blauvens, B. Smets, and J. Peters. In 16th Symp. (Int’l.) on Combustion. The Combustion Institute, 1977.
9.
W. L. Flower, R. K. Hanson, and C. H. Kruger. In 15th Symp. (Int’l.) on Combustion, page 823. The Combustion Institute, 1975.
10.
J. A. Miller, M. C. Branch, W. J. McLean, D. W. Chandler, M. D. Smooke, and R. J. Kee. In 20th Symp. (Int’l.) on Combustion, page 673. The Combustion Institute, 1985.
11.
M. Missaghi, M. Pourkashanian, A. Williams, and L. Yap. In Proceedings of American Flame Days Conference, USA, 1990.
12.
J. P. Monat, R. K. Hanson, and C. H. Kruger. In 17th Symp. (Int’l.) on Combustion, page 543. The Combustion Institute, 1979.
13.
N. Peters and S. Donnerhack. In 18th Symp. (Int’l.) on Combustion, page 33. The Combustion Institute, 1981.
This content is only available via PDF.
Copyright © 2006
 by ASME
You do not currently have access to this content.