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Show EFFECT OF OPERATING PARAMETERS ON N O X PRODUCTION IN A FLAT GLASS FURNACE 9 The presence of soot increases flame radiation to the furnace walls and glass surface, causing the average exhaust gas temperature to decrease by 15%. The average radiative heat flux to the glass also increased. The average N O x concentration value at the exit decreased by more than 5 5 % while the N O x per pound of glass dropped from 29.4 to 12.1 lb/ton of glass. The presence of the lance slightly increases (7%) the average exhaust gas temperature. However, the increase in temperatures in the furnace cause by the reduction of nitrogen in the furnace is significant enough to increase the N O x formation by more than 9 5 % as well as from 12.1 to 23.8 lb/ton of glass. Although the presence of the lance may be viewed as a stage combustion approach, which should alleviate the N O x formation problem, the increase in gas temperature certainly offsets that benefit and the result in a significant increase in the N O x formation with the oxygen lance. Average radiative heat flux to the glass also decreased, indicating a decrease in the overall heat transfer efficiency in the furnace. No significant differences were observed in the average exhaust temperatures between the pure-oxygen and pre-heated- air cases. The average temperature was only slightly lower for the pure-oxygen case. The radiative heat flux to the glass was also slightly lower for that case although heat flux uniformity did not change appreciably. N O x formation increased as indicated by the average N O x concentration at the exit of the furnace; however, given the significant reduction in the volume flow in the exhaust due to the fact that the nitrogen flow has been removed, the amount of N O x formed per ton of glass is reduced by more than 70%. ACKNOWLEDGMENTS This work was funded in part by the U.S. Department of Energy under Cooperative Agreement DE-FC02-95CE41187. Mr. Ed Gallagher serves as technical monitor. R E F E R E N C ES Carvalho, M.G., 1983, Computer simulation of a glass furnace, Ph.D. Thesis, Imperial College of Science and Technology, London, U K. Carvalho, M.G., and Lockwood, F.C., 1985, Mathematical simulation of an end-port regenerative glass furnace, Proceedings of the Institute of Mechanical Engineering, Part C, Vol. 199, C2, pp. 113- 120. Webb, B.W., 1997, Measuring and modeling combustion in glass melting furnaces" Proceedings of Modeling for the Glass Industry Workshop, Alfred University, July. Carvalho M.G., Wang J., and Nogueira M., 1997, Numerical simulation of thermal phenomena and particulate emissions in an industrial glass melting furnace, Proceedings of Conference Fundamentals of Glass Science and Technology, pp. 416-421, Vaxjo, Sweden, June 9-12. FLUENT User's Guide, 1995, FLUENT, Inc. Hill, S. and Smoot, L.D, 1993, A comprehensive three-dimensional model for simulation of combustion systems: PCGC-3, Energy and Fuels, Vol. 7, 874-883. Launder, B.E., and Spalding, D.B., 1972, Lectures in mathematical models of turbulence, Academic Press, London, UK. Launder, B.E., and Spalding, D.B., 1973, The numerical computation of turbulent flows, Imperial College of Science and Technology, London, U K , NTIS N74-12066, January. Rodi, W., 1984, Turbulence models and their application in hydraulics, Delft, The Netherlands, IAHR. |
