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Show 5 4 ~ 0 3 N 0 ~ 0 X 2 0 z ~ a.. e:- O) 0 ...J 0 -1 -7 -5 -3 Log (XNO) FIGURE 12. CONVERSION OF MOLE FRACTION TO PPM NO (0% OXYGEN, DRY BASIS) -1 the increase in the predicted NO. The estimated values in Table 3 further show t~e importance of the need to accurately determine the peak temperatures. In both runs 2 and 6 the theoretical flame temperature with 25% enriched air is 4200°F and the peak temperature was assumed to be 2960°F for both runs 2 and 6. However, the furnace temperature in 2 is only 1457°F as compared to 1800°F in run 6. Therefore, the peak temperatures should have been estimated lower in the case of #2 as compared with #6, thus resulting in a lower value of the estimated NOx ' Thus this methodology requires that both the peak temperature and residence time be accurately estimated. CONCLUSIONS The use of oxygen enriched air in industrial combustion processes offers considerable savings in fuel usage and potential increases in productivity. If the enrichment technology is economically feasible, the only potential barrier to the expanded use of oxygen enriched air is the environmental. The combustion of natural gas with oxygen enriched air results in higher temperatures which contribute to an increase in the production of NOx ' The National Source Performance Standards do not cover industrial furnaces. However, the NSPS for industrial steam generators is 0.2 lb N02/million BTU. The methodology developed in this paper permits the estimation of the NOx from combustion of oxygen enriched air for a given furnace of specific dimensions. The results indicate that the use of oxygen enriched air results in higher flame temperatures and longer residence times in the furnace, both of which contribute to increased NOx production to a level that would be in excess of that prescribed by the NSPS for steam generators. It is therefore recommended that this aspect of the use of oxygen enriched air be investigated further to determine exactly what the limitations are and what design modifications 195 can be made to the burner/furnace system to mitigate the$e environmenml effects. REFERENCES 1. Osborne J., "High Temperature Recuperator Opportunity Assessment" DOE/Office of Industrial Programs position paper, June 1983. 2. Hunter, S.C., "Continuous Monitoring of NOx EmisSions", The Glass Industry,p.13,March 1982. 3. Ryder, R.J.,"Use of Electric Boost to Reduce Glass Furnace Emissions", 38th Annual Glass Problems Conference, University of Illinois, November 1977. 4. Agrawal D.D. and C.P. Gupta, "Computer Program for Constant Pressure or Constant Volume Combustion Calculations in Hydrocarbon-air Systems" ASME Transactions, p.246-254,April 1977. 5. PAR Enterprises, Inc. ,"The Use of Chemical Equilibrium Thermodynamic Analysis in Predicting Furnace NOx Formation from using Preheated Oxygen Enriched Air in the Combustion of Fuels" Final Report, DOE Contract # DE-ACOl-84CE 40716, December 1985. 6. Marteney, P.J., "Analytical Study of the Kinetics of Formation of Nitrogen Oxide in HydroCarbon- Air Combustion", Combustion Science and Technology, Vol.l, p461-469,1970. 7. Garrido, G.F., A.S. Perkins and J.R. Ayton, "Upgrad ing Lime Recovery with Oxygen Enrichment'; Canadian Pulp and Paper Association Annual Meeting, Montreal, Quebec, January 26-30,1981. 8. Samuilov, E.V., I.B. Rozhdestrvenskii, N.W. Tsitelauri, V.N. Gulov and K.K. Olevinskii, "Thermodynamic Analysis in the formation of Nitrogen and Sulfur Oxides in the Combustion of Fuels, Translated from Teplofizika Vysokikh Temperatur, Vol.16, nl, Jan.-Feb. 1977,p35-41. 9. Energy and Environmental Analysis, Inc., "Industrial Waste Heat Recovery and the Potential for Emissions Reduction", Vo1.1, Main Report, # PB84-152347, February 1984. 10. Stull D.R. and H Prophet, "JANAF Thermodynamic Tables", Second Edition NSRDS-NBS 37, June 1971. 11. KVB iNc., "Reference Guideline for Industrial Boiler Manufacturers to Control Pollution with Combustion Modification", EPA Report # PB-276715 dated November 1977. 12. Ferry J., GTE Products Corp., Towanda, Pa. private communication, March 1986. |