Numerical Study on Formation Mechanism and Reduction Methods of NO_x in Methane/Oxygen-Enriched Air Diffusion Flame

Abstract:

In this study, a methane/oxygen-enriched air counterflow diffusion flame was analyzed numerically using detailed chemical kinetics, on the condition that the oxygen mass fraction in the oxidizer stream varied from 21% to 99%. The obtained results show that as the oxygen concentration in air increases, the maximum temperature increases; the region of combustion reaction is gradually divided into two parts, and the total NO production rate and especially the thermal NO production rate increase greatly. With consideration of the possibility of gas recirculation to minimize NO_X in the industrial combustor, the usefulness of NOX reduction in combustion was analyzed numerically when the methane stream was diluted with the inert gases N2 or CO2. The obtained results show that the flame structure and dominant mechanism of NO formation change greatly with the concentration of diluents in fuel; the emission index of NO decreases gradually when the concentration of diluent CO2 increases.

• Periodical: Advanced Materials Research (Volumes 602-604)
• Pages: 1317-1324
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.602-604.1317
• Online since: December 2012
• Authors: Yao Xun Feng, Xiao Feng Zheng, Ming Sheng Jia
• Keywords: Counterflow Diffusion Flame, Diluent, NO_x Formation Mechanism, Numerical Analysis, Oxygen-Enriched Combustion, Reduction Method

References

[1] Huang F., Ling X., Cheng X., Technology of Boiler (in Chinese), Vol. 31(2008) , p.21.

[2] Zhang K., Science and Technology of Chemical (in Chinese), Vol. 8(2009), 8(6), p.39.

[3] Nishimura M., M. Suyari, T. Suzuki and T. Takagi, Journal of the Japan Institute of Energy, Vol. 79(2000), p.321.

[4] Beltrame, A., P. Porshnev, et al., Combust. Flame, Vol. 124 (2001), p.295.

[5] Sun, C. J., C.J. Sung, H. Wang and C. K. Law, Combust. Flame, Vol. 107(1996), p.321.

[6] Tsuji H., Prog. Energy Combust. Sci. , Vol. 18(1992), p.93.

[7] Yamashita H., et al., Transactions of the JSME (in Japanese), Vol. 65(1999), p.630.

[8] Information on http: /www. me. berkekey. edu/gri_mech.

[9] Kee R. J., Rupley F. M. and Mileller J.A., CHEMKIN-Ⅱ: A Fortran Chemical Package for the Analysis of Gas-Phase Chemical Kinetics, SAND 89-8009(1989).

DOI: 10.2172/5681118

[10] Smooke M. D: Reduced Kinetic Mechanism and Asymptotic Approximations for Methane-Air Flames(Springer-Verlag, German 1991 ).