N₂O Formation in Selective Non-catalytic NO_x Reduction Processes

Crisanto Mendoza-Covarrubias, Carlos E. Romero, Fernando Hernandez-Rosales, Hans Agarwal
DOI: 10.4236/jep.2011.28126                

Abstract

Nitrous oxide is not an environmentally regulated species in the U.S., but it does participate in the stratospheric ozone chemistry and contributes to the greenhouse effect. Nitrous oxide has been found to be a by-product of the selective non-catalytic reduction process. Chemical kinetic calculations demonstrated that the formation of nitrous oxide in the urea-based selective non-catalytic reduction process is linked to the conversion of NO by cyano species released from the process parent compounds. This conversion occurs within in temperature window between 850 and 1050℃. With urea injection, nitrous oxide emissions represent up to 20 percent conversion of the NO_x reduced. The amount of nitrous oxide formed depends primarily on the process temperature, the amount of chemical injected, the initial NO_x level, and the carbon monoxide level in the gas stream. These observations, which were based on the chemical kinetics of the process, should be considered in designing selective non-catalytic reduction systems to minimize nitrous oxide by- product formation.

Keywords

Selective Non-Catalytic Reduction Process, Nitrous Oxide Emissions Chemical Kinetics

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	R. Weiss, “The Temporal and Spatial Distribution of Tropospheric N2O,” Journal of Geophysical Research, Vol. 86, No. C8, 1981, pp. 7185-7195. doi:10.1029/JC086iC08p07185
[2]	R. Lyon, J. Kramlich and J. Cole, “N2O: Sources, Sampling, and Science Policy,” Environmental Science and Technology, Vol. 23, No. 4, 1989, pp. 392-393. doi:10.1021/es00181a002
[3]	D. Tirpak, “The Role of N2O in Global Climate and Stratospheric Ozone Depletion,” Symposium on Stationary Combustion NOx Control, EPRI CS-5361, 1987.
[4]	Energy Information Administration, “Emissions of Green- house Gases Report,” 2008. http://www.eia.doe.gov/oiaf/1605/ggrpt/nitrous.html
[5]	W. Hao, S. Wofsy, M.McElroy, J. Beer and M. Toqan, Journal of Geophysical Research, Vol. 92, No. D3, 1987, pp. 3098-3104. doi:10.1029/JD092iD03p03098
[6]	J. Kramlich, J. Cole, J. McCarthy and Wm. Lanier, “Mechanism of N2O Formation in Coal Flames,” Combustion and Flame, Vol. 77, No. 3-4, 1989, pp. 375-384. doi:10.1016/0010-2180(89)90142-9
[7]	C. Castaldini, R. DeRosier, L. Waterland and H. Mason, “Environmental Assessment of Industrial Process Combustion Equipment Modified for Low-NOx Operation,” 1982 Joint Symnposium on Stationary Combustion NOx Control, EPA-600/9-85-022v, 1985.
[8]	L. Muzio, M. Teague, J. Kramlich, J. Cole, J. McCarthy, and R. Lyon, “Error in Grab Sample Measurements of N2O from Combustion Sources,” Journal of the Air Pollution Control Association, Vol. 39, 1989, pp. 287-293.
[9]	R. Roby and C. Bowman, “Formation of N2O in Laminar, Premixed, Fuel-Rich Flames,” Combustion and Flame, Vol. 70, No. 1, 1988, pp. 119-123. doi:10.1016/0010-2180(87)90163-5
[10]	L. Muzio, T. Montgomery, G. Samuelsen, J. Kramlich, R. Lyon and A. Kokkinos, “Formation and Measurement of N2O in Combustion Systems,” Symposium (International) on Combusttion, Vol. 23, No. 1, 1990, pp.245-250.
[11]	L. Muzio, T. Montgomery, G. Quartucy, J. Cole and J. Kramlich, “N2O Formation in Selective Non-Catalytic NOx Reduction Processes,” 1991 Joint Symposium On Stationary Combustion NOx Control, EPRI GS-7447, 1991.
[12]	EPA, “Proposed Rules, Acid Rain Program: Nitrogen Oxides Emission Reduction Program, 40CFR, Part 76,” Federal Register, Vol. 57, No. 228, 1992.
[13]	R. Kee, F. Ripley and J. Miller, “The CHEMKIN Thermodynamic Database,” Sandia Report SAND87-8215, 1987.
[14]	A. Lutz, R. Kee and J. Miller, “SENKIN: A Fortran Program for Predicting Homogeneous Gas Phase Chemical Kinetics with Sensitivity Analysis,” Sandia Report SAND87-8248, 1988.
[15]	M. Caracotsios and W. Stewart, “DASAC: Sensitivity Analysis of Initial Value Problems Including ODE’s and Algebraic Equations,” Computers and Chemical Engineering, Vol. 92, No. 4, 1985, pp. 359-365. doi:10.1016/0098-1354(85)85014-6
[16]	F. Mauss and N. Peters, “Reduced Kinetic Mechanism for Premixed Methane-Air Flames,” In: N. Peters and B. Rogg, Eds., Lectures Notes in Physics, Springer Verlag, 1995, p. 58.
[17]	J. Kramlich, J. Cole, J. McCarthy, J. Lanier and J. McSorley, “Mechanisms of N2O Formation in Flames,” Fall Meeting, Paper 1A-006, Western States Section, The Combustion Institute, 1987.
[18]	M. Jodal, C. Nielsen, T. Hulgaard and K. Dam-Johansen, “Pilot-Scale Experiments with NH3 and Urea as Reductants in SNCR,” 23rd Symposium International on Combustion, Orleans, 22-27 July 1990, p. 2370.
[19]	C. Romero and V. Ciarlante, “Sensitivity of the SNCR Process to Furnace Process Variables,” 1st U.S. DOE Conference on SCR & SNCR for NOx Control, Pittsburgh, 15-16 May 1997.
[20]	T. Hunt, “SNCR Demonstration at Public Service Company of Colorado’s Arapahoe Station,” 1992 EPRI NOx Controls for Utility Boiler Seminar, Cambridge, 1992.
[21]	D. Teixeria, C. Lin, D. Jones, J. Steinberger, R. Himes, R. Smith, L. Muzio and S. Okazaki, “Full-Scale Test of SNCR Technology on a Gas-Fired Boiler,” 1992 EPRI NOx Controls for Utility Boiler Seminar, Cambridge, 1992.
[22]	M. Berg, H. Bering and R. Payne, “NOx Reduction by Urea Injection in a Coal-Fired Utility Boiler,” 1992 EPRI NOx Controls for Utility Boiler Seminar, Cambridge, 1992.
[23]	G. De Michele, M. Graziadio, P. Massei and M. Cioni, “SNCR Application on a Tangentially Oil-Fired Boiler,” ASME, New Orleans, 28 November-3 December 1993.