Ammonia conversion and NOx formation in laminar coflowing nonpremixed methane-air flames

This paper reports on a combined experimental and modeling investigation of NOx formation in nitrogen-diluted laminar methane diffusion flames seeded with ammonia. The methane-ammonia mixture is a surrogate for biomass fuels which contain significant fuel-bound nitrogen. The experiments use flue-gas sampling to measure the concentration of stable species in the exhaust gas, including NO, O2, CO, and CO2. The computations evolve a two-dimensional low Mach number model using a solution-adaptive projection algorithm to capture fine-scale features of the flame. The model includes detailed thermodynamics and chemical kinetics, differential diffusion, buoyancy, and radiative losses. The model shows good agreement with the measurements over the full range of experimental NH3 seeding amounts. As more NH3 is added, a greater percentage is converted to N2 rather than to NO. The simulation results are further analyzed to trace the changes in NO formation mechanisms with increasing amounts of ammonia in the fuel.

[1]  F. G. Roper The prediction of laminar jet diffusion flame sizes: Part I. Theoretical model , 1977 .

[2]  S. Turns Understanding NOx formation in nonpremixed flames: Experiments and modeling , 1995 .

[3]  Robert J. Kee,et al.  Kinetic Modeling of the Oxidation of Ammonia in Flames , 1983 .

[4]  James A. Miller,et al.  Kinetic modeling of hydrocarbon/nitric oxide interactions in a flow reactor , 1998 .

[5]  C. Smith,et al.  The prediction of laminar jet diffusion flame sizes: Part II. Experimental verification , 1977 .

[6]  C. P. Fenimore,et al.  Formation of nitric oxide from fuel nitrogen in ethylene flames , 1972 .

[7]  Michael C. Drake,et al.  Thermal NOx in stretched laminar opposed-flow diffusion flames with CO/H2/N2 fuel , 1989 .

[8]  Mitchell D. Smooke,et al.  Computational and experimental study of soot formation in a coflow, laminar diffusion flame , 1999 .

[9]  K. Wohl,et al.  I. Diffusion Flames , 1956 .

[10]  S. Turn,et al.  Release of fuel-bound nitrogen during biomass gasification , 2000 .

[11]  C. Law,et al.  Burke—Schumann Flame with Streamwise and Preferential Diffusion , 1984 .

[12]  Robert J. Kee,et al.  Chemical nonequilibrium effects in hydrogen-air laminar jet diffusion flames , 1977 .

[13]  R. J. Kee,et al.  Chemkin-II : A Fortran Chemical Kinetics Package for the Analysis of Gas Phase Chemical Kinetics , 1991 .

[14]  R. Blint,et al.  Relative importance of nitric oxide formation mechanisms in laminar opposed-flow diffusion flames , 1991 .

[15]  David E. Keyes,et al.  Numerical Solution of Two-Dimensional Axisymmetric Laminar Diffusion Flames , 1986 .

[16]  P. Lin,et al.  Computational and experimental study of a laminar axisymmetric methane-air diffusion flame , 1991 .

[17]  P. Glarborg,et al.  Nitric Oxide Reduction by Non-hydrocarbon Fuels. Implications for Reburning with Gasification Gases , 2000 .

[18]  Stephen Wolfram,et al.  The Mathematica Book , 1996 .

[19]  Craig T. Bowman,et al.  Control of combustion-generated nitrogen oxide emissions: Technology driven by regulation , 1992 .

[20]  P. S. Wyckoff,et al.  On the Adequacy of Certain Experimental Observables as Measurements of Flame Burning Rate , 1998 .

[21]  T. Takeno,et al.  No emission characteristics of methane-air coflow partially premixed flame , 1998 .

[22]  M S Day,et al.  Numerical simulation of laminar reacting flows with complex chemistry , 2000 .

[23]  M. Aho,et al.  Effect of fuel composition on the conversion of volatile solid fuel-N to N2O and NO , 1995 .

[24]  Ping Lin,et al.  Primitive Variable Modeling of Multidimensional Laminar Flames , 1993 .

[25]  T. Takeno,et al.  Effects of multi-dimensionality on a diffusion flame , 1996 .

[26]  Robert J. Kee,et al.  CHEMKIN-III: A FORTRAN chemical kinetics package for the analysis of gas-phase chemical and plasma kinetics , 1996 .

[27]  S. Ishizuka,et al.  Structure and tip-opening of laminar diffusion flames , 1988 .

[28]  Jan Erik Johnsson,et al.  Formation and reduction of nitrogen oxides in fluidized-bed combustion☆ , 1994 .

[29]  Rahima K. Mohammed,et al.  Computational and experimental study of no in an axisymmetric laminar diffusion flame , 1996 .

[30]  Robert J. Kee,et al.  PREMIX :A F ORTRAN Program for Modeling Steady Laminar One-Dimensional Premixed Flames , 1998 .

[31]  James A. Miller,et al.  Mechanism and modeling of nitrogen chemistry in combustion , 1989 .

[32]  Toshimi Takagi,et al.  Numerical analysis of laminar diffusion flames—Effects of preferential diffusion of heat and species , 1994 .

[33]  J. Wendt,et al.  Effect of Ammonia in Gaseous Fuels On Nitrogen Oxide Emissions , 1974 .

[34]  Richard J. Martin,et al.  Nitrous oxide formation and destruction in lean, premixed combustion☆ , 1990 .

[35]  J. Wendt,et al.  Air staging and reburning mechanisms for NOx abatement in a laboratory coal combustor , 1994 .

[36]  C. McEnally,et al.  Characterization of a coflowing methane/air non-premixed flame with computer modeling, rayleigh-raman imaging, and on-line mass spectrometry , 2000 .

[37]  H. Sarv,et al.  NOx formation from the combustion of monodisperse n-heptane sprays doped with fuel-nitrogen additives , 1989 .

[38]  F. Williams,et al.  Visible Flame Heights of Laminar Coflow Diffusion Flames , 1999 .

[39]  S. Churchill,et al.  NOx Production from the Combustion of Ethane Doped with Ammonia in a Thermally Stabilized Plug Flow Burner , 1986 .

[40]  Kermit C. Smyth,et al.  NO Production and Destruction in a Methane/Air Diffusion Flame , 1996 .

[41]  Robert J. Kee,et al.  A FORTRAN COMPUTER CODE PACKAGE FOR THE EVALUATION OF GAS-PHASE, MULTICOMPONENT TRANSPORT PROPERTIES , 1986 .

[42]  J. Warnatz Rate Coefficients in the C/H/O System , 1984 .

[43]  B. Bennett,et al.  Computational and experimental study of axisymmetric coflow partially premixed methane/air flames , 2000 .

[44]  Alexandre Ern,et al.  Detailed Chemistry Modeling of Laminar Diffusion Flames On Parallel Computers , 1995, Int. J. High Perform. Comput. Appl..