Ammonia Conversion and NOx Formation in Laminar Coflowing Nonpremixed Methane-Air Flames

Neal Sullivan
ITN Energy Systems
8130 Shaffer Parkway
Littleton, CO 80127
Anker D. Jensen and Peter Glarborg
Department of Chemical Engineering
Technical University of Denmark
DK-2800, Lyngby, Denmark
Marcus S. Day, Joseph F. Grcar and John B. Bell
Center for Computational Sciences and Engineering
Lawrence Berkeley National Laboratory, 50A-1148
Berkeley, CA 94720
Christopher J. Pope
Combustion Research Facility
Sandia National Laboratories
Livermore, CA 94551
Robert J. Kee
Engineering Division
Colorado School of Mines
Golden, CO 80401


This report was submitted to Combustion and Flame

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 models 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.