Performance and Routes of Nitrogen Oxide Formation of MILD Forward-Flow Furnace with Reflector

Abstract

High-momentum jets, which are the key parameter to achieve moderate or intense low-oxygen dilution (MILD) combustion may lead to insufficient residence time and high CO emissions, especially for furnaces with a forward-flow configuration. A reflector for application in the furnace was proposed by two-dimensional numerical simulations to reduce the CO emissions and maintain low NOx emissions. The prediction showed a remarkable agreement with measurements. The effects of the reflector height H, the excess air factor λ (changes in the inlet methane-mass flow rate), and the hydrogen content in the blended gas were investigated. The numerical results indicate that the reflector blocks the reactant’s flow, intensifies the combustion before it, and prolongs the residence time of flue gases both before and behind it. The added hydrogen in methane can intensify combustion, increase reaction temperature and NO emissions, and reduce CO emissions. The reaction rates of thermal, prompt, NNH, and N2O-intermediate routes increase with the decrease of λ. The addition of hydrogen decreases the rate of the prompt route, but the rates of NNH and thermal routes increase. MILD combustion is achieved under the reflector conditions, considering the nearly uniform temperature distribution and the low pollutants.