Numerical Study on Nitric Oxide Production of Moderate or Intense Low-Oxygen Dilution Combustion Using Ammonia and City Gas

Ammonia (NH3) is attracting attention as a carbon-free fuel that does not emit carbon dioxide, but there is concern that a large amount of nitrogen oxides is emitted during its combustion. The mixtures of NH(3)and city gas are used as fuels, and the effectiveness of Moderate or Intense Low-oxygen Dilution (MILD) combustion to reduce nitric oxide (NO) emissions is investigated through zero-dimensional and three-dimensional numerical simulations for various NH(3)concentrations of the fuels at the lower heating value basis,E-NH3. The zero-dimensional numerical simulations show that NO emissions reach their maximum value forE(NH3)= 20-40%, and that dilution of the fuel and oxidizer by exhaust gas recirculation reduces NO emissions. On the other hand, the three-dimensional numerical simulations of an actual furnace show that MILD combustion is valid for reducing NO emissions forE(NH3)= 0%, 20% and 100%. For burner design, the nozzle diameters used for the oxidizer,D, and the distance between the fuel and the oxidizer nozzles,L, are important parameters. ForE(NH3)= 20%, a 0.39-fold reduction inDand a 2.5-fold increase inLmake the NO emissions 56% and 74%, respectively.

Automated summary

Ammonia (NH3) is being explored as a carbon-free fuel option, but concerns about nitrogen oxide emissions during combustion exist. Mixtures of NH3 and city gas are being studied for their effectiveness in reducing nitric oxide (NO) emissions through Moderate or Intense Low-oxygen Dilution (MILD) combustion. Results from zero-dimensional and three-dimensional numerical simulations show that diluting the fuel and oxidizer can help reduce NO emissions. Parameters such as nozzle diameters and distance between fuel and oxidizer nozzles are crucial for burner design in achieving reductions in NO emissions.