Numerical Evaluation of NO Production Routes in the MILD Combustion of the Biogas-Syngas Mixture

Abstract

In the present study, the effect of composition, pressure and inlet temperature on NO production in non-premixed MILD (Moderate or Intense Low-oxygen Dilution) combustion of biogas-syngas mixture is evaluated numerically. Several pressures, compositions and inlet temperatures are considered. Results showed that NO formation increase highly with increasing pressure and oxidizer injection temperature (Tox). It is found that production of NO is more sensitive to increasing Tox than decreasing pressure. Moreover, effect of pressure is reduced as volume of hydrogen decreases in mixture. Also, increase of maximum NO mole fraction, as a function of injection temperature is important for the B50S25 mixture. Furthermore, effect of pressure and injection temperature on different NO production routes (thermal, prompt, N2O and NO2) were evaluated. It is noticed that at low pressure, NO is mainly produced by prompt path, whereas NO2 mechanism prevails when pressure is increased. When oxidizer temperature increases, most important mechanism that produces NO is prompt one followed by thermal route and finally NO2 path. It is noticed that N2O production route is trivial for all values of pressure and Tox. The reaction path diagram was presented to show the formation routes of NO for different pressures.