Evaluation of coal ammonia flames using a non-adiabatic three mixture fraction flamelet progress variable approach

A highly resolved large eddy simulation (LES) modeling of the co-firing of ammonia with pulverized coal in a single-burner test furnace of the Central Research Institute of Electric Power Industry (CRIEPI) has been performed using a non-adiabatic three mixture fraction flamelet/progress variable (3Z-FPV) approach. To parametrize the thermochemical space, a six-dimensional tabulation method based on non-premixed flamelets is introduced, which uses three mixture fractions, for ammonia, coal volatiles, and char-off gases, respectively, as well as variance of mixture fraction, reaction progress variable, and total enthalpy. The accuracy of non-adiabatic model has been tested by comparing it with experimental data and previously computed adiabatic FPV results for two different ammonia injection cases. The results show that the non-adiabatic FPV model accurately predicted the peak temperature and its location, while the peak NO, overpredicted by approximately 150 % in the adiabatic FPV model, is slightly underpredicted in the non-adiabatic FPV model. Ammonia injection in the primary reaction zone lowered NO concentrations in both cases, primarily due to dominant NO reduction reactions with ammonia under the reducing environment. Reactive conditions and higher temperature caused NH₃ dissociation, increasing H₂ and H₂O concentrations near burner exit in burner ammonia injection case.