Experimental study and kinetic modeling of NH3/CH4 co-oxidation in a jet-stirred reactor

This work reports an experimental and kinetic modeling study of the co-oxidation behavior of NH3/CH4 binary fuel in a jet-stirred reactor (JSR). Experimental tests are conducted by varying the reaction temperature (850-1350 K), equivalence ratio (0.5-2), and NH3 mole fraction in fuel (0-100%) individually at ambient pressure and with N2 being diluent gas. The experimental measurement shows that there exists strong competition between CH4 and NH3 oxidation in fuel-lean condition, where the addition of NH3 tends to suppress CH4 oxidation by postponing the peak CO formation to a higher reaction temperature. However, such change is not observed in stoichiometric and fuel-rich conditions. When gradually increasing the reaction temperature, a dual NO formation behavior can be noticed for both NH3/CH4 mixture and pure NH3 regardless of equivalence ratio. When gradually increasing the equivalence ratio, NO formation becomes higher with the addition of NH3 at 1100 K, while is gradually reduced with the addition of NH3 at 1300 K. Kinetic modeling of the present experimental cases is further performed with different existing reaction mecha-nisms for NH3/CH4 and NH3. The comparison of NO emission shows that there is still some space for the improvement of the currently existing reaction mechanisms, especially in the low-intermediate temperature range (850-1200 K) where NO is significantly under -predicted by all models for both NH3/CH4 and NH3. Further NO reaction pathway and sensitivity analysis suggest that the reactions associated with C-N interaction, H2NO, NH2, N2H2 and NNH are responsible for the under-prediction of NO in the low-intermediate temperature range, and their reaction parameters should be optimized for obtaining improved performance.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study reports on the experimental and kinetic modeling investigation of the co-oxidation behavior of NH3/CH4 binary fuel in a jet-stirred reactor. The experimental results reveal that NH3 tends to suppress CH4 oxidation in fuel-lean conditions, but no such effect is observed in stoichiometric and fuel-rich conditions. Kinetic modeling shows that the currently existing reaction mechanisms underestimate NO emissions in the low-intermediate temperature range, indicating the need for further optimization.