Experimental and kinetic modeling study on NH3/syngas/air and NH3/bio-syngas/air premixed laminar flames at elevated temperature

Ammonia (NH 3 ) can help achieve large-scale storage and long-distance transportation of renewable energy. The co-firing of NH 3 with syngas and bio-syngas and increasing the initial temperature of reactants are economical and effective methods to enhance the reactivity of NH 3 flames in boilers and gas turbines . An accurate kinetic model is essential for developing corresponding burners. The current kinetic models are not accurate enough in temperature dependence. Laminar burning velocities ( S L ) of NH 3 /syngas/air and NH 3 /bio-syngas/air mixtures were measured at various H 2 contents in syngas and NH 3 contents in the mixtures, equivalence ratios of 0.7~1.4, atmospheric pressure, and elevated temperature up to 423 K in a high-pressure constant-volume combustion vessel. A detailed kinetic model was developed for NH 3 /syngas combustion and validated based on the literature data. The experimental results show that slightly rich flame, high mole fractions of syngas/bio-syngas, and elevated initial temperature contribute to increasing the S L . Kinetic modeling analysis was performed for interpreting the effect of fuel composition, equivalence ratio and initial temperature on the laminar flame propagation characteristics . The elevated H 2 content in syngas provides a stronger chemical effect and the enhanced laminar flame propagation of NH 3 /syngas/air and NH 3 /bio-syngas/air mixtures is dominated by chemical effect. Due to the presence of diluent (CO 2 and N 2 ), thermal effect has a negative influence on the enhancement of NH 3 /bio-syngas/air flame propagation. Although diluent hardly changes the NH 3 consumption pathways, it will significantly reduce the NH 3 consumption. Different NH 3 consumption pathways are preferred by lean and rich flame. Sensitivity analysis shows that NH 2 chemistry is favored by rich flames. Since NH 2 + NH = N 2 H 2 + H promotes the production of H radical in rich flames, it has the greatest influence on the S L of rich flames. H 2 is more capable of improving the temperature dependence of NH 3 /syngas/air flame than CO . The increased importance of NH 3 chemistry accounts for the strong temperature dependence of NH 3 /bio-syngas/air flame.