Work

Effect of Hydrogen-Enriched Syngas and Nitrogen Dilution on Ammonia Deflagration Characteristics at Moderate Pressure

Year: 2025

Type: article

Abstract: This research investigates the impact of syngas, hydrogen-enriched syngas (H/C ratio), and nitrogen (N2) diluent on the combustion characteristics of NH3/air mixtures in a constant volume vessel. Pressure peak (pmax), combustion duration time (tc), maximum rate of pressure rise (dp/dt)max, and laminar burning velocity (SL) were obtained at an initial pressure p0 = 3 bar, a temperature T = 300 K, and at various equivalence ratios ϕ = 0.8–1.3. The results indicate that increasing the syngas proportion and/or H/C ratio could enhance pmax, (dp/dt)max, SL, and shorten tc. The reverse is true for the dilution of N2 to the NH3/syngas mixtures. The maximum value of SL of NH3/syngas/air mixture is nearly at ϕ = 1.1 for all cases in which SL varies from 7.5 to 22 cm/s, increasing by 1.25 to 3.7-fold as compared to its values of NH3 flame. Using Mei-Mech, the sensitive analysis shows the most dominant reactions for SL of the stoichiometric NH3/syngas/air mixtures, including (R1): H + O2 = O + OH, (R15): H + O2 (+M) = HO2 (+M), (R76): NH2 + NH = N2H3, and (R94): NH2 + NH = N2H2 + H, where R1 and R15 exhibit the highest positive and negative sensitivity coefficients, respectively. Notably, in the case of H/C ratio effect, the net reaction rate of (R3): H2 + OH = H2O + H significantly increases, whereas it is less or negligible for the remaining reactions.

Source: ACS Omega

DOI: 10.1021/acsomega.5c03002