Kinetic Model Validation of Ammonia Decomposition and Oxidation in a Nanosecond Pulsed Plasma

This study explores the decomposition and oxidation of ammonia in a dielectric barrier discharge (DBD) plasma reactor. The effects of plasma and composition parametric variation on plasma temperature and various output species were assessed. By employing optical emission spectroscopy (OES), focusing on the N₂ second positive system (𝐶₃Π_𝑢 -> 𝐵₃Π_𝑔), plasma temperature was determined over a range of plasma and composition conditions. Gas chromatography with a thermal conductivity detector (GC-TCD) and Fourier transform infrared spectroscopy (FTIR) were utilized to quantify hydrogen production and ammonia conversion, respectively. In addition, in-situ cavity ring-down spectroscopy (CRDS) was used to measure the density of NH₂ under varying plasma conditions. The specific energy input (SEI) is proven to be the dominating factor controlling plasma temperature and ammonia conversion/hydrogen production. Temperatures ranged from approximately 500 to 900 K and increased with SEI where higher temperatures favored elevated ammonia conversion. Temperature quantification allowed for the determination of steady-state residence times and expanded experimental inputs used in numerical simulation. Results obtained thus far were compared to simulations using several chemical kinetic mechanisms, which are assessed as to their fidelity in predicting the experimental results.