Detailed Kinetic Mechanism for the Oxidation of Ammonia Including the Formation and Reduction of Nitrogen Oxides

This
work introduces a newly developed reaction mechanism for the oxidation
of ammonia in freely propagating and burner-stabilized premixed flames
as well as shock-tube, jet-stirred reactor, and plug-flow reactor
experiments. The paper mainly focuses on pure ammonia and ammonia–hydrogen
fuel blends. The reaction mechanism also considers the formation of
nitrogen oxides as well as the reduction of nitrogen oxides depending
upon the conditions of the surrounding gas phase. Doping of the fuel
blend with NO2 can result in acceleration of H2 autoignition via the reaction NO2 + HO2 ⇋
HONO + O2, followed by the thermal decomposition of HONO,
or deceleration of H2 oxidation via NO2 + OH
⇋ NO + HO2. The concentration of HO2 is
decisive for the active reaction pathway. The formation of NO in burner-stabilized
premixed flames is shown to demonstrate the capability of the mechanism
to be integrated into a mechanism for hydrocarbon oxidation.