Evaluation of NO x Reburning Models under Large-Scale Conditions

In order to evaluate reaction mechanisms describing NO reburning, experimental data performed by Stapf and Leuckel (1996) using a plug-flow reactor have been compared with model calculations using the CHEMKIN code. The present investigation applies the GRI mechanism, version 2.11 (Bowman et al., 1995) and the GADM mechanism (Glarborg et al., 1998). Model calculations revealed that both mechanisms underestimate the reaction time scales at an initial oxygen content of up to 1.6% in the hot gas mixture from the precombuster. In general, the agreement between measured and modelled species profiles is much better for experiments having large methane/oxygen ratios (radical poor conditions). The GRI mechanism was found to reproduce well the experimental HCN profiles but overpredicts NH 3 largely. The GADM mechanism overpredicts HCN considerably, whereas there is good agreement for NH 3 profiles. Based on reaction rate and sensitivity analysis, their main reaction pathways have been determined under different reburn conditions. Important reburn pathways in both mechanisms are reactions of NO with CH 3 and with HCCO.