Investigation of NO Reburn Chemical Mechanism at High Pressure

Stanford University, Stanford CA

Investigators

Abstract

ABSTRACT-BOWMAN This is a combined experimental and modeling study of nitric oxide (NO) reburning chemistry. The primary objective is an improved understanding of the reaction mechanism for reburning expressed as an optimized comprehensive model useful for prediction of NO emissions from laboratory flames. It may also serve as the basis for reduced mechanisms that can be incorporated into the CFD design codes used by industry. The experiments are conducted in a high-pressure flow reactor that can be operated at pressures up to 50 bar. The hot-gas source for the reactor is a laboratory burner operating on methane-oxygen-nitrogen. Varoius amounts of NO are added to the feedstream to simulate levels in practical devices. Downstream of the burner, fuel is injected into the reactor and rapidly mixed with the combustion products to initiate the reburning reaction. Temperature and concentration profiles of stable species are measured using traversing probes coupled to on-line analyzers. The concentrations of injected fuel are sufficiently small that reburning occurs under nearly isothermal conditions in order to simplify data interpretation. A range of temperatures, pressures, fuel types, and reburn-zone stoichiometrics are investigated. The modeling study employs solution mapping; in this approach, a starting detailed reaction mechanism and rate and thermochemical parameters are optimized by successive comparisons of model predictions with experimental data within a set of constraints that reflect prescribed uncertainties in the model parameters. Reburning is a promising control technology for nitrogen oxide (NOx) emissions that uses natural gas or other fossil fuel as a reducing agent to remove nitrogen oxides from combustion products. It also plays an important role in establishing NO emissions from nonpremixed hydrocarbon-air flames and fuel-rich premixed hydrocarbon-air flames.