Kinetics Modeling on NO_x Emissions of a Syngas Turbine Combustor Using Rich-Burn, Quick-Mix, Lean-Burn Combustion Method

To avoid flashback issues of the high-H₂ syngas fuel, current syngas turbines usually use nonpremixed combustors, which have high NO_x emissions. A promising solution to this dilemma is rich-burn, quick-mix, lean-burn (RQL) combustion, which not only reduces NO_x emissions but also mitigates flashback. This paper presents a kinetics modeling study on NO_x emissions of a syngas–fueled gas turbine combustor using RQL architecture. The combustor was simulated with a chemical reactor network (CRN) model in chemkin-pro software. The combustion and NO_x formation reactions were modeled using a detailed kinetics mechanism that was developed for syngas. Impacts of combustor design/operating parameters on NO_x emissions were systematically investigated, including combustor outlet temperature, rich/lean air flow split, and residence time split. The mixing effects in both the rich-burn zone and the quick-mix zone were also investigated. Results show that for an RQL combustor, the NO_x emissions initially decrease and then increase with combustor outlet temperature. The leading parameters for NO_x control are temperature-dependent. At typical modern gas turbine combustor operating temperatures (e.g., <1890 K), the air flow split is the most effective parameter for NO_x control, followed by the mixing at the rich-burn zone. However, as the combustor outlet temperature increases, the impacts of air flow split and mixing in the rich-burn zone on NO_x reduction become less pronounced, whereas both the residence time split and the mixing in the quick-mix zone become important.