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

Abstract

To avoid flashback issues of the high-H2 syngas fuel, current syngas turbines usually use nonpremixed combustors, which have high NOx emissions. A promising solution to this dilemma is rich-burn, quick-mix, lean-burn (RQL) combustion, which not only reduces NOx emissions but also mitigates flashback. This paper presents a kinetics modeling study on NOx 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 NOx formation reactions were modeled using a detailed kinetics mechanism that was developed for syngas. Impacts of combustor design/operating parameters on NOx 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 NOx emissions initially decrease and then increase with combustor outlet temperature. The leading parameters for NOx 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 NOx 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 NOx reduction become less pronounced, whereas both the residence time split and the mixing in the quick-mix zone become important.