Exploring the combustion chemistry of anisole in laminar counterflow diffusion-flames under oxy-fuel conditions

Biomass combustion under oxy-fuel conditions, i.e., burning biomass by using CO2/O2 mixtures as oxidizer instead of air, is a promising approach to mitigate climate change by recycling CO2 from the exhaust gas. Understanding oxy-fuel biomass combustion chemistry can further help to achieve higher efficiency and lower emissions in future design concepts. In this work, we investigated the combustion chemistry of anisole, a potential component of surrogates for biomass and volatiles, in two selected laminar counterflow diffusion flames under oxy-fuel conditions. A time-of-flight molecular-beam mass-spectrometer (ToF-MBMS) and a gas chromatograph with a mass spectrometer (GC–MS) were used to analyze the chemical compositions of the gaseous samples at various flame positions. The combined measurements allowed us to identify and quantify over 40 species, including many polycyclic aromatic hydrocarbons (PAH) and oxygenated polycyclic aromatic hydrocarbons (OPAH). Comparing the experimental results to numerical simulations using the latest kinetic model from Yuan et al. (Combust. Flame 2019, 201, 187–199), we found that some of the aromatic hydrocarbons (e.g., phenylacetylene, styrene, and ethylbenzene), PAH molecules, (e.g., naphthalene and acenaphthylene), and OPAH molecules (e.g., cresol, benzofuran, and dibenzofuran) were overpredicted by the kinetic model. The model analysis indicated that the reaction rate coefficients in PAH and OPAH chemistry may be responsible. Tentative kinetic model updates showed improvement on the predictions of benzofuran, naphthalene, and acenaphthylene. In summary, this work provides comprehensive speciation datasets from two measurement techniques, examines the latest anisole kinetic model in laminar counterflow diffusion-flames, and provides novel insights for biomass combustion chemistry under oxy-fuel conditions.