The composition of gases from a diffusion flame above longleaf pine needle fuel beds

Abstract

The gas and tar composition of a wildland fire diffusion flame from longleaf pine needles is currently relatively unmeasured and more data are needed to fill in the gap between pyrolysis data and smoke plume data, thus improving physical and chemical modeling of wildland smoke formation. A pilot experiment to measure light gas and tar composition of such a flame is described for three flame zones: persistent flame (flame base), intermittent flame, and smoke plume. Flame gases from 24 experimental fires were collected in canisters and analyzed for CO2, CO, H2, CH4, and C2 to C7 hydrocarbon gases. Other light gases were measured using FTIR spectroscopy. Condensed gas (tar) samples were collected and analyzed using GC/MS. Results from compositional data analysis suggest significant differences in (relative) concentration of compounds detected in the three zones. Statistical tests for differences in flame zones were performed using canister data. Concentration of hydrocarbons relative to CO and CO2 decreased from the persistent flame zone through the intermittent flame zone into the flame-free plume. This was likely due to oxidation reactions in the flame as well as entrainment of air into the flame/plume. Partial agreement between persistent flame zone composition and pyrolysis data for a global kinetic model provided support for future use of the kinetics model in physically-based fire models. The identification of gases and tars in different flame zones supported a conceptual model of a wildland flame

This work was supported by the DOD/DOE/EPA Strategic Environmental Research and Development Program project RC-2640. JPA was supported by the project PID2021-123833OB-I00, funded by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) and by ERDF A way of making Europe