Dynamic infrared gas analysis from longleaf pine fuel beds burned in a wind tunnel: observation of phenol in pyrolysis and combustion phases

Catherine A Banach,Olivia N Williams,Joey Chong,Tanya L Myers,Ashley M Bradley,Timothy J Johnson,David R Weise,Russell G Tonkyn

doi:10.5194/amt-14-2359-2021

Catherine A Banach, Olivia N Williams + Show 6 more

Open Access

https://doi.org/10.5194/amt-14-2359-2021

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Abstract

Abstract. Pyrolysis is the first step in a series of chemical and physical processes that produce flammable organic gases from wildland fuels that can result in a wildland fire. We report results using a new time-resolved Fourier transform infrared (FTIR) method that correlates the measured FTIR spectrum with an infrared thermal image sequence, enabling the identification and quantification of gases within different phases of the fire process. The flame from burning fuel beds composed of pine needles (Pinus palustris) and mixtures of sparkleberry, fetterbush, and inkberry plants was the natural heat source for pyrolysis. Extractive gas samples were analyzed and identified in both static and dynamic modes synchronized to thermal infrared imaging: a total of 29 gases were identified including small alkanes, alkenes, aldehydes, nitrogen compounds, and aromatics, most previously measured by FTIR in wildland fires. This study presents one of the first identifications of phenol associated with both pre-combustion and combustion phases using ca. 1 Hz temporal resolution. Preliminary results indicate ∼2.5× greater phenol emissions from sparkleberry and inkberry compared to fetterbush, with differing temporal profiles.

Highlights

Wildland fire is an important component of many ecosystems and has been used by humans for several thousand years (Crutzen and Goldammer, 1993; Pyne, 1997; Scott et al, 2014)
Multiple techniques were used to study the fire characteristics and the gas effluents: thermocouples, a Schmidt–Boelter heat flux sensor, a nadir thermal IR camera, and background-oriented Schlieren photography (Aminfar et al, 2019) to estimate heat transfer and airflow around the plants, canister samples analyzed by GC–FID, quantum-cascade (QC) infrared laser spectroscopy (Phillips et al, 2020), and broadband Fourier transform infrared (FTIR) spectroscopy
The analytical methods used in this study attempt to provide a detailed view of prescribed burning by enlisting two different FTIR acquisition modes, static and dynamic

Summary

Introduction

Wildland fire is an important component of many ecosystems and has been used by humans for several thousand years (Crutzen and Goldammer, 1993; Pyne, 1997; Scott et al, 2014). In the US, prescribed burning is used on approximately 8 million ha annually to accomplish a variety of forestry and agricultural objectives (Melvin, 2015); the impact of smoke from these fires has been studied for over 50 years (Chi et al, 1979; Biswell, 1989; Ward and Hardy, 1991; Hardy et al, 2001). The US Department of Defense (DoD) uses prescribed burning on approximately 243 000 ha annually for many of these objectives in addition to the maintenance of critical training areas (Cohen et al, 2014). In order to improve the use of prescribed burning to accomplish refined objectives, more detailed descriptions and modeling of the physical and chemical processes in fire are needed (Cohen et al, 2014)

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