Author(s)

K. Chetehouna, L. Courty, L. Lemée, J. P. Garo & P. Gillard

Abstract

Thymus vulgaris is a common Mediterranean vegetal species often involved in forest fires. The aim of this work is to characterize the VOCs emitted by the needles of this plant as functions of temperature. Experiments are performed using a flash pyrolysis apparatus. The influence of two parameters, namely the heating time and heating rate are studied: the highest VOCs’ emissions are found for a heating time of 30 s at 5000 K/s. Two major compounds are identified for all the temperatures, thymol and p-cymene. The total amount of VOCs emitted increases with temperature and except for the three lowest temperatures, thymol represents more than 50% of the gas mixture. Results are compared to literature available data and to the emissions behaviour of other vegetal species. Keywords: Thymus vulgaris, VOCs emission, flash pyrolysis, forest fires. 1 Introduction Vegetation is the engine of combustion in forest fires and its characterization is important to accurately modelling fires propagation. Before the pyrolysis temperature, many Volatile Organic Compounds (VOCs) are emitted by most of the vegetal species. These VOCs are mostly monoterpenes (C10H16) and sesquiterpenes (C15H24) and they have very low values of lower flammability limits, namely less than 1% vol. in air [1]. For this reason, they are much more flammable than typical pyrolysis products (CO, CH4, etc.) and they should be taken into account for the characterization of vegetation. We can find several

Keywords

Thymus vulgaris, VOCs emission, flash pyrolysis, forest fires.