Origin and justification of the use of the arrhenius relation to represent the reaction rate of the thermal decomposition of a solid

Degradation models are commonly used to describe the generation of combustible gases when predicting fire behavior. A model may include many sub-models, such as heat and mass transfer models, pyrolysis models or mechanical models. The pyrolysis sub-models require the definition of a decomposition mechanism and the associated reaction rates. Arrhenius-type equations are commonly used to quantify the reaction rates. Arrhenius-type equations allow the representation of chemical decomposition as a function of temperature. This representation of the reaction rate originated from the study of gas-phase reactions, but it has been extrapolated to liquid and solid decomposition. Its extension to solid degradation needs to be justified because using an Arrhenius-type formulation implies important simplifications that are potentially questionable. This study describes these simplifications and their potential consequences when it comes to the quantification of solid-phase reaction rates. Furthermore, a critical analysis of the existing thermal degradation models is presented to evaluate the implications of using an Arrhenius-type equation to quantify mass-loss rates and gaseous fuel production for fire predictions

The fire toxicity of polyurethane foams [Review]

Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. In addition to their flammability, polyurethanes form carbon monoxide, hydrogen cyanide and other toxic products on decomposition and combustion. The chemistry of polyurethane foams and their thermal decomposition are discussed in order to assess the relationship between the chemical and physical composition of the foam and the toxic products generated during their decomposition. The toxic product generation during flaming combustion of polyurethane foams is reviewed, in order to relate the yields of toxic products and the overall fire toxicity to the fire conditions. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. In particular, the ventilation condition has a critical effect on the yield of the two major asphyxiants, carbon monoxide and hydrogen cyanid

Impact de l'évolution de la composition des déchets ménagers sur la formation des polluants gazeux lors de l'incinération

La politique actuellement mise en œuvre aux niveaux européens et français en termes de gestion des déchets ménagers et assimilés conduit à l'augmentation de la part de ces déchets traités par recyclage ou par compostage. Cela entraîne une évolution de la part résiduelle des déchets, qui est classiquement et en respect de la législation (déchet ultime) conduite en site d'incinération afin d'effectuer une valorisation énergétique. L'objectif de la présente étude est de déterminer l'influence de l'évolution de la composition des déchets sur le processus d'incinération et sur les taux de polluants gazeux émis. Dans ce sens, le dispositif du réacteur à lit fixe à contre-courant qui permet de simuler la combustion d'une tranche verticale de déchet le long des grilles d'une unité industrielle est mis en œuvre. Trois mélanges combustibles sont alors étudiés : un représentatif de la fraction combustible des déchets ménagers actuels, et deux autres tenant compte de la modification de la composition du déchet par recyclage des plastiques ou par compostage des fermentescibles. Les essais de combustion ont été réalisés pour une large gamme de débits d'air primaire et secondaire. En même temps, les températures de combustion et les teneurs des principaux polluants gazeux émis ont été suivies. La comparaison des résultats obtenus en fonction des excès d'air de combustion pour les trois mélanges combustibles montre que l'évolution de la composition des déchets n'a pas d'impact significatif sur le process de combustion et sur la formation des polluants. Ceux-ci sont principalement dépendants des conditions de combustion et notamment de la répartition des airs comburants

Modeling the emission of hydrogen chloride and free chlorine from the thermal treatment of polyvinyl chloride- (PVC-) based plastic materials

International audienceTo simulate the emission of hydrogen chloride gas and free chlorine from the thermal treatment of plastic materials, especially those based on PVC, two mathematical models have been developed. An experimental research program has been undertaken to validate these models. It is found that the masses of hydrogen chloride and free chlorine computed with these models are in good agreement with the experimental results. According to these results, it can be assumed that the quantity of hydrogen chloride and free chlorine produced during the thermal treatment of PVC-based materials strongly depends on the pyrolysis temperature and duration. The agreement between the results from simulations and empirical studies also shows the capability of these models to predict the amount of gas that will be produced from PVC-based materials upon thermal treatment

Peren2bois : évaluation technico-économique des performances énergetiques et environnementales des meilleures techniques disponiblesde réduction des émissions de poussières fines et de composés organiques pour les appareilsde combustion domestique utilisant la biomasse

National audienc

Peren2bois : évaluation technico-économique des performances énergetiques et environnementales des meilleures techniques disponibles de réduction des émissions de poussières fines et de composés organiques pour les appareils de combustion domestique utilisant la biomasse

National audienc

Proceedings of the first workshop organized by the IAFSS Working Group on Measurement and Computation of Fire Phenomena (MaCFP)

This paper provides a report of the discussions held at the first workshop on Measurement and Computation of Fire Phenomena (MaCFP) on June 10-11 2017. The first MaCFP workshop was both a technical meeting for the gas phase subgroup and a planning meeting for the condensed phase subgroup. The gas phase subgroup reported on a first suite of experimental-computational comparisons corresponding to an initial list of target experiments. The initial list of target experiments identifies a series of benchmark configurations with databases deemed suitable for validation of fire models based on a Computational Fluid Dynamics approach. The simulations presented at the first MaCFP workshop feature fine grid resolution at the millimeter- or centimeter-scale: these simulations allow an evaluation of the performance of fire models under high-resolution conditions in which the impact of numerical errors is reduced and many of the discrepancies between experimental data and computational results may be attributed to modeling errors. The experimental-computational comparisons are archived on the MaCFP repository [1]. Furthermore, the condensed phase subgroup presented a review of the main issues associated with measurements and modeling of pyrolysis phenomena. Overall, the first workshop provided an illustration of the potential of MaCFP in providing a response to the general need for greater levels of integration and coordination in fire research, and specifically to the particular needs of model validation