Accurate calculations of heat release in fires

Fire is often considered as the most hazardous accidental event which may affect safety in the chemical industries. The fire damage may be thermal or non thermal. As examples, the fire plume may transport a variety of toxic effluents, which may injure the staff of the industrial premises and the fire fighters, as well as the inhabitants in the neighbourhood. Intense radiation produced by big fires may cause serious burn injuries and generate "domino effects" to previously non affected equipment in the vicinity and result in related phenomena such as jetfires, fireballs, BLEVEs1 . Moreover, polluted extinction waters while unconfined may greatly affect the aquatic environment. Although several ambitious projects were recently carried out in the field, there is still much work to be performed to get validated techniques capable of predicting (and keeping under acceptable control) the consequences of indoor and outdoor large chemical fires

A zone model for the prediction of thermal and chemical effects of a pool fire in a forced ventilated enclosure

Zone models have been developed since the early 60s for the prediction of fire parameters such as smoke temperature, smoke filling and movement in multi-compartment buildings. Unfortunately, one major difficulty in current zone models is that heat and chemical species release rates in relation with a given fire source term are usually to be provided as input data. A new zone model for prediction of thermal and chemical effects of pool fire in a forced ventilated enclosure has been developed

Differential sensitivity of Atriplex patula and Chenopodium album to sugar beet herbicides : a possible cause for the upsurge of A. patula in sugar beet fields

In the last decade, the prevalence of Atriplex patula as a weed in the Belgian sugar beet area has increased. Possible reasons for its expansion in sugar beet fields, besides a poor implementation of the low-dose phenmedipham/activator/soil-acting herbicide (FAR) system, might be low sensitivity or evolved resistance to one or more herbicides used in sugar beet. Dose-response pot bioassays were conducted in the glasshouse to evaluate the effectiveness of five foliar-applied sugar beet herbicides (metamitron, phenmedipham, desmedipham, ethofumesate and triallate) and three pre-plant-incorporated herbicides (metamitron, lenacil, dimethenamid-P) for controlling five Belgian A.patula populations. Local metamitron-susceptible and metamitron-resistant populations of Chenopodium album were used as reference populations. Effective dosages and resistance indices were calculated. DNA sequence analysis of the photosystem II psbA gene was performed on putative resistant A.patula populations. Overall, A.patula exhibited large intraspecific variation in herbicide sensitivity. In general, A.patula populations were less susceptible to phenmedipham, desmedipham, ethofumesate and triallate relative to C.album populations. Two A.patula populations bear the leucine-218 to valine mutation on the chloroplast psbA gene conferring low level to high level cross-resistance to the photosystem II inhibitors phenmedipham, desmedipham, metamitron and lenacil. In order to avoid insufficient A.patula control and further spread, seedlings should preferentially be treated with FAR mixtures containing higher-than-standard doses of metamitron and phenmedipham/desmedipham and no later than the cotyledon stage

Chemfire : a zone model for predicting chemical effects of pool fire in a single forced ventilation enclosure

International audienceZone models have been developed since the early 60s for the prediction of fire parameters such as smoke temperature, smoke filling and movement in multi-compartment buildings. Unfortunately, one major difficulty in current zone models is that heat and chemical species release rates in relation with a given fire source term are usually to be provided as input data. A new zone model for prediction of thermal and chemical effects of pool fire in a forced ventilated enclosure has been developed. The novelty of the approach relies in particular on the provision of three sub-models that are used for reducing the number of input data needed for a given simulation. The burning rate history of liquid pool fire is calculated from a vaporisation sub-model. A solid flame sub-model is used for predicting radiative properties of flame. Yields of chemical species are estimated from a dedicated sub-model of combustion. This zone model has received some validation for use in forced ventilated enclosures only. Promising results have been obtained

La qualité : des concepts à la pratique

Introduction La référence à la « qualité » n’est pas neuve. Mais elle s’exprime aujourd’hui dans une acception spécifique, voire technique, en de nombreuses occasions et dans bien des domaines. Des normes internationales lui sont consacrées, des modèles, simples ou moins simples, sont proposés à son sujet. Les rayons des librairies s'encombrent d'ouvrages généraux, de livres introductifs, de bouquins spécialisés,… qui prétendent vous apprendre, en cent pages ou en mille, le what's what de la ..

Improvement of the hazard identification and assessment in application of the Seveso II Directive

International audienceThe Council Directive 96/82/EC of 9 December 1996 on the control of major-accident hazards involving dangerous substances, known as SEVESO II Directive, aims at the prevention of major accidents and the limitation of their consequences for human beings and environment. Although rules are well established to identify potential risk, there is no method to measure the risk level which takes into account safety devices and safety management systems implemented by operators. This paper deals with the first stage of a global methodology that aims to better assess benefits form safety devices and safety management systems through accident scenario selection

Sooth generation in fires : an important parameter for accurate calculation of heat release

Oxygen consumption (OC) calorimetry and carbon dioxide generation (CDG) calorimetry are usual methods to determine the heat release rate (HRR) in bench-scale and large-scale fire tests. The paper emphasises on measuring problems associated with fires releasing large amounts of soot. Until now, the soot-related energy transfer was hardly ever taken into consideration in practical applications of HRR calculations. From standard CDG calorimetry, a generalised relationship is introduced in order to take into account the soot generation in the accurate determination of the heat release produced in sooty fires. The analysis of the significance of this correction factor is discussed by theoretical consideration as well as from results of lab-scale experiments recently carried out on chemicals by means of the INERIS fire calorimeter

The effect of oxygen concentration on CO yields in fires

International audienceIn addition to global ventilation effects on fires, vitiation of air is a ventilation related phenomenon that can also affect the generation of chemical species in a built environment. The paper is a contribution to the study on the subject. Experiments were performed at lab-scale with the Fire Propagation Apparatus in order to study the effect of air vitiation on the CO yield. Results are also presented for the fuel burning rate. Both carbon dioxide and nitrogen were used as diluents in the inlet air flows. The oxygen concentration was decreased stepwise until the extinction point was reached. A first set of experiments was performed in well-ventilated fire conditions (equivalence ration between 0.1 and 0.25). A second set of experiments was carried out in under-ventilated fire conditions (equivalence ratio equal to 1.1). The results revealed useful for improving the combustion sub-model predictions in a zone model under development