Modelling of gas flows in the goaf of retreating faces

In retreating faces, dilution of firedamp flowing out of the goaf area at the junction of face and retum roadway is problematic. Despite important flowrates and high CH4 drainage efficiencies, it has been observed that 2/3 of firedamp evacuated by the air stream concentrate in this particular place. So äs to progress in preventing such difficulties, it is necessary to better understand the repartition of gas fluxes in the goaf. This has obviously a benefit on firedamp drainage efficiency, but also on the choice of nitrogen injection points and flowrates in case of spontaneous combustion in the goaf. The use of a CFD code, PHOENICS, has allowed Simulation of circulation of three gases : air, CH4, and N2. Influence of the face dip on the repartition of CH4 patterns in the goaf area has been qualitatively demonstrated

Large scale characterisation of the concentration field of supercritical jets of hydrogen and methane

When an orifice or breach appears in the wall of a tank containing flammable gas under pressure. a jet is created which develops into an explosive cloud. Research has shown that the intensity of the explosion likely to take place in this cloud is then hiehly variable and depends on the cloud characteristics

AutoReaGas - A CFD-Tool for gaz explosion hazard analysis

Gas explosions constitute a major hazard for offshore gas and oil producing installations. A gas explosion is the consequence of an accidental release of a flammable gas, the mixing with air and a subsequent ignition. Under appropriate boundary conditions the resulting flame propagation process may develop explosive combustion and damaging blast loadings. In spaces containing a lot of equipment, this is a particular problem and a small quantity of fuel may be sufficient to give rise to the development of high explosion overpressures. If such overpressures are not anticipated in the design they may have fatal consequences for both crew and rig

Influence du confinement de la présense d'obstacles sur le déroulement d'une explosion de gaz

National audienceLes explosions de gaz sont regulierement a l'origine de degats importants dans les installations industrielles. Pour memoire, les accidents survenus ä Flixborough en 1974 (Sadee et al., 1976) ou plus recemment a La Mede en 1992 (Michaelis et al., 1995) en sont des illustrations marquantes. De par le monde, d'importants efforts de recherches ont donc ete mis en oeuvre pour prevoir et prevenir les consequences de ce type d'acciden

Damages of the Toulouse disaster, 21th september 2001

International audienceA terrible explosion of ammonium nitrate occurred on 21st September 2001, in Toulouse, in AZF plant belonging to Grande Paroisse Company, TotalFinaElf Group. The manufactured chemicals in the plant were mainly ammonium nitrate, ammonium nitrate-based fertilisers and other chemicals including chlorinated compounds. The explosion took place in a storage warehouse where roughly 400 tons of rejected off-spec materials were stored. The TNT equivalent mass of the explosion was estimated by INERIS in a range of 20 to 40 tons of TNT. The human effects of the explosion were 30 persons killed and up to 2242 people injured. The plant was located in the suburbs of Toulouse and the extent of damages was very large both on and off site with a cost estimated by insurers of 1.5 billion Euro. The first aim of this paper is to provide, outside France, information on the damages of this case history, with particular emphasis on estimates of the explosion strength's, on damages and human effects data, and on a few facts and lessons on the response to the effects and land use planning

Modélisation des effets toxiques d'un feu sur l'environnement d'un site industriel : importance des hypothèses relatives à la thermique

National audienceLes actions directes de la chaleur produite par un feu, telles que les emissions de flammes et de rayonnement thermique, les brulures, la propagation du feu a d'autres batiments ou installations non touches initialement par les flammes sont les effets les plus immediatement perceptibles des incendies. Les effets " chimiques " des feux sont les autres phenomenes ä redouter. Ils se traduisent par des consequences potentielles tout aussi redoutables et aussi variees que la reduction drastique de la visibilite en milieu confine, les dommages causes apres coup aux materiels electroniques par corrosion par les fumees acides et bien entendu, a des degres divers en fonction de la nature et de la quantite d'aliment au feu implique dans l'incendie, par un potentiel de toxicite, principalement par Inhalation de fumees

Assessment of an accidental vapour cloud explosion. A case study : Saint-Herblain, October the 7th 1992, France

International audienceEarly in the morning on October the 7th 1991, the town of Nantes (Westem France) was shaken by a deflagration. This vapour cloud explosion (VCE) occurred m a petroleum depot. This was not the first accident in such a configuration but, probably in France, the one which produced the most extensive damage to the surroundings. For instance, numerous windowpanes were broken in a 2 kilometer radius

Large scale characterisation of the concentration field to supercritical jets of hydrogen and methane

International audienceThis paper reports on an experimental investigation of the concentration field of supercritical jets of methane and hydrogen. The jets were produced by venting a tank containing gas at a pressure of 40 bar (568 psi) to atmosphere through orifices whose diameters ranged from 25 to 150 mm. The concentration measurements were made in the subsonic zone of the jets using an original echnique. This technique employs a sensor using the catalytic oxidation effect and can measure the concentration of combustible gas in highly reactive environments with no risk of ignition. The investigation was designed with experiments on a scale typical of that encountered in industry during accidental discharges of pressurized gas, a scale much larger than that normally used in a laboratory. The results show that when proper allowance is made for the expansion zone of supercritical jets it is possible to relate the results obtained in these jets with those found in variable density subsonic jets. In particular, the rates at which mass concentration decreases along the axes of supercritical and subsonic jets are equal when weighted by an equivalent diameter which takes into account the conditions of both pressure and density in the discharge sectio