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Computational and Experimental Study of Solid-Phase Formation during the Decompression of High-Pressure CO2 Pipelines
No full textInternational audienceDecompression of CO2 pipelines is studied both experimentally and numerically to provide a partially validated model as the basis for the prediction of the hazards associated with CO2 solid formation. The pipeline decompression experiments, performed using a fully instrumented 36.7 m long and 50 mm internal diameter test pipe up to a maximum pressure of 45 bar, incorporating discharge orifice diameters of 4 and 6 mm, reveal the stabilization of pressure and temperature near the CO2 triple point. In addition, video recordings of the decompression flow in the reinforced transparent section of the steel pipe show that initial stratification of the constituent liquid and vapor phases is followed by rapid CO2 solid formation and accumulation in the pipe. To aid the prediction of hazards associated with solids formation in pipelines, a homogeneous equilibrium pipeline decompression model is developed, accounting for the pertinent physical properties of CO2 in the liquid, vapor, and solid states. The model is validated against the experimental data, showing ability to accurately predict the measured pressure and temperature variations with time along the pipe as well as the time and amount of solid CO2 formed upon decompression across the triple point
Accounting for turbulence in gas explosion venting design
No full textInternational audienceWith the publication of NFPA 68 (2013); a major change is in progress in venting area calculation methods for gas explosions. Old methods referring to the Kg parameter proved to be inappropriate for real applications. The present work provides new data to correlate real gas concentration and initial turbulence conditions to flame propagation and explosion overpressure during a vented gas explosion. Explosion tests were performed in a 4 m3 rectangular chamber equipped with transparent walls and vented (0.49 m2 square vent) on one side. The chamber is filled with a turbulent or quiescent hydrogen-air mixture with a purposely built injection system that allows to vary the turbulence intensity and the length scale. Gas concentration and turbulence parameters are measured with concentration gauges and Pitot probes distributed in the chamber (Duclos, 2017). Then the flame propagation is fully characterized with high speed video and explosion overpressure is measured inside and outside the chamber. The paper presents the parametric study performed by varying the initial turbulence and focuses on its influence on the inside explosion overpressure. Then physics of vented gas explosion is discussed, results are compared to developing phenomenological model
The visual side of safety
No full textInternational audienceIn this chapter, I address what I believe to be a complementary discussion for this book on the relationship between safety, models and culture. One interesting angle of analysis is indeed to focus on drawings, graphics or visualisations that have supported powerful heuristics designed to channel ways of thinking the complex topic of safety, analytically and communicatively. In order to build the argument about the importance of how drawings, pictures or visualisation structure the understanding of safety individuals and become a support for action, some illustrations are offered, covering different categories of actors populating high risks systems, from process operators to engineers and managers. From there, a discussion of more research oriented drawings is developed, based on two illustrations: the Heinrich-Bird pyramid and the Swiss Cheese Model. They are considered from several analytical categories including their generic, normative, metaphoric aspects along with their status as inscriptions, boundary and performative objects
CFD modelling of dispersion in neutrally and stably-stratified atmospheric boundary layers : results for Prairie Grass and Thorney Island
No full textInternational audienceIt is a known problem that CFD models using the standard k - epsilon turbulence model do not maintain the correct atmospheric boundary layer (ABL) profiles along a flat, unobstructed domain. The present work examines the impact of these errors in the ABL profiles on dispersion model predictions for three field-scale experiments from the Prairie Grass and Thorney Island datasets. The modified ABL profiles produced by the CFD model in the Prairie Grass experiments result in differences in the predicted concentrations of up to a factor of two, as compared to a reference model. For the Thorney Island experiment, the results for the standard k - epsilon turbulence model are sensitive to the ground surface roughness and problems are identified in relation to the grid resolution near the ground. Industrial risk assessments involving atmospheric dispersion of toxic or flammable substances using CFD models should take into account these limitations of the k - epsilon turbulence model
Experimental and numerical investigation into rapid cooling of rock salt related to high frequency cycling of storage caverns
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Dépasser les stéréotypes de management relatifs aux actions (stéréotypes-actions) en proposant de nouveaux principes guidants
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Déploiement de micro-capteurs de qualité de l’air dans les logements pour une campagne nationale - contraintes et opportunités
No full textInternational audienceL’Observatoire de la Qualité de l’Air Intérieur (OQAI) prépare actuellement une deuxième campagne nationale de connaissance de la qualité de l’air dans les logements, après celle menée en 2003-2005. Pour cette nouvelle campagne, l’OQAI souhaite, en marge des techniques de mesure plus traditionnelles, suivre en continu différents indicateurs de qualité de l’air dans plusieurs centaines de logements représentatifs du parc de résidences principales sur une durée d’une semaine à quelques mois au moyen de capteurs portables, peu bruyants, sensibles, spécifiques, fiables, et le moins coûteux possible. A cet égard, l’OQAI a mis en place un groupe de travail multidisciplinaire sur cette thématique afin d’identifier les technologies à même de répondre aux besoins de cette campagne, d’identifier les critères à la fois techniques, de contraintes sur le terrain et de communications à prendre en compte pour un déploiement dans les logements, d’étudier la possibilité d’une mise en œuvre par les occupants eux-mêmes et d’identifier les opportunités offertes par l’acquisition de ces données. L’état des réflexions en cours est partagé ici
Particle emission characterization when incinerating halogen- and sulfur- containing nanowaste using a lab scale tubular furnace operating at 1100°C
No full textInternational audienceNanotechnology is said to be the industry of the 21st century. The production of nanoproducts keeps growing at a rapid pace. In November 2016 in France, the 4th annual declaration on imported, distributed and manufactured nanoscale substances reported a total number of registrations four times that of year 2013. Consequently, the need to anticipate how to deal with these products at each step of their life cycle is more and more necessary. Nanowaste management including product incineration is to be investigated to assess the impact it could have both on human health and the environment. The growing number of registrations of nanoscale substances clearly demonstrates that the amount of nanowaste to be processed in waste treatment plant will increase in years to come. Though to date French and European regulations relative to nanowaste management do not exist, recommendations may at least be delivered to minimize possible impact on the environment and human health. Data on nanowaste incineration are still scarce, which motivates considering this question to better understand the phenomena at stake..