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Improving the Predictability of Chemical Equilibrium Software
No full textInternational audienceOver the past few decades, researchers have been developing tools to predict chemical reactions to aid the growing field of industrial chemistry. Currently, a large variety of numerical tools are used to predict the final chemical equilibrium based on the minimization of the Gibbs free energy. Because of the mathematical complexity of the problem, numerical methods were developed to solve this problem. These methods were reviewed in another study (submitted for publication in Comput. Chem. Eng., Predicting multi-phase chemical equilibria using a Monte Carlo technique, 2018) exhibiting their limitations and proposing an alternative. In this study, the sensitivity of the prediction as a function of the thermochemical (input) parameters is discussed showing that significant deviations are possible when the relative uncertainty between the enthalpies of formation is larger than a few kJ/mol. Often the scatter between various data sources is much larger than this. To solve this difficulty, it was attempted to derive all the required thermodynamical parameters from a base of molecular descriptors common to the chemistry targeted in this work (organic). The group contribution theory is implemented and in particular the UNIFAC descriptors and is shown to give very satisfactory results
Caractérisation de l'émission particulaire de nanodéchets halogénés lors d'une incinération dans un four de laboratoire à 1100°C
No full textInternational audienceL'élimination des déchets contenant des nanocharges (ceci incluant leur incinération) se doit d'être étudié pour en mesurer l'impact sur la santé humaine et l'environnement. Il y a peu de connaissances sur le sujet de l'incinération de déchets nanostructurés. Dans ce contexte, le projet NanoWet soutenu par l'ADEME a été mis sur pied. Il se focalise sur le traitement de déchets nanostructurés halogénés et soufrés dans les filières spécialisées à haute température (1100°C). L'objectif général du projet est triple, à savoir d'évaluer l'influence (i) de la haute température sur le processus d'incinération (ii) de la présence de gaz acide dans les fumées sur l'émission particulaire (iii) des tours de lavages installées dans l'usine de traitement sur la capture des particules
Incidence de l’humidité sur l’adsorption de COV sur charbon actif pour la caractérisation des gaz
No full textInternational audienceLa présence de pollutions organiques volatiles dans les sols nécessite la mesure des concentrations dans les gaz du sol en vue d’évaluer leurs impacts (MTES, 2017). A l’heure actuelle en France, les prélèvements des gaz du sol sont le plus souvent réalisés par aspiration et adsorption sur charbons actifs. Récurrents dans les diagnostics de sites pollués, les défauts de caractérisation des concentrations gazeuses peuvent générer des incertitudes majeures dans la conduite des Plans de gestion [1]. Ciblée comme pouvant être à l’origine de telles difficultés, l’influence de la température et de l’humidité relative sur l’adsorption d’hydrocarbures (BTEX et composés aliphatiques C4-C10) et de solvants chlorés (Tétra et trichloroéthylène) sur les supports de type charbon actif de marques SKC et Orbo est l’objet des travaux présentés. Les travaux présentés sont issus des projets EFEMAIR et TEMPAIR cofinancés par l’ADEME et des travaux de l’INERIS reposant sur des essais en chambre d’exposition pour le Ministère en charge de l’environnement dans le cadre GT Laboratoires. Les essais conduits qu’ils soient en conditions maîtrisées (chambre d’essais) ou contrôlées (sites expérimentaux) montrent, pour une exposition des charbons actifs en deçà de la capacité maximale d’adsorption, l’absence d’influence de cette humidité relative de 50 à 99% et pour des températures de 8 à 23°C sur l’adsorption des molécules ciblées pour les gammes de concentrations testées. Il a cependant été mis en évidence une compétition d’adsorption entre les différentes fractions d’hydrocarbures pouvant conduire à des déplacements des molécules entre les zones de mesures et les zones de contrôle de ces charbons actifs. Un tel phénomène conduit dans les essais réalisés à l’absence de représentativité des concentrations estimées pour les fractions d’hydrocarbures aliphatiques inférieures à C7
Les composés aromatiques polycycliques oxygénés (CAP-O) dans les sols et les eaux souterraines : Comportement sur site atelier
No full textInternational audienceAu regard de leurs propriétés physico-chimiques et de leur potentielle toxicité, les composés aromatiques polycycliques oxygénés (CAP-O) pourraient être l’une des familles de composés à inclure dans les diagnostics et programmes de surveillance des sites et sols pollués contaminés par des hydrocarbures aromatiques polycycliques (HAP), en plus des composés actuellement recherchés. Cependant, à l’heure actuelle, les données scientifiques sur leur comportement dans les sols et les eaux souterraines sont rares dans la littérature. Dans le cadre du projet MEMOTRACES, des prélèvements d’eaux souterraines ont été réalisés sur le site d’une ancienne cokerie afin de mettre en évidence leur présence dans ce milieu ainsi que leurs voies de transfert. Les 16 HAP US EPA et 11 CAP-O ont été suivis. Il a été montré que les CAP-O étaient présents dans les eaux souterraines et représentaient entre 11 et 15 % de la somme des concentrations en HAP et CAP-O. Par ailleurs, les HAP légers migrent majoritairement sous forme dissoute (colloïdes et fraction dissoute vraie), les HAP lourds sont majoritairement associés à des particules de taille supérieure à 0,7 μm, alors que les CAP-O autres que le dibenzofurane ont principalement été mesurés dans la phase dissoute vraie
On the Usefulness of Phenomenological Approach to Model Explosions in Complex Industrial Systems
No full textInternational audienceExplosion protection is the object of various national and international documents, which are focused on the functions, the intended uses or the dimensioning rules for specific systems. However, despite a few application examples are described in the usual guidelines, they are limited to the description of a protection that can be added on a single piece of equipment while it is not the case in industrial processes. Furthermore, in an ATEX explosion there is a strong coupling between the explosion and its environment. Because of this the guidelines recommendations cannot be transposed on an industrial site without due consideration. In this paper, a way to consider the real explosion conditions is given allowing a choice and dimensioning of a set of safety systems. An example is shown based on the example of a model of a real installation. The functional properties of the safety system are extracted from the certification tests whereas the explosion characteristics are extracted both from the standard combustion properties of the dust and from the latest knowledge about flame propagation. A specific focus is made on two fundamental aspects: on the one hand, the critical importance to understand how the flame propagates in a given complex system. On the other hand, the behaviour of the protection systems that can be used with caution as they quite systematically influence the explosion driven flow
Long-term anisotropic hydro-viscoplastic modeling of a drift at the Meuse/Haute-Marne URL
No full textInternational audienceIn the context of radioactive waste management, one of the options currently being considered is to store it in deep geological formations. Clay formations, in particular, show very favorable confining conditions as repositories for long-term safety of nuclear waste due to their low hydraulic conductivity and significant retention capacity for radionuclides. In France, the National Radioactive Waste Management Agency (Andra) began to build the Meuse/Haute-Marne underground research laboratory (MHM-URL) in the Callovo-Oxfordian (COx) claystone formation, lying between depths of 420 m and 550 m. With regards to the main objectives of feasibility and safety assessment of a potential deep geological repository (Cigéo), a comprehensive scientific research programme of specific in situ experiments, laboratory tests and numerical modelling have been carried out to characterize and understand the behavior of the COx claystone formation in the framework of hydromechanical (HM) processes (Armand et al. 2017). In addition to the HM couplings and the associated parameters, it appears necessary to consider at least the inherent anisotropies (mechanical and hydraulic) of such rock, but also its time-dependent behavior (Armand et al. 2017). In this paper, we consider the transient creep mechanism determined from laboratory tests in order to study its effect on anisotropy and hydromechanical behavior of COx clay. The hydromechanical couplings are then evaluated around the GCS drift of MHM-URL (drift excavated following the major principal stress and without rigid lining) under satured conditions using Comsol Multiphysics code
Physiology-based toxicokinetic modelling in the frame of the European Human Biomonitoring Initiative
No full textInternational audienceGiven the opportunities provided by internal dosimetry modelling in the interpretation of human biomonitoring (HBM) data, the assessment of the links between exposure to chemicals and observed HBM data can be effectively supported by PBTK modelling. This paper gives a comprehensive review of available human PBTK models for compounds selected as a priority by the European Human Biomonitoring Initiative (HBM4EU). We highlight their advantages and deficiencies and suggest steps for advanced internal dose modelling. The review of the available PBTK models highlighted the conceptual differences between older models compared to the ones developed recently, reflecting commensurate differences in research questions. Due to the lack of coordinated strategies for deriving useful biomonitoring data for toxicokinetic properties, significant problems in model parameterisation still remain; these are further increased by the lack of human toxicokinetic data due to ethics issues. Finally, questions arise as well as to the extent they are really representative of interindividual variability. QSARs for toxicokinetic properties is a complementary approach for PBTK model parameterisation, especially for data poor chemicals. This approach could be expanded to model chemico-biological interactions such as intestinal absorption and renal clearance; this could serve the development of more complex generic PBTK models that could be applied to newly derived chemicals. Another gap identified is the framework for mixture interaction terms among compounds that could eventually interact in metabolism. From the review it was concluded that efforts should be shifted toward the development of generic multi-compartmental and multi-route models, supported by targeted biomonitoring coupled with parameterisation by both QSAR approach and experimental (in-vivo and in-vitro) data for newly developed and data poor compounds
Proposition of threshold for waste contaminated with mercury (compounds) in application of the Minamata convention on mercury and impact assessment
No full textInternational audienceThe Minamata Convention on Mercury is a global treaty to protect human health and the environment from the adverse effects of mercury. Environmentally sound management of waste is under discussion. This note proposes a threshold for waste of category c) Contaminated with mercury or mercury compounds to be disposed of (Article 11 of the Convention), using the Globally Harmonized System of classification and labelling of chemicals of the United Nations (GHS - UNEP 2017). Mercury and mercury compounds are classified as substances for the physical, health and environmental hazards categories. The thresholds of mercury and mercury compounds classifying a mixture as hazardous for the different hazard categories (physical, health, environmental) are “Presence”, >0.1% and >0.0025% (25 mg mercury/kg of waste) respectively. For impact assessment, this threshold is then compared with large data set of hazardous (793 data), potentially hazardous (depending on the concentration of hazardous substances) (55 data), as well as natural or non-polluted anthropized media (composts, sediments, agricultural soils) (21 784 data) from France. This demonstrates that 75% of the hazardous waste have higher total mercury concentration, that potentially hazardous waste samples have lower concentrations, and that all composts, agricultural soils and marine sediments and 99% of the fluvial sediments have lower concentrations. So, this threshold will not classify common industrial waste or natural media as requiring special treatment for safe disposal, but well a large part of industrial hazardous waste
EURODELTA III exercise : An evaluation of air quality models’ capacity to reproduce the carbonaceous aerosol
No full textInternational audienceThe carbonaceous aerosol accounts for an important part of total aerosol mass, affects human health and climate through its effects on physical and chemical properties of the aerosol, yet the understanding of its atmospheric sources and sinks is still incomplete. This study shows the state-of-the-art in modelling carbonaceous aerosol over Europe by comparing simulations performed with seven chemical transport models (CTMs) currently in air quality assessments in Europe: CAMx, CHIMERE, CMAQ, EMEP/MSC-W, LOTOS-EUROS, MINNI and RCGC. The simulations were carried out in the framework of the EURODELTA III modelling exercise and were evaluated against field measurements from intensive campaigns of European Monitoring and Evaluation Programme (EMEP) and the European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI). Model simulations were performed over the same domain, using as much as possible the same input data and covering four seasons: summer (1–30 June 2006), winter (8 January – 4 February 2007), autumn (17 September- 15 October 2008) and spring (25 February - 26 March 2009). The analyses of models’ performances in prediction of elemental carbon (EC) for the four seasons and organic aerosol components (OA) for the last two seasons show that all models generally underestimate the measured concentrations. The maximum underestimation of EC is about 60% and up to about 80% for total organic matter (TOM). The underestimation of TOM outside of highly polluted area is a consequence of an underestimation of secondary organic aerosol (SOA), in particular of its main contributor: biogenic secondary aerosol (BSOA). This result is independent on the SOA modelling approach used and season. The concentrations and daily cycles of total primary organic matter (TPOM) are generally better reproduced by the models since they used the same anthropogenic emissions. However, the combination of emissions and model formulation leads to overestimate TPOM concentrations in 2009 for most of the models. All models capture relatively well the SOA daily cycles at rural stations mainly due to the spatial resolution used in the simulations. For the investigated carbonaceous aerosol compounds, the differences between the concentrations simulated by different models are lower than the differences between the concentrations simulated with a model for different seasons
Precursors and formation of secondary organic aerosols from wildfires in the Euro-Mediterranean region
No full textInternational audienceThis work aims at quantifying the relative contribution of secondary organic aerosol (SOA) precursors emitted by wildfires to organic aerosol (OA) formation during summer of 2007 over the Euro-Mediterranean region, where intense wildfires occurred. A new SOA formation mechanism, (HOaro)-O-2, including recently identified aromatic volatile organic compounds (VOCs) emitted from wildfires, is developed based on smog chamber experiment measurements under low-and high-NOx regimes. The aromatic VOCs included in the mechanism are toluene, xylene, benzene, phenol, cresol, catechol, furan, naphthalene, methylnaphthalene, syringol, guaiacol, and structurally assigned and unassigned compounds with at least six carbon atoms per molecule (USC>6). This mechanism (HOaro)-O-2 is an extension of the (HO)-O-2 (hydrophilic-hydrophobic organic) aerosol mechanism: the oxidation of the precursor forms surrogate species with specific thermodynamic properties (volatility, oxidation degree and affinity to water). The SOA concentrations over the Euro-Mediterranean region in summer of 2007 are simulated using the chemistry transport model (CTM) Polair3D of the air-quality platform Polyphemus, where the mechanism (HOaro)-O-2 was implemented. To estimate the relative contribution of the aromatic VOCs, intermediate volatility, semivolatile and low-volatility organic compounds (I/S/L-VOCs), to wildfires OA concentrations, different estimations of the gaseous I/S/L-VOC emissions (from primary organic aerosol -POA-using a factor of 1.5 or from non-methanic organic gas-NMOG-using a factor of 0.36) and their ageing (one-step oxidation vs. multi-generational oxidation) are also tested in the CTM. Most of the particle OA concentrations are formed from I/S/L-VOCs. On average during the summer of 2007 and over the Euro-Mediterranean domain, they are about 10 times higher than the OA concentrations formed from VOCs. However, locally, the OA concentrations formed from VOCs can represent up to 30% of the OA concentrations from biomass burning. Amongst the VOCs, the main contributors to SOA formation are phenol, benzene and catechol (CAT; 47 %); USC > 6 compounds (23 %); and toluene and xylene (12 %). Sensitivity studies of the influence of the VOCs and the I/S/L-VOC emissions and chemical ageing mechanisms on PM2.5 concentrations show that surface PM2.5 concentrations are more sensitive to the parameterization used for gaseous I/S/L-VOC emissions than for ageing. Estimating the gaseous I/S/L-VOC emissions from POA or from NMOG has a high impact on local surface PM2.5 concentrations (reaching 30% in the Balkans, 8% to 16% in the fire plume and C 8% to C 16% in Greece). Considering the VOC as SOA precursors results in a moderate increase in PM2.5 concentrations mainly in the Balkans (up to 24 %) and in the fire plume (C 10 %)