Academic literature on the topic 'Réacteurs multifonctionnels'
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Dissertations / Theses on the topic "Réacteurs multifonctionnels":
Ferrouillat, Sébastien. "Étude du micro-mélange pour la caractérisation des performances d'échangeurs-réacteurs compacts multifonctionnels." Nantes, 2004. http://www.theses.fr/2004NANT2076.
Various design parameters of compact heat exchanger-reactors have been characterized in order to develop a new methodology for their design and optimization. The use of compact heat exchanger as a chemical reactor constitutes a significant break trough towards a new approach of chemical processes. In order to answer the compelling operation requirements, heat and mass transfer phenomena must be precisely investigated. Therefore, by using an original physico-chemical method, micro-mixing and thermo-hydraulics of turbulent flows have been studied to compare heat and mass transfer performance of selected geometries. Based on the results of this study a substantial data base is built. Using this database a novel process modeling has led to a creative design of future compact heat-exchanger reactors
Ghanem, Akram. "Intensification des transferts : typologies par régime d'écoulement et critères de performance d'échangeurs/réacteurs multifonctionnels." Ecole centrale de Nantes, 2013. http://www.theses.fr/2013ECDN0034.
The concept of multifunctional heat exchanger/reactor (MHE/R) includes all systems efficient for the realization of one or several unitary operations on industrial fluids with high productivity and reduced energy expenditures. The aim of the present work is to characterize the performance of different MHE/R configurations in terms of mixing and heat transfer using numerical and experimental techniques. An energy efficiency approach is adopted to evaluate the feasibility of each configuration based on common performance criteria. In the laminar regime, chaotic advection produced in the Split-And-Recombine (SAR) reactors promotes mixing by diffusion. Flow characteristics, heat transfer capacities, and mixing qualities are investigated in two SAR configurations. Superior mixing qualities are observed in these devices and convective heat transfer is enhanced up to 20 folds compared to classical geometries. In the transitional or inertial regime, modified surface geometries and tube inserts are most efficient in process intensification. Mixing enhancement in two corrugated channel reactors with different radii of curvature and a tube fitted with helical inserts is assessed by chemical probe. Mixing intensification relative to an empty tube reaches as high as 100 folds in the laminar regime. In the turbulent regime, convective heat transfer intensification produced by the trapezoidal vortex generator is quantified in the High-Efficiency Vortex (HEV) static mixer and heat exchanger by experimental thermal measurements. Convective heat transfer in this geometry attains values around 12 times higher than those recorded in a classical plain tube configuration
Mohand, Kaci Hakim. "Caractérisation des capacités de micromélange des échangeurs/réacteurs multifonctionnels par sonde chimique : application au HEV." Nantes, 2007. http://www.theses.fr/2007NANT2131.
The course of fast and instantaneous chemical reactions in industrial reactors can strongly be affected by the manner in which the reagents are arranged in molecular level. These effects are observed in reactive mixing of gases and liquids in both turbulent and laminar flows. Many works (Bourne (2003) ; Baldyga et al. (1995e)) showed that the mixing due to the small energetic vortices acting near the Kolmogorov scale is the limiting mechanism of the mass transfer. This is commonly called the micromixing step. In this work we show the interest in using a chemical probe to characterize the micromixing in reactors. We are interested in two particular points: - adaptation of the method to continuous flows. This method was largely and generally tested and used in batch reactors, but rarely used in continuous reactors. The present work is a continuation of a previous work carried in CEA/GRETh and LTN (Ferrouillat (2004)), - study of the relevance and validity of the chemical probe results with the information on mixing properties achieved by others methods. Mcromixing measurement is performed by a local injection. The limiting reagent, which is injected in default to an excess of reacting reagents, reacts with its surrounding medium and is therefore totally consumed at the end of the reaction. The conversion rate of the reagents gives an indication the segregation at the local level in the mixing. The selectivity of the chemical reactions can determine the quality of the mixture at the local level by a so-called "segregation index". This parameter, defined by the distribution of the products reactions, is a function of the operating conditions. Because of its dependence on the experimental conditions, it can not characterize the micromixing in an absolute way. In order to obtain quantitative information from the measurements, it is necessary to use a micromixing model which permits to link the segregation index to the micromixing characteristic parameters (micromixing time and dissipation rate)
Behloul, Chakib Rafik. "Méthodes de conception de réacteurs multifonctionnels (réacteur-échangeur-séparateur) : application à la synthèse directe de DME à partir de CO₂ et d’H₂." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0249.
The depletion of resources and the accumulation of pollutant gases in the atmosphere are nowadays of growing concern. The current energy transition requires that certain material and energy transformation processes be partially modified or profoundly reconsidered to fit more sustainable operating conditions. Low-carbon electricity and hydrogen can substitute fossil fuels, leading to an energy mix with a low greenhouse gas (GHG) footprint. In addition to hydrogen, the production of alternative fuels and high value-added products is another way to support the energy transition.Looking for optimal, sustainable and economical processes is therefore a major challenge that process engineers are facing. The present work has thus focused on the intensification of mass and energy transformation processes, through multifunctional units, which take advantage of the synergies between elementary functions of transformation (reaction, transfer, separation, etc.) within an intensive equipment. The concept of multifunctional reactors, coupling several elementary functions, has been a real success when historical demonstrators were created (Eastman-Kodak process, etc.), but their implementation has not been generalized, due to a lack of practical design methodology.This work focuses on the implementation of some intensification methodologies to understand and improve the performance of a process involving balanced exothermic reactions. The dimethyl ether (DME) direct synthesis from CO₂ and H₂ is considered as a case study. Different exploratory ways for the DME direct synthesis process development have been investigated based on modeling and simulation. Reactor- Heat exchanger, multifunctional reactor (reactor-heat exchanger-membrane separator), hybrid elementary block processes and a process involving the cooled reactor in a conventional process environment in the presence of additional unit operations and recycle loop are studied from different angles. Different optimization cases and strategies have been addressed which differ by the decision variables and the solving method. The different methodologies applied have demonstrated the relevance of the solutions obtained and the opening towards process innovation.At the equipment level, the profiles optimization represents the heart of the methodology. The results demonstrate the potential of multifunctional reactors: a CO₂ conversion per pass of 98%, a DME yield of 95% and the possibility to remove a distillation column are obtained. In order to assess the maximum achievable performance in a multifunctional reactor, a hybrid process of elementary blocks has been optimized. At the process scale, the reactor behavior has been studied to further understand the impact of the reactor integration in a recycle loop and to estimate the local and global effects on the multiple performance criteria. Based on various criteria (overall DME yield, overall CO₂ conversion, TRL, etc.), the comparison of the different designs revealed that a reduction of the equipment number by a factor of 11 is possible in the case of a multi-functional reactor choice
Aslan, Lina. "Dégradation atmosphérique de composés organiques multifonctionnels : les hydroxycétones et les aldéhydes insaturés." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10120/document.
This work was carried out with the objective of providing relevant information on the atmospheric fate of two families of multifunctional oxygenated volatile organic compounds (OVOCs), hydroxyketones and unsaturated aldehydes, to complement atmospheric models for air quality forecasts and for the drafting of regulations. The reactivity of the selected compounds was carried out in a flexible atmospheric simulation chamber equipped with various analytical techniques. The present work provides the first kinetic and mechanistic study of 4-hydroxy-4-methyl-2-pentanone (4H4M2P) photolysis and the first determination of the relative rate coefficient for the reaction of Cl atoms with 4H4M2P. The photolysis frequencies of 4-hydroxy-3-hexanone (4H3H) and 5-hydroxy-2-pentanone (5H2P) were also determined. These measurements enable estimating the atmospheric lifetimes of the three compounds by photolysis which ranged from 7 to 28 days. The main photolysis products of 4H4M2P were acetone (121±4)% and formaldehyde (20±1)%. These results allowed us to propose a mechanistic scheme for photolysis including a Norrish II intramolecular rearrangement process. In a second part, the preliminary study of photolysis kinetics of two unsaturated aldehydes, trans-2-hexenal (T2H) and trans-2-pentenal (T2P) was carried out. The estimated rate constant for photolysis of T2H ((1.2±0.6)´10-3 h-1) indicates that the photodissociation of T2H is negligible in the atmosphere. All the data obtained show that the photolytic reactivity of OVOCs is strongly linked to their structure
Ali, Samer. "Concept innovant d'échangeur/réacteur multifonctionnel par contrôle dynamique passif par générateurs de vorticité flexibles." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0034/document.
The aim of this study is to investigate the use of fluid-structure interaction (FSI) to improve heat transfer and mixing performances in multi-functional heat exchangers/reactors, and to evaluate configuration designs where the main target is to produce and maintain self-sustained oscillations of flexible vortex generators. At first, two dimensional laminar flow studies are numerically investigated. The results show that a minimum of three alternating flaps is needed to produce an instability that leads to large displacement oscillations. However, the introduction of two co-planar flaps upstream destabilizes the flow by creating periodic forces that act on the alternating downstream flaps. Hence, this results in artificially increasing the reduced velocity that will induce the alternating flaps to be in a lock-in state. Thus in this case, large displacement amplitudes are created with two alternating flaps only. The free flaps oscillations produce vortices of higher strength which have a positive impact on heat transfer and mixing. Secondly, a three dimensional HEV configuration with flexible trapezoidal vortex generators inclined with an angle of 45◦ with respect to the wall and reversed opposite to the flow direction is numerically investigated. Fast Fourier Transformation is applied on the temporal variation of the Proper Orthogonal Decomposition (POD) coefficientswhich displays a dominant peak in the flow and corresponds to the vortices periodic formation and detachment. This dominant frequency synchronizes well with the structural oscillation frequency and the fundamental frequency of the tabs reaching a lock-in state and leading to large oscillation amplitudes
Broust, François. "Le cyclone : un réacteur multifonctionnel : application à la pyrogazéification et à la pyroliquéfaction de la biomasse." Vandoeuvre-les-Nancy, INPL, 2003. http://www.theses.fr/2003INPL064N.
In fast pyrolysis conditions, biomass can be converted mainly into liquids (bio-oils) or into gases (high fractions of CO and H₂ which are of energetical or chemical interest. The experiments reported in this work are performed in a laboratory-scaled set-up including a cyclone reactor heated at its walls and fed by a flowrate of wood sawdust. All the products of the reaction (char, liquids and gases) are collected and analysed. The mass and elementary (C, H, 0) balances closures are very accurate. Basically by changing the operating conditions, the products distribution is significantly varied : the reaction can be directed to pyro-liquefaction at low temperature (maximum yields of liquids : 75 %) or to pyro-gasification at high temperature (maximum yields of gases : 85 %). A maximum throughput close to 1 kg h-¹ may be achieved in steady state in a 0. 5 L reactor. At lower temperatures, the excess of char formed can be converted during steam gasification steps alterned with the pyrolysis sequences. A general modelling takes into account the scaling laws of the reactor (hydrodynamics and heat transfers) and a scheme for the consumption of the particules and for thermal cracking of vapours. It allows to predict the variations of the selectivities as a function of the operating conditions, in agreement with the experimental results, and for different sires of cyclones. Besides, secondary cracking reactions are proved to occur mainly in the heart of the reactor, but also partly inside a thin boundary layer close to the hot walls
Abou, Rich Sami. "Films polymères organosiliciés multifonctionnels déposés et modifiés dans un réacteur duplex en post décharge d'un plasma micro-onde." Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10125/document.
Organosilicon polymers deposited from the decomposition of the TMDSO monomer in a nitrogen plasma afterglow show attractive properties for applications needing high growth rates. These polymers, having a siloxane structure, were deposited and studied under various conditions of gas flows TMDSO/O2 (Monomer/vector gaz), power, and for thicknesses ranging from tens nm to 30 µm by means of various technics of analysis (Reflectometry, FTIR, XPS, Ellispometry, AFM, TEM). A mechanism of polymerization based on the study of the vibrations of the bonds Si-O-X (X=O, C) and Si-H detected by infrared spectroscopy was proposed. We were indeed able to make evidence the variations of the relative abundance of the forms of type "ring" and "linear" in the polymer. The Si-H bond was shown to be sensitive to these changes of environment. Imaging on the reaction cone allowed, by analysis of the gaz transport, to provide sorne further elements of understanding about the decomposition of the monomer. This study suggests an additional mechanism associating the formation of the radicals peroxides produced by direct reactions involving both the molecular oxygen and nitrogen atoms which are strongly present in such a post-discharge. The transformation realized within the same reactor, in order to reduce roughness layer, in oxidizing environment (postdischarge N2/O2) modifies effectively the material by re-enforcement of the crosslinking with formation of a supercial silica-like layer. A simple model for prediction of the thickness of this layer, based on the infrared spectroscopy, was proposed on the basis of the initial thickness of the film, the time of treatrnent and a new element, the global contraction of the film
Pacheco, Sandoval Leonardo Esteban. "Production d'hydrogène par vapo-reformage de méthanol : intensification des transferts." Nantes, 2012. http://archive.bu.univ-nantes.fr/pollux/show.action?id=585bbe7d-5a79-4d63-99aa-19d5101658b3.
The aim of this numerical work is to study the influence of flow turbulence (offset OSF fins coated with CuO/ZnO/Al2O3 catalyst) on the conversion rate of methanol and also on the selectivity of this catalytic reaction. A thorough literature search of methanol steam reforming permitted retaining for this work the kinetic model developed by Peppley (1997) based on the SRM, WGS and methanol decomposition equations. A one-dimensional reactor approach allowed validating the kinetic model using the experimental results from literature for different operational conditions. A sensitivity study to the significant parameter of the process (temperature, pressure, H2O/CH3OH ratio, etc. ) is then carried out. A two-dimensional approach revealed the influence of reactor geometry and catalyst as well as the existence of certain regions in the reactor which favorise certain reactions (sometimes coupled) in steam reforming of methanol. Finally the effects of turbulence generators on the conversion rate of methanol and the selectivity of the catalytic reaction was investigated. Two aspects were specifically studied: “flow” and “reactive surface distribution”. A reactor composed of catalyst coated inserts (offset fins) is compared with a duct flow, and promising numerical results are obtained
Sellami, Jawhar. "Conception, mise en œuvre, développement et modélisation de réacteurs de précipitation utilisant des lits fluidisés." Thesis, Vandoeuvre-les-Nancy, INPL, 2008. http://www.theses.fr/2008INPL088N/document.
The objective of this work is to conceive, develop, implement and to optimize a continuous technology allowing a good control of the precipitation reactions, fast chemical process, giving birth to a solid phase. This precipitor is a multipurpose engine with fluidized bed which did not make the same great strides like fluidized bed crystallizers. Two experimental approaches were adopted : (1) the study of the mixing phenomena of the reagents and (2) the study of the influence of the operating conditions on the precipitation of a model product. The model product selected for this study is the calcite, the polymorphic most stable phase of calcium carbonate which has three polymorphs: vaterite, aragonite and calcite. The latter is obtained by the precipitation reaction between the calcium chloride and sodium carbonate solutions at a temperature of 20° C and a complexing agent (sodium citrate) to have the required crystalline form. A kinetic study was undertaken for the determination of the nucleation and crystalline growth kinetics of calcite in citrate medium. The fluidized bed reactor, having a volume of 10 L, consisted of two zones: cylindrical for fluidization and classification of the particles and cylindro-conical for decantation, was conceived at the Chemical Engineering Science Laboratory (LSGC). The study of mixing phenomena, performed using the decoloration acid-base reaction and the hydrodynamic study, carried out using suspensions of glass microballs, made it possible to develop and optimize this multipurpose reactor. The feasibility of the precipitation of calcite in a fluidized bed was then checked. The experiments carried out in the presence of an important solid content made it possible to decrease supersaturation and to support the crystalline growth. The precipitate obtained presents a relatively narrow size distribution and the particle shape is appreciably spherical. Lastly, the modelling tests of the fluidized bed reactor were undertaken to carry out simulations using the FLUENT commercial computer code