Contacteurs à membranes composites et contacteurs microporeux pour procédés gaz-liquide intensifiés de captage du CO2 en post-combustion : expérimentation et modélisation

The decrease of the CO2 anthropogenic emissions is one of the main aims of the 21st century. Different processes are developed in order to capture CO2, but gas-liquid absorption in packed columns is considered as the reference postcombustion technology. Membrane contactors, which could potentially decrease by a factor 2 to 10 the size of the absorption units due to an increased interfacial area (1000 to 5000 m2.m-3 ), a so-called intensification effect, have been investigated in this study. Two kind of hollow fibers are studied: microporous and composite membranes (i.e. a dense polymeric skin coated on a porous support). In a first part, a series of experiments is reported to evaluate the influence of some geometric and operating parameters on the process capture performances and on the mass transfer characteristics. Results obtained on short time scale experiments are in agreement to the literature results. Even though a dense skin layer on a porous support generates an additional resistance to the mass transfer, a dedicated study carried out on long time scale (several hundreds hours) show for the first time that mass transfer performances of composite fibers can be similar to microporous unwetted membranes. Moreover, the wetting resistance of the composite fibers compared to microporous hollow fibers (PP and PTFE) is clearly demonstrated. In a second part, a comparative study of different mathematical models with increasing complexity is carried out. One parameter is used to fit the experimental results: the membrane mass transfer coefficient (km). km values obtained through curve fits are in the range of data reported in the literature (10-2 to 10-5 m.s-1). However, the assumption of a km effective value which would depend of the operating conditions is addressed and discussed. This approach is different from the studies reported in the literature which generally postulates a single value for a given membrane material. Under these conditions, the composite membrane interest, which shows a constant and probably predictable value of the membrane mass transfer coefficient due to their wetting resistance, seems to be promising to intensify the gas-liquid absorption process in CO2 postcombustion capture.La réduction des émissions de CO2 anthropique est un des enjeux majeurs du 21eme siècle pour de nombreux pays. De nombreux procédés sont développés pour le captage du CO2, parmi lesquels l'absorption gaz-liquide par contacteur membranaire. L'utilisation d'une membrane permet d'intensifier le transfert grâce à une aire interfaciale développée 2 à 10 fois plus élevée (1000 à 5000 m2.m-3) que celle d'une colonne d'absorption (procédé de référence). Deux types de fibres sont étudiées : microporeuses et composites. Dans une partie expérimentale, l'influence de la nature des matériaux, des paramètres géométriques et opératoires sur les propriétés de transfert de matière et sur la stabilité des performances de captage des contacteurs membranaires est étudiée. Les résultats obtenus pour des durées d'expérimentation courte (dizaine d'heures de temps de contact), sont en adéquation avec les résultats présents dans la littérature. Bien que l'ajout d'une peau dense à un support poreux constitue une résistance supplémentaire au transfert de matière, une étude dédiée, effectuée sur des temps de contact importants (plusieurs centaines d'heures), a permis pour la première fois de valider le concept de résistance au mouillage des fibres à peau dense, comparativement aux fibres microporeuses (PP et PTFE). Dans une partie modélisation, une étude comparative d'approches mathématiques de complexité croissante a été menée. Un seul paramètre ajustable a été délibérément retenu : le coefficient de transfert de matière dans la membrane (km). Cette étude a estimé des valeurs de km obtenues par ajustement des données expérimentales dans la plage de données rapportées dans la littérature (10-2 à 10-5 m.s-1). Cependant, l'hypothèse d'une valeur caractéristique du km qui dépend du régime de fonctionnement est posée et commentée. Cette approche diffère singulièrement des travaux rapportés dans la littérature, qui postulent le plus souvent une valeur unique pour un matériau membranaire donné. Dans ces conditions, l'intérêt des fibres composites, qui présentent une valeur constante et vraisemblablement prédictible du coefficient de transfert membranaire de par leur résistance aux phénomènes de mouillage, apparaît comme particulièrement prometteur pour intensifier les procédés de captage du CO2 en post-combustion par absorption gaz-liquide

Innovative hollow fibers for crystallization process - A way to avoid fouling & control polymorphism

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Modeling strategies of membrane contactors for post-combustion carbon capture: A critical comparative study

International audienceMembrane contactors are considered as a promising process for intensification purposes of gas-liquid absorption units. CO2 post-combustion capture is one of the currently intensively investigated applications and experiments are most often performed on lab scale hollow fiber modules with a monoethanolamine (MEA) aqueous solution, usually in a large excess, as chemical solvent. Different mathematical models, showing a broad range of intrinsic complexity, have been already proposed in order to simulate or predict the separation performances of membrane contactors for this application. Unfortunately, no systematic comparison of the different modeling approaches has been performed yet. This study addresses this issue through a series of experiments performed on the two main types of hollow fiber membrane contactors (microporous PTFE and dense PMP skin composite membrane) under different sets of operating conditions. Four different types of models (constant overall mass transfer coefficient, 1D resistance in series, 1D and 2D convection-diffusion models) have been compared with the membrane mass transfer coefficient as the only adjustable parameter. It is shown that the different models lead to comparable predictions of the experimental results, with slightly similar membrane mass transfer coefficient values. This result addresses key questions in terms of strategy for model validation and with regard to the current trend of increasing model complexity. Interestingly, a different situation holds when MEA is significantly converted at the liquid outlet: in that case, a 1D model approach is required (variable mass transfer coefficient), and leads to results which are comparable to 2D models. Guidelines for a relevant model comparison strategy are finally proposed

Drop size distribution monitoring and modeling of oil-in-water emulsions in SMX+ static mixers.

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Solubility of L-Glutamic acid in concentrated Water/Ethanol solutions

International audienceIn this work the solubility of the metastable α-form and the stable β-form of L-Glutamic acid in pure water and in different water/ethanol mixtures at high concentrations of ethanol is measured by analytical gravimetric method. The experiments are carried out over a temperature ranging from 283 to 343K. The experimental results show that the solubility of the stable βform is lower than the metastable α-form regardless of the solvent studied (water or water/ethanol mixtures). The results also highlight that the solubility of both polymorphs decreases with the increase of the antisolvent concentration and increases with the temperature rising. Based on the data obtained, the enthalpy and the entropy of dissolution are estimated thanks to the empirical Van't Hoff correlation. The solubility data of both polymorphs is then correlated by Combined Nearly Ideal Binary Solution (CNIBS/Redlich-Kister) equation and the parameters are determined for the temperature studied

Dense Membrane Crystallization in Gas–Liquid Systems: Key Parameters Influencing Fouling

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Experimental study of CO2 absorption in a hollow fiber membrane contactor

International audienceA new experimental setup achieved by the CEP-Paris is presented. A hollow fiber membrane (Poly-3-OP) was used as gas-liquid contactors for CO2 removal from CO2N2 feed gas stream. CO2 is transferred from gas phase through the hollow fiber membrane contactor into a liquid phase under condition of high or low pressure. CO2 concentration is measured inlet and outlet the module by gas chromatograph. CO2 removal efficiency was given for chemical solvents monoethanolamine (MEA), Nmethyldiethanolamine (MDEA) and promising blend of methyldiethanolamine and triethylene tetramine (MDEA+TETA) will be tested. The results show that an increase of solvent's flow lead to an increase of CO 2 removal efficiency which is appreciably the same as well in the case of MEA as in that of MDEA+TETA when gas flow is lower than 20L/h. Effect of CO2 inlet mass percentage on removal efficiency depends on the solvents used. An important increase of CO2 removal efficiency is reached by using MDEA+TETA solutions as solvents, as well as MEA under specific operating parameters

Polymorphism investigation in stirred and stagnant conditions

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