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Liquid-liquid microfluidic systems rely on the intricate control over the fluid properties of either miscible or immiscible mixtures. Herein, we report on the use of partially miscible binary liquid mixtures that lend their microfluidic properties from a highly temperature-sensitive mixing and phase separation behaviour. For a blend composed of the thermotropic liquid crystal 4-Cyano-4'-pentylbiphenyl (5CB) and methanol, mixing at temperatures above the upper critical solution temperature (UCST; 24.4°C) leads to a uniform single phase while partial mixing can be achieved at temperatures below the UCST. Thermally-driven phase separation inside the microfluidic channels results in the spontaneous formation of very regular phase arrangements, namely in droplets, plug, slug and annular flow. We map different flow regimes and relate findings to the role of interfacial tension and viscosity and their temperature dependence. Importantly, different flow regimes can be achieved at constant channel architecture and flow rate by varying the temperature of the blend. A consistent behaviour is observed for a binary liquid mixture with lower critical solution temperature, namely 2,6-lutidine and water. This temperature-responsive approach to microfluidics is an interesting candidate for multi-stage processes, selective extraction and sensing applications.

The enzymatic esterification of oleic acid and 1-butanol to butyl oleate was performed in an aqueous-organic system in capillary microreactors with various inner diameters operated under slug flow. The free Rhizomucor miehei lipase in the aqueous phase was used as catalyst and n-heptane as the organic solvent. A close to 100% yield of butyl oleate could be achieved in the microreactor made of polytetrafluoroethylene within 30 min residence time at 30 °C. The reaction rate is well described by the existing kinetic model based on a Ping Pong Bi Bi mechanism with competitive inhibition of 1-butanol. This model was extended to describe the effect of the interfacial area and aqueous to organic flow ratio in microreactors. By performing the reaction at low aqueous to organic flow ratios in hydrophilic microreactors (e.g., made of stainless steel), the enzyme turnover number could be enhanced significantly making it promising for process intensification.

A simple kinetic model for the standard NH3-SCR reaction by Cu-ZSM-5 catalysts has been developed by assuming three reaction steps: NH3 adsorption (desorption), reactions of adsorbed NH3 with O2 (NH3 oxidation) and NO (NH3-SCR). The model is based on Arrhenius parameters for NH3-SCR and NH3 oxidation by a powder catalyst, combined with models for heat and mass transport and parameters of monolithic catalysts. The model is validated with the experimental results, not included in the estimation of the model, for NH3-SCR by monolithic catalysts with different parameters (catalyst loading and cell density). NOx removal from diesel exhaust, generated by engine bench, was also carried out by using monolithic Cu-ZSM-5 and Cu-AFX catalysts. The results suggest the poisoning effect of hydrocarbons in the exhaust emissions on NOx conversion is more significant for Cu-ZSM-5 than Cu-AFX.

Turning raw biogas into biomethane as energy carrier requires the selective removal of CO2 in a biogas upgrading process or a total conversion of CO2 to CH4 which is generally energy intensive. During membrane electrolysis, electrical energy can be used to simultaneously remove CO2 (and H2S) and produce H2 as side product. Biogas is thus scrubbed with catholyte and the captured HCO3− and HS− migrate towards the anode. Simultaneously, cathodic H2 mixes with residual biogas in a ratio that can be fine-tuned. We obtained in one step an ideal 4:1 H2:CO2 ratio in the reactor off gas. Subsequently the gas could be further upgraded via chemoautotrophic microbial conversion of CO2 to CH4. Biomethanation delivered biomethane with 98.9 ± 0.9% purity. The electrochemically-assisted scrubbing and stripping of CO2 and H2S resulted in high CO2 removal efficiencies (up to 100%), without addition of chemicals. The system was flexible depending on temporarily available power. Electrochemical biogas upgrading (EBU) can be envisaged as a scalable and decentralized storage of excess or off-peak renewable power, making better use of the power input used to drive a biological CO2 conversion.

Droplet-based microfluidic extraction is a promising way for effective lanthanides extraction due to its outstanding mass transfer performance. The separation process can be greatly enhanced with the droplet-based microfluidic extraction technique. However, the interactions between mass transfer, microfluidic dynamics and extraction kinetics are still unclear, which has hindered further manipulation on microfluidic extraction to boost extraction performance. In this study, the mechanisms of microfluidic droplet-based extraction and separation intensification of lanthanides are for the first time unveiled by using a numerical simulation model. The limiting factors for the performance of droplet-based microfluidic extraction are identified through a model-based parametric analysis. The numerical analyses provide a comprehensive understanding of droplet-based microfluidic extraction systems and offer operation and optimization guidelines for future research in this area.

With the technological advances in 3D printing technology, which are associated with ever-increasing printing resolution, additive manufacturing is now increasingly being used for rapid manufacturing of complex devices including microsystems development for laboratory applications. Personalized experimental devices or entire bioreactors of high complexity can be manufactured within few hours from start to finish. This study presents a customized 3D-printed micro bubble column reactor (3D-µBCR), which can be used for the cultivation of microorganisms (e.g., Saccharomyces cerevisiae) and allows online-monitoring of process parameters through integrated microsensor technology. The modular 3D-µBCR achieves rapid homogenization in less than 1 s and high oxygen transfer with kLa values up to 788 h−1 and is able to monitor biomass, pH, and DOT in the fluid phase, as well as CO2 and O2 in the gas phase. By extensive comparison of different reactor designs, the influence of the geometry on the resulting hydrodynamics was investigated. In order to quantify local flow patterns in the fluid, a three-dimensional and transient multiphase Computational Fluid Dynamics model was successfully developed and applied. The presented 3D-µBCR shows enormous potential for experimental parallelization and enables a high level of flexibility in reactor design, which can support versatile process development.

Liquid-phase adsorption has hardly been established in micro-flow, although this constitutes an industrially vital method for product separation. A micro-flow UV-photo isomerization process converts cis-cyclooctene partly into trans-cyclooctene, leaving an isomeric mixture. Trans-cyclooctene adsorption and thus separation was achieved in a fixed-bed micro-flow reactor, packed with AgNO3/SiO2 powder, while the cis-isomer stays in the flow. The closed-loop recycling-flow has been presented as systemic approach to enrich the trans-cyclooctene from its cis-isomer. In-flow adsorption in recycling-mode has hardly been reported so that a full theoretical study has been conducted. This insight is used to evaluate three process design options to reach an optimum yield of trans-cyclooctene. These differ firstly in the variation of the individual residence times in the reactor and separator, the additional process option of refreshing the adsorption column under use, and the periodicity of the recycle flow. ispartof: AICHE JOURNAL vol:67 issue:1 ispartof: location:United States status: published

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was performed in perfluoroalkoxy alkane capillary microreactors packed with a carbon-supported ruthenium (Ru/C) catalyst with an average particle diameter of 0.3 or 0.45 mm. The reaction was executed under an upstream gas–liquid slug flow with 1,4-dioxane as the solvent and H2 as the hydrogen donor in the gas phase. Operating conditions (i.e., flow rate and gas to liquid flow ratio, pressure, temperature and catalyst particle size) were varied in the microreactor to determine the influence of mass transfer and kinetic characteristics on the reaction performance. At 130 °C, 12 bar H2 and a weight hourly space velocity of the liquid feed (WHSV) of 3.0 gfeed/(gcat·h), 100% LA conversion and 84% GVL yield were obtained. Under the conditions tested (70–130 °C and 9–15 bar) the reaction rate was affected by mass transfer, given the notable effect of the mixture flow rate and catalyst particle size on the LA conversion and GVL yield at a certain WHSV. A microreactor model was developed by considering gas–liquid–solid mass transfer therein and the reaction kinetics estimated from the literature correlations and data. This model well describes the measured LA conversion for varying operating conditions, provided that the internal diffusion and kinetic rates were not considered rate limiting. Liquid–solid mass transfer of hydrogen towards the external catalyst surface was thus found dominant in most experiments. The developed model can aid in the further optimization of the Ru/C catalyzed levulinic acid hydrogenation in packed bed microreactors.

High throughput (HT) screening techniques for pressure-driven membrane processes allow simultaneous screening of multiple membrane samples under similar conditions, and are thus labour-, time- and consumables efficient. HT-modules have so far all been set-up in dead-end configuration. A new filtration set-up for cross-flow filtration has now been designed, allowing to simultaneously perform 16 pressure-driven separations with a membrane surface of 15 cm² each. The potential of the developed equipment and of the HT-screening concept in general was validated by demonstrating the reliability and reproducibility of the measurement of membrane performances, and by comparing flow simulations and experimental data. These data were obtained with 2 types of commercially available membrane: a nanofiltration membrane (NF 270, DowDuPont, USA) and a reverse osmosis membrane 73AC-UTC (Toray Industries Inc., Japan). Additionally, the flow-regime inside the cross-flow channel was studied by varying the hydrodynamic parameters and by applying feed spacers. The reproducibility of the data proved that this HT-approach can be a useful tool to rapidly screen a large array of operational parameters in membrane processes.

We reported experimental measurements of the diffusion coefficient of methane at effectively infinite dilution in methylbenzene and in heptane at temperatures ranging from (323 to 398) K and at pressures up to 65 MPa. The Taylor dispersion method was used and the overall combined standard relative uncertainty was 2.3%. The experimental diffusion coefficients were correlated with a simple empirical model as well as the Stokes–Einstein model with the effective hydrodynamic radius of methane depending linearly upon the solvent density. The new data address key gaps in the literature and may facilitate the development of an improved predictive model for the diffusion coefficients of dilute gaseous solutes in hydrocarbon liquids.

Maintaining chemical and physical stability of the product during freeze-drying is important but challenging. In addition, freeze-drying is typically associated with long process times. Therefore, mechanistic models have been developed to maximize drying efficiency without altering the chemical or physical stability of the product. Dried product mass transfer resistance ( R p ) is a critical input for these mechanistic models. Currently available techniques to determine R p only provide an estimation of the mean R p and do not allow measuring and determining essential local (i.e., intra-vial) R p differences. In this study, we present an analytical method, based on four-dimensional micro-computed tomography (4D- &mu, CT), which enables the possibility to determine intra-vial R p differences. Subsequently, these obtained R p values are used in a mechanistic model to predict the drying time distribution of a spin-frozen vial. Finally, this predicted primary drying time distribution is experimentally verified via thermal imaging during drying. It was further found during this study that 4D- &mu, CT uniquely allows measuring and determining other essential freeze-drying process parameters such as the moving direction(s) of the sublimation front and frozen product layer thickness, which allows gaining accurate process knowledge. To conclude, the study reveals that the variation in the end of primary drying time of a single vial could be predicted accurately using 4D- &mu, CT as similar results were found during the verification using thermal imaging.

A catalyst preparation method, consisting of slurry washcoating with γ-Al2O3 followed by impregnating platinum on the microreactor walls, has been investigated. The effect of various factors in the preparation procedures on the adhesion of the washcoated γ-Al2O3 was studied, including the slurry property (i.e., the binder type, concentration and molecular weight, γ-Al2O3 concentration and particle size, pH), and the (micro)reactor substrate and channel shape. The results show that the adhesion of γ-Al2O3 washcoat strongly depended on the slurry rheological characteristics. A good adhesion on FeCrAlloy substrates was obtained using the slurry with polyvinyl alcohol as the binder (typical concentration at 3–5 wt% and molecular weight of 57,000–186,000), 20 wt% γ-Al2O3 (particle size being around 3 µm) and pH = 3.5. FeCrAlloy as the substrate exhibited an excellent coating adhesion in rectangular or round channels, primarily due to the formation of alumina film over the surface during thermal pretreatment. The aluminum-free stainless steel as the substrate only showed a good adhesion in a round channel. Well-adhered Pt/γ-Al2O3 catalysts were then applied in a microreactor comprising parallelized microchannels made of FeCrAlloy under the optimized coating procedures, and investigated in terms of its performance in the catalytic methane combustion. It is shown that the reaction temperature has a greater influence on the methane conversion than the flow rate, and a favorable coverage of methane and oxygen on the catalyst surface is essential to obtain a good catalytic performance. These reaction results are in line with the temperature behavior measured along the microreactor.

An optimized design for a 210 kg alloy, Ti-Mn alloy based hydrogen storage system for stationary application is presented. A majority of the studies on metal hydride hydrogen systems reported in literature are based on system scale less than 10 kg, leaving questions on the design and performance of large-scale systems unanswered. On the basis of sensitivity to various design and operating parameters such as thermal conductivity, porosity, heat transfer coefficient etc., a comprehensive design methodology is suggested. Following a series of performance analyses, a multi-tubular shell and tube type storage system is selected for the present application which completes the absorption process in 900 s and the desorption process in 2000 s at a system gravimetric capacity of 0.7% which is a vast improvement over similar studies. The study also indicates that after fifty percent reaction completion, heat transfer ceases to be the major controlling factor in the reaction. This could help prevent over-designing systems on the basis of heat transfer, and ensure optimum system weight. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

International audience; A fixed volume packed column was simulated for the absorption at counter-current of four more or less hydrophobic volatile organic compounds (VOCs) in water and in two heavy organic solvents (PDMS 50, a silicone oil) and DEHA (Bis(2-ethylhexyl) adipate). Reliable values of the mass-transfer coefficients were deduced allowing to calculate the VOCs removal efficiency. Disappointing performances in heavy solvents, lower than 60% for isopropanol and acetone, were computed in a 3 m height column and using mild conditions (atmospheric pressure and a liquid-to-gas mass flow rate ratio around 2). However, toluene removal efficiencies higher than 90% were simulated. (C) 2017 The Korean Society of Industrial and Engineering Chemistry.

Product yield optimization in bimodal reaction sequences including degradation has been performed considering three-phase reactors such as the jet loop and trickle bed reactors. The considered reaction network comprises two consecutive homogeneous reaction steps toward intermediates which are converted to the corresponding final products by heterogeneously catalyzed reactions, while the reactant and these intermediates are susceptible to irreversible degradation. In the jet loop reactor, the so-called “homogeneous product” is the main product; hence, the remaining challenge is the reduction of degradation. For the trickle bed reactor, gas−liquid mass phase transfer plays a very pronounced role in its ultimate performance. Higher gas flow rates may be employed in the trickle bed reactor to overcome potential mass-transfer limitations and selectively form the “heterogeneous product”. Lower gas flow rates result in a less effective gas dissolution, and product selectivities change toward the homogeneous product, rendering avoiding degradation difficult.

Heterogeneous catalytic epoxidation of propene to propene oxide with hydrogen peroxide as oxidant was investigated in a confined Taylor flow (CTF) reactor, a continuous monolith reactor, containing a long alumina rod coated with titanium silicalite (TS-1) catalyst in the centre of the reactor column. The effect of gas and liquid superficial velocity on the hydrodynamics of CTF reactor was also investigated under Taylor flow regime at atmospheric pressure. The variation of hydrodynamics had a profound impact on the production of propene oxide. When liquid superficial velocity was constant, the concentration of propene oxide produced decreased with increasing gas superficial velocity as Taylor bubble length and bubble rise velocity increase. However, when gas superficial velocity was constant, the concentration of propene oxide produced had no linear dependency on liquid superficial velocity as Taylor bubble length decreases but bubble rise velocity increases.

Mass-transfer coefficients between an electrolyte solution and the wall of a hydrocyclone were experimentally determined by using the electrochemical technique. The local mass-transfer coefficients were measured as a function of the axial distance from the entrance changing the inlet volumetric flow rate and the underflow stream. An enhancement of mass-transfer was observed in comparison to that predicted for developing axial flow in an annular duct, being the cylindrical part more active than the conical one. The global mass-transfer coefficient in the cylindrical region depends on the Reynolds number raised to an exponent of 0.79, in accordance with the mass-transfer behavior of decaying annular swirl flow. The modified hydrocyclone was also examined for the removal of copper from dilute synthetic solutions. A diminution of copper concentration from 400 ppm to 40 ppm was achieved after 60 minutes of electrolysis in a recirculating system and the contaminant was recovered as a metal powder separated by the hydrocyclone. The space time yield and the specific energy consumption were 12.5 kg m-3 h-1 and 4.9 kWh kg-1, respectively, with a cumulative current efficiency of 54%, showing that the modified hydrocyclone is a suitable reactor for the electrochemical treatment of effluents. Fil: Resio, L. C.. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina Fil: Gonzalez Perez, Omar. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Bisang, Jose Maria. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina

For practical applications the Euler-Euler two-fluid model relies on suitable closure relations describing interfacial exchange processes. Concerning pure fluid dynamics of dispersed gas-liquid multiphase flow, an ongoing effort has led to a validated set of closures that is applicable under a rather broad range of conditions. Similar results for the technologically even more important field of mass transfer remain to be achieved. Progress so far has been hampered by a lack of spatially resolved data including measurements of concentration, which are suitable for CFD model validation. In addition, correlations proposed to describe the mass transfer coefficient differ widely. Here, a preliminary study of axial concentration profiles in a bubble column is given, based on the available experimental data found in the literature. For this purpose the simplified assumption of a constant mass transfer coefficient throughout the column is made and experimentally determined values are used. New measurements will be needed to come to a final conclusion.

openaire: EC/H2020/788489/EU//BioELCell The prediction of the morphology of wet-spun fibers has so far been only possible by complex and experimentally intensive approaches that include the construction of ternary phase diagrams. Ultimately, however, the available models give approximate information. Here we propose an alternative predictive approach that uses design principles based on the combination of (1) relative energy difference (RED) of Hansen solubility and (2) a kinetic parameter "T" that considers mass transfer effects. Such a model is applied and experimentally validated for a priori determination of the diameter and internal morphology of wet-spun fibers. Remarkably, only three. variables relevant to wet-spinning are needed, namely, the choice of polymer, solvent, and nonsolvent types. A combination of systems is tested, and the morphology of the obtained fibers is determined via electron microscopy. Aspects related to demixing, internal specific surface area (BET), and layer formation on the fibers are described qualitatively. The facile implementation of the design parameters is further confirmed through comparison with data published on the subject. Our proposed model is expected to accelerate future developments in nanomaterials, especially in the context of ongoing efforts related to fiber spinning with biopolymers.

International audience; This study focuses on Butyraldehyde (C4H8O) degradation using catalytic ozonation oriented to the optimization of non-thermal plasma/photocatalytic coupled processes. After the first oxidation by non-thermal plasma coupled photocatalytic processes, a second oxidative step leading to the decomposition of the residual Butyraldehyde by Ozone is catalyzed by Mordenite, ZSM-5 and γ-alumina. The Butyraldehyde degradation in the presence of Ozone under operational parameters such as plasma energy, Butyraldehyde inlet concentration, relative humidity and the height of the catalytic bed are reported in detail. The optimum operating conditions found were Qair = 1 m3 h-1, [C4H8O] = 100 mg m-3, SIEplasma = 18 JL-1, for Butyraldehyde degradation mediated by ZSM-5. The formation of intermediate by-products was monitored during the degradation of Butyraldehyde in the presence of Ozone and ZSM-5 catalyst to suggest a degradation pathway. The coupling of catalytic ozonation by non-thermal plasma/photocatalysis lead to the total decomposition of Ozone when catalyzed by ZSM-5and presents a positive effect on the mineralization capacity. The pollutants degradation intermediates were identified by GC-MS and the oxidative states on the catalytic bed were characterized by XPS. © 2018 Elsevier B.V.

This work investigates the effect of current density on the hydrogen gas bubble formation during electrolysis on a platinum electrode. Local detection of bubble evolution was performed electrochemically by using a hydrogen-collecting microelectrode placed in close proximity of a larger hydrogen-generating platinum electrode. The micro-electrode probe locally measured the concentration of dissolved molecular hydrogen produced during electrolysis. In acidic conditions, it was found that at low electrolysis currents the concentration of dissolved hydrogen could temporarily rise up to 50 times the saturation level, while once a large current was reached, the concentration dropped, increasing the concentration of hydrogen inside gas bubbles, and became independent of the current. Through laser reflectance, the onset of bubble formation was found (similar to-0.7 mA/cm(2)), which was lower than the first bubble observable by naked eye or detected by the microelectrode probe.

The oxidation of ferrous ions in acidic sulfate solutions in the presence of cupric ions at elevated air pressures was investigated in a high-intensity gas-liquid contactor. The study was required for the design of the regeneration steps of the novel Vitrisol((R)) desulphurization process. The effects of the Fe2+ concentration, Cu2+ concentration, Fe3+ concentration, initial H2SO4 concentration, and partial oxygen pressure on the reaction rate were determined at three different temperatures, i.e., T=50 degrees C, 70 degrees C, and 90 degrees C. Most of the experiments were determined to be affected by the mass transfer of oxygen, and therefore true intrinsic kinetics could not be fully determined. An increase in Fe2+ and Cu2+ concentrations, as well as the partial pressure of oxygen and temperature, increased the Fe2+ oxidation rate. H2SO4 did not influence the Fe2+ oxidation rate. An increase in Fe3+ concentration decreased the Fe2+ oxidation rate. Although determined from experiments partially affected by mass transfer, a first order of reaction in Fe2+ was observed, fractional orders in both Cu2+ and O-2 were measured, a zero order in H2SO4 was determined, and a negative, fractional order in Fe3+ was obtained. The activation energy was estimated to be 31.3kJ/mol.

Models proposed to describe the liquid side mass transfer coefficient in absorption processes differ widely in such basic questions as on which of the local flow variables they are based. Comparison of different alternatives with experimental data taken from the literature suggests that there are two basic mechanisms, a laminar and a turbulent one, each of which dominates under suitable conditions. A dimensionless number that allows to identify the corresponding regimes is suggested together with a preliminary model encompassing both. New experiments will be needed to come to a final conclusion.

Solvent extraction is a key principle for separations of components often requiring relatively large separation times due to large droplet size distributions. A continuous mesoflow reactor setup was evaluated for solvent extraction and phase separation in terms of efficiency of Co/Ni separation with cyanex 272 as extractant in a kerosene mixture. Several mixer types have been evaluated for the solvent extraction capability combined with a thin film coalescer/separator, expediting separation times, resulting in a settling volume that was only 1-2 times the volume of the mixer effectively reducing total residence time compared to classic mixer-settlers, where the ratio is 4-8 times higher. This was mainly attributed to the droplet homogeneity generated in the mixer, resulting is a short separation time. The thin film coalescer partitions in the settler expedited the phase separation further reducing the required settler volume. This paper shows that continuous mesoflow reactor setups can be utilized for small-scale liquid extractions with narrowly defined droplet sizes, enhancing the phase separation time, making it a viable screening utility. It also shows that the useful volume is much higher than those for conventional mixer-settler with a phase-separation-volume-to-equilibrium-volume ratio of 1-2 compared to 4-8 for the conventional mixer-settler expediting parameter screening. (C) 2016 Elsevier B.V. All rights reserved.

In the present paper, the impact of the acid concentration, Cyanex 272 concentration, and membrane wetting properties on the stripping kinetics of loaded Cyanex 272 with cobalt is studied in a flat membrane microcontactor. To reduce the environmental impact and to be ever economically viable, the extractant needs to be regenerated. From the observed results, a model was derived to describe the stripping kinetics, enabling to maximize throughput. Like for the extraction of cobalt, also for the reversed reaction (stripping of loaded Cyanex 272 with cobalt), pseudo-first order kinetics could be assumed. However, unlike the extraction of cobalt, the reaction kinetics for the stripping of loaded Cyanex 272 had to be taken into account. As a consequence, the concentration of sulphuric acid influences the stripping kinetics and consequently throughput as well. Furthermore, it was also shown that the concentration of Cyanex 272 affected the stripping rate, in contrast to the extraction of cobalt. While for extractiondiffusion in the organic phase can be neglected, this was no longer the case for stripping. When the concentration of Cyanex 272 was increased, the stripping rate decreased severely. To increase throughput, a scale-up strategy was proposed, that could realize without inducing a loss of efficiency. This was demonstrated by increasing throughput by a tenfold. Moreover, also the separation efficiency is studied in a continuous operation set-up over a span of 5 h. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Three commercial spiral-wound membrane modules of different sizes, from 1.8″ × 12″ to 4.0″ × 40″, are used to concentrate a solution of sucrose octaacetate in ethyl acetate under different operating conditions. A mathematical model to describe the batch concentration process is developed, based on a combination of the classical solution diffusion membrane transport model and the film theory, to account for the mass transfer effects. The model was implemented using the “OSN Designer” software tool. The membrane transport model parameters as well as all parameters in the pressure drop and mass transfer correlations for the spiral-wound modules were obtained from regression on a limited number of experimental data at steady state conditions. Excellent agreement was found between the experimental and multi-scale modelling performance data under various operating conditions. The results illustrate that the performance of a large scale batch concentration process with spiral-wound membrane modules can be predicted based on laboratory crossflow flat sheet test data when the fluid dynamics and mass transfer characteristics in the module, and the necessary channel geometry are known. In addition, the effects of concentration polarisation, pressure drop through feed and permeate channels, and thermodynamic non-ideality of the solution at large scale batch concentration are also investigated.

International audience; A simple dynamic absorption procedure to assess the mass-transfer performances of a solvent toward a selected gaseous solute is presented. Absorption was operated semi-continuously at transient state until the equilibrium was reached without solvent recirculation. Four volatile organic compounds (VOC) more or less hydrophobic (toluene, acetone, dichloromethane, isopropanol) were absorbed in water and two heavy organic solvents (Bis(2-ethylhexyl) adipate DEHA and polydimethylsiloxane PDMS). A numerical resolution procedure was developed to simulate the gas-liquid mass-transfer and to deduce the VOC partition coefficients, expressed as the Henry’s law constants, as well as the overall liquid-phase mass-transfer coefficients. The overall liquid-phase mass-transfer coefficients were correlated to the diffusion coefficients using the Higbie penetration theory. The results confirm the high selectivity of water whereas the two organic solvents, especially DEHA, exhibit rather good affinity with all VOC even if the Henry’s law constants of the most soluble and the less soluble compounds for those solvents differ by 1 or 2 orders of magnitude. The liquid-film mass-transfer coefficients in the two organic solvents, even being more viscous, are larger than in water which confirms their good potential for hydrophobic VOC treatment.

The individual factors that determine the kinetic performance (B- and C-term band broadening and bed permeability K-v) of radially elongated pillar (REP) columns are studied. To this end, columns with REPs having 4 different aspect ratios (AR = 9, 12, 15, 20) were characterized experimentally and by means of numerical simulations. A tortuosity and retention based plate height equation was established, enabling a good global fit for all studied conditions. The B-term plate height contribution appears to decrease with a factor equaling the square of the flow path tortuosity tau. Going from AR= 12 to AR= 20 (tau = 5.7 and tau = 9.0 respectively), this resulted in a shift in plate height expressed in axial coordinates from H-min =0.42 mu m to H-min = 0.25 for non-retained conditions and from H = 0.77 mu m to H = 0.57 mu m for a component with k = 1.0. The obtained parameters were combined to predict optimal time-efficiency combinations for all possible channel lengths. This revealed an efficiency limit of N = 10(7) plates for a non-retained component and N = 7-8 x 10(6) for k=1 for a channel with an AR= 20, corresponding to a channel length of 2.5 m and a void time of 2.4h. (C) 2016 Elsevier B.V. All rights reserved.

A continuous-flow adsorption/desorption process for the recovery of phenolic compounds (PCs) from olive mill wastewaters (OMWs) was developed in a 0.53 m packed column, using a previously selected resin (Amberlite XAD16) and an actual OMW. The main goals of the study were (i) to evaluate the PC adsorption/desorption performances of XAD16 by means of adsorption isotherms and adsorption/desorption breakthrough tests, and (ii) to develop a reliable model of the process. A combination of centrifugation and microfiltration resulted necessary to attain a high suspended solid removal (98.5%) and thus avoid clogging of the packed bed. The quality of two packing procedures was evaluated by means of frontal analysis tests. XAD16 performed well in terms of both adsorption yield at 20% breakthrough (87–88%) and PC/COD selectivity (PC/COD adsorption constant = 7–9). The desorption solvent (acidified ethanol) was effectively regenerated by vacuum distillation. The adsorption breakthrough curves were successfully simulated with a 1-D convection/dispersion model with mass-transfer (R2 = 0.95–0.99; kLa = 0.8–2.5 · 10−3 1/s), whereas an equilibrium adsorption model with dispersion failed to predict the experimental data. In the perspective of a process scale-up, the simulation of the best-performing operational condition was used to evaluate the process performances for different column lengths (0.5–10 m). A precise and automated HPLC method for total PC measurement was developed and compared to the traditional Folin–Ciocalteu methodology. Further research is needed to optimize the desorption step, to scale up the process and to evaluate the long-term resin performances.

Falling film reactors represent the actual technology to run sulfonation reaction at pilot and industrial scale. The reaction is characterized by high thermal tenor, thus realizing a liquid reactive film flowing directly downwards on the internal reactor wall, it benefits of high heat exchange to the external jacket. The scale-up of such reactors is straightforward as it consists mainly on increasing the pipe numbers, with heat exchanger shell/pipe architecture. The main problem of this reactor solution is its modelling. The fluid-dynamics is complex to be fully described and the few models proposed in the literature lacks in rigorousness. The aim of the present work is the realization of a detailed reactor model able to describe sulfonation reaction in a falling film reactor. The simulations were compared with data collected on a pilot-plant.

In this study, photoactive CuxO/TiO2 coatings were prepared using magnetron sputtering operated at different powers and modes (Direct-current magnetron sputtering and High Power Impulse magnetron sputtering). Indoor/outdoor air pollutions (Volatile Organic Compounds, VOCs) degradation have been dramatically reduced on sputtered CuxO/TiO2 on polyester (PES) cloth under low intensity visible light. The Low intensity visible light was used to irradiate the sputtered photocatalysts, which degraded various VOC molecules concomitant with a bacterial inactivation ability. The VOC removal kinetics were studied in the dark and under visible light as a function of the deposition time and applied peak currents during the coating by HiPIMS. High concentrations of chloroform and butyraldehyde were shown to be degraded (90% and 85%, respectively) on CuxO/TiO2-PES fabrics under daylight irradiation. The repetitive reuse of the sputtered coatings was also investigated showing the long operational lifetime of the prepared fabrics. The deposition rates of Ti and Cu atoms and their atomic distribution along the sputtered film have been investigated by Transmission Electronic Microscopy (TEM). Redox catalysis was shown to happen within the VOC degradation time as detected by X-ray Photoelectron Spectroscopy (XPS). Deconvolution of the Cu2p3/2 peak in the CuxO/TiO2 on PES samples showed changes in the Cu2O and CuO within the VOCs degradation and the bacterial inactivation. The interfacial charge transfer (IFCT) between CuxO induced under light leading to VOCs oxidation path seemed to require a low photons energy and were able to oxidize the pollutants even at high concentrations. The mechanisms involving the VOCs degradation on CuxO/TiO2 catalysts are suggested in which the holes generated by Cu2O transfer to TiO2 in the TiO2 (n)/CuxO(p) in the hetero-junction. This transfer is favored by the electrostatic interaction between both semiconductors. The photo-generated ROS, mainly (OH)-O-center dot-radicals were determined by fluorescence method. The possible contribution of the (OH)-O-center dot-radicals in the bacterial inactivation on the sputtered CuxO/TiO2 catalysts was discussed. DRS, TEM, contact angle (CA) and XPS were used to characterize the catalyst optical and structural properties.

Reactive chromatography is a special topic in chemical reaction engineering, consisting of the combination of chemical reaction and chromatographic separation. The main idea is to avoid a further separation unit, by performing reaction and separation in one unique equipment, allowing process intensification. This technology is usually applied in hydrolysis (or esterification) reactions, that undergoes through the reaching of chemical equilibrium. The chromatographic reactor application would lead to complete conversion, by separating reactants and products as the reaction proceeds. Modelling is certainly a delicate issue for chromatographic reactor to optimize the operation conditions, thus different approaches were published. The aim of the present work is to show a novel chromatographic reactor model, were all the physical and chemical phenomena involved and described by a rigorous approach. The fluid-dynamics was treated by axial dispersion approach, and the Peclet number values were obtained from dedicated experiments. The external fluid-solid mass transfer was calculated from existing correlations, demonstrating to be negligible for the modelled chromatographic reactor. The intraparticle mass diffusion was assumed to be the sum of two parallel contributions, i.e. porous and surface diffusivity. The model was tested on literature data for methyl acetate hydrolysis experiments with satisfactory results, obtaining reliable values of the surface diffusivity. A sensitivity analysis was conducted highlighting that the model can predict complete ester conversion and product separation.

As excessive foam formation is undesirable from an operational perspective in the ammonia stripping process of anaerobic digested slurry, the effect of alkaline agents on foam production was first evaluated by comparing two pH adjusters (NaOH and CaO). Results show that increased pH via CaO addition can significantly aggravate foam production and restrain defoaming ability during the stripping of anaerobic digestion effluent. The addition of 0.75% normal silicone oil (NSO) or 0.01% polyether-modified silicone oil (PMSO) as antifoam reduced foam capacity by 56.2 ± 2.5% and 75.2 ± 2.7%, respectively, but only works in a slurry with pH adjusted by NaOH, not by CaO. Moreover, the addition of these antifoams led to 4.31% (0.75% NSO) and 5.38% (0.01% PMSO) NH4+-N removal efficiency abatement during the stripping process. Finally, a new high-temperature, neutral (without pH adjustment) stripping strategy is proposed in this study, because it can effectively mitigate the formation of foam and maintain equalized ammonia removal. The effluent discharged via this stripping concept can be handled easily and does not cause heavy negative impacts from the residual alkaline content. Furthermore, the ammonia loss in the preparation phase before stripping was only 1/3 that in the traditionally high-pH stripping, indicating the potential of this new mitigation strategy in the frame of an environmentally friendly development.

This work presents numerical simulations, with validation considering analytical expressions and experimental results, of masstransfer in electrochemical reactors under laminar and turbulent flows in ducts of rectangular and tubular shape. Sudden expansion at the reactor inlet and segmented electrodes are also analyzed. Computational fluid dynamics (CFD) simulations were performed solving the laminar or RANS equations with the Shear Stress Transport (SST) k-ω turbulence model using the open source code OpenFOAMin steady-state. For mass-transfer simulations, the averaged diffusion-convection equation was implemented and solved. A good agreement between mass-transfer simulations with experimental data and analytical results were attained for both laminar and turbulent flow. Discussions about the segmented electrode technique in order to obtain local mass-transfer data in laminar and turbulent flow are also performed. Fil: Colli, Alejandro Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Bisang, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina

The dissolution of a gas bubble in a confined geometry is a problem of interest in technological applications such as microfluidics or carbon sequestration, as well as in many natural flows of interest in geophysics. While the dissolution of spherical or sessile bubbles has received considerable attention in the literature, the case of a two-dimensional bubble in a Hele-Shaw cell, which constitutes perhaps the simplest possible confined configuration, has been comparatively less studied. Here, we use planar laser-induced fluorescence to experimentally investigate the diffusion-driven transport of dissolved CO2 that propagates from a cylindrical mm-sized bubble in air-saturated water confined in a horizontal Hele-Shawcell. We observe that the radial trajectory of an isoconcentration front, r(f) (t), evolves in time as approximately r(f) - R-0 alpha root t, where R-0 denotes the initial bubble radius. We then characterize the unsteady CO2 concentration field via two simple analytical models, which are then validated against a numerical simulation. The first model treats the bubble as an instantaneous line source of CO2, whereas the second assumes a constant interfacial concentration. Finally, we provide an analogous Epstein-Plesset equation with the intent of predicting the dissolution rate of a cylindrical bubble. We acknowledge the support of the Spanish Ministry of Economy and Competitiveness through Grants No. DPI2014-59292-C3-1-P and No. DPI2015-71901-REDT, partly funded through European Funds.

International audience; The purpose of this paper is to study the butyraldehyde (Buty) conversion using dielectric barrier discharge (DBD) in a continuous reactor at pilot scale. One of the focused-on parameters in this study is relative humidity, which effect on (i) butyraldehyde removal (ii) selectivity of CO2 and CO, and (iii) intermediate byproducts and ozone formation was investigated using a DBD reactor with planar configuration. The results showed that at pilot scale, adding a small amount of water vapor in air enhances the processes performance and 10% increase in Buty removal efficiency was observed. A kinetic degradation model was also proposed, which takes into account the relative humidity influence. Active species due to water dissociation are integrated in the model. To represent the chemical degradation pathway, we supposed, in a first step, that an equivalent intermediate compound (EI) is formed directly from Buty. Then, in a second step, this EI is oxidized by active species into CO2 and CO in the discharge zone. This approach that also considers the competition effect between actives species improved the concordance between simulated results and experiments with a satisfactory overall description of the degradation and byproducts formation. (C) 2016 Elsevier B.V. All rights reserved.

A model for ionic and electronic grain boundary transport through thin films, scales or membranes with columnar grain structure is introduced. The grain structure is idealized as a lattice of identical hexagonal cells – a honeycomb pattern. Reactions with the environment constitute the boundary conditions and drive the transport between the surfaces. Time-dependent simulations solving the Poisson equation self-consistently with the Nernst-Planck flux equations for the mobile species are performed. In the resulting Poisson-Nernst-Planck system of equations, the electrostatic potential is obtained from the Poisson equation in its integral form by summation. The model is used to interpret alumina membrane oxygen permeation experiments, in which different oxygen gas pressures are applied at opposite membrane surfaces and the resulting flux of oxygen molecules through the membrane is measured. Simulation results involving four mobile species, charged aluminum and oxygen vacancies, electrons, and holes, provide a complete description of the measurements and insight into the microscopic processes underpinning the oxygen permeation of the membrane. Most notably, the hypothesized transition between p-type and n-type ionic conductivity of the alumina grain boundaries as a function of the applied oxygen gas pressure is observed in the simulations. The range of validity of a simple analytic model for the oxygen permeation rate, similar to the Wagner theory of metal oxidation, is quantified by comparison to the numeric simulations. The three-dimensional model we develop here is readily adaptable to problems such as transport in a solid state electrode, or corrosion scale growth.

International audience; In this study, a continuous process combining plasma and photocatalysis, at pilot scale, has been investigated on pollution treatment. The degradation efficiency and by-products formation has been monitored through the variation of multiple parameters such as inlet concentration, specific energy, and residence time. Results show that process combination leads to an enhancement of pollutant degradation compared to the separate systems even at high flow rate (250 m(3) h(-1)). Synergy factor due to this association ranged from 1.10 to 1.17. Furthermore, CO2 selectivity has significantly improved when comparing the combined system to that with plasma alone. Moreover, we note that adding a photocatalyst in the discharge zone leads to a reduction of ozone and CO formation compared to plasma process alone. Based on this investigation, a methodology of scaling up the combined system was proposed. Indeed, as a practical application, an industrial reactor has been developed and tested for treating a real pollution from animal quartering centers. This investigation indicates that the combined system of photocatalysis with plasma is a promising method for removing air pollutants.

Feed spacers are used in spiral wound reverse osmosis (RO) membrane modules to keep the membrane sheets apart as well as to enhance mixing. They are beneficial to membrane performance but at the expense of additional pressure loss. In this study, four types of feed spacer configurations are investigated, with a total of 20 geometric variations based on commercially available spacers and selected filament angles. The impact of feed spacer design on membrane performance is investigated by means of three-dimensional (3D) computational fluid dynamics (CFD) simulations, where the solution-diffusion model is employed for water and solute transport through RO membranes. Numerical simulation results show that, for the operating and geometric conditions examined, fully woven spacers outperform other spacer configurations in mitigating concentration polarisation (CP). When designed with a mesh angle of 60°, fully woven spacers also deliver the highest water flux, although the associated pressure drops are slightly higher than their nonwoven counterparts. Middle layer geometries with a mesh angle of 30° produce the lowest water flux. On the other hand, spacers with a mesh angle of 90° show the lowest pressure drop among all the filament arrangements examined. Furthermore, the computational model presented here can also be used to predict membrane performance for a given feed spacer type and geometry.

International audience; Three volatile organic compounds (VOC) with no acidic or basic function (butanol, butyraldehyde, methylethylketone), encountered at low concentrations in odorous effluents, were absorbed in water in a compact wet scrubber. This gas-liquid contactor consisted of a wire mesh packing structure where the gas phase flows at high velocity (>12 m s(-1)). A very turbulent two-phase downward flow could be observed in the scrubber with dispersed fine droplets (around 10 μm). For compounds showing a good affinity for water, such as butanol, removal efficiencies up to 90% were measured for a short contactor length of 32 cm leading to a gas residence time of 20 ms. However, the removal efficiency of butyraldehyde, which is poorly soluble in water, ranged between 10 and 30%. Mass-transfer modeling was achieved and underlined that working with several small scrubbers in series, fed with an unloaded solution, is effective to improve the removal efficiency. The influences of the VOC/solvent affinity, the contactor length, and the mass-transfer and hydrodynamic parameters on the removal efficiency were evaluated through a sensitivity analysis.

The performances of well-known porous metal/metalloid oxide adsorbents (zeolite 13X, zeolite 4A and silica gel) and less explored Engelhard titanosilicate ETS-10 for water adsorption heating systems (AHSs) were compared with the aid of computational modelling and simulations. The developed model contemplated adsorption equilibrium, one-dimensional heat and mass transfer in the bed, external heat transfer limitations, and intraparticle mass transport. The pair zeolite 13X/water seemed most promising for the AHS partly due to a higher amount of heat generated per cycle, and favourable water-adsorption isotherm features. Based on sensitivity studies, for zeolite particle diameters in the range 0.2-0.6 mm, the coefficient of performance was 1.48 and the specific heating power was in the range 1141-1254 W Kg(s)(-1) Aiming at inferior computational and numerical efforts, the impact of considering some simplified postulations (e.g. constant thermal conductivity of the adsorbent; constant isosteric heat of adsorption; constant linear driving force coefficient), while ensuring comparable predictions of the performances of the AHSs, was successfully investigated. (C) 2016 Elsevier Ltd. All rights reserved.

The advent of technology and development has led to a surge in energy demands by both developing and developed nations. Since 2000, the energy usage pattern in India has doubled. The majority of the power sector is dependent on the fossil fuel sources for energy generation. While energy generation is of prime concern the storage and retrieval with minimum losses is also significant. The packed beds system form a significant part of the solar power systems which are used to store energy during day time and retrieve it during the night. The present work investigates on the issues related to energy storage capability in packed beds. In the present work, volumetric heat transfer coefficient is measured using a transient technique in packed beds with uniformly sized spheres. The experiments are conducted for bed to particle diameter ratios of 5, 10 and 21. The temperatures inside the packed bed are measured at four axial locations with thermocouples placed inside the spheres and positioned 112 mm apart along the central axis. The temperatures are measured at four radial locations 5, 10, 15 and 20 mm apart from the solid wall along different axial planes from the entry of packing. The experimental results are compared with Schumann's curves and the volumetric heat transfer coefficient is estimated. It is found that the estimated volumetric heat transfer coefficient (h(v)) is higher for smaller particle diameter 2.38 mm as compared to larger diameter spheres with random packing. There is an increase in the volumetric heat transfer coefficient (h(v)) with the increase in the particle Reynolds number. (C) 2016 Elsevier Masson SAS. All rights reserved.

Microporous stannosilicate AV-6 was investigated for cadmium(II) removal from aqueous solutions in batch experiments. Ion exchange equilibrium of the Cd2+/K+/AV-6 system was modeled using the mass action law combined with activity coefficient models for the solution (ideal, Debye-Htickel and Pitzer equations) and for the solid (Wilson equation) with absolute average relative deviations (AARDs) between 6.56% and 6.75%. It was concluded that the system embodies strong intraparticle non-idealities, namely solid activity coefficients between 0.2602 and 0.7180 for Cd2+. The kinetics of cadmium(II) sorption was analyzed measuring removal curves and modeling the data with pseudo-first and pseudo-second order expressions, commonly adopted in the literature, and with Maxwell-Stefan (MS) and Nernst-Plank (NP) based models. The best results were achieved by MS and NP approaches, for which AARD was 3.74% and 3.71%, respectively. The kinetic performance of the ion exchange was also discussed taking into account structural aspects of the AV-6 material. (C) 2016 Elsevier B.V. All rights reserved.

An a priori prediction of multiphase flow pattern in micro-capillaries or microstructured reactors (MSR) is required for their rational design. The state-of-the-art numerical models require huge computational efforts. In the present work, an analytical model based on flow stability analysis has been applied to study the flow patterns in MSR. In order to simplify the task, a coaxial capillary geometry was chosen as a model of MSR and the two-phase flow was characterized in terms of the rate of perturbation in relation to the axial velocity. Liquid-liquid flow experiments were carried out in glass micro-capillary equipped with high-speed camera under various operating conditions such as flow velocity, flow ratios and viscosity ratios. The volume of fluid (VOF) model by ANSYS Fluent software was applied to predict the flow pattern details numerically. The results obtained were consistent with the experimental observations. Finally, the experimental and simulation results were rationalized in terms of dimensionless numbers allowing simple a priori prediction of the flow pattern in MSR. (C) 2012 Elsevier Ltd. All rights reserved.

Emulsification using electric fields is an easy alternative to flow-induced drop breakup, and the former is reported to be more effective and economical than the latter, especially when the medium phase is poorly conducting and highly viscous. The emulsification of a coarse water-in-oil emulsion in a uniform electric field is studied. We perform a detailed experimental analysis of the effect of applied electric field strength and the duration of applied electric field on the drop size distribution. The average diameter as well as the time for emulsification decreases with an increase in the intensity of the electric field. Moreover, a narrow size distribution is observed. An average size of a few microns of the dispersed phase could be achieved. New breakup mechanisms at play in the emulsification process are discussed. Identified mechanisms involve charged lobe disintegration, charged drop breakup, chain formation in which several water droplets are interconnected by thin water bridges, electrospraying and charge transfer, and coalescence. The study shows that charged drop disintegration could be the key mechanism of fine emulsification of an initially electrically neutral coarse emulsion.

A mathematical and numerical investigations on the gas–liquid absorption of carbon dioxide in monoethanolamine solutions in a hollow fiber membrane contactor device is described. The reactive absorption mechanism was built based on momentum and mass transport conservation laws in all three compartments involved in the process, i.e., the gas phase, the membrane barrier, and the liquid phase. The liquid absorbing solution flows in the fiber bore in which the velocity is assumed to obey a fully developed laminar flow, and the gas mixture circulates counter-currently to the liquid flow in the shell side where the velocity is characterized by the Navier-Stokes momentum balance equations. The average outlet gas and liquid concentrations, the reactive absorption flux, and the gas removal efficiencies are parametrically simulated with operational parameters such as gas flow rate, fresh inlet amine concentrations, and fiber geometrical characteristics. The shell velocity was described by other flow hydrodynamics models besides Navier-Stokes and their simulated results were favorably compared to experimental data. © 2011 American Institute of Chemical Engineers AIChE J, 2012

International audience; The adsorption of toluene (TOL) as a target volatile organic compound has been studied experimentally and modelled on various hydrophobic zeolites: Faujasite (FAU), ZSM-5 (Z) and Mordenite (MOR). The influence of the nature of the compensating cation (H+ or Na+) has also been investigated for ZSM-5 zeolite, which is known to possess three kinds of adsorption sites (sinusoidal channels, straight channels and intersections). Type I isotherms observed on FAU, Na-Z and MOR fitted well with the Langmuir model. A deviation from a type I isotherm was observed for H-Z, because of the structure of this zeolite. The Successive Langmuir Model was more successful to fit the ‘bump’ of the experimental curve than the Double Langmuir. Classical shapes were found for MOR, FAU and Na-Z breakthrough curves that were fitted with good accuracy using the Linear Driving Force (LDF) approximation. In the case of H-Z, a change of profile was observed during the dynamic adsorption and the differences seen between the Na-Z and H-Z behaviours were explained by the strong interactions between Na+ and adsorbed TOL at the intersection sites. The Na+ cations prevented reorientation of TOL molecules at the intersection and thereby avoided the filling of the sinusoidal channel segments. Thus, a specific model was developed for fitting the breakthrough curve of H-Z. The model developed took into account these two types of adsorption sites with the overall uptake for each site being given by an LDF approximation.

This work focuses on the use of ionic liquids as alternative solvents for the removal of thiols, at room-temperature, from n-dodecane used as jet fuel model stream. The model extraction system composed by a selected ionic liquid, the thiol to be removed and an alkane representative of the jet-fuel, show high selectivities and low distribution ratios, which makes unfeasible the use of conventional liquid-liquid extraction processes due to the high volume of ionic liquid required. This works evaluates the use of supported ionic liquid membranes (SILMs) for the selective removal of thiols applying vacuum in the downstream side. This approach consists in the incorporation of the ionic liquid inside the membrane pores, while due to the vacuum applied, the thiol compound is scrubbed. To study the target solute transport from the feed to the ionic liquid, extraction experiments were carried out using different 1-ethyl-3-methylimidazlium cation-based ionic liquids. The mass transfer resistance was found to be higher in the ionic liquid phase, which results mainly from the high ionic liquid viscosities, hindering the thiol transport. The SILMs stability was investigated by evaluating different membrane supports, with the various ionic liquids selected for study. The results obtained show that the ionic liquids were properly incorporated inside the pores of the membrane support. However, and despite the negligible mutual solubility between n-dodecane and the studied ionic liquids, n-dodecane permeation through the membrane support was found to be undesirably high. This problem was solved by using a membrane contactor with polypropylene hollow fibre membranes, not wetted by the ionic liquid, which receives the thiol compound transported. Under these conditions, n-dodecane was not detected in the receiving ionic liquid phase. (C) 2014 Elsevier B.V. All rights reserved.

Since many years food engineers have attempted to describe physical phenomena such as heat and mass transfer that occur in food during unit operations by means of mathematical models. Foods are hierarchically structured and have features that extend from the molecular scale to the food plant scale. In order to reduce computational complexity, food features at the fine scale are usually not modeled explicitly but incorporated through averaging procedures into models that operate at the coarse scale. As a consequence, detailed insight into the processes at the microscale is lost, and the coarse scale model parameters are apparent rather than physical parameters. As it is impractical to measure these parameters for the large number of foods that exist, the use of advanced mathematical models in the food industry is still limited. A new modeling paradigm – multiscale modeling – has appeared that may alleviate these problems. Multiscale models are essentially a hierarchy of sub-models which describe the material behavior at different spatial scales in such a way that the sub-models are interconnected. In this article we will introduce the underlying physical and computational concepts. We will give an overview of applications of multiscale modeling in food engineering, and discuss future prospects. ispartof: Journal of Food Engineering vol:114 issue:3 pages:279-291 status: published

International audience; Hydrogen storage in metal hydride tanks (MHT) is a very promising solution. Several experimental tanks, studied by different teams, have already proved the feasibility and the interesting performances of this solution. However, in much cases, an optimization of tank geometry is still needed in order to perform fast hydrogen loading. The development of efficient numerical tools is a key issue for MHT design and optimization. We propose a simple model representing a metal hydride tank exchanging its heat of reaction with a thermal fluid flow. In this model, the radial and axial discretisations have been decoupled by using Matlab (R) one-dimensional tools. Calculations are compared to experimental results obtained in a previous study. A good agreement is found for the loading case. The discharging case shows some discrepancies, which are discussed in this paper.