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International audience; Ammonia has a potential as carbon-free and high-energy density compound for chemical storage of renewable energies and its synthesis from green H2 requires to be as energetically efficient as possible. In this work, a superstructure optimization methodology for process synthesis is proposed and applied to an ammonia production process. The approach covers three different scales: process, equipment, and molecules. Process scale refers to finding the optimal process structure, while the equipment scale is related to the best set of operating conditions, and the molecular scale studies two catalysts (Fe and Ru) with their respective kinetic rates. The optimization intends to minimize the Levelized Cost of Ammonia (LCOA) and maximize the energy efficiency. The best trade-off is found with the Ru catalyst, with an LCOA of 766 €/tNH3 and 57.2 % of energy efficiency. In comparison with reference cases, the LCOA decreases 0.6 % and the energy efficiency increases 1.5%. The main improvement is found in the pressure, 75 bar, reduced in 25 %. The production of 11.6 tNH3/day equals to 2.5 MW of stored power from 3 MW supplied as H2 to the process, with a total energy consumption of 10.67 kW h/kgNH3, including prior H2 and N2 production processes.

Nickel (Ni) agromining aims at recovering this metal from the biomass of hyperaccumulator plants grown on serpentine soils, giving value to these low-grade agricultural soils. A process has already been designed to produce Ni salts, especially ammonium nickel sulphate hexahydrate (ANSH) from the biomass of Alyssum murale. The first stage of biomass processing consists of burning the dry plant to obtain ash, considered as a bio-ore because of its high Ni content (15–20%). This stage is perfectly controlled at the lab scale with a few grams of plant. At the pilot scale, plants are burnt in a boiler dedicated to biomass combustion; temperature cannot be precisely controlled and reaches 900 °C, which is likely to modify the chemical composition of ashes. The objective of this research was to compare ashes produced at lab and pilot scales and assess if the ANSH recovery from ashes obtained at higher temperature was still effective. Two batches of ashes of A. murale were prepared at the lab and pilot scales (550 and 900 °C) and analysed for elemental composition, mineralogy, particle size and morphology. Due to different temperatures and combustion times, the two ashes resulted to have diverse characteristics. To test process efficiency, they were used in the first process stages in which ashes are involved: potassium removal by ash washing and acid leaching to transfer Ni into solution. Extraction kinetics of potassium, the main impurity, was modelled. Results show that the discrepancy in ash composition and properties had no influence on the process. Hence, it can be up-scaled by using an industrial furnace to increase the production of nickel salts and develop a valuable method for Ni recovery by agromining.

Drop-based hydromechanics has gained extensive attention, especially drop formation and breakup, due to the wide-ranging applications and rich physical phenomena. Magnetic field as an externally active means, displays enormous potential in manipulating drops. In this work, the formation and breakup dynamics of ferrofluid drops with an upward magnetic field (UM), downward magnetic field (DM) and no magnetic field (NM) were respectively investigated and compared. A high-speed camera was used to observe the morphological evolution of ferrofluid drops during the formation at a nozzle in air. The shape evolution of the initial drops, primary drops and satellite drops was exhaustively studied. It was found that the volume, shape as well as formation frequency of ferrofluid drops could be actively controlled by an applied magnetic field. Through analyzing quantitatively the minimum neck diameter and corresponding position, the breakup process reveals complex nonlinear dynamics and exhibits finite time singularities and self-similarity, regardless of the initial conditions. Furthermore, the primary pinch-off processes both in the axial and radial directions were deeply investigated and the results unveil that the axial elongation is much faster than the radial diminution. In a word, the gravity-compensating and gravity-superimposing magnetic fields exert a negligible effect on the pinch-off mechanism, but directly determine the location of primary pinch-off point.

Phytomining, now called agromining, consists of growing hyperaccumulator plants in orderto farm metals and recover them from the biomass. This technology enables us to extractmetals from secondary resources (e.g. metal containing-soils, mineral wastes, polluted soils)and manufacture high-value products. It has proved feasible for nickel, since more than 400hyperaccumulators have been identified worldwide, able to accumulate at least 1% Ni intheir tissues. Moreover, Ni is a target metal with a relatively high economic value.We have recently designed and patented a method for the synthesis of a nickel salt,ammonium nickel sulfate hexahydrate (ANSH: Ni(NH4)2(SO4)2·6H2O), from the biomass ofthe hyperaccumulator plant Alyssum murale, grown in the Balkans. In this contribution, theprocess has been improved in order to save water, energy and chemicals, while producinga high purity salt. The biomass is dried and ashed, potassium is removed by washing ashwith pure water following a cross-current pathway, nickel is extracted by acid leaching (2 MH2SO4, 95◦C, 2 h, mass fraction of 10%). The leachate is neutralized by Ca(OH)2to reach a pHof 4–5 and magnesium is removed by precipitating MgF2after addition of NaF. Then volumeis reduced by evaporation and ANSH crystallization is run at 2◦C for 4 h. The crystals are dis-solved and a second crystallization is run. The final ANSH was characterized by combinedtechniques (ICP-AES, XRD and gravimetric analysis), and the purity was 99.1 ± 0.2%.

International audience; Some representations are well established in Chemical Engineering: the logic of unit oper- ations, the logic linking reaction, transfer and transport phenomena or the logic of scales (from atoms to process and even to market). Today chemical and process engineers aim to open new opportunities for innovation, promote new ideas and create new representa- tions. This notably involves exploring how to think differently and working on the earlier stages of design. Design Theory is particularly suited to deal with early innovation and to promote idea generation. In this study, the C–K innovative design method, which is well used in industrial companies, was applied to the Chemical Engineering field. With C–K method, innovation emerges through a co-expansion of the Concept-space and the Knowledge-space. This project aimed to both open new paths of innovation and identify C–K strategies that would allow reaching promising concepts for Chemical Engineering. The results are presented through several C–K trees. The most promising design paths for this C–K exploration are those leading to an interaction between different representations and reviewing the established logics of unit operations, scales and reaction–transfer–transport phenomena. An evaluation of the exploration quality is then presented and allows opening further lines of development.

International audience; The heterogeneous catalysis for esterification generally uses a poly(styrene-divinylbenzene) sulfonated resin. It presents a selective affinity with the chemical species involved in the reaction, and a coupled phenomenon of swelling. The components partitioning rests on still not precisely known interactions between the chemical species and the intern structure of catalyst. Although the chemical reaction is supposed to be located in the resin structure, most of the proposed kinetic models do not involve the sorbed components. Due to reaction processes, the sorption and kinetic phenomena cannot be independently studied. First part of the methodology is the analysis of selective sorption in absence of reaction at room temperature. The swelling phenomenon study at reaction temperature then allows the simultaneous determination of kinetic and sorption coupled parameters. It permits to design a more realistic kinetic model of the heterogeneous esterification reaction, to estimate the parameters and to validate them on experimental data obtained with esterification reactions in a batch reactor.

International audience; High performance of compact heat exchangers is conditioned by correct fluid distribution. This is especially true for gas-liquid heat exchangers where a uniform distribution is particularly delicate to obtain and where maldistribution entails significant performance deterioration. Several phenomena can lead to phase distribution problems: the fins may be subject to manufacturing defects or fouling, leading to shortcuts or dead zones. But the first source of maldistribution may be a poor distribution at the outlet of the entrance distributor. This distributor aims at mixing the phases and distributing them across the channels. The present study deals with the simulation and experimental investigation of the two-phase distribution and flow regimes in a distributor located at the bottom of the cold flow pilot plant of a vertical compact heat exchanger. Air and water are the working fluids, and the range of superficial velocities inside the distributor is 0.9-8.8m s(-1) and 0.35-0.8 ms(-1), for air and water respectively. Three-dimensional Volume Of Fluid (VOF) simulations are performed and compared to experimental distributions, pressure drops, and visualizations.

International audience; The objective of this article is to find the optimal dimensions of rectangular plate-type micro-separators in order to enhance the continuous separation of immiscible liquids. The main structure of the separators contains two plates: a hydrophobic (PTFE) upper plate and a hydrophilic (stainless steel) bottom plate which formed the contact surfaces for the fluids in the channel. The devices have two outlets, one for the aqueous phase and the other for the organic phase enabling the continuous separation and withdrawal of the separated phases. Demulsification has been carried out using Shellsol/water emulsion in the presence of a non-ionic surfactant (Teen 80). The separation efficiency is investigated as a function of micro-separator sizes, channel depths, flow rates and plate configurations. The major parameter that controls the destabilization mechanism is the ratio between the droplet size and the channel depth. When the size of the dispersed droplets remains smaller than the height of the separator (channel depths: 25-100 mu m), creaming is the main demulsification mechanism. Creaming refers to the migration of the dispersed phase of an emulsion, under the influence of buoyancy. The particles float upwards and rise to the top due to the difference in the densities of the particles and the medium. The separation efficiency depends mainly on the residence time of the liquid/liquid mixture in the device regardless of the separator dimensions and channel heights. The separation rate is limited by the removal of the cream layer, formed at the top of the upper plate, from the separator. When the size of the dispersed droplets is larger than the depth of the separator (channel height of 9 pm), the separation performance and mechanism become different. The coalescence of the dispersed droplets occurs by passing through the device. The comparison of the data corresponding to creaming and coalescence phenomena emphasizes that the coalescence greatly enhance and accelerate the separation action. The phase separation in the micro-coalescer takes place considerably faster than in the micro-separators.

International audience; This work investigates the impact of catalyst structuring into particles or monoliths on methanol production from only CO2 and H2 at a large scale. Methanol synthesis in multi-tubular reactors is evaluated using packed-bed and monolithic reactors by modeling heat and mass transfer in each reactor. The obtained simulation results show that, at low gas hourly space velocity (GHSV = 10,000 h−1), the performances of both reactor technologies are similar. In this case, the packed-bed reactor technology is the most appropriate technology due to its simplicity of installation and operation. At high GHSV (25,000 h−1), the packed-bed reactor technology is limited by a considerable pressure drop that causes an important loss in productivity due to thermodynamic equilibrium, whereas the monolithic reactors exhibit negligible pressure drop and achieve far better performances.

International audience; Electrochemical processes involving gas evolution at appreciable rates have been optimized in their design for the sake of reduced energy consumption. The present investigation was conducted in view to reducing the energy demand of a pilot process for electrolytic reduction of hematite particles to iron metal; attention was paid at the design of the lantern blade anodes where oxygen evolution occurs. An experimental cell consisting on two facing anodes and two remote cathodes has been designed and used for investigation of the gas behavior and current density distribution at the anode blades. The model for prediction of secondary distributions was validated by measurement of the currents at the segmented anodes and the effects of the average current density and the anode gap could be observed. The model was finally applied to the pilot cell for iron production; as expected, larger gaps allow more uniform current distributions at the anode, however without reducing the cell voltage. In contrast, blade lengths in the order of 10-15 x 10(-3) m only would allow visible reduction in the cell voltage.

International audience; Post combustion carbon dioxide capture raises tremendous chemical engineering challenges. For the first generation of industrial installations, gas liquid absorption in chemical solvents is classically considered to be the best available technology. Two major bottlenecks have however to be solved in order to achieve technico-economical targets: decrease the energy requirement of the process (e.g. through novel solvents or heat integration approaches) and decrease the size of the installation (through process intensification).This study intends to explore the possibilities and limitations of membrane contactors, which are considered as one of the most promising strategy for intensified CO2 capture by gas–liquid absorption. A very large number of studies is continuously reported on this topic, including materials, mass transfer or process design issues, but a rigorous evaluation of their effective potential in terms of intensification is still lacking. Moreover, controversial results have been reported such as intensification factors, compared to packed columns, ranging between 10 and 0.8 on a total unit volume basis.This unclear situation results from different factors. First, experimental comparison of membrane contactors vs. packed absorption columns performances is indeed seldom. Second, the evaluation of membrane contactors is systematically performed at laboratory scale, under operating conditions which do not necessarily reflect industrial operation (i.e. fresh amine solutions are used, limited capture ratio are achieved). These simplifying assumptions have obviously to be reconsidered if a realistic comparison for industrial operation is aimed. More importantly, pressure drop levels, which are known to be very small for packed columns (typically 50 mBar on the gas side for an industrial packed column), have to be considered in order to minimize the energy impact of the process. An analysis combining intensification and pressure drop aspects for membrane contactors design, with solvent flowing inside the fibers, and the associated trade-off, which, to our knowledge, has not been achieved for CO2 absorption, is presented based on experimental and simulation results. Practical guidelines on the set of conditions for membrane materials (i.e. permeability and thickness), fiber geometry (external diameter, thickness) and module design (length, packing factor) which enable a significant process intensification effect are finally proposed.

International audience; To assess the long-term safety of a geological carbon dioxide storage site, the confining properties of the rocks sealing an underground reservoir (caprocks) and their evolution inthe presence of CO2 must be characterized. The present study consists in the measurement of the transport parameters of dissolved CO2 through low permeability carbonate-rich caprocks. The properties of interest are the effective permeability and the diffusion coefficients of carbon dioxide dissolution products in water. The impact of carbon dioxide has been evaluated when altering rock samples by diffusion of a CO2-saturated brine under reservoir thermodynamic conditions, and by comparison of the pre- and post-alteration measured values. Permeability was measured by a gas-tracing method and, to study diffusion, radioactive isotopes of carbon (14C) and hydrogen (3H) were used. Despite a porosity increase observed for all the studied samples, the low values of transport parameters, measured initially, were also measured after alteration, showing a non-catastrophic alteration of the material.

International audience; CFD techniques are used to study the precipitation of barium carbonate in a solid–liquid fluidized bed reactor. Experimental analysis of the hydrodynamic behaviour for a neutralization reaction in the fluidized bed column, followed by CFD simulations is carried out using different reaction models. The Eddy Dissipation model, the Eddy Dissipation model-MTS and the Eddy Dissipation Concept micro-mixing models are tested in order to simulate the acid–base instantaneous reaction. The modelling of the precipitation in a fluidized bed reactor is coupled with the Eddy Dissipation model-MTS micro-mixing model and the k- standard turbulence model. Barium carbonate is chosen as the model substance. The liquid phase reaction rate as well as the nucleation, growth and aggregation kinetics is included in the precipitation model. The discrete method is chosen to solve the population balance equation. The activity coefficient needed to calculate the supersaturation in the kinetic equations is determined using the Bromley's method. A good agreement is obtained between the experimental results and the CFD results.