Modeling Ozonation and Chlorination in potable Water Treatment

This article presents SimOx, the new simulator being currently developed by Anjou Recherche / ENSCR for oxidation steps in potable water treatment works. Whereas designing this new prediction engine was originally motivated by difficulties encountered when simulating a plant under on-site conditions, an increasingly stringent legal context and the emergence of micropolluants of concern clearly confirmed the need for a performing and innovative tool. The experience gained with the development of previous simulators is of advantage and opens interesting possibilities, in particular calculation capabilities upon which SimOx partly bases. Nevertheless, given the very characteristics of the new simulator SimOx (capacity to deal with sparse on-site data under changing water matrixes and hydrodynamic conditions), special modelling and calculation procedures are being implemented

Improved growth model for two-stage continuous cultures of Lactobacillus helveticus

An unstructured model for growth and lactic acid production during two-stage continuous cultures of Lactobacillus helveticus was previously developed. The Verlhust model was considered to describe growth kinetics. Production models was based on modified Luedeking-Piret expressions involving an inhibitory effect for the first stage (seed culture) and a nutritional limitation effect for the second stage (culture). To account for the decrease of the biomass concentration observed in the second stage, the dilution rate Dc was replaced by an exponential term of the dilution rate \u3b1 exp (Dc/\u3b2 ) in the growth and product relations. Contrarily to the previous model, the important decrease of the biomass concentration observed at steady state in the second stage at high dilution rates, namely close to wash out, was correctly described by the new model. It also proved to satisfactory describes production data and volumetric productivity

Chromatographie à contre-courant simulé : développements et perspectives

Les applications industrielles et le principe de fonctionnement du procédé de séparation en lit mobile ou en contre-courant simulé sont brièvement rappelés. La réalisation pratique de trois unités pilotes fonctionnant selon ce principe mais employant une technologie innovante est présentée. Cette mise en oeuvre particulière permet de tester par un simple changement de paramètres de contrôle toutes les configurations possibles de l'unité. Cet appareillage particulièrement souple est donc véritablement multitâche, ce qui permet en plus des applications en pétrochimie son emploi dans les domaines de la pharmacie, de la chimie fine et des bioséparations, où existe un grand nombre d'applications potentielles très différentes les unes des autres. Deux exemples de séparations réalisées à l'Institut Français du Pétrole sont succinctement présentés. La conclusion de ces essais est que la modélisation de ces procédés est indispensable pour pouvoir opérer correctement ce type d'unité. Une comparaison entre la chromatographie d'élution et cette technique de séparation ainsi que quelques propositions d'amélioration du procédé permettront au lecteur de se faire une idée sur l'extension potentielle de ce type de séparation

Comment on "anomalous dielectric behavior of nanoconfined electrolytic solutions". Reply to comment.

International audienceA reply to the polemic of Gekle and Arnold, ibid., 089801. [on SciFinder(R)

Behavior of volatile compounds in membrane distillation: The case of carboxylic acids

International audienceThanks to its unique features, membrane distillation (MD) has been particularly applied for desalination but also for niches applications with feed solutions containing a mixture of volatile molecules. For such solutions, the complex interplay of the solutes and solvent physicochemical and operating parameters makes it challenging to predict the separation efficiency by MD. There is thus a need for a better understanding of the behavior of volatile compounds in MD as well as the influence of their physicochemical environment. This study aimed at investigating the influence of different operating parameters on rejection efficiency of air-gap MD towards carboxylic acids (formic, acetic and succinic acids). Acid rejection was found to be highly dependent on the carboxylic acid structure. In addition, it increased with the acid concentration, which could be related to the formation of acid dimers in the feed solution. This behavior is opposite to what is classically observed for pressure-driven membrane processes thus suggesting that MD can be a suitable alternative to these techniques for the concentration/separation of carboxylic acids. On the other hand, acid rejection decreased with the increase of feed temperature which could be explained by the calculation of the apparent energies of activation of both the water and carboxylic acids using an Arrhenius-type model. Finally, the acid dissociation rate played a key role in the acid rejection. Taking advantage of this observation, it was demonstrated how a simple pH adjustment can be used to successfully achieve the selective separation of ethanol (compared to acetic acid) from an acetic acid/ethanol aqueous mixture. © 2020 Elsevier B.V

Assessment and potential of membrane cascades for organic solvent nanofiltration of hydroformylation media through a graphical representation composed of performance maps

International audienceThis paper aims at proposing a graphical representation composed of several performance maps to help to answer to some current questions that can puzzle membrane end-users facing the arrangement of membranes in cascade in order to better master separation of complex media. Indeed, different compromises can be highlighted according to realistic goals for the separation such as quality and recovery yield of each fraction/component, energy consumption and required membrane area. This representation needed first the systematic simulations of cascades of pre-selected configurations. These last ones were chosen thanks to the target application field, namely the organic solvent nanofiltration of a final synthesis media of hydroformylation that is a homogeneous catalysed reaction. We voluntary assumed the a priori limitation of the number of stages to 5, anticipating that more complex cascades will probably be too expensive (both operating and capital costs). The graphical representation by itself is based on sets of six 2D-maps. Each map highlights relationships selected in an appropriate way between two of the six selected criteria extraction/recovery, retentate/permeate quality/purity, membrane filtering area and overall energy consumption. For sake of illustration, the separation of 2 components C and A was considered. C/A has been chosen in a 1/1000 molar ratio, where C corresponds to the less retained component of the catalytic system that must be recovered in the retentate and A corresponds to the less transmitted product to extract in the permeate. In realistic nanofiltration conditions achieved in toluene, the rejections were experimentally determined on the initial media to filter. C has a high rejection (88%) whereas A has a low one (30%). The simulations of cascades were established using these constant values for rejection and the experimental permeate flux. For sake of an illustration of the use of the graphical representation, a case study was finally discussed regarding a given target of recovery for the two desired components, namely at least 99% of C recovery and better than 70% of A extraction. A complementary multi-criteria analysis was added aiming at facilitating the decision-making