Modélisation de la cinétique de biodégradation de phénol par granules aérobies

This work describes a model of the biodegradation of phenol carried out by aerobic granules. These granules were obtained by culturing an activated sludge supernatant in a sequencing batch reactor fed with a synthetic waste water and subsequently, by acclimation to phenol (100 mg/L). The kinetics of phenol biodegradation by the aerobic granules was investigated over a wide range of initial phenol concentrations (40–1112 mg/L) in shake‐flask cultures. A Haldane‐type model was adjusted to the experimental results, which depicts successfully the phenol biodegradation profiles in the entire range of initial concentrations studied by using only one set of parameters. It is our view that the proposed model could contribute to the knowledge about the ability of aerobic granular systems to biodegrade toxic, inhibitory compounds such as phenol.     

Dispositif de déposition de couches de suspensions de céramiques appliqué à la stéréolithographie

A system to coat uniform layers of ceramic suspensions has been developed for rapid prototyping applications. The metering system is made of a gas injection nozzle which height, angle of attack and pressure can be adjusted. The coated layer homogeneity and the process reproducibility have been studied. The effect of each parameter on the coated layer thickness has been characterized using a design of experiments approach and a reliable mathematical model is proposed to optimze the coating system.     

Méthodologie d'étude et de modélisation de la déphosphatation d'effluents aqueux

Due to phosphorus impact on water pollution, a P‐recovery process by calcium phosphate precipitation was developed. The reactor process is a fluidized bed in which phosphate precipitates continuously and coats sand grains. The pilot unit can treat synthetic wastewater flow rates ([P] = 50 mg/l) of about 0.1 m3/h. A two‐stage methodology is proposed to understand the physicochemical phenomena. Fluidized bed precipitation modeling involves thermodynamical concepts taking into account the various calcium phosphates that can precipitate vs. operating conditions (PH, [P], [Ca], T). Coating modeling is performed by a first‐order kinetics reaction between fines and sand grains, combined with a network of ideal reactors representing system hydrodynamics.     

Simulation de la distillation catalytique par un nouveau modèle de transfert – Application à la production d'acétate de méthyle

A catalytic distillation model, based on Maxwel‐Stefan Equations, is presented. In this model, the effective diffusion in porous catalyst is taken into account. Since this model is developed in a commercial environment (ProSim Plus process simulator), particular attention is paid to the solution strategy: robustness and adaptability are of particular importance for the user. The influence of catalyst characteristic, column design, mixture non – ideality and liquid/vapour interface are discussed. We conclude that an optimum design exists. Reflux ratio and catalyst location are key‐parameters.     

Cinétique de la calcination du coke de pétrole en atmosphères neutre et oxydante

A devolatilization kinetic study of oil coke samples under conditions close to those of industrial calcination furnace is presented. The effects of the surrounding conditions (neutral or oxydizing medium), the heating rate and the percentage of oxygen in an oxydizing environment are analyzed. Experiments are carried out in an induction oven and involved thermogravimetric and chromatographic analyses. Results show that, under certain conditions, the nature of the environment influence the devolatilization process. A slow heating rate and a low content in volatiles promote the coke degradation by oxygen in an oxydizing medium. The reactive schemes are derived by tracking the concentration of CH₄, H₂, CO and CO₂. In regions where the coke is not degraded, a kinetic model is used to compare the parameters describing the develotilization phenomena in the two media (neutral and oxydizing), i.e.: the reaction order, the activation energy and the pre-exponential factor. It is shown that the oxydizing medium promotes an increase in the activation energy.     

Dépôt chimique CVD de silicium dopé in situ au phosphore. Partie 2: Analyse théorique et modélisation

The behaviour modelling of a CVD reactor is useful to better understand the involved complex mechanisms and determine the conditions required for the fabrication of depositions according to industrial standards. This approach was applied to the deposition of polycrystalline silicon doped in situ with phosphor. A model was developed to represent the deposition process which predicts correctly the excess of deposition thickness caused by silylene. The control of the deposition operation is mainly governed by the feed phosphine concentration and the inlet geometry where silylene is formed.     

Etude de l'influence des paramètres de fonctionnement d'un réacteui électrochimique à lit fixe conique

The recovery of metallic ions from dilute solutions has been carried out with a three-dimensional electrode. This work follows a study of electrochemical reactors with transported beds enclosed in a conical vessel. It deals more precisely with the influence of flow direction (upwards or downwards) and the cone angle when a reactor is working at the limiting diffusion current. The results of this study permit to define the geometric parameters determining the most efficient operation of the reactor.     

L'électrolyseur dans l'optique de la dynamique des procédés

This article written for the non-specialists reviews the various methods for modeling electrolyzer behavior. Deterministic and stochastic models are discussed and the adaptation of process dynamic to electrolysers is emphasized.     

Etude de l'oxydation du pentachlorophénol dans différentes géométries de réacteurs à ultrasons de haute fréquence

The determination of the key geometric parameters used for high-frequency sonoreactor modeling has been studied. The methodology allowing the characterization of the different reactors built in our laboratory has been defined. The methods are: calorimetry, determination of the residence time distributions, the observation of the chemiluminescence of luminol and the degradations of a prototype molecule: pentachlorophenol. After characterization of the studied reactors, it seems that volumetric power, with equivalent emitting system, is the major parameter of the reactor's performance.     

Augmentation,par régénération électrochimique du substrat,de la production d'une biomasse (thiobacillus ferrooxidans DSM 583) pour un procédé biologique de récupération de métaux

A bioelectrochemical reactor regenerates the substrate of the acidophilic bacterium Thiobacillus ferrooxidans DSM 583 (ferrous ions). This reactor uses a through-flow porous fixed bed or carbon as cathode. A linearizing non-linear regulator insures an efficient control of the intensity imposed to the electrochemical reactor. The protein concentration, correlated to the biomass concentration, is 6.4 fold increased for a 55 h growth, including a 20 h electrolysis. The metal tolerance and the metal fixation capacity of a T. ferrooxidans biomass are presented both for solutions including one or two metallic ions and an industrial waste. A bioelectrochemical process based on these characteristics is proposed for removing metal ions from wastes.     

Etude numérique et paramétrique de la combustion de particules d'aluminium

Several numerical models have been investigated to study the reactivity of aluminium particles coming from the combustion of solid propellants in spatial launchers. The Law model has been rapidly selected as it yields a continuous model from an aluminium drop to an oxide drop. The model also gives the residue size at the end of the combustion process. This could explain the scaling observed in the rocket engines. In order to study the coupling between the flow and the combustion, the combusion of aluminium drops has been widely analyzed with 0D computation. The main mechanisms of the combustion process have been identified.     

Corréation entre la stabilité colloïdale de la matière première et le degré de dispersion du noir de carbone

The evolution of carbon black technology allows, at present, various hydrocarbon products as fillers in complex mixtures. The fillers investigated in this work are made of a blend of five products from different origins. The objective of this work is the study of the correlation between the colloidal stability of the filler and the quality of the carbon black, as well as the relation between the degree of dispersity of the carbon black and the resin tensile strength.     

Effet de la pression sur la transition ruisselant-pulsé dans les réacteurs catalytiques à lit fixe arrosé

The effect of pressure on transition displacement between trickle and pulsed regimes (TPR: trickle-pulsed transition) in catalytic trickle bed reactors (CTBR) is not properly predicted by existing theoretical models and empirical correlations. Based on high pressure TPR data available to date, a modified Charpentier diagram is proposed to quantify directly the effect of pressure in non-foaming systems.     

Enlèvement du phosphore des eaux usées par traitement à base de tourbe dopée aux boues rouges

The addition of an aluminium and iron doping agent, bauxite red mud, has been tested with a commercial peat for thetreatment of a secondary municipal wastewater. Based on a column study, phosphorus (P) removal was raised from about17% to 21% on peat alone to over 95% with red mud treatment of peat. By this mean, the use of red muds allowed areduction of P, concentration effluent to below 0.15 mg/L. The boosting effect of red mud seemed to decrease with timeand especially with the hydraulic loading. For a hydraulic loading of 30 cm/j, P removal met govermental guidelines (_t effluent < 1 mg/L) for a period of 50 days. Other classic efficiency parameters such as BOD₅, COD and coliforms werenot altered by the use of the doping agent.     

Modélisation d'un four de calcination du coke de pétrole: II. Simulation du procédé

A one-dimensional steady-state mathematical model has been developed to simulate the process of calcination of petroleum coke in a rotary kiln. A simulation is made to reproduce the operating conditions prevailing during a normal working day, in order to validate the model, and to study the effects of the main process control variables. It has been found that of the energy provided by combustion, 59.5 % comes from hydrogen, 14.6 % from the carbon of the coke bed, 13.8 % from coke dust, 11.3 % from methane and 0.8 % from tar. A comparison with existing models is made to identify eventual similarities between the various kilns under study. It appears that maximum coke temperature occurs at 45 to 55 % of kiln length, while volatile matters evolution takes place between 5 and 60 % of kiln length, measured from feed end.     

Le cyclone: Un réacteur chimique. Application à la réaction de décarbonatation de NaHCO3

The purpose of the present paper is the experimental and theoretical study of the behaviour of the cyclone working as a chemical reactor. The model reaction is the decarbonation of NaHCO₃. Thanks to the use of scale-up relationships previously determined, it is possible to derive kinetic constants in good agreement with other published values obtained under quite different conditions. The measurements are performed in a wide range of experimental conditions (particle size, residence time of particles, cyclone wall temperatures, solid flow rate). The paper emphasizes two possible fields of utilization for the cyclone: a device for the measurement of kinetic constants, a processing reactor operating with high throughput of solids.     

Dépôt chimique CVD de silicium dopé in situ au phosphore. Partie 1: Etude expérimentale

The fabrication of silicon layers doped in situ with phosphor using CVD technique is still poorly controlled by the microelectronics industry. Significant thickness heterogeneities are noticeable on circuit and load, which greatly limits the process utilization. An experimental study of this deposition was carried out. The influence of many parameters (temperature, pressure, feed composition) was studied in terms of deposition thickness and uniformity as well as crystalline structure and resistivity. The advantages and involved mechanisms are presented.     

Contrôle hydrodynamique de l'evaporation d'un film liquide ruisselant sur une paroi isotherme à symétrie de révolution dans un courant d'air humide

A thin-film evaporation from a surface of a axisymmetrical body in a humid air stream was studied using a finite difference method associated with Thomas' algorithm. The surface of the body is supposed isothermal. The variability of physical properties is taken into account, and a steady-state and laminar regime is supposed. The influence of the main parameters of the system on the evaporation is determined, especially the wall profile. It is shown that, for certain conditions of calculation, it is possible to find a flat ellipsoid of revolution offering a uniformly accessible wall between the pole and the equator.