Showing papers in "Canadian Journal of Chemical Engineering in 1972"

Effectiveness factors for immobilized-enzyme reactions

Abstract: The effect of intraparticle diffusion in artificial membranes on the kinetic behavior of immobilized enzymes has been considered theoretically in terms of an effectiveness factor. When the immobilized enxymes obey a Michaelis-Menten relationship, an approximate equation is proposed for the effectiveness factor. For a substrate inhibited enzymatic reaction, the effectiveness factor may exceed unity and display multiple steady-state behavior. Thus, the over-all rate of reaction in the artificial membrane is faster in this case than that when the substrate concentration in the interior is at the same as that at the exterior surface. In the case of a product inhibited enzymatic reaction, the effectiveness factor is always less than that which corresponds to a Michaelis-Menten relationship. On a etudie theoriquement, en fonction d'un facteur d'efficacite, l'effet que produit la diffusion entre particules dans les membranes artificielles sur le comportement cinetique d'enzymes immobilisees. Lorsque les enzymes immobilisees obeissent a une relation de Michaelis et Menten, on propose une equation d'approximation pour le facteur d'efficacite. Dans le cas d'une reaction enzymatique inhibee par le substrat, le facteur d'efficacite peut ětre plus grand que 1 et indiquer un comportement de regimes permanents multiples; aussi, la vitesse globale de reaction dans la membrane artificielle est-elle plus considerable dans ce cas que lorsque la concentration du substrat a la surface interieure est la měme que celle qu'on note a la surface exterieure. Dans le cas d'une reaction enzymatique inhibee par un produit, le facteur d'efficacite est toujours moindre que celui qui correspond a une relation de Michaelis et Menten.

The effects of extruder variables on the gelatinisation of corn starch

Abstract: The first stage of a study of the extrusion of starch-based materials is described. The chemical and physical changes which occur in the extrusion of a corn starch-water system relative to fifteen extruder variables have been investigated. A mathematical model of the extruder has been obtained from analysis of the data. The important variables were found to be moisture, barrel and die temperatures, screw speed and screw geometry. A strong interaction between moisture and barrel temperature was found to occur. These variables in the model account for 90.5% of the variance in the data obtained. The effects of the variables on the gelatinisation and shearing mechanical degradation of starch are discussed. On decrit la premiere etape d'une etude sur l'extrusion de produits amylaces. On a examine les changements chimiques et physiques qui se produisent dans l'extrusion d'un systeme forme de fecules de mais et d'eau, en employant quinze variables relatives a l'appareil refoulant (bondineuse). On a mis au point un modele mathematique de la boudineuse a la suite de l'analyse des resultats experimentaux. On a trouve que les variables importantes etaient l'humidite, les temperatures du barillet et de la matrice ainsi que la vitesse et la forme de la vis. On a constate qu'il se produisait une forte action reciproque entre l'humidite et la temperature du barillet. Les dites variables dans le modele ont ete responsables de 90.5% des variations notees dans les resultats experimentaux. On discute l'influence des variables sur la gelatinisation de l'amidon et sa desintegration mecanique par cisaillement.

Hold-up and axial mixing characteristics of two and three phase fluidized beds

Abstract: The hydrodynamics of two (water-air, water-solids) and three (water-air-solids) phase fluidized beds have been studied in a large two-dimensional column. Two solids were used, namely 6 mm glass beads and 2.6 mm irregular gravel. The individual phase holds-ups, bed expansion, and axial mixing characteristics were measured. The data were correlated empirically by equations involving liquid and gas phase Reynolds and Froude numbers, and the ratios of the particle and fluid densities. Bubble sizes and rising velocities were determined photographically and found to be of great importance in determining the hydrodynamics of the different beds. On a etudie, dans une grosse colonne a deux dimensions, lehydrodynamique de lits fluidises a deux phases (eau-air et eau-matieres solides) et a trois phases (eau-air-matieres solides). On a utilise deux sortes de matieres solides, a savoir des perles de verre de 6 millimetres et des particules de gravier irregulier de 2.6 millimetres. On a mesure la retention dans chaque phase individuelle, leexpansion des lits et les caracteristiques du melange axial. On a etabli une correlation empirique entre les resultats obtenus au moyen dequations comportant des nombres de Reynolds et de Froude, phases liquide et gazeuse, et en utilisant les rapports entre les densites des particules et du fluide. On a determine par photographie les dimensions des bulles et leurs velocites delevation; on a trouve queelles etaient bien importantes pour determiner lehydrodynamique des differents lits.

Fluid dynamics and flow patterns in stirred tanks with a turbine impeller

Abstract: Velocity profiles were measured in a stirred tank with a turbine impeller using a three-dimensional, pitot tube probe. A tangential jet model was used to describe the flow in the region of the impeller, and two-dimensional potential flow models and a circular jet were used to describe the flow in the rest of the tank. The tangential jet model accurately predicted the measurements from this work and comparable measurements reported in the literature for water and air, for varying impeller diameter and speeds and for different tank diameters. In the rest of the tank a three-dimensional, low velocity, flow field exists; and the center of circulation is not a true stagnation point. The flow at this point is tangential. The two-dimensional models only qualitatively described the flow in this region, and a three-dimensional model would be required. It was experimentally and theoretically confirmed that standard practice of using 10% baffles effectively controls the flow in the tank. On a mesure les profils de velocite dans un reservoir agite et muni d'une roue mobile de turbine, en employant une sonde basee sur un tube de Pitot a trois dimensions. On a utilise un modele de jet tangentiel pour decrire I'ecoulement dans la region de la roue ainsi que des modeles d'ecoulement potentiel a deux dimensions et un jet circulaire pour indiquer I'ecoulement dans le reste du reservoir. Le modele de jet tangentiel a predit avec justesse les mesures ainsi obtenues et celles qu'on a publiees pour I'eau et I'air, dans le cas de divers diametres et vitesses de roues et de diametres differents de reservoirs. On a trouve qu'il y a dans le reste du reservoir un champ d'ecoulement a trois dimensions et faible velocite et que le centre de la circulation n'est pas un vrai point de stagnation; I'ecoulement a ce point est tangentiel. Les modeles a deux dimensions ne decrivent que qualitativement I'ecoulement dans la dite region et il faudrait avoir recours a un modele a trois dimensions. On a confirme experimentalement et theoriquement que I'emploi normal de chicanes a 10% permet de contro'tler efficacement I'ecoulement dans le reservoir.

The effect of non‐uniform porosity in causing flow maldistributions in isothermal packed beds

Abstract: A formulation is developed for the flow of an incompressible fluid through a two dimensional packed bed having a spatially variable void fraction, through the statement of the Ergun Equation in a two dimensional system. Computed results are presented for particular spatially distributed void fractions in the bed, which indicate that a lateral variation in the resistance to flow may cause appreciable flow maldistribution and “cross flow” effects. This work is thought to be a first, necessary step in the quantitative understanding of channeling and by-pass phenomena in packed bed reactors. On met au point une formule relative a I'ecoulement d'un fluide incompressible dans un lit gami a deux dimensions et dans lequel il y a une fraction de vide a variable spatiale; on a employe, a cette fin, I'enonce de I'equation d'Ergun dans un systeme a deux dimensions. On presente les resultats calcules dans le cas de fractions de vide particulieres, dans le lit, ou la distribution est spatiale; ils indiquent qu'une variation laterale de la resistance a I'ecoulement peut produire une distribution mauvaise et appreciable de I'ecoulement et les effets d'un “courant croise”. On croit que le present travail est la premiere etape requise pour avoir une idee quantitative des phenomenes de circulation et de deviation dans les reacteurs a lits garnis.

A theoretical and experimental study of natural convection in a confined porous medium

Abstract: Natural convection in a porous medium was mathematically modelled by writing force mass and energy balances on a differential element of porous medium. The resultant set of partial differential equations, which accounts for temperature-dependent physical properties, was solved numerically after the introduction of a pseudo-stream function. This method of treating emperature-dependent fluid properties, which is also applicable to other fluid flow problems, resulted in an efficient solution algorithm. Good agreement has been obtained between theoretical and experimental results. Theoretical calculations show that under certain conditions variation of fluid properties with temperature has a significant effect on convective motions.

Sorption in davison 5 a molecular sieves

Abstract: Kinetic and equilibrium data are reported for the sorption of propane, propylene and 1-butene in two commercial 5A molecular sieves (Davison C-521 and C-626). It is shown the kinetics of sorption are controlled by the diffusional resistance of the macropores and tortuosity factors are calculated from the experimental data. Rates of sorption are compared with previous data for the Linde 5A sieve. For measurements over large step changes in concentration, adsorption is much faster than desorption but these differences can be quantitatively accounted for by considering the non-linearity of the equilibrium isotherms. On presente les resultats deune etude sur la cinetique et lequilibre dans le cas de leadsorption du propane, du propylene et du 1-butene dans deux tamis moleculaires commerciaux 5-A (Davison C-521 et C-626). On γ indique que la resistance des macropores a la diffusion regit la cinetique deadsorption et leon calcule les facteurs de tortuosite a partir des donnees experimentales. On compare les taux deadsorption avec ceux queon a prealablement obtenus avec le tamis 5A de Linde. Dans le cas des mesures faites lorsqueil γ a des changements considerables dans la concentration, leadsorption est bien plus rapide que la desorption; on peut expliquer cette difference quantitativement en considerant le fait que les isothermes dequilibre ne sont pas lineaires.

The effect of a uniform magnetic field on mass transfer in electrolysis

Abstract: By coupling uniform magnetic and electric fields, the effect of the magnetic field strength on cathode current density was studied in an experimental electrorefining cell. The increase, with respect to electrolysis in a purely electric field, in the rate of mass transfer is interpreted by an approximate mathematical model. On a etudie, dans une cellule experimentale d'affinage electrolytique, l'effet de la puissance du champ magnetique sur la densite du courant cathodique; on a associe a cette fin les champs magnetique et electrique. On a interprete, au moyen d'un modele mathematique d'approximation, l'augmentation de la vitesse de transfert de masse dans le cas d'une e-lectrolyse dans un champ entierement electrique.

Fluid‐fluid interactions and hydrodynamics in agitated dispersions: A simulation model

Abstract: A model which accounts for complex fluid-fluid interactions and hydrodynamic effects in a fully baffled turbulently agitated dispersed phase system for batch, semi-batch, or continuous operation is developed. Both micromixing and macromixing effects on particle size distributions are taken into account. Coalescence and breakage functions are developed and examples are given of the normalized number and/or volume size distributions for various vessel regions. Calculated distributions are compared with experimental data to estimate values of coalescence and breakage parameters. Effects of coalescence, breakage, and system parameters on transient and steady state distributions are determined. On a mis au point un modele qui tient compte des actions reciproques et complexes de deux fluides dans un systeme a phase dispersee, completement en chicane et agite d'une maniere turbulente; ce modele a ete employe pour des operations continues, semi-continues et discontinues. On a considere a la fois les effets du micro-melange et du macro-melange sur la distribution des dimensions des particules. Des fonctions de coalescence et de fragmentation ont pris naissance et l'on donne des exemples du nombre normalise et/ou de la distribution des dimensions des particules en volume pour diverses regions du recipient. On a compare les distribution calculees avec les resultats experimentaux pour evalner les parametres de coalescence et de fragmentation. On a determine les effets des parametres de coalescence et de fragmentation ainsi que ceux du systeme sur la distribution des regimes transitoires et permanents.

Holdup in vertical two and three phase flow Part I: Theoretical analysis

Abstract: A general one-dimensional theory for predicting the average holdup or column concentration in three phase flow is formulated. The analysis takes into account the local relative velocity between the phases, the non-uniform flow and holdup distribution across the column, and the effect of the concentration of the dispersed phase on the relative velocity. The present theory is compared with the previous analyses for two phase flow reported in the literature and it is shown that all of them are special cases of the general theory proposed here. On presente une theorie generale et a une dimension pour predire la retention ou concentration moyenne dans une colonne dans le cas d'un ecoulement en trois phases. On tient compte, dans l'etude de la vitesse locale et relative entre les phases, de l'ecoulement non-uniforme et de la repartition du produit retenu dans la colonne et de l'effet de la concentration de la phase dispersee sur la vitesse relative. On compare la dite theorie avec les analyses deja faites et publiees dans le cas d'un ecoulement a deux phases; on voit qu'elles sont toutes des cas speciaux de la theorie generale qu'on propose dans le present travail.

Perturbation theory and one-fluid corresponding states theories for fluid mixtures

Abstract: A family of perturbation theories is defined which gives rise rationally, in zeroth order, to an infinite number of sets of corresponding states theories of the one-fluid type, for solutions of molecules whose potentials are conformal. It is argued that the optimum zeroth order member of this family yields the highly successful one-fluid van der Waals (vdWl) theory. This places that theory on a firm theoretical foundation and enables it to be systematically extended. The theory is derived to the second-order terms and preliminary numerical results are presented for the case of hard-sphere mixtures. Suggestions are made for empirical evaluation of some of the exact expressions. On decrit un groupe de theories de perturbation (qui se remenent rationnellement, a l'ordre zero, a un nombre infini de series de theories pour regimes correspondants comportant un seul fluide) dans le cas de solutions de molecules dont les potentiels sont en conformite les uns avec les autres. On demontre que la theorie optimale d'ordre zero au dit groupe engendre la theorie tres satisfaisante de van der Waals pour un fluide, ce qui lui donne une fondation solide et permet de la soumettre a une extension systematique. On applique la theorie aux termes de second ordre et presente des resultats numeriques et preliminaires dans le cas de melanges de spheres dures. On fait des suggestions pour l'evaluation empirique de certaines des expressions exactes.

The hydrodynamics or gas‐liquid contacting in towers with fluidised packings

Abstract: A model is developed of gas liquid contactors in which packing pieces are maintained in the fluidized state. The model proposes that the column can exist in either of two modes, namely fluidisation without flooding and fluidisation due to incipient flooding. The mode of operation established depends primarily on the packing density and to a lesser extent on the packing size, liquid flow and liquid properties. Equations predicting the transition from one mode to the next are developed. The inherent advantages of operating in the “incipient flooding” mode are stressed. It is argued that the pressure build up associated with flooding will be sufficient to support the weight of packing pieces and the liquid in the column. At this stage, rather than reject counter current flow (true flooding) the bed expands to maintain a state of incipient flooding. In this way counter current flow can be maintained in a situation well above the normal flooding point. This explains the high performance of such units.

Experimental study on the optimum performance of an adiabatic MT reactor

Abstract: The performance of an adiabatic MT reactor has been studied under various experimental conditions, using the reaction between hydrogen peroxide and sodium thiosulphate. Following the M-section, consisting of a CSTR, the T-section was made up of a large number of small stirred tanks in series. The same general condition for optimizing the MT model, that the reaction rate in the M-section be a maximum, is shown to apply when maximizing the conversion for a given residence time as it was shown previously to apply when minimizing the residence time for a given conversion. Very good agreement is shown between theoretical and experimental results, confirming the superior results often obtained with an MT combination as compared with those given by a stirred tank or a tubular reactor under similar conditions. Bi-stable steady states of conversion have been achieved and their effect shown on the performance of the combined reactor. Les auteurs ont etudie le rendement d'un reacteur adiabatique MT, pour differentes conditions experimentales, au moyen de la reaction du thiosulphate de sodium avec le peroxyde d'hydrogene. La section M constituee d'un RHAC, est suivie d'un grand nombre de petits reservoirs bien agites, en serie, qui constituent la section T. On montre que le critere d'optimisation du modele MT, a savoir que la vitesse de reaction dans la section M soit maximum, s'applique aussi bien pour trouver la conversion maximum pour un temps de sejour donne, que pour determiner le temps de sejour minimum pour une conversion donnee. Les resultats theoriques et experimentaux sont en tres bon accord. Ils confirment que pour des conditions analogues, le reacteur combine MT peut souvent donner de meilleures performances que le reacteur agite ou le reacteur tubulaire. Selon les conditions, on a obtenu l'un ou l'autre des deux conversions stationnaires possibles; on montre leur effet sur le rendement du reacteur combine.

Momentum transfer in a horizontal liquid‐jet ejector

Abstract: The performance of a horizontal liquid-air ejector system was greatly enhanced by creating mixing shock. Principles of macroscopic momentum and energy balances were employed to define an overall loss factor which was found to be a useful correlating parameter in the case of homogeneous bubble flow. Empirical correlations are proposed to predict mass ratio as a function of different parameters.

The effect of concentration on the rates of dissolution of gibbsite and boehmite

Abstract: The effect of caustic soda concentration on the rate of dissolution of gibbsite and boehmite was studied. The activity of sodium hydroxide rather than cencentration was found to be the best parameter for kinetically describing the effect of concentration on dissolution rate. For the gibbsite reaction, a first order dependence on sodium hydroxide activity was observed whilst the boehmite dissolution exhibited a dependence on the term (aNaOH. aH2O) which was first order above 210 g/1 Na2O and half order below that concentration. On a etudie leeffet de la concentration de la soude caustique sur la dissolution de la gibbsite et de la boehmite. On a trouve que cetait plutǒt leactivite de lehydroxyde de sodium que sa concentration qui etait le meilleur parametre pour decrire par cinetique leeffet de la concentration sur la vitesse de dissolution. Dans le cas de la reaction de la gibbsite, on a observe une dependance de premier ordre de leactivite de lehydroxide de sodium; on a trouve, par contre, que la dissolution de la boehmite dependait du terme (aNaOH- aH2O) et que cette dependance etait de premier ordre pour une concentration excedant 210 g/1 de Na2O et deun demi-ordre au-dessous de la dite concentration.

Transient freezing in laminar tube‐flow

Abstract: A new model is presented for treating transient freezing in laminar tube-flow. The liquid motion is constrained by requiring head-loss versus flow-rate to match that of a linear pump-characteristic curve. This feature enables the model to describe freezing conditions which may lead to occlusion of the tube with solid-phase material. The results demonstrate the sensitivity of tube occlusion both to temperature and liquid-pumping capability. Both steady-state and transient results obtained compare favorably with those found in the literature, which include an exact steady-state solution. Maximum error is estimated at 15%. On presente un nouveau modele pour le traitement de la congelation temporaire qui se produit lors de l'ecoulement dans un tube laminaire. On restreint le mouvement du liquide en s'assurant que le rapport entre la perte de charge et le debit corresponde a celui d'une courbe caracteristique pour une pompe lineaire; cela permet au modele d'indiquer les conditions de congelation qui peuvent conduire a l'occlusion du tube avec des matieres solides. Les resultats qu'on a obtenus demontrent la sensibilite de l'occlusion du tube a la temperature et a la capacite de pompage du liquide. Les informations obtenues en regime permanent et en regime transitoire se comparent favorablement avec les donnees publiees, lesquelles comprennent une solution exacte en regime permanent. On considere que l'erreur maximale est de 15%.

Viscosity properties of suspensions at the limiting conditions for turbulent drag reduction

Abstract: On the basis of a postulated mechanism of drag reduction, the overall viscosity properties of suspensions are used to establish general quantitative criteria for the upper and lower limit on the conditions at which turbulent drag reduction can occur in suspensions of rigid, elongated, nearly neutrally-buoyant particles. Experimental data obtained in drag reducing suspensions of nylon fibres in water verified, quantitatively, the criterion for the upper limit. The experimental data obtained were not sufficient for a precise test of the lower limit; however, these data did show the existence of a practical lower limit, at a value slightly larger than the predicted one. En se basant sur un mecanisme admis de diminution de la forces de traǐnee, on a utilise les proprietes globales de la viscosite des suspensions pour etablir des criteres quantitatifs et generaux dans le cas des limites superieure et inferieure des conditions auxquelles une reduction de la force de traǐnee turbulente peut se produire dans des suspensions de particules rigides, allongees, dont la densite etait pratiquement celle du milieu. Les resultats experimentaux obtenus dans le cas de suspensions de fibres de nylon dans l'eau, ou il se produisait une diminution de la force de traǐnee, ont confirme la valeur du critere pour la limite superieure; les dits resultats n'ont pu fournir une verification precise pour ce qui est de la limite inferieure, mais ils ont montre l'existence d'une limite inferieure pratique dont la valeur excedait legerement celle qu'on avait prevue.

Drag reduction and turbulence modification in rigid particle suspensions

Abstract: Turbulent drag reductions on the order of 50% were obtained for pipe flow of submicron, rod-like particle suspensions at weight concentrations of less than 0.5%. Wall Reynolds numbers as high as 40,000 were obtained for the suspensions. The suspended particle configuration was rigid and non-elastic and was not affected by local strain rate fields. Longitudinal turbulence data are presented for two suspensions and for the Newtonian solvent at an average flow velocity of about 7 fps. Distinctly modified turbulence generation and dissipation were observed. The suspension exhibited smooth transitional flow behavior and increases in both macroscale and microscale. A particle length effect, or relaxation time effect, was observed with the larger relaxation time suspension exhibiting the more extreme flow and turbulence differences. On a obtenu une diminution de la force de traǐnee turbulente d'environ 50% dans le cas de l'ecoulement, dans des conduits, de suspensions de particules en forme de tiges et de grosseur inferieure a un micron, dont les concentrations en poids etaient moindres que 0.5%. On a trouve sur les parois des nombres de Reynolds allant jusqu'a 49,000 pour les suspensions. La configuration des particules en suspension etait rigide et depourvue d'elasticite; elle n'etait pas affectee par les taux de contrainte locale. On presente les resultats relatifs a la turbulence longitudinale dans le cas de deux suspensions et du solvant newtonien pour une vitesse moyenne d'ecoulement d'environ 7 pieds a la seconde. On a observe la production et la disparition d'une turbulence distinctement modifiee. Les suspensions se sont comportees comme un ecoulement calme de transition et ont manifeste des augmentations en grosses et petites particules. On a note un effet de la longueur des particules ou du temps de relaxation; on a trouve, dans la suspension dont le temps de relaxation etait le plus eleve, les differences les plus considerables dans l'ecoulement et la turbulence.

Theory of gas solubility in mixed solvent systems

Abstract: A simplified form of perturbation theory for mixtures is applied to the prediction of gas solubility in mixed solvent systems. A method for the determination of Henry's Law constants for gases as a function of solvent composition for any general multicomponent solvent mixture is presented. The theory requires molecular parameters and solvent density to predict the gas solubility. For the accurate prediction of solubility of complex molecules if is necessary to use gas solubility data for the pure solvent; however, solvent mixture activity coefficient data are not required. Comparisons with experimental results indicate that the theory works well for both polar and nonpolar solvent mixtures, provided that the dissolved gas does not chemically combine or associate with the solvents. On applique une forme simplifiee de la theorie de perturbation pour les melanges a la prediction de la solubilite des gaz dans des systemes formes de melanges de solvants. On presente une methode pour determiner les constantes de la Loi d'Henry pour les gaz en fonction de la composition des solvants et ce pour n'importe quel melange general de solvants a composants multiples. La theorie necessite l'emploi des parametres moleculaires et des densites des solvants pour predire la solubilite des gaz. Pour predire avec precision la solubilite de molecules complexes, il faut utiliser les donnees de solubilite du gaz dans le solvant pur; toutefois, il n'est pas necessaire d'employer les donnees relatives au coefficient d'activite du melange de solvants. Des comparaisons faites avec les resultats experimentaux indiquent que la theorie est satisfaisante dans le cas de melanges de solvants polaires ou non, pourvu que le gaz dissous ne se combine pas chimiquement avec les solvants.

New mixing rules for the BWR parameters to predict mixture properties

Abstract: New mixing rules which are general and easy to use have been developed to predict the properties of mixtures from the BWR equation. The rules contain a binary interaction parameter, readily obtainable from the experimental values of the second virial cross-coefficients. The mixing rules were used to predict the densities of binary mixtures of carbon dioxide with methane, ethane and propane at elevated pressures. For any of the three mixtures, the standard error of the predictions was approximately equal to or less than the sum of the standard errors of fit for the pure components. The BWR parameters for the pure components, required in the above predictions, were determined by minimizing the sum of relative error squares in specific volume.

Sequential statistical design strategy in an experimental kinetic study

Abstract: The value of using a sequential statistical design strategy is illustrated through its use in an experimental kinetic study of the oxidation of o-xylene over a vanadium oxide catalyst. The rate of oxidation of o-xylene was determined in a differential reactor over the following ranges of conditions: 270 to 300°C, (0.5 to 3.5) x 10-4 g.mole o-xylene/1., (1.0 to 10.0) x 10-3 g.mole oxygen/1. The statistical design strategy for precise parameter estimation was found to be effective in increasing the precision of the parameter estimates, in reducing the correlation between parameter estimates and in showing the magnitude of this problem, and in providing a reliable prediction of the value of carrying out additional runs. On illustre leimportance de leemploi deune stategic sequentielle de profil statistique en leutilisant dans une etude cinetique et experimentale de leoxydation de leorthoxylene sur de leoxyde de vanadium comme catalyseur. On a determine la vitesse deoxydation de leorthoxylene dans un reacteur differentiel dans les conditions suivantes: 270°C a 300°C, (0.5 a 3.5) x 10-4 g.mole deortho-xylene par litre, (1.0 a 10.0) x 10-3 g.mole deoxygene par litre. On a trouve que leemploi de la strategie de profil statistique pour levaluation precise des parametres permettait deameliorer la precision de cette evaluation, de diminuer la correlation entre les estimations des parametres, de demontrer leamplitude du probleme et de fournir une prediction fiable de leimportance de faire des experiences additionnelles.

Identification of one phase flow processes

Abstract: A method is presented for the identification of parameters in the partial differential equations describing the dynamic behaviour of a certain class of one phase flow processes. Included in this class of processes are certain types of heat exchangers and flow reactors in which axial and radial dispersion are not important. The approach employed is to reduce the partial differential equations to an extended system of ordinary differential equations with the method of characteristics. Once in this form the method of quasilinearization is employed to identify the parameters in these ordinary differential equations. On expose une methode pour identifier les parametres dans les equations differentielles partielles, qui servent a decrire le comportement dynamique deune certaine categorie de procedes decoulement en une phase. La dite categorie comprend certains genres dechangeurs de chaleur et de reacteurs pour ecoulement dans lesquels les dispersions axiales et radiales sont sans importance. La methode utilisee consiste a ramener les equations differentielles partielles a un systeme etendu dequations differentielles ordinaires au moyen de la methode des caracteristiques. On etudie alors la technique de quasi-linearisation pour identifier les parametres dans les dites equations differentielles ordinaires.

Evaluation and improvement of control vector iteration procedures for optimal control

Abstract: To improve the convergence rate to the optimal policy, a simple but effective way of determining the stepping parameter for the control policy adjustment is developed. The application of the proposed approach to four systems described by ordinary differential equations shows that the existing methods are improved considerably when the proposed method is incorporated. Afin deameliorer la vitesse de convergence pour queelle corresponde aux exigences de la methode de contrǒle optimal, on a mis au point un procede simple, mais efficace, de determiner le parametre dechelonnement en vue du reglage de la technique de contrǒle. Leapplication de la methode proposee a quatre systemes, definis par des equations differentielles ordinaires, indique queil y a une forte amelioration des methodes actuelles lorsqueon leur incorpore la technique proposee.

Some problems concerning the non-adiabatic tubular reactor a-priori bounds, qualitative behavior, preliminary uniqueness and stability considerations

Abstract: An investigation of the non-adiabatic tubular reactor, in which a single chemical reaction occurs, is presented. The steady state mass and heat balance equations are shown to be a pair of coupled, nonlinear differential equations, and are shown to uncouple into a single functional-differential equation for the case Le = 1. A-priori bounds on the steady state concentration and temperature are developed, and some remarks about the shape of the steady state profiles made. Sufficient conditions ensuring uniqueness of steady states and their asymptotic stability are derived. On presente les resultats d'une etude faite sur un reacteur tubulaire et non-adiabatique, dans lequel il se produit une seule reaction chimique. On montre que les equations de masse et d'equilibre de chaleur, en regime permanent, consistent en deux equations differentielles et non-lineaires associees, qui se ramenent a une seule equation differentielle fonctionnelle lorsque Le = 1. On etablit des limites a-priori sur la concentration et la temperature en regime permanent et fait des remarques sur l'allure des profils en regime permanent. On deduit des conditions qui permettent d'assurer l'aspect unique des regimes permanents et leut stabilite asymptotique.