scispace - formally typeset
Search or ask a question

Showing papers in "Canadian Journal of Chemical Engineering in 1989"


Journal ArticleDOI
TL;DR: In this article, an estimate of the best possible control can be obtained by fitting a univariate time series to process data collected under routine control, and the use of this technique is demonstrated with pilot plant and production data.
Abstract: For processes described by linear transfer functions with additive disturbances, the best possible control in the mean square sense is realized when a minimum variance controller is implemented. It is shown that an estimate of the best possible control can be obtained by fitting a univariate time series to process data collected under routine control. No ‘identifiabuity’ constraints need be imposed. The use of this technique is demonstrated with pilot plant and production data. Pour les procedes decrits par des fonctions de transfert lineaires avec des perturbations additives, le meilleur controle possible au sens des moindres carres s'obtient avec un regulateur a variance minimum. On montre qu'on peut obtenir une estimation du meilleur controle possible en adaptant une serie chronologique univariee pour traiter des donnees recueillies lors d'un retrocontrole de routine. Il n'est pas necessaire d'imposer des contraintes d'«identificabilite». L'utilisation de cette technique est decrite par des donnees d'une usine pilote et des donnees de production.

814 citations


Journal ArticleDOI
TL;DR: In this article, the kinetics of pyrolysis of lignocellulosic materials were studied with a view of providing simple kinetic models for engineering purposes, based on the results obtained by means of thermal analysis techniques.
Abstract: The kinetics of the pyrolysis of lignocellulosic materials was studied with a view of providing simple kinetic models for engineering purposes. Experimental data obtained by means of thermal analysis techniques suggest that the pyrolysis of fine particles (below 1 mm) can be considered to be controlled by pyrolysis kinetics. The rate of pyrolysis of one biomass type can be represented by the sum of the corresponding rates of the main biomass components (cellulose, lignin, hemicellulose). The kinetics of each of these components was simulated by a kinetic scheme capable of predicting the pyrolysis rate and the final weight-loss for a wide range of pyrolysis parameters including various heating conditions.

431 citations


Journal ArticleDOI
TL;DR: In this article, a four-lump model is proposed to describe the process of fluid catalytic cracking in which the deposition rate of coke on catalyst can be predicted from gas oil conversion and isolated from the C 1 − 4 gas yield.
Abstract: In the fluid catalytic cracking reactor heavy gas oil is cracked into more valuable lighter hydrocarbon products. The reactor input is a mixture of hydrocarbons which makes the reaction kinetics very complicated due to the involved reactions. In this paper, a four-lump model is proposed to describe the process. This model is different from others mainly in that the deposition rate of coke on catalyst can be predicted from gas oil conversion and isolated from the C1–C4 gas yield. This is important since coke supplies heat required for endothermic reactions occurring in the reactor. By this model we can also conclude that the C1–C4 gas yield increases with increasing reactor temperature, while production of gasoline and coke decreases.

149 citations


Journal ArticleDOI
TL;DR: In this paper, six Langmuir-Hinshelwood-Hougen-Watson models have been derived for the kinetics of conversion of carbon monoxide to hydrocarbons in the Fischer-Tropsch synthesis.
Abstract: Six Langmuir-Hinshelwood-Hougen-Watson models have been derived for the kinetics of conversion of carbon monoxide to hydrocarbons in the Fischer-Tropsch synthesis The models were fitted to experimental data obtained in an internal recycle reactor over a wide range of operating conditions Two models, one based on the hydrogenation of surface carbon and the other on a hydrogen-assisted dissociation of carbon monoxide as rate limiting steps were both able to provide a satisfactory fit to the experimental rate data A general model was also developed for the rate of methanation in the presence of higher hydrocarbons The same two rate limiting assumptions as those used in formulating the rate of total CO conversion are used in these models The two models were fitted to experimental data for methane formation It was the model assuming CH formation as rate limiting that showed the best fit for both CO conversion for CH4 formation

118 citations


Journal ArticleDOI
TL;DR: In this paper, a gravity drainage concept has been proposed and tested for in-situ recovery of bitumen by mobilization with soluble gases at ambient reservoir temperature conditions Experiments were done using carbon dioxide and ethane gases at ∼ 20°C to recover Athabasca bitumen from a scaled reservoir model.
Abstract: A gravity drainage concept has been proposed and tested for in-situ recovery of bitumen by mobilization with soluble gases at ambient reservoir temperature conditions Experiments were done using carbon dioxide and ethane gases at ∼ 20°C to recover Athabasca bitumen from a scaled reservoir model Thermal gravity drainage theory has been modified for the mass transfer case The measured drainage rates were higher than those predicted by the model using molecular diffusivity data but fit the model better using an increased effective diffusivity Lateral dispersion theory does not predict the high measured effective diffusivities A preliminary economic evaluation of field production indicates potential application to recovery of Lloydminster heavy oil

96 citations


Journal ArticleDOI
TL;DR: In this paper, the decomposition of a synthetic core of methane hydrate is modelled by coupling intrinsic kinetics with heat transfer rates, and numerical simulation results show the effects of incorporating the intrinsic kinetic rate of decomposition.
Abstract: Decomposition of a synthetic core of methane hydrate has been modelled by Selim and Sloan (1985) and Ullerich et al. (1987) based on heat transfer considerations. In the present work, the decomposition is modelled by coupling intrinsic kinetics with heat transfer rates. Numerical simulation results are presented to show the effects of incorporating the intrinsic kinetic rate of decomposition. Simulation results indicate that by changing the system pressure we can move from a heat transfer controlled regime to a regime where both heat transfer and intrinsic kinetics have a significant effect on the global rate of decomposition. La decomposition d'un noyau synthetique d'hydrate de methane a ete modelisee par Selim et Sloan (1985) et Ullerich et al. (1987) a partir de considerations sur le transfert de chaleur. Dans le present travail, la decomposition est modelisee en couplant la cinetique intrinseque aux taux de transfert de chaleur. On presente les resultats de la simulation numerique pour montrer les effets de l'introduction de la vitesse de la cinetique intrinseque de decomposition. Les resultats de la simulation indiquent qu'en variant la pression du systeme nous pouvons passer d'un regime regime controle par le transfert de chaleur a un regime dans lequel le transfert de chaleur et la cinetique intrinseque ont tous deux un effet significatif sur la vitesse globale de decomposition.

83 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a steady-state characterization of the two-phase flow using the average voidage profile and the net solids circulation rate of the core and annular regions.
Abstract: summary, given the pressure distribution along the CFB riser, or equivalently the average voidage profile and the net solids circulation rate, G, the model equations can be solved sequentially to provide a steady-state characterization of the two-phase flow. The gas and solids velocities provided by the model represent average values over the cross sectional area of the core and annular regions. However, if information is avail- able from similar units, a radial velocity distribution can be readily incorporated into the model to provide a more realistic representation of the flow. Kefa et al. (1988), for example, have found that the gas velocity follows the power law with the exponent n = 1/7. Simulation Results and Discussion The validity of the proposed model was tested using recently obtained experimental data available in the litera- ture (Bader et al., 1988; Horio et al., 1988; Brereton, 1987; Hartge et al., 1988). The experimental data employed in the evaluation cover a wide range of reactor sizes and operating conditions and are listed in Table 1. Each simulation has been performed by utilizing experimental average voidage profiles or pressure drop dis- tributions, as provided by the various authors, and by solving the model equations described

82 citations


Journal ArticleDOI
TL;DR: In this paper, an investigation into the effects of fuel boiling point and chemical type on the autoignition of single droplets of a number of pure hydrocarbons is reported.
Abstract: An investigation into the effects of fuel boiling point and chemical type on the autoignition of single droplets of a number of pure hydrocarbons is reported. Ignition delay times were measured using the suspended droplet technique, and a numerical model was developed to extract reaction rate constants for the fuels. The results show that both fuel boiling point and chemical kinetics are important contributors to the ignition delay. Une etude sur les effets du point d'ebullition et du type chimique du carburant sur l'allumage de gouttelettes individuelles de nombreux hydrocarbures, est presentee. Le delai d'allumage fut mesure pour des gouttelettes suspendues, et un modele mathematique fut developpe pour determiner les coefficients de reaction pour chaque carburant. Les resultats demontrent que le point d'ebullition ainsi que la cinetique chimique contribuent largement au delai d'allumage.

73 citations


Journal ArticleDOI
TL;DR: A test rig was designed and fabricated to measure local heat transfer coefficients from a large-diameter, steam-heated horizontal tube to thin falling films of water as discussed by the authors, which generally support the theory developed by Rogers for laminar film conditions, which were found to persist up to film Reynolds numbers of about 2000.
Abstract: A test rig was designed and fabricated to measure local heat transfer coefficients from a large-diameter, steam-heated horizontal tube to thin falling films of water. The results of the experiments generally support the theory developed by Rogers for laminar film conditions, which were found to persist up to film Reynolds numbers of about 2000. Agreement between theoretical predictions of heat transfer coefficients and the measured values is reasonable for the thermal boundary layer development region, but measured values are about 20% lower than predicted values in the developed region. The lower values in the developed region are attributed mainly to measured film thicknesses being greater than predicted values. Nous avons concu et fabrique une installation de forage experimental pour mesurer les coefficients de transfert de chaleur locaux d'un tube horizontal, chauffe a la vapeur, de gros diametre dans des films d'eau minces descendants. Les resultats des experiences confirmement en general la theorie elaboree par Rogers pour les conditions d'ecoulement en film laminaire, qui s'appliquent jusqu'a des nombres de Reynolds du film d'environ 2000. Les predictions theoriques des coefficients de transfert de chaleur et les valeurs mesurees concordent raisonnablement bien pour la region de developpement de la couche limite thermique, mais les valeurs mesurees sont environ 20% inferieures aux valeurs predites dans la region developpee. Ces valeurs inferieures dans la region developpee sont attribuees principalement aux epaisseurs mesurees du film qui se sont averees superieures aux valeurs predites.

71 citations


Journal ArticleDOI
TL;DR: In this paper, the Stryjek-Vera modification of the Peng-Robinson equation of state (PRSV) was applied to sixty-nine additional compounds of industrial interest.
Abstract: Pure - compound - parameters for the Stryjek-Vera modification of the Peng-Robinson equation of state, PRSV, are reported for sixty-nine additional compounds of industrial interest. Errors in the reproduction of pure compound vapor pressure are normally below 1% at reduced temperatures lower than 0.7 At reduced temperatures higher than 0.7, for a few compounds for which data are scarce, errors are somewhat higher than 1%.

64 citations


Journal ArticleDOI
TL;DR: In this article, an equation is derived to predict the minimum possible total residence time to achieve any desired substrate conversion, which is applied to Monod, substrate inhibition and product inhibition cases.
Abstract: The primary reactor type currently used in the production of microorganisms or microbial products is the stirred tank reactor (STR). If operated on a continuous flow basis (CFSTR) they become similar in performance to the primary reactor configuration used in most of the chemical industry. In this work, microbial kinetics are considered in the design of CFSTRs in series. An equation is derived to predict the minimum possible total residence time to achieve any desired substrate conversion. The equation permits the use of a wide variety of growth kinetic models and is applied here to Monod, substrate inhibition and product inhibition cases. For the majority of cases, it is found that three optimally designed CFSTRs in series provide close to the minimum possible residence time for any desired substrate conversion. A comparison to the use of a PFR is made for cases of both no-recycle and biomass recycle to the CFSTR train. It is found that three CFSTRs, which are not equi-volume, provide the same required total mean residence time as a PFR for Monod kinetics, but are significantly superior (i.e., less total volume required) to a PFR for substrate-inhibited growth. Le type de reacteur primaire habituellement utilise dans la production de microorganismes ou de produits microbiens est le reacteur agite (STR). En mode continu (CFSTR), la performance de ces reacteurs se compare a celle des reacteurs primaires utilises le plus souvent dans l'industrie chimique. On considere dans ce travail des cinetiques microbiennes pour la conception de reacteurs agites continus en serie. Une equation est etablie pour predire le temps de sejour total possible minimum pour obtenir les conversions voulues de substrat. Cette equation permet l'utilisation d'un large eventail de modeles cinetiques de croissance et est appliquee ici aux cas de Monod, de l'inhibition de substrat et de l'inhibition de produit. Dans la majorite des cas, on a trouve que trois reacteurs agites continus en serie concus de maniere optimale permettent de se rapprocher du temps de sejour possible minimum pour toute conversion de substrat desiree. On a effectue une comparaison entre ce type de reacteur et un PFR pour les cas d'un non-recyclage et d'un recyclage de biomasse dans la serie de reacteurs agites continus. On a trouve que trois reacteurs agites continus, qui n'ont pas le měme volume, donnent le měme temps de sejour moyen total requis qu'un PFR pour la cinetique de Monod, mais ils sont nettement plus performants (par exemple volume total requis moins important) que les PFR pour la croissance inhibee par le substrat.

Journal ArticleDOI
TL;DR: In this article, a mathematical model was developed to describe the minimum fluidization velocity behavior of a cocurrent, gas-liquid-solid fluidized bed with cylindrical hydrotreating catalysts under conditions of high gas holdup.
Abstract: Experiments were performed to study the hydrodynamic characteristics of a cocurrent, gas-liquid-solid fluidized bed containing cylindrical hydrotreating catalysts under conditions of high gas holdup. These conditions were established using an aqueous t-pentanol (0.5 wt. %) solution as the liquid phase in an attempt to simulate reaction conditions for hydrotreating of residual oils and coal liquefaction. Separate three-phase experiments were performed with air and water to investigate the effect of surface tension on hydrodynamic behavior. A mathematical model was developed to describe the minimum fluidization velocity behavior. Bed voidage, gas holdup and terminal velocity of the particles were analyzed and correlated empirically to investigate the effect of particle shape and liquid surface tension. A bubble-wakes interaction coefficient defined by Jean and Fan (1987) was determined for cylindrical particles.

Journal ArticleDOI
TL;DR: The applications of solid/ liquid and/or solid/liquid/gas fluidized beds are considered in such areas as environmental biotechnology for the nitrification and denitrification of wastewater, denitification of drinking water, anaerobic digestion, production of cell mass and primary and secondary metabolites with microorganisms, and cultivation of animal cell lines.
Abstract: The applications of solid/liquid and/or solid/liquid/gas fluidized beds are considered in such areas as environmental biotechnology for the nitrification and denitrification of wastewater, denitrification of drinking water, anaerobic digestion, production of cell mass and primary and secondary metabolites with microorganisms, and cultivation of animal cell lines. Cell mass and alcohol, glutathion, and enzyme production in gas/solid fluidized beds are also considered. The performance and modelling of these reactors are discussed.

Journal ArticleDOI
TL;DR: In this paper, a 102 mm diameter conventional cyclone operated with air heated to temperatures between 300 K and 2 000 K, was used for gas-solid separations in a 102mm diameter cyclone, where fractional collection efficiencies were measured for alumina and silica having particle sizes of 100% less than 44 μm.
Abstract: Experimental results for gas-solid separations in a 102 mm diameter conventional cyclone operated with air heated to temperatures between 300 K and 2 000 K, are presented. Overall and fractional collection efficiencies were measured for alumina and silica having particle sizes of 100% less than 44 μm and mass median diameters of 5.0 and 10.0 μm respectively. Inlet velocities ranged from three to 42 m/s and inlet dust loads were between 0.3 and 235 g/m3. The dust load had a strong influence on the collection efficiency and the loading effect was stronger at high temperatures.

Journal ArticleDOI
TL;DR: In this paper, the solubility of H2S, CO2 and their mixtures in a 3.43 molar solution of 2-amino-2-methyl-1-propanol (AMP) has been determined at 50°C at partial pressures between 4 and 5650 kPa.
Abstract: The solubility of H2S, CO2 and their mixtures in a 3.43 molar solution of 2-amino-2-methyl-1-propanol (AMP) has been determined at 50°C at partial pressures between 4 and 5650 kPa. A mathematical model has been used to correlate the data for the individual gases in the solvent. The parameters obtained have been used to predict the partial pressures in the four-component system. In general the predicted values are in good agreement with the experimental data.

Journal ArticleDOI
TL;DR: In this article, a forced circulation single-stage evaporator is considered, and a process model derived from fundamental mass and energy balances is presented to outperform single loop and predictive control strategies by a significant amount.
Abstract: This paper outlines the use of a process model directly in a control algorithm. The process considered, a forced circulation single-stage evaporator, is a nonlinear interacting process. The control strategy employing a process model derived from fundamental mass and energy balances is shown to outperform single loop and predictive control strategies by a significant amount. The control structure is first presented in general form and then specifically applied to this process.

Journal ArticleDOI
TL;DR: In this paper, a new impinging-jet reactor system was developed for the fast pyrolysis of particulate carbonaceous materials, which served to promote rapid uniform mixing between a fine particulate heat carrier and a particulate feedstock.
Abstract: A new impinging-jet reactor system has been developed for the fast pyrolysis (ultrapyrolysis) of particulate carbonaceous materials. The reactor system serves to promote rapid uniform mixing between a fine particulate heat carrier and a particulate feedstock in order to achieve the high heat transfer rates necessary for fast pyrolysis. Flow visualization experiments in a cold model testing unit indicated that the system performed effectively over a wide range of conditions. A sampling system utilizing isokinetic sampling probes was developed to investigate the small scale solids mixing. The effects of reactor geometry and operating conditions upon the solids mixing are reviewed. Un nouveau systeme de reacteur a jet a impact a ete mis au point pour la pyrolyse rapide (ultrapyrolyse) de materiaux particulaires carbones. Le reacteur sert a promouvoir un melange uniforme rapide entre un caloporteur de particules fines et une alimentation de particules dans le but d'obtenir les vitesses elevees de transfert de chaleur necessaires a la pyrolyse rapide. Des experiences de visualisation des ecoulements dans un systeme d'essai froid indiquent que ce dispositif donne des resultats performants pour un large eventail de conditions. On a mis au point un systeme d'echantil-lonnage utilisant des sondes isocinetiques pour etudier le melange des solides a petite echelle. Les effets de la geometrie du reacteur et des conditions operatoires sur le melange des solides sont etudies.

Journal ArticleDOI
TL;DR: In this paper, the effect of temperature on the viscosity of bitumen fractions was investigated by vacuum distillation of a large Cold Lake bitumen sample, and the results of the calculations were compared with the bitumen data.
Abstract: New data are presented for the effect of temperature on the viscosity of bitumen fractions, which were obtained by vacuum distillation of a large Cold Lake bitumen sample. The viscosity of these fractions differs by several orders of magnitude; from 4.3 mPaϵs for Cut 1 to 430 000 mPaϵs for Cut 4 at 30°C. Cut 5 is a glass-like solid at room temperature with a softening temperature of about 100°C, and has a viscosity of 800 000 mPaϵs at 120°C. The effect of temperature on the viscosity of each bitumen fraction is modelled very well with a two-parameter correlation that was shown to be valid generally for Alberta bitumens. The results of bitumen viscosity calculations, based on a simple liquid-mixture viscosity formula, are presented and compared with the bitumen viscosity data. De nouvelles donnees sont presentees pour l'effet de la temperature sur la viscosite de fractions de bitume, qui ont ete obtenues par distillation sous vide d'un large echantillon de bitumes de Cold Lake. La viscosite de ces fractions varie de plusieurs ordres de grandeur; de 4,3 mPaϵs pour la coupe 1 a 430 000 mPas pour la coupe 4 a 30°C. La coupe 5 est un solide semblable au verre a la temperature ambiante; sa temperature de ramollissement des cendres est d'environ 100°C et sa viscosite de 800 000 mPas a 120°C. L'effet de la temperature sur la viscosite de chaque fraction de bitume se modelise tres bien par une correlation a deux parametres qui s'est averee generalement valide pour les bitumes d'Alberta. Les resultats des calculs de viscosite des bitumes, bases sur une formule simple de viscosite de melange liquide, sont presentes et compares a des donnees de viscosite de bitumes.

Journal ArticleDOI
TL;DR: In this paper, the hydrodynamics of fluidization for two thin "two-dimensional" fluidized beds, one containing a centrally located rectangular obstacle and the other containing three square tubes roughly approximating a portion of a fluidized bed combustor (FBC), was solved using the FLUFIX/MOD2 computer program.
Abstract: The hydrodynamics of fluidization for two thin ''two-dimensional'' fluidized beds, one containing a centrally located rectangular obstacle and the other containing three square tubes roughly approximating a portion of a fluidized bed combustor (FBC), was solved using the FLUFIX/MOD2 computer program. The monolayer energy dissipation erosion model extended to include solids viscous stress was compared with the Finnie erosion model. Hydrodynamic and erosion convergence studies were performed for the first bed. Computed erosion rates from the monolayer energy dissipation erosion model compare more favorably for both beds with available erosion data than those from the Finnie erosion model. 27 refs., 15 figs.

Journal ArticleDOI
TL;DR: In this article, experimental data were presented for the liquid-liquid-vapour equilibrium for the system water-hydrogen sulphide, and conditions ranged from the hydrate-LV quadruple point (29.4°C and 2.23 MPa) to beyond the critical temperature of hydrogen sulphide (100.3°C).
Abstract: Experimental data are presented for the liquid-liquid-vapour (LLV) equilibrium for the system water-hydrogen sulphide. Conditions ranged from the hydrate-liquid-liquid-vapour quadruple point (29.4°C and 2.23 MPa) to beyond the critical temperature of hydrogen sulphide (100.3°C). The maximum temperature at which three phases can exist is 106.2°C at 9.39 MPa. This is 6°C higher than previously believed.

Journal ArticleDOI
TL;DR: In this paper, a simple kinetic model has been used to simulate catalytic naphtha reformers, and a sensitivity analysis of operating parameters on reactor performance revealed that, while temperature affects the aromatics production significantly, the effect of pressure is negligible.
Abstract: A simple kinetic model has been used to simulate catalytic naphtha reformers. The model idealises naphtha to three constituents, namely, paraffins, naphthenes and aromatics, with average properties assigned to each class. Out of the many reactions the mixture can undergo, four major reactions have been considered for which the kinetic parameters have been estimated using plant production data. The reactor model is validated against two different sets of plant data. The agreement between predicted results and observations is generally good. A sensitivity analysis of operating parameters on reactor performance revealed that, while temperature affects the aromatics production significantly, the effect of pressure is negligible. Un modele cinetique simple a ete utilise pour simuler des reformeurs de naphta catalytiques. Dans ce modele, le naphta est represente par trois composants, soit les paraffines, les naphtenes et les aromatiques, avec des proprietes moyennes attribuees a chacun des groupes. Outre les nombreuses reactions que le melange peut subir, quatre reactions principales ont ete considerees pour lesquelles les parametres cinetiques ont ete estimes en utilisant des donnees de production d'une installation. Le modele de reacteur est valide en confrontant deux series differentes de donnees de production. L'accord entre les resultats predits et les observations est generaalement satisfaisant. Une analyse de sensibilite des effets des parametres operatoires sur la performance du reacteur revele que l'effet sur la pression est negligeable, alors que la temperature exerce un effet important sur la production des aromatiques.

Journal ArticleDOI
TL;DR: In this article, different correlations used for predicting the minimum fluidization velocities of binary systems were evaluated and compared, based on the experimental data obtained from the published literature and from this work.
Abstract: The fast defluidization method was used to measure the minimum fluidization velocities of binary systems. Based on the experimental data obtained from the published literature and from this work, different correlations used for predicting the minimum fluidization velocities of binary systems were evaluated and compared. On a utilise la methode de defluidisation rapide pour mesurer les vitesses minimales de fluidisation de systemes binaires. A partir des donnees experimental deja publiees et d'autres obtenues dans les presents travaux, differentes correlations utilisees pour la prediction des vitesses minimales de fluidisation de systemes binaires ont ete evaluees et comparees.

Journal ArticleDOI
TL;DR: In this article, instantaneous and time-averaged local bed-to-wall heat transfer coefficients were measured in a 9.3 m tall, 152 mm ID cold model circulating fluidized bed riser at three different heights for 171 μm Ottawa sand at a superficial gas velocity of 7 m/s, and for solids circulation fluxes up to about 70 kg/m2.
Abstract: Instantaneous and time-averaged local bed-to-wall heat transfer coefficients were measured in a 9.3 m tall, 152 mm ID cold model circulating fluidized bed riser at three different heights for 171 μm Ottawa sand at a superficial gas velocity of 7 m/s, and for solids circulation fluxes up to about 70 kg/m2.s. All data were obtained with an instantaneous heat transfer probe consisting of a thin platinum film deposited on a 1 cm2 piece of glass protected by a thin plastic film. Instantaneous heat transfer coefficients in the riser showed sudden and dramatic peaks caused by strands or sheets of particles sweeping past the probe. Consistent with previous work, time-averaged coefficients varied nearly linearly with suspension density. The heat transfer coefficient decreased from the bottom to the middle of the column, and then increased near the top due to an increase in suspension density for the exit geometry employed. Des coefficients locaux de transfert de chaleur lit-paroi instantanes et moyennes dans le temps, ont ete mesures dans une colonne a lit fluidise en circulation froid ayant 9,3 m de hauteur et 152 mm de diametre interieur, a trois hauteurs differentes, pour du sable d'Ottawa de 171 μm, a une vitesse de gaz superficielle de 7 m/s, et pour des flux de circulation de solides allant jusqu'a 70 kg/m2.s. Toutes les donnees ont ete obtenues a l'aide d'une sonde de transfert de chaleur instantane constituee d'un film de platine mince depose sur un morceau de verre de 1 cm2 protege par un film de plastique mince. Les coefficients de transfert de chaleur instantanes dans le colonne ont montre des pics importants et soudains dus a des morceaux de particules circulant autour de la sonde. En accord avec des travaux anterieurs, les coefficients de transfert de chaleur moyennes dans le temps varient presque lineairement avec la densite de suspension. Le coefficient de transfert de chaleur diminue du bas jusqu'au milieu de la colonne, puis augmente pres du haut de la colonne en raison d'une augmentation de la densite de suspension pour la geometrie de sortie employee.

Journal ArticleDOI
TL;DR: In this article, a semi-theoretical relation for the effective shear rate of liquid phase volumetric mass transfer coefficients for oxygen was derived in three-phase fluidized beds of 8 mm glass spheres fluidized by a cocurrent flow of air and pseudoplastic polysaccharide solutions (carboxymethyl cellulose, xanthan).
Abstract: Liquid phase volumetric mass transfer coefficients for oxygen were determined in three-phase fluidized beds of 8 mm glass spheres fluidized by a cocurrent flow of air and pseudoplastic polysaccharide solutions (carboxymethyl cellulose, xanthan). A semi-theoretical relation for the effective shear rate was suggested. The mass transfer coefficients could be correlated, together with literature data for particle diameters of 3 mm and 5 mm in other liquids, using the terminal velocity as the particle-specific property.

Journal ArticleDOI
TL;DR: In this paper, the hold-up behaviors of a froth flotation column were linked together using the drift-flux model using the Richardson-Zaki equation, and the ratio of the gas drift flux, jgf, to the bubble terminal velocity, V, for both the bubbly and the froth zones was found to be well correlated.
Abstract: The flow characteristics of a froth flotation column have been experimentally studied using air and aqueous surfactant solutions without the presence of solids. The hold-up behaviours of the bubbly and the froth zones of the column were linked together using the drift-flux model. The ratio of the gas drift-flux, jgf, to the bubble terminal velocity, V, for both the bubbly and the froth zones was found to be well correlated by the Richardson–Zaki equation: On a etudie de maniere experimentale les caracteristiques d'ecoulement d'une colonne de flottation par mousse en utilisant des solutions gazeuses et aqueuses de composes tensio-actifs en l'absence de solides. Les comportements de retention des zones mousseuse et bulleuse de la colonne ont ete relies a l'aide du modele de flux-derive. On a trouve une bonne correlation du rapport entre le flux-derive du gaz, jgf, et la vitesse terminale des bulles, V∞, tant pour la zone de bulles que pour la zone de mousse, par l'equation de Richardson-Zaki:

Journal ArticleDOI
TL;DR: In this paper, an adaptive strategy which combines effective adaptive random search (ARS) and statistical ridge analysis steps is developed to simultaneously estimate the parameters and to reduce a complex kinetic model, which can save computational time because the estimation is not repeated with each reduced model.
Abstract: In order to simultaneously estimate the parameters and to reduce a complex kinetic model, an adaptive strategy which combines effective adaptive random search (ARS) and statistical ridge analysis steps is developed. As demonstrated, this strategy can save computational time because the estimation is not repeated with each reduced model. The use of ARS is preferred for highly nonlinear models and cases having multiple parameter constraints, guaranteeing reliability for interactively obtaining the global reduced model parameter solution. Dans le but d'estimer simultanement les parametres et de reduire un modele cinetique complexe, on a mis au point une strategie adaptative qui combine une recherche aleatoire adaptative (ARS) effective et des phases d'analyse de crětes statistiques. Comme il a ete demontre, cette strategie permet de reduire le temps de calcul sur ordinateur du fait que l'estimation n'est pas repetee avec chaque modele reduit. L'utilisation de la methode ARS est preferable pour les modeles hautement non lineaires et les cas ayant des contraintes de parametres multiples, ce qui garantit la fiabilite pour obtenir de maniere interactive la solution globale des parametres des modeles reduits.

Journal ArticleDOI
TL;DR: In this article, a lumiere des donnees publiees par Carroll et Mather (1989) present a nouvelle interpretation des donnes ajustees souvent citees de Selleck, Carmichael et Sage (1952) pour l'equilibre de phase dans le systeme eau-hydrogene sulfure.
Abstract: A la lumiere des donnees publiees par Carroll et Mather (1989), on presente une nouvelle interpretation des donnees ajustees souvent citees de Selleck, Carmichael et Sage (1952) pour l'equilibre de phase dans le systeme eau-hydrogene sulfure. Les donnees de Carroll et Mather montrent que le point triple liquide-liquide-vapeur est valide a des temperatures plus elevees que ne le pensaient Selleck et al.. Les donnees experimentales issues de plusieurs sources sont correlees a l'aide de la modification de Stryjek-Vera (1986a) de l'equation d'etat de Peng-Robinson (1976). On demontre que le calage des donnees brutes par l'equation d'etat est aussi valable que le lissage de selleck et al


Journal ArticleDOI
TL;DR: The correlation of slip velocity using a large bank of published data for pulsed perforated plate, Karr reciprocating-plate, rotating disc and spray extraction columns is presented in this article.
Abstract: The correlation of slip velocity using a large bank of published data for pulsed perforated-plate, Karr reciprocating-plate, rotating disc and spray extraction columns is presented. Based on more than 3,700 data points with and without mass transfer, empirical equations not including hold-up for each of the columns are suggested which reproduce the slip velocity data over a wide range of variables. Explicit correlations for hold-up in both the loose and dense-packed regions of operation in spray columns are also presented which do not involve slip velocity. The equations presented are more exact and simpler to use than previous empirical correlations; these often involve the characteristic velocity which is difficult to accurately predict.

Journal ArticleDOI
TL;DR: In this article, a physical model for the prediction of transition to slug flow is presented, which assumes that the slug is formed as a result of a hydraulic jump which is sufficient to just touch the top wall of the conduit.
Abstract: A physical model for the prediction of transition to slug flow is presented. The model assumes that the slug is formed as a result of a hydraulic jump which is sufficient to just touch the top wall of the conduit. This, together with a ‘breaking dam’ assumption at the rear of the slug, gives necessary and sufficient conditions for the formation of a stable slug. The minimum liquid film thickness ahead of the slug, degree of aeration within the slug and slug translational velocity are predicted. The predictions agree very well with those of previous workers and with experimental data. On presente un modele physique pour la prediction de la transition a l'ecoulement piston. Le modele suppose que le bouchon se forme a la suite d'un saut hydraulique juste suffisant pour toucher la paroi superieure du conduit. Cette hypothese, jointe a une hypothese de «barrage de rupture» a l'arriere du bouchon, fournit les conditions conduisant a la formation d'un bouchon stable. On donne les predictions pour l'epaisseur minimale du film liquide en avant du bouchon, le degre d'aeration a l'interieur du bouchon ainsi que la vitesse de transition du bouchon. Ces predictions montrent un tres bon accord avec les travaux anterieurs et les donnees experimentales.