Showing papers in "Canadian Journal of Chemical Engineering in 1986"

PRSV: An improved peng—Robinson equation of state for pure compounds and mixtures

Abstract: The temperature and acentric factor dependence of the attractive term of the Peng—Robinson equation of state have been modified. The introduction of a single pure compound parameter allows the accurate reproduction of the vapor pressure data for a wide variety of substances. Nonpolar, polar nonassociating and associating compounds are equally well represented by the cubic PRSV equation of state. The conventional one-binary-parameter mixing rule allows the correlation of the vapor—liquid equilibrium data for a wide variety of binary systems. Only for systems formed by a polar compound (associating or not) and a saturated hydrocarbon, are results poorer than those obtained with conventional excess Gibbs energy functions.

The permeability of fibrous porous media

Abstract: The literature was searched for experiments and theories related to low-Reynolds-number flow through fibrous porous media, particularly highly porous structures. Experimental data were found for a wide range of materials, from polymer chains to fiberglass, and the results collapse reasonably well when the appropriate dimensionless co-ordinates are employed. Of the theories, accurate solutions of Stokes equation are available for regular arrays of parallel rods, either aligned with or normal to the flow. For irregular arrays and three-dimensional media, approximate permeabilities can be calculated from several flow models.

Contacting modes and behaviour classification of gas—solid and other two-phase suspensions

Abstract: An attempt is made to extend schemes for classifying the behaviour of gas—solid contacting modes and other two-phase systems. The regime diagram approach of Reh (1971) is modified and extended to cover the operating regions of common reactors and contactors where a gas flows upwards through a bed of solids including fixed and moving packed beds, conventional fluidized beds, circulating beds, spouted beds, and pneumatically conveyed suspensions. New boundaries are proposed between groups A and B and between groups B and D of the Geldart (1972, 1973) powder classification scheme. These boundaries reflect more recent data and allow the classification scheme to be used for gases other than air and for temperatures and pressures other than atmospheric.

Phase equilibria of oil, gas and water/brine mixtures from a cubic equation of state and henry's law

Abstract: This paper presents the predictions and calculations of the phase equilibria of oil, gas and water/brine mixtures where the oil and gas are modeled by a cubic equation of state and where the gas solubility in the aqueous phase is estimated from Henry's law. Henry's law constants for a variety of compounds of interest to the petroleum industry are correlated against pressure and temperature. The scaled-particle theory is used to take into account the presence of salt in the aqueous phase. An extensive match of experimental data is presented, showing the adequacy of the proposed model for Henry's law constant.

“PRSV — An improved peng‐robinson equation of state with new mixing rules for strongly nonideal mixtures”

Abstract: Two new composition dependent mixing rules for cubic equations of state are proposed. Both mixing rules contain two adjustable binary parameters and reduce to the conventional one parameter mixing rule when the parameters are equal. Vapor-liquid equilibrium data for mixtures of polar (associated or not) compounds with saturated hydrocarbons and for systems water/alcohol have been used to test the new mixing rules applied to the PRSV cubic equation of state. For these highly nonideal systems, correlation of the data with a new mixing rule of the Van Laar type for the PRSV equation gives better results than those obtained using excess Gibbs energy functions like the Wilson equation, NRTL and UNIQUAC.

Viscosity of compressed athabasca bitumen

Abstract: New data for the effect of pressure and temperature on Athabasca bitumen viscosity are presented The viscosity data cover a temperature range of 43–120°C and pressures up to 10 MPa It is shown that the compression of bitumen results in a significant increase in its viscosity but only a small increase in its density Also presented are correlations that include the effect of pressure and temperature on the viscosity of the bitumen On presente de nouvelles donnees sur l'influence de la pression et de la temperature sur la viscosite du bitume d'Athabasca Les donnees de viscosite ont ete obtenues pour des temperatures comprises entre 43 et 120°C et des pressions jusqu'a 10 MPa On montre que la compression du bitume entraǐne une augmentation importante de sa viscosite tandis que l'on n'observe qu'une faible augmentation de sa densite On presente egalement des correlations decrivant l'influence de la pression et de la temperature sur la viscosite du bitume

Kinetics of oil extraction from canola (rapeseed)

Abstract: The extraction of oil from canola (rapeseed) using hexane as a solvent can be described by a two stage washing/diffusion model. Oil which is at the surface of the seed as a result of pressing or cooking is removed rapidly at the beginning of the extraction process by simple washing by the solvent. This is followed by a slow extraction of the oil from the seed by a diffusional process. This latter process appears to be controlled by two mechanisms: slow, unhindered diffusion of oil held in the ruptured cells in the seed; and very slow, hindered diffusion of oil held within unruptured cells in the seed. To evaluate this model, rapeseed was extracted with commercial hexane in a simple bench scale batch extractor and the effects of variables such as particle thickness, temperature, cooking, degree of agitation, and solvent-to-seed ratio were studied. On peut decrire, au moyen d'un modele impliquant deux etapes de lavage/diffusion, l'extraction de l'huile de la graine de colza, pour l'hexane employe comme solvant. L'huile qui se trouve a la surface de la graine a la suite d'un pressurage ou d'une cuisson, est enlevee rapidement au debut du precede d'extraction par simple effet de lavage par le solvant. II se produit ensuite une extraction lente de l'huile de la graine par un processus de diffusion. Ce dernier semble controle par deux mecanismes, a savoir (a) une diffusion libre lente de l'huile retenue dans les cellules brisees de la graine et (b) une diffusion contrainte tres lente de l'huile retenue dans les cellules non brisees de la graine. Pour evaluer le modele, on a extrait la graine de colza avec de l'hexane commercial dans un simple extracteur discontinu de laboratoire et l'on a etudie les effets de variables telles que l'epaisseur des particules, la temperature, la cuisson, le degre d'agitation et la proportion solvant/grain.

A correlation for gas holdup in turbulent coalescing bubble columns

Abstract: A review of existing literature for the purpose of comparing correlations which allow the explicit predictiosn of gas holdup in two- or three-phase bubble columns shows wide disagreement concerning the effect of various variables. Further, various correlations, apparently of equal validity, show equally wide disagreement in the predicted absolute values of gas holdup among three test systems; water-air, hydrocarbon solvent—air, and trichloroethytene air. Some possible reasons for these disagreements are discussed. Extensive gas holdup data obtained in a 0.30 m diameter column for the three test systems were correlated statistically for the transition and the turbulent region. The resulting correlation gives agreement with experiment to within ±20%, with most data showing ± 10% agreement. The proposed correlation was also tested against thirteen data sets (from eight researchers) which corresponded to its region of validity and gave good agreement. Three additional relevant data sets were not satisfactorily predicted. On a precede a une etude bibliographique dans le but de comparer des correlations permettant de predire explicitement la retention des gaz dans des colonnes a bulles a deux ou trois phases et on a montre que ces correlations ne s'accordent pas sur l'effet des differentes variables. De plus, diverses correlations, apparemment de měme validite, montrent egalement un desaccord dans les valeurs absolues predites pour la retention des gaz dans le cas de trois systemes-tests: eau-air, solvant a base d'hydrocarbures–air et trichlorethylene-air. On analyse quelques raisons pouvant expliquer ces desaccords. On a correle de maniere statistique un grand nombre de donnees de retention des gaz obtenues dans une colonne de 0,30 m de diametre pour les trois systemes-tests, dans la region de transition et la region turbulente. L'ecart entre la correlation obtenue et l'experience est de ±20%, la majorite des donnees ne presente pas d'ecart superieur a ± 10%. La correlation proposee a ete egalement testee avec treize series de donnees (produites par huit chercheurs differents) compatibles avec sa region de validite et montre un bon accord. Trois autres series de donnees pertinentes ont ete predites de maniere non satisfaisante.

Correlations for prediction of diffusion in liquids

Abstract: Based on an extensive experimental data collection (about 1925 points), empirical correlations for the estimation of binary liquid diffusion coefficients have been developed. The new correlations for organic mixtures and for aqueous solutions (including dissolved gases) require only well known and simple parameters like the viscosity of the solvent and the molar volumes of solute and solvent at the normal boiling point. They are shown to predict the limiting diffusion coefficients with the same or sometimes better accuracy than established correlations which make use of additional parameters. The concentration dependence of the mutual diffusion coefficients can be estimated from the knowledge of the two limiting diffusion coefficients and thermodynamic data. Established equations are investigated and classified for different groups of systems e.g. nonpolar + nonpolar, nonpolar + polar and polar + polar liquid mixtures. On a developpe des correlations empiriques pour l'estimation des coefficients de diffusion binaires en phase liquide en s'appuyant sur un grand nombre de donnees experimentales (environ 1925 points experimentaux). Ces nouvelles correlations developpees pour les melanges organiques et les solutions aqueuses (y compris des gaz dissous) n'utilisent que des parametres simples et connus comme la viscosite du solvant et les volumes molaires du solute et du solvant au point d'ebullition normal. On montre qu'ils predisent les coefficients de diffusion limites avec la měme precision, ou parfois une meilleure precision que les correlations usuelles qui utilisent des parametres supplementaires. La variation des coefficients de diffusion mutuels en fonction de la concentration peut ětre estimee en connaissant les deux coefficients limites et de donnees thermodynamiques. Les equations usuelles ont ete etudiees et classifiees pour differents groupes de systemes, par exemple les melanges de liquides polaire + polaire, non polaires + polaire et non polaire + non polaire.

The gas disengagement technique for studying gas holdup structure in bubble columns

Abstract: By recording the drop in dispersion height after stopping the gas supply, the fractions of large and small bubbles, the respective swarm rise velocities, and the contributions to the overall gas flow can be determined. Some problems of the analysis are discussed in detail. The efficiency of the technique is demonstrated for the results obtained with two different gas distributors in a bubble column of 30 cm diameter. Il est possible de determiner les fractions respectives des petites et des grosses bulles, les vitesses d'ascension de leurs populations respectives ainsi que les contributions a l'ecoulement global du gaz, en mesurant la chute de la hauteur de dispersion apres l'arrět de l'alimentation du gaz. Certains problemes rencontres lors de l'analyse sont discutes en detail. L'efficacite de la technique est illustree pour les resultats obtenus avec deux distributeurs de gaz differents dans une colonne a bulles de 30 cm de diametre.

Catalytic conversion of canola oil to fuels and chemical feedstocks Part I. Effect of process conditions on the performance of HZSM‐5 catalyst

Abstract: The conversion of canola oil to hydrocarbons using a shape selective zeolite catalyst is reported in this work. Canola oil was passed over HZSM-5 catalyst in a fixed bed micro-reactor and the effects of reaction temperature and oil space velocity on the conversion and selectivity were studied using a statistical experimental design. The results show that 60–95 wt% of the canola oil can be converted to hydrocarbons in the gasoline boiling range, light gases and water. The gasoline fraction contained 60–70 wt% of aromatic hydrocarbons and the gases were mostly C3 and C4 paraffins. Furthermore, the spent catalyst could be regenerated completely at 600°C in 1 h with dry air. Dans cette etude, on decrit la conversion de l'huile de colza en hydrocarbures au moyen d'un catalyseur selectif de type zeolithe. L'huile de colza a ete passee sur un catalyseur HZSM-5 dans un microreacteur a lit fixe pour etudier l'influence de la temperature de reaction et du temps de passage de l'huile sur la conversion et sur la selectivite a l'aide d'un plan experimental statistique. Les resultats montrent que 60 a 95% en poids de l'huile de colza peuvent etre convertis en hydrocarbures dans la gamme de points d'ebullition de l'essence, en gaz legers et en eau. La fraction essence contient de 60 a 70% en poids d'hydrocarbures aromatiques et les gaz obtenus sont principalement des paraffines en C3 et C4. Par ailleurs, le catalyseur employe peut etre completement regenere a 600°C en une heure avec de l'air sec.

Generalized correlations for the aqueous liquefaction of lignocellulosics

Abstract: This paper shows that liquefaction (i.e. solubilization) of lignocellulosics in aqueous phase and in the absence of catalysts results in two general correlations. The extents of solubilization of both holocellulose and lignin are linearly related to overall conversion within the temperature range 150–270°C and up to conversions of 83%. Cet article presente l'evidence experimentale concernant deux correlations generales observees lors de la liquefaction (i.e. solubilisation) des matieres lignocellulosiques en phase aqueuse et en absence de catalyseurs. Les niveaux de solubilisation de l'holocellulose et de la lignine sont relies de facon lineaire a la conversion dans la plage de temperature comprise entre 150 et 270°C et pour des conversions allant jusqu'a 83%.

Flooding in inclined pipes — Effect of entrance section

Abstract: Flooding in countercurrent flow of air and water in inclined tubes has been investigated. Data on flooding inception in the whole range of inclinations have been collected and predictive models for calculating the flooding conditions as a function of the flow rates and pipe inclination were proposed. Special attention is placed on the effect of the liquid injection mode. It has been shown that the porous injection system causes a local disturbance and enhances flooding at relatively shallow inclinations and high liquid flow rates. L'engorgement d'un eacoulement a contre-courant d'air et d'eau a ete etudie dans des tubes inclines. On a reuni des donnees sur le seuil d'engorgement dans toute la gamme d'inclinations et des modeles sont proposes pour la prediction des conditions d'engorgement en fonction des debits et de l'inclination des tubes. On s'est particulierement interesse a l'effet du mode d'injection du fluide. Un systeme d'injection poreux entraine une pertubation locale et augmente l'engorgement a des inclinations relativement faibles et aux debits de liquide eleves.

Size of bubbles and liquid circulation in a bubble column with a draught tube and sieve plate

Abstract: The size distribution of bubbles and the liquid circulation in a bubble column with a draught tube and sieve plate were studied experimentally. The size of bubbles is well correlated with the previous result of the authors; the size distribution data are fitted reasonably well by a logarithmic normal probability distribution. Gas holdup in the draught tube and annulus and pressure drop were measured and correlations for these parameters are obtained. An energy balance is used to predict liquid circulating velocity using gas holdup and pressure drop correlations. Reasonable agreement is found between the calculated and measured circulating velocity. On a etudie de maniere experimentale la distribution de taille des bulles et la circulation du liquide dans une colonne a bulles munie d'un tube d'aspiration et d'un plateau perfore. La taille des bulles est correlee de maniere satisfaisante avec les resultats precedents des auteurs; les donnees de la repartition de la taille suivent raisonnablement bien la courbe logarithmique normale de distribution des probabilites. La retention des gaz dans le tube d'aspiration et dans l'espace annulaire, ainsi que la perte de charge ont ete mesurees et des correlations ont ete obtenues pour ces parametres. On a utilise un bilan d'energie pour predire les vitesses de circulation du liquide a partir des correlations pour la retention du gaz et pour la perte de charge. On a obtenu un accord raisonnable entre les valeurs mesurees et calculees de la vitesse de circulation.

Ethanol production by extractive fermentation – solvent identification and prototype development

Abstract: The in situ removal and recovery of inhibitory fermentation products by solvent extraction has numerous beneficial effects (increased reaction rate, fermentation of concentrated feeds, decreased water usage, etc.) which have been confirmed on theoretical grounds. For the development of such an extractive fermentation process, the identification of solvents having desirable physical properties as well as complete biocompatibility with the microorganism is an absolute prerequisite, which, to this point, has not been adequately met. By means of a computer data base, we have systematically screened 1,361 solvents for their suitability for use in an extractive ethanol fermentation, and, through subsequent experimental evaluation of 70 of these solvents, have identified 19 as being appropriate for use in a continuous extractive fermentation process. Details of this screening procedure, and physico-chemical data of the suitable extraction solvents are presented. A prototype extractive fermentation system, the first to employ a Continuous Stirred Tank Fermentor, is described. Results from mass transfer experiments in this prototype system, together with extractive fermentation experiments involving medium-strength (ca. 150 g/L) glucose feeds are discussed. La separation in situ et la recuperation par extraction au solvant des produits de fermentation inhibiteurs ont de nombreux effets positifs (vitesse de reaction accrue, fermentation d'alimentation concentree, economie d'eau, etc.) confirmes sur des bases theoriques. Pour la mise au point d'un tel precede de fermentation extractive, l'identification de solvants possedant les proprietes physiques requises et etant egalement completement bio-compatibles avec le microorganisme, est une necessite absolue, probleme qui n'a encore pas ete resolu de maniere adequate. On a examine systematiquement 1361 solvants pour leur capacite a ětre utilises dans la fermentation extractive de l'ethanol, a l'aide d'une base de donnees informatiques. Apres avoir effectue une evaluation experimentale de 70 de ces solvants, 19 ont ete reconnus comme appropries pour un precede continu de fermentation extractive. On donne le detail de la procedure de selection et on presente les donnees physico-chimiques des solvants d'extraction retenus. Un prototype du systeme de fermentation extractive, le premier a utiliser un fermenteur a reservoir agite continu, est decrit. Des resultats provenant d'experiences de transfert de matiere menees dans ce prototype, de měme que d'experiences de fermentation extractive utilisant du glucose de teneur moyenne (ca. 150 g/L) comme alimentation, sont egalement analyses.

Catalytic conversion of canola oil to fuels and chemical feedstocks: Part II Effect of co‐feeding steam on the performance of HZSM‐5 catalyst

Abstract: Ca lola oil and steam were co-fed continuously to a 15.5 mm i.d. fixed-bed reactor loaded with HZSM-5 catalyst at varying process conditions. The liquid hydrocarbon product contained 60–70 wt% aromatics. The gas product was highly olefinic, while for canola oil alone it was mostly paraffinic. The C2-C5 olefin selectivity increased with an increase in the steam/canola oil ratio in the feed. In addition, co-feeding with steam resulted in a two-fold increase in the catalyst life. Though the exact role of steam in altering the chemistry of the reaction is not known, it is probable that the rates of olefin formation and aromatization reactions are affected by the presence of steam. The product pattern suggests the possibility of propene being the initial olefin in the reaction scheme. De l'huile de colza et de la vapeur ont ete introduites simultanement en continu dans un reacteur a lit fixe de 15, 5 mm de diametre interieur charge avee un catalyseur HZSM-5 dans differentes conditions de fonctionnement. La fraction hydrocarbure liquide produite contient 60 a 70% en poids d'aromatiques. La fraction gazeuse est hautement olefinique alors que lorsque l'huile de colza est alimentee seule, elle est essentiellement paraffinique. La selectivite en olefines en C2—C5 croit avec une augmentation du rapport vapeur-huile de colza dans l'alimentation. De plus, la co-alimentation avee la vapeur permet de doubler la duree de vie du catalyseur. Bien que l'on ne connaisse pas le role exact de la vapeur dans la modification de la chimie de la reaction, il est probable que les vitesses de formation des olefines et de la reaction d'aromatisation soient influencees par la presence de vapeur. La structure du produit permet de croire que le propene serait l'olefine initiale dans le schema de reaction.

Modelling of the acetone‐butanol fermentation with cell retention

Abstract: A mathematical model for the kinetics of the acetone-butanol fermentation by Clostridium acetobutylicum was developed reflecting the biochemical pathway and culture behavior. Steady-state concentration of the process parameters in a cell-retention (CR) fermentation were predicted by computer process simulation. It was established that the product concentrations are independent of the dilution rate ((DF), whereas the accumulated biomass concentration increased linearly with respect to the dilution rate. The predicted effect of the glucose feed concentration (So) on steady-state concentrations of the process parameters showed that for values of So greater than 52.0 g/L the CR fermentor cannot attain a steady-state. On a etabli un modele mathematique pour la cinetique de fermentation en acetone-butanol par le Clostridium acetobutylicum qui rend compte de la voie reactionnelle biochimique et du comportement de la culture. On a predit les concentrations en regime stationnaire dans une fermentation a retention de cellules (CR) par une simulation du procede par ordinateur. On a etabli que les concentrations des produits sont independantes de la vitesse de dilution (DF), tandis que la concentration en biomasse accumulee augmente lineairement avec la vitesse de dilution. L'effet predit de la concentration de l'alimentation en glucose (So) sur les concentrations en regime stationnaire, montre que pour des valeurs de So superieures a 52,0 g/L, le fermenteur CR ne peut atteindre un regime stationnaire.

Aggregate behaviour of liquid fluidised beds

Abstract: New and long published experimental observations of the onset of aggregate (bubbling) behaviour in liquid fluidised beds are shown to be in agreement with the predictions of a recently published model of the fluidisation process. For a given liquid, the transition from particulate to aggregate fluidisation depends on both the density and size of the suspended particles: the lower the particle density the larger is the size necessary for a transition to occur: thus for fluidisation by ambient water, lead particles larger than 200 μm and soda glass particles larger than 2000 μm will exhibit aggregate behaviour; below a critical particle density no such transition is possible. On montre que des observations experimentales publiees recemment ou anterieurement relatives au comportement au demarrage de l'agregation (bullage) dans des lits fluidises par un liquide, sont en accord avec les predictions d'un modele du processus de fluidisation publie recemment. Pour un liquide donne, la transition de la fluidisation homogene a la fluidisation heterogene (bullage) depend a la fois de la densite et de la taille des particules suspendues: plus la densite des particules est basse plus la taille necessaire a la realisation de la transition est grande. Ainsi, pour la fluidisation a l'eau ambiante, des particules de plomb de failles superieures a 200 μm et des particules de verre sode de tallies superieures a 2000 μm montreront un comportement d'agregation. Une telle transition est impossible en-dessous d'une densite critique de particules.

A continuous process for recovery of sulfur from natural gas containing low concentrations of hydrogen sulfide

Abstract: A continuous catalytic process was developed to remove hydrogen sulfide from a natural gas stream using activated carbon as catalyst. The concentration range of hydrogen sulfide in the gas stream studied was 300–3000 ppmv (0.0126–0.126 moles/m3). Virtually 100 percent conversion of hydrogen sulfide was achieved by the combination of various parameters. The “field gas” employed in this study exhibited cracking of some heavier hydrocarbons and made the product sulfur slightly brown. These hydrocarbons should therefore be separated from the gas stream prior to the oxidation reaction. No carbon monoxide or carbon dioxide was produced during the oxidation of hydrogen sulfide. It is concluded that the process described herein has the potential for the removal of hydrogen sulfide as sulfur from a sour natural gas stream on a continuous basis and could therefore eliminate an environmental problem which now exists. On a developpe un procede catalytique continu utilisant du carbone active comme catalyseur pour la separation de l'hydrogene sulfure d'une alimentation de gaz naturel. La gamme de concentration de l'hydrogene sulfure dans le debit de gaz etudie est de 300–3000 ppmv (0,0126–0,126 mole/m3). Une conversion quasiment a 100% de l'hydrogene sulfure a ete realisee grǎce a la combinaison de differentes parametres. Dans le gas brut utilise dans cette etude on a observe le craquage de certains hydrocarbures lourds, ce qui a conduit a une coloration legerement brunǎtre du soufre produit. Ces hydrocarbures devraient par consequent ětre separes du courant de gaz prealablement a la reaction d'oxydation. Aucun monooxyde de carbone ou gaz carbonique n'a ete produit au cours de l'oxydation de l'hydrogene sulfure. On a conclu que le precede decrit ici presente de bonnes possibilites pour l'elimination de l'hydrogene sulfure et la production de soufre d'un courant de gaz naturel acide de maniere continue et qu'il pourrait par consequent eliminer un probleme environnemental actuel.

Effect of temperature on flow regimes and gas hold-up in a bubble column

Abstract: The effect of temperature on the gas hold-up and flow regimes for air—water and air—electrolyte solutions (NaCl and CuCl2) was studied in a bubble column with a sintered glass disc distributor. For the air—water system, the gas hold-up was found to decrease with increase in temperature. For the air—electrolyte solutions, increase in temperature resulted in increased gas hold-up at lower gas velocity, while at higher gas velocity the gas hold-up was found to decrease with temperature. The gas velocity ugT for transition from bubble flow to churn turbulent flow was found to decrease with increase in temperature as a result of increased coalescence. In the presence of electrolytes, ugT was found to be higher than that for water. On a etudie 1'influence de la temperature sur la retention des gaz et sur les regimes d'ecoulement pour des solutions air—eau et air–electrolyte (NaCl et CuCl2) dans une colonne a bulles munie d'un disque en verre fritte comme distributeur. La retention des gaz diminue dans le cas du systeme air—eau lorsque la temperature augmente. Pour les solutions air–electrolyte, une augmentation de la temperature provoque une augmentation de la retention des gaz a basse vitesse tandis qu'a plus haute vitesse de circulation des gaz, la retention diminue avec la temperature. On a trouve egalement que la vitesse des gaz ugT correspondant a la transition d'un ecoulement malaxe, diminue lorsque la temperature augmente en raison d'une coalescence accrue. ugT s'avere plus eleve en presence d'electrolyte qu'en presence d'eau.

Anisole production by alkylation of phenol over ZSM5

Abstract: The alkylation of phenol with methanol was performed in a microcatalytic reactor using the H- and Na-forms of a ZSM5 zeolite. Conditions were found in which the selectivity of the O-alkylation yielding anisole was as high as 80%. Some results are also reported for the alkylation of 2,4-dimethylphenol. On a effectue l'alkylation du phenol par le methanol dans un reacteur microcatalytique a lit fixe, en employant les formes H- et Na- d'une zeolithe ZSM5. On a etabli les conditions dans lesquelles la selectivite de l'alkylation sur le groupe OH conduisant a l'anisole est de l'ordre de 80%. Quelques resultats sont egalement presentes sur l'alkylation du 2,4-dimethylphenol.

Dilute acid depolymerization of cellulose in aqueous phase: Experimental evidence of the significant presence of soluble oligomeric intermediates

Abstract: The objective of this investigation is to show that rapid hydrolysis can be achieved by passage of aqueous cellulosic suspensions (2–10% solids) through capillaries followed by sudden decompression and post-treatment under dilutes acid conditions. Through detailed experimentation within the 200–240°C temperature range and at low sulfuric acid concentrations (0.2–1.0% w/w) it was found that liquefaction of the cellulose proceeds via extensive formation of soluble oligomeric intermediates. A simple kinetic model has been developed to explain the liquefaction-saccharification patterns of the cellulose. The sequence considered is: Cellulose Oligo-derivatives Glucose Decomposition products Quantitative values of the rate constants have been determined and a discussion on the selectivity of the overall reaction sequence is presented. L'objectif de ce travail est de montrer que l'hydrolyse de la cellulose peut ětre effectuee par passage rapide de suspensions aqueuses (ayant 2 a 10% de solides) a travers de capillaires suivi d'une decompression soudaine et post-traitement en presence d'acides dilues. Dans la plage de temperatures comprise entre 200 et 240°C et a des concentrations d'acide sulfurique de 0.2 a 1.0% (base ponderale) nous avons trouve que la liquefaction de la cellulose procede par voie de formation d'oligomeres solubles. Un simple modele cinetique developpe afin d'expliquer les profits de liquefaction-saccharification de la cellulose. La sequence reactionnelle consideree peut ětre representee par: Cellulose Oligo-derives Glucose Produits de decomposition Des valeurs quantitatives des constantes cinetiques ont ete determinees. Une discussion sur la selectivite de la reaction d'hydrolyse est presentee.

Kinetics and reaction mechanism of hydrogen sulfide oxidation over activated carbon in the temperature range of 125–200°c

Abstract: The kinetics and reaction mechanism of the oxidation of hydrogen sulfide over activated carbon were studied in the temperature range 125–200°C. The heats of adsorption of oxygen and H2S were found to be 73.8 and 16.0 kJ/mol, respectively, in the above temperature range. The sorption constants and the reaction constant have been expressed as a function of temperature. The role of water in the oxidation reaction has been clarified. No evidence was found to show that sulfur catalyzes the oxidation reaction.

Modelling and adaptive control of fed-batch penicillin fermentation

Abstract: This paper describes a study to investigate the application of state estimation and parameter adaptive control in fed-batch fermentation for penicillin production. A model of the penicillin fermentation process is outlined and shown to be capable of matching industrial data. The penicillin mould biomass is controlled to a reference trajectory by applying self-tuning control to an estimate of biomass, obtained from measurements of carbon dioxide production rate and fermenter volume and by using the fermentation model with an extended Kalman filter. The manipulated variable, sugar feed to the fermenter, is calculated by an adaptive algorithm. Simulation results compare the performance of self-tuning control with that obtained using digital Proportional plus Integral control.

Mixing characteristics and gas hold-up of a bubble column

Abstract: The hydrodynamic behavior of a bubble column has been studied for various Newtonian and non-Newtonian liquids (water, glycerol, carboxymethylcellulose and polyacrylamide solutions). The mixing time, the power consumption, the circulation time and the gas hold-up have been measured in a cylindrical column (diameter: 0.254 m, height: 0.9 m) for three air sparger plates with different numbers and distributions of 1 mm diameter orifices. It is shown that the mixing efficiency decreases as the viscosity or the shear-thinning and elastic properties of the liquid increase. The viscosity of the liquid has little influence on the gas hold-up which is, however, strongly affected by the sparger plate characteristics and increases as the liquid phase becomes more elastic. A model for predicting gas hold-up is proposed. Le comportement hydrodynamique d'une colonne a bulles utilisant differents liquides newtoniens et non-newtoniens (eau, glycerol, solutions de carboxymethylcellulose et de polyacrylamide) a ete etudie. Le temps dc melange, la puissance dissipee, le temps de circulation et le taux de vide ont ete determines dans une colonne cylindrique (diametre: 0.254 m, hauteur: 0.9 m). Trois differents types de distributeur d'air ont ete utilises. Tous possedent des orifices de I mm de diametre, mais le nombre et la repartition des orifices different de l'un a l'autre. On constate que l'efficacite de l'action de melange decroit lorsque la viscosite du liquide augmente ou lorsque ses proprietes rheofluidisantes et elastiques deviennent plus importantes. La viscosite du liquide a peu d'influence sur le taux de vide observe qui, par contre, varie beaucoup selon le type de plaque distributrice utilise et augmente avec le caractere elastique du liquide. Un modele pour la prediction du taux de vide est propose.

Measuring and modelling lateral solid mixing in a three‐dimensional batch gas—solid fluidized bed reactor

Abstract: A 0.27 m diameter fluidized bed reactor has been designed to allow experimental measurement of the axial and radial mixing behaviour of the solids. A unique method has been developed which permits the continuous determination of solid tracer concentration with time at different radial and axial positions within the fluidized bed. Solids mixing has been described by a model in which vertical mixing is instantaneous and lateral mixing occurs by dispersion. The lateral solids dispersion coefficients have been evaluated at various operating conditions from the experimental results of tracer concentration versus time. Based on the results, a modification of an existing correlation is proposed. On a concu un reacteur a lit fluidise de 0.27 m de diametre, qui permet de mesurer experimentalement le comportement des melanges axiaux et radiaux des solides. On a mis au point une methode unique qui permet la determination continue de la concentration d'un traceur solide en fonction du temps, a differentes positions radiales et axiales a l'interieur du lit fluidise. On decrit le melange des solides au moyen d'un modele, dans lequel le melange vertical est instantane et le melange lateral se fait par dispersion. Les coefficients de dispersion laterale des solides ont ete evalues dans differentes conditions operatoires, a partir des resultats experimentaux de la concentration du traceur en fonction du temps. On propose, a partir des resultats obtenus, une modification d'une correlation existante.

On the mechanism of hydrodeoxygenation of ortho substituted phenols

Abstract: Hydrodeoxygenation reactivities of four ortho-substituted phenols and of the unsubstituted phenol were compared at 350°C in the presence of a cobalt molybdate catalyst. The order of reactivities was established as: tert-butyl phenol >phenol >methyl phenol> ethyl phenol >dimethyl phenol.The order of resistance of phenolic rings to hydrogenation was observed as: dimethyl phenol methyl phenol >ethyl phenol >tert butyl phenol >phenol.

Prediction of drop size in rotating disc extractors

Abstract: A partir de donnees publiees sur les tailles des gouttes en absence de transfert de matiere, on presente deux equations pour la prediction du diametre des gouttes avec une intersection a un nombre de Reynolds de disque de 50000. La gamme totale de nombre de Reynolds de disque couverte va de 1200 a 282000. Les memes equations peuvent etre utilisees en presence de transfert de matiere si l'on modifie uniquement les preconstantes

Flow behaviour of oil‐in‐water emulsions

Abstract: The rheological behaviour of concentrated oil-in-water emulsions has been investigated using the Weissenberg Rheogoniometer. The oil concentration has been varied from 40 to 95 volume percent. The effects of shear rate and oil concentration on the viscosity have been determined. From the rheological data, the maximum attainable oil concentration in the emulsion has been estimated and is introduced as a parameter in the relationship between relative viscosity and oil concentration to account for certain variations in the emulsion characteristics. Empirical equations have been obtained which correlate zero shear rate viscosity and infinite shear viscosity as a function of reduced oil concentration. Comparison has been made between the emulsion viscosity and the solid-liquid suspension viscosity at high dispersed phase concentration. Estimated maximum attainable oil concentration is found to be in close agreement with the actual maximum concentration that could be achieved experimentally.