Showing papers in "Canadian Journal of Chemical Engineering in 1987"

Flow through Porous Media of a Shear-thinning Liquid with Yield Stress

Abstract: Darcy's law for the laminar flow of Newtonian fluids through porous media has been modified to a more general form which will describe the flow through porous media of fluids whose flow behavior can be characterized by the Herschel-Bulkley model. The model covers the flow of homogeneous fluids with a yield value and a power law flow behavior. Experiments in packed beds of sand were carried out with solutions of paraffin wax in two oils and with a crude oil from the Peace River area of Canada. The model fitted the data well. A sensitivity analysis of the fitting parameters showed that the model fit was very sensitive to errors in the flow behavior index, n, of the Herschel-Bulkley model. A comparison of the “n” values calculated from viscometer measurements and from flow measurements agreed well. A more general Reynolds number for flow through porous media, which includes a fluid yield value, was developed. The data were fitted to a Kozeny-Carman type equation using this Reynolds number. The constant in the Kozeny-Carman equation was determined for the two packed beds studied using Newtonian oils. The data could all be represented, within the experimental error, by the relationship f* = 150/Re*. Since the mean volume to surface diameter of the packing was determined by the measurement of its permeability to a Newtonian oil, assuming C' = 150, the new definition of the Reynolds number allows the direct use of the Kozeny-Carman equation with Herschel-Bulkley type fluids.

Use of sewage sludge for manufacturing adsorbents

Abstract: On demontre que la boue digeree peut etre reutilisee comme adsorbant pour la separation de vapeurs organiques (MEK, TOL et TCE) apres un traitement par pyrolyse. Les produits adsorbants fabriques ont ete caracterises par la valeur de leur surface de Brunauer, Emmett et Teller (BET), par leur activite vis-a-vis du tetrachlorure de carbone et par un test d'analyse elementaire. La determination de l'activite vis-a-vis du CCl 4 et celle de la surface BET sont toutes deux considerees comme des moyenz convenables pour estimer la capacite d'adsorption des vapeurs organiques sur des adsorbants de ce type. D'apres la surface specifique (activite du CCl 4 ou capacite d'adsorption), l'adsorbant regenere peut etre fabrique dans des conditions optimales en ajoutant ZnCl 2 a la boue traitee et en chauffant le melange

Experimental study of the inverse fluidized bed biofilm reactor

Abstract: A new apparatus, the inverse fluidized bed biofilm reactor, is described. Introduction of the so called inverse fluidized bed, in which low density particles covered by a biofilm are fluidized by downflow of the liquid, allows control of the biofilm thickness and provides a high oxygen concentration in the reacting liquid. Characteristics of the reactor were studied by carrying out two important biotechnological processes: aerobic wastewater treatment by a mixed bacterial culture, and ferrous iron oxidation by the bacteria Thiobacillus ferrooxidans. The bioreaction rates per unit volume of the reactor were up to 14 times higher than those in the equivalent airlift bioreactor. The structure of the liquid flow was determined by a tracer method.

Coal slurry fuel technology

Abstract: Volatile oil markets experienced in the seventies have promoted renewed interest in coal-based fuel technologies. Coal-slurry fuels have emerged as viable technical alternatives for oil and gas in utility and industrial boilers. Despite current low prices and the abundance of oil, concerns over its long-term availability and price, as well as strategic considerations, make coal-slurry technology attractive. Initially, coal-slurry fuels were based on coal-oil mixtures, now the emphasis is largely on coal-water fuels. This review assesses the status of the relevant technology. It covers the preparation of coal-slurry fuels, slurry properties, combustion characteristics, emissions, current applications and concludes with their future outlook.

Spatial control of sheet and film forming processes

Abstract: The general problem of controlling both machine and cross-directional properties on sheet and film forming processes is treated. A flexible class of linear dynamic-stochastic models capable of characterizing the process and disturbance dynamics in these systems is suggested. Procedures are presented for identifying these models from data collected from common scanning type sensors. Linear-Quadratic-Gaussian (LQG) control theory is used to design multivariable controllers capable of jointly controlling the machine and cross-directional property variations using both lumped and spatially distributed actuators. Le probleme du contrǒle simultane des proprietes dans le sens de la machine et dans le sens transversal dans les processus de preparation des feuilles et des films est etudie. On examine une categorie flexible de modeles dynamiques-stochastiques lineaires susceptibles de caracteriser la dynamique du processus et de la perturbation dans ces systemes. Des precedes pour l'identification de ces modeles sont presentes a partir des donnees obtenues par des manipulateurs courants a balayage. La theorie du contrǒle gaussien quadratique lineaire (LQG) est utilisee pour la conception de programmes multivariables pouvant contrǒler a la fois les variations des proprietes dans le sens de la machine et dans le sens transversal en utilisant un manipulateur global et d'autres repartis dans l'espace.

Gas-liquid mass transfer in "dead-end"autoclave reactors

Abstract: Gas-liquid volumetric mass transfer coefficients, (kLa), have been obtained for “dead-end” autoclave reactors operated in two different modes: (a) gas introduced into the gas phase, and (b) gas introduced through a dip-tube in the liquid. Three different methods of kLa determination have been compared. Effects of agitation speed, impeller diameter, gas to liquid volume ratio (Vg/VL), position of the impeller and reactor size on kLa have been investigated. The kLa data were found to be correlated as: kLa = 1.48 × 10−3 (N)2.18 (Vg/VL)1.88 (dI/dT)2.16 (h1/h2)1.16 The critical speed of surface breakage, at which transition from the surface convection to the surface entrainment regime occurs, was also determined for different impeller positions, impeller diameters and gas to liquid volume ratios. On a obtenu des coefficients volumiques de transfert de matiere gaz-liquide (kLa) pour des reacteurs de type autoclave sans circulation fonctionnant sous deux modes differents: (a) gaz introduit dans la phase gazeuse; (b) gaz introduit dans le liquide au moyen d'un tube immerge. On a compare trois methodes de determination de kLa. On a etudie l'effet de la vitesse d'agitation, du diametre de la turbine, du rapport volume de gaz sur volume de liquide (Vg/VL), de la position de la turbine ainsi que de la taille du reacteur sur le coefficient kLa. Les donnees ont ete correlees de la maniere suivante: kLa = 1,48 × 10-3(N)2.18 (Vg/VL)1.18 (dI/dT)2.16 (h1/h2)1.16 La vitesse critique de rupture de la surface correspondant a une transition entre un regime convectif de surface et un regime d'entraǐnement de surface, a egalement ete determines pour differentes positions et diametres de turbine et differents rapports volume de gaz sur volume de liquide.

Kinetics of growth and lactic acid production from whey permeate by Lactobacillus helveticus

Abstract: Batch fermentation kinetics of Lactobacillus helveticus were examined in detail. The nature of the culture medium had a significant effect on the product synthesis mechanism. In a glucose synthetic medium, lactic acid produced by the non-growth-associated mechanism was less than that by the growth-associated mechanism. In a lactose synthetic medium, the contribution of both mechanisms was approximately equal at the end of fermentation. In the whey-yeast extract permeate medium, the contribution by the non-growth-associated mechanism was superior to that of the growth-associated mechanism. Temperature and pH also influenced the relative contribution of the two mechanisms on the total production of lactic acid in whey-yeast extract permeate medium. Under optimal conditions for temperature and pH, the contribution of non-growth-associated product formation was the highest among all temperatures, and the lowest among all pH's. The ATP concentration-biomass concentration relationship in the batch fermentation process could be roughly approximated by a Luedeking-Piret-like equation. On a etudie en detail la cinetique de la fermentation discontinue du Lactobacillus helveticus. La nature du milieu de culture exerce un effet important sur le mecanisme de synthese du produit. Dans un milieu sythetique comportant du glucose, l'acide lactique produit par le mecanisme non associe a la croissance est moins important que celui produit par le mecanisme associe a la croissance. Dans un milieu synthetique comportant du lactose, la contribution des deux mecanismes est approximativement egale en fin de fermentation. Dans un milieu impregne en extrait de levure de petit lait, la contribution du mecanisme non associe a la croissance est plus grande que dans le mecanisme associe a la croissance. La temperature et le pH influencent aussi la contribution relative des deux mecanismes sur la production totale d'acide lactique en milieu impregne en extrait de levure de petit lait. Sous des conditions optimales de temperature et de pH, la contribution de la formation de produit non associee a la croissance est la plus importante de toutes celles obtenues aux diverses temperatures, et la moins importante de toutes celles obtenues aux divers pH. On a pu obtenir une approximation grossiere de la relation concentration de l'ATP-concentration biomasse dans le procede de fermentation discontinue par une equation de type Luedeking-Piret.

Rising velocity of a swarm of spherical bubbles in a power law non-Newtonian liquid

Abstract: Previous work on the rise of a swarm of bubbles in non-Newtonian media has been reviewed. Variational principles have been combined with the Happel free surface cell model to obtain upper and lower bounds on the swarm velocities of bubbles rising slowly through power law liquids. The predictions presented herein encompass wide ranges of gas holdup and shear-thinning behaviour. On a fait une etude de la litterature sur la montee d'un agglomerat de bulles en milieu non newtonien. Des principes varationnels ont ete combines a un modele de cellule de surface libre de Happel dans le but d'obtenir des limites superieures et inferieures sur la vitesse d'agglomeration de bulles montant lentement dans des liquides de type loi de puissance. De ce fait, les predictions presentees couvrent une large gamme de retention de gaz et de comportement rheofluidisant.

Viscosity of Compressed Cold Lake Bitumen

Abstract: Viscosity data over a temperature range of 37-115°C and a pressure range of 0-10 MPa gauge are presented for a Cold Lake bitumen sample. These data show that the compression of Cold Lake bitumen results in a significant increase in its viscosity. Results are compared with those from a similar study on an Athabasca bitumen sample. Also presented are two correlations for the effects of pressure and temperature on the viscosity of Cold Lake bitumen. On presente des donnees de viscosite pour une gamme de temperature de 37 a 115°C et une gamme de pressions de 0 a 10 MPa pour un echantillon de bitumes de Cold Lake. Ces donnees montrent que la compression des bitumes de Cold Lake entraine une augmentation importante de leur viscosite. Ces resultats sont compares a ceux d'une etude similaire effectuee sur un echantillon de bitumes d'Athabasca. On presente egalement deux correlations pour decrire l'effet de la pression et de la temperature sur la viscosite des bitumes de Cold Lake.

New analysis of non-newtonian turbulent flowndashyield-power-law fluids

Abstract: The writers' new analysis of non-Newtonian turbulent flow is extended to the yield-power-law model. As the value of the exponent of the yield-power law decreases from unity, the calculated friction factor begins by converging toward the Newtonian line at high velocity, then parallels it, and finally diverges downward. This prediction agrees with previously unexplained experimental results. L'analyse originale, que font les auteurs, de l'ecoulement turbulent non-newtonien est etendue au modele de la loi de puissance avec seuil. A mesure que la valeur de l'exposant de la loi de puissance avec seuil decroit a partir de la valeur un, le facteur de friction calcule commence par converger vers la droite newtonienne a haute vitesse, puis suit parallelement cette ligne pour finalement diverger vers le bas. Cette prediction est en accord avec des resultats experimentaux qui n'ont pu ětre expliques anterieurement.

Spouted bed hydrodynamics in a 0.91 m diameter vessel

Abstract: Hydrodynamic measurements were obtained in a flat-based half-cylindrical column of diameter 0.91 m and inlet orifice diameters of 76 to 114 mm. Beds of 3.5 to 6.7 mm diameter particles with static depths of 0.53 to 1.83 m were spouted with air. In agreement with measurements by earlier workers in smaller columns, it was found necessary to operate with inlet orifice diameters less than about 30 times the mean particle diameter in order to be able to achieve stable spouting. Correlations for minimum spouting velocity developed on small vessels generally gave poor predictions for the large diameter vessel employed in this work and failed to predict the observed dependence of Ums on the static bed height. Substantial dead regions where particles were stagnant were observed in the lower outer portion of the vessel. Other aspects of behaviour studied, including spout diameters and shapes, fountain heights, pressure profiles and gas velocities in the annulus, were qualitatively similar to those in smaller columns, although equations developed for the smaller vessels did not always provide accurate predictions. Des mesures hydrodynamiques ont ete obtenues dans une colonne semi-cylindrique a fond plat d'un diametre de 0,91 m et dont le diametre d'entree de I'orifice varie entre 76 et 114 mm. De l'air est injecte dans des lits de particules de 3,5 a 6,7 mm de diametre et d'une profondeur statique se situant entre 0,53 et 1,83 m. En accord avec des mesures effectuees par d'autres chercheurs sur des colonnes de dimensions inferieures, il apparaǐt necessaire d'operer avec des diametres d'orifice inferieurs a 30 fois le diametre moyen des particules si l'on veut pouvoir effectuer un lit a jet stable. Les correlations de la vitesse minimale etablies sur des colonnes de petites dimensions donnent generalement de mauvaises predictions sur la colonne de large diametre utilisee dans ce travail. En outre, ces correlations ne predisent pas la variation observee de Ums avec la hauteur statique du lit. On a observe par ailleurs d'importantes regions ou les particules sont stagnantes dans la partie exterieure basse de la colonne. Les autres aspects du comportement etudie, parmi lesquels le diametre et la forme des jaillissements, la hauteur de la fontaine, le profil de pression et la vitesse des gaz dans la partie annulaire, sont qualitativement similaires a ceux des colonnes plus petites, bien que les equations developpees pour les colonnes plus petites ne fournissent pas toujours de predictions precises.

Two classes of anionic surfactants and their significance in hot water processing of oil sands

Abstract: In hot water flotation of bitumen from Athabasca oil sands, two types of primary oil recovery response to sodium hydroxide addition are identified. Natural carboxylate surfactants can promote bitumen separation and flotation under certain process conditions, while a second, more polar, class of natural anionic surfactants can promote separation and flotation under different process conditions. As a result, some oil sands exhibit two recovery peaks as a function of sodium hydroxide addition. The phenomena are explained in terms of different sodium hydroxide additions required to reach critical surfactant concentrations specific to each surfactant class. The concept provides a means for interpreting a wide range of processibility phenomena. Au cours du procede de flottation a l'eau chaude des bitumes provenant des sables bitumineux d'Athabasca, on a identifie deux types de reponses lors de la recuperation primaire de petrole. Des surfactants naturels au carboxylate favorisent la separation et la flottation des bitumes sous certaines conditions de fonctionnement alors que d'autres surfactants naturels anioniques de nature plus polaire favorisent la separation et la flottation dans des conditions differentes. On a ainsi pu montrer que certains sables bitumineux ont deux pics de recuperation en fonction de l'addition d'hydroxyde de sodium. On a explique ce phenomene par les differentes quantites d'hydroxyde de sodium necessaires pour atteindre les concentrations de surfactants limites specifiques a chaque categorie. Ce concept permet d'interpreter de tres nombreux phenomenes intervenant lors du traitement.

Formation and growth mechanism of porous, amorphous, and fine particles prepared by chemical vapor deposition. Titania from titanium tetraisopropoxide

Abstract: The formation and growth mechanism of porous, amorphous, and fine particles were investigated. TiO2 particles were produced in a tubular flow reactor by a chemical vapor deposition technique using titanium tetraisopropoxide as a starting material at low temperatures (573-973 K) and atmospheric pressure. Prepared particles were of submicron size and had large surface area (as large as 270 × 103 m2/kg). According to the proposed mechanism, reactions begin on the reactor wall and then the primary particles form in the gas phase by chemical reactions. The primary particles collide, coalesce with each other and grow. However, significant experimental deviations from the Brownian collision and coalescence theory imply that other processes, such as the surface reactions on the particle, play an important role in the growth, in addition to coalescence. Intraparticle reactions decreased the surface area by filling the pores. On a etudie la formation et le mecanisme de croissance de particules fines, amorphes et poreuses. Des particules de TiO2 ont ete produites dans un reacteur tubulaire a ecoulement continu par une technique de depǒt de vapeur chimique en utilisant le tetra-isopropoxyde de titane comme materiau de depart, a basses temperatures (573-973 K) et a pression atmospherique. Les particules preparees ont une taille inferieure au micron et une grande surface specifique (jusqu'a 270 × 103 m2/kg). D'apres le mecanisme propose, les reactions commencent a la paroi du reacteur, puis les particules primaires se forment dans la phase gazeuse par reaction chimique. Les particules primaires se heurtent, s'agglomerent entre elles et croissent. Cependant, des ecarts experimentaux importants par rapport a la theorie de collision et d'agglomeration brownienne laissent supposer que d'autres phenomenes comme des reactions a la surface des particules jouent aussi un rǒle important dans le mecanisme de croissance. Des reactions a intraparticulaires diminuent la surface specifique en bouchant les pores.

Permanent jet formation in beds of particulate solids

Abstract: The simple criterion proposed by Chandnani and Epstein (1984, 1986) for stable spouting, dor/dp ≤ 25.4, is shown to give a good separation between gas-solid systems which form permanent jets and those that bubble, for a wide range of experimental data reported in the literature. The criterion is suggested as a necessary but not sufficient condition for permanent jet formation in fluidized, spout-fluid and spouted beds. On montre que le critere simple propose par Chandnani et Epstein (1984, 1986) pour un jaillissement stable, d ≤ 25.4, donne une bonne separation entre les systemes gaz—solides qui forment des jets permanents et ceux qui produisent des bulles, pour une grande categorie de donnees deja publiees. Ce critere est propose comme condition necessaire mais non suffisante pour la formation des jets permanents dans les lits fluidises, les lits a jaillissement et les lits mixtes.

Mass transfer between solid particles and liquid in a three phase fluidized bed

Abstract: Particle-liquid mass transfer in a co-current three-phase fluidized bed of glass beads, water and air was studied with two measurement techniques. Both techniques measured the weight loss of a few particles coated with benzoic acid in a bed of inert glass beads. The effects of liquid and gas velocities, gas distribution and surface active agents on particle-liquid mass transfer in a three-phase fluidized bed were thus determined. In the absence of surface active agents in the liquid, particle-liquid mass transfer rates in a three-phase fluidized bed were up to 30% higher than in the corresponding liquid fluidized bed. When surface active agents were added to the liquid, the particle-liquid mass transfer rate was increased by up to about 100% in the three-phase fluidized bed, relative to the liquid fluidized bed. The particle-liquid mass transfer coefficient was found to be inversely proportional to the liquid hold-up in the three-phase fluidized bed. On a etudie le transfert de matiere entre les particules et le liquide dans un lit fluidise triphasique, billes de verre, air et eau fonctionnant a cocourant, a l'aide de deux techniques de mesures. Ces deux techniques permettent de mesurer la perte de poids de quelques particules recouvertes d'acide benzoǐque dans un lit de billes de verre inertes. De cette maniere, on a pu determiner les effets des vitesses du liquide et du gaz, de la distribution du gaz et des agents tensioactifs sur le transfert de matiere entre les particules et le liquide dans un lit fluidise triphasique. En l'absence d'agents tensioactifs dans le liquide, le transfert de matiere entre les particules et le liquide dans un lit fluidise triphasique sont superieures de 30% a celles obtenues dans le lit fluidise liquide correspondant. Lorsqu'on ajoute des agents tensioactifs au liquide, le transfert de matiere entre les particules et le liquide augmente de 100% dans le lit fluidise triphasique, relativement au lit fluidise liquide. On a trouve que le coefficient du transfert de matiere entre les particules et le liquide est inversement proportionnel a la retention de liquide dans le lit fluidise triphasique.

Investigations of fluid dynamics in mechanically stirred aerated slurry reactors

Abstract: The fluid dynamics of stirred aerated slurry reactors with A-310® propeller, 4-blade 45° pitch turbine and 6-blade Rushton disc turbine were studied over a wide range of gas flow rates. With respect to power consumption, gas hold-up, and fluid dynamically limiting cases, viz., suspension and flooding, the Rushton disc turbine was found to be the best in stirred aerated slurry reactors. The influence of particle density, shape and mass fraction and of liquid properties on gassed critical stirrer speed, Njsg, and of gassed power input per unit volume, Pjsg, on particle suspension and gas dispersion, were investigated. Empircal correlations in combination with that of Zwietering were established for scale-up design in three-phase slurry reactors. On a etudie pour une large gamme de vitesses d'ecoulement de gaz, la dynamique de fluide de reacteurs agites a suspensions aerees munis d'une helice A-310®, d'une turoine a 4 pales a pas de 45° et d'une turbine a disques Rushton a 6 pales. En ce qui regarde la consommation d'energie, a retention de gaz et les cas limites de la dynamique de fluide a savoir, le regime en suspension et l'engorgement, la turbine a disques Rushton s'avere ětre la meilleure dans les reacteurs agites a suspensions aerees. On a etudie egalement l'influence de la densite, de la fraction massique et de la forme des particules et des proprietes du liquide sur la vitesse critique de l'agitateur, Njsg, ainsi que l'influence de la consommation d'energie par unite de volume Pjsg sur la suspension des particules et la dispersion des gaz. Des correlations empiriques combinees a celle de Zwietering ont ete etablies pour une mise a l'echelle dans des reacteurs a suspensions a trois phases.

A correlation for hydrogen solubility in alicyclic and aromatic solvents

Abstract: A correlation for hydrogen solubility in aromatic, alicyclic, and heterocyclic hydrocarbon solvents is presented. This correlation, employing corresponding state theory, provides reliable estimates for hydrogen solubility, in simple and multicomponent solvents, over the temperature interval 0.45 ≤ Tr ≤ 0.97, and for pressures from 0.1 to 30.0 MPa. The correlation was found to have an average absolute error of 5.9% for 14 simple solvents, and 6.8% for 11 multicomponent solvents which include coal liquids and bitumen. Solvent specific coefficients are not employed, and the correlation is well suited for predicting hydrogen solubility in multicomponent ill defned solvents, or in simple solvents where experimental data are unavailable.

Effect of water on the solubilities and mass transfer coefficients of gases in a heavy fraction of Fischer−Tropsch products

Abstract: The effects of water on the solubilities, C*, and volumetric mass transfer coefficients, kLa, for CO, H2, CH4 and CO2 in a heavy fraction of Fischer-Tropsch liquid were examined at elevated pressures and temperatures at different mixing power inputs. For these gases, higher solubilities were measured in the hydrocarbon mixture saturated with water than those obtained in the hydrocarbon free of water. The kLa values for the four gases were slightly affected by the presence of dissolved water in the hydrocarbon mixture; and they were strongly dependent on the power input per unit liquid volume. Two empirical correlations for kLa as a function of turbine speed and pressure are proposed. On a etudie l'influence de l'eau sur la solubilite C* et le coefficent de transfert de matiere volumique, kLa, pour le CO, l'H2, le CH4 et le CO2, dans une fraction lourde de liquide de Fischer-Tropsch, pour des temperatures et des pressions elevees, et differentes puissances de melange. Pour ces gaz, on a obtenu des solubilites plus grandes dans le cas du melange d'hydrocarbures satures en eau qu'avec les hydrocarbures anhydres. Les valeurs de kLa pour les quatre gaz sont legerement modifiees par la presence d'eau dissoute dans le melange d'hydrocarbures. En outre, ces valeurs sont fortement dependantes de la puissance depensee par unite de volume liquide. On propose deux correlations empiriques pour kLa en fonction de la vitesse de la turbine et de la pression.

Gas hold-up and mass transfer in a bubble column with viscoelastic fluids

Abstract: The influence of viscoelasticity on gas hold-up and the volumetric mass transfer coefficient in a bubble column is discussed and examined experimentally. It was found that the gas hold-up increased due to an increase in the number of entrapped very small bubbles formed because of the elasticity of the liquid. On the other hand, a decrease in volumetric mass transfer coefficient due to the fluid elasticity was observed. Qualitative effects of an antifoam agent and a draft tube on the performance of the bubble column with viscoelastic fluids were also examined. L'influence de la viscoelasticite sur la retention des gaz et sur le coefficient volumetrique de transfert de matiere dans une colonne a bulles est analysee et etudiee de maniere experimentale. On a trouve que la retention de gaz augmente en raison d'un accroissement du nombre de bulles tres petites emprisonnees, formees du fait de l'elasticite du liquide. D'autre part, on a observe une diminution du coefficient volumetrique de transfert de matiere due a l'elasticite du fluide. Des effets qualitatifs d'un agent antimousse et d'un tube de circulation sur l'efficacite de la colonne a bulles avec des fluids viscoelastiques, ont egalement ete etudies.

Degradation of aqueous DEA solutions in a heat transfer tube

Abstract: Experiments were performed on the degradation of aqueous diethanolamine (DEA) solutions passing through a coiled heat transfer tube (2.0032 mm ID, 3.175 mm OD, 4.8 m long) immersed in a constant temperature bath. The operating conditions were: DEA flow rate 0.011 to 0.0172 L/s, DEA concentration 20 to 40 wt%, DEA temperature 60 to 200/sup 0/C, CO/sub 2/ partial pressure 1.38 to 4.18 MPa. The degradation rate was found to increase with temperature, DEA concentration and CO/sub 2/ partial pressure; it decreased with solution flow rate. The degradation was accompanied by the formation of a fouling deposit. A simple mathematical model is presented for predicting DEA degradation.

Axial mixing and scaleup of reciprocating plate columns

Abstract: Axial mixing measurements in single phase (water) flow have been taken in open-type reciprocating plate columns of diameters 25.4 and 508 mm. In the case of the smaller column, two-phase axial mixing was measured, both in the dispersed phase (water dispersed in n-heptane) and the continuous phase (with n-heptane dispersed in water). Pulse injection of a tracer solution of ammonium chloride and methanol in water was used. Under single phase conditions, the axial dispersion coefficients were found to go through a minimum as the agitation level was increased from zero. The coefficients were nearly an order of magnitude higher in the 508 mm column than in the 25,4 mm column. In two phase flow in the 25,4 mm column, the continuous phase axial dispersion coefficients also went through a minimum as agitation was increased. The dispersed phase axial dispersion coefficients decreased monotonically as agitation was increased from zero. The results of this work and previous data are used in modelling the scale-up of reciprocating plate columns by means of Pratt's simplified technique. The existing empirical scale-up equation is consistent with an assumption that continuous phase mixing increased with column diameter but dispersed phase mixing remains unchanged. Des mesures de melange axial dans un ecoulement monophasique (eau) ont ete prises dans des colonnes a plateaux vibrants de type ouvert de diametres 25,4 et 508 mm. Dans le cas de la plus petite colonne, un melange axial biphasique a aussi ete mesure a la fois dans la phase dispersee (eau dispersee dans du n-heptane) et dans la phase continue (avec du n-heptane disperse dans de l'eau). On s'est servi d'une injection par impulsion d'une solution-traceur de chlorure d'ammonium et de methanol dans de l'eau. Dans le cas monophasique, les coefficients de dispersion axiale passent par un minimum pour un niveau d'agitation croissant a partir de zero. Les coefficients sont presque d'un ordre de grandeur superieures dans la colonne de 508 mm que dans celle de 25,4 mm. Dans le cas biphasique dans la colonne de 25,4 mm, les coefficients de dispersion axiale de la phase continue passent egalement par un minimum a mesure que l'agitation augmente. Les coefficients de dispersion axiale de la phase dispersee diminuent de maniere monotone pour une agitation croissante a partir de zero. Les resultats de cette etude sont utilises avec des donnees anterieures pour la moderation de la mise a l'echelle de colonnes a plateaux vibrants au moyen de la technique simplifiee de Pratt. L'equation de mise a l'echelle empirique existante correspond a l'hypothese que le niveau de melange augmente dans la phase continue lorsque le diametre de la colonne augmente, mais que le niveau de melange de la phase dispersee demeure inchange.

Liquid phase synthesis of methyl tert‐butyl ether catalyzed by ion exchange resin

Abstract: Synthesis of methyl tertiary butyl ether (MTBE) from methanol and isobutene was studied using macroporous cation exchange resin, Amberlyst 15 in the hydrogen form, as a catalyst in the temperature range of 313-328 K The reaction was carried out in a batch reactor at a pressure of one atmosphere in the liquid phase A high degree of agitation was maintained in order to eliminate film diffusion resistance The effect of catalyst loading, catalyst particle size and reaction temperature on reaction rate were studied The reaction rate increased with increase in catalyst concentration and reaction temperature Resin particle size had virtually no effect on the rate under the experimental conditions The reaction rate data were analysed using homogeneous kinetics and heterogeneous models based upon Langmuir-Hinshelwood rate expressions The apparent activation energies using homogeneous and heterogeneous models were determined and found as 790 kJ/mol and 767 kJ/mol respectively

High shear jet‐mixers as two‐phase reactors: An application to the oxidation of phenol in aqueous media

Abstract: Jet-mixers are known as devices capable of greatly enhancing the gas-liquid interfacial areas. Their application to chemical reactions is discussed in this paper. The oxidation of phenols in aqueous media is considered. Rates of oxidation fifty times higher than those previously observed can be achieved through a jet-mixer discharging a fine mist into the reactor side operating at plug flow regime. The presence of hydrogen peroxide accelerates the oxidation. Kinetic information is provided. Les atomiseurs sont bien connus comme etant capables d'augmenter considerablement l'aire interfaciale gaz-liquide. Leur application a des reactions chimiques est discutee dans cet article. Le cas concret de l'oxydation de solutions phenoliques est discute avec detail. Des taux d'oxydation du phenol tres eleves ont ete observes dans notre etude experimentale portant sur l'oxydation de solutions phenoliques qui, une fois atomisees, sont oxydees dans un reacteur tubulaire operant en regime d'ecoulement piston. Une augmentation du taux superieure a cinquante fois les taux rapportes dans la bibliographie est imputable au systeme de contact developpe au cours de cette etude. La presence du peroxyde d'hydrogene accelere davantage l'oxydation. Une etude cinetique est presentee dans la discussion de nos resultats.

On the determination of kinetic parameters for the regeneration of cracking catalyst

Abstract: In the study of the regeneration of cracking catalyst, two approaches may be taken when determining the kinetic rate constant for the coke combustion reaction. A global coke burning rate equation may be considered, based on the observed oxygen concentration and carbon dioxide to carbon monoxide molar product ratio. This reaction may also be represented by an intrinsic coke burning equation which is a function of the oxygen concentration and the carbon dioxide to carbon monoxide molar ratio at the reaction site, combined with a carbon monoxide postcombustion equation. It is proposed in this paper that the rate constant for intrinsic coke burning, kc, is essentially equal to the global coke burning rate constant, kc, and that its value is independent of the rate equation chosen for the carbon monoxide post-combustion reaction. Deux approches peuvent ětre envisagees pour determiner la constante de vitesse de la reaction de combustion du coke intervenant dans la regeneration des catalyseurs de craquage. On peut considerer une equation de vitesse de combustion globale du coke utilisant les valeurs observees de la concentration d'oxygene et du rapport molaire dioxyde de carbone/monooxyde de carbone. La reaction peut egalement ětre representee par une equation de la combustion intrinseque du coke, fonction de la concentration d'oxygene et du rapport molaire dioxyde de carbone/monooxyde de carbone, au niveau du site reactionnel, associee a une equation de post-combustion du monooxyde de carbone. On propose dans cette etude que la constante de vitesse pour la combustion intrinseque du coke kc est a peu pres egale a la constante de vitesse de combustion globale du coke kc, et que sa valeur est independante de l'equation de vitesse choisie pour decrire la reaction de post-combustion du monooxyde de carbone.

Experimental investigation of cocurrent two-phase flow in a vertical rectangular channel

Abstract: New time averaged data of two-phase flow in bubbly and slug regimes are presented. A modified dual spherical tipped optical fiber probe is used to measure local void fractions, gas velocity and bubble sizes. Hot film anemometry was used to measure the local mean liquid velocity axially. The void fraction, gas and liquid velocities values were presented as averages over the long and short dimensions respectively. Also core values of these variables are presented along the smaller dimension of 12.7 mm, near the plane of symmetry of the longer dimension, to show the most general trend of the different bubbly and slug flow runs. Bubble sizes obtained experimentally were compared with predictive models applied to circular geometries and were found to have a reasonable agreement. It was also interesting to find that local void fractions measured using hot film anemometers were comparable to those found by optical fiber probes. Frequencies of interfacial passage of bubbles and slugs are presented which show rather flat profiles across the channel. It is hoped that these data can be further used in predictive two-phase two-fluid models in the future. Lastly of interest is the fact that slip values near the boundaries were shown to be less than 1.0 for some cases in bubbly flow similar to those observed in circular geometries. On presente une serie de nouvelles donnees moyennes dans le temps, sur les regimes bouchons et bulleux d'un ecoulement biphasique. Une double-sonde modifiee a fibre optique a extremite spherique a ete utilisee pour mesurer le degre de vide local, la vitesse du gaz et la taille des bulles. On a utilise l'anemometrie a film chaud pour mesurer dans le sens de l'axe la vitesse moyenne locale du liquide. Les valeurs du degre de vide, de la vitesse du gaz et de celle du liquide sont presentees sous forme de moyennes dans le sens de la grande et de la petite dimension respectivement. On presente egalement les valeurs ponctuelles de ces variables le long de la plus petite dimension de 12.7 mm pres du plan de symetrie pour la plus grande dimension, afin de montrer la tendance generale des differents essais d'ecoulement en regimes bulleux et bouchons. Les tailles de bulles obtenues de maniere experimentale se comparent raisonnablement bien aux resultats de modeles predictifs appliques a des geometries circulaires. On a egalement remarque que les degres d vida locaux mesures par anemometrie a film chaud sont comparables a ceux obtenus a l'aide de word optiques. On montre que les frequences de passage interfacial des bulles et des bouchons ont des span le canal. On espere utiliser ces donnees ulterieurement dans des modeles predictifs biphasiques a span Finalement, on a trouve que les valeurs de glissement pres des frontieres sont inferieures a l'unite dans certains cas d'ecoulements bulleux identiques a ceux qu'on observe en geometrie circulaire.

Pipeline flow behaviour of heavy crude oil emulsions

Abstract: Pipeline transportation of heavy oils as oil-in-water emulsions has been proposed as an alternative to blending the crude oil with natural gas condensate or other diluent. An 18 m long, 0.02 m I.D. closed loop was constructed to investigate the behaviour of an emulsified Cold Lake crude oil under pipeline flow. Pressure drop was measured as a function of flow rate for freshly produced emulsions to establish correlations of friction factor versus Reynolds number. Stability was observed for long term pipeline flow. The time at which the emulsion breakdown occurred was found to be a function of oil concentration and shear rate. The breakdown of the emulsion was clearly indicated by a simultaneous change in the system variables of pressure drop, temperature and power required to turn the pump at constant speed.

On the particle terminal velocity in a gas‐liquid medium with liquid as the continuous phase

Abstract: A mechanistic model was developed to describe the terminal velocity of spherical particles in a gas-liquid medium with liquid as the continuous phase. The model was established based on the momentum balance of a single particle taking into consideration the drag and buoyancy forces due to the liquid phase and the bubble-wake and particle interaction. The bubble-wake and particle interaction coefficient was shown to be a function of the particle properties only. A comparison of the particle terminal velocity between the model prediction and experimental data obtained in this study was also made over a wide range of particle size and gas velocity. On a developpe un modele mecanistique pour decrire la vitesse de chute libre de particules spheriques de un milieu gaz-liquide, le liquide etant la phase continue. Le modele a ete etabli a partir du bilan de la q de mouvement d'une particule unique en prenant en consideration les forces de trainee et de flottabilite dues la phase liquide et l'interaction du sillage des bulles et des particules. On decrit le coefficient d'interaction entre le partet le sillage des bulles comme une fonction des proprietes des particules seulement.Une comparaison des predictions du modele et des resultats experimentaux obtenus dans cette etude pour la vitesse de chute libre des particules, a eg etablie pour une grande variete de tallies de particules et de vitesses du gaz.

Vapor-liquid equilibrium of the binary mixtures CnH2n + 1(OH) (n = 2,3,4) + Propyl Ethanoate and + Ethyl Propanoate

Abstract: The compositions of the vapor-liquid equilibria have been obtained in a small-capacity recirculating still for the binary systems comprised of ethanol, propan-l-ol and butan-l-ol with propyl ethanoate and ethyl propanoate at a constant pressure of 101.32 ± 0.07 kPa. The experimental data were correlated with suitable equations and the azeotropes and their minimum boiling temperatures found were: ethanol + propyl ethanoate (x = y = 0.923; T = 351.5 K), propan-l-ol + propyl ethanoate (x = y = 0.610; T = 361.7 K), ethanol + ethyl propanoate (x = y = 0.875; T = 350.9 K) and propan-l-ol + ethyl propanoate (x = y = 0.534; T = 366.2 K). Les compositions d'equilibre liquide-vapeur ont ete obtenues dans un ebulliometre a recirculation de petite capacite pour les systemes binaires comportant l'ethanol, le propane-l-ol et le butane-l-ol avec de l'ethanoate de propyle ou du propanoate d'ethyle a une pression constante de 101,32 ± 0,07 kPa. Les donnees experimentales ont ete correlees avec des equations appropriees; les azeotropes et leurs temperatures d'ebullition minimales sont pour le systeme ethanol + ethanoate de propyle (x = y = 0,923; T = 351,5 K), le systeme propane-l-ol + ethanoate de propyle (x = y = 0,610; T = 367,7 K), le systeme ethanol + propanoate d'ethyl (x = y = 0,875; T = 350,9 K) et le systeme propane-l-ol + propanoate d'ethyle (x = y = 0,534; T = 366,2 K).

The solubility of sulfur dioxide and hydrogen sulfide in associating solvents

Abstract: The solubilities of SO2 are reported in the solvents N, N-dimethyl acetamide (DMA), N, N-dimethyl formamide (DMF), ethyl acetate, acetonitrile, chlorobenzene, methanol, (1,2-ethanediol) ethylene glycol and acetone for atmospheric pressure and for temperatures ranging from 268 K to 333 K (-5°C to 60°C). Solubilities of H2S are also reported for the first five of the above-mentioned solvents and for hexane for similar conditions. These gases and solvents exhibit extreme molecular interactions which are reflected in unusual solubility behavior. This paper is a continuing attempt in providing data and analyses for improving the understanding of gas solubilities in complex gas-solvent systems. Solubilities expressed as hydrogen-bonding factors have been found useful in systematically relating gas solubilities in one associating or reacting solvent to another chemically similar solvent. Thus, with a limited amount of data for gas solubilities, it is often possible to predict solubilities even in highly associated or reacting gas-solvent solutions.

Kinetics of and catalyst decay accompanying the gas phase rearrangement of cyclohexanone‐oxime over a hy ultrastable zeolite

Abstract: The kinetics of the rearrangement of cyclohexanone-oxime has been studied in a fixed bed, glass tubular reactor at atmospheric pressure and temperatures of 240, 270, 300 and 335°C, using ultrastable HY zeolite catalyst. Several kinetic models, including the Langmuir-Hinshelwood type, have been derived and the best statistical fit has been obtained with a pseudo-first order kinetic equation. The rate constants and activation energies for the formation of the products caprolactam, cyclohexanone and 5-cyanopent-l-ene have been calculated. Based on the evolution of the selectivity with temperature, and the I.R. spectra of the poisoned catalyst, different decay models have been deduced and discussed. On a etudie la cinetique de rearrangement du cyclohexanone-oxime dans un reacteur tubulaire de verre a lit fixe sous la pression atmospherique et a des temperatures de 240, 270, 300 et 335°C, a l'aide d'un catalyseur de zeolithe HY ultrastable. Plusieurs modeles cinetiques, dont un modele de type Langmuir-Hinshelwood, ont ete etablies; le meilleur accord statistique a ete obtenu avec une equation cinetique du pseudo-premier ordre. On a egalement calcule les constantes de vitesse et les energies d'activation pour la formation des produits suivants: caprolactam, cyclohexanone et 5-cyanopent-l-ene. Les differents modeles possibles ont ete analyses d'apres l'evolution de la selectivite avec la temperature, et le spectre d'infrarouge du catalyseur empoisonne.