Showing papers in "Canadian Journal of Chemical Engineering in 1973"

Evaporation rates of liquid hydrocarbon spills on land and water

Abstract: The mass and heat transfer processes occurring during the evaporation of liquid hydrocarbon spills on land and water are described and equations developed to enable the liquid temperature and evaporation rate to be predicted. Experiments on the evaporation of cumene, water and gasoline are described and the evaporation mass transfer coefficient correlated with the wind-speed, liquid pool size and the vapour phase Schmidt Number. Good agreement is obtained between experimental and computed cumene temperature and evaporation rates. Comparison of the correlation with flat plate mass transfer correlations shows satisfactory agreement and suggests that turbulent transfer occurs, the rate being enhanced by the liquid surface roughness. The more complex problem of estimating evaporation rates of hydrocarbon mixtures is discussed briefly. On decrit les processus de transfert de masse et de chaleur qui ont cours durant levaporation d'hydrocarbures liquides renverses sur le sol ou leau, ainsi que les equations mises au point pour pouvoir predire la temperature et le taux devaporation des liquides. On expose les experiences faites sur levaporation du cumene, de leau et de la gazoline et etablit une correlation entre le coefficient de transfert de masse par evaporation et la vitesse du vent, les dimensions de la mare liquide et le nombre de Schmidt en phase gazeuse. On a obtenu une bonne concordance entre les taux devaporation et la temperature (experimentale et calculee) du cumene. On a aussi obtenu une concordance satisfaisante en comparant la dite correlation avec celles du transfert de masse sur une plaque unie, et il ya lieu de penser qu'il se produit un transfert turbulent dont la vitesse augmente avec lasperite de la surface liquide. On discute brievement le probleme plus complexe de levaluation des taux devaporation de melanges d'hydrocarbures.

Removal of fine particles from water by dispersed air flotation: effects of bubble size and particle size on collection efficiency

Abstract: A theoretical treatment is presented which attempts to quantify the benefits obtained by using smaller bubbles or larger particles in dispersed air flotation. The limited experimental data obtained so far suggest that the theory is sound, particularly in its prediction of the effect of bubble size.

Vertical pneumatic conveying: An experimental study with particles in the intermediate and turbulent flow regimes

Abstract: Vertical pneumatic conveying was studied in a 3-inch diameter riser 30 feet in length using solids ranging in particle Reynolds number from 100 to 3500. Particle to gas mass flow ratios varied from 0 to 8 and pipeline conditions extended from dilute flow down into the choking region. Average particle hold-up was determined by means of a series of quick-closing valves and particle slip velocity was often found to be greater than the calculated terminal velocity. The reasons for this are examined. Frictional pressure losses in the riser were also determined and compared with literature data. The phenomenon of choking is considered briefly. On a etudie le transport pneumatique et vertical, dans un tuyau de 30 pieds de longueur et 3 pouces de diametre, en utilisant des matieres solides dont les nombres de Reynolds des particules variaient entre 100 et 3500. Les rapports d'ecoulement entre les particules et le gaz variaient de 0 a 8 et les conditions dans le tuyau se sont etendues d'un ecoulement dilue a la region d'engorgeinent. On a determine la retention moyenne des particules, au moyen d'une serie de soupapes qui fermaient rapidement, et l'on a souvent trouve que la velocite de glissement etait plus elevee que la velocite terminate qu'on avait calculee; on en analyse les raisons. On a aussi determine les pertes de pression dues a la friction dans le tuyau et les a comparees avec les donnees publiees. On considere brievement le phenomene d'engorgement.

Simulated random packing of equal spheres

Abstract: PACS, a computer program to simulate very slow settling of rigid equal spheres into a randomly packed bed, is described. Simulated packings of 6,000, 10,000, and 15,000 spheres are anisotropic. Mean void fraction is 0.42 and mean number of nearest neighbours 6.0. There are numerous cases of four spheres arranged in a tetrahedron, but no larger ordered regions. These findings, plus local voidage, distribution of circles in a section, angular distribution, and radial distribution are compared to theoretical and experimental results.

An analysis of horizontal stratified two phase flow in pipes

Abstract: Using a mechanistic approach, equations are developed to describe the stratified cocurrent flow of gas-liquid mixtures in horizontal pipes. An iterative method is suggested for their solution. Experimental data were collected using air-oil mixtures in a one inch 1. D. by 101 ft. long acrylic pipe. Pressure drop and average in situ liquid volume fraction are presented as a function of the superficial gas velocity and are compared with predicted results from this study and other models reported in the literature. Visual observation of flow patterns and their transitions are indicated on the tentative flow pattern map of Govier and Aziz(1).

A general method of predicting the water activity of ternary aqueous solutions from binary data

Abstract: An isopiestic method has been developed to predict aw for ternary solutions from binary aw data. Another method, previously outlined by Robinson and Bower, has been extended to include non-electrolytes. Both methods have been used to predict aw's for 51 representative systems. The results show that the isopiestic method is as good as, or better than Robinson and Bower's in predicting aw for ternary aqueous electrolyte/ electrolyte, electrolyte/non-electrolyte and non-electrolyte/non-dectrolyte systems. Calculated aw values are in good agreement ( error on the average) with experiment. The methods are applicable to relatively concentrated solutions up to 12 m. Une methode isopiestique de prediction de aw pour des systemes ternaires est proposee. Cette methode utilise les aw de systemes binaires. Une autre methode, precedemment esqnissee par Robinson et Bower, a aussi ete developpee pour des solutions de non-electrolytes. Les deux methodes ont ete employees pour calculer les aw de 51 systemes representatifs. Une comparaison des resultats obtenus demontre que la methode isopiestique est aussi bonne, sinon meilleure, que celle de Robinson et Bower lorsqu'on vent predire des aw pour des systemes ternaires aqueux comprenant electrolyte/electrolyte, electrolyte/non-electrolyte et non-electrolyte/non-electrolyte. Les valeurs calculees de aw sont en tres bon accord (< 0.5% d'erreur, en moyenne) avec les valeurs obscrvees. Les methodes de calcul sont applicables jusqu'aux concentrations 12 fois molales.

Vertical pneumatic conveying: A theoretical study of uniform and annular particle flow models

Abstract: Two models for vertical pneumatic conveying, a uniform flow model at high gas velocities and an annular flow model near the particle terminal velocity, have been examined theoretically. The uniform flow model leads to the following relationship between gas and particle velocity and line porosity: No simple analytical solution was found for the annular flow model but a numerical solution was possible. Both models indicate that slip velocity may exceed the particle terminal velocity under certain conditions. The theoretical predictions agree reasonably well with experimental observations.

Exact solutions for a class of heat and mass transfer problems

Abstract: A number of heat and mass transfer problems of chemical engineering interest involve the convective diffusion equation of the form where θ = θ(X1, X2). Exact solutions for such problems are developed in terms of well-known functions which have been thoroughly studied in recent years. Several problems which have appeared in the literature, solved by completely numerical methods, are re-examined and new problems are discussed and solved. The results of the present analysis are compared with those obtained by other methods where possible. The problem of axial diffusion of heat or mass is solved in terms of known functions. The present formulation is shown to be particularly useful in the analysis of conjugated boundary value problems, i. e. for problems involving heat or mass transfer across an interface where the interfacial boundary condition is not known a priori but is related to the temperature or concentration fields in the adjacent phases.

The multicomponent solubility of hydrocarbons in water

Abstract: The aqueous solubility of six binary hydrocarbon systems consisting of benzene and cyclohexane with each of 2-methyl-pentane, n-hexane, and l-hexene, have been measured at 25d'C The solubility of each hydrocarbon component is greater by from 6 to 35% than the value expected by prediction on the basis of the solubility of the hydrocarbon component being proportional to its mole fraction in the hydrocarbon phase This positive deviation is partly attributable to the activity coefficient of the hydrocarbon in the hydrocarbon phase being slightly greater than unity There is, however, additional solubility enhancement of from 1 to 25% with an average of 107% apparently due to the reduction of the hydrocarbon activity coefficients in the aqueous phase by the presence of the other hydrocarbon The implications of these effects in calculating the solubility of complex hydrocarbon mixtures in water is considered On a mesure a 25°C la solubilite aqueuse de six systemes binaires d'hydrocarbures formes de melanges du benzene et du cyclohexane avec le 2-methylpentane, l'hexane normal et l'hexene normal pris separement La solubilite de chaque composant (hydrocarbure) est plus elevee de 6 a 35% que la valeur prevue en se basant sur le fait que la solubilite du composant est proportionnelle a sa fraction moleculaire dans la phase hydrocarbure Cet ecart positif est partiellement attribuable an fait que le coefficient d'activite de l'hydrocarbure dans la phase hydrocarbure excede a peine l'unite Il y a, cependant, un accroissement de solubilite de 1 a 25% (107% en moyenne) a cause apparemment de la diminution des coefficients d'activite des hydrocarbures dans la phase aqueuse due a la presence de l'autre hydrocarbure On considere les implications des dits effets dans le calcul de la solubilite dans l'eau de melanges complexes d'hydrocarbures

The velocity distribution within a hydrocyclone operating without an air core

Abstract: The three dimensional flow patterns in a 3-in. diameter hydrocyclone operating without an air cone were studied using tracer particles and cine photography. Analysis of films at 55 locations inside the hydrocyclone yielded data for 18 velocity profiles at six vertical positions. These data were checked for consistency and compared with the results of earlier work in hydrocyclones operating with air cores. The tangential velocity profiles were found to be similar to those produced with an air core although, n. in VAIn = const, is about 0.2 to 0.4 instead of 0.7 to 0.8 for air core operation. In this work the radial velocity component was relatively independent of radius.

Symposium on application of pulse techniques to kinetic measurements: Influence of cycling on the rate of oxidation of SO2 over a vanadia catalyst

Abstract: Feed composition cycling of the catalytic oxidation of SO2 to SO3 in an isothermal, differential reactor was studied using an industrial vanadia catalyst. Reaction was carried out at 405°C using square-wave cycles of SO2, O2 and N2 at pressures close to atmospheric and at constant total molar flow through the reactor. Significant increases were found in the rate of oxidation of SO2 over steady-state values, depending upon the choice of both amplitude and period. Some preliminary interpretation of these results is provided. On a fait une etude du cyclage de la composition qui entre dans un reacteur differentiel et isothermique ou se passe l'oxydation de SO2 a SO3 en utilisant un catalyseur industriel a base d'oxyde de vanadium. La reaction s'est faite a 405°C en utilisant des cycles a ondes carrees de SO2, d'O2, et de N2 et des pressions a-peu-pres atmospheriques et des courants constants a travers du reacteur. On presente quelques interpretations preliminaires de ces resultats.

Rheological behavior of shear degradable oils: Kinetic and equilibrium properties

Abstract: An investigation of the non-Newtonian, time dependent, flow properties of various crude oils at or below their pour points is reported. Experimental observations of material response under various shear and stress conditions provide a basis for the development of a kinetic and rheological model which quantitatively describes the shear degradation and equilibrium behavior exhibited by these materials. Preliminary data on the effects of thermal history and aging are also reported, showing the relative importance of these factors to the rheological properties. On presente une etude des proprietes d'ecoulement (nonnewtonien et dependant du temps) de diverses huiles brutes, a leurs points de fluidite ou au-dessous de ceux-ci. Les observations experimentales de la reponse des huiles dans diverses conditions de cisaillement et de tension ont fourni les elements de base pour la mise au point d'un modele cinetique et rheologique qui decit quantitativement la degradation par cisaillement et le comportement d'equilibre manifeste par les huiles. On rapporte aussi les resultars preliminaires qu'on a obtenus sur les effets de la chaleur et du vieillissement; ils montrent l'importance relative de ces facteurs sur les proprietes rheologiques.

Oxidation of propionic acid solutions

Abstract: Wet air oxidation is a process in which organic materials in the aqueous phase are oxidized by air at temperatures between 300°F and 600°F and pressures of 1000-1800 psia. To improve our understanding of the process, its kinetics were studied using a propionic acid solution to simplify both analysis and rate measurements. The aim of the research was to define the regime where the reaction rate is kinetically controlled, to develop a model for the reaction rate and to interpret the model in terms of mechanism. Oxidation appears to proceed homogeneously in the aqueous phase and is probably kinetically controlled between 450° and 550°F. The oxidation appears to take place via two principal routes. Approximately half the propionic acid is oxidized completely to carbon dioxide while the oxidation of the remainder apparently proceeds via acetaldehyde as an intermediate to acetic acid. Acetic acid oxidizes only at a very low rate. A power law rate expression was developed which adequately described the oxidation of propionic acid solutions.

Solids entrainment in a large gas fluidized bed

Abstract: Entrainment from a gas fluidized bed of cracking catalyst in a 2-ft diameter column equipped with continuous solids recycle has been studied. Radial profiles of entrainment rate and mean particle size were relatively flat. The entrainment rate decreased rapidly with increasing height above the bed and with decreasing fluidizing velocity. The existence of a transport disengaging height above which the entrainment rate and mean particle size become essentially constant was confirmed experimentally. This may be taken as the height above the bed surface at which the inverse Froude number becomes equal to 1000. On a etudie lentrainement provenant dun lit de catalyseur de craquage fluidise an gaz, dans une colonne de 2 pieds de diametre et pourvne dun dispositif pour recycler dcs solides dune maniere continue. Les profils radiaux du taux dentrainement et des dimensions moyennes des particules se sont averes relativement plats. Le taux dentrainement a diminue rapidement en raison inverse de la hauteur et directement avec la velocite decroissante de fluidisation. On a confirme experimentalement lexistence dune hauteur de degagement au-dessus. de laquelle le taux dentrainement et les dimensions moyennes des particules devenaient essentiellement constants; on peut la considerer comme la hauteur au-dessus de la surface dn lit a laquelle le nombre inverse de Froude devient egal a 1000.

Optimal discrete stochastic control theory for process application

Abstract: The design of discrete feedback controllers which minimize some linear function of the variances of the output deviations from target subject to possible constraints on the variances of the inputs, for linear systems subject to stochastic disturbances, is treated from two points of view: (1) using transfer function models to characterizing the process dynamics and autoregres-sive-moving-average models to characterize the stochastic disturbances, and then solving the optimal control problem using an approach due to Box and Jenkins and a discrete version of the Wiener-Newton theory; and (2) using state variable models to characterize both the dynamic and stochastic parts of the system, and then solving the optimal control problem using the results of dynamic programming and Kalman filtering. Practical considerations such as model forms, their identification and estimation, and the development of variance relationships that are necessary for the application of these two approaches in the process industries are discussed. The relationship between and a comparison of these two approaches is made. On discute de deux manieres differentes, dans le cas des systemes lineaires qui sont sujets a des perturbations stochastiques, la conception de controleurs de reactions discontinues, lesquels minimisent une fonction lineaire des variations des ecarts du rendement de lobjectif recherche a des contraintes possibles sur les variations de lalimentation fournie. On a procede comme suit: (1) on a employe des modeles de la fonction de transfert pour caracteriser la dynamique du processus et des modeles ordinaires auto-regressifs pour depeindre les perturbations stochastiques, et l'on a resolu le probleme de controle optimal en ayant recours a un mode dapproche de Box et Jenkins et a une version discontinue de la theorie de Wiener et Newton; (2) on a employe des modeles variables de regimes pour caracteriser les parties dynamiques et stochastiques du systeme et lon a resolu le probleme de controle optimal en utilisant les resultats de la programmation dynamique et de la filtration de Kalman. O discute certains points pratiques telles que les formes, lidentification et levaluation des modeles, ainsi que la mise au point de relations entre les variations qui sont necessaires pour appliquer les deux modes dapproche precites aux industries de traitement. On compare les dits modes dapproche en soulignant leur connexite.

Flow maldistribution in two dimensional packed beds: Part II: The behavior of non‐isothermal systems

Abstract: A formulation is developed and computed results are presented for flow maldistribution in two-dimensional packed beds involving non-isothermal systems. Results are shown for both, systems in cylindrical and rectangular coordinates and the examples discussed include the pasage of a two-dimensional temperature wave through a packed bed of non-uniform porosity and the examination of the flow maldistribution that is caused by the radial non-uniformity of temperature. The results indicate that radial temperature profiles in packed beds may lead to flow maldistribution even under conditions where the porosity is uniform and it is suggested that this phenomenon may play an important role in the formation of hot spots. On a mis au point une formule et presente les resultats calcules, dans le cas d'une mauvaise distribution de l'econlement dans des lits garnis de deux dimensions ou entrent en jeu des systemes non isothermes. On indique les resultats, pour les deux systemes, dans des coordonnees cylindriques et rectangulaires et discute des exemples tels que le passage d'une onde de temperature a deux dimensions dans un lit garni de porosite non nniforme, et l'etude de la mauvaise distribution de l'ecoulement qui est due a l'absence d'uniformite radiale de la temperature. Les resultats indiquent que les profils de temperature radiale dans les lits garnis peuvent conduire a une mauvaise distribution de l'ecoulement, meme dans des conditions ou la porosite est uniforme, et il y a lieu de croire que ce phenomene peut joner un role important dans la formation de points chauds.

Drag force on isolated axisymmetric particles in stokes flow

Abstract: An approximate solution to the equation of motion governing Stokes flow past a number of isolated closed bodies of revolution is obtained by the least squares fitting of a truncated series expression for the stream function to known boundary conditions. The solution yields a reasonably accurate (±5%) estimate for the Stokes resistance on body shapes, such as cylinders and cones, for which analytic solutions are exceedingly difficult. The computed drag values were applied in determining the limitations of the various empirical expressions used to predict the drag resistance of these geometrically simple bodies. A new empirical correlation is presented. On obtient une solution approximative a l'equarion de mouvement qui regit l'ecoulement de Stokes, apres avoir soumis des solides fermes et isoles a un certain nombre de revolutions, en adaptant, a des conditions-limites connues, les moindres carres d'une expression de serie tronquee pour la fonction du courant. La solution fournit une estimation raisonnablement exacte (±5%) de la resistance de Stokes sur les formes des solides (tels que cylindres et cones) pour lesquels il est tres difficile d'obtenir des solutions analytiques. On a applique les valeurs calculees du tirage a la determination des limitations de diverses expressions empiriques qui servent a predirc la resistance a la trainec des dits corps geometriques simples. On presente une nouvelle correlation empirique.

A general algorithm for multistage multicomponent separation calculations

Abstract: This paper presents a new general calculational method for equilibrium stage processes. The method employs a multivariate Newton procedure to solve all equations simultaneously for corrections to temperatures, flow rates and compositions. The linearized model equations are selected so that only 2N (1 + NCP) partial derivatives need to be evaluated per iteration. Experience to date indicates that the method is reliable for both distillation and absorption problems and requires less computing time than current procedures. The rigorous solution of a reboiled absorber problem for 16 stages and 15 components required 5 iterations and 14.4 seconds on an IBM 360/67 computer even when the Chao-Seader correlation was employed for the direct calculation of composition dependent equilibrium and enthalpy data. On presente une nouvelle methode generale de calcul dans le cas des processus etages dequilibre; on y emploie le procede de Newton a variables multiples pour resoudre en meme temps toutes les equations relatives aux corrections des temperatures, des vitesses decoulement et des compositions. On choisit les equations linearisees du modele de maniere qu'il ne faille evaluer par iteration que les derives particls 2N (1 + NCP). Lexperience a indique jusqu'ici que la methode est fiable dans le cas des problemes de distillation et dabsorption et qu'elle exige moins de temps de calcul que les procedes actuels. La solution rigoureuse du probleme dun absorbeurbouilleur, dans le cas de 16 etages et 15 composants, a exige 5 iterations et 14.4 secondes sur un ordinateur IBM 360/67, meme en utilisant la correlation de Chao et Seader pour le calcul direct des resultats relatifs a lequilibre dependant de la composition et a lenthalpie.

The removal of copper, cadmium, and lead ions from dilute aqueous solutions using foam fractionation

Abstract: The removal of copper, lead and cadmium ions from aqueous solution by foam fractionation using sodium dodecylbenzene sulphonate (NaDBS) has been experimentally studied and theoretically predicted for solutions with a pH less than 4. A mathematical model of the system consisting of the equilibrium relations of chemical reactions occurring in the system was solved for the equilibrium concentration of all ions in the solution. Based on this equilibrium concentration and the effective radius of the hydrated ion, a modified theory of the Gouy-Chapman diffuse double layer(9) was used to predict the distribution factor of the metal ions. The work was extended to systems containing two metal ions for the determination of the separability of the ions with respect to each other. It was found that the distribution factor for solutions containing one metal ion could be predicted theoretically for a bulk solution pH less than four. Deviation of results above this pH was attributed to the limitations of the bulk solution reaction model because it did not include reactions for the formation of poly hydroxyl and poly nuclear hydroxyl complexes. Good agreement was also obtained between experiment and theory in the separability study. The results indicate that the order of removal of the ions from solution is Pb++ > Cd++ > Cu++. This sequence is the reverse order of the effective radii of the hydrated ions. The results support the fact that the mechanism for removal of the ions from solution is that of electrical attraction and that selectivity depends upon the charge and size of the hydrated ion. On a etudie experimentalement la separation des ions de cuivre, plomb et cadmium d'une solution aqueuse par fractionnement de type ecume, en employant le dodecylbenzenesulphonate de sodium (NaDBS); on l'a aussi predite theoriquement pour des solutions dont le pH est inferieur a 4. On a resolu, pour la concentration d'equilibre de tous les ions en solution, un modele mathematique du systeme comprenant les relations d'equilibre des reactions chimiques qui s'y produisent. En se basant sur la dite concentration d'equilibre et sur le rayon effectif de l'ion hydrate, on a employe une theorie modifiee de la couche double et diffuse de Gouy et Chapman(9) pour predire le facteur de distribution des ions metalliques. On a fait une extension du travail aux systemes qui contiennent deux ions metalliques pour determiner la separabilite des ions les uns des autres. On a trouve qu'on pouvait predire theoriquement, pour des solutions dont le pH etait moindre que 4, le facteur de distribution des solutions contenant un ion metallique. On a attribue l'ecart des resultats, dans le cas d'un pH superieur a 4, aux limitations du modele des reactions en solution, parce qu'il n'embrassait pas les reactions pour la formation de polyhydroxyle et de complexes nucleaires de polyhydroxyle. On a obtenu une bonne concordance entre les resultats experimentaux et les theoriques dans l'etude de separabilite. Les resultats indiquent que l'ordre de separation des ions de la solution est: Pb++ > Cd++ > Cu++, La dite sequence correspond a l'ordre inverse des rayons effectifs des ions hydrates. Les resultats appuient le fait que le mecanisme de separation des ions d'une solution est celui de l'attraction electrique et que la selectivite depend de la charge et des dimensions de l'ion hydrate.

A cationic surfactant as a soluble ion exchanger in the continuous foam fractionation of nitrate; iodide, and bromide

Abstract: An experimental investigation is presented of the continuous foam fractionation of NO3− versus Br− and of T− versus Br− with a quaternary ammonium surfactant at concentrations of the order 1.8 × 10−4M. An equation is derived to enable the computation of anion selectivity coefficients from foam fractionation data. The key assumptions of the derivation are verified experimentally. The selectivity coefficient for NO3 versus Br− is 1.56 ± 0.28 and for I− versus Br− is 5.85 ± 1.81, established from 40 continuous-flow experiments. Precipitation of EHDA-I is indicated at the highest ratios of the bulk solution concentrations of I− and Br−. significantly, both selectivity coefficients are independent of the fraction of the exchanger occupied by the preferred ion, indicating an exchanger activity coefficient ratio of unity, and are independent of ionic strength. The counterion present markedly influences the surfactant distribution coefficient. On presente une etude expeiimentale de la separation, par fractionnement continu avec production de mousse, de NO2− de Br− et de I− de Br−; on a utilise a cette fin un agent tensio-actif quaternaire d'ammonium a des concentrations de l'ordre de 1.8 × 10−4M. On a mis au point une equation qui permet de calculer les coefficients de selectivite des anions a partir des resultats de la separation par fractionnement avec production de mousse. On a verifie experimentalement les principales suppositions faites lors de la mise au point de l'equation. On a etabli, au moyen de 40 experiences en courant continu, que le coefficient de selectivite de NO3− par rapport a Br− etait 1.56 ± 0.28 et celui de I− par rapport a Br− etait 5.85 ± 1.81. On indique la precipitation de EHDA-I aux rapports les plus eleves de l'ensemble des concentrations en solution de I− et Br−. Fait significatif, les deux coefficients de selectivite sont independants de la fraction de l'echangeur occupee par l'ion prefere (ce qui indique un rapport de 1 pour le coefficient d'activite de l'echangeur) et de la force ionique. l'ion contraire present exerce un effet notable sur le coefficient de distribution de l'agent tensio-actif.

On the efficiency of a venturi scrubber

Abstract: The performance of a venturi scrubber with a 1-in. by 3-in. throat was determined using monodispersed uranine-methylene blue aerosols in the size range 0.8 to 3.0μm at throat velocities ranging from 109.6 ft/sec to 245 ft/sec. Separate measurements on the water separator showed that substantial aerosol removal took place in this unit, and the efficiency of the scrubber itself was calculated from these measurements plus overall efficiency measurements on the combination scrubber and separator. These results were compared with values obtained from a theoretical model and agreement was generally satisfactory, although the theoretical efficiencies were lower than the experimental efficiencies at the highest air velocities, and viceversa. This discrepancy may be due to a number of factors which are discussed. On a determine le comportement dun epurateur-venturi, muni dune gorge de 1′ par 3′, en employant des aerosols monodisperses duranine et de bleu de methylene, dont les dimensions des particules variaient entre 0.8 et 3.μm pour des vitesses de la gorge de 109.6 a 245 pieds a la seconde. Des mesures faites separement sur le separateur deau ont indique qu'il s'y produisait une elimination substantielle des aerosols; aussi a-t-on calcule le rendement de lepurateur a partir de ces mesures et des mesures totales faites a la fois sur lepurateur et le separateur. On a compare les resultats avec les valeurs obtenues au moyen dun modele theorique; la concordance s'est averee generalement satisfaisante, quoique les rendements theoriques aient ete inferieurs aux experimentaux pour les vitesses de lair les plus elevees, et vice versa. La variation constatee peut dependre dun certain nombre de facteurs qu'on decrit.

The screening and selection of solvents for the extraction of phenol from water

Abstract: The thermodynamic basis foi the selection of solvents for the removal of phenol by liquid-liquid extraction from waste water is discussed. Data are presented showing the often marked dependence of distribution coefficient on solute concentration at levels of 5 to 1000 mg/l. Experimental and literature data for the infinite dilution activity coefficient of phenol in 26 solvents at 25°C are correlated using a Regular Solution approach by assigning a value to an interaction energy term dependent on the chemical nature of the solvent. The accuracy is not sufficient for design purposes but the method can be used for screening. Toxicity and biodegradability of the preferred solvents are discussed. On discute l'utilisation de la thermodynamique pour le choix de solvants dans l'enlevement du phenol de l'eau usagee au moyen d'extraction d'un liquide par un liquide. On presente des donnees qui indiquent la dependance souvent marquee qu'a le coefficient de distribution de la concentration du solute lorsqu'elle varie entre 5 et 1000 milligrammes par litre. On etablit une correlation entre les resultats experimentaux et les donnees publiees dans le cas du coefficient de phenol pour une activite de diluition infinie dans 26 solvants a 25°C; on emploie a cette fin le mode d'approche d'une solution ordinaire en assignant une valeur a un terme d'energie d'interaction qui depend de la nature chimique du solvant. L'exactitude de cette methode est insuffisante pour fin de conception, mais on peut l'utiliser pour une selection. On discute la toxicite et la degradation biologique des solvants preferes.

Continuous ion exchange in fluidized beds

Abstract: A mathematical model has been developed for prediction of the performance of a continuous ion-exchange column, comprising a series of fluidized beds of resin, operated with periodic flows of both phases. Simple small-scale tests provide the data required in calculations. Experimental work was carried out on uranium extraction from unfiltered ore leach pulps and clarified liquors. On a mis au point un modele mathematique pour prevoir le rendement d'une colonne d'echange continu d'ions, formee d'une serie de lits fluidises de resine et fonctionnant sous l'effet des ecoulements periodiques des deux phases. On a obtenu, au moyen d'essais simples et faits sur une petite echelle, les donnees requises pour les calculs. On a fait un travail eexperimental sur l'extraction de l'uranium des boues de lixiviation d'un minerai non-filtrees ainsi que des liqueurs clarifiees.

Solubilities of the highly soluble gases, propane and butane, in normal paraffin and polar solvents

Abstract: The solubility of highly soluble gases in both polar and non-polar solvents has been found to approach a mole fraction of unity as the solution temperature is reduced toward the normal boiling point of the dissolved gas. Solubilities of all gases in the polar solvents chlorobenzene, normal butanol and acetone, tend toward a common reference solubility for each solvent as the temperature is increased toward the solvent critical temperature. Solubilities of propane as measured in this work are reported at 0°C, 25°C and 50°C in chlorobenzene, butanol and acetone and at 25°C in hexane and hexadecane, along with solubilities of butane at 5°C, 25°C and 50°C in hexane, heptane, octane, dodecane, hexadecane and butanol. These data, along with those from literature sources, have been utilized in formulating the above generalizations.

Non-Newtonian thin films: Theory and experiment

Abstract: The flow of thin films of Newtonian and non-Newtonian, Power law fluids down a vertical plate was studied in the laminar and wavy flow regimes. A theoretical development based on the existence of a steady, periodic solution to the equations describing film flow was used to predict the flow characteristics of the film. Double logarithmic plots of film thickness versus Reynolds number (ReP. L.) were linear, as predicted, up to a ReP. L. = 100. The ratio of surface to average velocity was found to be approximately independent of the Reynolds number at values predicted by a laminar velocity profile. The wavelength of stable waves was found to be independent of the Reynolds number for a given fluid. On a etudie, dans les regimes decoulements laminaires et ondules, lecoulement vers le bas dune plaque verticale de pellicules minces de fluides newtoniens ou non et obeissant a la loi de lenergie. On a employe, pour predire les caracteristiques decoulement des dites pellicules, une theorie nouvelle basee sur lexistence dune solution ferme et periodique des equations qui decrivent lecoulement des pellicules. Comme on lavait prevu, les diagrammes logarithmiques doubles montrant lepaisseur des pellicules versus le nombre de Reynolds (ReP. L.) se sont averes lineaires jusqu'a un nombre de Reynolds de 100. On a trouve que le rapport entre la surface et la velocite moyenne etait approximativement independent du nombre de Reynolds pour des valeurs prevues par un profil de velocite laminaire. On a constate que la longueur dondes stables etait independante du nombre de Reynolds pour un fluide donne.

Thermal instability of laminar natural convection flow on inclined isothermal plates

Abstract: An analysis is made to deteimine the conditions marking the onset of longitudinal vortices in the laminar natural convection flow over a heated isothermal inclined plate. A linear stability theory based on Boussinesq approximation and without the conventional parallel-flow assumption for basic velocity and temperature profiles is employed in the derivation of perturbation equations. An iterative procedure employing a fourth order Runge-Kutta method is applied in the solution of the perturbation equations. A comparison between the neutral stability resuts obtained with and without the commonly used parallel-flow approximation in the stability theory of small disturbances shows that the parallel-flow assumption is an invalid one for the present problem. Solutions are obtained for Pr = 0.72, 1, 2, 10, 100, and ∞ and the critical Rayleigh number marking the onset of longitudinal vortices is found to be a rather weak function of Prandtl number. A comparison of the present neutral stability results for the inclination angles α = 20° ∼ 60° with experimental data reported in the literature reveals that the theory predicts critical values which are generally two orders of magnitude lower than the experimental data. On fait une analyse pour determiner les conditions qui marquent la production de tourbillons Iongitudinaux dans l'ecoulement laminaire a convection naturelle qui se fait sur une plaque inclinee chauffee d'une maniere isothermique. On emploie, dans l'etablissement des equations de perturbation, une theorie de stabilite lineaire qui est basee sur l'approximation de Boussinesq, mais est depourvue de la supposition classique d'ecoulement parallele pour la vitesse de base et les profits de temperature. On applique, dans la solution des equations de perturbation, un procede iteratif ou l'on utilise une methode de quatrieme ordre de Runge et Kutta. On montre que la supposition de l'ecoulement parallele est sans valeur dans le probleme actuel, en comparant les resultats de stabilite neutre, obtenus avec ou sans l'approximation de l'ecoulement parallele qu'on utilise couramment dans la theorie de stabilite des perturbations faibles. On obtient des solutions pour des nombres de Prandtl de 0.72, 1, 2, 10, 100 et ∞ et trouve que le nombre critique de Rayleigh qui correspond a la production des tourbillons longitudinaux est une fonction pluto't faible du nombre de Prandtl. En comparant, pour les angles d'inclinaison α = 20° ∼ 60°, les resultats actuels de la stabilite neutre avec les donnees experimentales deja publiees, on trouve que la theorie prevoit des valeurs critiques qui sont generalement inferieures de deux ordres de grandeur aux donnees experimentales.

Coalescence and break‐up in dilute polydispersions

Abstract: Functional relationships for coalescence rate dependence on drop size and hold-up were derived via the collision rates and coalescence efficiency. Experiments in an agitated vessel indicated the coalescence rate to be controlled by the viscous flow regime and, per unit drop concentrations, to be proportional to the third power of the sum of the diameters of the two coalescing drops. By combining the experimentally known coalescence rate dependence on drop diameter with the independently determined dependence of the latter on the dispersed phase hold up, the breakup rate was found to depend on d2.0. On a etabli des relations fonctionnelles dans le cas de la dependance qu'a la vitesse de coalescence des dimensions et de la retention des gouttes; on a utilise a cette fin les vitesses de collision et lefficacite de la coalescence. Les experiences faites dans un recipient soumis a lagitation ont indique que la vitesse de coalescence etait regie par le regime decoulement visqueux et qu'elle etait proportionnelle, par les concentrations unitaires des gouttes, a la troisieme puissance de la somme des diametres des deux gouttes coalescentes. En coinbinant la dependance du diametre des gouttes qu'a la vitesse de coalescence, laquelle est connue experimentalement, avec la dependance (determinee independamment) de celui-ci de la retention de la phase dispersee, on a trouve que la vitesse de rupture dependait de d2.0.

Some observations on uniqueness and multiplicity of steady states in non‐adiabatic chemically reacting systems

Abstract: An investigation of uniqueness and multiplicity of the steady states in two non-adiabatic chemically reacting systems, the stirred tank and the tubular reactors, is presented. Exact uniqueness and multiplicity criteria are presented, and some conclusions derived therefrom, for the stirred tank reactor. For the tubular reactor, some numerical results are reported and multiplicities of the type 1-3-1, 1-3-1-3-1 and 1-3-5-3-1 noted. Criteria obtained earlier and those obtained from a lumping approximation of the distributed system are evaluated. In addition, two asymptotic solutions are obtained for the non-adiabatic tubular reactor. On presente une etude de l'unicite et de la multiplicity des regimes stables dans deux systemes non-adiabotiques de reactions chimiques, a savoir les reacteurs tubulaires et a cuve agitee. On indique les criteres d'unicite et de multiplicite exactes ainsi que certaines conclusions qui en decoulent, dans le cas du reacteur a cuve agitee. En ce qui a trait au reacteur tubulaire, on rapporte quelques resultats numeriques et des multiplicites telles que 1-3-1, 1-3-1-3-1 et 1-3-5-3-1 qu'on a observees. On evalue les criteres deja obtenus et ceux qui proviennent d'une approximation globale du systeme reparti. On obtient, en outre, deux solutions asymptotiques pour le reacteur tubulaire et non-adiabatique.

Submerged culture growth of edible mushrooms on waste sulphite liquors

Abstract: Various waste sulphite liquors (WSL) i.e. NH3−, Mg-, Ca-, and mixed-base, were used as substrates for submerged cultivation of four species of edible mushrooms (morel mushroom): Morchella spp., Morchella crassipes, Morchella deliciosa, Morchella esculenta. Growth was found to be completely inhibited by calcium found in both Ca-WSL and mixed-WSL. (In NH3− WSL and Mg-WSL growth generally occurs in large pellet form. The optimal initial pH for the different morel species on various WSL was found to be between 5.0 and 7.0. The highest yield (approximately 83.4% based on utilized carbohydrate) and dry weight (approximately 4.86 g/l) were obtained when the NH3− WSL was diluted (1:5 v/v) and used for growth of Morchella crassipes. Freeze-dried morel mushroom mycelium (MMM) on WSL contains on a dry basis, 25.7-48.0% crude protein, 2.45-4.38% fat, 13.7-39.2% carbohydrate and 5.9-18.0% ash. The spectrum of essential amino acids is comparable to the FAO standard, except for the levels of methionine and isoleucine. A strong mushroom flavor (aroma and taste) is also conserved in freeze-dried powdered samples. On a employe diverses liqueurs usagees au sulfite (LUS), dont les bases etaient NH3−, Mg-, Ca- et un melange de ces cations (MC), comme substrats pour la culture sous l'eau de quatre especes de champignons comestibles (morilles), nommement Morchella spp., Morchella crassipes, Morchella deliciosa et Morchella esculenta. On a trouve que le calcium present dans Ca-LUS empěchait completement la croissance des dits champignons. Dans le cas de NH3−LUS et Mg-LUS, la croissance s'est faite sous forme de grosses boulettes. On a trouve qu'un pH initial de 5.0 a 7.0 etait optimal pour les differentes especes de morilles cultivees sur les types precites de LUS. On a obtenu le meilleur rendement (environ 83.4% base sur l'hydrate de carbone utilise) et le poids sec le plus eleve (environ 4.86 grammes par litre) lorsqu'on dilua NH3−LUS (1.5 v/v) et l'employa ainsi pour la culture de Morchella crassipes. Le mycelium de la morille sechee a l'etat de congelation sur LUS contient a l'etat sec 25.7 a 48.0% de proteine brute, 2.45 a 4.38% de matiere grasse, 13.7 a 39.2% d'hydrate de carbone et 5.9 a 18.0% de cendres. Le spectre des acides aminees essentielles se compare au standard de la FAO, excepte en ce qui a trait aux concentrations du methionine et de l'isoleucine. Une forte de champignon (arǒme et goǔt) persiste egalement dans les echantillons en poudres seches a l'etat congele.