bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanics of a turbulent contact absorber
Authors: Uchida S. , Chang C. S. , Wen C. Y.
Published: March 2009

The operating conditions of a turbulent contact absorber (TCA) can be divided into four regimes. The characteristic behaviour of a TCA in each of the regimes is discussed. The condition below the flooding point is the usual operating regime. Correlations are developed to relate the pressure drop and the liquid holdup of a TCA by the operating variables.

A terminal velocity model is developed to explain the flooding condition of a TCA. With this model, the hydrodynamic behavior of the TCA at the flooding point can be identified.

The total pressure drop and the pressure drop across a single stage are distinguished to clarify the controversy whether the gas velocity can affect the pressure drop of a TCA. The total pressure drop of a TCA is composed of the pressure drop due to distributor loss at the entrance and the pressure drop of the bed itself. The pressure drop of a single stage bed of a TCA is independent of gas velocity.
Unsteady flow of a micro‐polar fluid between two concentric circular cylinders
Authors: Ramkissoon H. , Majumdar S. R.
Published: March 2009

This paper examines the flow of a micropolar fluid between concentric cylinders in the case where the outer cylinder is held fixed while the inner cylinder is subjected to an arbitrary time dependent angular velocity. Here integral transforms are effectively used to obtain closed form solutions. The special case of a periodic angular velocity is then considered. The results obtained are compared as far as possible with their classical counterparts and some of the physical quantities have been represented graphically. It has been found that, in comparison to classical fluids, an increased couple is experienced by the inner cylinder.
A thermal oscillator for optimization of control
Authors: Tennankore K. N. , Bock H. H. R.
Published: March 2009

Bock suggested in 1972 a practical measure for the quality of control of a process as the ratio of ‘external disturbance’ to ‘error’ in the system. Optimization of the control of chemical engineering processes according to this measure requires low frequency filters. In this study a low frequency thermal oscillator has been developed by using a brass rod with a heating section at the middle and a sensing section at one end. The frequency response of this system shows that the equivalent pathlength for heat transfer is more than the distance between the heater and the sensor. Feedback oscillations have been obtained with proper circuitry between the sensor and the heater in dicating the possibility of using the system as a low frequency filter for optimizing the control of a process according to Bock's measure for the quality of control. A scheme for the measurement of the quality of control and its maximization is briefly outlined.
Mass transfer by free convection during electrolysis at inclined electrodes
Authors: Patrick M. A. , Wragg A. A. , Pargeter D. M.
Published: March 2009

The limiting electrolysis current technique has been used to obtain experimental measurements of mass transfer in natural convection at rectangular plane plates. Inclinations varying from horizontal down facing to horizontal upfacing at intervals of 10° have been employed with plate height and electrolyte concentration as additional variables. For attached boundary layer flow conditions, all results are well correlated by the equation:

Attached flow conditions are obtained for all downfacing inclined orientations the vertical position and for upfacing inclinations where θ (the angle from the vertical) is small. Separation of the flow occurs at higher values of θ in upfacing orientations and is demonstrated by Schlieren photography, as is the existence of longitudinal vortices in the flow. The critical Rayleigh number for separation instability is estimated from the mass transfer measurements and compared with results of other authors.
Foam breaking — key process in detoxification of kraft mill effluents by foam separation
Authors: Ng K. S. , Mueller J. C. , Walden C. C.
Published: March 2009

A study was undertaken to demonstrate on pilot plant scale the performance of a turbine foam breaking system and to develop the design parameters for large scale application.

Among various configurations a 3‐blade vaned‐disc turbine was found to be optimal for foam breaking. Major process variables controlling foam breaking were system design, tip velocity, rotation speed, and foam load. A foam breaking system with only restricted liquid draw‐off performed 3 ‐ 16 times better than a conventional flow through system. A 38 cm diameter turbine operating at 1800 τ/min (3600 cm/s tip velocity) collapsed up to 1.2 m3/min (42 ft3/min) of foam.

Design equations developed for sizing of foam breakers suggest that a 61 cm (2‐ft) diameter 21 kW turbine will collapse 4.7 m3/min of foam. For a 95 × 103m3/d foam separation plant, approximately 12 foam breakers are required. Capital costs are estimated at $108,000.
Control of cross‐direction variations in web forming machines
Authors: Boyle Thomas J.
Published: March 2009

Web forming machines are often fitted with control actuators which can be used to produce uniform web properties across the width of the machine. A formal procedure for setting these actuators is presented. It is based on a linear incremental steady state process model and a quadratic objective function. Quadratic programming is used to determine optimum settings. It is shown that the procedure handles limited range actuators, interaction among actuators, and physical constraints on the pattern of actuation. Computing costs are seen as a potential problem when large numbers of actuators are involved.
Separation of mixed granular solids using the fluidized counter‐current cascade principle
Authors: Beeckmans J. M. , Minh T.
Published: March 2009

The countercurrent gas fluidized cascade is a novel device for separating mixed granular solids. It embodies counter‐current mass exchange principles similar to those used in distillation or liquid‐liquid extraction. Results are reported for the separation of sand and carbon mixtures under total reflux conditions.
Film boiling of mercury droplets
Authors: Baumeister Kenneth J. , Schoessow Glen J. , Chmielewski Charles E.
Published: March 2009

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting: therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed‐form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.
The leaching of a chalcopyrite concentrate in ammonia
Authors: Reilly Irvine G. , Scott Donald S.
Published: March 2009

The rate of dissolution of a chalcopyrite concentrate was measured in ammoniacal solutions under oxygen pressure for conditions when chemical reaction rate controlled. Temperatures from 50°‐95°C, oxygen pressures to 689 kPa and ammonia concentrations from 2.5 to 7.0 mol/l were investigated. An electrochemical surface reaction model in which the cathodic reduction of oxygen on the solid surface is rate determining satisfactorily predicts experimental behaviour in the range of experimental data. The activation energy for the reaction was found to be 74.1 kJ/mol.
The oxidation of ortho‐xylene on vanadium pentoxide catalysts. I. Transient kinetic measurements
Authors: Wain Wright M. S. , Hoffman T. W.
Published: March 2009

The gas‐phase oxidation of o‐xylene was studied on commercial vanadia oxidation catalysts, one supported on silica the other on titania.

Kinetic data were obtained under transient and steady‐state conditions in fixed bed and transported bed reactors. Product distributions and rates of conversion were measured in the temperature range 233°C and 390°C. The transient experiments with these catalyst indicate a dramatic decrease in catalyst activity with time, accompanied by a considerable decrease in selectivity to phthalic anhydride and an increase in selectivity to carbon oxides. These data also provide additional support for a two‐step reaction model.

The object of this experimental program is to study the kinetics of oxidation of o‐xylene on vanadium pentoxide catalysts and thereby elucidate the mechanisms of the reaction and some of its characteristics.
Parameters and mechanisms in the solvent extraction of mined athabasca oil sand
Authors: Cormack Donald E. , Kenchington John M. , Phillips Colin R. , Leblanc Patrick J.
Published: March 2009

The efficiency of solvent extraction of bitumen from mined Athabasca oil sands has been studied in laboratory‐scale, batch, stirred vessels. Solvent type, solids concentration, stirrer speed and contact time have been identified as important parameters. A theoretical analysis of the extraction process provides a basis by which the various parameters are assessed in terms of relative overall mass transfer coefficients. However, because the size distribution of the oil sand aggregates is difficult to reproduce, the analysis is limited. Greater reproducibility, and similar quantitative results were obtained for the dissolution of pure bitumen from the bottom of the stirred vessels.

It is shown that highly aromatic solvents such as benzene and toluene can dissolve bitumen 3–5 times faster than an essentially alpha tic solvent such as kerosene. There is evidence, however, which indicates that solvent properties other than aromaticity are also important.

The data indicate that a minimum stirrer speed must be exceeded before the extraction of oil sand or pure bitumen will proceed at a reasonable rate. Above this minimum rate, the mass transfer coefficient increases linearly with stirrer speed. The solids concentration is also important since the data suggest that a higher efficiency is obtained at higher solids concentrations in the range of solid loadings studied.
Second virial coefficients of polar gases for a four‐parameter model
Authors: Lin Hung‐Huei , Stiel Leonard I.
Published: March 2009

The second virial coefficients of polar gases have been studied for a potential function consisting of the Kihara spherical core potential combined with a preaveraged dipole‐dipole interaction term. The molecular parameters ϵ/κ, ρo, a*, and y of this potential function were determined for ten substances by a nonlinear least squares analysis of experimental second virial coefficients. These molecular parameters were related to the critical constants, acentric factors, and fourth parameters of the substances. The resulting equations reproduced the second virial coefficients to within the accuracy of the data. Comparisons with experimental data for substances not included in the development of the relationships indicated that good agreement can be obtained for polar fluids by the method of this study.
The analysis and design of binary vapour‐liquid equilibrium experiments. Part I: Parameter estimation and consistency tests
Authors: Sutton Thomas L. , Macgregor John F.
Published: March 2009

When estimating the unknown parameters in semi‐empirical relationships from vapour‐liquid equilibrium experiments, it has been common practice to minimize the sum of squares of some arbitrary function of one or more of the measured variables (x, y, P, T) without regard to the statistical consequences of such a procedure. It is shown that because these arbitrary procedures do not fully account for the errors in all the variables in the functional relationship they can lead to poor parameter estimates when compared to a statistically sound procedure based on maximum likelihood. The analysis of some binary data sets and a simulation study based on one of them are used to demonstrate the kinds of errors that arise.

Use of the maximum likelihood method of estimation also aids one in checking the adequacy of the model used, and in testing the consistency of the experimental data. This is accomplished by comparing the deviations between predicted and measured responses with their computed confidence limits.
Analysis of the efficiency of reverse flow cyclones
Authors: Beeckmans J. M. , Kim C. J.
Published: March 2009

The efficiency of a 152 mm cyclone was determined for inlet velocities in the range 6.1 — 15.5 m/s, for particle sizes from 0.6 μm to 4.7 μm, using monodisperse methylene blue‐uranine aerosol particles. The efficiency of a geometrically similar 76 mm cyclone was also measured for a few conditions of inlet velocity and particle size. These data and others were correlated by linear regression analyses on a function of cyclone Stokes number and cyclone Reynolds number. It was concluded that in the range of variables spanned by the experimental data, the flow fields within the cyclones depended on Reynolds number, and hence that contrary to the assumptions of most theoretical models, cyclone efficiency is not exclusively a function of Stokes number.
Water droplet vaporization in humid atmospheres
Authors: Frazier George C.
Published: March 2009

Droplet vaporization histories are computed from a semiempirical quasi‐steady model, including natural convection, and compared with the experimental results of Houghton on suspended droplets in the size range of 500 — 1000 μm. This model explains the curvature in the data, and the agreement between theory and experiment is good in most cases, and indicates further, that natural convection effects around water droplets should be negligible for diameters less than a few hundred microns. However, the same model, modified to include the best available form for the forced ventilation factor, consistently under predicts the Duguid and Stampfer observations on 6 — 18 μm, freely falling droplets. It is suggested that this lack of agreement may be due to incipient Brownian motion on the part of these small droplets, which disrupts the surrounding transport film. Additional data in the size range of a few microns are required in order to test and to quantify this hypothesis.
Break‐up of drops and bubbles in stagnant media
Authors: Grace J. R. , Wairegi T. , Brophy J.
Published: March 2009

A simple empirical model is developed based on two‐dimensional linearized Rayleigh‐Taylor stability theory to describe the break‐up of drops and bubbles in stagnant fluids. Splitting is predicted to occur if the growth of indentations on the leading edge is rapid enough relative to the rate at which the disturbance is carried around the interface to the equator. Experimental data on maximum stable sizes of drops and bubbles in viscous liquids are presented for eighteen different systems, covering a range much larger than in previous studies. Agreement between the model and experimental results is favourable.
A comprehensive study on co2‐interphase mass transfer in vertical cocurrent and countercurrent gas‐liquid flow
Authors: Deckwer W.‐D. , Adler I. , Zaidi A.
Published: March 2009

Cocurrent and countercurrent absorption and desorption of CO2 in water was investigated in tall bubble columns (length 440 and 720 cm, diameter 15 and 20 cm, respectively). Operating conditions were applied which provided for high interphase mass transfer rates. Under these circumstances the relative gas holdup varies considerably with axial position whereas the mean bubble diameter measured at two points was found to be approximately constant. The measured data permit the calculation of local values of interfacial areas, superficial gas velocities, and frequency factors for bubble coalescence and break up.

A dispersion model which takes into account the hydrostatic head and a variable gas velocity was applied to describe the measured concentration profiles in both phases. If increased mass transfer coefficients at the column bottom and measured local values of the hold up were used a striking agreement between experimental and predicted profiles could be obtained. The findings lead to a more sophisticated picture of the complex behaviour of gas‐liquid dispersions at high interphase mass transfer rates.
Enhancement factors for gas‐absorption with second‐order irreversible chemical reaction
Authors: Wellek R. M. , Brunson R. J. , Law F. H.
Published: March 2009

A relatively simple and explicit mathematical expression has been developed for estimating the enhancement factors for mass transfer accompanied by a second‐order irreversible chemical reaction. The development is based on asymptotic characteristics, i.e., limiting solutions, for second‐order enhancement factors. The resulting mathematical relation and other approximate analytical formulations previously presented in the literature have been critically compared with a numerical solution for the diffusion‐reaction process based on film theory.
Gas separation by permeation Part II: Effect of permeate pressure drop and choice of permeate pressure
Authors: Pan C.‐Y. , Habgood H. W.
Published: March 2009

Calculation methods for determining pure gas permeabilities and gas separation performance of hollow fiber modules with significant permeate pressure drop inside the fiber are presented. A sequential optimization method for determining the near‐optimum permeate pressures in cascade operation is developed. It is shown that the performance of narrow hollow fiber modules can be significantly affected by the permeate pressure build‐up inside the narrow fiber. For a given module and given recovery there exists an optimum permeate outlet pressure which minimizes the membrane and permeate compression costs. Examples given relate to the recovery of helium from natural gas.
Decomposition of n‐ and iso‐butyl acetates on charcoal
Authors: Pettit Paul J. , Anderson Robert B.
Published: March 2009

The decomposition of n‐butyl acetate on charcoal was studied at 365° and 385°C, and isobutyl acetate at 394° and 419.5°C. Isobutene and acetic acid were the principal products from the iso ester, and n‐butenes and acetic acid from the normal ester. Other primary and secondary reactions exceeded 20% in most experiments. The principal primary product from the normal ester was 1‐butene which isomerized subsequently to 2‐butenes; iso‐butene from the iso ester did not isomerize.

For both esters the activity of the charcoal decreased rapidly, the conversion decreasing linearly with time. Linear correlations were used to estimate the conversion at zero time, and data at zero time were used to evaluate constants of a rate equation. Fouling was attributed to reactions of olefins which produced carbonaceous residues.
Estimation of time delay time constant parameters in time, frequency, and laplace domains
Authors: Sundaresan K. R. , Krishnaswamy P. R.
Published: March 2009

Four methods are proposed for estimating the dominant time constant and dead time of a given process from a knowledge of its moments, s‐plane, frequency or transient response data. The methods are faster and simpler and, in terms of accuracy and reliabiltiy, are comparable to the time domain least squares procedure for parameter estimation. Applications of the methods are illustrated with the aid of a dispersion model. A comparison is also made with other known techniques to demonstrate the superiority of the suggested methods.
The drag and pressure drops for hydrodynamically suspended cylinders in a vertical tube with and without polymer addition
Authors: Lee S. W. , Latto B.
Published: March 2009

The pressure drops and the suspension velocities for hydrodynamically suspended aluminum and steel cylindrical bodies were measured for a range of aspect ratios (L/d) in a 5 cm vertical plexiglass tube. Four different body‐to‐tube diameter ratios (d/D) from 0.432 to 0.864 were investigated. Both water and drag reducing aqueous polymer solutions of Reten 423* having concentrations in the range 20 to 100 ppm by weight were used.

In all cases, the addition of polymer reduced the drag coefficient and the drag coefficient per aspect ratio approached a constant value as (L/d) approaches 14. The available data for cylindrical bodies in vertical pipelines were correlated to obtain semi‐empirical equations relating pressure drops, drag coefficients and suspension velocities.
Kinetics of nitrobenzene hydrogenation using a gel entrapped palladium catalyst
Authors: Tong S. B. , O'Driscoll K. F. , Rempel G. L.
Published: March 2009

Palladium metal has been precipitated in a gel formed by the crosslinking polymerization of 2‐hydroxyethylmethacrylate. The metal particles were found to have an average size of 14 nm. The dried polymer gel contained 1.38% Pd; it was crushed and sieved to give gel particles ca 200 μm in size. When the gel containing Pd was swollen by a solvent, catalytic activity toward the quantitative hydrogenation of nitrobenezene to aniline was observed. A detailed study of the kinetics of this hydrogenation revealed that at 101 kPa pressure and 31°C, resistance to the reaction was approximately equally divided between extra‐particle mass transfer and the chemical activity of the Pd. The high activity of this novel catalyst is attributed to the large surface of the Pd and the extensive swelling of the gel by the reaction medium.
Dynamic modeling of ph electrodes
Authors: Hershkovitch Hugo Z. , Mcavoy Thomas J. , Liapis Athanasios I.
Published: March 2009

A mathematical model for the dynamic behavior of the pH glass electrode is presented. The model results from a description of ionic transport in an assumed stagnant boundary layer around the electrode surface. Documented information regarding the characteristics and operation of the glass electrode and the mechanism of pH measurements is combined with dynamic mass balances in an attempt to describe its transient response. New experimental results are presented which indicate both the validity of the model and that double layer effects are also contributors to the dynamic response. One of the interesting features of the model is that it predicts that if an electrode is subjected to a step change from a solution of a strong acid at a given pH to another solution of the same acid at the same pH but containing a salt of that acid, a transient response will result. This effect has been observed experimentally and is due to the differences in the diffusivities of the various ionic species present in the solutions.
Drop size distribution for spray by full cone nozzle
Authors: Sada Eizo , Takahashi Katsuroku , Morikawa Kazuhiko , Ito Shigeru
Published: March 2009

Experiments were carried out to measure the drop size distribution in the spray produced by a full cone nozzle. At the center of the spray the distribution has one peak that can be expressed as a logarithmic normal distribution function. However, the distribution at other part of the spray has two peaks. Here it can be expressed as the sum of two distribution functions. At the vertical distance of 50 cm from the nozzle and the radial distance of 20 cm from the center of the spray, the geometric mean diameters of the first and the second peak are 61 and 235 μm, respectively, for an injection pressure of 294 KPa. For the same condition, the logarithmic standard deviations of the first and the second peak are 2.08 and 2.40, respectively. At the same position in the spray the geometric mean diameter varies in proportion to —0.2 power of injection pressure and the logarithmic standard deviation does not depend on injection pressure.
A mathematical model for concentric horizontal capsule transport
Authors: Van Den Kroonenberg H. H.
Published: March 2009

For designing capsule pipeline systems the designer needs preferably simple mathematical models, to make quick calculations of the main characteristics of the system. For this purpose an easy to handle mathematical model for horizontal concentric capsule flow is proposed. In this model separate friction coefficients for the moving capsule wall and the pipe wall are introduced. These friction coefficients can be taken from the Moody chart. In the model only relatively long capsules are considered so that end effects can be neglected. The model gives expressions for the capsule velocity and the pressure difference across the capsule. Test results are in good agreement with the proposed model.
Conditions needed for satisfactory measurement of mass transfer coefficients, internal diffusivity and adsorption rate constants
Authors: Gangwal Santosh K. , Hudgins Robert R. , Silveston Peter L.
Published: March 2009

Conditions are developed for the accurate measurement of mass transfer coefficients, internal diffusivity and adsorption rate constants using pulse gas chromatography within the limits of the approximation of the Kubin‐Kucera model for adsorption in a packed bed. Physisorption rates are shown to be many orders of magnitude higher than those measurable. Thus, pulse chromatography cannot be used to determine physisorption rate constants. Mass transfer coefficients at low Reynolds Numbers are shown to be measurable under severely restricted conditions.
Characterization and methanation activity of supported nickel catalysts
Authors: Bhatia S. , Bakhshi N. N. , Mathews J. F.
Published: March 2009

The methanation of carbon monoxide was studied over various supported nickel catalysts in a fixed bed reactor in the temperature range of 250 to 400°C. The hydrogen to carbon monoxide ratio was kept higher than stoichiometric in order to avoid carbon formation. The catalyst particles had an average diameter of 80 pm and nickel contents ranging from 5 to 42 wt %. The performance of laboratory prepared catalysts was compared with commercial ones. The catalysts were characterized by BET surface area, pore volume and carbon monoxide chemisorption. Specific activities for the methanation reaction were obtained and were found to vary with nickel concentration and with crystallite size. There exists a crystallite size range in which the maximum activity was observed. Metal support interactions may also contribute to the vdation in specific activity. The activation energy was found to vary from 58.2 MJ/kmol to 119.4 MJ/kmol. It appears that the methanation reaction over Ni/aIumina catalysts is a structure sensitive reaction. A compensation effect was observed for this reaction.
Volume reaction model for pyrolysis of a single solid particle accompanied by a complex reaction
Authors: Fan Liang‐Shih , Fan L. T. , Tojo K. , Walawender W. P.
Published: March 2009

A fairly general model is proposed for the pyrolysis of a single solid particle accompanied by consecutive reactions. The model not only takes into consideration the transient heat transfer, mass transfer, and chemical reaction simultaneously but also the functional dependencies of various parameters on the variation of the solids concentration and temperature in the particle. The effects of the heat of reaction, Thiele modulus, and rate of reaction on the solids reactant conversion, concentration profiles and temperature profiles are analyzed and graphically presented.
Intermittent two phase flow in horizontal pipes: Predictive models
Authors: Nicholson M. K. , Aziz K. , Gregory G. A.
Published: March 2009

A semi‐mechanistic model for two phase gas‐liquid slug flow proposed recently by Dukler and Hubbard has been modified and extended to apply to the entire intermittent flow regime. Flow predictions of the model proposed in this paper are compared with detailed experimental data recently obtained for an air‐oil system.

The model requires the use of empirical correlations for the slug velocity and the in situ liquid volume fraction in the slug.

In addition, either the slug frequencies or length corresponding to the given design conditions must be known. However, calculated values of average pressure gradient and in situ liquid volume fraction are relatively insensitive to these latter parameters, and in fact, good results are obtained assuming a constant slug length.

The paper includes a discussion of the limitations of the proposed model and the expected direction of further study required to extend its mechanistic aspects.
Bubble formation in flowing liquid
Authors: Sada Eizo , Yasunishi Akira , Katoh Shigeo , Nishioka Masashi
Published: March 2009

Initial bubbles in flowing liquid from a nozzle were observed from two mutually perpendicular directions. Two nozzles of 0.086 cm and 0.305 cm in diameter were used. The gas flow rate and the superficial liquid velocity ranged from 0.33 cm3/s to 36.2 cm3/s and from 0 cm/s to 154.9 cm/s, respectively.

The bubble size formed in flowing liquid decreased with decreasing gas flow rate and with increasing superficial liquid velocity. Three types of bubble formation, i.e. single bubbles, coalescent bubbles and gas jets, were observed depending upon the gas rate and the liquid velocity. Two empirical equations of the bubble sizes are given.
Batch sedimentation of red mud suspensions in an inclined tube
Authors: Sarmiento G. , Uhlherr P. H. T.
Published: March 2009

The batch settling behaviour of lightly flocculated red mud in inclined tubes has been investigated experimentally. A simple model is proposed which describes the behaviour observed for this suspension better than models at present available from the literature. The new model is based on the Nakamura‐Kuroda equation into which a correction factor is introduced. For red mud, this factor is found to be a simple function of the angle of inclination and to be independent of solids concentration. This is in contrast to the various correction factors that have been proposed by other authors who have found strong and complex dependence on both solids concentration and angle of inclination. Thus, in the case of the suspension studied, the model represents considerable simplification of the description of inclined settling behaviour. The observed regimes of behaviour in inclined tubes are also discussed in the light of mechanisms observed in vertical settling for the same suspension.
Review of some useful rheological equations
Authors: Carreau P. J. , De Kee D.
Published: March 2009

A variety of constitutive equations have been proposed in recent years to describe the behaviour of polymer solutions and melts. Rather complete reviews of most of the differential and integral equations proposed prior to 1967 have been given by Spriggs, Huppler and Bird(1) and by Bogue and Doughty(2,3). Since then, numerous efforts have been directed towards the development of equations capable of predicting adequately nonlinear and transient properties of polymer solutions and melts.

Considerable information can be found in the recently published works by Bird et al.(4,5).

Some of the more successful models are presented here in an uniform notation. The models are evaluated in terms of their ability to simultaneously describe some or most of the rheological functions such as the non‐Newtonian viscosity, the normal stress difference functions, the components of the complex viscosity, stress growth and stress relaxation.
A preliminary study of interfacial areas in vertical cocurrent, two‐phase upflow
Authors: Watson Alex P. , Cormack Donald E. , Charles Michael E.
Published: March 2009

Pseudo‐first order chemical absorption was used as the basis for determining the effective interfacial area available for mass transfer in gas‐liquid, cocurrent, upward pipe flow. The study, which was performed in a 2.54 cm I.D. tube, encompassed the slug and froth flow regimes.

The interfacial area displayed a strong dependence upon the coordinates of the flow regime map proposed by Oshinowo and Charles(16). In addition, the systematic variation of surface area could be rationalized on the basis of flow regime geometry. Unfortunately the data could not be used to assess previous surface area models due to the unresolved diameter dependence of these models.

Observations are also made concerning the apparently significant effect of chemical composition on interfacial surface area, and concerning the inadequacy of the popular methods used for estimating frictional pressure drop in vertical two‐phase flows.
The coalescence of n‐hexane droplets in aqueous solutions of n‐alcohols
Authors: Sagert Norman H. , Quinn Michael J.
Published: March 2009

Coalescence times, measured by high speed cinematography, are reported for n‐hexane droplets formed and grown on adjacent nozzles in equilibrated aqueous solutions of ethanol, n‐butanol, n‐hexanol, n‐octanol, n‐decanol and n‐dodecanol. The drops remained attached to the nozzles throughout the coalescence process. Coalescence times increased when alcohols were added to the system. Very similar results were obtained for the alcohols n‐hexanol to n‐dodecanol. When these alcohols, which are much more soluble in n‐hexane than in water, were present, the observed coalescence times could be accounted for best by considering diffusion processes occurring in the n‐hexane. For ethanol and n‐butanol, which are more soluble in water, diffusion processes occurring in the water had to be considered as well.
Kinetics of sorption in bi‐porous molecular sieves — Part I. Mathematical models for systems with rectangular equilibrium isotherm
Authors: Lee Lap‐Keung , Ruthven D. M.
Published: March 2009

The coupled diffusion equations describing transport in a bi‐porous adsorbent (micropore‐macropore) have been solved in order to obtain the theoretical uptake curves for such a system when the adsorption equilibrium isotherm is rectangular. Solutions are presented for both the step change boundary condition generally encountered in adsorption from the gas phase and for the more complex case which is encountered in studies of adsorption from the liquid phase, when the composition of the ambient fluid changes significantly during the course of an experiment. The theoretical uptake curves are compared with the corresponding curves for a linear system.
Direct hydrogenation of hybrid poplar wood to liquid and gaseous fuels
Authors: Boocock D. G. B. , Mackay D. , Mcpherson M. , Nadeau S. , Thurier R.
Published: March 2009

Fast growing hybrid poplar suspended in water has been treated with hydrogen at temperatures of around 350°C and pressures of about 10 MPa (100 atm) in the presence of Raney‐nickel. Complete conversion of the wood to oil and gas has been achieved. The oils, which appear to derive predominantly from the lignin, contain about 10 percent oxygen and have heating values of up to 40.8 MJ/kg (17,550 BTU/Ib). The gas, which is mostly methane, appears to derive from the celluloses and contains no carbon monoxide. Treatment of purified cellulose yields only gases and water soluble organics.
Kinetics of the dehydrogenation of ethanol to acetaldehyde on unsupported catalysts
Authors: Peloso A. , Moresi M. , Mustachi C. , Soracco B.
Published: March 2009

A kinetic study of the dehydrogenation of ethanol to acetaldehyde on an unsupported catalyst of base composition CuO – Cr2O3 was carried out in an isothermal reactor fed with ethanol 95% vol. in the temperature range 225–285°C with space velocities 1.5–7.5 LHSV at atmospheric pressure.

The mechanism which was found suitable to describe the reaction was that of surface adsorption on dual sites.

Taking into account interphase and intraphase diffusion, the observed conversions of ethanol were reconstructed with a standard error below 10%, thus confirming the validity of the physical assumptions.
Transport effects in the manufacture of reaction‐bonded silicon nitride
Authors: Hughes G. S. , Mcgreavy C. , Merkin J. H.
Published: March 2009

The transient behaviour of the exothermic, irreversible, silicon‐nitrogen reaction is analysed, using mixed type boundary conditions to represent external resistances. The mathematical model incorporates a sharp cut‐off reaction into the moving reaction zone, in the heat mass transfer field, and the resulting system of equations is solved numerically using an explicit finite difference scheme. Effects of varying the Thiele modulus, Prater temperature and Biot number are examined, together with the different geometrical effects. The results are graphically presented and interpreted.
The gravity clarifier as a stratified flow phenomenon
Authors: Cordoba‐Molina J. F. , Hudgins R. R. , Silveston P. L.
Published: March 2009

A problem that has plagued the designers of gravity clarifiers is that of obtaining a uniform and stable flow field necessary for efficient sedimentation.

Clarifier operation is a fluid problem which, up to now, has been viewed in terms of homogeneous fluid concepts. In this paper we show that by treating clarifier flow as stratified (i.e. a fluid with variable density), it is possible to obtain a uniform and stable flow field. If this flow condition can be realized in full‐scale units, it should provide significant increases in removal performance or clarifier capacity at a constant removal.
On the efficiency of a centrifugal fan wet scrubber
Authors: Nguyen X. T.
Published: March 2009

An inertial theoretical model is proposed to predict the capture of aerosol particles by accelerating liquid droplets in a centrifugal fan scrubber. The results are in good agreement with literature experimental data for micron and large submicron size particles. The theory tends to underestimate the scrubber performance for submicron size particles of less than 0.3 μm in diameter. The discrepancy may be due to the lack of a reliable expression predicting the diffusion deposition of aerosol particles on an isolated liquid droplet. The effects of variables such as fan speed, sizes of liquid droplets and particles, gas and liquid flow rates predicted by the theory are discussed and agree with literature observation.
Mixing in water elutriators
Authors: Biddulph Michael W.
Published: March 2009

This paper describes the results of an experimental and theoretical study of a water elutriator. An eddy mixing model is proposed and a photographic study of the behaviour of glass and plastic spheres in an operating elutriator appears to confirm the model. Values of the eddy diffusion coefficient are presented for a range of conditions. The correlation of the eddy diffusion values is encouraging, and the results will be useful in the design and evaluation of commercial elutriators separating solid species.
Stabilité de V2O5supporte sur SiO2, comme photocatalyseur de l'oxydation du cyclohexane
Authors: Nguyen D. L. , Roberge P. C. , Kaliaguine S.
Published: March 2009

The activity of Vanadium pentoxide supported on silicagel for the photocatalytic oxidation of cyclohexane has been studied. It was found that this catalyst presents a stable activity after an or decrease depending on the surface concentration of VOshrd initial unsteady state period during which the activity might increase or decrease depending on the surface concentration of V2O5. An interpretation is proposed for the two phenomena affecting the activity during the unsteady state period.
Simulation and design of distillation units for treatment of sulfite pulping condensates to recover methanol and furfural: Part II: Applicability of multiple‐effect distillation using live steam
Authors: Aly G. , Zacchi G.
Published: March 2009

A distillation unit has been designed for a capacity of 73 t/h of condensate and for at least 90% recovery of the contaminating organics. This unit consists of three columns: a primary stripper to remove volatile organics and two upgrading columns to purify the methanol and furfural byproducts.

Three different energy‐saving alternatives for satisfying the energy requirements have been studied: utilisation of secondary steam from the evaporation plant, and application of the principle of multi‐effect distillation in one‐stripper and in two‐stripper configurations.

Investment cost needed in all alternatives amounts to 5.5–6.0 MCr (millions of Swedish Crowns) while operating cost varies between 0.8–3.1 MCr. The first design alternative has a payoff period of 2.3 years while the two multi‐effect distillation alternatives have a payoff period of about 3 years.
Foam fractionation of spent sulphite liquor: Part II: Separation of toxic components
Authors: Berk Dimitrios , Behie Leo A. , Zajic James E.
Published: March 2009

Foam fractionation was used as a unit operation for the reduction of toxicity in spent sulphite liquor. Toxicity was measured quantitatively using a Daphnia magna bioassay. The optimum pH for the operation was 10 and no toxicity removal was possible at pH values less than 8. The maximum decrease in the toxicant concentration was 40%. The collapsed foam was very toxic to D. magna indicating that toxicants were concentrated in the foam which contained 20% of the original liquid charged to the column. A relationship between surfactant and toxicant concentration was shown to exist.
Behavior of tar sand bitumen with paraffinic solvents and its application to separations for athabasca tar sands
Authors: Funk Edward W.
Published: March 2009

A study was made of the dissolution of tar sand bitumen using low‐molecular‐weight paraffinic solvents at essentially ambient temperatures. The experimental data were obtained using the spinning disc technique, liquid‐fluidized beds, and direct particle‐size analysis of the insolubles. The results are consistent with a mechanism where the paraffins leach the soluble oil from the bitumen and leave behind a porous network of insoluble asphaltenes. This phenomenon of oil diffusing through an asphaltene layer was modeled using Fick's law for unsteady‐state diffusion. An understanding of the mechanism of bitumen extraction with paraffins and also the effect of fluid mechanics in the tar sand system have been applied to obtain a novel separation of deasphalted oil and asphaltenes from Athabasca tar sands. This new separation technique has the potential of simplifying downstream processing for the bitumen and also of avoiding environmental problems associated with the present tar sand extraction technology.
A numerical technique for the estimation of critical constants and of Lennard‐Jones (12–6) parameters. Application to tetramethyl and tetraethyl compounds
Authors: Rummens Frans H. A. , Rajan S.
Published: March 2009

A numerical technique is given which allows the estimation of critical constants from vapor pressures at any two temperatures and the liquid density at any temperature. It is shown that such a technique can also be used to test the accuracy of vapor pressure data. This method is applied to the compounds X(CH3)4 and X(CH2CH3)4, where X=C, Si, Ge, Sn and Pb. For these same molecules estimates are given for their σ and ϵ/k Lennard‐Jones (12–6) parameters, based on the calculated critical constants.
Transferring information from one experiment to another
Authors: Hoffman Terrence W. , Reilly Park M.
Published: March 2009

This paper presents a rational method (based on Bayes' Theorem) for transferring information on parameter values from one experiment to another, in situations where the mathematical models for the two experiments share some parameters in common. The uncertainty in the estimates of the parameters, which reflects the experimental error in the initial experiment, is properly transferred as well.

The use of the method is demonstrated by applying it to a fairly complicated system, typical in chemical reaction engineering, in which the kinetic parameters in a model for the hydrogenolysis of butane reaction were estimated using data obtained from a bench‐scale, integral packed‐bed reactor. These parameter estimates were then transferred to a model for a fluidized bed reactor in which the same chemical reaction occurred. Using the fluidized bed data they were updated and two additional parameters in the fluidized bed model were also estimated. This procedure allows a more realistic estimate of the uncertainty in all parameter values in the model for the fluidized bed reactor.
Characteristics of a hydro‐filter pressure drop, liquid hold‐up and liquid overflow rate
Authors: Uchida S. , Sumiyama M. , Kageyama S.
Published: March 2009

An experimental study of the effect of operating conditions on the characteristics of a hydro‐filter (Marble bed scrubber) has been performed. There are stable operating regions of a hydro‐filter with respect to the gas flow rate, the packed bed height and the height of an overflow pipe above the bed.

The total pressure is mainly composed of the pressure drops in two sections, the packed section and the bubble section. The pressure drop in the packed section can be estimated from the correlation for a cocurrent gas‐liquid upward flow packed bed given by Turpin ad Huntington.
Turbulent flow behaviour of dilute polymer solutions in an annulus
Authors: Tiu Carlos , Chee Ngee‐Onn
Published: March 2009

An experimental study has been carried out to investigate the turbulent flow behaviour of dilute polymer solutions in an annulus. The polymers used are two grades of Separan, AP30 and MG500, both are known to exhibit drag reduction characteristics in turbulent pipe flow. Similar drag reduction phenomena have been observed in annulus flow. At a given Reynolds number, the friction factor decreases with increase in polymer concentration and appears to reach a minimum (or maximum drag reduction) at certain optimum concentration. An estimate of the critical wall shear stress, which marks the onset of drag reduction, is consistent with pipe flow results, suggesting that the critical value is independent of flow geometry and size. A lower drag reduction, achieved in an annulus in comparison with circular pipes, is attributed mainly to a diameter effect.
Simultaneous heat and mass transfer in turbulent gas streams in wetted‐wall columns
Authors: Hikita H. , Ishimi K. , Asano K. , Ohba Y.
Published: March 2009

The effect of the gas and liquid flow rates on the gas‐phase mass and heat transfer rates in turbulent gas streams in wetted‐wall columns with cocurrent and countercurrent gas‐liquid flow was studied. The experiments were carried out on the adiabatic vaporization of water into a turbulent air stream under both conditions of rippling and no rippling on the surface of the falling liquid film. The experimental results showed that the effect of the gas and liquid flow rates on the mass and heat transfer rates are in good agreement with the theoretical predictions and that the effect of the rippling on the mass and heat transfer rates can be neglected.
Solution of the SSAM or redox equations
Authors: Mclean D. D. , Boag I. F. , Bacon D. W. , Downie J.
Published: March 2009

An efficient procedure for solving the steady‐state adsorption model (SSAM) or oxidation‐reduction model (REDOX) equations is presented for batch, plug flow and backmix systems.
The oxidative dehydrogenation of ethylbenzene to styrene
Authors: Degannes Percival N. , Ruthven Douglas M.
Published: March 2009

The results of a kinetic study of the oxidative dehydrogenation of ethylbenzene to styrene over an organic catalyst (pyrolyzed polymerized acrylonitrile) are reported. The reaction is found to be second order in ethylbenzene and zero order in oxygen with an activation energy of 76.5 kJ/mol. The rate equation is: \documentclass{article}\pagestyle{empty}\begin{document}$ - r(mol/\min .g\,catalyst) = 3.2 \times 10^9 \exp [ - 76,500/RT] \cdot C_{EtB}^2 \cdot C_{O_2 }^0 $\end{document} where R = 8.31 J/niol.K and concentration (CEtB) is expressed as mol/L. The catalyst is more active than conventional metal oxide catalysts and appears to be quite stable under reaction conditions. The results suggest that, using the PPAN catalyst, it may be possible to reduce the operating temperature of the oxidative dehydrogenation of ethylbenzene to about 250‐300°C, thereby avoiding some of the problems of the present high temperature process.