bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal instability of laminar natural convection flow on inclined isothermal plates
Authors: Hwang G. J. , Cheng K. C.
Published: March 2009

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.
Hydrogen sulphide — air equilibria under claus furnace conditions
Authors: Bennett H. A. , Meisen A.
Published: March 2009

Equilibrium compositions of mixtures resulting from reactions between hydrogen sulphide and air at atmospheric pressure were calculated for temperatures and O2/H2S ratios ranging from 600 to 2000°K and 0.05 to 1.0, respectively. Forty‐four compounds containing nitrogen, hydrogen, oxygen and sulphur were assumed to be formed but only 25 had concentrations exceeding 0.1 ppm. These compounds should not, as in previous studies, be omitted from equilibrium calculations. Sulphur yields are shown to be increased by approximately 10% if O2/H2S ratios less than stoichiometric are used. Reasons for this and implications for Claus plant operation are provided.
Oxidation of propionic acid solutions
Authors: Day D. C. , Hudgins R. R. , Silveston P. L.
Published: March 2009

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.
The screening and selection of solvents for the extraction of phenol from water
Authors: Kiezyk Peter R. , Mackay Donald
Published: March 2009

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.
Coalescence of drops in a liquid‐liquid dispersion by passage through a fibrous bed
Authors: Rosenfeld J. I. , Wasan D. T.
Published: March 2009

A model which describes the operation of a fibrous bed coalescer is presented. From this model, a theoretical equation can be derived for the filter coefficient, λ, at small velocities where the effect of turbulence is negligible. This expression which considers the void fraction of the bed, ϵ, the drop diameter, dp, the average saturation, Sm, the fiber diameter, dP, and the effective fiber diameter dfe, is:where β is the fraction of collisions which lead to coalescence. At larger velocities, a suitable empirical equation is obtained by multiplying the above expression by the square root of the velocity at which the filter coefficient begins to decrease divided by the superficial velocity. These equations describe the data of various workers.

A method of obtaining the average saturation in a fibrous bed is presented. A possible correlating equation is found to be:where U is the superficial velocity.
Vertical two‐phase flow part I. Flow pattern correlations
Authors: Oshinowo Toks , Charles M. E.
Published: March 2009

Two‐phase gas‐liquid flow has been investigated in a 1‐inch internal diameter vertical tube coil containing two risers and a downcomer all connected by “U” bends. Flow pattern data were obtained in the three vertical tubes, each 17.30 ft. long, for five different air‐liquid systems at about 25 psia over flow ranges of 0–700 lbmair/min‐ft2and 140–25300 lbmliquid/min‐ft2. Liquid phase viscosities ranged from 1 to 12 cp.

A flow pattern classification with six regimes including coring‐bubble, bubbly‐slug, falling film, falling bubbly‐film, froth and annular flow regimes was established for downflow. Flow patterns in the bends were also classified.

Data from the present investigation were used to formulate an empirical flow pattern graphical correlation for both upflow and downflow which is based upon the coordinates (Rv)1/2and FrTP/A, where Rvis the delivered gas‐to‐liquid volume ratio, FrTPis the mixture Froude number, and A = μs/(SLσs3)1/4in which μs, SL, σsare specific viscosity, specific density and specific surface tension respectively of the liquid with reference to water. The correlation was satisfactorily tested with independent literature data for upflow systems, including air‐water, steam‐water at various pressures, nitrogen‐mercury and air‐heptane, and data from flowing gas‐oil wells. No independent literature data appear to be available for testing the correlation for downflow systems, but it is anticipated that the correlation will prove to be generally applicable.

The coring phenomenon in downward bubble flow was examined by means of high speed motion photography and is explained by the development of a lift force on a bubble.
The effect of mass transfer on flow characteristics in vertical two‐phase unstable flow
Authors: Golding J. A. , Mah C. C.
Published: March 2009

Studies carried out on the absorption of hexane from inert carrier gases into paraffin oil have shown that mass transfer can affect flow characteristics in unstable vertical two‐phase flow. In the absence of mass transfer chain‐flow patterns prevailed. These patterns were broken when mass transfer took place from the gas to the liquid phase. Bullet shaped slugs were then formed, the slugs pairing and coalescing as they rose up the column. The direction of mass transfer was critical no effect on flow pattern being observed when mass transfer took place from the liquid to the gas phase.

Slug frequencies and slug sizes were found to be influenced by mass transfer and an effect of overall absorber length was observed. Individual slug sizes and separation distances were measured and varied widely even under constant flow conditions. Rise velocities were correlated using an equation of the form:where C2 was a function of the fluid flow‐rates and system physical‐properties.
Developments in spouted bed technology
Authors: Mathur Kishan B. , Epstein Norman
Published: March 2009

The spouted bed, though originally developed for drying of coarse granular solids, has, over the last decade, proved to be of interest for carrying out a remarkably wide variety of operations. These include not only other diffusional and/or thermal operations such as heating or cooling of solids, drying of solutions and suspensions onto inert bed particles, particle coating, and granulation, but also certain mechanical functions like solids blending, comminution and aerosol collection from a gas stream. The use of spouted bed reactors for several chemical processes — coal carbonization, shale pyrolysis, ore roasting, cement clinker production, and thermal cracking of petroleum — has also received attention.

This paper presents a review of the above developments, supplemented in a few cases by recent results of research being carried out at the University of British Columbia. The particular features of a spouted bed which play the key role in each type of application are identified, some new applications are suggested and consideration given to the future industrial potential of individual processes.
Residence time distribution of gas in spouted beds
Authors: Lim C. J. , Mathur Kishan B.
Published: March 2009

Stimulus‐response experiments have been carried out, using helium gas as tracer, to measure the residence time distribution of gas in spouted beds. The data obtained, under a variety of experimental conditions, are compared against predictions from a two‐region gas flow model. The model postulates plug flow of gas in the spout and axially‐dispersed plug‐flow in the annulus, the extent of axial dispersion being accounted for by a coefficient, D, which is an adjustable parameter of the model. The values of D thus determined were found to increase with gas flow rate, to be relatively insensitive to bed path, and to be much larger for beds of wheat than of polystyrene.
The application of soil mechanics to spouted bed design
Authors: McNab G. S. , Bridgwater J.
Published: March 2009

The annular material around a spout may be considered to be a loosely packed assembly of particles with its behavior described by effective stresses using the Mohr‐Coulomb failure criterion as employed in soil mechanics. The work shows the development of a height‐independent stress model together with an interpretation of the mathematical results in physical terms. The form of a simple equation for spout diameter is shown which gives some information about the interactions between the spout and the annular material.
Minimum air requirement for spouting mixed particles
Authors: Brunello Giovanni , Nina Gilberto Della , Nunes Francisco Carlos S. , Nascimento Claudio Augusto O.
Published: March 2009

Minimum spouting velocity data for beds of soybean (dp = 0.246 in.) and sorghum (dp = 0.142 in.) mixtures contained in a 12 in. diameter column are reported. The agreement of some of the existing correlations is tested against these data, and an empirical equation for this particular case is proposed.
Pressure and flow characteristics of a gas phase spout‐fluid bed and the minimum spout‐fluid condition
Authors: Nagarkatti A. , Chatterjee Asok
Published: March 2009

Spoutfluidization is a new technique for solid‐fluid contact which aims at incorporating the advantages of spouted bed and fluidized bed technique.

The characteristics of physical state of the bed with the variation of the variables which include flow of fluid, particle diameter, orifice diameter, bed height, are studied in this investigation. Experimental study of minimum spoutfluidizing velocity using glass beads with mean particle diameters from 0.254 to 0.600 mm has been carried out in a 90 mm glass column with three spouting inlet orifice sizes at different bed heights. Phase diagrams indicate that the minimum spout‐fluid flow rate in a gas‐solid system may be a point property for a given bed. A correlation is presented in which the standard deviation of experimental from calculated minimum spoutfluidizing velocity is within 5%.
Precipitation of sparingly soluble salts: A model of agglomeration controlled growth
Authors: Baker C. G. J. , Bergougnou M. A.
Published: March 2009

A model describing the role played by agglomeration in the growth of precipitates of sparingly soluble salts is presented. The model predicts that the mean size of the precipitate should increase with the agglomeration and unit particle generation rates, and that the resulting size distributions may be log normal. These findings qualitatively confirm previous experimental results. The model also shows that the precipitate size characteristics can be described in terms of a single parameter, a dimensionless drawdown time.
Vapor‐liquid equilibrium in the ethane‐carbon dioxide system
Authors: Hamam Salah E. M. , Lu Benjamin C. Y.
Published: March 2009

Vapor‐liquid equilibrium compositions were measured at four isothermal conditions from −60°F to 60°F over the pressure range from 101.5 to 827.0 psia for the binary system ethane‐carbon dioxide. A forced recirculation apparatus was employed for the determination.

The data obtained were found to be thermodynamically consistent, and were compared favorably with the values predicted by means of a modified Redlich‐Kwong equation of state especially at the lower temperatures.
Sliding in inclined slurry pipelines at shutdown
Authors: Shook C. A. , Rollins J. , Vassie G. S.
Published: March 2009

The sliding phenomenon which is reported to impose a restriction upon the slope of slurry pipelines is investigated experimentally. Two different types of behavior which could be called “sliding” were observed.

At pipe inclianations greater than 22° to the horizontal, fully settled layers of solid particles would slide with shear occurring at or near the pipe wall. The critical angle of inclination increased as the particle size decreased.

When the slurry was not fully settled, a natural convective flow process was observed to move the slurry down a pipe incline. This flow occurred at much lower pipe inclinations. Concentration profiles measured near the bottom of a pipe incline showed little effect of slurry type or concentration, provided the slurry contained a significant amount of slowly settling solids. In this case, pipe slope was the most important variable.
Cyclic electrodialysis: Experimental results in a closed system
Authors: Thompson D. W. , Bass D.
Published: March 2009

Experimental results are presented for cyclic reflux operation of an electrosorption — desorption separation process. Solute is alternately absorbed by, or desorbed from, a stack of multilayer ion‐selective membranes in a modified electrodialysis cell by periodically reversing the polarity of the applied electric field. Solution passes through a single set of flow channels parallel to the membrane sheets, and the flow alternates in direction synchronously with the electric current cycle. An axial concentration gradient is set up within the cell so that dialysate is produced at one end of the stack and concentrated solution at the other.

Two cell designs are described, one containing a single stack of membranes, the other built in a modular arrangement with up to eight stacks in series. The effect of nine system parameters on the separation of aqueous NaCl solutions is reported for the first unit. Separation factors of up to 40 were obtained. For the second unit, the effect of channel length, displacement cycle, applied voltage and initial concentration on the rate of separation, the final separation factor, and the current consumption are reported. This unit has longer channels, more uniform flow distribution and less axial dispersion than the earlier design and gave separation factors > 103 with NaCl solution. Applications of the process to continuous separation in open systems are discussed.
Polymerization of butadiene with tii4‐Al(i‐Bu)3 catalyst: Part I: Kinetic study
Authors: Loo C. C. , Hsu C. C.
Published: March 2009

A kinetic study on the polymerization of butadiene in toluene with TiI4‐Al(i‐Bu)3 catalyst has been carried out in a batch reactor. The effects of catalyst concentration, Al/Ti ratio, initial monomer concentration and temperature on the polymerization rate and the molecular weight distribution were investigated. It was found that the rate of propagation which is first order with respect to monomer concentration is a function of Al/Ti ratio, having a maximum rate at a ratio of 1.5 and decreasing rapidly as ratio increases. The number of active sites which is directly proportional to the concentration of Til4, is the prime determinant of the molecular weight of the polymer, yet the growth of the living polymer molecules is regulated by the chain transfer reaction to aluminum alkyls. The termination reaction was found significant only at Al/Ti ratio where the catalyst is most reactive.
A study of the effect of optimization function on calculated parameters of wilson equation
Authors: Brinkman Norman D. , Tao Luh C. , Weber James H.
Published: March 2009

Estimated values of Wilson parameters depend upon the objective function which is used in the optimization procedure. The relationships between these estimated parameters seem to be more important than the values themselves, and the desirable paired parameters are confined to a region near ridge lines. This region represents a high level of joint confidence.

In this study four different objective functions were used in the investigation of binary and ternary systems. Also, comparisons were made on calculated V/L equilibrium values predicted for ternary systems by using parameters estimated from binary and from the sole use of ternary data. Using the parameters estimated from binary data with a chosen objective function did not produce the best sum of squares of errors in a ternary system for the same objective function. Based on the overall performance, the best objective function to fit parameters in three ternaries is the one to fit the pressure.
Hydraulic characteristics of a valve in two‐phase flow
Authors: Tremblay P. E. , Andrews D. G.
Published: March 2009

In the case of boiling in nuclear reactor channels, it is apparent that the hydraulic characteristics of any valves used to control channel flowrates may have an important bearing on the critical channel power for the initiation of oscillations. The present investigation was therefore undertaken to determine the best model for two‐phase water‐steam pressure drop across such a valve. Pressures were between 300 and 1000 psig, mass fluxes between 0.1 and 0.5 × 106 lb m/hr‐ft2 and qualities up to 64%. The measurements were made in the FLARE rig of Atomic Energy of Canada Ltd. by one author during the course of a doctoral study on boiling instabilities. Various pressure‐drop models were tried. It was found that for turbulent flow a homogeneous model was the best.
The gaussian distribution of θ1/3 — a two‐parameter statistical model for approximating RTD's in CSTR's
Authors: Roy Paul‐H. , Choquette Pierre
Published: March 2009

The normal or Gaussian distribution of Θ1/3 is shown to give a satisfactory approximation of RTD's in continuous‐flow stirred tanks, whether mixing is ideal or not, and its mean Θm1/3 and standard deviation σ are, in each case, determined from the F‐curve as a function of Θ1/3 on linear probability paper.

For ideal mixing, Θm1/3 and σ approach respectively the values of 0.89 and 0.32. In this case, the approximation is considered satisfactory for values of the relative time Θ ranging from 0.05, for F = 0.01, to 9.21, for F = 0.9999.

As mixing conditions depart more and more for ideality, Θm1/3 assumes progressively lower values than 0.89 whilst the values of σ are all greater than 0.32. For a wide range of non‐ideal mixing conditions, the same approximation is satisfactory for values of Θ ranging from 0.125 to 5.0 and even up to 8.5 in some cases.
Théorie et application de la distribution normale de θ1/3 aux temps de séjour des fluides dans les réservoirs agités en régime continu
Authors: Roy Paul‐H. , Martinet J.‐P.
Published: March 2009

Les modèles statistiques qui décrivent la distribution des temps de séjour dans une cascade de réservoirs de même volume et parfaitement agités se ramànent à une distribution normale de θ1/2, θ1/2, et θ selon que le nombre de réservoirs est respectivement > 15, > 50 ou trés grand.

Pour un seul réservoir, la distribution normale de θ1/2 est une approximation satisfaisante de la distribution des temps de séjour pour l'agitation parfaite ou imparfaite. Pour l'agitation parfaite, la moyenne xm et l'écart type σ de la distribution de θ1/2 prennent des valeurs respectives de 8/9 et 1/3. Si l'agitation est imparfaite, xm et σ sont respectivement < 8/9 et > 1/3.

Enfin, la distribution de θ1/3 permet la définition d'un critère simple de l'efficacité de l'agitation tout en étant conforme aux notions de Danckwerts.
Simulation of the oxidative dehydrogenation of methanol
Authors: Ulinder John D. , Tollefson Eric L.
Published: March 2009

The selective air oxidation of methanol over a 96.6% silver ‐3.4% copper catalyst supported on α‐alumina was studied to determine whether by supplying heat from an external source the extent of the dehydrogenation reaction to formaldehyde could be increased relative to the oxidative dehydrogenation route. Preheated reactants were fed over the catalyst which was held in place between glass wool plugs within a 0.16 inch I.D. quartz U‐tube. The latter was suspended in an electrically heated bath of fluidized alumina used to maintain constant temperature. Product analyses were made by gas chromatography using a Porapak N column. A mathematical model was designed to simulate the observed results. The results show that with the catalyst employed the addition of heat to supply the requirements of the dehydrogenation reaction and to decrease the extent of the oxidative reaction is not favorable in terms of formaldehyde production efficiency.
Some general considerations of reversible chemical reactions in batch and tubular reactors
Authors: Varma Arvind , Amundson Neal R.
Published: March 2009

The possibility of change in the algebraic sign of the net reaction rate of a single reversible reaction occurring in adiabatic or non‐adibatic batch and tubular reactors is investigated. This change is shown not to occur for adiabatic reactors; it may depending on the operating conditions and the system parameters for non‐adiabatic reactors. These and the related aspects of approach to system equilibrium are analyzed by an examination of the mathematical models describing these chemical reactors. Important results are summarized throughout the paper as Conclusions 1 ‐ 10. The results have direct applications in reactor design and operation. From a practical point of view it means that yield may be reduced in some cases by allowing too long a residence time even for a single reaction. Numerical examples are given to illustrate the results.
Kinetics of oxidation of pseudocumene in the vapor phase
Authors: Balasubramanian S. , Viswanath D. S.
Published: March 2009

The kinetics of pseudocumene oxidation in the vapor phase with tin vanadate as catalyst have been studied over the following ranges of the variables: Oxygen concentration, 0.909 to 2.857 mole/m3; pseudocumene concentration, 0.071 to 0.125 mole/m3; temperature, 260 to 320°C; space time, 22.5 to 90 × 104 g. catalyst/mole sec. Oxidation‐reduction models have been found to describe the kinetics adequately. The mechanism is found to remain the same throughout the temperature range covered.
Cracking of a dewaxed and extracted neutral distillate over La‐Y catalyst
Authors: Pachovsky Roman A. , Wojciechowski Bohdan W.
Published: March 2009

A four parameter conversion model based on the time on stream theory of catalyst decay is applied to experimental data on the cracking of an extracted and dewaxed neutral distillate over La‐Y catalyst. It is found that in this system the decay exponent is very large indicating that m, the order of the decay reaction, is unity. Based on this finding, an exponential decay function has also been fitted to the data and it is found to give an equally satisfactory fit. It is also found that the value for the parameter W which describes the refractoriness of the feed is very high for this system, making the use of the refractoriness function unavoidable. The unusual behaviour observed here allows interesting comparison to be drawn between this system and that of Mid Continent Gas Oil over REHX catalyst. This in turn makes it clear that a) “standard” catalyst tests can be seriously misleading and b) that the behaviour of a feed‐catalyst system can not be properly described by any one simple concept such as “activity” or “refractoriness” but must take into account a number of parameters simultaneously.
New method of view factor calculation in radiative transfer
Authors: Kolenda Zygmunt , Malec Marian
Published: March 2009

The method of view factor calculation presented in this article is based on the methods of analytical geometry. The given method can be used when the surfaces are separated by non‐absorbing gas and radiation from the surfaces, whether emitted or reflected, is diffused.
Jet break‐up in liquid‐liquid systems
Authors: Skelland A. H. P. , Johnson K. R.
Published: March 2009

A study was made of the jet length, jet contraction, and size of drops resulting from the formation and break‐up of liquid jets in another Newtonian, immiscible liquid. Drop size and jet contraction were correlated with system parameters, but attempts to correlate the jet length proved unsuccessful. Data were obtained from measurements of 4202 drops and 294 jet lengths and diameters on 294 photographs representing 92 runs. Variables included nozzle size, flow rate, and physical properties from six Newtonian liquid‐liquid systems.
Wettability control of glass beads
Authors: Singhal A. K. , Dranchuk P. M.
Published: March 2009

Wettability plays an important role in a number of industrial applications. Often it becomes desirable to control contact angles (wettability). For this purpose, two techniques for altering the contact angles of glass beads are described. These involve chemisorption of Silicones or Hexamethyldisilazane (HMDS) on glass surfaces.

The results of measured contact angles on treated glass beads indicate that by carefully controlling the treating procedure, it is possible to obtain the desired wettability.
Dynamic behavior of reciprocating‐plate columns
Authors: Landau J. , Dim A. , Shemilt L. W.
Published: March 2009

The unsteady‐state behaviour of a reciprocating plate column in which adjacent plates move out of phase with each other has been studied experimentally by determining responses to step changes.

The one‐dimensional, two‐parameter model developed, leading to a system of differential equations with time‐dependent coefficients, was simplified to allow parameter estimation in the Laplace domain. Special features of the experimental technique for obtaining instantaneous values of the tracer concentration which closely approximate to the average for a column cross section are described; the limitations of parameter estimation in the Laplace domain are discussed.
Heat transfer from a grid jet in a large fluidized bed
Authors: Behie L. A. , Bergougnou M. A. , Baker C. G. J.
Published: March 2009

Heat transfer from a vertical grid jet within a 2 ft diameter and 4 ft deep fluidized bed of cracking catalyst was studied. The test nozzle diameter was varied from ¼ to 1 in. and the nozzle velocity from 50 to 250 ft /sec which is within the range of industrial practice. The axial temperature data have been related to a Froude, a Reynolds and a Nozzle number:

In (δT/δTo) = –58.1 Fr−0.562 No1.08 Re−0.112

A simple jet quenching model yielded heat transfer coefficients between the fluid bed and grid jet which ranged from 300 to 1200 Btu/ft2 hr.o F.
Hydrodynamic studies in natural and forced convection electrowinning cells
Authors: Gendron A. S. , Ettel V. A.
Published: March 2009

Horizontal and vertical mapping of the cathode mass transfer coefficient was used to compare the hydrodynamics of full height model electrowinning cells employing either natural convection or two methods of forced convection. The most sgnificant improvement in performance was achieved with uniform agitation resulting from sparging gas over the cathode surface.
Sorption characteristics of binary hydrocarbon mixtures in low density polyethylene
Authors: Ghosh S. K. , Rawat B. S. , Krishna M. G.
Published: March 2009

Sorptions of six pure hydrocarbons and five of their binary mixtures in low density polyethylene have been measured. Composition of the binary mixture sorbed has been determined experimentally by a direct method. Selectivity due to sorption has been shown to constitute a major portion of the permselectivity.

Correlations have been developed to predict the quantity and composition of the binary mixture sorbed in the polymer at any temperature, when the pure compound sorptions at some temperature are known.
SO2/O2 dehydrogenation of ethylbenzene
Authors: Gaspar N. J. , Cohen A. D. , Vadekar M. , Pasternak I. S.
Published: March 2009

In the SO2 dehydrogenation of ethylbenzene to styrene using alkalized alumina or titania catalysts, addition of small amounts of oxygen results in (1) higher styrene yields at equivalent SO2 concentrations, or (2) equivalent styrene yields with lower SO2 requirements. By staging the oxygen additions, styrene yields of greater than 80% are achieved at SO2 levels as low as 0.15 mole/mole ethylbenzene when 0.45 mole O2 is added in increments of 0.15 mole. The low SO2 concentration and staging of the oxygen result in a high selectivity (94%) for the reaction to styrene by minimizing both byproduct formation and combustion.
Experimental studies of single droplet liquid extraction with chemical reaction
Authors: Wellek R. M. , Rrunson R. J.
Published: March 2009

Experimental data were obtained for the diffusion of a solute from the continuous phase into droplets falling in a single streani though a simple spray extractor. The solute reacted inside the dispersed phase by means of a second‐order reaction. The high droplet Reynolds numbers encountered necessitated the use of modifications of film and penetration approaches to arrive at methods for predicting single droplet extraction with reaction. The evaluation of the interfacial concentration was a special problem in this study.
A comparison of transient reactor models for non‐catalytic gas‐solid processing
Authors: Sampath B. S. , Ramachandran P. A. , Hughes R.
Published: March 2009

Transient behaviour of packed bed reactors for non‐catalytic gas‐solid reactions has been simulated using the sharp interface, finite reaction zone and the particle‐pellet model for the reaction process occurring within the individual pellets. The solution procedures to the system of equations is based on the orthogonal collocation method. The effect of perturbations in the reactor inlet conditions on the temperature profiles encountered in the bed has also been examined.
Diffusivité de l'acide benzoi'que dans l'eau: Influence de la température
Authors: Lozar J. , Laguerie C. , Couderc J. P.
Published: March 2009

Benzoic acid diffusivity in water has been determined using the diaphragm cell method, with a flexible and thin “Millipore” filter that leads to a reduction in the time of experiment. Twenty‐two experimental data points are given in the range 10–50°C. Two different correlations are proposed.
Removal of micron‐size particles from gases by turbulent deposition and diffusiophoresis
Authors: Azarniouch M. K. , Farkas E. J. , Cooke N. E. , Bobkowicz A. J.
Published: March 2009

When one gaseous or vapour component diffuses across a space occupied by another component, there is a tendency to entrain and remove particles in the micron size range suspended in that space. This phenomena is called diffusiophoresis. The object of this work was to study the application of this phenomenon as a means of air pollution control when pollutant particles are suspended in a gas stream in turbulent flow. Under these conditions turbulent deposition also results in removal of particles from the gas stream. The test system chosen for study was sulfuric acid droplets suspended in air, with water vapour as the diffusing component. A concentration gradient was established by passing the mixture through a vertical tube whose walls were cooled. Experimental particle collection efficiencies agreed with efficiencies calculated from a theoretical model of the system. The energy requirement of this pollution control technique was analyzed.
The rate of mass transfer at a rotating cylindrical electrode with wiper blades
Authors: Nadebaum P. R. , Fahidy T. Z.
Published: March 2009

A theoretical analysis of mass transfer at a rotating cylindrical electrode with wiper blades yields the dimensionless equation

where w is the number of the symmetrically located wiper blades, d is the wiper blade thickness and R1 is the radius of the wiped electrode. NuR, ReR and Sc are defined in terms of the cell and electrolyte parameters. Experimental evidence via the reduction of oxygen and ferrocyanide ions indicates that mass transfer rates can thus be predicted at no more than ±5% inaccuracy for Sc>200. The two‐wiper blade system is shown to effect an increase in mass transfer rates by a factor of 7‐8 with respect to a rotating cylindrical electrode without wiper blades.
Slurry and trickle‐bed reactor effectiveness
Authors: Sylvester N. D. , Kulkarni A. A. , Carberry J. J.
Published: March 2009

Overall slurry and trickle‐bed reactor effectiveness with respect to mass transport limitation upon linear kinetics is readily assessed by utilization of estimated parameters and data secured in a single experiment. A judicious estimate of certain other physical parameters permits an estimate of the intrinsic chemical reaction rate coefficient. The procedure is illustrated with literature data.
A technique for analysing integral rate data in non‐ideal flow reactors to estimate unknown parameters
Authors: Cresswell D. L. , Quon D.
Published: March 2009

A technique is described for analysing integral rate data taken from a non‐ideal flow chemical reactor characterised by the axial dispersion model, using a weighted residual approach.

This approach avoids the formidable computational difficulties involved with the solution of the boundary value problem associated with the model differential equations. The measured concentration profile is approximated by a series of orthogonal polynomials. Model parameters are estimated by specifying that the fitting polynomial satisfy certain moment relations derived from the mass balance equation and boundary conditions.

If the form of the rate equation is known, a priori, the estimation of the rate constant and the dispersion coefficient becomes explicit. In the more general case, in which the reaction order is also unknown, the estimation problem reduces to a uni‐dimensional search for the reaction order parameter (or the adsorption parameter in the case of complex kinetics). The method is applied to both linear and non‐linear systems and conclusions are drawn regarding the sensitivity of the chemical kinetic and transport parameters to experimental error.
Gas absorption in vertical slug flow
Authors: Golding J. A. , Mah C. C.
Published: March 2009

An investigation has been made of gas absorption characteristics in unstable vertical slug flow. The process studied was the absorption of hexane from an inert carrier gas into paraffin oil. Gas‐phase properties were varied by use of nitrogen, helium and Freon‐14 as carriers, while variation of liquid‐phase properties was achieved by using light and heavy paraffin oils and their mixtures. Absorption efficiencies were high, ranging from 0.75 to 0.99 The values depended not only on operating and system variables, but also on absorber geometry with a distinct discontinuity being observed when the overall mass transfer efficiency was plotted against absorber length H. This discontinuity was particularly marked for the heavy paraffin oil and was found to be related to the variation of slug surface area with H. Flow rates and system properties were found to affect the mass transfer coefficients and a comparison of experimental values with those predicted by the penetration theory suggested that not all the slug surface area was effective in mass transfer.
Improvement of mass transfer coefficient in reverse osmosis by oscillatory flow
Authors: Thayer W. L. , Pageau Lucien , Sourirajan S.
Published: March 2009

This paper describes a laboratory apparatus for confined feed liquid reverse osmosis operation. In this apparatus, the mass transfer coefficient on the high pressure side of the membrane is increased by sweeping the membrane surface at a predetermined frequency by a back and forth movement of the feed liquid itself through an adjustable narrow channel in the cell. The utility of the technique for improving membrane performance is illustrated.
A generalised approach to the fluid dynamics of particulate systems part 2: Sedimentation and fluidisation of clouds of spherical liquid drops
Authors: Barnea E. , Mizrahi J.
Published: March 2009

In a recently published paper(1), it has been demonstrated that the drag coefficient—Reynolds number relationship for a single spherical solid particle may be applied to multi‐particle systems as well, provided that modified definitions of the drag coefficient and Reynolds number incorporating suitable functions of the particles volume fraction are used.

This generalised approach is now extended to include the case of a fluid dispersed phase. This done by incorporating a function of the ratio of the phase viscosities, based on theoretical derivations due to Hadamard—Rybczinski and Taylor in the modified definition of Reynolds number.

All available experimental data (88 points from 3 sources, on 12 different liquid‐liquid systems) were recalculated and correlated on this basis.
Absorption with first order chemical reaction into turbulently flowing liquids
Authors: Stepanek J. B. , Achwal S. K.
Published: March 2009

The damped turbulence model has been applied to the problem of absorption with a first order chemical reaction through a gas‐liquid interface into a turbulently flowing liquid. An analytical solution has been obtained in terms of Gauss hypergeometric functions. A further investigation has shown that the solution is fairly insensitive to the boundary condition inside the liquid phase. A simpler solution has also been obtained with a negligible loss of accuracy.
Synthesis of optimal process flowsheets by an infeasible decomposition technique in the presence of functional non‐convexities
Authors: Stephanopoulos George , Westerberg Arthur W.
Published: March 2009

An infeasible decomposition method based on the two‐level optimization procedure is proposed for the structural parameter method for synthesis of optimal process flowsheets. A penalty term is used to guarantee the success of the method in the presence of functional non‐convexities very often encountered in chemical process design. The convergence characteristics of the primal and dual problems have been considered and a computational procedure which will enhance the convergence rates for both problems is proposed. The use of the suggested strategy is illustrated in the synthesis of a simple reactor‐separator system.
The effect of line length for inclined slurry pipelines at shutdown
Authors: Shook C. A. , Mcleod D. J.
Published: March 2009

The behaviour of inclined slurry pipelines at shutdown was studied using different active lengths of pipe. The ultimate settled condition was found to depend on pipe slope in the same fashion as for much shorter pipes. Pressure changes observed at the bottom of the slope gave a good indication of the time scale of the settling/flow process. A preliminary interpretation of the process is provided by a model in which inertial forces, compressibility effects and axial variations of velocities are neglected.
Radial liquid distribution in cocurrent two‐phase downflow in packed beds
Authors: Sylvester Nicholas D. , Pitayagulsarn Punya
Published: March 2009

Radial liquid distribution was measured experimentally for cocurrent, two‐phase downflow in packed beds. The effects of bed length, water and air flow rates, and type of packing were determined. The experimental data were obtained in the gas‐continuous, transition and pulsing trickling‐flow regimes. For all finite air rates, the liquid velocity profiles were approximately flat with the maximum average velocity occurring at the center of the packed column. Increasing the air rate increased the center liquid velocity. The gas rate effect was more pronounced in shorter beds. At higher gas rates the liquid rate had less effect on the radial liquid distribution than at lower gas rates. Operation at higher liquid rates resulted in a flatter radial liquid veilocity profile. It was observed that the bed of pellets operated at high liquid rate and low gas rate was unstable. Increasing the bed height increased the stability of the system and a better liquid distribution was obtained. The effects of water flow rate, bed length, and packing type on the shape of the liquid velocity profiles were minor.
A study of the combined effects of kinetic parameters and flow models on conversions for second order reactions
Authors: Lindfors Lars‐Eric
Published: March 2009

The present paper is a study of the interplay between kinetic parameters and different flow patterns and its effect on fractional conversions for second order reactions with arbitrary stoichiometry and arbitrary ratios between the initial concentrations of the reactants. The models studied are the normal, segregated and maximum‐mixed axial dispersion and tanks‐in‐series models. The calculations required have been performed with the aid of digital simulation and the results are presented in diagrams making possible the determination of the fractional conversion for ten different models.

When plotted as a function of a reaction rate group the absolute value of the difference between the conversions for the normal and segregated models always attains its highest value for the limiting model represented by complete backmixing, while this difference is zero for the opposite limiting model, i.e. plug flow. In the case of maximum‐mixed and normal models this difference attains its highest value between plug flow and complete backmixing, but the exact value is dependent on other parameter values. The diagrams indicate that it is more important to choose the proper model for certain parameter combinations than for others: the maximum difference between the conversions for different models is about 8%; the lowest is zero.
Effects of charge stock composition on selectivity in the cracking of neutral distillates
Authors: Pachovsky Roman A. , Wojciechowski Bohdan W.
Published: March 2009

Gasoline selectivity in the catalytic cracking of four neutral distillates, varying only in wax content, has been studied over a range of temperatures. It has been found that the cracking rate constants leading to gasoline and to undesirable products, as well as the gasoline recracking rate constant, increase linearly with the mole fraction of wax in the feed. At the same time the activation energies for the primary rate constants decrease with increasing wax content of the feed, while the activation energy for gasoline recracking is not affected by feed composition.

We also find that the various components of the feed crack quite independently of one another and do not interact in any way. There appears to be no synergistic interactions between the wax‐free fraction and the wax in the feed.

In spite of the large difference between reaction rate constants reported here and those previously reported for the cracking of a mid‐continent gas oil by Pachovsky and Wojciechowski16, the Optimum Performance Envelopes for all the chargestocks we have studied are very similar. Our results indicate that the major differences between gas oils we have studied lie in their “reactivity”; in other words, in their relative rates of conversion at a given set of conditions.
On fluidized bed‐to‐surface heat transfer
Authors: Zabrodsky S. S. , Antonishin N. V. , Parnas A. L.
Published: March 2009

Development of new techniques has stimulated new interest in fluidized bed‐to‐surface heat transfer phenomena. In this paper a short critical review of major recent works on the subject as well as comments on the validity of some general concepts and of “small scale” equations available are presented. It appears that these concepts can serve as a basis for future development of reliable design equations for large commercial equipment and for analysis of its performance. Examples of the analysis of imperfectly understood observations are presented.
The measurement and prediction of temperatures at the free interface of falling water films under heat transfer
Authors: Borodin A. S. , Picot J. J. C.
Published: March 2009

This paper describes an experimental measurement of temperatures at the free liquid interface of distilled water films falling vertically downwards on the outside surface of a copper tube heated internally by a countercurrent circulating liquid. An infrared radiometer was used for the temperature measurements. A prediction for these temperatures is made by solving numerically the governing equations of momentum, continuity and energy. Experimentally estimated temperature profiles were employed as the wall temperature boundary conditions. Internal turbulence eddies and surface wave celerity were considered in the numerical solution by using the eddy diffusivity profile of Mills and Chung. Good agreement between experiment and theory was obtained
Effect of axial dispersion on interphase mass transfer in packed absorption columns
Authors: Mathur V. K. , Wellek R. M.
Published: March 2009

Gas phase axial mixing parameters and interphase mass transfer coefficients were determined simultaneously for gas‐liquid flow in a packed column. It was found that axial mixing in the gas phase increases with increases in liquid flow rate, packing size, and packing height. The behavior of apparent and true mass transfer coefficients indicates a decrease in axial mixing with increases in gas flow rates. Gas phase Peclet numbers obtained were about two to three times greater than reported than reported by workers using transient tracer techniques under similar conditions. Correlations for apparent and true overall liquid phase mass transfer coefficients are presented.
Analytical approximate solutions for simultaneous absorption with reaction
Authors: Sada Eizo , Kumazawa Hidehiro , Butt M. A.
Published: March 2009

An analytical approximate solution for simultaneous absorption of two reacting gases into an inert liquid is presented assuming a non‐linear concentration profile for gaseous species A. The approximate enhancement factors of A and B show a closer agreement with the exact enhancement factors on the basis of film theory than do those in any existing paper. The same suggested concentration profile is successfully applied to the problems of simultaneous absorption of two reacting gases in a reactive liquid and of three reacting gases in an inert liquid.
Hydrodynamic study of gas and solid flow through a screen‐packing
Authors: Claus G. , Vergnes F. , Goff P. Le
Published: March 2009

Many drawbacks of conventional gas fluidized beds can be avoided by filling the column with a fixed wire‐screen Raschig ring packing of high voidage. Such systems have been studied in batch and countercurrent continuous mode. Excellent fluidization occurs with relatively coarse particles but not with smaller particles. In batch systems, the expansion is given by a Capes and McIlhinney type power law and the contribution of the packing to support the bed can be up 20 percent of the weight of solid. In countercurrent systems, for each gas velocity two operating points can occur: the dilute or the dense phase bed in the same way as for gas liquid flow. All increases in the flow of the solid or in the dilution of the bed lead the packing to support a greater part of the grains.