bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the precipitation of silver bromide photographic emulsions
Authors: Margolis Geoffrey , Gutoff Edgar B.
Published: June 2004

Nucleation and crystal growth processes involved in the batch precipitation of photographic emulsions by the addition of silver nitrate to an aqueous solution of bromide and gelatin have been reasonably successfully modeled. Simulation predicts the known increase in average crystal size with increased addition time, with increased temperature, and with increased halide levels. Solubility is related to crystal size by the Gibbs‐Thomson equation. The predicted decrease in the number of crystals during the course of precipitation is similar to published data, but there are quantitative differences. The model is very sensitive to variations in the constant in the growth equation, but not to variations in the constants in the nucleation equation.
Synthesis strategies for multicomponent separation systems with energy integration
Authors: Rathore Ram N. S. , Van Wormer Kenneth A. , Powers Gary J.
Published: June 2004

The problem of synthesizing an optimal multicomponent separation system which is energy integrated is solved by a combined decomposition and dynamic programming technique.

Dynamic programming is an optimization technique which allows the solution by decomposition of a multistage or serial optimization problem. Whenever the special serial structure is absent, again decomposition can be tried, but in this case it is by no means obvious how to decompose effectively the given problem into subproblems. In this paper the nonserial problem of synthesizing an energy integrated separation system is solved by decomposing the original problem so that a serial structure results.
Ignition on catalytic wires: Kinetic parameter determination by the heated‐wire technique
Authors: Rader C. G. , Weller S. W.
Published: June 2004

A new analysis is presented for the extraction of Arrhenius parameters from experimental measurements of ignition temperatures during catalytic oxidation over electrically‐heated metal wires. Butane oxidation on high purity platinum wires has yielded reproducible experimental results for the reaction rate and has provided consistent estimates of the Arrhenius parameters. First‐order kinetics was assumed. The present treatment contains explicit consideration of: (1) the ohmic heating term; and (2) the end conduction heat loss from the catalytic wire. The effects of wire length, diameter, and configuration are reconciled when the ignition phenomenon is refferred to the center‐point temperature of the wire.
Sorption and diffusivity characteristics of acid‐leached mordenites
Authors: Satterfield Charles N. , Chiu George T.
Published: June 2004

The apparent diffusivity for the binary liquid systems benzene‐cumene and cyclohexane‐cumene in H‐mordenite crystals at 25°C to 44°C was increased by an order of magnitude or more after the zeolite was acid‐leached to increase the silica‐alumina mole ratio from the range of 14 to 18 to the range of 70 to 89. The calculated diffusivities, which range from 10−12 to 10−16 cm2/s, decrease with approach to sorption equilibrium and may be markedly reduced under some circumstances by adsorption of molecules from the bulk liquid, causing blockage of pores.

Comparison of sorption capacities as a function of silica‐alumina ratio as reported by various investigators indicates that considerable differences exist in the properties of acid‐leached mordenites of the same silica‐alumina ratio but of different origins.
Stabilizing effects of surfactants on pseudoplastic falling films
Authors: Skelland A. H. P. , Popadic Vujadin O.
Published: June 2004

The effects of nonionic surfactants on thin‐film flow of pseudoplastic non‐Newtonian liquids down a smooth vertical plate have been studied experimentally. For all liquids examined there was a surfactant concentration at which the stabilizing action of surfactants was maximized. Comparison with experimental data showed that an existing equation, developed for the stabilizing action of surfactants on thin‐film flow of Newtonian fluids, may be used to predict the effect of surfactants on the stability of pseudoplastic thin‐film flow by using the zero‐shear rate apparent viscosity in place of the Newtonian viscosity.
Influence of crystal size on the rate of contact nucleation in stirred‐tank crystallizers
Authors: Bauer L. G. , Rousseau R. W. , McCabe W. L.
Published: June 2004

The purpose of this study was to investigate the influence of seed crystal size on the rate of nucleation in batch stirred‐tank crystallizers. Experimental results confirm the existence of such an effect. Nucleation rate data are correlated with a second‐order polynomial in seed crystal size; coefficients of the correlation are functions of the solute‐solvent system, crystallizer geometry, and mixing conditions. The empirical correlation is incorporated into a population balance model for determining the nucleation rate in multi‐seed crystallizers. The observed results are explained in terms of variations in impact energy, circulation frequency, and target efficiency.
Adsorption and kinetics in a batch heterogeneous catalytic reactor
Authors: Hsu Stephen M. , Kabel Robert L.
Published: June 2004

The utility of a new dynamic experimental technique is illustrated for the specific case of the vapor phase dehydration of ethanol over a hydrogen ion exchange resin. Adsorbed phase composition data are obtained simultaneously with complete vapor phase information, providing new insight into the catalytic behavior. A mathematical model, based upon Langmuir‐Hinshelwood kinetics, comprises simply five first‐order ordinary differential equations. The model describes all of the important transient and equilibrium characteristics of the reacting system qualitatively and most quantitatively. Experimental data alone are used to show that the surface reaction is the rate controlling step.
Application of quasilinearization to methane pyrolysis
Authors: Denis Gilles H. , Daubert Thomas E.
Published: June 2004

The rate constants appearing in differential equations derived from proposed mechanisms for methane pyrolysis were estimated from published integral conversion data. Quasilinearization, capable of fitting the differential equation solutions directly to the integral data and therefore not requiring differentiation or transformations, was used. Since differential equations representing free radical reactions have coefficients varying over many orders of magnitude, implicit numerical integration was used to obtain the numerous particular and homogeneous solutions required in the execution of the algorithm. Convergence was achieved by replacing the concentrations after each iteration with values near the solution at that point and by repeatedly estimating a small number of parameters in a cyclic manner in order to improve starting estimates of all parameters simultaneously. The mechanisms attempted were considered plausible when they led to adequate data fits and reasonable rate constant estimates. The major contribution of the work is that the algorithm is capable of testing a mechanistic model over a relatively wide range of conditions with minimal experimental data.
Mechanisms of brine‐side mass transfer in a horizontal reverse osmosis tubular membrane
Authors: Derzansky Lewis J. , Gill William N.
Published: June 2004

The desalination performance of a tubular reverse osmosis membrane was studied under well‐defined hydrodynamic conditions. Experimental measurements were made of local mass transfer rates in a 2.31‐cm I.D. × 81‐cm long horizontal cellulose acetate membrane at 16 locations along the tube length for both laminar and turbulent flows. The membrane's intrinsic permeability to water and NaCl was found to vary significantly along its productive length.

The experiments suggest that the dominant transport mechanisms in laminar flow are forced convection in the upstream region and combined free and forced convection in the downstream region, beyond a distance of approximately 16 tube diameters, for all feed concentrations studied. The Deissler analogy applies well to the turbulent region for Re ≧ 104; however, it increasingly overpredicts performance as Re is decreased below 104.

The experimental results of other workers are interpreted successfully in terms of the mechanisms deduced in the present work.
Regulation of lumped periodic processes
Authors: Liaw J.‐S. , Bailey J. E.
Published: June 2004

When a periodic process is disturbed, control action may be necessary to maintain satisfactory performance. Regulating controls to achieve this objective can be synthesized by solving a linear‐quadratic optimization problem with periodic coefficient's. Generalized proportional and proportional‐integral feedback regulators developed in this manner are tested by simulating a cyclic reactor. Very satisfactory control is achieved for 10% step disturbances in reactor feed conditions although the results are sensitive to the choice of manipulated variables.
Mechanisms of secondary nucleation in agitated crystallizers
Authors: Evans T. W. , Margolis G. , Sarofim A. F.
Published: June 2004

Experiments were designed to identify the mechanism of the secondary nucleation of ice in a vigorously agitated crystallizer. It has been shown that the nucleation rate is proportional to the product of two factors, one characterizing crystal morphology and the other the rate of removal of potential nuclei from the surfaces of the existing crystals. Consequently, the nucleation rate attributable to different mechanisms is additive and the rate is proportional to the number of collisions per crystal. The contribution to the secondary nucleation of ice, by collisions of crystals with the impeller, baffles, and other crystals in an agitated crystallizer have been identified by measurements in a batch crystallizer in which each of the different collision mechanisms could be suppressed.
Three‐dimensional flow of fluids through nonuinform packed beds
Authors: Stanek V. , Szekely J.
Published: June 2004

Through the statement of the Ergun equation in a vectorial form, a formulation is presented for three‐dimensional flow of fluids through packed beds having a spatially variable resistance to flow. The equations were put in a form convenient for numerical solution by successive over‐relaxation, and a selection of computed results is presented for cylindrical beds where the nonuniform resistance to flow obeys axial symmetry. The method outlined in the paper for calculating flow maldistribution in packed beds is thought to be a necessary first step in the representation of hot spot formation and flow nonuniformities in packed bed reactors.
Minimum cost design of a multimodal fluidized reactor‐heater system involving an exponential function inside an integral equation
Authors: Wilde Douglass J.
Published: June 2004

A simple procedure for achieving the minimum cost design of a single reaction fluidized reactor system with feed and recycle heaters is presented and proven. The problem's mathematical interest stems from its multimodality, the handling of the exponential dependence of temperature, and the presence of an integral equation constraint. The proof technique is an extension of Lagrange's method, supplemented by ideas from geometric programming, extended to exponential and the integral functions.
Gas phase axial mixing at extremely high irrigation rates in a large packed absorption tower
Authors: Woodburn Edward T.
Published: June 2004

Extensive gas phase dispersion data are reported for extremely high liquid‐gas ratios in a cylindrical packed absorption tower operated at atmospheric pressure under counterflow conditions.

The dispersion data report gas Peclet numbers in terms of superficial liquid and gas Reynolds numbers over the range

An increase in Peclet number with increasing gas rate is observed at subloading conditions.

Reverse gas flow was observed in the gas phase when the liquid Reynolds number exceeded 650. Dispersion in the gas phase at liquid rates for which NReL < 650 is consistent with previously recorded correlations but becomes independent of further increases of liquid rate when NReL is > 650.

The dispersion coefficients obtained by dynamic testing under reverse gas flow conditions were consistent with those obtained from steady state absorption profiles and provide a quantitative explanation for the anomalies in plug‐flow KLa at high water rates recorded by Sherwood and Holloway (1940).
Model reduction and the design of reduced‐order control laws
Authors: Wilson Robert G. , Fisher D. Grant , Seborg Dale E.
Published: June 2004

This paper is concerned with the problem of designing satisfactory loworder (incomplete state feedback) controllers starting with a high‐order, state‐space model. Two design approaches are considered: the control law reduction technique, recently developed by the authors (Wilson et al., 1973), and the well‐known model reduction approach. These two design techniques are used to develop a variety of low‐order controllers for a double‐effect evaporator starting with a 10th‐order model. Experimental and simulated response data from the computer‐controlled evaporator demonstrate the superiority of the control law reduction approach in this application. It is also shown that several of the previously published modal approaches to model reduction are basically equivalent since they yield identical reduced‐order models.
Modified one‐at‐a‐time optimization
Authors: Findley M. E.
Published: June 2004

An optimization method has been developed that searches one variable at a time under the conditions that previously searched variables are at their approximate optimum and variables to be searched later are constant. This method provides the optimum and also information on the effects of the variables. The method is based on the Partan and Powell methods and on assuming linear partial derivatives of the objective function with respect to any given variable. The procedure involves searching each variable separately with other variables either constant or varied so that they remain at their estimated optimum for the given conditions. This method provides useful information on the effects of independent variables as well as locating the overall optimum and a number of partial optimums and requires a comparable number of trials.
Convective instabilities in concurrent two‐phase flow: Part II. Global stability
Authors: Gumerman Raymond J. , Homsy George M.
Published: June 2004

The method of energy is used to determine global stability limits for thermally stratified two‐phase plane Couette flow. Instabilities due to surface tension variations, buoyancy effects, and shear are allowed for, but surface waves are specifically excluded from consideration. Under these assumptions, the Marangoni, Rayleigh, and Reynolds numbers completely describe the system. Stability plots, valid for disturbances of any magnitude, are presented for both streamwise oriented roll vortices and two‐dimensional transversely oriented disturbances. It is shown that rolls are the most dangerous disturbances in the sense that they cannot be shown to be stable relative to transverse disturbances at any nonzero Reynolds numbers. Comparisons are made with existing linear limits, and these are seen to be close only for moderate Reynolds numbers.
Oscillating behavior on distillation trays‐II
Authors: Biddulph Michael W.
Published: June 2004

This paper describes an extension of an earlier study on oscillations which can develop on distillation trays. The oscillations take the form of violent lateral movements of the gas/liquid biphase, and they are generally undesirable for good column performance. It has been found that lower density gases need higher velocities to initiate oscillation, and vice versa for higher densities. The predictive method for the onset of oscillations proposed previously appears to remain valid for the range of gas density covered, and for small hole size trays. The presence of oscillations has been shown to increase weeping significantly.
Thermodynamic consistency using orthogonal collocation or computation of equilibrium vapor compositions at high pressures
Authors: Christiansen Lars J. , Fredenslund Aage
Published: June 2004

The numerical method of orthogonal collocation is used within a thermodynamically consistent framework to calculate equilibrium vapor compositions from P‐T‐x data for binary systems. The method may be used for isothermal or isobaric data in both the normal liquid and in the critical region, and it applies to any choice of standard states.

To use the method it is necessary to have experimental or estimated values of vapor phase fugacity coefficients for both components in the mixture and liquid molar volumes (isothermal case) or heats of mixing (isobaric case). If vapor composition data are available, each set of P‐T‐x‐y data may be checked for thermodynamic consistency by comparing y (experimental) with y (calculated). Illustrative calculations are given. The method is shown to provide an excellent procedure for obtaining Henry's constants from P‐x data for systems with one noncondensable component.
Vapor‐liquid equilibrium: Part IV. Reduction of P‐x data for ternary systems
Authors: Abbott M. M. , Floess J. K. , Walsh G. E. , Van Ness H. C.
Published: June 2004

Total pressure measurements taken for the ternay systems acetone‐chloroform‐methanol and chloroform‐ethanol‐n‐heptane at 50°C are reduced by Barker's method and correlated by an equation similar to one proposed by Wohl (1953).
Flexible solutions to linear programs under uncertainty: Inequality constraints
Authors: Friedman Y. , Reklaitis G. V.
Published: June 2004

In most industrial applications the linear model used for optimization by linear programming involves significant uncertainties and inaccuracies in the model parameters. This paper presents a framework which allows uncertainties in the matrix elements of the linear program to be taken into account without requiring detailed knowledge of the statistical characterstics of these uncertainties. Three cases for the inequality constrained problem are considered: independent variations in the array elements, column dependent variations, and row dependent variations. In each case the problem can still be solved as a linear program. In the first two cases, the problem size is doubled, while for the row dependent case a finitely terminating cutting plane algorithm is constructed.
Thermal effects in gas absorption
Authors: Verma Surjit L. , DeLancey George B.
Published: June 2004

The transformation of the energy equation from the mass average to the volume average reference frame exposes a pseudo Dufour effect. The theoretical model for absorption into a stagnant liquid including this effect, the heat of absorption, variable density, an interfacial velocity, and an arbitrary equilibrium condition at the interface is able to predict experimental data over a wide range of conditions. The data consisted of liquid temperature profiles and mass transfer rates into a stagnant liquid. The ammonia‐water system exhibited interfacial temperature rises from 6.9°K to 18.2°K. The interfacial temperature rise for the propane‐decane system was 1.3°K. Simpler theoretical models were able to predict the mass transfer rates or the temperature profiles.
Statistical thermodynamics of liquid mixtures: A new expression for the excess Gibbs energy of partly or completely miscible systems
Authors: Abrams Denis S. , Prausnitz John M.
Published: June 2004

To obtain a semi‐theoretical equation for the excess Gibbs energy of a liquid mixture, Guggenheim's quasi‐chemical analysis is generalized through introduction of the local area fraction as the primary concentration variable. The resulting universal quasi‐chemical (UNIQUAC) equation uses only two adjustable parameters per binary. Extension to multicomponent systems requires no ternary (or higher) parameters.

The UNIQUAC equation gives good representation of both vapor‐liquid and liquid‐liquid equilibria for binary and multicomponent mixtures containing a variety of nonelectrolyte components such as hydrocarbons, ketones, esters, amines, alcohols, nitriles, etc., and water. When well‐defined simplifying assumptions are introduced into the generalized quasi‐chemical treatment, the UNIQUAC equation reduces to any one of several well‐known equations for the excess Gibbs energy, including the Wilson, Margules, van Laar, and NRTL equations.

The effects of molecular size and shape are introduced through structural parameters obtained from pure‐component data and through use of Staverman's combinatorial entropy as a boundary condition for athermal mixtures. The UNIQUAC equation, therefore, is applicable also to polymer solutions.
Selection of decompositions for chemical process simulation
Authors: Upadhye Ravindra S. , Grens Edward A.
Published: June 2004

A method has been developed for selection of the set of torn streams in a process simulation that leads to convergence of a direct substitution calculation in the minimum number of iterations. It is based on the establishment of families of decompositions, the members of each of which have identical convergence behavior. Explicit criteria for choice among families have been found that lead, in almost every case, to a single optimum decomposition family. These results have been verified by application to several chemical process simulation examples.
Prediction of unsymmetric convention liquid‐phase activity coefficients of hydrogen and methane
Authors: Brelvi S. Waseem , O'Connell John P.
Published: June 2004

A corresponding states method has been developed to predict the binary parameter in the unsymmetric‐convention one‐term Margules relation for binary activity coefficients of H2 and CH4 in solvents. In addition to the solvent density, only characteristic volumes used previously for partial molar volumes at infinite dilution and pure solvent compressibility are required. Comparisons with experiment for nonpolar solvents indicate that use of the method is usually significantly more accurate than assuming ideal solution (Henry's law).
An investigation of anomalous osmosis and thermoosmosis
Authors: Goldstein W. E. , Verhoff F. H.
Published: June 2004

Measurements of water flux, solute flux, and electrochemical potential were made simultaneously in a membrane transport system designed for the studies in anomalous osmosis and thermoosmosis using a series of cations with a common anion. The cation exchange membrane employed was dimensionally stable. The anomalous osmosis appeared to be composed of two components, the normal osmosis and a facilitated osmosis; whereas the thermoosmosis was composed solely of a facilitated component. The anomalous water flux did not correlate with the solute flux or the electro‐chemical potential. Anomalous osmosis depended strongly upon the cation species.
Dielectric constants and Clausius‐Mossotti functions for simple liquid mixtures: Systems containing nitrogen, argon and light hydrocarbons
Authors: Pan W. P. , Mady M. H. , Miller R. C.
Published: June 2004

Dielectric constants and Clausius‐Mossotti functions (CM) have been determined for selected pure components, binary mixtures, and ternary mixtures at temperatures between 91 and 115 K and pressures near saturation. Excess Clausius‐Mossotti functions (CME) have been calculated from the pure fluid and mixture values.

Mixture CME values are found to be generally less than 0.1% of the mixture CM values for systems containing only nonpolar species. Thus, dielectric constant measurements can be conveniently used as substitute density measurements for simple liquid mixtures. Methods have been developed to utilize dielectric constant measurements to accurately determine densities and heating values per unit liquid volume for liquefied natural gas mixtures.
New network permeability model of porous media
Authors: Dullien Francis A. L.
Published: June 2004

In this study a new mathematical model for predicting permeabilities of porous media has been developed. The model consists of a set of cubic networks of arbitrary orientations with respect to the macroscopic flow direction. The networks consist of capillary tubes which are made up of segments of different diameters. It is shown that a cubic network of capillaries has isotropic permeability properties. The permeability model requires two pore size distributions and the porosity of the sample for the calculations. The calculated permeabilities agreed with experimental results for a wide range of permeabilities of highly compacted materials to within ± 23%, without using adjustable tortuosity factors.
Multicomponent distillation simulation — distillation of air
Authors: Biddulph Michael W.
Published: June 2004

This paper describes the application of a mathematical model to a column distilling air to produce nitrogen, oxygen, and argon. The upper column of a plant producing 400 tonnes/day (400 Mg/day) of oxygen is considered. Apart from any direct interest in this system, the outcome illustrates the problems which arise in the study of the separation of multicomponent systems. The effect of directed flow compared with normal flow is established, and in particular the way in which some components benefit more than others. The simulation uses experimental values of point efficiency and mixing measurements, and a good comparison with plant experience is achieved.
Freeze dehydration by microwave energy: Part I. Theoretical investigation
Authors: Ma Yi Hua , Peltre Philippe R.
Published: June 2004

A general unsteady state analysis is employed to derive a mathematical model of a freeze‐drying process using microwave heating. The model takes into account the variations of the transport and dielectric properties in the sample with both time and location as a function of temperature and pressure. The variations of the properties are described by functionals which have been derived from literature data and are built into the model.

The mathematical model is used to simulate the freeze drying of beef meat with microwave energy at 2450 MHz. The simulation shows that drying rates are essentially a function of the microwave power input. The model also shows that the total pressure and the partial pressure of water vapor in the vacuum chamber directly affect the sample temperature during dehydration. The simulation shows, in particular, that, an optimal microwave freeze‐drying operation corresponds to an operation near corona and overheating/melting conditions.
A new method for nonlinearly constrained optimization
Authors: Newell J. S. , Himmelblau D. M.
Published: June 2004

A new penalty function method of solving problems involving a nonlinear objective function subject to nonlinear equality and inequality constraints is described. It ameliorates difficulties experienced with the illconditioning of the Hessian matrix of classical penalty function methods. Experience based on the solution of 25 test problems indicates the proposed method is as good as, or better, than methods that are now being used.
General analysis for free drainage of non‐Newtonian films from flat plates when inertial and surface tension forces and normal stresses are negligible
Authors: Pendergrass John
Published: June 2004

General equations for (1) thickness, (2) specific holdup, and (3) specific flow rate of non‐Newtonian films under conditions of plane free drainage with negligible inertial and interfacial tension forces and normal stresses as functions of position and time are derived. Use of these equations reduces the heretofore tedious process of derivation for a particular rheological model of expressions for film thickness, holdup, and flow rate to a single‐step operation for film thickness and relatively simple processes for holdup and flow rate. The general equations are evaluated for popular non‐Newtonian models, with description of efficient methods for doing so, and the results for thickness, holdup, and flow rate, many new, in compact dimensionless form made available to the interested reader in a supplement.
Effects of nonseparable kinetics in alcohol dehydration over poisoned silica‐alumina
Authors: Bakshi K. R. , Gavalas G. R.
Published: June 2004

Methanol and ethanol dehydration over fresh and poisoned silica‐alumina have been used as a model system to demonstrate experimentally certain effects of nonseparable kinetics including the change in product distribution upon flow reversal in a reactor with a poisoning gradient. The rate expression r = kKACA1/2/(1 + KACA1/2 + KWCW) describes the epxerimental data for all reactions although the constants for ether and olefin formation are entirely different and vary between fresh and poisoned catalysts. The nonseparability of kinetics and the concomitant variation of KA, KW with poisoning are briefly discussed in terms of interactions between poison molecules and surface acid‐base sites.
Effectiveness factors in gas‐liquid reactions
Authors: Kulkarni B. D. , Doraiswamy L. K.
Published: June 2004

The concept of the effectiveness, factor, commonly used as a means of accounting for diffusional effects in gas‐solid catalytic and noncatalytic reactions, is extended to gas‐liquid reactions. The relevant differential equations for an isothermal system with appropriate boundary conditions are solved for the case of (1) a simple first‐order irreversible reaction, (2) a consecutive reaction, and (3) a parallel reaction. The results are presented in terms of effectiveness factor plots, and methods of delineating the controlling regimes are discussed. It is shown that gas‐liquid reactions represent perhaps the most general case which reduces to gas‐solid reactions under appropriate limiting conditions.
Gas absorption accompanied by instantaneous bimolecular reaction in turbulent liquids
Authors: Méndez Francisco , Sandall Orville C.
Published: June 2004

Gas absorption accompanied by instantaneous bimolecular reaction in turbulent liquids (Re > 1200) is treated in terms of an eddy diffusion model. The species balance equations are integrated for the eddy diffusivity varying as the square of the distance from the free surface. Experimental mass transfer coefficients were measured in a wetted‐wall column for the absorption of carbon dioxide in aqueous sodium hydroxide solutions. Experimental results were obtained for carbon dioxide partial pressures of 1.0 and 1.5 atm. and for sodium hydroxide concentrations varying between 0.020 and 0.220 N over the Reynolds number range 1400 to 5400. The experimental data showed good agreement with the theoretical calculations, the mean deviation being 8.2%.
Limits of superheat and explosive boiling of light hydrocarbons, halocarbons, and hydrocarbon mixtures
Authors: Porteous William , Blander Milton
Published: June 2004

The limits of superheat of thirteen light hydrocarbons and four light halocarbons were experimentally measured at one atmosphere using a superheating column. While there was some variation in the number of degrees to which a compound could be superheated before boiling explosively, in all cases the reduced limits TL/Tc were close to 0.88. The measured superheat limits of three binary hydrocarbon systems and several ternary mixtures were close to mole fraction averages of the limits of the pure components. The results of both pure components and mixtures paralleled predictions of Beegle (1973), based on thermodynamic stability theory. Limits of pure components agreed closely with limits predicted from homogeneous nucleation theory.
Optimal decomposition of process networks
Authors: Genna Peter L. , Motard R. L.
Published: June 2004

The tearing or decomposition of recycle process networks is extended to include the enumeration of alternate cut sets or tear stream sets. The optimality criterion is the response to convergence acceleration in the quasi‐Newton sense and an algorithm is proposed to select the optimum cut set adaptively as the recycle computation proceeds.
Sulfur dioxide oxidation in slurries of activated carbon. Part I. Kinetics
Authors: Komiyama Hiroshi , Smith J. M.
Published: June 2004

Dynamic adsorption and reaction studies were made for the catalytic oxidation of sulfur dioxide in aqueous slurries of activated carbon at room temperature and atmospheric pressure. For the small particles (dp = 0.03 mm) of carbon used, mass transfer resistances were of minor importance so that the data could be analyzed in terms of the kinetics of the chemical reaction. Quantitative evaluation of mass transfer effects, including intraparticle diffusion, is presented in Part II.

The rate was first order in oxygen concentration in the liquid and zero order with respect to SO2. The rate decreased with increasing H2SO4 concentration in the liquid. This was explained by the decrease in solubility of oxygen in the solution rather than by a change in reaction rate constant. The adsorption and rate data together suggest that the controlling step in the mechanism is the adsorption of oxygen on active sites of the carbon surface. The low concentration of oxygen in water (due to its low solubility) reduces its rate of adsorption.
Continuous production of polystyrene in a tubular reactor: Part I
Authors: Wallis J. P. A. , Ritter R. A. , Andre H.
Published: June 2004

An experimental analysis of the bulk polymerization of styrene initiated by azobisisobutyronitrile was carried out in a tubular reactor.

The experiments performed in a 2.362‐cm I.D., 6‐meter long jacketed reactor showed that: (1) it was feasible for a tubular reactor to produce acceptable quality polystyrene for industrial purposes; (2) the quality of the polymer product was reproducible at any time; (3) it was technically feasible for the tubular reactor to replace the stirred‐batch kettles as the preliminary stage in the polystyrene manufacturing process, and (4) radial temperature gradients were not a problem for reactor operation.
Trickle‐bed reactor performance. Part I. Holdup and mass transfer effects
Authors: Goto Shigeo , Smith J. M.
Published: June 2004

Liquid holdup and mass transfer rates were measured in a 2.58‐cm I.D. tube, packed with glass beads and granular CuO · ZnO catalyst or β‐naphthol particles, and operated as a trickle bed. Gas‐to‐liquid (water) transport coefficients were determined from absorption and desorption experiments with oxygen at 25°C and 1 atm. Liquid‐to‐particle mass transfer was studied using β‐naphthol particles.

Holdup and both mass transfer coefficients were unaffected by gas flow rate but increased with liquid rate. The data were correlated with equations that could be used for predicting mass transfer coefficients at high temperatures and pressures for use in the reaction studies reported in Part II.
Trickle‐bed reactor performance. Part II. Reaction studies
Authors: Goto Shiego , Smith J. M.
Published: June 2004

Dilute solutions (132 ppm) of formic acid in water were oxidized with air in a trickle‐bed reactor at 212° to 240°C and 40 atm. Particles 0.291 and 0.0541 cm in diameter, prepared from a commercial CuO · ZnO catalyst, were used to provide a model system for studying water purification by catalytic oxidation.

Differential reactor runs were made to measure the global rate of reaction. These data were compared with predicted rates from the known intrinsic kinetics and intraparticle diffusivities, and the mass transfer coefficients measured in Part I.

High conversion (of formic acid) data were also obtained in order to test models for trickle‐bed reactors. Experimental conversions agreed reasonably well (within 10%) with predicted values based upon intrinsic kinetics and the several transport rates. Axial dispersion was found to be less important than gas‐to‐liquid mass transfer and intraparticle diffusion. In our laboratory studies (reactor I.D. = 1 in.) careful arrangements were made to obtain nearly uniform distribution of liquid over the reactor cross section. Hence effects of maldistribution, which may be important in large‐scale reactors, were minimized.
Stresses and friction force in moving packed beds
Authors: Grossman Gershon
Published: June 2004

A model to determine stresses and friction forces in moving packed beds with interstitial fluid flow has been developed. The scaling parameters are determined from the governing equations. A plane and an axisymmetric bed geometry are studied and the wall stress calculated under uniform one‐dimensional axial flow conditions. The effect of added transverse flow (for example, due to a screen in the wall) is investigated. The present model is an improvement over earlier, one‐dimensional models with capability to include in the stress analysis varying pressure gradients in all directions which may exist in practical moving bed systems.
Diffusion and reaction in turbulent flow of a power‐law fluid in a circular tube
Authors: Mohan V. , Raghuraman J. , Wasan D. T.
Published: June 2004

Simultaneous diffusion and homogeneous reaction during the turbulent flow of a power‐law fluid in a tubular reactor has been studied using the correlations for the velocity profile and eddy diffusivity proposed by Krantz and Wasan. The results of the theory indicate that while the cup‐mixing concentration is unaffected by variations in the Reynolds number, the Schmidt number, or the flow behavior index, it is significantly influenced by the reaction parameter and the reaction order.
Mechanics of steady spinning of a viscoelastic liquid
Authors: Denn Morton M. , Petrie Christopher J. S. , Avenas Pierre
Published: June 2004

The equations for steady isothermal spinning of a viscoelastic liquid are solved for a fluid model with constant modulus and a single constant relaxation time. High stress levels are predicted for elastic liquids, and the velocity approaches a linear profile in the limit of maximum drawdown. These predictions are in accordance with the observed behavior of polymeric liquids in isothermal spinning. Relaxation times computed from spinning data of Spearot and Metzner and Acierno et al. for four low density polyethylene melts are comparable to those measured rheogoniometrically, though the spinning relaxation times are 20 to 80% larger.
Ecokinetics: A study of the fate and distribution of chemicals in laboratory ecosystems
Authors: Blau G. E. , Neely W. B. , Branson D. R.
Published: June 2004

The anticipated kinetic behavior of different amounts or forms of a chemical in the environment can be studied by introducing the chemical into a laboratory ecosystem, collecting samples of the different components of the system at various times, and obtaining a sequence of concentrations of the chemical and/or its metabolites. Conventional compartmental models can be used to characterize this concentration‐time data in order to better predict the distribution and ultimate fate of a chemical introduced into the environment, to provide a quantitative measure for helping assess the environmental impact of different chemicals, and to reduce the cost of expensive laboratory testing and field work.
A Deborah number for diffusion in polymer‐solvent systems
Authors: Vrentas J. S. , Jarzebski C. M. , Duda J. L.
Published: June 2004

A Deborah number is introduced as a means of characterizing diffusional transport in amorphous polymer‐solvent systems. Two types of temperature‐penetrant concentration diagrams are constructed, and the various regions on these figures are identified by their Deborah number values. The utility of the diffusion Deborah number is demonstrated by using this dimensionless group to anticipate conditions under which thickness anomalies can be expected in sorption experiments for the atactic polystyrenepentane system.
Phase separation of primary dispersions in beds packed with spherical packings
Authors: Wilkinson David , Mumford C. J. , Jeffreys G. V.
Published: June 2004

Studies have been made of the behavior of drops in primary dispersions flowing through beds packed with glass ballotini in order to establish the mechanism of phase separation. The buoyancy and surface forces have been analyzed in terms of drop size and shape in the interstice in the packing and the physical properties of the dispersion. A mathematical model has been developed to describe drop behavior in the bed, and the drop size in the effluent dispersion has been predicted from established correlations.
Self‐generated oscillations in continuous crystallizers: Part I. Analytical prediction of the oscillating output
Authors: Yu K. M. , Douglas J. M.
Published: June 2004

The theory of nonlinear oscillations should provide a useful tool for studying both forced and self‐generated oscillations in continuous crystallizers. The application of the theory is described in this paper for the case of self‐generated oscillations in a MSMPR (mixed‐suspension, mixed product removal) isothermal crystallizer. Although the process parameters do not correspond to typical industrial conditions, the results indicate that for the Class I system studied higher yields sometimes can be obtained from the periodic process than the steady state design. Thus, there may be some situations where oscillatory operation is advantageous.
Flow phenomena in stirred tanks. Part II. The bulk of the tank
Authors: Günkel Alfred A. , Weber Martin E.
Published: June 2004

Turbulence parameters were measured in the bulk of turbulent stirred tanks of 45.7 and 91.4 cm diameter with air as the working fluid. Three types of turbine impellers were studied ranging in diameter from 22.8 to 45.7 cm. The turbulence in the bulk of the tank was essentially homogeneous and isotropic. The normalized one‐dimensional energy spectra and the Eulerian autocorrelation functions were approximately the same throughout the tank and for all tanks, impellers, and operating conditions. The space averaged turbulent velocities were correlated by using the turbulent energy equation. A transformation of the measured spectra from the frequency space to the wave number space was accomplished. Integration of the dissipation spectra in the wave number space confirmed that most of the energy input is dissipated in the bulk of the tank through the turbulent motion. The results were extended to low viscosity liquid systems and used to interpret the data on mass transfer from suspended particles.
Model discrimination and parameter estimation in heterogeneous catalysis
Authors: Froment G. F.
Published: June 2004

After a brief discussion of the experimental aspects of a kinetic investigation, the paper reviews the methodology of kinetic analysis, for both single and complex reactions. The necessity of statistical testing of the results is emphasized. Special attention is given to methods for estimating parameters in algebraic and differential equations. Sequential methods for the design of an experimental program aiming at optimal discrimination between rival models and optimal parameter estimation are reviewed and illustrated by means of practical examples.
Flooding rates and holdup in packed liquid‐liquid extraction columns
Authors: Watson J. S. , McNeese L. E. , Day John , Carroad P. A.
Published: June 2004

Countercurrent flow of liquids in columns packed with Raschig rings was studied with fluids having a wide range of physical properties. These results, along with data reported previously from other studies, were used to develop a correlation for predicting flooding rates in packed columns that is significantly better than previous correlations. Dispersed phase holdup in packed columns can be estimated over a wide range of flow rates or flow ratio by assuming a constant slip velocity between the two phases which is dependent on the properties of the fluids and packing used. Although the slip velocity is thus essentially constant at flow rates below flooding, the flooding rate correlation indicates that this term is not necessarily constant at flooding conditions.
Pyridine hydrodenitrogenation: An equilibrium limitation on the formation of piperidine intermediate
Authors: Satterfield Charles N. , Cocchetto Joseph F.
Published: June 2004

Equilibration between pyridine and piperidine, the first product formed in the overall series of hydrodenitrogenation (HDN) reactions of pyridine, can be a rate‐limiting factor under some conditions. Thus, on a commercial NiMo/Al2O3 catalyst at 11 bars pressure, a maximum in the pyridine HDN rate occurs at about 400°C, caused by a thermodynamic limitation on the allowable concentration of piperidine. From studies with pyridine and with piperidine, NiMo/Al2O3 appears to have greater hydrogenation‐dehydrogenation activity than CoMo/Al2O3 but CoMo/Al2O3 appears to have greater hydrogenolysis activity than NiMo/Al2O3, at least at about 300°C and below.
Benzoin‐ and benzoin methyl ether‐sensitized photopolymerization of styrene and methyl methacrylate: Quantum yields and mixing effects
Authors: Mendiratta S. K. , Felder R. M. , Hill F. B.
Published: June 2004

Styrene and methyl methacrylate have been polymerized in a batch photoreactor using two sensitizers–benzoin (C6H5COCHOHC6H5) and benzoin methyl ether (C6H5COCHOCH3C6H5)–and light with a peak intensity at 366 nm. Primary quantum yields have been calculated for each monomer‐sensitizer combination. Effects of mixing on the rate of polymerization and product molecular weight distribution have been determined and correlated with a two‐region reactor model.
Perturbed hard‐chain theory: An equation of state for fluids containing small or large molecules
Authors: Beret Samil , Prausnitz J. M.
Published: June 2004

Generalized van der Waals theory is used to establish a partition function that considers the effect of density on rotational and vibrational motions in addition to translational degrees of freedom. A three‐parameter equation of state is derived from this partition function. The equation of state is applicable to small, spherical (argon‐like) molecules and also to large, structurally complex molecules, including polymers. Parameters are presented for three polymers and twenty‐two common fluids including light hydrocarbons, heavy hydrocarbons, nitrogen, carbon dioxide, hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, and water. The equation of state gives good liquid densities, and vapor pressures, and fair second virial coefficients.
The decomposition kinetics of molybdenite in an argon plasma
Authors: Munz R. J. , Gauvin W. H.
Published: June 2004

A reactor system was developed for the study of heterogeneous reaction kinetics in plasma tail flames. This system was used to investigate the thermal decomposition kinetics of stationary particles of molybdenum disulfide in both the molten and solid state when exposed to argon flames in the temperature range 3 000°K to 8 000°K.

In the solid state a shrinking‐core reaction model was obeyed. The rate of reaction was largely controlled by the diffusion of sulfur vapor outwards through the product layer. An apparent activation energy of 134 kcal/mole was calculated for the particle temperature range 1 613° to 1 833°K The molten state reaction was controlled by the rate of heat transfer to the reacting particle. Calculations indicated that the rate of heat transfer was influenced by the efflux of sulfur.
A coordinate‐transformation method for the numerical solution of nonlinear minimum‐time control problems
Authors: Kwon Young D. , Evans Lawrence B.
Published: June 2004

A new method is presented for the numerical solution of nonlinear minimum‐time control problems where at least one of the state variables is monotone. A coordinate transformation converts the problem with fixed end point and free end time to one of free end point and fixed end time. The transformed problem can be solved efficiently by the use of the gradient method with penalty functions to force the system to achieve target values of state variables. Application of the method is illustrated by the synthesis of a minimum‐time temperature path for the thermally initiated bulk polymerization of styrene.
Cis‐1,4 polymerization of butadiene initiated by CoCl2 · 4C5 H5 N‐(C2 H5)2 AlCl
Authors: Hsu C. C. , Ng L.
Published: June 2004

The effect of catalyst composition on the polymerization of butadiene initiated by CoCl2 · 4Py‐Et2AlCl‐H2O in a batch reactor has been studied. It was found that the polymerization is first order with respect to monomer and cobalt concentrations, and both the deactivation of catalyst and the chain transfer reaction have great influence in conversion as well as molecular weight. A general conversion model was proposed, and it fits the experimental data well.