bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of nickel sulfate in a laboratory‐scale fluidized‐bed crystallizer
Authors: Phillips V. Roger , Epstein Norman
Published: June 2004

Growth and dissolution rates of nickel sulfate α‐hexahydrate were measured as functions of the concentration driving force in a laboratory‐scale fluidized‐bed crystallizer for the temperature range 35° to 50°C and the crystal size range 0.5 to 4.0 mm.

Dissolution rates at a given temperature and crystal size were first order in the concentration driving force. Growth rates were about one‐quarter of dissolution rates and depended on a higher exponent (around 1.3) of the concentration driving force. This exponent was not significantly affected by variations in crystal size, but decreased as temperature increased. The apparent variation of growth rate itself with crystal size at constant temperature was slight. Growth rates were found to be insensitive to solids concentration.
Surface diffusion of stearic acid on aluminum oxide
Authors: Yang Ralph T. , Fenn John B. , Haller Gary L.
Published: June 2004

By means of infrared internal reflection spectroscopy we measured the time dependence of the surface concentration of stearic acid molecules over a well defined region of the surface. The molecules were diffusing into this region from a source comprising a compressed monolayer or bulk crystalline material outside the field of view. By these measurements in conjunction with solutions to the diffusion equations we determined the diffusion coefficient Ds of stearic acid on the (0001) plane of α‐alumina. We also determined the dependence of Ds upon the amount of water coadsorbed on the surface. When the surface was free of reversibly adsorbed water, Ds had a value of about 2 × 10−7 cm2/s. As the surface coverage of coadsorbed water increased to about a monolayer Ds increased to a maximum value of about 4 × 10−5 cm2/s. With further additions of surface water Ds then decreased and became less than 10−8 cm2/s at coverages slightly less than about two monolayers. In the region of its maximum value the temperature dependence of Ds indicated an activation energy for the diffusion process of about 26 kcal/mole.
Single‐phase chromatography: Solute retardation by ultrafiltration and electrophoresis
Authors: Lee H.‐L. , Reis J. F. G. , Dohner John , Lightfoot E. N.
Published: June 2004

It is suggested that chromatographic separations can be performed very effectively in the absence of a stationary sorbent phase by using small diameter tubes or tube bundles for the column and segregating the solutes radially into the slower moving fluid near the tube walls. Separation is achieved by differential solute retardation whenever the degree of segregation is different for the various solute species present.

An approximate analysis and preliminary experimental studies demonstrate the feasibility of using ultrafiltration through the tube wall to achieve solute separation. Preliminary estimates based on our ultrafiltration analysis also show that segregation by electromigration is very promising for electrically charged solutes.
Laboratory reactors and their limitations
Authors: Weekman Vern W.
Published: June 2004

Choosing the type of laboratory reactor for evaluating process kinetics may be the most crucial step in an industrial process development program. Not only would a wrong choice result in expensive delays, but data may be obtained which would scale‐up erroneously, leading to a disastrous commercial design. Some of the pitfalls and limitations of various laboratory reactors are discussed for some typically complex industrial reaction systems. A modus operandi is suggested for choosing from among the potential reactors those that have the best chance of supplying the desired data. As is typical of many complex industrial reaction systems, no one reactor turns out to be ideal and many times the building of two or more types is advantageous.
Determination of the kinetics of secondary nucleation in batch crystallizers
Authors: Kane S. G. , Evans T. W. , Brian P. L. T. , Sarofim A. F.
Published: June 2004

The kinetics of secondary nucleation have been determined from measurement of the supersaturation as a function of time following the addition of seed nuclei to a supercooled solution in a well‐stirred batch crystallizer. Population balance mathematics have been used to show that the secondary nucleation kinetics may be inferred from the supersaturation‐time curve. The method has been applied to the determination of the kinetics of the secondary nucleation of ice and found to give results in excellent agreement with those obtained from tedious particle counts. In addition, it has been shown that the moment of the particle size distribution that best correlates the nucleation rate data can be inferred from the initial transient of the supersaturation‐time history.
Mass transfer in laminar flow between parallel permeable plates
Authors: Walker Gary , Davies Terence
Published: June 2004

Solutions for the concentration profiles and mass transfer rates are found for various wall Sherwood numbers. Use is made of the confluent hypergeometric function in the solution, and its advantage over the previously used series solution is pointed out. Perturbation solutions are also presented for both large and small values of the wall Sherwood number.
Trajectory calculation of particle deposition in deep bed filtration: Part I. Model formulation
Authors: Payatakes Alkiviades C. , Tien Chi , Turian Raffi M.
Published: June 2004

The packed bed model developed by Payatakes, Tien, and Turian (1973a, 1973b) is used as a basis for the study of particle deposition in deep bed filtration. The size of the particulate matters present in the suspension is assumed to be sufficiently large for Brownian motion to be negligible, but small enough for straining to be unimportant. The prediction of the rate of particle deposition is based on the one‐step trajectory approach. The collector is represented by a unit bed element of the porous media model and the particle trajectory equation is formulated to include the gravitational force, the hydrodynamic force and torque (including the correction for the presence of the unit cell wall), the London force (including the retardation effect, which is shown to be of primary importance under conditions usually met in deep bed filtration systems), and the electrokinetic force. Sample capture trajectories, including the limiting capture trajectories, are given.

Based on the limiting trajectories and the assumption of uniform particle distribution at the entrance of each unit cell, the number fractions (of suspended particles) impacted on each unit cell are determined and then used to calculate the fraction impacted on the entire unit collector and also the value of the filter coefficient for a clean bed. It is also shown how the capture trajectory calculation can be used to determine the local rate of deposition along the wall of a given unit cell.
Bisphenol a synthesis: Kinetics of the phenol‐acetone condensation reaction catalyzed by sulfonic acid resin
Authors: Reinicker R. A. , Gates B. C.
Published: June 2004

The industrially important reaction of phenol and acetone to give bisphenol A and water was catalyzed by beads of ion‐exchange resin (sulfonated styrene‐divinylbenzene copolymer) suspended in a batch reactor containing liquid reactants. The data are summarized by a rate equation accounting for reaction in the resin competitively swollen by water, acetone, phenol, and methylcyclohexane.

The catalyst is modeled as two phases, each in equilibrium with the liquid: a polar phase consisting of sulfonic acid groups with hydrogeb–nonded acetone and water and a nonpolar phase consisting of the hydrocarbon matrix swollen with organic components. The rate determining step is the electrophilic attack on phenol in the nonpolar phase by a carbonium ion intermediate in the polar phase.

Resin cross‐linked with 4% divinylbenzene initially catalyzed acetone conversion at a rate of 5 × 10−4 (moles)/(equiv of acid groups s) at 364°K. An 8% cross‐linked resin was much less active because the rigid polymer matrix was only slightly swollen by phenol, but a more highly cross‐linked resin with macropores and accessible internal surface catalyzed reaction almost as rapidly as the 4% cross‐linked catalyst.
Separations with protein liquid crystals
Authors: Kozinski A. A. , Kizior G. J. , Wax S. G.
Published: June 2004

A lyotropic protein liquid crystal was studied experimentally to evaluate its potential as a selective liquid membrane. Concentrated solutions of fibrinogen had nematic like properties under shear and exhibited graded selectivities toward solutes of widely differing sizes when subjected to a two‐dimensional velocity field. The magnitude of the selectivity differences was found to depend on the shear orientated direction of the liquid crystal layer. The selectivity seems to be both a solubility phenomena and a relative diffusion phenomena. These anisotropic layers may have potential as controlled variable selectivity membranes.
Surface diffusion in liquid‐filled pores
Authors: Komiyama Hiroshi , Smith J. M.
Published: June 2004

Surface diffusivities of benzaldehyde in liquid‐filled pores of Amberlite particles (polystyrene) were measured at 25°C using water as a solvent. For particles of different surface areas but chemically similar pore surfaces, the intrinsic surface diffusivity Ds' was about the same, but the relative importance of surface to pore‐volume diffusion increased with surface area. For a single type of particle, the adsorption capacity was decreased about twenty‐fold by adding up to 19 mole % methanol to the solvent. This was accompanied by an increase in Ds' from 1.2 × 10−8 to 1.2 × 10−7 cm2/s. These results were interpreted in terms of a two‐step theory for surface migration: (1) formation of a vacant site on the adsorbent surface followed by (2) movement of the adsorbate molecule into the site by breaking the surface‐adsorbate bond. The theory predicts that surface transport will be large when the surface area is high and that the Ds' will be large when the heat of adsorption is low, and when the bond between solvent molecules and the surface is weak.

In our studies the surface contribution to intraparticle transport was as much as 20 times the contribution due to pore‐volume diffusion. This ratio increases as the concentration of adsorbate in the liquid decreases.
On the optimization of distributed parameter systems with boundary control: A counter example for the maximum principle
Authors: Gruyaert F. , Crowe C. M.
Published: June 2004

A counterexample is given to the strong maximum principle for boundary control of a class of distributed parameter systems. The particular system deals with chemical reactors suffering catalyst decay and is in the class whose members are described by sets of first‐order partial differential equations of the hyperbolic type. It is shown that an optimal control exists and that over any finite time interval in which the control is unconstrained the exit conversion from the reactor remains constant. It is further shown that for certain values of the parameters the optimal control policy violates the necessary conditions of the strong maximum principle for boundary control of distributed parameter systems.
Synthesis of fault tolerant reaction paths
Authors: Powers Gary J. , Cummings Daniel L. , Rathore Ram N. S.
Published: June 2004

The problem of synthesizing an optimal low risk reaction network from unreliable reactions is formulated. An expected cost criterion function for decision‐making is derived both for the case of a continuously operating network of reactions and for the case of reaction paths that involve batch reactions. It is shown that in general the decision space has a nonserial structure and the search for the optimal path will involve use of network search methods. An example is given where the optimal reaction path is synthesized for deoxyribonucleic acid. This example demonstrates the decision‐making strategy for a class of bath reaction systems.
Mass transfer studies across liquid/liquid interfaces (use of an analytical ultracentrifuge)
Authors: Chandrasekhar Sivam , Hoelscher Harold E.
Published: June 2004

Experimental data have been obtained using an Analytical Ultracentrifuge, in regions much closer to the interface in immiscible liquid/liquid systems than have hitherto been reported. The water/toluene system was investigated with acetic and propionic acids as the transfer solutes. The direction of mass transfer was from the water to the toluene phase. The data derived from the study indicates that the maximum mass transfer flux in the water/toluene system occurs, not at the interface, but at regions further away from it and that the water/toluene system offers significant interfacial resistance of about 104 s/cm to the transfer of acetic and propionic acids. The water/n‐butanol system was also studied and found to offer negligible resistance to the transfer of acetic acid across the interface.

Diffusion coefficients for ethylene glycol, glycerol, and n‐butanol in water were also determined with the Ultracentrifuge. The values derived in this study were reproducible to within 5% and were in close agreement with those derived from classical diffusion experiments.
Two kinds of self‐preserving size spectra of a cloud of particles
Authors: Pulvermacher B. , Ruckenstein E.
Published: June 2004

The population balances describing the time dependence of the size distribution can, under some conditions, be trasformed by means of a similarity transformation into an ordinary integro‐differential equation containing two instead of three variables. If there is compatibility between the transformed equation and the constraints given by the total mass conservation equation and the equation for the total number of particles, a self‐preserving spectrum of the first kind can be obtaiened. There are, however, many situations such as the sintering controlled aging of supported metal catalysts, coagulation of colloidal particles in laminar shear flow, and coagulation of colloidal particles in a turbulent flow when the particles are smaller than the size of the smallest eddy for which, although a similarity transformation is possible, the transformed equation has no solution because of incompatibility with the above mentioned constraints. A second kind of self‐preserving spectrum is suggested for these situations. The new variables are induced from a particular case for which an analytical result is available. A detailed presentation of the sintering controlled aging of supported metal catalysts is presented.
Wall mass transfer in laminar pulsatile flow in a tube
Authors: Patel Rutton D. , McFeeley John J. , Jolls Kenneth R.
Published: June 2004

Wall mass transfer was measured in fully developed pulsating laminar flow in a tube using the diffusion‐controlled electrode technique. The average Reynolds number, pulsating frequency and amplitude, and length of the mass transfer surface were the independent variables studied. The results are given in the form of the amplitude ratio and phase angle of the pulsating wall transfer rate. At lower frequencies the amplitude and phase were found to be correlated by the variable ωd2 Gz−2/3 in accordance with theory. At higher frequencies an empirical correlation with the variable ωd2 Gz−1/3(L/D)1/3 was found. While this may show some deficiency in the usual theoretical model, it is also possible that other causes such as nondevelopment of the flow are responsible. Time‐averaged transfer rates were found to be only slightly different from the corresponding steady flow transfer rates in the range of variables investigated.
Natural convection with mercury in a uniformly heated vertical channel during unstable laminar and transitional flow
Authors: Humphreys William W. , Welty James R.
Published: June 2004

Experimental heat transfer correlations were determined for natural convection in mercury in a uniformly heated vertical channel with width‐to‐height ratios varying from 0.25 to infinity (the single plate limit). Local modified Grashof numbers varied between 108 and 1011. Temperature and velocity profiles were obtained for these same channel configurations and local Grashof numbers. Instantaneous velocity plots indicate the range of conditions studied to proceed from unstable laminar flow well into the transition regime. Heat transfer results are in good agreement with earlier results reported for stable laminar flow which were limited to values of modified Grashof number less than 109.
Drag reduction in solid‐fluid systems
Authors: Radin I. , Zakin J. L. , Patterson G. K.
Published: June 2004

Pressure drop measurements were made on a variety of dilute solid‐liquid suspension systems in order to study the effects of particle shape and size, concentration, fluid viscosity, and tube diameter on friction factor. The central objective was to determine under what conditions drag reduction would occur.
Steady state chemical process simulation
Authors: Motard R. L. , Shacham M. , Rosen E. M.
Published: June 2004

In recent years process simulation by computer has become an accepted tool in the design and control of chemical processes, but there are still uncertainties and conflicting views about the real benefits relative to cost in both chemical industry and in education.

This article surveys the literature of the last three years, exploring the answers to the question: How has chemical process simulation by computer fulfilled expectations in industry and education and what are the major areas of research identifiable at this time?

It is concluded that process simulation remains a very dynamic field with a continuous expansion in the areas of application and in the number of users. New subjects requiring research are replacing older areas which have matured.
Quantitative overdesign of chemical processes
Authors: Freeman R. A. , Gaddy J. L.
Published: June 2004

Overdesign is applied to chemical processes to account for expected variations in the design data or design conditions. These variables must be treated quantitatively in order to design a process that is certain to perform adequately. Process dependability is introduced as a means of quantifying variable process behavior. Overdesign using the dependability criterion is a stochastic optimization problem. An example problem with three stochastic variables and two design variables is presented to illustrate these procedures.
The behavior of a power‐law fluid flowing through a sudden expansion. Part II. Experimental verification
Authors: Halmos A. L. , Boger D. V.
Published: June 2004

Experimental data are presented to verify the numerical model discussed in Part I. The experimental techniques employed for recovering flow patterns and for point velocity measurement are described and justified. The measured reattachment lengths, the recorded flow patterns, and the developing axial velocity field all show excellent agreement with the model predictions.
Sulfur dioxide oxidation in slurries of activated carbon. Part II. Mass transfer studies
Authors: Komiyama Hiroshi , Smith J. M.
Published: June 2004

Bubble‐to‐liquid, liquid‐to‐particle, and intraparticle mass transport effects were all found to be significant for some conditions in a three‐phase slurry reactor operated for the oxidation of SO2 at 25°C and 1 atm. In particular, intraparticle diffusion was important for particles as small as 99 microns (effectiveness factor = 0.45).

Effective diffusivities determined from reaction, desorption, and adsorption data for O2, H2SO4, and SO2 indicated that surface diffusion was appreciable for SO2 but not for oxygen. These results are consistent with the kinetic results in Part I which suggested that the rate‐controlling step was a chemisorption process for oxygen on the pore surface of the carbon particles.
Process reliability analysis
Authors: Henley Ernest J. , Gandhi Satish L.
Published: June 2004

This paper presents a unified approach for obtaining system reliability and availability parameters from block diagram representations of process systems. It starts with computer algorithms for obtaining the minimal paths in a system, then shows how this information can be combined with unit reliability data to obtain the overall system reliability, and the response of system reliability to changes in unit reliability (sensitivities). It then demonstrates how these sensitivities can be used to optimize the system reliability and availability by equipment redundancy. Extension of the methodology to the automated production of system fault trees as well as the mathematical relationship between fault trees and block diagrams are noted.
Continuous production of polystyrene in a tubular reactor: Part II
Authors: Wallis J. P. A. , Ritter R. A. , Andre H.
Published: June 2004

An analysis of the bulk polymerization of styrene by azobisisobutyronitrile in a tubular reactor was made. Rigorous models were developed and verified. A diffusion model gave predictions of molecular weights and conversions that were 2% higher on the average than the experimental values. Another model, a plug flow contraction of the diffusion model, predicted molecular weights and conversions that were 6% higher on the average than the experimental values.

The diffusion model showed that optimal conversions could be obtained by proper reactor operation. Tentative studies for optimal conversion with minimal molecular weight dispersion indicated the reactor should be operated at a wall temperature 5° to 10°C below that required for optimal conversion.
Interphase mass and heat transfer in pulsatile flow
Authors: McMichael W. J. , Hellums J. D.
Published: June 2004

A study on the effects of flow pulsations on interphase mass or heat transfer has been made. The situation corresponds to fully developed flow in a long conduit with a periodic pressure gradient at amplitudes which cause flow pulsations without flow reversal. It is shown that the basic three‐parameter formulation can be reduced to a one‐parameter problem in the boundary layer formulation. Solutions are developed over wide ranges of the parameters in both the basic and the boundary layer formulations.

The boundary approach gives accurate results over wide ranges of the parameters. Pulsations cause increases in the time‐averaged interphase flux at intermediate values of a composite frequency‐space variable. However, at small values of this variable the pulsations cause a decrease in the flux such that the overall space‐averaged flux is always decreased.
Kinetics of solid phase reactions
Authors: Ruckenstein E. , Vavanellos T.
Published: June 2004

The kinetics of isothermal transformations or decompositions of solids proceeding through nucleation and subsequent growth is treated in the spirit of Avrami, eliminating, however, some of the internal contradictions of his treatment. Universal solutions of the dimensionless integral equation are computed. The theory is extended to nonisothermal systems and the resulting integral equations are solved numerically for the adiabatic case. It is shown that two kinds of catastrophic behavior can occur: one is characterized by slopes approaching infinity in the conversion vs. time curve following a long period of quiescent behavior; the other is characterized by a very short time for total conversion and by milder slopes in the conversion vs. time curve throughout the course of reaction. In the first kind the nucleation is mainly responsible for the catastrophic behavior, while in the second kind the rate of growth is responsible.
Oxygen reduction at an anodically activated platinum rotating disk electrode
Authors: Forbes Melvin , Lynn Scott
Published: June 2004

The reduction of oxygen in neutral saline solution and in seawater was studied using the rotating disk electrode (RDE). The objective was to test the applicability of the RDE as a primary reference standard for the measurement of oxygen concentrations below 0.1 ppm in seawater. Limited success was achieved with an activated platinum electrode. A gold electrode was less effective. If one postulates that the 2‐electron reduction of oxygen at an activated RDE is rapid, it appears that little or no 4‐electron reduction occurs and that the subsequent 2‐electron reduction or catalytic decomposition of hydrogen peroxide is relatively slow. The anodic activation procedure developed appears to impart a transient catalytic activity to the electrode surface for the peroxide reaction(s).
Flow maldistribution in packed beds: A comparison of measurements with predictions
Authors: Szekely J. , Poveromo J. J.
Published: June 2004

Experimental measurements are reported on flow maldistribution in packed beds containing side streams and deliberately created spatially nonuniform resistance to flow. The actual experimental technique involved the determination of the velocity field of the gas stream exiting the column through the use of a hot wire anemometer. The experimental measurements were compared with predictions based on the numerical solution of the differential vectorial form of the Ergun equation and reasonable agreement was obtained. Both the measurements and the analysis confirmed the existence of preferential flow in the vicinity of the walls even for uniformly packed beds.
Catalytic activity and selectivity on heterogeneous surfaces with mass transfer
Authors: Loffler Daniel G. , Schmidt Lanny D.
Published: June 2004

Effective reaction rates and selectivities on surfaces having active and inactive regions are calculated for systems in which diffusion of reactants and products through a boundary layer is significant. With a single reaction it is shown that rates are larger than those calculated assuming area weighted averages. The selectivity of production of an intermediate in a series of reactions on a heterogeneous surface is higher than on a homogeneous surface, and with parallel reactions selectivities may be lower or higher depending on the kinetics of the competing reaction.

Numerical examples from NH3 oxidation on a Pt gauze and CO oxidation in the automotive converter indicate that these effects may be important in determining selectivities and conversions in some industrial reactors.
Real‐time time‐optimal control of a stirred‐tank reactor using Kalman Filtering for state estimation
Authors: Lynch Edmond B. , Ramirez W. Fred
Published: June 2004

This paper presents the development and real‐time implementation of a time‐optimal control algorithm for a continuous stirred‐tank reactor. A multivariable time‐optimal control law is derived and an Extended Kalman Filter formuated for on‐line estimation and filtering. The work demonstrates the powerful capability of real‐time computation and decision‐making in optimal control and optimal estimation of process states.
Pseudoplastic falling films with concurrent gas streams
Authors: Skelland A. H. P. , Popadic V. O.
Published: June 2004

An experimental and theoretical study on gas and pseudoplastic liquid films in vertical downward flow is reported. Good agreement was obtained between predicted and measured values of the film thickness as a function of liquid shear properties and interfacial shear except in the case of the most dilute solution. Measured pressure drops in the gas in two‐phase flow depend strongly on liquid shear properties and are up to five times higher than when gas flows alone.

Aqueous Carbopol solutions were used as pseudoplastic liquids.
Modeling of heterogeneous systems in a plasma jet reactor
Authors: Bhattacharyya D. , Gauvin W. H.
Published: June 2004

A theoretical model of the behavior of a plasma jet reactor (5 000 K to 12 000 K) considering a three‐dimensional, nonisothermal, turbulent, compressible, swirling, confined flow is developed. Single particle trajectories are predicted by solving the equations of motion for the axial, radial, and tangential directions. Calculations are carried out for both argon and nitrogen gases. The model is then extended to a multiparticle system on the basis of a feed particle size distribution, concentration distribution, and loading ratio.

The calculations are applied to a study of the decomposition of molybdenum disulfide particles into molybdenum metal and elemental sulfur. Results are presented in terms of the effects on the particle history (trajectory, temperature, and conversion) of the following variables: particle size, nozzle exit temperature and velocity, injection velocity, location and angle of injection, swirl velocity, and ambient temperature conditions.
Oxygen transfer in fermentation
Authors: Tsao George T. , Lee Douglas D.
Published: June 2004

The rate of biological processes in aerobic fermentation and waste water treatment is often limited by the rate of dissolution of oxygen from air bubbles into the liquid. A clear understanding of interfacial resistance to oxygen transfer is thus of importance. An oxygen sensing microprobe was used to detect a stagnant film and a penetrable zone near an air‐water interface contaminated with surfactants. The technique, when used in clean water, can also measure the frequency of surface renewal. A linear relationship was found between the square root of the renewal rate S0.5 and the interfacial mass transfer coefficient kL, which is predicted by the Danckwerts theory.
Prediction of dynamic temperature distributions in the human body
Authors: Huckaba Charles E. , Tam Hak‐Shing , Darling Robert C. , Downey John A.
Published: June 2004

A detailed procedure is presented for the calculation of unsteady state temperature distributions throughout the human body. The adequacy of the proposed computation procedure is demonstrated by comparison of calculated and experimental results for studies conducted on subjects exposed to decreasing ambient temperatures. Core temperatures were predicted within ±0.2°C, and average deviations for individual skin temperatures generally were within ±0.5°C.
Membrane ultrafiltration of a nonionic surfactant and inorganic salts from complex aqueous suspensions: Design for water reuse
Authors: Bhattacharyya Dibakar , Garrison K. A. , Jumawan Jr. A. B. , Grieves R. B.
Published: June 2004

Complex aqueous suspensions containing a nonionic surfactant, phosphates, silicate, hypochlorite, oil, and kaolinite particulates are subjected to continuous flow membrane ultrafiltration with noncellulosic membranes. The ultrafiltrate water flux and the rejections by the Millipore PSAL membrane of total organic carbon, surfactant, and total phosphate are related by stepwise, multiple linear regression analysis (logarithmic model) to transmembrane pressure difference, thin channel velocity, membrane resistance, and feed solution concentration. The variables are adjusted to eliminate gel polarization and to minimize concentration polarization.

The data are extended, by the development and use of a computer simulation scale‐up procedure, to a 1 000 cm3/s (23 000 gal/day) laundry waste treatment and water recovery unit. The procedure considers banks of modules in series, banks in parallel, and a parallel‐series‐tapered arrangement. Membrane area requirements per unit ultrafiltrate water flux and solute rejections are predicted for water recoveries up to 95% of the inlet flow rate.
A thermodynamic method of predicting the transport of steroids in polymer matrices
Authors: Michaels A. S. , Wong P. S. L. , Prather R. , Gale R. M.
Published: June 2004

Application of Hildebrand's theory of the solubility of microsolutes in ordinary solvents, and of the Flory‐Huggins theory to the solubility of steroids in polymers, has permitted the derivation of a predictive correlation between polymer permeability and steroid crystalline melting temperature, other correlating parameters being the entropy of fusion of the steroid and the (computed) solubility parameters of steroid and polymer. The correlation permits prediction of the permeability of any steroid in any polymer with reasonable accuracy.
Interaction of activated carbon with dissolved oxygen
Authors: Prober Richard , Pyeha John J. , Kidon William E.
Published: June 2004

The sorption of dissolved oxygen on activated carbon was characterized with manometric and packed column apparatus. All carbons tested, granular and powdered, virgin and reactivated, sorbed 150 to 600 μmole of oxygen/g after run times up to 1 700 hr., but sitll not at equilibrium. The rate data generally conform to a model of sorption limited by intraparticle diffusion. Carboxylic acid groups increase by about 200 μeq/g as a result of dissolved oxygen sorption, which can account for at least 10 to 50% of the oxygen sorbed. Also, about 5% of the sorbed oxygen can be eluted into deoxygenated water.
Advanced control practice in the chemical process industry: A view from industry
Authors: Lee Wooyoung , Weekman Vern W.
Published: June 2004

This paper presents a commentary on the status of application of modern control theories to industrial chemical processes. The difficulties encountered in the implementation of advanced control to chemical reactors are critically examined in order to determine the reasons for its limited success to date. Chemical processes, very often poorly understood because of the physicochemical complexities, are nonlinear, highly interacting, spacially dependent, and continuously disturbed by many uncharacterized noises. It is time‐consuming and expensive to develop advanced control methods for these systems because few of the available theories can be applied directly. Thus, we often find it difficult to economically justify advanced control projects.
The selection of design variables in systems of algebraic equations
Authors: Book Neil L. , Ramirez W. Fred
Published: June 2004

Present algorithms for the selection of design variables produce a single combination of design variables which results in a solution sequence of minimum difficulty. A new theory entitled solution mapping results in information about all optimal combinations of design variables. This theory gives detailed information about the structure of all underspecified systems of algebraic equations which do not contain persistent iteration.
Nucleation effects in the dropwise condensation of steam on electroplated gold surfaces
Authors: Detz Clifford M. , Vermesh Robert J.
Published: June 2004

Dropwise condensation heat transfer coefficients were measured for stream on gold surfaces electroplated on copper and nickel substrates. The effect on the heat transfer of the activation of very small nucleation sites present on the gold plated copper surface was observed. In addition, the heat transfer coefficient of the gold plated nickel surface was lower than that of the gold plated copper surface.
Oxidation of acetic acid solutions in a trickle‐bed reactor
Authors: Levec Janez , Smith J. M.
Published: June 2004

Rates of oxidation of dilute, aqueous solutions of acetic acid were measured at 252° to 286°C and 67 atm in liquid full and trickle‐bed reactors packed with ferric oxide catalyst particles. Predicted global rates and conversions indicated that localized vaporization and liquid channeling could affect trickle‐bed performance.
A theory of isothermal melt spinning and draw resonance
Authors: Fisher Robert J. , Denn Morton M.
Published: June 2004

The mechanics of isothermal melt spinning are studied for a viscoelastic liquid with a power law viscosity and a constant shear modulus. Steady state velocities and stresses are in agreement with experiment. The onset of the draw resonance instability, the magnitude of diameter fluctuations in the unstable region, and a second stable region at high draw ratio are predicted accurately.
A theoretical study of pressure drop for non‐Newtonian creeping flow past an assemblage of spheres
Authors: Mohan V. , Raghuraman J.
Published: June 2004

A combination of Happel's free surface model and variational principles is used to obtain bounds on the drag offered by the creeping flow of a power law fluid past an assemblage of solid spheres. The theoretical predictions of the product of the Fanning friction factor ƒ and Reynolds number Rep are in close agreement with available experimental data on non‐Newtonian flow through porous media. The product (ƒ Rep) reduces for the Newtonian case to that of Happel and Brenner.
Separation of nonlinearly sorbing solutes by parametric pumping
Authors: Camero Arthur A. , Sweed Norman H.
Published: June 2004

A rigorous mathematical analysis shows that parametric pumps can separate, concentrate, and recover in pure form all components of a multi‐solute mixture. The obtained separation cannot be predicted by existing linear models. Criteria for determining steady periodic separations of binary mixtures are discussed in detail for batch and continuous systems.
Some performance characteristics of liquid phase spray columns
Authors: Laddha G. S. , Krishnan T. R. , Viswanathan S. , Vedaiyan S. , Degaleesan T. E. , Hoelscher H. E.
Published: June 2004

New data on residence time distribution (RTD), axial mixing, and Peclet numbers for both phases in liquid spray columns are presented.

Drop size distribution is of major interest. Continuous phase velocities affect RTD variance at high flow without appreciable effect on dispersed phase RTD variance. New correlating equations are presented.
Computer model for tubular high‐pressure polyethylene reactors
Authors: Chen C. H. , Vermeychuk J. G. , Howell J. A. , Ehrlich Paul
Published: June 2004

A computer model was developed for tubular high‐pressure polyethylene reactors. Plug flow and absence of axial mixing were assumed. Emphasis was placed on realistic modeling of the reaction kinetics and the variation of physical properties along the reaction coordinate. A good simulation of axial temperature profiles, conversion, molecular weights, molecular weight distribution, and transport properties along the reaction coordinate is believed to have been achieved. The model can be extended readily to cases where radial diffusion is significant.
Studies in chemical process design and synthesis II. Optimal synthesis of dynamic process systems with uncertainty
Authors: Nishida N. , Liu Y. A. , Ichikawa A.
Published: June 2004

The concept of the optimal synthesis of dynamic process systems with uncertain parameters is introduced. A structure parameter approach is used to theoretically derive the necessary condition for the optimal performance system structure, and an effective algorithm for implementing the synthesis method is presented. The results are applied to the optimal synthesis of a reactor‐separator system for the dynamic start‐up of two reaction systems.
Multiple minima in a fluidized reactor—heater system
Authors: Chen Herbert T. , Fan L. T.
Published: June 2004

A minimum cost design problem for a single‐reaction fluidized‐bed reactor system is analyzed in this paper. The problem's mathematical interest stems from Wilde's statements (1974) that there can be only two types of design to this nonlinear, nonconvex, multimodal problem. It is shown by a direct search procedure that, in fact, there are at least four types of optimal design. Furthermore, the type 3, rather than the type 1 design, is the global solution to the numerical example considered in Wilde's work, if the required auxiliary cooler cost is excluded.
Improving efficiency of electrostatic precipitation by physicochemical modification of the electrical resistivity of flyash
Authors: Ditl Pavel , Coughlin Robert W.
Published: June 2004

Theory and experiment show that lowered resistivity of fly ash, frequently caused by adding conditioning agents to flue gas to improve efficiency of electrostatic precipitation, is caused by capillary condensation of liquid at the contact points of ash particles, thereby providing additional pathways for flow of electrical current.
Correlation of liquid heat capacities with a four‐parameter corresponding states method
Authors: Lyman Thomas J. , Danner Ronald P.
Published: June 2004

A four‐parameter corresponding states method with the critical temperature, the critical pressure, the radius of gyration, and a fourth parameter developed from the Frost‐Kalkwarf vapor pressure equation has been applied to the correlation of liquid heat capacities. An equation has been developed to predict the temperature dependence of the saturated liquid heat capacities of both normal and polar fluids over the liquid range from a reduced temperature of 0.35 to 0.96. The accuracy of the predictions obtained is superior to that of the presently available generalized correlation for polar liquids. The new correlation may be easily adopted for computer use.
Electropolarization chromatography
Authors: Reis Joaquim F. G. , Lightfoot E. N.
Published: June 2004

The utility of electropolarization chromatography for fractionation of native protein mixtures is examined both mathematically and experimentally.

Mathematical prediction based on a simplified but basically realistic model of this process suggests it to be very promising for both analytical and preparative purposes.

This expectation is borne out by tests with well‐defined proteins in single ultrafiltration fibers. The major observed departure from model prediction is an unexpectedly sharp increase in retardation at a critical voltage specific to the protein and composition of the carrier electrolyte. This permits sharper separations than previously expected and is thus favorable.
Design of an lonic lattice for optimum cation diffusion
Authors: Ruckenstein Eli , Dadyburjor Dady B.
Published: June 2004

Varying the species and/or distance parameters of a lattice changes the activation energy of a particular species diffusing through it, thus allowing transport properties to be optimized. As an example, the activation energy of silver ions in α‐silver iodidelike structures was calculated as lattice properties were changed.
An analysis of slow reactions in a porous particle
Authors: Wen C. Y. , Wu Nancy Tsai
Published: June 2004

A one‐parameter volume reaction model is developed by a simplified analytical approach to describe reaction of a gas and a consumble solid in a porous particle. In this model, a modified Thiele modulus M is introduced to take into account the effect of solid reactant depletion during the reaction.

Experimental results of an isothermal carbon‐carbon dioxide reaction in the temperature range from 1 130° to 1 365°K under atmospheric pressure were analyzed by the working diagrams derived from this model. A satisfactory agreement between the experimental results and those predicted by the model indicated the applicability of this model.
The effect of flow maldistribution on conversion in a catalytic packed‐bed reactor. Part II. Experimental studies
Authors: Choudhary Manoj , Weller Sol W. , Szekely Julian
Published: June 2004

The modeling equations formulated for a catalytic packed‐bed reactor with distributed resistance to flow have been applied to the alumina catalyzed isomerization of 1‐butene to cis‐ and trans‐2‐butene. Flow maldistribution was deliberately created in a 5.25 cm I.D. reactor by packing different radial sections with alumina particles of different size. Effluent gas composition, monitored by gas chromatography, was found to vary with radial position in a manner consistent with the modeling equations and with the reaction rate constant previously established in a microreactor.
Melting, freezing, and channeling phenomena in ice counterwashers
Authors: Grossman Gershon
Published: June 2004

Thermal phenomena are associated with the operation of ice counter‐washers, a major component for the separation of ice and brine in freeze crystallization processes. Melting, freezing, and channeling in the upper leg of the counterwasher occur because of the temperature difference between the wash water and the ice and have important effects on the operation of the device. In the present study, these phenomena are modeled and analyzed and their scaling laws derived. Ice and wash water temperature distributions as well as variations in porosity and wash water flow rate due to melting and freezing in the ice plug are computed and plotted. The effect of channeling on counterwasher operation is studied and formulated in terms of the channel dimensions and ice plug properties. Growth rates of channels due to melting by the wash water are calculated. Results indicate that warm wash water and slow motion of the ice plug cause rapid channel growth and may be deleterious to counterwasher operation. Best conditions for recovery from channeling are obtained with wash water temperature close to freezing and high plug velocity.
Activator effects on urease kinetics
Authors: Choi C. Y. , Perlmutter D. D.
Published: June 2004

An experimental study of the effects of amino acid additives on the rates of urease kinetics showed that the degree of enhancement is sensitive to the relative levels of additives and substrate, and that enhancement can turn to inhibition at especially low concentrations of either arginine, DL‐alanine, or glycine. Kinetic models developed to interpret these and prior literature data showed that all the data are consistent in the framework of the steady state model proposed but contradict the expectations that would follow from an equilibrium based treatment.
An analysis of carrier facilitated transport in heterogeneous media
Authors: Stroeve Pieter , Smith Kenneth A. , Colton Clark K.
Published: June 2004

A theoretical model is developed for steady state diffusion in reactive heterogeneous media in which simultaneous reversible chemical reactions occur between diffusible carrier species and the transported species. The heterogeneous systems analyzed are those for which one phase is dispersed as uniform spheres in a second continuous phase, and either or both phases may be reactive. The results have a simple physical interpretation in terms of additivity of resistances. The theory is applied to oxygen diffusion in blood.
Vortex free downflow in vertical drains
Authors: McDuffie Norton G.
Published: June 2004

Performance of flush drains in gas‐liquid separators has been evaluated under conditions of variable gas flow and pressure, liquid height and flow rate, and drain diameter. For the two‐phase flow regime, liquid flow rate is found to be independent of vessel pressure or gas flow rate. Transition from weir control to orifice control of liquid flow rate occurs over the range of H/D ratios from 0.4 to 1.5. In this range, simple orifice equations do not apply. Revised design equations for use to determine minimum liquid height for maintenance of single‐phase downflow in gas‐liquid separators are presented.
The characterization of fixed beds of porous solids from pulse response
Authors: Bashi Haseeb , Gunn Donald
Published: June 2004

The response of a fixed bed of porous particles through which fluid flows to a pulse of tracer gas has been analyzed by a number of methods. It is found that analysis of the Fourier transformed and the Laplace transformed response curves for small values of the parameters of the integrals provides accurate estimates of intraparticle diffusivity and Peclet group for axial dispersion when additional information provided by the experiments is used to resolve interaction between the process coefficients in the dynamic response.
Degrees of anisotropy for fluid flow and diffusion (electrical conduction) through anisotropic porous media
Authors: Neale Graham
Published: June 2004

This work involves a quantitative comparison between diffusion (or electrical conduction) and fluid flow occurring in the principal directions of certain simple anisotropic porous media, namely, clusters of parallel circular (or elliptic) cylindrical fibers. The degrees to which the observed macroscopic properties, permeability, and effective diffusivity (electrical conductivity) depend upon the direction of flow are determined analytically. Systems of parallel fibers are shown to be considerably more anisotropic with respect to fluid flow than with respect to diffusion (or electrical conduction), this effect being very pronounced with flattish fibers. It would not appear that any general analogy exists between diffusion (electrical conduction) and fluid flow occurring within anisotropic porous media.