bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steady‐state multiplicity of a nonadiabatic bubble column with fast reactions
Authors: Huang D. T.‐J. , Varma Arvind 
Published: June 2004

AbstractA steady‐state model is developed for a nonadiabatic bubble column with fast pseudo‐nth‐order reactions. A priori bounds are obtained for steady‐state temperature and conversion, and analytic necessary and sufficient criteria are derived for the prediction of uniqueness and multiplicity of the steady states as a function of system physico‐chemical parameters. For the special case of pseudo‐first‐order reactions, the occurrence of multiple steady states is shown to be more possible in a bubble column than in a gas‐liquid CSTR for equivalent system parameters.
Design and experimental evaluation of controllers for process undisturbability
Authors: Shah S. L. , Fisher D. G. , Seborg D. E. 
Published: June 2004

AbstractSelected state and/or output variables can be made undisturbable, i.e., invariant, to arbitrary, unmeasured changes in specific input variables by properly designed feedback and feedforward controllers. Simulation and experimental applications to a computer‐controlled, pilot plant evaporator gave results superior to conventional controllers.Necessary and sufficient conditions for undisturbability are expressed in terms of the structure of the coefficient matrices of the state space model and equivalently of the corresponding eigenvector matrix. The design procedure normally includes arbitrary specification of all closed‐loop eigenvalues and up to r elements of each eigenvector, where r is the number of control (manipulated) variables.
Regeneration of powdered activated carbon. Part I. Thermal decomposition kinetics
Authors: Chihara Kazuyuki , Smith J. M. , Suzuki Motoyuki 
Published: June 2004

AbstractKinetics of thermal regeneration of powdered activated carbon containing adsorbed sucrose was studied from 298 to 1033 K. Most of the data were obtained (by measuring mass vs. time of spent carbon samples) in a thermal gravimetric apparatus. The regeneration process was interpreted in terms of a two‐step process: (1) low‐temperature decomposition to an adsorbed intermediate and gaseous products; and (2) a higher temperature decomposition of adsorbed intermediate into adsorbed residual carbon and gaseous products.Surface area measurements indicated that most of the original carbon surface, but not all, could be recovered by thermal (with inert gas) regeneration up to 773 K. If permanent loss in surface is to be avoided during continued, cyclical use of the carbon, reaction with an oxidizing gas would be required after thermal regeneration.
An efficient, general method for computation of countercurrent separation processes with axial dispersion
Authors: Ricker N. L. , Nakashio Fumiyuki , King C. J. 
Published: June 2004

AbstractA calculational method is proposed for the simulation of steady‐state, multisolute, countercurrent extraction with axial dispersion. The method provides for complex chemical‐equilibrium and phase‐equilibrium relationships, and accounts for the individual resistances of the liquid phases in the calculation of mass‐transfer rates. The solution procedure follows that developed by Newman (1967, 1968) for systems of simultaneous, second‐order difference equations.Three example problems are solved to demonstrate the efficiency and flexibility of the method. These include (1) an example from McSwain and Durbin (1966), (2) calculation of axial‐dispersion and mass‐transfer parameters from experimental data for the extraction of acetic acid from water by a tertiary amine in an RDC extractor, and (3) simultaneous extraction of solutes that interact in an acid‐base complexing reaction at the liquid‐liquid interface. The examples all assume that extraction is governed by interphase mass‐transfer rates and cell‐wise backmixing; however, the method is also applicable to equilibrium‐stage separators, separators described by the diffusional model of axial dispersion, and other countercurrent separation processes.
Forces on immersed tubes in fluidized beds
Authors: Kennedy T. C. , Donovan J. E. , Trigas Athanasios 
Published: June 2004

AbstractThe external forces imparted by the bed material on tubes in a fluidized bed contribute to failure of the tubes and their support systems. The objective of this investigation was to provide data on tube forces to be used in structural design. Forces on tubes of various lengths were measured in fluidized beds operating at room temperature. The parameters varied in the experiments were superficial gas velocity and tube array height above the gas distributor. The force‐time histories consisted of a series of pulses, whose magnitudes were approximately linearly proportional to tube length. Spectral analyses of the time series indicated that the primary frequency composition of the load was below 25 Hz.
Local hold‐up and liquid velocity in air‐lift reactors
Authors: Merchuk Jose C. , Stein Yehuda 
Published: June 2004

AbstractMeasurements of local hold‐up and liquid recirculation rate in an air‐lift reactor were performed with two types of gas spargers using a manometric technique. A simple exponential function correlated properly the liquid velocity measured to the gas flow rate. The local hold‐up varied appreciably along the column and showed a maximum in most of the cases. A simple linear relationship correlated the local gas velocity with the total flow rate of the mixture.
A perturbed hard‐sphere, corresponding states model for liquid metal solutions
Authors: Paulaitis M. E. , Eckert C. A. 
Published: June 2004

AbstractMolecular thermodynamics is used to develop a new model for the prediction of the thermodynamic properties of liquid metal mixtures. It combines corresponding states theory with a perturbed hard sphere model to predict successfully, without adjustable parameters, a variety of mixture properties from pure component properties for simple eutectic mixtures.
Studies in reaction path synthesis
Authors: Govind Rakesh , Powers G. J. 
Published: June 2004

AbstractThe development of processes requires the consideration of a wide variety of reactions which are required to transform raw materials into desired products, solve separation problems, and heat or cool process streams. These reactions have to be evaluated on the basis of raw material costs, kinetics, potential separation difficulties, catalyst costs, safety and reliability, as well as other factors that would arise in their industrial implementation. In this paper, the current status of research in reaction path synthesis has been reviewed. Details have been presented on the REACT program that has been developed for the synthesis of reaction paths for industrial organic chemicals.
Computation of phase and chemical equilibrium, part IV: Approach to chemical equilibrium
Authors: White Charles W. , Seider Warren D. 
Published: June 2004

AbstractThe Rand algorithm for calculation of compositions in phase and chemical equilibrium is extended to permit specifications of extents of reactions that cannot be taken at equilibrium. Pseudo‐Gibbs free energies of formation are introduced to permit specification of temperature approaches. The extended algorithm is demonstrated for methane reforming.
Intermixing over cell boundary between taylor vortices
Authors: Kataoka Kunio , Takigawa Takahiro 
Published: June 2004

AbstractThe rate of exchange of fluid elements between Taylor vortices was experimentally determined for low axial flow rates. A model was formulated defining the exchange coefficient appropriate for this flow system. In the laminar vortex flow region, the measured exchange coefficient increases with Re but is almost independent of Ta.
Steady flow through porous media
Authors: Greenkorn R. A. 
Published: June 2004

AbstractThe increasing demands for oil, water, and food produced in an environmentally sound manner have placed emphasis on the manner of their production, a major part of which is concerned with flow through porous media.The movement of materials through porous media is of interest in many disciplines: in chemical engineering—adsorption, chromatography, filtration, flow in packed columns, ion exchange, reactor‐engineering; in petroleum engineering—displacement of oil with gas, water and miscible solvents including surface‐active agent solutions and description of reservoirs; in hydrology—movement of trace pollutants in water systems, recovery of water for drinking and irrigation, salt water encorachment into fresh water reservoirs; in soil physics—movement of water, nutrients, and pollutants into plants; in biophysics—life processes such as flow in the lung and the kidney.This paper reviews the fundamentals of steady flow through porous media: it discusses the pseudotransport coefficients permeability, capillary pressure, and dispersion and relates these coefficients to the geometry of porous media. It also discusses single‐fluid flow, multifluid immiscible flow, and multifluid miscible flow including the effects of heterogeneity, nonuniformity, and anisotropy of media.
Evolutionary synthesis of separation processes
Authors: Nath R. , Motard R. L. 
Published: June 2004

AbstractThis paper deals with the problem of finding, among many alternatives, the sequence of separation units that will isolate desired products from given feed at the minimum cost. Multicomponent products can be specified. An evolutionary procedure is presented. This method consists of two phases. In the first phase, a good initial structure is created by heuristic methods. In the second phase, the initial structure is successively modified by making evolutionary structural changes. This logic has been programmed on a digital computer and has been tested on several problems.
Solubility extrema in solid‐fluid equilibria
Authors: Kurnik R. T. , Reid R. C. 
Published: June 2004

AbstractExperimental data and theory both support the contention that there is a maximum solubility in solid‐fluid equilibria. An example system, naphthalene‐ethylene, at temperatures between the upper and lower critical end points and at pressures from 1 to 1000 bar is considered. There is also a solubility minimum in this system.
Distillation models for two partially immiscible liquids
Authors: Ferraris Guido Buzzi , Morbidelli Massimo 
Published: June 2004

AbstractWe hereby submit three different numerical methods for the solution of the multicomponent distillation model for two partially immiscible liquids. A procedure to define the real number of phases present on each stage has been developed. The proposed Newton‐Raphson method allows efficient solution of problems with a large selection of the unknowns and the specification equations.
Modeling the flow of viscoelastic fluids through porous media
Authors: Deiber J. A. , Schowalter W. R. 
Published: June 2004

AbstractA tube with sinusoidal axial variations in diameter has been used as a first step toward modeling the flow channels of a porous medium in such a way that appreciable Lagrangian unsteadiness is present. Experiments with dilute aqueous solutions of a polyacrylamide (Dow Separan AP‐30) show that the Lagrangian unsteadiness gives rise to an increase in resistance to flow through the sinusoidal channel relative to that predicted for a purely viscous fluid. The increase in pressure drop can occur as a consequence of fluid elasticity, without any observable secondary flow. At sufficiently high flow rates, secondary flow appears.
Progressive freezing of composites analyzed by isotherm migration methods
Authors: Talmon Yeshayahu , Davis H. T. , Scriven L. E. 
Published: June 2004

AbstractThe Isotherm Migration Method of numerically analyzing conduction with phase change is modified to handle surface and external resistances, appearance, and propagation of successive fronts into slabs of composite material of one or more constituents finely dispersed in a matrix, different components transforming at different temperatures. Procedures are developed for selecting temperature intervals between isotherms, initially locating isotherms by means of analytical approximations to the earliest stages, and thereafter inserting and removing isotherms as appropriate, particularly when each component gives rise to a separate front.
Numerical solution of nonequilibrium multicomponent mass transfer operations
Authors: Billingsley D. S. , Chirachavala Arun 
Published: June 2004

AbstractAn improved model and solution procedure for nonequilibrium, multicomponent, two‐phase, steady‐state mass transfer problems are developed. Processes as diverse as packed column operation and the drying of porous solids are included. Ideas such as “HETP,” “HTU” or “mass transfer section” are avoided. “Stiff” systems appear to be handled well.
Electrokinetic phenomena in the filtration of colloidal particles suspended in nonaqueous media
Authors: Chowdiah P. , Wasan D. T. , Gidaspow D. 
Published: June 2004

AbstractFiltration of carbon black particles from tetralin through a bed of sand with simultaneous measurement of bed streaming potential shows that the charge on the filter and its neutralization by depositing colloidal particles plays an important role in filter performance. Filter capacities up to the point of charge neutralization, calculated from knowledge of the colloid and filter zeta potentials using a semitheoretical model for variation of filter surface charge characteristics, are found to be in good agreement with experimental values.
Analysis of particulate removal in venturi scrubbers—effect of operating variables on performance
Authors: Placek T. D. , Peters L. K. 
Published: June 2004

AbstractA theoretical model of venturi scrubber performance consisting of the governing differential equations for momentum, material, and energy exchange is solved using a Milne fourth‐order predictor—Hamming corrector numerical integration procedure. The model provides for specification of the operating variables, including scrubber geometry, throat gas velocity, liquid to gas loading ratio, and collector droplet and particle‐size distributions. Liquid loading ratio and gas velocity are shown to be the two most important operating variables, while the dispersity of the droplet size distribution only slightly affects collection efficiency over the operating range normally encountered. Location of the liquid injection site and length of the throat are also important design considerations. While particle collection in venturi scrubbers has typically been assumed to occur in the potential flow regime, the present results show that collection can also occur under conditions corresponding to viscous flow about the collecting droplets. The transition Reynolds number used to change from the potential to viscous flow equations affects the predicted performance.
Adsorption‐desorption barrier, diffusional exchanges and surface instabilities of longitudinal waves for aperiodic regimes
Authors: Hennenberg M. , Sanfeld A. , Bisch P. M. 
Published: June 2004

AbstractOur purpose is to give the physical conditions under which transfer of a surfactant through a fluid interface between two immiscible liquids may induce aperiodic convective motion.Adsorption‐desorption rates are considered together with diffusional exchanges. New kinds of surface instabilities are then predicted.
Reduction of thermodynamic data by means of the multiresponse maximum likelihood principle
Authors: Kemeny S. , Manczinger J. , Skjold‐Jørgensen S. , Toth K. 
Published: June 2004

AbstractThe statistical behavior of some common parameter estimation methods is investigated by simulation. The methods based on the maximum likelihood principle give the best estimates of parameters in a given model. An analysis of the possibilities for detecting systematic errors by means of the maximum likelihood method showed that this method gives at best the same information as other well known tests.
Solute condensation in adsorption beds during thermal regeneration
Authors: Friday David K. , Levan M. Douglas 
Published: June 2004

AbstractThis theoretical study shows that a liquid phase can be developed in and passed through a fixed‐bed adsorber during thermal regeneration. The liquid results from passing hot gas from the inlet end of the bed, where the adsorbate is desorbed, towards the cool outlet end, where condensation of the solute occurs. The stage model of an adsorption bed is applied to two examples, the regeneration of an activated carbon bed with adsorbed benzene using hot nitrogen and the regeneration of a 4A molecular sieve bed with adsorbed water using hot methane.
Carbon dioxide concentration for manned spacecraft using a molten carbonate electrochemical cell
Authors: Winnick J. , Toghiani H. , Quattrone P. D. 
Published: June 2004

AbstractA high‐temperature molten carbonate electrochemical cell has been tested for use as a carbon dioxide concentrator in a manned spacecraft. Carbon dioxide is removed from a stream of cabin air supplied to the cathode of the bench scale cell. It is then concentrated through the molten carbonate electrolyte to the anode. The anode is fed either hydrogen (energy producer) or nitrogen (substance producer). Performance variation with gas flow rate, cell temperature, carbon dioxide partial pressure, and current are presented and analyzed.
The rheological characterization of coal liquefaction preheater slurries
Authors: Thurgood J. R. , Hanks R. W. , Oswald G. E. , Youngblood E. L. 
Published: June 2004

AbstractRheological characterizations were made for a coal liquefaction preheater slurry; measurements were made in line at high temperature and high pressure. Above 400°K, the coal‐solvent slurry (35 wt. % coal) was pseudoplastic and was adequately modeled by a power‐law equation. Experimental data over a temperature range of 400 to 700°K were correlated, and critical slurry velocities for transition from laminar flow were calculated for flow in several pipe diameters.
A study of the volumetric and phase behavior of binary systems. Part I. Critical properties of propane‐perfluorocyclobutane mixtures
Authors: Barber J. R. , Kay W. B. , Teja A. S. 
Published: June 2004

AbstractThe volumetric and phase behavior of propane‐perfluorocyclobutane mixtures has been determined in the critical region. This system exhibits a minimum temperature point in its critical locus curve and forms a positive critical azeotrope. The measured critical points in this system and their correlation using an extended corresponding states principle are reported in this paper.
A study of the volumetric and phase behavior of binary systems. Part III. P‐V‐T‐x data and second virial coefficients of propane‐perfluorocyclobutane mixtures
Authors: Barber J. R. , Kay W. B. , Teja A. S. 
Published: June 2004

AbstractP‐V‐T‐x data for the propane‐perfluorocyclobutane system are reported in this paper. The data cover a temperature range from 329.4 to 397.7°K and a pressure range from 60 to 6920 kPa. The low pressure compressibility measurements were used to determine second virial coefficients of pure propane and pure perfluorocyclobutane and for seven of their mixtures. The prediction of second virial coefficients using an extended corresponding states principle is also reported. Excellent predictions of the second virial coefficients of both pure components and mixtures have been obtained using, in the case of mixtures, a binary interaction coefficient obtained from a study of the critical states of the system.
A dynamic method for liquid‐particle mass transfer in trickle beds
Authors: Tan C. S. , Smith J. M. 
Published: June 2004

AbstractPrevious investigations of liquid‐to‐particle mass transfer in trickle beds have used non‐porous particles. However, the applications of trickle beds have been for reactions or adsorption employing porous catalysts as adsorbents. In this study a method of dynamic adsorption with porous particles is developed. The procedure is to extrapolate the response to a step‐function input of non‐volatile adsorbate to a short time where intraparticle diffusion and adsorption do not affect the overall process.The method is applied to the adsorption of benzaldehyde from aqueous solutions in a bed of granular, activated carbon particles. Measurements were made for three particle sizes, in adsorbers of two diameters, at 298K and 1 atm. The gas flow rate had no discernible effect on the mass transfer coefficients, kLsaLs, over a superficial velocity range of 1.47 to 8.0 × 10−2 m/s, but kLsaLs increased with liquid rate. The results, correlated as Sherwood vs. Reynolds number, agree well with the nonporous particle data of Van Krevelen and Krekels (1948), but suggest larger Sherwood numbers than similar data from later investigations.The wide range of mass transfer results for either liquid‐to‐particle or liquid‐to‐gas in trickle beds seems to be due in large measure to the difficulty in reproducing the rivulent flow pattern of liquid from bed to bed.
Dynamics of a creeping Newtonian jet with gravity and surface tension: A finite difference technique for solving steady free‐surface flows using orthogonal curvilinear coordinates
Authors: Dutta Anit , Ryan M. E. 
Published: June 2004

AbstractA finite difference technique capable of simulating steady, incompressible, viscous, free‐surface flows has been successfully applied to the motion of a creeping Newtonian jet, including both surface tension and gravitational forces. In accordance with experimental results, the numerical solutions predict either a 12 or 16% increase in the jet dimensions depending on whether the jet emerges from a circular or a slit die. Both gravity and surface tension inhibit the swelling behavior.
A chemical theory for the thermodynamics of highly‐solvated liquid metal mixtures
Authors: Eckert C. A. , Smith J. S. , Irwin R. B. , Cox K. R. 
Published: June 2004

AbstractChemical solution theory has been shown to be particularly well‐suited for certain classes of liquid metal mixtures. A generalized formulation of this approach is presented and it eliminates the need for mechanistic information. The results are in good agreement with many data, and could lead to a variety of industrial applications of liquid metal solvents.
Hydrogenation of nitrobenzoic acid
Authors: Andersson Bengt 
Published: June 2004

AbstractAqueous solutions of p‐nitrobenzoic acid were hydrogenated in the presence of Pt/C and Pd/C catalysts in a slurry reactor. External as well as internal mass transport steps were studied using a membrane H2‐electrode and a metal probe electrode. After the influence of the mass transport effects was corrected for, it was possible to obtain corrected values of the kinetic characteristics of the overall chemical reaction. The mechanism was studied using potential and polarization methods.
Further work on multicomponent liquid phase adsorption in fixed beds
Authors: Wang Shu‐Chieh , Tien Chi 
Published: June 2004

AbstractThe problem of multicomponent liquid phase adsorption in fixed beds was studied further. In contrast to the earlier work (Hsieh et al., 1977), the method developed in this work is more efficient and also has a greater scope of applicability as it incorporates the use of the IAS (Ideal Adsorbed Solution Theory) method for the estimation of multicomponent adsorption equilibrium data. It was shown that the use of the more complex IAS method for the prediction of the isotherm data does not present insurmountable obstacles as once feared (DiGiano, 1978) but provides much better prediction of carbon adsorption. An extension of the method to batch adsorption was shown to be straightforward and presented no special difficulty.