bluuebunny/crossref_metadata_2025_split huggingface dataset:
Char attrition during the batch fluidized bed combustion of a coal
Authors: Chirone R. , D'Amore M. , Massimilla L. , Mazza A. 
Published: June 2004

AbstractBatchwise fluidized bed combustion of a coal has been carried out to investigate the generation of elutriable carbon fines by attrition of the burning char, Differences between the purely mechanical attrition and the combustion‐assisted attrition of the char have been outlined. The time required to “activate” the char surface as regards attrition explains certain features of carbon elutriation curves. Attrition rate constants determined from these curves are compared with those previously found by continuous fluidized combustion of the same coal.
Solid‐liquid mass transfer in packed beds with cocurrent gas‐liquid downflow
Authors: Rao V. G. , Drinkenburg A. A. H. 
Published: June 2004

AbstractLocal instantaneous solid‐liquid mass transfer coefficients were measured in two‐phase gas‐liquid downflow through packed columns for 3 × 3 mm and 6 × 6 mm cylinders. An electrochemical technique was used. Liquid flow rates from 3.0 to 26.6 kg/m2·s and gas flow rates from 0.07 to 1.16 kg/m2·s covered the gas‐continuous, ripple, and pulse flow regimes. Time‐averaged mass transfer coefficients in trickle flow and in pulse flow for the pulse proper and the base (outside the pulse) were found to increase with increasing gas and liquid rates. Correlations are presented in terms of liquid phase Reynolds numbers and in terms of Kolmogoroff numbers. The mass transfer coefficients in the pulse were found to correspond closely to the coefficients that would be attained in the dispersed bubble flow regime.
Cold flow mixing rates in confined, recirculating coaxial jets with angular secondary injection
Authors: Hedman P. O. , Leavitt D. R. , Sharp J. L. 
Published: June 2004

AbstractThe mixing of gases and particles in confined, coaxial jets with angular secondary steam injection into suddenly expanded mixing chambers was studied. The effects of secondary stream injection angle, mixing chamber diameter and length, primary jet solids loadings, particle size, and secondary stream velocity on particle and gas mixing rates were determined. Gas mixing was much faster than particle mixing. Angular secondary injection significantly increased the initial gas and particle mixing rates but had little effect on the overall length of duct needed for complete mixing. The effects on initial gas mixing rate of combined angular secondary injection and increased secondary velocity were additive.
Multiplicity in continuous MSMPR crystallizers. Part II: Temperature multiplicity in a cooling crystallizer
Authors: Tavare N. S. , Garside John , Akoglu Koksal 
Published: June 2004

AbstractThis paper demonstrates the application of the theory of temperature multiplicity to the continuous mixed‐suspension, mixed‐product removal (MSMPR) cooling crystallizer as described by the coupled solute and energy balances along with the associated population balance transformed into moment equations. Exact uniqueness and multiplicity criteria are developed. Applications to specific cases together with diagrams depicting the effects of the important variables on the regions of multiplicity and uniqueness are presented.
The effects of surfactants on the motion and transport mechanisms of a condensing droplet in a high reynolds number flow
Authors: Chang Tae‐Ho , Chung J. N. 
Published: June 2004

AbstractThe motion and transport mechanisms of a condensing droplet initially contaminated with insoluble monolayer surfactant material are examined through a theoretical approach. The surface tension gradient force induced by the surfactant and the shear stress from the relative motion between droplet and its ambient vapor are evaluated on the droplet surface as major forces affecting the internal motion of the droplet. The strength of the internal motion ranges from one order of magnitude smaller than the free stream velocity for slight surfactant contamination to almost a complete stop in motion for high surfactant concentration.
The influence of a grid‐generated turbulence on the development of chemical reactions
Authors: Bennani A. , Gence J. N. , Mathieu J. 
Published: June 2004

AbstractThe evolution of slow, irreversible, isothermal, second‐order chemical reactions between two nonpremixed species is experimentally studied in a field of quasiisotropic grid turbulence developing in a water tunnel. The experiments provide some basic data on the interaction between the turbulent mixing and the reaction, which tends to remove the mixed species.
Modeling of permeators with two different types of polymer membranes
Authors: Perrin J. E. , Stern S. A. 
Published: June 2004

AbstractMathematical models have been developed for the separation of binary gas mixtures in permeator modules housing two different types of membranes simultaneously. The membranes are selected so as to exhibit reverse selectivities toward the components of a mixture, i.e., so that one membrane is more permeable to one of the components while the second membrane is more permeable to the other component. The mathematical models describe the membrane separation process for three kinds of flow patterns of the permeated (low pressure) and unpermeated (high pressure) gas streams in the permeator, namely, “perfect mixing,” counter‐current flow, and cocurrent flow. Numerical solutions of the models indicate that the extent of separation achievable in a two‐membrane permeator can be much higher than in a conventional single‐membrane permeator. Also, for given product compositions, the membrane area requirements of the former permeator can be lower than those of the latter. Countercurrent flow is generally the most efficient flow pattern in a two‐membrane permeator, and “perfect mixing” is the least efficient one, but the opposite is true under special operating conditions.
The role of porosity in filtration. Part X: Deposition of compressible cakes on external radial surfaces
Authors: Tiller F. M. , Yeh C. S. 
Published: June 2004

AbstractThe theory of deposition of compressible, particulate beds on cyclindrical surfaces is developed for both constant‐pressure and constant‐rate filtration. Radial flow is encountered in tubular filters and in both filtering and sedimenting centrifuges. It differs mathematically from filtration on planar surfaces in the manner in which the frictional drag balance on the particle structure is coupled with Darcy's equation.
Fully developed temperature waves in a bed of processed shale
Authors: Hiskakis Miltiadis , Hanratty T. J. 
Published: June 2004

AbstractThe combustion of processed shale is analyzed. By using a coordinate system moving with the same velocity as the combustion zone a model is obtained for the fully developed temperature wave. Of particular interest is the interpretation of this wave in terms of the kinetics and thermal effects of the reactions that are involved.
Heat and mass transfer in water‐laden sandstone: Convective heating
Authors: Wei Chen Kou , Davis H. T. , Davis E. A. , Gordon Joan 
Published: June 2004

AbstractA theoretical model was developed to predict the heat and mass transfer phenomena in porous materials. A water‐filled sandstone was heated in a convective oven and its water loss rates and temperature profiles were compared with theoretical results. In addition to local temperatures, moisture content, gas densities and pressure, this model also predicts the fluid flow pattern in the heated sample.
Dynamics of deep‐bed filtration. Part I: Analysis of two limiting situations
Authors: Chiang Hsu‐Wen , Tien Chi 
Published: June 2004

AbstractThe dynamic behavior of deep‐bed filtration was studied by considering two limiting situations. In the first case it was assumed that deposition leads to the presence of a reasonably smooth deposite layer over filter grains. In the second case particle aggregates, once formed, were assumed to remain rigid and the deposited particles to act as additional collectors. The effect on filter performance of the media change resulting from the presence of these two types of deposits was examined quantiatively.
Mass transfer in AC electrolysis. Part III: Study of triangular and square‐wave current on rotating electrodes
Authors: Cheng C. Y. , Chin D.‐T. 
Published: June 2004

AbstractA theoretical and experimental investigation is presented for mass transfer to a rotating hemispherical electrode when direct current (DC) superimposed with symmetrical triangular‐ or square‐wave alternating current (AC) is used for electrolysis. A film model is used for the analysis of AC concentration components. The limiting AC current density corresponding to a zero instantaneous surface concentration and the phase shift between the applied AC and the periodic potential changes are calculated and compared to the experimental studies. The experimental data agreed with the theoretical prediction to within ±8% in the regime of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 1 and less than 180. The mass transfer behavior with the triangular and square waves is further compared to that of the sinusoidal current. It is found that for a given AC frequency and rotational speed, the limiting AC current density on the electrode decreases in the order of traingular‐wave AC > sinusoidal AC > square‐wave AC.
Thermodynamically consistent quasi‐Newton formulae
Authors: Lucia Angelo , Miller D. C. , Kumar Ashwani 
Published: June 2004

AbstractNewton and quasi‐Newton methods have been used in chemical process design and optimization calculations for quite some time. They continue to be used today, both in the traditional sense and as part of the more recent hybrid method. While Newton‐based fixed‐point methods have been used to solve many different kinds of chemical process design and optimization problems, perhaps the point of single largest application has been that of multicomponent separation problems, especially equilibrium stage distillation.Quite aside from this, classical thermodynamics provides us with certain fundamental mathematical and physical relationships governing the behavior of nonideal solutions, those being the homogeneity of partial molar excess properties and their derivatives and the Gibbs‐Duhem equation.In this work, we draw a connection between the class of Newton‐based fixed‐point methods and classical nonideal thermodynamics. That is, it is shown that, with the exception of Newton's method, none of the conventional Newton‐like methods gives matrix approximations that are thermodynamically consistent. In other words, all existing nonsymmetric and symmetric quasi‐Newton formulae generate matrix approximations that do not satisfy, for either the zerodegree homogeneity or Gibbs‐Duhem equations.In light of this, a new class of quasi‐Newton formulae is presented for use in chemical process problems whose models include chemical and/or phase equilibrium. In particular, several new quasi‐Newton formulae are presented that give Jacobian or Hessian approximations that satisfy the zero‐degree homogeneity and/or Gibbs‐Duhem equations, in addition to the usual secant and perhaps symmetry and sparsity condition. This new class of formulae is called thermodynamically consistent quasi‐Newton formulae. Some numerical results are presented that show that these thermodynamically consistent quasi‐Newton formulae can provide improvements in reliability and computational efficiency when compared to existing Newton‐like methods.
Kinetics of CO oxidation over Co3O4/γ‐Al2O3. Part III: Mechanism
Authors: Perti Deepak , Kabel R. L. , McCarthy G. J. 
Published: June 2004

AbstractInterpretations of a variety of transient experiments are combined with information from the literature to reveal the roles played by the Co3O4 catalyst surface and adsorbed species. The reaction path depends on the oxidation state of the catalyst. A rather coherent picture of oxidation‐reduction catalysis by a metal oxide is obtained.
The application of drop size distribution and discrete drop mass transfer models to assess the performance of a rotating disc contactor
Authors: Al‐Aswad K. K. , Mumford C. J. , Jeffreys G. V. 
Published: June 2004

AbstractA method has been developed to calculate the overall mass transfer coefficient in an agitated liquid extraction column containing a wide range of drop sizes. The method applied the drop size distribution diagram to estimate the volume percentage of stagnant, circulating, and oscillating drops in the drop population. Individual mass transfer coefficients were then evaluated for the corresponding drop state, using the different single‐drop mass transfer models, after which the overall coefficient Kcal was calculated as the fractional sum of the individual coefficients and their proportion in the drop population. These estimated mass transfer coefficients have been compared with results obtained from a large rotating disc extractor 0.45 m in diameter and 6.75 m high, extracting acetone between water and Clairsol (a parafinic hydrocarbon, principally decane). Good agreement was obtained in the majority of the experiments when the Rose‐Kintner correlation was applied to evaluate the dispersed phase mass transfer coefficient of the oscillating drops. In all experiments agreement between the calculated and experimental overall mass transfer coefficients was improved by evaluating the concentration driving force by applying Simpson's rule, thereby introducing corrections for the variation in flowrate along the column and for possible backmixing.
Kinetics of free radical polymerizations in reactive polymer processing
Authors: Huang Y. J. , Lee L. J. 
Published: June 2004

AbstractA kinetic model has been developed for radical chain growth type of reactive polymer processing operations. This model incorporates considerations of the molecular diffusion that is described by a free volume theory and the basic reaction mechanism of the free‐radical chain polymerization. Experimental results from the bulk styrene polymerization and a reaction of sheet molding compound (SMC) showed good agreement with the model.
The dependence of viscoelastic flow functions on polymer structure for linear and branched polystyrene and polybutadiene
Authors: Ramachandran S. , Christiansen E. B. 
Published: June 2004

AbstractExperimentally determined viscosities, first and second normal stress differences, and compliances for concentrated solutions of linear and four‐arm star‐branched polystyrenes and polybutadienes depend on the shear rate and the molecular weight, in agreement with theory and previously reported experimental results. The ratios of the second to first normal stress difference are ‐0.29 and ‐0.214 for the linear and branched polymers, respectively, independent of molecular weight, molecular weight distribution, concentration, and shear rate.
Influence of site energy distribution on catalytic rates with multicomponent chemisorption
Authors: Bhat Y. S. , Prasad S. D. , Doraiswamy L. K. 
Published: June 2004

AbstractWithout using the assumption of constancy of mole fractions in adsorption space, dual‐component adsorption accompanied by catalytic reaction on a heterogeneous surface is modeled. A simple parallel reaction scheme which is supposed to idelalize key steps in cracking and disproportionation reactions is studied. Quantities of interest in catalytic kinetics such as mean surface coverage, mean squared surface coverage, and others are calculated as statistical averages over the bivariate analogs of four well‐known monovariate distributions, with the assumption of relaistic heats of adsorption. Using a variant of the Mellin transform method proposed earlier, explicit expressions for the rates are given as functions of partial pressure ratio and the parameters characterizing the site energy distribution. Methods are proposed to determine the characteristic ratio of partial pressures at which a desired selectivity pattern is realized. Lastly, two reaction schemes which outline key steps in platforming and reforming reactions and which occur on bifunctional catalysts are analyzed and methods for determining the characteristic pressure ratio are suggested.
Liquid‐liquid interfacial areas formed by turbine impellers in baffled, cylindrical mixing tanks
Authors: Eckert R. E. , McLaughlin C. M. , Rushton J. H. 
Published: June 2004

AbstractAn extensive experimental study on the formation of liquid‐liquid interfacial areas was conducted using flat‐blade turbine impellers in standard mixing tank geometry. The interfacial areas were measured with a light probe for different combinations of volume fraction, continuous and dispersed phase physical properties, and mechanical mixing conditions.
Size‐dependent crystal growth—A manifestation of growth rate dispersion in the potassium alum‐water system
Authors: Girolami M. W. , Rousseau R. W. 
Published: June 2004

AbstractGrowth of potassium alum crystals was characterized by the advance rates of crystals on the leading edge of population distributions and by the advance rates of the modes of these distributions. Growth rates of crystals on the leading edge appeared to follow size‐dependent kinetics, but the observed spread of the distribution about the average size was much greater than would be expected from size‐dependent growth alone. The spread of the distribution was correlated with the extent of growth determined from the net advance of the average crystal size. These quantitative and qualitative results show that what has often been referred to as size‐dependent growth is in fact a manifestation of growth rate dispersion.
A simultaneous‐modular approach to process flowsheeting and optimization. Part I: Theory and implementation
Authors: Chen Hern‐Shann , Stadtherr M. A. 
Published: June 2004

AbstractThere basic problem formulations for the simultaneous‐modular approach are discussed, as are three alternative methods for computing the flowsheet‐level Jacobian. A new algorithm for partitioning and tearing when using the simultaneous‐modular approach is also presented. SIMMOD, our implementation of the simultaneous‐modular approach is then outlined. In subsequent papers in this series we use SIMMOD to study the performance of the simultaneous‐modular approach on process simulation and optimization problems, as well as to perform experiments on different numerical strategies for implementing the simultaneous‐modular approach.
Annular flow pressure drop model for pease–anthony‐type venturi scrubbers
Authors: Viswanathan S. , Gnyp A. W. , St. Pierre C. C. 
Published: June 2004

AbstractAn annular flow pressure drop model has been developed and compared with experimental data obtained on a pilot‐plant‐size Pease‐Anthony‐type venturi scrubber. Droplet and film accelerations as well as wall friction, based on the two‐phase Lockhart‐Martinelli correlation, are considered. Excellent agreement with experimental data is demonstrated for a wide range of throat gas velocities, liquid to gas ratios, and film flow rates for a single scrubber geometry.
Prediction of adsorption and desorption of protein on dextran based ion‐exchange resin
Authors: Tsou Hai‐Shung , Graham E. E. 
Published: June 2004

AbstractThe equilibrium and kinetic adsorption and desorption of bovine serum albumin (BSA), fraction V, on Sephadex A‐50 has been studied. The equilibrium data have been presented by a Langmuir isotherm for both adsorption and desorption conditions. The kinetics of adsorption in a batch system may be represented by a simple diffusional model. The kinetics of desorption of BSA in a batch system show a very fast initial rate due to the rapid shrinkage of the resin with changes in salt concentration. This has been modeled by including a protein exclusion term in the kinetics for desorption. The above information has been used to predict the breakthrough of BSA in a column operation. Under the pressure exerted in a column flow system the Sephadex A‐50 is severely compressed. The effect this has on the breakthrough rate of BSA has been demonstrated.
Role of rhenium in Pt‐Re‐Al2O3 reforming catalysis—An integrated study
Authors: Jothimurugesan K. , Nayak A. K. , Mehta G. K. , Rai K. N. , Bhatia S. , Srivastava R. D. 
Published: June 2004

AbstractThe inclusion of Re in Pt‐Re‐Al2O3 reforming catalysts to improve the lifetime is known, but how rhenium functions and how it is disposed in the catalyst remain unclear. These fundamental questions have been attempted in this study by the use of proton‐induced X‐ray emission and Rutherford backscattering spectrometry (together with electron microscopy and chemisorption studies) to characterize a commercial like catalyst for dehydrogenation of methylcyclohexane.
The determination of equilibrium exchange rates in catalytic reactions: Application to methanol synthesis on Cu‐Zn‐oxide
Authors: Willcox Dave , Garland Marc , Liu George , Kung H. H. 
Published: June 2004

AbstractA method is described to obtain reaction rates of chemical reactions in a network in which there are more independent reactions thatn independent chemical species. The method makes use of the linear theory of nonequilibrium thermodynamics to obtain the equilibrium exchange rates of the reactions, which are calculated from the relaxation data as the system approaches chemical equilibrium. A method which follows very closely that of Wei and Prater (1962) can be used to treat the relaxation data. As an example, the method was applied to the methanol synthesis reaction from CO, CO2, and H2 over a Cu‐Zn oxide catalyst. It was concluded that successful application of the method is limited to systems in which all the processes contributing to the observed relaxation are known, in addition to the common limitations due to noise in experimental measurements.
Vacuum sorption pumping studies with pure gases on molecular sieves
Authors: Crabb K. S. , Perona J. J. , Byers C. H. , Watson J. S. 
Published: June 2004

AbstractLow‐pressure, low‐temperature adsorption of N2 and CO2 were studied in beds of 4A molecular sieves. System parameters were estimated by a comparison of experimental results and a molecular‐flow theoretical model. Nitrogen data followed theoretical prediction. Theory adequately represented pressure above the bed for CO2, while pressure drops deviated deviated significantly from the model.
Effect of drag‐reducing polymers on mass transfer fluctuations
Authors: Vassiliadou Eleni , McConaghy G. A. , Hanratty T. J. 
Published: June 2004

AbstractElectrochemical techniques are used to show that drag‐reducing polymers decrease the magnitude and the frequency of mass transfer fluctuations. Measurements of the frequency spectrum of the mass transfer fluctuations allow calculation of the normal component of velocity fluctuations in the immediate vicinity of the wall. This information is used to interpret the observed effect of drag‐reducing polymers on the rate of mass transfer.
Optimal, real‐time monitoring of particle size distribution in a fluidized bed
Authors: Cooper D. J. , Clough D. E. 
Published: June 2004

AbstractA novel method for tracking particle size distribution dynamics in a fluidized bed yields on‐line, real‐time measurements of particle size distribution that are representative of actual conditions. These measurements are somewhat corrupted with noise (random error), however, and are available to the computer only at discrete time intervals. An optimal filtering algorithm combines the measurements with predictions from an idealized dynamic model to yield particle size distribution estimates that are not only on‐line and real‐time, but also virtually continuous and well‐behaved.