bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reaction regimes in coal oxidation
Authors: Karsner G. G. , Perlmutter D. D. 
Published: June 2004

AbstractA series of seven coals were oxidized in a fixed bed reactor to determine the controlling reaction regimes during mild coal oxidation. The effects of coal porosity and particle size, reactor temperature, and oxygen partial pressure were evaluated. The results show that coal‐oxygen reactions are controlled by the rate of internal gaseous diffusion for most coals, and by the rate of chemical reaction for the most porous coal of the set tested. Particle size effects also suggest internal diffusional control. Determinations of cumulative oxygen deposition indicate that surface areas several orders of magnitude greater than the superficial surface can participate in oxidation reactions, putting in doubt the applicability of the model previously derived by Kam et al. (1976a) for external mass transfer control.
Coke deposition in the thermal cracking of ethane
Authors: Sundaram K. M. , Van Damme P. S. , Froment G. F. 
Published: June 2004

AbstractA novel experimental setup allowed both the kinetics of the thermal cracking of ethane and of the coke formation to be studied over a temperature range extending from 750 to 870°C. The overall kinetics of ethane disappearance are in excellent agreement with previously reported pilot results. Coking rates are initially high but rapidly decrease to reach an asymptotic value. The initial product distribution also differs from the asymptotic product distribution. A kinetic model for the coking is derived from the experiments and used in conjunction with a set of conservation equations for the simulation of industrial ethane cracking. The predicted run length, thickness of the coke layer and evolution of the tubeskin temperatures are in agreement with industrial observations.
Simulation of particulate removal in gas‐solid fluidized beds
Authors: Peters M. H. , Fan Liang‐Shih , Sweeney T. L. 
Published: June 2004

AbstractA mathematical model for simulating particulate removal in gas‐solid fluidized beds is developed based on bubble assemblage concepts and particulate collection mechanisms. The importance of fluidization mechanics on the overall fluidized bed filtration performance is emphasized in the present study. Model predictions of fluidized bed filtration efficiencies are shown to compare favorably to the experimental results of various investigations. Because of the general formulation of the proposed model, it is believed to be applicable in the design of fluidized bed filtration operations.
Thermodynamic properties of adsorbed mixtures of benzene and cyclohexane on graphitized carbon and activated charcoal at 30°C
Authors: Myers A. L. , Minka C. , Ou D. Y. 
Published: June 2004

AbstractExperimental data at 30°C are reported for the adsorption of mixtures of benzene and cyclohexane on two types of carbon surface: graphitized carbon and activated charcoal. The properties of the adsorbed solution approach those of bulk liquid at vapor saturation for graphitized carbon, but not for activated charcoal. The mixtures adsorbed on graphitized carbon are nonideal, and the deviations from ideality increase with surface coverage. For activated charcoal, the adsorbed mixtures are nearly ideal at all coverages. Mixture behavior for both adsorbents can be predicted without using experimental data for the adsorbed mixtures.
Fluidized bed freeboard phenomena: Entrainment and elutriation
Authors: Wen C. Y. , Chen L. H. 
Published: June 2004

AbstractA model describing the entrainment of solid particles in the freeboard region of a fluidized bed is proposed. Published experimental data have been used to correlate the entrainment rate near the bed surface and the elutriation rate above the bed. It has been shown that the column diameter can have an important influence on the amount of fines elutriated.
Thinning of a liquid film as a small drop or bubble approaches a solid plane
Authors: Lin C.‐Y. , Slattery J. C. 
Published: June 2004

AbstractWhen a small drop or bubble approaches a solid surface, a thin liquid film forms between them, drains, until an instability forms and coalescence occurs. A hydrodynamic theory is developed for the first portion of this coalescence process: the drainage of the thin liquid film while it is still sufficiently thick that the effects of London‐van der Waals forces and electrostatic forces can be ignored. This theory describes the time rate of change of the film profile, given only the drop radius and the required physical properties. Predictions are compared with profiles measured by Platikanov (1964) for gas bubbles. It is concluded that, even with only a trace of surfactant present, the liquid‐gas interface may be nearly immobile (tangential components of velocity are zero) and the surface viscosities will have little effect upon the drainage rate.
Experimental determination of the light distribution in a photochemical reactor: Influence of the concentration of an absorbing substance on this profile
Authors: Tournier A. , Deglise X. , Andre J. C. , Niclause M. 
Published: June 2004

AbstractKnowledge of the local distribution of the light energy, in a photochemical reactor in the presence of an absorbing substance which reacts at a rate of order different from one with respect to the adsorbed light intensity, is important in order to calculate the mean rate of reaction and the design of the reactor. Here we report a simple method for the determination of this profile as a function of the concentration of an absorbing substance and we compare the results obtained with the models of emission from the literature. A semi‐empirical model accounting for our experimental results is presented.
Modelling highly skewed chromatographic response curves
Authors: Gelbin D. , Wolff H.‐J. , Friedrich S. 
Published: June 2004

AbstractA model is presented in which damaged pores are distributed throughout a network of undamaged pores within a spherical particle. The differential equations are solved according to the numerical procedure of Haynes, Jr. (1975). The model is intended to simulate more highly skewed chromatographic response curves than the two‐zone model recently proposed by Chou and Hegedus (1978).Pulse chromatographic measurements in fresh NaMgA zeolites using i‐butane as a tracer which only enters the macropores yield response curves with relatively low skew, which are readily fitted by a system of equations accounting for diffusion in a monodisperse pore system. For hydrothermally treated zeolites effective diffusivities and Henry constants are considerably lower and the skew higher than in fresh samples.Curve fitting with the model proposed below is quite satisfactory, and the characteristic parameters determined are approximately constant at the flowrates studied. Application of the model should not be restricted to hydrothermally treated zeolites, but may be extended to catalysts or adsorbents with macroporous structures damaged by other forms of ageing.
Cylindrical cell model for the hydrodynamics of particle assemblages at intermediate reynolds numbers
Authors: Tal (Thau) Reuven , Sirignano W. A. 
Published: June 2004

AbstractThe spherical cell model for transport in assemblages of spheres, which stems from the low Reynolds number hydrodynamics, has a serious physical limitation when extended to the range of intermediate Reynolds numbers. Spherical symmetry cannot persist around a sphere, given a definite direction of convection. The boundary conditions of the spherical cell model are inappropriate and a cubic cell model would best represent the system. However, in order to avoid undue mathematical difficulties peculiar to three‐dimensional problems, a cylindrical cell model is proposed.A numerical solution of the Navier‐Stokes equations expressed in vorticity‐stream function variables has been performed in conjunction with the cylindrical cell model for various values of porosity and Reynolds number. A much better agreement of the drag coefficient with experimental results is obtained by the cylindrical cell model than by the spherical cell model.
Dispersion by laminar flow
Authors: Powell R. L. , Mason S. G. 
Published: June 2004

AbstractDispersion was studied by subjecting clusters of spherical particles (20–400 μm) to laminar flow fields. The clusters were: cohesionless, consisting of particles suspended in the same liquid as the bulk medium and cohesive for which a different liquid was used to make the suspension. Both qualitative and quantitative results are presented.
Non‐isothermal channel flow of non‐Newtonian fluids with viscous heating
Authors: Dinh S. M. , Armstrong R. C. 
Published: June 2004

AbstractApproximate analytical solutions of the local temperature variations, due to viscous heating, in channel flows of non‐Newtonian fluids with small Nahme‐Griffith numbers were obtained by the WKB‐J method. The results are general and easy to use so that extensive numerical computations are not required. Comparisons between the approximate analytical solution and complete numerical solution showed that the relative differences were very small.
Design parameters estimations for bubble column reactors
Authors: Shah Y. T. , Kelkar B. G. , Godbole S. P. , Deckwer W.‐D. 
Published: June 2004

AbstractGas‐liquid as well as gas‐liquid‐solid bubble column reactors are extensively used in the chemical industry. This review evaluates the present state of the art for the estimation of “nonadjustable” parameters in bubble column reactors. All the pertinent literature concerning these parameters is discussed and the discussion is followed by relevant recommendations for their predictions. Literature on the modified bubble columns has been incorporated. Finally, the inadeqacies of the data in some areas of practical importance have been pointed out and the recommendations for future work are outlined.
Concentration dependence of surface diffusion coefficient of propionic acid in activated carbon particles
Authors: Suzuki Motoyuki , Fujii Takao 
Published: June 2004

AbstractA Wicke Kallenbach type steady state diffusion experiment was performed for varying concentrations of propionic acid solution through activated carbon pellets. Since surface diffusion is a dominant mechanism, concentration dependence of the surface diffusion coefficient is precisely determined from the change of diffusion flux with concentration. Strong dependence of surface diffusion coefficient on amount adsorbed is partially interpreted in terms of the change of heat of adsorption with surface coverage as determined from separate equilibrium runs.
The sedimentation of coal in model oils: The effect of the viscosity and composition of the oil
Authors: Adams‐Viola Mary , Botsaris G. D. , Glazman Yuli 
Published: June 2004

AbstractThe results of batch settling tests with various coal powders in model oils indicated that the viscosity and the aromatic/paraffinic nature of the oil influences the sedimentation and the aggregation rate of the particles. Oxidation of paraffin oil may result in the generation of surface active agents which retards the sedimentation of certain coals.
Heterogeneous catalytic reactors undergoing chemical deactivation. Part I: Deactivation kinetics and pellet effectiveness
Authors: Lee H. H. , Butt J. B. 
Published: June 2004

AbstractA general expression for the time‐dependence of the activity of a catalyst pellet affected by both chemical deactivation and diffusion is developed. Specific results are given for both uniform and pore‐mouth poisoning, with parallel and series poisoning mechanisms. Comparisons show a satisfactory agreement between theoretical and experimental results. A pellet effectiveness representing the combined effect of deactivation and diffusion is also developed in a form suitable for direct inclusion in reactor conservation equations.
Heterogeneous catalytic reactors undergoing chemical deactivation. Part II. Design and analysis: Approach of reactor point effectiveness
Authors: Lee Hong H. , Butt John B. 
Published: June 2004

AbstractA design method is presented that takes into account the effects of both diffusion and deactivation on hetergeneous catalytic reactors. Improvements that can be made by the method are demonstrated and an efficient methodology is developed by which the design problem as well as associated optimization problems can be solved in a routine manner. The approach is based on the reactor point effectiveness for global rate of reaction in terms of bulk fluid conditions. Some important features emerge from the examples presented.
A new method for on‐line controller tuning
Authors: Yuwana Minta , Seborg Dale E. 
Published: June 2004

AbstractA new method for tuning controllers on‐line has been developed based on a single experimental test, a step change in controller set point. The set‐point response data and analytical formulae are used to calculate model parameters for a first‐order plus time delay transfer function. Controller settings can then be calculated using the model parameters and standard controller tuning relations. Simulation results demonstrate that the new method provides good initial values for PID controller settings despite gross modeling errors and unanticipated load disturbances that may occur during the experimental test.
Multiple‐phase equilibria in hydrates from methane, ethane, propane and water mixtures
Authors: Holder G. D. , Hand J. H. 
Published: June 2004

AbstractPhase‐equilibrium conditions for multicomponent hydrocarbon‐water mixtures were experimentally determined, demonstrating that both structure I and structure II hydrates can form from a single mixture. Model parameters were optimized to allow prediction of the hydrate structure, and prediction of the pressure and temperature of hydrate formation for the experimental mixtures.
Dynamic contact angles
Authors: Gutoff E. B. , Kendrick C. E. 
Published: June 2004

AbstractThe dynamic contact angles of various liquids on a gelatin‐subbed polyester tape were investigated by plunging a tape into a pool of liquid, in the manner of Perry and of Burley and Kennedy. The effect of the upper fluid was studied by replacing the air normally present by immiscible oils. A fair correlation was found at the point of air entrainment, relating the capillary number, μV/σ, to a physical properties number, gμ4/ρσ3. A dimensional correlation, relating the air entrainment velocity to the viscosity to the −0.67 power, was even better. At various velocities, the dynamic contact angle (or the dynamic contact angle minus the static angle) could be related to the capillary number, the physical properties number, and to density and viscosity ratios. Again, the dimensional correlations were better than the dimensionless ones, perhaps caused by an omission of a significant dimensionless group due to our inability to choose a suitable characteristic length.With any one system, the data could be expressed as θ = kN above some minimum velocity, or, covering all velocities, as (θ − θs) = kN. With air as the upper fluid, all the data at one angle lie within one decade, with capillary numbers at air entrainment in the range of 0.6–1.3.
Analysis of vertical pneumatic conveying of solids using multiphase flow models
Authors: Arastoopour Hamid , Lin Shaw‐Chan , Weil S. A. 
Published: June 2004

AbstractThe multiphase flow models were used to predict pressure drop and segregation of particles flowing in a vertical pipe. To compare calculations with data, it was necessary to assume an effective particle size based on a coefficient of restitution and on inlet void fractions. Different partifle size distributions with equal average particle size generate distinctly different pressure drops and segregations. Contribution of solid interaction force is very important in accounting for the segregation of the particles in a vertical pipe.All models gave a reasonable prediction of the design parameters. The pressure drops predicted by the models agreed well with both high‐ and low‐pressure experiments.
Gas transport through polyethylene membranes
Authors: Soles Emma , Smith J. M. , Parrish W. R. 
Published: June 2004

AbstractTransport rates were measured by monitoring the pressure decay between two reservoirs connected by a polyethylene membrane. The diffusion equation was integrated to obtain a relation between the pressure difference across the reservoirs and the time, with solubility, expressed by Henry's law constant H, and the diffusivity D as parameters. A procedure was developed whereby both H and D are evaluated from a single set of Δp vs. t measurements. For argon in low‐density polyethylene, H and D at 323 K were 35[kg·mo]/(m3 of gas)/[kg·mol/(m3 of polymer)] and 2.1 × 10−10 m2/s, respectively. For the high‐density sample these values were 38.7 and 1.11 × 10−10 at 298.1 K.
Analysis of batch, dispersed‐emulsion, separation systems
Authors: Kremesec V. J. , Slattery J. C. 
Published: June 2004

AbstractAn analysis of a batch, dispersed‐emulsion (liquid membrane), separation system results in simple models that describe the concentrations and masses of each phase as functions of time. Comparisons with a limited set of experimental data are offered. One of these models allows a set of pilot studies to be extended to performance predictions and comparative studies of different feed‐membrane‐solvent combinations, which could lead to an optimally designed separation process.
Statistical estimation of parameters in vapor‐liquid equilibrium
Authors: Patino‐Leal Hugo , Reilly P. M. 
Published: June 2004

AbstractA new procedure for the estimation of parameters in two‐component vapor‐liquid equilibrium is presented. It allows for measurement errors in all variables and gives better fits than most other procedures because of the use of two relations between the variables rather than one as is commonly used. An approximate and an exact solution are described and the importance of using all thermodynamic and statistical information is illustrated for the Wilson and UNIQUAC models. New alternatives for analysis of residuals are also discussed.
Multiparameter corresponding‐states correlation of coal‐fluid thermodynamic properties
Authors: Brule M. R. , Lin C. T. , Lee L. L. , Starling K. E. 
Published: June 2004

AbstractA multiparameter corresponding‐states correlation has been developed to describe fossil‐fluid thermodynamic properties needed to design fluid‐flow, heat‐exchange, and other unit operations in coal‐liquefaction plants. Three equation‐of‐state parameters, a molecular‐size/separation parameter, a molecular‐energy parameter, and a molecular‐orientation parameter are used to characterize nonpolar and slightly polar aromatic hydrocarbons. A conformal‐solution model is developed for predicting thermodynamic properties of coal‐derived mixtures.
Kinetics of thermal regeneration reaction of activated carbons used in waste water treatment
Authors: Hashimoto Kenji , Miura Kouichi , Watanabe Tsuneo 
Published: June 2004

AbstractThe kinetics of the thermal regeneration of activated carbons used in the waste water treatment was analyzed on the basis of a model that the regeneration reaction consists of a set of many first‐order reactions each of which has different activation energy and frequency factor. The frequency factors were correlated approximately by a function of the activation energy.The difference in the activation energy was represented by a distribution curve which was obtained by analyzing the thermogravimetric curve (TG curve) measured under a constant heating rate. The weight loss during the regeneration reaction under complicated heating conditions was well predicted by use of the distribution curve determined by the proposed method. This method describing the kinetics of the thermal regeneration may be applied to the design of reactors regenerating spent carbons.
Numerical solution of liquid‐phase multicomponent adsorption in fixed beds
Authors: Mansour Awadh , Von Rosenberg D. U. , Sylvester N. D. 
Published: June 2004

AbstractA generalized mathematical model is developed to describe the process of multicomponent adsorption on activated carbon in fixed beds. Numerical, finite difference, solutions for the adsorption of binary, and ternary organic mixtures are shown to satisfactorily match previously published experimental data.
Diffusivity of urea in concentrated, saturated and supersaturated solutions
Authors: Sorell L. S. , Myerson A. S. 
Published: June 2004

AbstractA relatively simple and extremely versatile optical method of obtaining diffusion coefficient data known as Gouy interferometry was employed to measure diffusion coefficients in undersaturated and supersaturated aqueous urea solutions at 25°C. The use of laser light as a monochromatic light source in the interferometer greatly simplified the procedure for obtaining diffusivity data from the interferometer. A novel design of a real image camera was employed to record the interferometric data. Values obtained from the interferometric data for low concentration (0–4 molar) aqueous urea solutions were within ±5% of literature values.The diffusion coefficient was found to decrease linearly with increasing concentration up to the saturation point of the aqueous urea solutions, and to decrease drastically with increasing concentration in the supersaturated region. This behavior is similar to that observed in liquid‐liquid systems near the consolute point (Cussler, 1980). It is speculated that this phenomenon is a result of molecular aggregation of the urea molecules in supersaturated aqueous solutions. Very little experimental data have previously been obtained in the supersaturated region due to crystallization problems. Supersaturated diffusion coefficient data are important in the study and design of crystallization processes.The solid‐solute‐liquid solvent binary systems urea‐water and sucrose‐water were modeled as a saturated solution solute‐liquid solvent system in order to test various concentration dependent diffusion relationships. Two of these relationships, the Vignes and Leffler‐Cullinan equations, showed improved correlation with experimentally determined diffusivity data for aqueous urea and aqueous sucrose solutions at undersaturated conditions.
An experimental study of floc strength
Authors: Glasgow L. A. , Hsu Jyh Ping 
Published: June 2004

AbstractPhotographic observation of the disintegration of individual flocs upon interaction with a turbulent jet has been used to quantify the binding force of kaolin‐polymer and kaolin‐Fe+III aggregates. The data suggest that the strength per unit mass decreases with increasing floc size, thereby supporting the multiple‐level model for aggregation.