bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mathematical model for pyrolysis of a solid particle — effects of the heat of reaction
Authors: Miyanami Kei , Fan Liang‐Shih , Fan L. T. , Walawender W. P. 
Published: March 2009

AbstractA transient analysis of the effects of the heat of reaction in a solid pyrolysis system is presented. Two cases, one characterizing the heat‐transfer‐controlled reaction and the other self‐sustaining reaction, are analyzed. To carry out the numerical simulation, utilization is made of the volume reaction model which takes into account the simultaneous heat and mass transfer phenomena, and the method of line which utilizes the second order centered finite difference scheme for the spatial discretization. Effects of the heat of reaction on the solid conversion, solid reactant, and fluid product concentration profiles, temperature distribution, enthalpy, and average fluid product concentration in the particle are examined. The results are graphically presented and interpreted.
Reduced dynamic model of a fixed bed reactor
Authors: Mcgreavy C. , Naim H. M. 
Published: March 2009

AbstractThe solution of dynamic distributed parameter models describing complex highly exothermic reactions in fixed bed reactors usually requires excessive computation times which are too demanding for detailed explorations. A lumping technique has been applied to a dynamic distributed parameter model, in which the radial differential operators have been approximated and effectively replaced by simple algebraic expressions by redefining the dependent variable. The resulting reduced model retains the accuracy of description and the necessary structure which is implicit in the full set of equations. This has been achieved by relating a suitably defined set of pseudoparameters to the chemical and physical processes taking place. The direct benefit of this is that the computation time and storage requirements have been reduced to a more realistic level for design purposes.
Mechanics of a turbulent contact absorber
Authors: Uchida S. , Chang C. S. , Wen C. Y. 
Published: March 2009

AbstractThe operating conditions of a turbulent contact absorber (TCA) can be divided into four regimes. The characteristic behaviour of a TCA in each of the regimes is discussed. The condition below the flooding point is the usual operating regime. Correlations are developed to relate the pressure drop and the liquid holdup of a TCA by the operating variables.A terminal velocity model is developed to explain the flooding condition of a TCA. With this model, the hydrodynamic behavior of the TCA at the flooding point can be identified.The total pressure drop and the pressure drop across a single stage are distinguished to clarify the controversy whether the gas velocity can affect the pressure drop of a TCA. The total pressure drop of a TCA is composed of the pressure drop due to distributor loss at the entrance and the pressure drop of the bed itself. The pressure drop of a single stage bed of a TCA is independent of gas velocity.
Unsteady flow of a micro‐polar fluid between two concentric circular cylinders
Authors: Ramkissoon H. , Majumdar S. R. 
Published: March 2009

AbstractThis paper examines the flow of a micropolar fluid between concentric cylinders in the case where the outer cylinder is held fixed while the inner cylinder is subjected to an arbitrary time dependent angular velocity. Here integral transforms are effectively used to obtain closed form solutions. The special case of a periodic angular velocity is then considered. The results obtained are compared as far as possible with their classical counterparts and some of the physical quantities have been represented graphically. It has been found that, in comparison to classical fluids, an increased couple is experienced by the inner cylinder.
A thermal oscillator for optimization of control
Authors: Tennankore K. N. , Bock H. H. R. 
Published: March 2009

AbstractBock suggested in 1972 a practical measure for the quality of control of a process as the ratio of ‘external disturbance’ to ‘error’ in the system. Optimization of the control of chemical engineering processes according to this measure requires low frequency filters. In this study a low frequency thermal oscillator has been developed by using a brass rod with a heating section at the middle and a sensing section at one end. The frequency response of this system shows that the equivalent pathlength for heat transfer is more than the distance between the heater and the sensor. Feedback oscillations have been obtained with proper circuitry between the sensor and the heater in dicating the possibility of using the system as a low frequency filter for optimizing the control of a process according to Bock's measure for the quality of control. A scheme for the measurement of the quality of control and its maximization is briefly outlined.
Mass transfer by free convection during electrolysis at inclined electrodes
Authors: Patrick M. A. , Wragg A. A. , Pargeter D. M. 
Published: March 2009

AbstractThe limiting electrolysis current technique has been used to obtain experimental measurements of mass transfer in natural convection at rectangular plane plates. Inclinations varying from horizontal down facing to horizontal upfacing at intervals of 10° have been employed with plate height and electrolyte concentration as additional variables. For attached boundary layer flow conditions, all results are well correlated by the equation:Attached flow conditions are obtained for all downfacing inclined orientations the vertical position and for upfacing inclinations where θ (the angle from the vertical) is small. Separation of the flow occurs at higher values of θ in upfacing orientations and is demonstrated by Schlieren photography, as is the existence of longitudinal vortices in the flow. The critical Rayleigh number for separation instability is estimated from the mass transfer measurements and compared with results of other authors.
Foam breaking — key process in detoxification of kraft mill effluents by foam separation
Authors: Ng K. S. , Mueller J. C. , Walden C. C. 
Published: March 2009

AbstractA study was undertaken to demonstrate on pilot plant scale the performance of a turbine foam breaking system and to develop the design parameters for large scale application.Among various configurations a 3‐blade vaned‐disc turbine was found to be optimal for foam breaking. Major process variables controlling foam breaking were system design, tip velocity, rotation speed, and foam load. A foam breaking system with only restricted liquid draw‐off performed 3 ‐ 16 times better than a conventional flow through system. A 38 cm diameter turbine operating at 1800 τ/min (3600 cm/s tip velocity) collapsed up to 1.2 m3/min (42 ft3/min) of foam.Design equations developed for sizing of foam breakers suggest that a 61 cm (2‐ft) diameter 21 kW turbine will collapse 4.7 m3/min of foam. For a 95 × 103m3/d foam separation plant, approximately 12 foam breakers are required. Capital costs are estimated at $108,000.
Control of cross‐direction variations in web forming machines
Authors: Boyle Thomas J. 
Published: March 2009

AbstractWeb forming machines are often fitted with control actuators which can be used to produce uniform web properties across the width of the machine. A formal procedure for setting these actuators is presented. It is based on a linear incremental steady state process model and a quadratic objective function. Quadratic programming is used to determine optimum settings. It is shown that the procedure handles limited range actuators, interaction among actuators, and physical constraints on the pattern of actuation. Computing costs are seen as a potential problem when large numbers of actuators are involved.
Separation of mixed granular solids using the fluidized counter‐current cascade principle
Authors: Beeckmans J. M. , Minh T. 
Published: March 2009

AbstractThe countercurrent gas fluidized cascade is a novel device for separating mixed granular solids. It embodies counter‐current mass exchange principles similar to those used in distillation or liquid‐liquid extraction. Results are reported for the separation of sand and carbon mixtures under total reflux conditions.
Film boiling of mercury droplets
Authors: Baumeister Kenneth J. , Schoessow Glen J. , Chmielewski Charles E. 
Published: March 2009

AbstractVaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting: therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed‐form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.
The leaching of a chalcopyrite concentrate in ammonia
Authors: Reilly Irvine G. , Scott Donald S. 
Published: March 2009

AbstractThe rate of dissolution of a chalcopyrite concentrate was measured in ammoniacal solutions under oxygen pressure for conditions when chemical reaction rate controlled. Temperatures from 50°‐95°C, oxygen pressures to 689 kPa and ammonia concentrations from 2.5 to 7.0 mol/l were investigated. An electrochemical surface reaction model in which the cathodic reduction of oxygen on the solid surface is rate determining satisfactorily predicts experimental behaviour in the range of experimental data. The activation energy for the reaction was found to be 74.1 kJ/mol.
The oxidation of ortho‐xylene on vanadium pentoxide catalysts. I. Transient kinetic measurements
Authors: Wain Wright M. S. , Hoffman T. W. 
Published: March 2009

AbstractThe gas‐phase oxidation of o‐xylene was studied on commercial vanadia oxidation catalysts, one supported on silica the other on titania.Kinetic data were obtained under transient and steady‐state conditions in fixed bed and transported bed reactors. Product distributions and rates of conversion were measured in the temperature range 233°C and 390°C. The transient experiments with these catalyst indicate a dramatic decrease in catalyst activity with time, accompanied by a considerable decrease in selectivity to phthalic anhydride and an increase in selectivity to carbon oxides. These data also provide additional support for a two‐step reaction model.The object of this experimental program is to study the kinetics of oxidation of o‐xylene on vanadium pentoxide catalysts and thereby elucidate the mechanisms of the reaction and some of its characteristics.
Parameters and mechanisms in the solvent extraction of mined athabasca oil sand
Authors: Cormack Donald E. , Kenchington John M. , Phillips Colin R. , Leblanc Patrick J. 
Published: March 2009

AbstractThe efficiency of solvent extraction of bitumen from mined Athabasca oil sands has been studied in laboratory‐scale, batch, stirred vessels. Solvent type, solids concentration, stirrer speed and contact time have been identified as important parameters. A theoretical analysis of the extraction process provides a basis by which the various parameters are assessed in terms of relative overall mass transfer coefficients. However, because the size distribution of the oil sand aggregates is difficult to reproduce, the analysis is limited. Greater reproducibility, and similar quantitative results were obtained for the dissolution of pure bitumen from the bottom of the stirred vessels.It is shown that highly aromatic solvents such as benzene and toluene can dissolve bitumen 3–5 times faster than an essentially alpha tic solvent such as kerosene. There is evidence, however, which indicates that solvent properties other than aromaticity are also important.The data indicate that a minimum stirrer speed must be exceeded before the extraction of oil sand or pure bitumen will proceed at a reasonable rate. Above this minimum rate, the mass transfer coefficient increases linearly with stirrer speed. The solids concentration is also important since the data suggest that a higher efficiency is obtained at higher solids concentrations in the range of solid loadings studied.
Second virial coefficients of polar gases for a four‐parameter model
Authors: Lin Hung‐Huei , Stiel Leonard I. 
Published: March 2009

AbstractThe second virial coefficients of polar gases have been studied for a potential function consisting of the Kihara spherical core potential combined with a preaveraged dipole‐dipole interaction term. The molecular parameters ϵ/κ, ρo, a*, and y of this potential function were determined for ten substances by a nonlinear least squares analysis of experimental second virial coefficients. These molecular parameters were related to the critical constants, acentric factors, and fourth parameters of the substances. The resulting equations reproduced the second virial coefficients to within the accuracy of the data. Comparisons with experimental data for substances not included in the development of the relationships indicated that good agreement can be obtained for polar fluids by the method of this study.
The analysis and design of binary vapour‐liquid equilibrium experiments. Part I: Parameter estimation and consistency tests
Authors: Sutton Thomas L. , Macgregor John F. 
Published: March 2009

AbstractWhen estimating the unknown parameters in semi‐empirical relationships from vapour‐liquid equilibrium experiments, it has been common practice to minimize the sum of squares of some arbitrary function of one or more of the measured variables (x, y, P, T) without regard to the statistical consequences of such a procedure. It is shown that because these arbitrary procedures do not fully account for the errors in all the variables in the functional relationship they can lead to poor parameter estimates when compared to a statistically sound procedure based on maximum likelihood. The analysis of some binary data sets and a simulation study based on one of them are used to demonstrate the kinds of errors that arise.Use of the maximum likelihood method of estimation also aids one in checking the adequacy of the model used, and in testing the consistency of the experimental data. This is accomplished by comparing the deviations between predicted and measured responses with their computed confidence limits.
Analysis of the efficiency of reverse flow cyclones
Authors: Beeckmans J. M. , Kim C. J. 
Published: March 2009

AbstractThe efficiency of a 152 mm cyclone was determined for inlet velocities in the range 6.1 — 15.5 m/s, for particle sizes from 0.6 μm to 4.7 μm, using monodisperse methylene blue‐uranine aerosol particles. The efficiency of a geometrically similar 76 mm cyclone was also measured for a few conditions of inlet velocity and particle size. These data and others were correlated by linear regression analyses on a function of cyclone Stokes number and cyclone Reynolds number. It was concluded that in the range of variables spanned by the experimental data, the flow fields within the cyclones depended on Reynolds number, and hence that contrary to the assumptions of most theoretical models, cyclone efficiency is not exclusively a function of Stokes number.
Water droplet vaporization in humid atmospheres
Authors: Frazier George C. 
Published: March 2009

AbstractDroplet vaporization histories are computed from a semiempirical quasi‐steady model, including natural convection, and compared with the experimental results of Houghton on suspended droplets in the size range of 500 — 1000 μm. This model explains the curvature in the data, and the agreement between theory and experiment is good in most cases, and indicates further, that natural convection effects around water droplets should be negligible for diameters less than a few hundred microns. However, the same model, modified to include the best available form for the forced ventilation factor, consistently under predicts the Duguid and Stampfer observations on 6 — 18 μm, freely falling droplets. It is suggested that this lack of agreement may be due to incipient Brownian motion on the part of these small droplets, which disrupts the surrounding transport film. Additional data in the size range of a few microns are required in order to test and to quantify this hypothesis.
Break‐up of drops and bubbles in stagnant media
Authors: Grace J. R. , Wairegi T. , Brophy J. 
Published: March 2009

AbstractA simple empirical model is developed based on two‐dimensional linearized Rayleigh‐Taylor stability theory to describe the break‐up of drops and bubbles in stagnant fluids. Splitting is predicted to occur if the growth of indentations on the leading edge is rapid enough relative to the rate at which the disturbance is carried around the interface to the equator. Experimental data on maximum stable sizes of drops and bubbles in viscous liquids are presented for eighteen different systems, covering a range much larger than in previous studies. Agreement between the model and experimental results is favourable.
A comprehensive study on co2‐interphase mass transfer in vertical cocurrent and countercurrent gas‐liquid flow
Authors: Deckwer W.‐D. , Adler I. , Zaidi A. 
Published: March 2009

AbstractCocurrent and countercurrent absorption and desorption of CO2 in water was investigated in tall bubble columns (length 440 and 720 cm, diameter 15 and 20 cm, respectively). Operating conditions were applied which provided for high interphase mass transfer rates. Under these circumstances the relative gas holdup varies considerably with axial position whereas the mean bubble diameter measured at two points was found to be approximately constant. The measured data permit the calculation of local values of interfacial areas, superficial gas velocities, and frequency factors for bubble coalescence and break up.A dispersion model which takes into account the hydrostatic head and a variable gas velocity was applied to describe the measured concentration profiles in both phases. If increased mass transfer coefficients at the column bottom and measured local values of the hold up were used a striking agreement between experimental and predicted profiles could be obtained. The findings lead to a more sophisticated picture of the complex behaviour of gas‐liquid dispersions at high interphase mass transfer rates.
Enhancement factors for gas‐absorption with second‐order irreversible chemical reaction
Authors: Wellek R. M. , Brunson R. J. , Law F. H. 
Published: March 2009

AbstractA relatively simple and explicit mathematical expression has been developed for estimating the enhancement factors for mass transfer accompanied by a second‐order irreversible chemical reaction. The development is based on asymptotic characteristics, i.e., limiting solutions, for second‐order enhancement factors. The resulting mathematical relation and other approximate analytical formulations previously presented in the literature have been critically compared with a numerical solution for the diffusion‐reaction process based on film theory.
Gas separation by permeation Part II: Effect of permeate pressure drop and choice of permeate pressure
Authors: Pan C.‐Y. , Habgood H. W. 
Published: March 2009

AbstractCalculation methods for determining pure gas permeabilities and gas separation performance of hollow fiber modules with significant permeate pressure drop inside the fiber are presented. A sequential optimization method for determining the near‐optimum permeate pressures in cascade operation is developed. It is shown that the performance of narrow hollow fiber modules can be significantly affected by the permeate pressure build‐up inside the narrow fiber. For a given module and given recovery there exists an optimum permeate outlet pressure which minimizes the membrane and permeate compression costs. Examples given relate to the recovery of helium from natural gas.
Decomposition of n‐ and iso‐butyl acetates on charcoal
Authors: Pettit Paul J. , Anderson Robert B. 
Published: March 2009

AbstractThe decomposition of n‐butyl acetate on charcoal was studied at 365° and 385°C, and isobutyl acetate at 394° and 419.5°C. Isobutene and acetic acid were the principal products from the iso ester, and n‐butenes and acetic acid from the normal ester. Other primary and secondary reactions exceeded 20% in most experiments. The principal primary product from the normal ester was 1‐butene which isomerized subsequently to 2‐butenes; iso‐butene from the iso ester did not isomerize.For both esters the activity of the charcoal decreased rapidly, the conversion decreasing linearly with time. Linear correlations were used to estimate the conversion at zero time, and data at zero time were used to evaluate constants of a rate equation. Fouling was attributed to reactions of olefins which produced carbonaceous residues.
Estimation of time delay time constant parameters in time, frequency, and laplace domains
Authors: Sundaresan K. R. , Krishnaswamy P. R. 
Published: March 2009

AbstractFour methods are proposed for estimating the dominant time constant and dead time of a given process from a knowledge of its moments, s‐plane, frequency or transient response data. The methods are faster and simpler and, in terms of accuracy and reliabiltiy, are comparable to the time domain least squares procedure for parameter estimation. Applications of the methods are illustrated with the aid of a dispersion model. A comparison is also made with other known techniques to demonstrate the superiority of the suggested methods.
The drag and pressure drops for hydrodynamically suspended cylinders in a vertical tube with and without polymer addition
Authors: Lee S. W. , Latto B. 
Published: March 2009

AbstractThe pressure drops and the suspension velocities for hydrodynamically suspended aluminum and steel cylindrical bodies were measured for a range of aspect ratios (L/d) in a 5 cm vertical plexiglass tube. Four different body‐to‐tube diameter ratios (d/D) from 0.432 to 0.864 were investigated. Both water and drag reducing aqueous polymer solutions of Reten 423* having concentrations in the range 20 to 100 ppm by weight were used.In all cases, the addition of polymer reduced the drag coefficient and the drag coefficient per aspect ratio approached a constant value as (L/d) approaches 14. The available data for cylindrical bodies in vertical pipelines were correlated to obtain semi‐empirical equations relating pressure drops, drag coefficients and suspension velocities.
Kinetics of nitrobenzene hydrogenation using a gel entrapped palladium catalyst
Authors: Tong S. B. , O'Driscoll K. F. , Rempel G. L. 
Published: March 2009

AbstractPalladium metal has been precipitated in a gel formed by the crosslinking polymerization of 2‐hydroxyethylmethacrylate. The metal particles were found to have an average size of 14 nm. The dried polymer gel contained 1.38% Pd; it was crushed and sieved to give gel particles ca 200 μm in size. When the gel containing Pd was swollen by a solvent, catalytic activity toward the quantitative hydrogenation of nitrobenezene to aniline was observed. A detailed study of the kinetics of this hydrogenation revealed that at 101 kPa pressure and 31°C, resistance to the reaction was approximately equally divided between extra‐particle mass transfer and the chemical activity of the Pd. The high activity of this novel catalyst is attributed to the large surface of the Pd and the extensive swelling of the gel by the reaction medium.