bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transient modeling of a catalytic converter to reduce nitric oxide in automobile exhaust
Authors: Ferguson Noble B. , Finlayson Bruce A. 
Published: June 2004

AbstractMathematical models are developed to study the catalytic reduction of nitric oxide contained in automobile exhaust in which the temperature, flow rate, and concentrations of various species vary widely with time. The quasi‐static approximation is compared to the fully dynamic model. In the quasi‐static model all processes are steady state except for the solid temperature and inlet conditions. Suggestions are given for deciding a priori if the quasi‐static model is appropriate. Suggestions are also given for integrating the quasi‐static equations in order to minimize errors compared to the dynamic model. The performance of three different catalysts is examined with the mathematical model, when the inlet conditions correspond to typical values of temperature, flow rate, and concentration when the automobile is operated according to the Federal Test Procedure.
Absorption in packed towers with concurrent upward flow
Authors: Specchia Vito , Sicardi Silvio , Gianetto Agostino 
Published: June 2004

AbstractIn a previous paper hydrodynamic conditions, interfacial areas and mass transfer coefficients in a packed tower with concurrent downward flows were measured. In this work a packed column with concurrent upward flow has been examined.The results show greater area and liquid mass transfer coefficient values than with downward flow. In concurrent upward flow the increase of power consumption was less than proportional to the mass transfer increase.The experimental data show some factors which affect the increase of area and of the liquid mass transfer coefficient.Energy correlations of mass transfer parameters were proposed.
Intraparticle mass transport in liquid‐filled pores
Authors: Komiyama Hiroshi , Smith J. M. 
Published: June 2004

AbstractAdsorption rate data were measured at 25° to 75°C for benzaldehyde on polymeric, porous Amberlite particles. When the benzaldehyde is dissolved in methanol, the adsorption capacity is very low. Data for methanol solutions gave reasonable values for intraparticle diffusivities based solely on transport in the pore volume. For adsorption from aqueous solution (where the adsorption capacity was high), the contribution of surface diffusion was important.From the two sets of data it was possible to evaluate average effective surface diffusivities by using a model based upon both pore‐volume and surface transport. These values were about 10−8 cm2/s and were sufficiently sensitive to temperature to give activation energies of 7 to 9 k cal/mole.For the more hydrophobic Amberlite, XAD‐4, surface transport was many times as large as pore‐volume diffusion.
Analysis and optimization of the Williams‐Otto process by geometric programming
Authors: Rijckaert M. J. , Martens X. M. 
Published: June 2004

AbstractThis paper applies the principles of geometric programming to the optimization of the well‐known Williams‐Otto process. Following the trend of the articles published on this subject, two different objective functions are considered and the results are compared to those of other investigators.The dual geometric program is used to provide an answer to the question of why the optimal value of the objective function remains unchanged for perturbations in a certain variable.
Joule‐Thomson coefficients of argon‐carbon dioxide mixtures
Authors: Strakey Joseph P. , Bennett Carroll O. , Dodge Barnett F. 
Published: June 2004

AbstractAdiabatic Joule‐Thomson coefficients are presented for argon and two argon‐carbon dioxide mixtures (46.4% CO2and 75.4% CO2) in the single‐phase part of the range: −120 <T<110°C,P< 190 atm. Results are analyzed in terms of the virial equation (including terms to account for the quadrupole moment of CO2), several forms of the Redlich‐Kwong equation, and the Benedict‐Webb‐Rubin equation. In general, the best results were obtained by the Redlich‐Kwong equation as modified by Barner et al. (1966).
Three‐phase equilibria using equations of state
Authors: Heidemann Robert A. 
Published: June 2004

AbstractIt is demonstrated that a single equation of state may be used to describe all three phases in liquid‐liquid‐vapor equilibrium situations. Wilson's version of the Redlich‐Kwong equation is shown to predict accurately the water solubility in normal paraffins with interaction parameters k12 = 0.50. A simple procedure for three‐phase flash computations is presented. Results obtained using this procedure for the system methane, n‐butane, water exhibit many of the characteristics of the experimental data of McKetta and Katz (1948). In particular, the water content of the vapor phase and the liquid hydrocarbon phase are accurately predicted.
Synthesis of distillation systems with energy integration
Authors: Rathore Ram N. S. , Vanwormer Kenneth A. , Powers Gary J. 
Published: June 2004

AbstractA formal method is described for the synthesis of multicomponent distillation systems when energy integration is considered between streams both within the separation sequence and in other parts of the process. The pressure in each column is considered as an optimization variable for both the energy integration and column sizing computations. Four rules are used to enumerate all feasible energy matches between the streams associated with the distillation columns. A bounding strategy which uses both upper and lower bounds is combined with dynamic programming to synthesize the optimal distillation sequence with energy integration. A five‐component separation problem demonstrates the effectiveness of the methods.
Single particle studies of binary and ternary cation exchange kinetics
Authors: Bajpai R. K. , Gupta A. K. , Rao M. Gopala 
Published: June 2004

AbstractExtensive ternary ion‐exchange rate data for cases where particle‐diffusion is important are presented. Experimental rate data, using a single‐particle radioactive‐tracer technique, were obtained for the following systems in Dowex 50W‐X8 resin: Mn‐Cs‐Na, Ba‐Mn‐Na, and Sr‐Mn‐Cs. Nernst‐Planck equations have been used to describe the ternary ion‐exchange kinetics. The Nernst‐Planck model, when used for the correlation of binary and various types of ternary exchange data obtained under unfavorable equilibrium conditions, usually cannot afford to disregard liquid‐film resistance. The model incorporating the film effects correlated satisfactorily most of the experimental data, and even in cases where the correlation was not good, it interpreted adequately the trend of the results.
Relative contribution of variables affecting the reaction in fluid bed contactors
Authors: Miyauchi Terukatsu , Furusaki Shintaro 
Published: June 2004

AbstractSimplified expressions to calculate the extent of reaction in a fluid bed show good agreement with the experimental data of Lewis et al. (1959) and Swaay and Zuiderweg (1972). The contribution of the dilute phase seems more important than that of the jetting zone or reaction factor (Hatta number) in usual fluid bed operations. The effect of the dilute phase is discussed. It is profitable to use the dilute phase for the consecutive isothermal and endothermic reaction, but unprofitable for the exothermic reaction. These characteristics depend upon the nature of reactions and careful considerations as to the choice of the gas velocity, particle characteristics, and reactor design will be necessary.
Solubilities of gases in high‐boiling hydrocarbon solvents
Authors: Chappelow C. C. , Prausnitz J. M. 
Published: June 2004

AbstractLow‐pressure solubilities of methane, ethane, propane, n‐butane, iso‐butane, and hydrogen have been measured in n‐hexadecane, n‐eicosane, squalane, bicyclohexyl, octamethylcyclotetrasiloxane, diphenylmethane, and 1‐methylnaphthalene over the temperature range 25° to 200°C. The accuracy of these measurements is better than 1%. The data for the hydrocarbon gases have been correlated with a generalized configurational entropy and a van Laar‐type interaction parameter. The entropic component of that parameter is related to the free volume of the solvent as suggested by Flory's equation‐of‐state theory of fluid mixtures. The accuracy of the correlation is about ±15%.
Effect of London forces upon the rate of deposition of Brownian particles
Authors: Prieve Dennis C. , Ruckenstein Eli 
Published: June 2004

AbstractRates of deposition of particles onto a spherical collector, immersed in a creeping fluid, are calculated as a function of Peclet number, aspect ratio, and the ratio of Hamaker's constant to kT for all cases of practical importance involving convective‐diffusion and London forces. Boundaries of regions where London forces or Brownian motion may be neglected are established in terms of the above dimensionless groups. Gravitational forces were included in the calculations for some representative conditions but may be neglected for small or neutrally buoyant particles or for high flow rates.Close agreement was noted between deposition rates calculated by summing individual contributions from each transport mechanism and deposition rates calculated from a rigorous consideration of their combined effect. Thus the additivity rule was verified for the cases studied.
Vapor‐liquid equilibrium: Part III. Data reduction with precise expressions for GE
Authors: Abbott M. M. , Van Ness H. C. 
Published: June 2004

AbstractThrough an empirical but rational appraoch to the development of equations to represent the composition dependence of the excess Gibbs function for binary liquid systems, it has been found possible to correlate VLE data precisely, even for highly nonideal systems. This makes possible the application of Barker's method to the reduction of VLE data on a routine basis. The validity of the method is demonstrated through application to several sets of data from the literature, and new experimental data are presented for six diverse binary systems in vapor‐liquid equilibrium at 50°C.
Membranes with common ion pumping
Authors: Caracciolo Frank , Cussler E. L. , Evans D. Fennell 
Published: June 2004

AbstractLiquid membranes containing a macrocyclic polyether can move or pump a specific cation against its concentration gradient. The cation flux is not proportional to the difference of the cation concentration but to the difference of the product of cation and anion concentrations across the membrane. The results are inconsistent with existing theories of ion transport, but can be explained in terms of ion pairs.
Onset of fluidization and slugging in beds of uniform particles
Authors: Broadhurst T. E. , Becker H. A. 
Published: June 2004

AbstractA comprehensive investigation has been made of the boundaries of the regime of bubbling aggregative fluidization. Experiments were done with sand, glass beads, clover seed, and iron shot fluidized with helium, air, and freon‐12 in columns 2.5, 5, 10, and 21 cm in diameter. Bed heights ranged from 1 to 60 column diameters, particle diameters from 0.07 to 1.1 mm, particle densities from 1300 to 7600 kg/m3, and gas densities from 0.17 to 5.2 kg/m3. Correlations are presented for the void fraction at the minimum bubbling point and for the superficial fluid velocity at the points of minimum fluidization, minimum bubbling, and minimum slugging.
A comparison of theoretical predictions with published experimental measurements on the blown film process
Authors: Petrie C. J. S. 
Published: June 2004

AbstractThe equations governing the shape and velocity of the polymer melt in the bubble blowing part of the blown film process are derived for non‐isothermal Newtonian and isothermal elastic material behavior. Measured bubble shapes (Ast, 1973; Farber, 1973) can be reproduced quite well, lying between elastic and viscous predictions. Velocity and strain rate predictions appear more sensitive to details of temperature profile and melt rheology. The results also include bubble pressure predictions or equivalently apparent viscosities for bubble blowing. The main lines of development suggested are the modeling of heat transfer and the use of a viscoelastic constitutive equation.
Contact nucleation of various crystal types
Authors: Tai C. Y. , McCabe W. L. , Rousseau R. W. 
Published: June 2004

AbstractThe purpose of this study was to investigate contact nucleation for various types of crystalline materials. Selected were aqueous solutions of two hydrated inorganic salts (MgSO4 · 7H2O and KAl(SO4)2 · 12H2O), one nonhydrated inorganic salt (K2SO4) and one organic substance (citric acid). Nucleation data were determined as number of nuclei generated per contact as a function of supersaturation and impact energy. Both of these variables strongly influenced the number of nuclei generated per contact. These data show that crystal growth and contact nucleation are related, with more rapidly growing substances giving higher yields of nuclei.
Particle‐gas dispersion effects in confined coaxial jets
Authors: Hedman Paul O. , Smoot L. Douglas 
Published: June 2004

AbstractThe objective of this study was to determine the mixing characteristics of two‐phase, confined, coaxial jets. Gas composition, gas velocity, and particle mass flux radial profiles were obtained at different axial stations using 20% by weight of 6 or 30 μm spherical aluminum particles in the primary stream. Additional tests were conducted without particles. Radial profiles for gas composition, velocity, and particle flux were correlated using the principle of similarity. In the gas phase, mass mixed more rapidly than momentum, and the 6 μm particles mixed less rapidly than mass or momentum. Systems with low primary density and low secondary velocity mixed most rapidly. An implicit numerical model was developed to predict the rate of mixing of the gas/particle mixture. The model included coupled dynamic and thermal nonequilibrium effects between the gas and solid phases. Comparisons of model predictions and experimental results were good.
On the statistical sensitivity analysis of models for chemical kinetics
Authors: Atherton R. W. , Schainker R. B. , Ducot E. R. 
Published: June 2004

AbstractThe differential equations governing the propagation in time of the sensitivity matrix for a mathematical model given by a system of ordinary differential equations are derived. These equations are used to perform a statistical sensitivity analysis of models for chemical reactors. The behavior of the sensitivities at equilibrium is analyzed. It is shown that the sensitivity equations for linear kinetics may be solved using an analytic representation. The numerical solution of these equations is discussed, and illustrative examples are presented. The lognormal distribution is presented as being representative of errors in rate constants.
Analysis of the high pressure polyethylene tubular reactor with axial mixing
Authors: Agrawal Satish , Han Chang Dae 
Published: June 2004

AbstractA theoretical study was carried out for the analysis of the high pressure polyethylene tubular reactor with axial mixing (TRAM). In the study, the Contraction Mapping Theorem in the square‐integrable function space L2[0, 1] was first used to derive a uniqueness criterion for the existence of the steady state solution of the polyethylene TRAM. Then, an algorithm was derived which enabled us to compute the profiles of reactor temperature and concentration. Details of reactor performance were investigated in terms of the reactor operating and design variables: heat transfer coefficient, feed temperature and concentration, axial mixing, the length of reactor, and the distribution of preheating and cooling zones of the reactor. Also investigated in this study was the product quality in terms of the number‐average molecular weight and molecular weight distribution as affected by change in reactor operating conditions and by the chain transfer reactions.
Temperature excursions in catalytic monoliths
Authors: Hegedus L. Louis 
Published: June 2004

AbstractThe application of monolithic catalysts to automotive emission control has frequently been complicated by unexplained thermal degradation phenomena. This paper reports experimental and theoretical studies aimed at the understanding of how heat is generated and distributed in catalytic monoliths during an exothermal, mass transfer limited reaction.Theoretical considerations indicate that under certain operating conditions the steady state solid catalyst temperature can exceed the adiabatic reaction temperature. It is also shown that the catalyst overtemperature is influenced by the nature of the reactive species and by the geometry of the catalyst. These predictions have been verified by experiments in a novel tubular reactor.
Experimental investigation of models for fluidized bed catalytic reactors
Authors: Fryer Colin , Potter Owen E. 
Published: June 2004

AbstractThe countercurrent backmixing model of a fluidized bed reactor predicts axial concentration profiles quite different from those suggested by simple two‐phase models. The models can also be distinguished in terms of the dependence of conversion on operating variables.An experimental study of ozone decomposition in a reactor of 22.9 cm diameter has provided extensive data for comparison with backmixing and two‐phase models which incorporate bubble size variation. The measured profiles show a minimum concentration within the bed at gas velocities above a critical value, as predicted only by the backmixing model. The effect of operating variables on the shape of the profiles is also well accounted for by this model. The backmixing model is further supported by good agreement between predicted and measured reactant conversion. In particular, the variation of conversion with rate constant and gas velocity is fitted more accurately by the backmixing model than by two‐phase models.
Heat transfer and curing in polymer reaction molding
Authors: Broyer Ephriam , Macosko Christopher W. 
Published: June 2004

AbstractA theoretical model is proposed for curing in polymer reaction molding operations like casting, potting, lamination, thermoset molding, or reaction injection molding. In many cases, convection and mass diffusion can be neglected. The resulting unsteady heat equation with temperature dependent generation is solved numerically. Temperature and property profiles, gel point, sol fraction, and modulus are presented for a typical urethane system under several conditions. Two dimensionless groups, the adiabatic temperature rise and the ratio of polymerization rate to heat conduction rate, are most significant. Process design criteria are discussed.
Fluid and particle entrainment into vertical jets in fluidized beds
Authors: Merry J. M. D. 
Published: June 2004

AbstractThe flow of particles and fluid in the vicinity of vertical jets in fluidized beds was studied by using a two‐dimensional bed of lead shot fluidized by water. It was found that both interstitial fluid and solid particles are entrained into the jet as it expands and penetrates into the bed. An approximate mathematical model is developed to describe the particle and fluid flow fields observed experimentally; from this, an expression is derived for rates of entrainment into vertical jets in fluidized beds, and a model is postulated for the flow fields around grid jets.
The role of n‐butane in hydrate formation
Authors: Ng Heng‐Joo , Robinson Donald B. 
Published: June 2004

AbstractThe role of n‐butane in the formation of hydrates has been a matter of some uncertainty. The experimental measurements resulting from this work have shown conclusively that n‐butane does enter the hydrate lattice when hydrates are formed in the presence of methane at pressures from about 1 000 to 10 000 kPa over a temperature range from 0° to about 13°C. At higher pressures and temperatures, n‐butane ceases to enter the crystal and behaves like a nonhydrate former.
A flow model for gas movement in spouted beds
Authors: Lim C. J. , Mathur K. B. 
Published: June 2004

AbstractA two‐region model of a spouted bed, postulating vertical plug flow of gas in the spout and dispersed plug flow along curved streamlines in the annulus, is proposed. The extent of axial dispersion is accounted for by a coefficient D which is an adjustable parameter of the model. Experimental support for the theory is provided by residence time‐distribution data obtained by using helium gas as tracer, covering a wide range of conditions. Values of the coefficient D, determined from a comparison between predicted and observed RTD curves, are generally higher than those reported for packed beds but much smaller than those for fluidized beds.
The modeling of hematite reduction with hydrogen plus carbon monoxide mixtures: Part I. The behavior of single pellets
Authors: Tsay Q. T. , Ray W. H. , Szekely Julian 
Published: June 2004

AbstractOn the assumption of shrinking core behavior, a mathematical model was developed for representing the reduction of hematite disks with a mixture of hydrogen and carbon monoxide. In the model, experimentally measured values were used for the porosity, and the effective pore diffusivities were calculated from pseudo binary formulas. Literature data were used for the activation energies of the reactions, while the preexponential factors were obtained by data fitting. The model was found to provide a good means for representing experimental measurements of Szekely and El‐Tawil (1976), both with regards to the effect of temperature and gas composition.
Studies in chemical process design and synthesis: III. A Simple and practical approach to the optimal synthesis of heat exchanger networks
Authors: Nishida N. , Liu Y. A. , Lapidus Leon 
Published: June 2004

AbstractAn algorithmic‐evolutionary approach to the systematic synthesis of minimum cost networks of exchangers, heaters, and coolers is proposed. The new approach is easy to apply by hand calculations, requiring no special mathematical background and computational skill from the user. In addition to generating many cheaper networks for sample problems ranging in size from 4 to 10 streams as compared to previous studies, the proposed method provides an explicit theoretical guidance on the optimal exchange among hot and cold streams and on the optimal locations of heating and cooling utilities in the network. It also has a provision for the use of stream splitting and for generating a cyclic network. The new method is particularly effective in the synthesis of minimum cost networks for industrial crude unit preheat recovery.
Methanol, past, present, and speculation on the future
Authors: Stiles Alvin B. 
Published: June 2004

AbstractMethanol is overviewed from the standpoint of history: how the history relates to the present and how it could relate to the future. The overview includes ingredients (fuels, catalysts, etc.), synthesis gas generating procedures, processing techniques, and equipment and other considerations for the present and the near and more distant term future.
Statistical analysis of material balance of a chemical reactor
Authors: Madron Frantisěk , Veverka Vladimir , Vaněček Vojtěch 
Published: June 2004

AbstractA method is suggested for a complex statistical treatment of the material balance of a chemical reactor, based on the stoichiometric characteristics of reactions taking place in the reactor. Statistically adjusted values of the balance variables are obtained, and the hypothesis that the material balance data do not contain gross errors is tested. The calculation procedure is demonstrated by an illustrative example of the material balance of a fermentation process.
Distillation with secondary reflux and vaporization: A comparative evaluation
Authors: Mah R. S. H. , Nicholas J. J. , Wodnik R. B. 
Published: June 2004

AbstractA novel distillation scheme which makes use of secondary reflux and vaporization to enhance thermal efficiency is presented. Low operating temperatures, close boiling mixture, and tight product specifications appear to favor this scheme over the conventional distillation. Computer simulation indicates a potential utility reduction of 50 to 75%.