bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pyrite oxidation in aqueous ferric chloride
Authors: King W. E. , Perlmutter D. D. 
Published: June 2004

AbstractThe rate of pyrite oxidation in aqueous ferric chloride was determined for two distinct solid particle systems: industrial grade pyrite and coal particles containing pyrite. The oxidation rate for the pyrite particle system was found to increase significantly with increasing temperature (40° to 100°C), ferric chloride concentration (0.1 and 1.0 M), and pyrite loading (2 to 20 g/l); the rate decreased with increasing particle size (−325 to 140 mesh). Agitation did not have a significant effect, and a kinetic model was developed and fit to the experimental data.For the coal particle system used in this study, the most important variable was particle size. The oxidation rate of pyrite in coal smaller than 325 mesh was much greater than in larger coal particles. The effect of temperature (80° to 100°C) on the oxidation of pyrite in coal was not significant, nor was the effect of pretreatment with 0.1N hydrochloric acid. Approximately half of the detected ferric iron reduction was attributable to pyrite oxidation; the balance arises from other coal reactions.
Experimental study of eddy diffusion model for heated turbulent free jets
Authors: Kataoka Kunio , Takami Tohru 
Published: June 2004

AbstractPrandtl's eddy diffusion model was successfully extended to turbulent momentum, energy, and mass transfer in nonisothermal free jets by taking into account the effect of change in volume of traveling eddies. The present model was experimentally confirmed for the high temperature, low velocity, turbulent free jets produced by combustion of methane gas.
Evaluation of parameters for nonlinear thermodynamic models
Authors: Anderson T. F. , Abrams D. S. , Grens E. A. 
Published: June 2004

AbstractA method based on the maximum likelihood principle has been developed for the determination of model parameters from experimental data when all the measured variables are subject to error. In addition to the best estimates of the parameters, this method also yields information useful in selection of appropriate models and evaluation of the accuracy of the data. Application of the method is illustrated in the reduction of binary vapor‐liquid equilibrium data.
Adsorption rate on molecular sieving carbon by chromatography
Authors: Chihara Kazuyuki , Suzuki Motoyuki , Kawazoe Kunitaro 
Published: June 2004

AbstractDiffusivities in the micropore and adsorption equilibrium constants were determined for neon, argon, krypton, xenon, nitrogen, methane, ethylene, ethane, propylene, propane, n‐butane, and benzene on molecular sieving carbon by chromatographic measurement and moment analysis. Isosteric heat of adsorption was found to be 2.6 times heat of vaporization for the gases examined here. Two separate linear relations were obtained between activation energies of diffusion in micropore and isosteric heats of adsorption for rare gases, methane, and benzene, and for n‐paraffin and n‐olefin except methane.
The mixing of solids in slugging gas fluidized beds
Authors: Thiel William J. , Potter Owen E. 
Published: June 2004

AbstractMeasurements have been made of axial solids mixing in fluidized beds of 0.05, 0.1, and 0.22 m diameter with a variety of materials at atmospheric pressure. Round nosed slugs, raining slugs, and turbulent bubbling have been investigated. Raining slugs occur with coarser materials. With cracking catalyst round nosed slugs form readily in the smaller diameter beds, but in the largest bed, breakdown to the turbulent state was normal. A model has been developed to predict the axial solids mixing in a slugging fluidized bed containing round nosed slugs. The model supposes that each slug is followed by a well‐mixed wake and a piston flow region. The model predicts well the scale effect noted by W. G. May. Axial mixing is fast for round nosed slugs, falls for turbulent bubbling, and is low for raining slugs.
Convective mass transfer in the presence of polarizing fields: Dispersion in hollow fiber electropolarization chromatography
Authors: Reis Joaquim F. G. , Ramkrishna Doraiswamy , Lightfoot Edwin N. 
Published: June 2004

AbstractAn effective means is developed for describing two‐dimensional convective dispersion in the presence of polarizing fields. Explicit results are given for planar fields applied across Poiseuille flows, and these are used to characterize hollow fiber electropolarization chromatography (EPC).
Influence of polymer additives on the gas‐liquid mass transfer in stirred tanks
Authors: Ranade V. R. , Ulbrecht J. J. 
Published: June 2004

AbstractThe influence of polymer additives upon the gas‐liquid mass transfer in stirred tanks is examined. While the addition of sodium carboxymethyl‐cellulose brings about a reduction of the overall liquid side mass transport coefficient which is in line with the predictions by earlier works, the reduction ofkLain polyacrylamide solutions of equal viscosity is much stronger. This is explained by the viscoelasticity of the PAA solutions, and an empirical correlation is proposed.
Relaxation oscillations in chemical reactors
Authors: Gilles E. D. , Eigenberger Gerhart , Ruppel Wilhelm 
Published: June 2004

AbstractThis paper deals with a particular type of limit cycle in chemical reaction systems, the so‐called relaxation oscillation. This phenomenon can be caused by thermal or kinetically induced instabilities in a loop reactor or a CSTR, but can also occur in a catalytic fixed‐bed reactor for an endothermic reaction with self‐inhibiting or self‐accelerating steps.
Cold flow mixing rates with recirculation for pulverized coal reactors
Authors: Tice Christopher L. , Smoot L. Douglas 
Published: June 2004

AbstractThe mixing of particles and gases in confined, coaxial jets in the presence of recirculation was studied. Particle and gas mixing rates were measured for conditions simulating processes involving pulverized coal combustion and entrained gasification. The effects of mixing chamber diameter, gas velocity, particle size, and particle loading level on mixing rates were determined from particle mass flux and gas tracer measurements. In every case, the gas mixed much faster than did the particles. Introduction of an expanded mixing chamber of larger diameter (with recirculation zone) significantly increased both gas and particle mixing rates over that for a smaller mixing chamber without recirculation. However, this observed increase was not strongly dependent upon the diameter of the larger mixing chamber. Increasing secondary velocity also increased mixing rates significantly.
Magnetically enhanced thermal convection in oxygen gas
Authors: Honeywell W. I. , Vevai J. E. 
Published: June 2004

AbstractThe effects of static magnetic fields on heat transfer in oxygen gas have been measured at temperatures between 78 and 112°K and pressures between 2.01 and 4.77 kN/m2. After the data are corrected for ordinary thermal conductivity behavior, comparison with theory suggests that the phenomenon is magnetically enhanced thermal convection.
Heat transfer in plane Couette flow with additional pressure gradient including entrance effects for a non‐Newtonian fluid
Authors: Mitwally Essam M. 
Published: June 2004

AbstractAnalytical solutions are presented for laminar plane Couette flow of a power law non‐Newtonian fluid. Effects of an additional negative pressure gradient were included in solving for the velocity distribution. The contributions due to the entrance heating region and the viscous dissipation effects were included in arriving at the temperature distribution and also the variation of the local Nusselt number at the stationary plate.
A model for short residence time hydropyrolysis of single coal particles
Authors: Russel William B. , Saville Dudley A. , Greene Marvin I. 
Published: June 2004

AbstractThe chemical reactions and mass transfer processes occurring within a single coal particle during high temperature hydropyrolysis are described mathematically and the model is tested using extant experimental data. A significant feature of the model is the treatment of bulk flow due to the evolution of volatiles and the resulting balance between diffusion, bulk flow, and chemical reaction. Predictions of the variations in conversion due to changes in total pressure, hydrogen partial pressure, and particle size agree quantitatively with experimental data.
Annular two‐phase flow of gases and non‐Newtonian liquids
Authors: Eisenberg Fred G. , Weinberger Charles B. 
Published: June 2004

AbstractTwo‐phase, annular flow of gases and non‐Newtonian liquids through horizontal pipes is modeled, and a prediction method for pressure drop and gas volume fraction is proposed. The prediction method consists of a modification, based upon shear rate dependence of the apparent viscosity of the liquid phase, of Lockhart‐Martinelli correlations for Newtonian liquids. The model applies to the case of laminar flow of the annular liquid film. Experimental data, obtained with several aqueous polymer solutions and air, agree closely with predicted values of pressure drop and void fraction.
Infinite dilution volatilities of polar solutes in hydrocarbons
Authors: Won K. W. 
Published: June 2004

AbstractInfinite dilution volatility data have been correlated for alcohols, esters, aldehydes, ketones, and sulfur containing hydrocarbon solutes in aliphatic hydrocarbon solvents over a wide temperature range using a temperature dependent energy parameter for the pure solute.When a polar solute molecule is surrounded entirely by nonpolar molecules, polar molecular interactions such as hydrogen bonding do not play an important role. Therefore, a single, pure solute parameter is sufficient for correlation.Calculated heats of solution at infinite dilution agree well with published calorimetric data.
Simulation of the dynamic behavior of deep bed filters
Authors: Tien Chi , Turian Raffi M. , Pendse Hemant 
Published: June 2004

AbstractA simulation procedure for predicting the dynamic behavior of a deep bed filter over the entire practicable range of filter operation is developed. The method is based on synthesizing available quantitative results relating to filtration, and to porous media flows, within an overall framework which views the process to consist of two principal stages dominated by appropriate limiting deposition modes. Evaluation of the results through comparison with available data indicates, to the extent the nature of these types of data permits, that the method is surprisingly effective and even capable of predicting on satisfactorily quantitative basis some intricate details of observed filter behavior.
The simulation of binary adsorption in continuous countercurrent operation and a comparison with other operating modes
Authors: Liapis A. I. , Rippin D. W. T. 
Published: June 2004

AbstractSimulation studies are presented of three different modes of operating a two‐component adsorption system. The efficiency with which an activated carbon adsorbent is utilized is compared for a single fixed bed, a periodic countercurrent system in which the adsorbent is equally distributed over two, four, and six beds and a continuous countercurrent system. The carbon utilization in the single fixed bed was shown to be one third to one half of that in a continuous countercurrent adsorber of the same length, whereas the periodic countercurrent system achieved a utilization of 79 to 98% of that in the continuous system.The mathematical models used to describe the three different modes of column operation include the effects of axial diffusion in the columns, mass transfer resistance in the boundary layer surrounding each particle, and fluid diffusion within the porous particles.
Mixing with helical ribbon agitators: Part II. Newtonian Fluids
Authors: Patterson W. Ian , Carreau P. J. , Yap C. Y. 
Published: June 2004

AbstractOf necessity, the mixing process is sometimes restricted to the laminar regime, although turbulent mixing is generally more desirable. Common examples of laminar mixing are found when the fluid has a very high viscosity, or when one of the mixture components is shear sensitive. It has been pointed out that the helical ribbon agitator (HRA) is admirably suited to the low Reynolds number mixing process. This work derives a model to predict the power consumption of the HRA. The model has been developed with the aid of experimental data and tested extensively using literature data. For a wide range of mixer geometries and sizes, it predicts power consumption with an average deviation of 13%.The concept of relative efficiency of mixers is also described as an aid to comparing different HRA mixer geometries. Finally, the problem of scale‐up of different HRA configurations is discussed.
Analysis of solid‐solid reactions: A review
Authors: Tamhankar S. S. , Doraiswamy L. K. 
Published: June 2004

AbstractThis paper reviews some important aspects of the analysis of solid‐solid reactions which include: fundamental considerations, experimental techniques, analysis of pellet‐pellet reactions, analysis of mixed powder reactions, role of the gas phase, and reactor design. Illustrations are given wherever necessary. Examples of industrial applications, important systems studied, and the models used are tabulated.
Efficient single‐jet mixing in turbulent tube flow
Authors: Forney L. J. , Kwon T. C. 
Published: June 2004

AbstractA similarity law is proposed to provide effective jet penetration and mixing of a tracer in turbulent tube flow. The scaling law is derived from approximate solutions to the equations of motion for the case of a single, fully developed turbulent jet issuing normally to the flow. Jet properties are correlated with experimental measurements on a methane tracer.
Hot wire measurement in the interacting two‐plane parallel jets
Authors: Yuu Shinichi , Shimoda Fumio , Jotaki Tomosada 
Published: June 2004

AbstractThis study presents the data of turbulence properties in the two‐plane parallel air jets which merge as they issue into still surroundings. These turbulent properties (time averaged and root mean square velocities, Eulerian auto and cross correlation coefficients, various scales of turbulence, energy spectra, and probability density functions of fluctuating velocities) were measured in both the converging and combined regions of the jets by using the X array, hot wire anemometers.The negative high shear stress existed in the merging region. Strictly speaking, the turbulent flow in this region is not isotropic. In the combined region, the turbulent mechanics of these jets are essentially the same as that of the single plane jet. All of the spectra in these jets had a slope of 5/3 over about one decade of the wave number space. The probability density functions were Gaussian except for the boundary to the surrounding air.
Absorption of carbon dioxide into aqueous monoethanolamine solutions
Authors: Hikita Haruo , Asai Satoru , Katsu Yoshio , Ikuno Seiichi 
Published: June 2004

AbstractThe rates of absorption of pure carbon dioxide into aqueous monoethanolamine solutions with a surface active agent were measured at 15°, 25°, 35°, and 45°C in a liquid jet column and a wetted wall column. Experimental results were analyzed with the chemical absorption theory based on the penetration model. Physical solubility of carbon dioxide in aqueous monoethanolamine solutions was determined from the absorption rates measured in a near pseudo first‐order reaction regime and was shown to be considerably larger than the physical solubility in water. The measured absorption rates were in good agreement with the theoretical predictions for gas absorption with an irreversible second‐order reaction, when the variation of the physical solubility of carbon dioxide due to the change in the composition of the solution during the absorption process was taken into account.
Calcium silicates: A new class of highly regenerative sorbents for hot gas desulfurization
Authors: Yang Ralph T. , Shen Ming‐Shing 
Published: June 2004

AbstractA study has been conducted on the utilization of calcium silicates and the silica supported lime as regenerative sorbents for desulfurization of hot combustion gases. Except for γ‐Ca2SiO4 and Ca3SiO5, all the calcium silicates and the silica supported calcium oxide are equally or more reactive than calcium oxide, and the regeneration rates of these sorbents are substantially higher than that of calcium oxide. There was no tendency of decaying of the reactivity after eight cycles of sorption and regeneration.
Drag coefficient and relative velocity in bubbly, droplet or particulate flows
Authors: Ishii Mamoru , Zuber Novak 
Published: June 2004

AbstractDrag coefficient and relative motion correlations for dispersed two‐phase flows of bubbles, drops, and particles were developed from simple similarity criteria and a mixture viscosity model. The results are compared with a number of experimental data, and satisfactory agreements are obtained at wide ranges of the particle concentration and Reynolds number. Characteristics differences between fluid particle systems and solid particle systems at higher Reynolds numbers or at higher concentration regimes were successfully predicted by the model. Results showed that the drag law in various dispersed two‐phase flows could be put on a general and unified base by the present method.
Electroforced sedimentation of thick clay suspensions in consolidation region
Authors: Shirato Mompei , Aragaki Tsutomu , Manabe Akira , Takeuchi Nobuhiko 
Published: June 2004

AbstractIt is shown that the slow settling rates of thickened Gairome clay slurries, when initial concentrations are sufficiently concentrated for settling due to the so‐called consolidation mechanism from the beginning of settling, can be greatly enhanced by application of D.C. voltages. Equations for settling due to the consolidation mechanism are developed in view of the influence of the gravitational and the applied electric field. It is demonstrated that the settling rates increase remarkably with increasing electric field intensity. The settling rates and the porosity distributions in settling sediments calculated by the new equations compare favorably with experimental observations.
Multivariable controller design for linear systems having multiple time delays
Authors: Ogunnaike B. A. , Ray W. H. 
Published: June 2004

AbstractA multivariable, multidelay compensator, capable of handling general, linear time delay problems is derived in a form applicable both in continuous and discrete time. The controller developed is shown to have the same structure as the linear‐quadratic optimal feedback controller for input delays and reduces to the Smith predictor (and the analytical predictor) for the special case of a single time delay. Some examples representative of engineering practice are used to demonstrate the effectiveness of the controller.
Forced convective boiling in vertical tubes for saturated pure components and binary mixtures
Authors: Bennett Douglas L. , Chen John C. 
Published: June 2004

AbstractOver 1000 sets of data for forced convective boiling of distilled water, ethylene glycol and aqueous mixtures of ethylene glycol are reported. Most of these data were taken in the annular flow regime. These data indicate a previously unrecognized Prandtl number effect on the boiling heat transfer for both pure components and mixtures. A significant reduction in the heat transfer coefficient is observed for mixtures attributable to mass transfer effects. An expression is developed which accounts for both of these effects and correlates the experimental data to within a mean deviation of 14.9%. This correlation reduces to the standard Chen correlation for pure fluids with Prandtl numbers close to unity.
Identification and linear multivariable control in an absorption‐desorption pilot plant
Authors: Albrecht J. J. , Kershenbaum L. S. , Pyle D. L. 
Published: June 2004

AbstractA study of the identification of the dynamics of a pilot scale absorption‐desorption system and the subsequent design of a multivariable control scheme are reported. A multivariable transfer function model was obtained from experimental input‐output data in which the inputs (steam supply and liquid circulation rate) were perturbed simultaneously using uncorrelated pseudo random sequences. A two‐step, least‐squares estimator was employed for the identification of the model.A multivariable controller was then designed on the basis of the direct Nyquist array method. The implementation of the controller design indicated the utility of the design procedure as compared to independent single input, single output control loops; there is, however, some scope for additional tuning.
Viscous heat generation in slit flow
Authors: Ybarra Robert M. , Eckert Roger E. 
Published: June 2004

AbstractThe onset of significant departure from isothermality caused by viscous energy dissipation in flow through a slit is determined for isothermal and adiabatic walls. A series solution of the energy equation enables calculation of dimensionless profiles for any power law fluid. Such solutions provide useful standards for judging performances of numerical schemes for solving complex nonisothermal flows.
Fundamental investigations and electrochemical engineering aspects concerning an advanced concept for alkaline water electrolysis
Authors: Fischer Juergen , Hofmann Hans , Luft Gerhard , Wendt Hartmnt 
Published: June 2004

AbstractA thorough search for electrocatalysts for anodic oxygen evolution from caustic potash solution together with an investigation for the main reasons of ohmic potential drops in the interelectrode gap has lead to a new concept for an advanced medium temperature (150° to 200°C), medium pressure (30 to 100 bars) alkaline water electrolysis. The new concept will allow electrolytic water decomposition at temperatures between 160° and 200°C with current densities of 1 to 1.5 A/cm2 and cell voltages between 1.55 and 1.65 V.
Dynamics of mixed cultures of microorganisms: Some topological considerations
Authors: Stephanopoulos Gregory 
Published: June 2004

AbstractStructural relationships between the numbers of the various types of steady states exhibited by a mixed culture of microorganisms growing in a chemostat have been obtained. The analysis is based on the degree theory and utilizes Hopf's index theorem. Useful information concerning the culture growth and general conclusions pertaining to the nature of the possible steady states are obtained from these relationships. An alternate method of stability analysis, based on the above results, has also been developed and applications to several cases of growth of indirectly interacting populations which demonstrate the efficiency of the method are presented.
Optimal sensor location with an application to a packed bed tubular reactor
Authors: Harris T. J. , Macgregor J. F. , Wright J. D. 
Published: June 2004

AbstractA number of approaches to the optimal selection of sensor locations are presented, and some of these are applied to determine optimal thermocouple positions in a packed bed tubular reactor. As expected, the optimal locations were found to be those surrounding the hot spot location. The theory also revealed that for good state estimation and for goodlinear quadratic control of the reactor, only one or two well located temperature measurements are necessary rather than the entire temperature profile.
Substrate‐inhibited kinetics with catalyst deactivation in an isothermal CSTR. II. Multiple pseudosteady states and reactor failure
Authors: Do Duong D. , Weiland Ralph H. 
Published: June 2004

AbstractAnalytical expressions are derived for the time and magnitude of failure of an isothermal CSTR with substrate‐inhibited kinetics, caused by slow catalyst deactivation under three types of parallel and series mechanisms. Reactors operating at high space velocity are found to be most susceptible to early failure and poisoning by product is more dangerous than by reactant. The magnitude of the jump across steady states depends solely on the Langmuir‐Hinshelwood kinetic parameters and a detailed analysis of reactor behavior during the jump itself is given.