bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model of ceramic membrane fouling during heavy oil ultrafiltration
Authors: Duong Anna , Smith Kevin J. 
Published: March 2009

AbstractFouling of asymmetric, single tube ceramic membranes during ultrafiltration of Cold Lake heavy oil, is described by a pore restriction fouling model that predicts reduced permeate flux but increased asphaltene rejection with increased time‐on‐stream. Application of the model to experimental data showed that a 2nd‐order rate of asphaltene adsorption/deposition within the membrane pores, described the data better than a 1st‐order model. The asphaltene molecular radius, estimated as a parameter of the model, was in the range 3.8 ‐ 14.2 nm, depending on the membrane pore diameter. These values are in good agreement with previously published estimates of asphaltene particle size, determined using different experimental techniques.
Oxidation of low concentrations of hydrogen sulphide: Process optimization and kinetic studies
Authors: Yang Aimin , Tollefson Eric L. , Dalai Ajay K. 
Published: March 2009

AbstractLow concentrations (e.g. < 3) of H2 S in natural gas can be selectively oxidized over an “granular Hydrodarco” activated carbon catalyst to elemental sulphur, water and a small fraction of by‐product sulphur dioxide, SO2. To optimize the H2 S catalytic oxidation process, the process was conducted in the temperature range 125—200 °C, at pressures 230—3200 kPa, with the O/H2 S ratio being varied from 1.05 to 1.20 and using different types of sour and acid gases as feed. The optimum temperature was determined to be approximately 175 °C for high H2 S conversion and low SO2 production with an O/H2 S ratio 1.05 times the stoichiometric ratio. The life of the activated carbon catalyst has been extended by removing heavy hydrocarbons from the feed gas. The process has been performed at elevated pressures to increase H2 S conversion, to maintain it for a longer period and to minimize SO2 production. The process is not impeded by water vapour up to 10 mol% in the feed gas containing low concentrations of CO2 (< 1.0). A decrease in H2 S conversion and an increase in SO2 production were obtained with an increase in water vapour in the feed gas containing a high percentage of CO2. The process works well with “sour natural gas” containing approximately 1% H2 S and with “acid gas” containing both H2 S and CO2. It gives somewhat higher H2 S conversion and low SO2 production with feed gas containing low concentrations of CO2. A kinetics study to determine the rate‐controlling step for the H2 S catalytic oxidation reaction over “granular Hydrodarco” activated carbon has been conducted. It was concluded that either adsorption of O2 or H2 S from the bulk phase onto the catalyst surface is the rate‐controlling step of the H2 S catalytic oxidation reaction.
Modeling infinite dilution activity coefficients of organic‐aqueous systems using a modified regular solution equation and cubic equations‐of‐state
Authors: Bader Mansovr S. H. , Gasem Khalid A. M. 
Published: March 2009

AbstractExpressions derived from the regular solution equation and the generalized cubic equations‐of‐state (EOS) were employed to model the infinite dilute activity coefficient (γ∞) of organic‐aqueous systems. A database of 119 organic species in aqueous systems, divided into six classes, was gathered for models evaluations. The use of the molar density, the first order molecular connectivity, and the dipole moment appear to be adequate correlating variables for describing the structural dependence of the residual part in the modified regular solution equation (MRS). The Soave‐Redlich‐Kwong (SRK) and Peng‐Robinson (PR) were specified and employed in the generalized cubic EOS form. The excess activity coefficient concept was used in the SRK and PR EOS models to account for the deficiency of EOS in dealing with highly non‐ideal or polar systems. The abilities of two existing correlation models along with two modified versions of the UNIFAC model were also assessed. The proposed models provide creditable equations for correlating γ∞ of organic‐aqueous systems.
Rising velocity of a swarm of spherical bubbles in power law fluids at high reynolds numbers
Authors: Chhabra R. P. 
Published: March 2009

AbstractIn this work, a theoretical scheme for estimating the rise velocity of a swarm of spherical bubbles through quiescent power law liquids at high Reynolds number is developed. The inter‐bubble interactions have been accounted for by the use of a cell model. The effect of the power law index and the volume fraction of the gas on the rise velocity is elucidated. Depending upon the degree of shearthinning behaviour and the gas fraction, the swarm may rise slower or faster than a single bubble. This behaviour has been explained qualitatively in terms of two competing mechanisms.
Transient heat transfer in a fixed bed of slab‐shaped and spherical particles with intraparticle conduction
Authors: Sheikholeslami Roya , Watktnson A. Paul 
Published: March 2009

AbstractThe mathematical equations for heat transfer between a flowing fluid and both slab‐shaped and spherical particles with intraparticle conduction in a fixed bed, are numerically solved using the method of lines. The solution for spherical particles was used to confirm previous results for zero and non‐zero Biot numbers. Conditions are identified under which heat transfer to beds of slabs should not be approximated by available solutions for spheres.
Gas‐solid mass transfer in a rotating drum
Authors: Javhari Ritika , Gray Murray R. , Masliyah Jacob H. 
Published: March 2009

AbstractGas‐solid volumetric mass transfer coefficients (kSA) were measured in a rotary drum by evaporation of n‐decane into dry air from the surface of porous solids. The effect of drum rotational speed, N (0.09 to 2.0 min−1), solids volume fraction, η (0.043 to 0.25) and the presence of baffles on kSA were investigated. In the presence of baffles, kSA was independent of ηand higher than in the case of a rolling bed where no baffles were present. For the rolling bed case, kSA increased with increasing η. Mass transfer in the rolling bed was modeled based on the particle motion.
Ethanol‐water pulping: Cooking variables optimization
Authors: Gilarrahz M. A. , Oliet M. , Rodriguez F. , Tijero J. 
Published: March 2009

AbstractThe ethanol‐based pulping of Eucalyptus globulus by the ALCELL® process was studied to determine the optimum cooking conditions. In the first set of experiments the influence of chip size, chip impregnation, liquor‐to‐wood ratio and cooking additives was studied. Once the more convenient values for these variables were established according to kappa number, yield and viscosity, a surface response method was used to determine the influence of cooking temperature, cooking time and ethanol concentration on autocatalyzed pulping process. The developed models indicate that a high screened pulp yield (56%) and acceptable kappa number (23) and viscosity (1030 mL/g) can be obtained when cooking conditions are around 185°C, 110 min and 50% of ethanol.
Non‐isothermal micromixing in turbulent liquids: Theory and experiment
Authors: Baldyga Jerzy , Bourne John R. , Walker Benedikt 
Published: March 2009

AbstractPartial segregation of reagents occurs when reaction rates exceed mixing rates and frequently causes product distributions to be mixing‐dependent. A simultaneous temperature segregation, whereby the temperature in a reaction zone differs from that in its surroundings, has rarely been considered when mixing reagents in the liquid phase. The Prandtl number is usually sufficiently small that engulfment, not thermal conduction, determines the local temperature. The engulfment model of micromixing can then be extended by a heat balance to specify this temperature. To evaluate this model, a new pair of fast competitive reactions (neutralisation and acetal hydrolysis) has been characterised thermochemically and kinetically. A Mettler RC1 calorimeter was operated under isothermal and adiabatic conditions with various stirrer speeds and HCl was slowly added to a mixture of NaOH and 2,2‐dimethoxypropane. Measured hydrolysis yields compared quite well with the extended engulfment model, although temperature segregation was of minor importance. It was also unimportant in other reaction systems (simultaneous neutralisation and ester hydrolysis; diazo coupling) employed earlier to study micromixing. Suggestions for further work are made.
The use of mixing‐sensitive chemical reactions to study mixing in dispersed fibre systems: Adsorption of reactants and product dyes on the dispersed phase
Authors: Mmbaga Joseph P. , Bennington Chad P. J. 
Published: March 2009

AbstractMixing‐sensitive chemical reactions conducted under controlled conditions can be used to qualitatively and quantitatively assess mixing in aqueous systems. These reactions are typically competitive reactions where the distribution of products is used to quantify mixing. This technique is valuable for studying both mixing and local energy dissipation in dispersed systems where the opacity of the suspension prevents the use of other techniques. However, correct interpretation of the test results requires that adsorption of reactants and product dyes on the dispersed phase be known. The adsorption of the reactants and product dyes formed in the mixing‐sensitive azo coupling between mixtures of 1‐ and 2‐ naphthol and diazotized sulfanilic acid was measured in aqueous suspensions of nylon, polyethylene, fibreglass and kraft pulp fibres. The polyethylene fibre did not adsorb the reactants or product dyes. The nylon, fibreglass and kraft fibres adsorbed both reactants and product dyes, with adsorption described by Langmuir isotherms. Accounting for the adsorption of dye on the dispersed phase allowed correct interpretation of mixing in the aqueous phase of the dispersions. This technique is evaluated for mixing assessment in suspensions of nylon fibre and fully bleached kraft (FBK) pulp in a medium‐intensity mixer.
Process viscometry of complex fluids and suspensions with helical ribbon agitators
Authors: La Fuente Edmundo Brito‐De , Nava Jose A. , Lopez Luzmaria , Medina Luis , Ascanio Gabriel , Tanguy Philippe A. 
Published: March 2009

AbstractThe viscosity of highly inelastic shear thinning fluids and aqueous suspensions of kaolin clay particles has been investigated using a helical ribbon impeller fitted to a rheometer. Viscosity data for the single phase non‐Newtonian fluids adequately processed with a generalized Reynolds number based on the impeller tip speed are shown to superimpose very well to the results obtained with a cone and plate rheometer. In the case of the two‐phase system, it is shown that the data treatment for single phase system can be extended. The helical ribbon impeller yields more stable viscosity values than with the traditional geometries and no spurious flow phenomena (i.e., sedimentation, slip at the wall, etc.) was observed, making this system a superior device for suspension rheology over cone and plate and Couette flow rheometers.
Characterization of dispersed hydroprocessing catalysts prepared in reversed micelles
Authors: Hall Andrew G. , Duangchan Apinya , Smith Kevin J. 
Published: March 2009

AbstractFe, Co and Ni particles were prepared in water/polyoxyethylene‐4‐laurylether/n‐hexane and water/polyoxyethylene‐4‐laurylether/decahydronaphthalene microemulsions by reduction of metal nitrates dissolved in the water pools of the reversed micelles. The particles were mostly monodispersed with average diameters in the range 8 to 23 nm, as determined by dynamic light scattering (DLS). However, significantly smaller size estimates were obtained using transmission electron microscopy (TEM). The average DLS particle diameters increased with increased average diameter of the reversed micelles, and the diameter of the reversed micelles increased with an increase in the microemulsion water: surfactant ratio and metal ion concentration. The diameter of the reversed micelles was also dependent upon the metal dissolved in the water pool, increasing in the order Ni < Co < Fe. These trends are explained in terms of changes that occur to the microemulsion hydrophilic‐lipophilic balance. Preparation of nickel and cobalt sulfides by sulfidation of the metal salt with H2S at low temperature, yielded much larger diameter particles (average diameter 75 nm). Measurement of the activity of the sulfided catalysts showed that the Co catalyst was more active than the Ni catalyst for the hydrocracking of diphenylmethane, and Co was more effective than Fe in reducing coke yield during Cold Lake residue hydroprocessing.
Kinetics and extraction of phenol in phase‐transfer catalyzed reaction
Authors: Wu Ho‐Shing , Liu Chien‐Bang 
Published: March 2009

AbstractUnder two‐phase conditions, the feasibility of extracting/removing phenol from aqueous alkaline medium via reaction with allyl bromide dissolved in dichloromethane was investigated using phase‐transfer catalysts in a stirred cell. The effects of the concentrations of base, reactant and catalyst, and temperature were also evaluated to obtain the optimum reaction conditions. According to these results, the extractive efficiency of phenolic substances varied strongly with increasing base concentration. The specific extraction rate, diffusivity, mass transfer coefficient and distribution coefficient of an intermediate product were determined to explain the reaction mechanism by the proposed theoretical model. During reaction, the concentration of the intermediate product in the organic phase was also measured, and a simulation method was used to examine the mass transfer behavior of the intermediate product in the liquid‐liquid system.
Evaluation des dépôts d'aérosols par thermo et diffusiophorèse lors de l'ecoulement dans une conduite cylindrique — applications aux essais tuba diffusiophorèse
Authors: Zoulalian André , Albiol Thierry 
Published: March 2009

AbstractDans l'hypothèse d'un accident sévère sur un réacteur nucléaire à eau pressurisée, les aérosols émis par le coeur du réacteur seront entraînés par un écoulement gazeux constitué de vapeur d'eau et d'incondensables. Dans le circuit primaire et plus précisément au niveau du générateur de vapeur, ces aérosols se déposeront sur la paroi du faisceau tubulaire par thermo et diffusiophorèse. L'analyse des bilans de matière et d'énergie montre que dans le cas d'un écoulement stationnaire dans un tube cylindrique à température de paroi constante, l'efficacité des dépôts d'aérosols par thermo et diffusiophorèse peut être estimée à partir de la connaissance de deux grandeurs thermohydrauliques que sont l'efficacité de condensation et la température moyenne du fluide à la sortie du tube. Les expressions théoriques trouvées permettent de rendre compte de manière satisfaisante des résultats obtenus lors du programme expérimental “Tuba diffusiophorèse” de l'Institut de Protection et de Sûreté Nucléaire. Enfin, l'analyse simultanée des deux types de dépôts est plus représentative qu'une analyse associant de manière indépendante les deux types de dépôt.
Sodium aluminosilicate crystal formation in alkaline solutions relevant to closed cycle kraft pulp mills
Authors: Park Hyeon , Englezos Peter 
Published: March 2009

AbstractMetal ions, such as those of Al, Si, and Ca known as non‐process elements (NPEs), are a major concern in the development of technology for achieving closed cycle operation in Kraft pulp mills. For example, the build‐up of NPEs such as Al and Si ions causes sodium aluminosilicate complex formation in the recovery cycle of Kraft pulp mills. These complexes precipitate on process equipment and are very hard to remove. The purpose of this study is to supply basic data on the precipitation conditions for such complexes. These data can be used to develop process models for design and optimization of closed mills. The precipitation conditions of sodium aluminosilicate complexes in synthetic green and white liquors were determined. In the experiments, the effects of varying the A1/Si ratio and concentrations of OH‐, Na2S, CO32‐, and SO42‐ were studied. The structure of the precipitates was identified by X‐ray diffraction, thermo‐gravimetry and chemical analysis. The precipitates were found to have the structure of hydroxysodalite and/or sodalite.
Control of the product distribution in the hydrogenation of vegetable oils over nickel on silica catalysts
Authors: González‐Marcos M. Pilar , Gutiérrez‐Ortiz José I. , De Elguea Cristina González‐Ortiz , Alvarez Jon I. , González‐Velasco Juan R. 
Published: March 2009

AbstractSeveral nickel on silica catalysts, prepared by impregnation or precipitation/deposition, and a commercial catalyst were tested for activity and selectivity in the sunflower seed oil hydrogenation. An average turn‐over frequency of 2.57 s−1 was found for the catalysts, assuming inaccessibility of nickel in pores smaller than 2 nm and a constant nickel surface concentration poisoned by the reaction mixture. After studying the mass‐transfer steps, the effect of temperature (373‐453 K) and pressure (101‐608 kPa) on reaction rates in the kinetic regime was analyzed, and the corresponding apparent activation energies and reaction orders were obtained. Conclusions on the effect of temperature and pressure on the selectivity to the preferential hydrogenation of polyunsaturates (So) and to the formation of trans‐isomers ((Strans)0) in the kinetic regime were derived from the results. Finally, a similar analysis was carried out when diffusion limitations were known to be present.
Unsteady mass transfer between a slender bubble and a viscous liquid in a simple extensional flow
Authors: Favelukis Moshe 
Published: March 2009

AbstractUnsteady mass transfer between a slender bubble and a viscous Newtonian liquid in a simple extensional and creeping flow has been studied. The exact analytical solution, at large Peclet numbers, has been obtained using similarity transformations and by the method of characteristics. It was determined that when a dimensionless time (the strength of the flow multiplied by the time) is greater than 2, then steady state is, in practice, obtained.
Propriétés rédox de fullerènes fonctionnalisés
Authors: Boudon Corinne , Gisselbrecht Jean‐Paul , Gross Maurice , Thiel Walter , Cardullo Francesca , Seiler Paul , Isaacs Lyle , Nierengarten Jean‐François , Haldimann Richard F. , Diederich François , Mordasini‐Denti Tiziana 
Published: March 2009

AbstractLes propriétés physico‐chimiques du C60 laissent présager son utilisation comme brique élémentaire dans la synthèse de nouveaux matériaux. La fonctionnalisation de fullerènes modifiant ces propriétés, nous avons, pour toute une série de fullerènes hautement fonctionnalisés, étudié les modifications de leurs propriétés physico‐chimiques et plus particulièrement électrochimiques. Cette mise au point rassemble les résultats obtenus lors de nos études électrochimiques de fullerènes C60 mono et poly‐fonctionnalisés de manière covalente. L'objectif est d'analyser les corrélations susceptibles d'exister entre les propriétés rédox des fullerènes et le degré, le motif et la nature de la fonctionnalisation du C60. Pour effectuer cette étude, une série de fullerènes fonctionnalisés sur les positions [6,6] ont été synthétisés. Cette série unique de mono‐ et poly‐adduits permet effectivement l'étude des modifications des propriétés physiques et électrochimiques en fonction du degré, du motif et de la nature de la fonctionnalisation. Les résultats obtenus sont comparés aux données de la littérature.
Gas—liquid mixing studies with multiple up‐ and down‐pumping hydrofoil impellers: Power characteristics and mixing time
Authors: Hari‐Prajitno Danawati , Mishra Ved P. , Takenaka Katsuhide , Bujalski Waldemar , Nienow Alvin W. , Mckemmie Jack 
Published: March 2009

AbstractAxial flow impellers with hydrofoil blades, APV‐B2, i. e., B2‐30 and B2‐45 (30° and 45° angle of attack of blades) have recently been designed, mainly for use in the up‐pumping mode, and some new results are reported here for single, dual and triple impeller configurations in the turbulent flow regime. The results are compared with dual Lightnin' A‐315's pumping downwards as they have traditionally been used and with dual radial flow Rushton turbines. The ungassed power numbers of the APV‐B2's are low, allowing these impellers to be used at large impeller‐to‐tank diameter ratios. The drop in Pg/P is lower with all combinations of APV‐B2 impellers, i. e., for single, dual and triple impellers when compared to other configurations tested. Torque fluctuations are less than those with single or dual down pumping axial hydrofoils. Mixing times measured using a decolourisation technique for dual and triple impeller configurations of APV‐B2 under unaerated and aerated conditions showed that the mixing times are much shorter than those for the dual Rushton turbine and similar to those found for dual down‐pumping A‐315's. Detailed mixing characteristics and flow patterns for the dual and triple APV‐B2's are also discussed.
Catalytic steam pyrolysis of a selected saturated hydrocarbon on calcined mineral particles
Authors: Taralas Georgios 
Published: March 2009

AbstractAt a total pressure of 101.3 kPa, and in the presence of water vapor (P = 32 kPa), the impact of commercially available Norwegian and Swedish quarried mineral rocks on the gaseous product yields and selectivities generated during the catalytic steam pyrolysis of n‐heptane (Pn‐C7H16, = 2.9‐4.7 kPa) in the intermediate temperature range of 973–1073 K and GHSV 1200–4000 h−1 was investigated. The results indicate that the choice of calcined mineral particles as the bed material influences the product distribution of alkenes. In particular, calcined dolomites [CaMg(O)2] suppressed the evolution of unsaturated and aromatic hydrocarbon species; however, the formation of ethylene (C2H4) was correlated. A Langmuir‐Hinshelwood mechanism has also been proposed to describe the rate equation of the vapor‐phase steam pyrolysis of n‐heptane on calcined dolomite at 973 K.
Gas holdup in homogeneous and heterogeneous gas—liquid bubble column reactors
Authors: Sarrafi Amir , Müller‐Steinhagen Hans , Smith John M. , Jamialahmadi Mohammad 
Published: March 2009

AbstractThe velocity‐holdup relationship is the most important design parameter for gas—liquid bubble column reactors, providing the basis for the prediction of heat and mass transfer coefficients and information on hydrodynamic conditions. A summary of the literature on gas holdup in bubble columns is supplemented by new experimental results which extend the data range. A criterion for the gas velocity leading to the transition between homogeneous and heterogeneous regimes for perforated plate gas distributors has been developed. Correlations for gas holdup in both regimes are developed and verified against both new and existing data.
Étude hydrodynamique des lits fluidisés sous vide et sous haute température
Authors: Ruvalcaba J. Ramiro Rodriguez , Caussat Brigitte , Hemati Merhdji , Couderc Jean‐Pierre 
Published: March 2009

AbstractAfter having analyzed the few literature results concerning fluidized beds hydrodynamics under reduced pressure, new theoretical elements are proposed which provide an estimation of the beginning and finishing fluidization velocities. Numerous experimental results(Umfapp, Umb, Ump, ϵmf, ϵmb, ϵmp), obtained at 20 and 500°C, are then presented for several sub‐atmospheric pressures. Finally, f& the first time, at leastto our knowledge, by high frequency recording pressure drops through the bed, the influence of pressure decreases on the hydrodynamics is accurately analyzed.