bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass transfer properties of bubble columns suspending immobilized glucose oxidase gel beads for gluconic acid production
Authors: Nakao Katsumi , Harada Tsuyoshi , Furumoto Keiji , Kiefner Andreas , Popovic Milan 
Published: March 2009

AbstractThe volumetric gas‐liquid oxygen transfer coefficient, kL a, and the liquid–solid coefficient, kS, were measured in a 6.7 L external loop airlift bubble column (ELBC), a 2.5 L internal loop airlift (ILBC) and a 2.5 L normal bubble column (NBC) by the steady state method proposed previously using the oxidation of glucose with air catalyzed by glucose oxidase, GO. For an improved and simultaneous determination of kL a and kS, GO was entrapped in calcium alginate gel beads together with fine palladium particles instead of catalase to decompose the hydrogen peroxide produced. The gas holdup, ϵG, in each type of bubble column and the liquid circulation velocity, uL, governing ϵG in the ELBC were also measured to correlate the data on kLa according to the previous correlations proposed for a larger scale of the ELBC, ILBC and NBC. The data on kL a, kS, ϵG and uL (only for the ELBC) in the reaction system were compared to each other for the three types of bubble columns. The results are well predicted by the previous correlations.
Bioremediation of contaminated air using an external‐loop airlift bioreactor
Authors: Wei Vicky Q. , Hill Gordon A. , Macdonald Douglas G. 
Published: March 2009

AbstractBiological air treatment methods are gaining popularity in the chemical industries due to their low cost and ability to convert many hazardous volatile organic compounds (VOCs) into harmless byproducts. An external loop, airlift bioreactor (ELAB) is used to separately bioremediate two prototype, water‐soluble VOC compounds: p‐cresol and ethanol. In both cases, the effluent air was cleansed and bioremediated to below detectable limits (beyond 99.7% removal) due to the efficient scrubbing action of the ELAB. The bioreactor continued to provide this removal efficiency up to maximum air p‐cresol concentration of 0.6 g/m3 and ethanol concentration of 110 g/m3 and at bioreactor loading rates up to 8 g/m3 h for p‐cresol and 220 g/m3 h for ethanol. A dynamic and quasi‐steady state, biokinetic model is shown to predict the transient bioremediation process very well using batch growth biokinetic parameters.
Steady incompressible fluid flow over a bundle of cylinders at moderate reynolds numbers
Authors: Satheesh V. K. , Chhabra Raj P. , Eswaran V. 
Published: March 2009

AbstractThe complete Navier‐Stokes equations describing the steady flow of incompressible Newtonian fluids normal to an array of long cylinders have been solved numerically using the finite difference method in terms of the stream function and vorticity variables. The inter‐cylinder interactions have been mimicked using the well known free surface cell model. Extensive information on the detailed structure of the flow field in terms of the surface vorticity distribution, stagnation pressure, stream line and iso‐vorticity line plots, as well as on the values of the integral quantities, such as pressure, friction and total drag coefficients, have been obtained under wide ranges of conditions as follows: 0.3 ≤ ϵ 0.99 and 0.01 ≤ Re ≤ 100. The numerical results presented herein have been validated using the appropriate theoretical and experimental results available in the literature; the match between the present predictions and the scant experimental results is good.
Modeling the effect of drop charge on coalescence in turbulent liquid—liquid dispersions
Authors: Tobin Thomas , Ramkrishna Doraiswami 
Published: March 2009

AbstractIn this work, a mechanistic model of drop coalescence based upon a stochastic film‐drainage analysis is developed. The coalescence model accounts for previously considered factors, such as turbulence intensity, drop size, and drop deformability, while additionally describing the dual effects of drop surface potential and system electrolyte concentration. Model results indicate that electrostatic repulsion may strongly inhibit small drop coalescence, as well as coalescence between larger deformable drops. Comparison of model predictions to data from several transient coalescence experiments shows good agreement in most cases.
Esterification of ethenyl benzene and its derivatives with acetic acid in the presence of perchloric acid as a catalyst
Authors: Martínez de la Cuesta Pedro J. , Martínez Eloísa Rus , Palomino Pérez Fuensanta I. , Sarria Francisca Romero 
Published: March 2009

AbstractThe esterification process of ethenyl benzene and its derivative compounds (p‐methyl, p‐methoxy, p‐chloro, m‐methyl, m‐nitro and m‐chloro, respectively) was carried out with acetic acid and using perchloric acid as a catalyst. From the effects of the variables studied it could be concluded that: the temperature and the catalyst concentration influence positively over the olefin conversion, whereas the initial olefin concentration exert no effect over the same; and that the presence of perchloric salts exerts a different influence, depending on the temperature and on the catalyst concentration. It has been proven that the substituted radicals in the m‐ or p‐ positions exert an important influence over the conversion of the studied olefins, presenting growing reactivity in the following order: m‐nitro ethenyl benzene, m‐chloro ethenyl benzene, p‐chloro ethenyl benzene, m‐methyl ethenyl benzene, ethenyl benzene, p‐methyl ethenyl benzene and p‐methoxy ethenyl benzene. Finally, a kinetic and thermodynamic study has been done and the corresponding parameters have been calculated, with an adequate fitting.
Microstructural aspects of the flow behaviour in a liquid—solids circulating fluidized bed
Authors: Zheng Ying , Zhu Jing‐Xu (Jesse) 
Published: March 2009

AbstractThe local instantaneous and time‐average suspension densities were determined in a 76 mm diameter by 3 m tall liquid‐solids circulating fluidized bed riser using a fibre‐optic probe. Attempts were made to qualify the microflow structure through statistical analysis of the local bed voidage fluctuations obtained under different operating conditions for the first time. The results show that local microflow structure is uniform in the axial direction but non‐uniform in the radial direction with more flow fluctuation near the wall than in the core of the column for a given axial position. The standard deviation and intermittency index tend to increase with increasing solids circulating rates. Comparing with the gas—solids CFB, the liquid—solids CFB shows much more homogeneous flow structure in both the axial and radial microscopic flow behaviours. The microflow behaviours in the conventional liquid—solids fluidization, liquid—solids circulating fluidization and dilute‐phase liquid transport regimes are also characterized by examining the probability distribution and the intermittency index of the solids holdup.
Modelling FCC units under steady and unsteady state conditions
Authors: Arandes José M. , Azkoiti Miren J. , Bilbao José , de Lasa Hugo I. 
Published: March 2009

AbstractA FCC phenomenological‐based model is presented in this study. This model accounts for the behaviour of the riser, the stripper and the regenerator. Both the reactor and the regenerator are incorporated in the model using detailed reaction kinetics. Catalyst regeneration allows for both catalytic and non‐catalyzed combustion of CO to CO2. Overall, the model is constituted by a set of ordinary differential equations, relatively easy to solve and suitable for steady and unsteady state simulation of FCC units. The proposed model avoids, as much as possible, empirical expressions being suitable for simulation of industrial FCC units and process control studies.
Three‐stage well‐mixed reactor model for a pressurized coal gasifier
Authors: Song B. H. , Watkinson A. Paul 
Published: March 2009

AbstractThree Canadian coals of different rank were gasified with air‐steam mixtures in a 0.1 m diameter spouted bed reactor at pressures to 292 kPa, average bed temperatures varying between 840 and 960°C, and steam‐to‐coal feed ratios between 0.0 and 2.88. In order to analyze gasifier performance and correlate data, a three‐stage model has been developed incorporating instantaneous devolatilization of coal, instantaneous combustion of carbon at the bottom of the bed, and steam/carbon gasification and water gas shift reaction in a single well mixed isothermal stage. The capture of H2S by limestone sorbent injection is also treated. The effects of various assumptions and model parameters on the predictions were investigated. The present model indicates that gasifier performance is mainly controlled by the fast coal devolatilization and char combustion reactions, and the contribution to carbon conversion of the slow char gasification reactions is comparatively small. The incorporation of tar decomposition into the model provides significantly closer predictions of experimental gas composition than is obtained otherwise.
Fractionation of nylon fibres using a vertical settler
Authors: Chen Joyce X. , Masliyah Jacob H. 
Published: March 2009

AbstractBased on theoretical analysis, a continuous vertical settler was found capable of fractionating fibres according to their length. Fractionation experiments confirm the theoretical predictions. Under the extreme dilution used in this study, there was no effect of feed consistency. The performance of fibre fractionation decreased with an increase in the overflow stream flow rate. Fibre fractionation performance improved for a larger fibre diameter. A theoretical model was developed to simulate fractionation in the continuous vertical settler and it agrees fairly well with the experimental results.
Comparaison de deux types d'écoulements (tangentiel plan et tourbillonnaire) dans des modules d'ultrafiltration. Influence de la contrainte pariétale
Authors: Morineau‐Thomas Odile , Lelièvre Caroline , Rossignol Nathalie , Jaouen Pascal , Legentilhomme Patrick 
Published: March 2009

AbstractCette étude est consacrée à l'évaluation des performances d'un nouveau procédé de séparation par membrane constitué d'une cellule annulaire munie d'une entrée tangentielle unique à sa base. Pour cela, nous avons comparé les flux de perméation de ce module, siège d'un écoulement tourbillonnaire non entretenu, à ceux obtenus avec un module à écoulement tangentiel plan classique. L'ultrafiltration de suspensions modèles de bentonite nous a permis de comparer les performances des deux modules pour différentes conditions opératoires. Les influences du débit, du nombre de Reynolds et du gradient pariétal de vitesse à la surface de la membrane ont été étudiées; ce dernier paramètre apparaǐt comme le critère le plus approprié pour mettre en parallèle les deux géométries. En effet, il prend en considération la nature de l'ecoulement et plus particullèrement la contrainte de cisaillement à la surface měme de la membrane qui régit le transfert de solvant au travers de cette dernière. Dans certaines conditions, le module à écoulement tourbillonnaire permet d'atteindre des flux de perméation augmentés de plus de 30% par rapport à ceux obtenus avec un module tangentiel plan classique. L'étude de la consommation énergétique de ces deux cellules permet de confirmer l'intérět des écoulements tourbillonnaires pour la conception de nouvelles géométries de modules de séparation par membrane.
Piloting of anionic polymerization of styrene in tetrahydrofurant
Authors: Saban Marko , Liebermann George , Jay Alex , Shi An‐Chang , Ro Nam , Dale William , Forgione Pat 
Published: March 2009

AbstractAnionic polymerization of styrene in THF with n‐butyllithium/alpha‐methylstyrene initiator is described as a first step in preparation of a styrenic block copoly‐mer. In order to suppress rapid decay of living alpha‐methylstyrene unimers, which occurred at room temperature, the initiation reaction was carried out at −20(+5)°C. The kinetic parameters of this decay reaction were determined and used for process optimization. By combining experiments with modelling of styrene propagation reaction all key process parameters were defined for l‐L, 38‐L, and 189‐L reactors. A good match was demonstrated between the model and experimental propagation exotherm for semibatch reaction conditions. Overall, it was demonstrated that technical grade THF and styrene could be used at pilot plant scale to prepare well‐defined polymers up to Mn 22 000 via the “living” polymerization mechanism. The resulting polymers had narrow molecular weight distributions (1.06 < Mw/Mn < 1.30).
The role of the vapour phase in fluid coker cyclone fouling: Part 1. Coke yields
Authors: Mallory Donald G. , Mehta S. A. (Raj) , Moore R. Gordon , Richardson Susan 
Published: March 2009

AbstractThe cyclone sections of fluid coking reactors at oil sand upgrading facilities have been observed to undergo severe coke fouling during each operational cycle. This work was conducted to determine if vapour phase deposition mechanisms could be responsible for the formations observed in the cyclones. The effects of vapour phase temperature (from 490°C to 560°C) and residence time (from 0.4 to 4.4 s) were studied. Raising the vapour phase temperature above the temperature at which the vapours were derived was found to significantly increase both the yield and rate of production of vapour phase coke.
On the control of an unstable periodic state in the repeated fed‐batch operation of a biochemical system
Authors: Jayant Alok , Subramaniam Pushpavanam 
Published: March 2009

AbstractIn this paper we discuss the proportional feedback control of a repeated fed‐batch reactor around a desired but unstable periodic state. The flow rate in each cycle is assumed to be a constant. The unstable periodic state is determined using a shooting method technique and its stability is found using the Floquet theory. The control action is based on the performance, i.e., biomass concentration, at the end of the cycle. Two choices of the manipulated variable are investigated, i.e., the cycle time and the flow rate. The concentration of the substrate in the feed is assumed to be a constant.
The viscoelastic properties of polymer‐modified asphalts
Authors: Carreau Pierre J. , Bousmina Mosto , Bonniot Frank 
Published: March 2009

AbstractThe linear viscoelastic properties of one family of base asphalts, unmodified or modified by the simple addition of an elastomer or by further in‐situ crosslinking, have been investigated. The time‐temperature superposition principle was shown to be valid for the base as well as for the modified asphalts. The addition of the elastomer styrene‐butadiene (SB) copolymer increased drastically the storage modulus and the elastic character of the asphalts. The thermal susceptibility of the polymer modified asphalts was considerably reduced and this combined with an increased resistance to deformation (larger complex modulus) suggests much better performances for road applications. The chemically modified asphalt containing 3% SB showed similar viscoelastic properties as the physical blend containing 6% SB.
Enrichment of heavy water in flat‐plate thermal diffusion columns of the frazier scheme with the optimal plate aspect ratio for best performance
Authors: Yeh Ho‐Ming 
Published: March 2009

AbstractThe solutions of the optimum plate aspect ratio as well as the corresponding maximum separation, maximum production rate and minimum plate surface area in thermal diffusion columns of the Frazier scheme for enrichment of heavy water have been obtained, analogous to those obtained in the previous work for separation of a binary system. It was found that all the optimum plate aspect ratios do not depend on feed concentration, while the corresponding best performances do. It is found that considerable improvement in performance is obtained when the operation is carried out with the optimal plate aspect ratio.
Deposition of magnetite particles from flowing suspensions under flow‐boiling and single‐phase forced‐convective heat transfer
Authors: Turner Carl W. , Klimas Stan J. 
Published: March 2009

AbstractThe deposition rate of colloidal magnetite particles was measured under both single‐phase forced‐convective and flow‐boiling conditions. All measurements were made at alkaline pH where both the heat transfer surface and the surface of the magnetite particles appear to be negatively charged. For single‐phase forced convection, the deposition rate constant is lower than the mass transfer coefficient for colloidal particles, and the difference is attributed to the force of repulsion between the negatively charged surfaces of the particle and substrate. The deposition rate measured under flow‐boiling conditions is lower than that reported for the deposition of colloidal particles at neutral pH. The difference is, again, attributed to the force of repulsion between the particle and substrate. Particle removal rates were significantly lower than deposition rates; analysis using the theory of turbulent bursts suggests a removal efficiency of only 10−9% for each turbulent burst. The low removal efficiency is consistent with the particle diameter being significantly smaller than the thickness of the laminar sublayer in these tests.
Integral equation study of the residual chemical potential in infinite‐dilution supercritical solutions
Authors: Lotfollahi Mohammad Nader , Modarress Hamid , Mansoori G. Ali 
Published: March 2009

AbstractA new method for solving the integral equation based on the Ornstein‐Zernike equation for binary mixture is proposed. Then the radial distribution function obtained for both the Percus‐Yevick and the hypernetted chain closure equations are used to calculate the residual chemical potential at infinite‐dilution and at reduced temperatures T* = 2, 1.5 (supercritical isotherms) over a varying range of reduced densities ρ* = 0.1 to 0.6 for various types of the Lennard‐Jones mixture in terms of size ratios D and energy ratios C. To examine the ability of the integral equation approach for the residual chemical potential calculations, the results are compared with the Monte‐Carlo simulation data and the van der Waals I results (Shing et al., 1988). It is seen that at ρ* = 0.1 to 0.5, the deviation of the integral equation results from the MC simulation data is less than the reported statistical fluctuation.
The effect of adsorption on mass transfer in fluidized bed catalytic reactors
Authors: Akşahin Inci , Eroĝlu Inci , Yücel Hayrettin 
Published: March 2009

AbstractTracer gas residence time distributions (RTD) in a laboratory scale fluidized bed system have been measured for pulses of three different tracer gases (methane, ethane and propane) at different temperatures in the range 323 to 435 K. The fluidized solid was a commercial zeolite based FCC catalyst (CBZ‐2), and measurements were carried out in a superficial air velocity range of 0.01 to 0.04 m/s. The data were interpreted with two‐phase dense phase dispersion models for adsorptive tracers, available in the literature. In addition, modified models were considered by assuming a stationary dense phase and neglecting axial dispersion in this phase. Mean residence time, μ1, and the variance of the residence time, σ2, of RTD data were calculated for each experimental run. Applying the moment technique in the Laplace domain, the differential equations for all models considered were analytically solved.Mass transfer coefficients obtained from dynamic experiments were compared with the values estimated from the relations available in the literature. It was found that methods considering convective flux alone between the bubble and emulsion phases give closer values to the experimental ones than the methods also including the diffusive flux.
Drag coefficient—reynolds number transition for gas bubbles rising steadily in viscous fluids
Authors: Rodrigue Denis 
Published: March 2009

AbstractRecently, the author (Rodrigue, 2001) developed a generalized correlation for the motion of gas bubbles rising steadily in uncontaminated viscous Newtonian fluids of infinite extent. It is the purpose of this note to show that this model can be written in an explicit form for the drag coefficient as a function of the Reynolds and Morton numbers. This new correlation is then used to predict the position of the minimum in a graphical representation of CD versus Re. It is shown that the model can predict quite nicely this hydrodynamic transition for viscous fluids.
Alkaline hydrolysis of isoamylformate: Effect of dissolved electrolytes on kinetics
Authors: Ghosh Bhaswati , Bhattacharjee Sekhar , Chaudhuri Basab , Mukherjee Dulal C. 
Published: March 2009

AbstractThe kinetics of alkaline hydrolysis of isoamylformate with aqueous solutions of sodium hydroxide and pottassium hydroxide has been determined by using the theory of mass transfer with chemical reaction; the effect of presence of electrolyte salts such as sodium chloride and sodium sulfate in aqueous alkaline solution has been assessed. Experiments have been conducted in a stirred cell having a flat liquid—liquid interface. For the different aqueous phases employed, the alkaline hydrolysis conforms to the fast pseudo‐first order reaction regime. The system is of considerable practical importance and has been successfully employed for the measurement of the interracial area of a flooded packed bed contactor that contained cation exchange resin particles having a diameter of approximately 0.5 mm as packing particles.
Bang‐Bang solution of nonlinear time‐optimal control problems using a semi‐exhaustivesearch
Authors: Gupta Yash P. 
Published: March 2009

AbstractAt times, the objective is to seek a bang‐bang control policy for nonlinear time‐optimal control problems. The usefulness of iterative dynamic programming (IDP) has been shown in the literature for solving such problems. However, the convergence to the optimal solution has been obtained from about 50% of the guessed values near the optimum. In this paper, we present a semiexhaustive search method for seeking such solutions and a comparison is made with the IDP. The results show that the convergence can be obtained from a significantly higher number of guessed values chosen over a much wider region around the optimum.
Experimental study of a reverse flow catalytic converter for a dual fuel engine
Authors: Liu Benlin , Checkel M. David , Hayes Robert E. 
Published: March 2009

AbstractTheperformance of a reverse flow catalytic converter for a methane/diesel dual fuel engine, a monolith honeycomb converter with palladium catalyst washcoat, was evaluated under steady and transient engine conditions. The reverse flow converter provided superior performance (that is, higher conversion of pollutants) for several steady engine operations, compared with unidirectional flow operation. For transient operation following a step change in engine operating conditions, reverse flow is better than unidirectional flow when the change in engine operation results in a reduction in exhaust gas temperature. For an increasing exhaust gas temperature, reverse flow decreased the rate of increase of reactor temperature. The reverse flow converter was tested using the transient Japanese 6‐Mode tests. Reverse flow operation gave higher conversions than unidirectional flow for this test, with a switch time of 5 s giving the best results.