bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modélisation et simulation du séchage en continu des couches minces par rayonnement infrarouge
Authors: Cote Benoit , Broadbent Arthur D. , Therien Normand 
Published: March 2009

AbstractBasé sur des concepts de transferts simultanés de masse et d'énergie, un modèle différentiel est posé pour le séchage en continu des couches minces par rayonnement infrarouge. Des essais conduits sur le séchage d'une nappe de coton non‐mercerisé dans un séchoir semi‐industriel d'une capacité maximale de 20 kW ont servi à la calibration du modèle. Les simulations, par intégration numérique des bilans de masse et d'énergie, fournissent les conditions à la sortie du séchoir: température de l'air, température du tissu et degré d'humidité résiduelle dans la nappe. Une étude de sensibilité indique que la température des émetteurs infrarouges est le paramètre qui influence le plus significativement le séchage. Les résultats montrent également que l'air alimenté sert presqu'uniquement à évacuer la vapeur produite, le transfert de chaleur par convection étant faible par rapport au rayonnement.
Correlations for prediction of molecular diffusivities in liquids at infinite dilution
Authors: Wong C. F. , Hayduk W. 
Published: March 2009

AbstractDiffusivities measured at 278.2 K to 323.2 K are reported for propene in acetic acid, acetone, n‐butanol, chloroben‐zene, N, N dimethyl formamide, ethyl acetate and n‐octane. Measurements were made utilizing the steady‐state capil‐lary cell method. It was found that the diffusivities were reduced in the associating solvents when compared with those obtained in non‐polar solvents at the same temperature. Three new empirical correlations have been developed for the prediction of diffusivities in liquids at infinite dilution and these are: for n‐alkane solutions, for dissolved gases in organic solvents, and for dissolved gases in water.
Process control: An overview and personal perspective
Authors: Fisher D. Grant 
Published: March 2009

AbstractThis paper presents an overview and personnal perspective on recent developments and current practice in computer process model. The basic concepts behind conventional process control are reviewed to provide a starting point for the non‐control specialist and process engineer. The ensuing sections on Internal Model Control (IMC), Model Predictive Control (MPC) and adaptive control illustrate the evolution of control technology from the traditional multiloop strategies to the modern, multivariable, model‐based, computer control systems now being used in industry. The paper does not provide a complete, critical review of process control. However, the discussion and the recommended references should provide a good starting point for anyone wanting to become familiar with current practice and some of the new directions of process control.
Feedback control of crystal size distribution in a continuous cooling crystallizer
Authors: Rohani S. , Paine K. 
Published: March 2009

AbstractControl of crystal size distribution (CSD) in a 21.8 L continuous cooling KCl crystallizer was attempted. Feed saturated at 54°C with potash, nearly saturated with NaCl and containing 0.75 g MgSO4/100 g of H2 O was cooled to the crystallizer temperature at 40°C. The control scheme consisted of a proportional‐integral controller with the rate of fines dissolution/removal as the input variable and the fines suspension density (crystals smaller than 150 μm) as the output variable. The measured/controlled variable was a temperature difference, ΔT, corresponding to the temperature of a slurry sample containing representative fines, before and after the fines were dissolved by heating. An increase in the product weight‐mean crystal size and a decrease in the coefficient of variation of product were observed in the controlled runs.
Experimental studies on heat transfer with phase change on diverging‐converging surfaces
Authors: Chakravarty T. K. , Narayanan C. M. , Bhattacharyya B. C. 
Published: March 2009

AbstractAttempts have been made to study experimentally condensation of pure vapours on the inside surfaces of vertical diverging‐converging tubes. The work highlights the significant augmentation in heat transfer efficiency achievable in film condensation on surfaces that are of diverging‐converging geometry. The dependence of the augmentation phenomena on the geometric characteristics of the heat transfer surface, such as angle of constriction and number of segments in series, and also on the operating parameters such as fluid flow rate and fluid inlet temperature, is also discussed.
Mathematical modelling of protein diffusion in microcapsules: A comparison with experimental results
Authors: Kwok W. Y. , Kiparissides C. , Yuet P. , Harris T. J. , Goosen M. F. A. 
Published: March 2009

AbstractThe objective of this study was to develop a general diffusion model for describing mass transport phenomena and membrane diffusivities in alginate—polylysine (PLL) microcapsules. Good agreement between calculated and experimental protein concentration profiles was obtained based on a microcapsule model, consisting of a capsule membrane containing a partially impermeable alginate gel core with a decreasing gel pore size towards the centre of the capsule. The apparent size of the impermeable gel core and the capsule membrane permeability were directly dependent on the size of the diffusing protein and the alginate‐PLL reaction time. The presence of this impermeable core may hinder the commercial and clinical use of these microcapsules in cell culture engineering and cell transplantation by affecting cell viability.
Animal cell bioreactors — recent advances and challenges to scale‐up
Authors: Hu Wei‐Shou , Peshwa Madhusudan V. 
Published: March 2009

AbstractThe demand for animal cell derived products has stimulated the development of bioreactors in the last decade. Most of those developments allow a higher cell concentration to be achieved in the bioreactor than in the past, primarily by means of the continuous flow of culture medium and a mechanism of cell retention. The advantages and technological challenges of some of these developments are discussed. Lagging behind the bioreactor developments is the strategy for culture operation and optimization. The need for suitable kinetic models to describe animal cell growth is emphasized.
Adaptive neural models for on‐line prediction in fermentation
Authors: Van Breusegem Vincent , Thibault Jules , Chéruy Arlette 
Published: March 2009

AbstractThis paper deals with on‐line prediction of fermentation variables by neural network techniques. It is shown that the accuracy of the on‐line prediction based on a neural model, obtained from an initial learning sequence, decreases when kinetic changes occur during the course of the fermentation. Therefore, sliding window learning schemes are proposed. For a given network structure, the proposed learning procedures progressively refresh the knowledge integrated within an initial neural model. The influence of the length of the learning window, the number of iterations and the initial neural model on the predictive accuracy of adaptive neural models are investigated. Sliding window learning schemes can be also used when fermentation measurements are delayed and/or infrequent.
Suspension codeposition in electrowinning cells: The role of hydrodynamics
Authors: Graydon J. W. , Kirk D. W. 
Published: March 2009

AbstractElectrolytic codeposition of particles suspended in a plating bath constitutes a novel method for producing certain alloys. The suitability of this approach for the manufacture of copper‐phosphorus alloy from a suspension of red phosphorus in acid copper sulphate solution was assessed in a scaled, full‐depth, transparent electrowinning cell operated continuously. The suspension was maintained both by the jetting of recirculated electrolyte and by the natural flows of electrolyte and anodic bubbles. Smooth thick deposits of copper containing acceptably uniform, optimal levels of phosphorus were produced. The vertical variation of phosphorus in the cathode is explained by a detailed consideration of hydrodynamic flow near the cathode.
An application of a cascaded self tuning regulator to a karr solvent extraction column
Authors: Camvrdan M. C. , Taylor P. A. , Baird M. H. I. 
Published: March 2009

AbstractAn application of a cascaded Clarke‐Gawthrop self tuning regulator (STR) to a Karr liquid‐liquid solvent extraction column is presented. The Karr column, a reciprocating plate column, exhibits nonlinear asymmetric responses which are complex functions of the operating conditions and requires adaptive control in order to prevent instability. The outer loop of this cascade scheme controls the extract concentration of the continuous phase while the inner loop controls the hydrodynamic holdup in the column and prevents flooding. The manipulated variable was the frequency of reciprocation. The STR‐STR cascade arrangement is compared with a fixed parameter Proportional plus Integral (PI) controller in the outer loop and an STR in the inner loop.
Bulk polymerization in tubular reactors I. Experimental observations on fouling
Authors: Cunningham M. F. , O'Driscoll K. F. , Mahabadi H. K. 
Published: March 2009

AbstractConditions under which fouling (polymer deposition) occurs in tubular polymerization reactors were studied using bulk methyl methacrylate polymerizations at 70°. It was demonstrated that reactor orientation and flow direction have a significant effect on fouling behaviour. Natural convection becomes increasingly important as concentration gradients in the reactor increase. Using the optimum reactor configuration determined in the first part of the study, a feasible operating region for the reactor was established, thereby permitting selection of conditions which will prevent reactor fouling.
The influence of aluminum alkyls on the polymerization of ethylene with SiO2/MgCl2‐supported TiCl4 catalysts
Authors: Lynch David T. , Jejelowo M. Olukayode , Wanke Sieghard E. 
Published: March 2009

AbstractThe influence of different aluminum alkyls (diethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri‐n‐hexylaluminum, tri‐n‐octylaluminum and isoprenylaluminum) on the ethylene polymerization activity of a laboratory prepared high‐activity SiO2/MgCl2‐supported TiCl4 catalyst has been investigated. A slurry reactor (decane diluent) was used for measuring rates of polymerization. The average molar mass, the breadth of the molar mass distribution, the polymerization activity, and the shapes of the activity‐time profiles, were strongly dependent on the nature of the aluminum alkyl. For several of the cocatalysts used, the catalytic activity approached a constant value after a certain amount of time under reaction conditions. In this constant activity region, a first‐order dependence of the polymerization rate on the monomer concentration was found for all of the systems examined. However, the activation energy of the polymerization reaction was found to depend strongly on the type of cocatalyst which was used.
CO2 gasification kinetics of two alberta coal chars
Authors: Kovacik G. , Chambers A. , Özüm B. 
Published: March 2009

AbstractCO2 gasification kinetics of chars from two Alberta coals (Obed Mountain, high volatile bituminous and Highvale, subbituminous) have been studied using a thermogravimetric analyzer (TGA) and a fixed bed reactor. Charification and gasification reactions were performed sequentially in both the TGA instrument and in the fixed bed reactor to simulate real gasifier operating conditions. TGA and fixed bed data were processed numerically to evaluate the kinetic rate of CO2 gasification of the chars. Calculated gasification kinetics could be correlated using both the volume reaction and the grain models. Activation energies of the kinetic rate constants were near 200 kJ/mol for both Highvale and Obed Mountain coal chars using the TGA data. The activation energies calculated for the Obed Mountain coal char using the fixed bed reactor were about 250 kJ/mol. For all the cases studied the calculated activation energies were nearly the same for both the volume and grain reaction models.
Modelling of circulating fluidized bed combustion of a char
Authors: Arena Umberto , Malandrino Alberto , Massimilla Leopoldo 
Published: March 2009

AbstractThe combustion of a char in the 41 mm ID riser of a laboratory circulating fluidized bed combustor has been investigated at different air excesses and rates of solids (char and sand) circulating in the loop. Riser performance was characterized by an axial oxygen concentration profile as well as by the overall carbon content and particle size distribution. The proposed model accounts for carbon surface reaction, intraparticle and external diffusion, and attrition. External diffusion effects were relevant in the riser dense region where char was potentially entrapped in large clusters of inert solids. Experimental data and results of the model calculations are in satisfactory agreement.
A fluidized bed membrane reactor for the steam reforming of methane
Authors: Adris A. M. , Elnashaie S. S. E. H. , Hughes R. 
Published: March 2009

AbstractIn the present investigation a realistic two‐phase model accounting for the change in the total number of moles accompanying the reaction is utilized to explore a novel reactor configuration suggested for the methane steam reforming process. The suggested design is basically a fluidized bed reactor equipped with a bundle of membrane tubes. These tubes remove the main product, hydrogen, from the reacting gas mixture and drive the reaction beyond its thermodynamic equilibrium. The proposed novel design is also equipped with sodium heat pipes which act as a thermal flux transformer to provide the large amount of heat needed by the endothermic reaction through a relatively small heat transfer surface, assuring better reactor compactness. Two options for fluid routing through the membrane tubes are proposed; each is suitable for a certain industrial application. The performance of this novel configuration is compared with that of an industrial fixed bed steam reformer and the comparison shows the potential advantages of the suggested configuration.
Kinetics of desulfurization of hydrogen sulfide using metallic copper as a desulfurizer
Authors: Chen Qiyuan , Li Lili , Hepler Loren G. 
Published: March 2009

AbstractThe kinetics of desulfurization of hydrogen sulfide, using metallic copper as desulfurizer, have been investigated over a range of temperatures and pressures of hydrogen sulfide. Our results indicate that there are two stages of reaction; activation energies for the first and second stages are 63 kJ/mol and 38 kJ/mol, respectively. Possible reaction mechanisms in which the initial rate is controlled by interface reaction and the later stage is controlled by diffusion through or in the Cu2S layer are consistent with the experimental data.
Axial mixing and mass transfer in a vibrating perforated plate extraction column
Authors: Baird M. H. I. , Rao N. V. Rama , Vijayan S. 
Published: March 2009

AbstractThe axial mixing and countercurrent mass transfer characteristics of a 5 cm diameter extraction column agitated by vibrating perforated Teflon plates have been investigated. The dispersed phase was an organic liquid (usually kerosene) and the continuous phase was water. Axial mixing was measured in both phases using pulse tracer techniques; in the continuous phase the axial mixing was estimated to have a significant effect on mass transfer, but axial mixing in the dispersed phase had a negligible effect. Mass transfer was measured for several different solutes; n‐butyric acid, benzoic acid and phenol. The overall heights of a transfer unit (cont. phase) were in the order of 10‐20 cm for the organic‐acids but higher for transfer of phenol from very dilute solutions. The characteristics of the vibrating plate column have been compared with those of other types of extractor and suggestions are made for further development.
Modeling and application of a semibatch coaxial two‐impinging‐stream contactor for dissolution of solids
Authors: Tamir Abraham , Glitzenstein Azar 
Published: March 2009

AbstractA semibatch, coaxial, two‐impinging‐stream (TIS) contactor was developed and tested for dissolving solid particles of sodium‐nitrate, sodium‐nitrite and urea in water. The feature of the contractor lies in the possibility of increasing and controlling the mean residence time of the particles in the reactor.The mass transfer coefficients determined in the semibatch device, where the water was in a continuous flow and the particles remained in the reactor for a certain period of time, can also be applied to a continuous TIS device. The comparison of mass transfer coefficients with values of other well‐known devices indicated that they are among the highest and that the present contactor is very effective.A physical model was established for the behaviour of the dissolving particles which yielded a two‐parameter correlation for predicting the Sherwood number as a function of the operational parameters.
Absorption of carbon dioxide in alkanolamines in the presence of fine activated carbon particles
Authors: Saha A. K. , Bandyopadhyay S. S. , Biswas A. K. 
Published: March 2009

AbstractThe rates of absorption of CO2 into water and 0.1 kmol/m3 aqueous solutions of MEA, DEA and AMP were measured in a stirred cell with a flat gas‐liquid interface in the presence of fine activated carbon particles. Experiments showed that the rates of absorption increased significantly with increases in the loading of activated carbon up to about 6 kg/m3 and thereafter remained constant.
Hydrogenation activity of an amorphous Pd‐Zr alloy held in an alumina matrix
Authors: Takahashi Takeshige , Abe Kazumasa , Kai Takami , Kimura Hisamichi , Masumoto Takeshi 
Published: March 2009

AbstractThe hydrogenation of benzene has been carried out over a catalyst prepared from an amorphous Pd‐Zr alloy held in an alumina matrix. The catalytic activity was compared with that over the alloy cut into 1 mm fragments. It was found that the fixed alloy in the alumina had not only higher catalytic activity, but also a smaller catalyst fouling rate than the fragments of the alloy.The effect of palladium content in the amorphous alloy on the hydrogenation activity was examined. It was found that the initial activity increased with the fraction of palladium. However, the activity of the catalyst which had the highest palladium content decreased with repeated regeneration and reaction, whereas the activity of the other catalysts reached a stable value.
Minimum fluid flowrate, pressure drop and stability of a conical spouted bed
Authors: Povrenovié D. S. , Hadžismajlovié Dž E. , Grbavčić Ž B. , Vuković D. V. , Littman H. 
Published: March 2009

AbstractA model for calculating the minimum spouting flowrate and pressure drop in a conical spouted bed has been developed and described in our previous paper (Hadžismajlovi et al., 1986). In the present work, this model was examined at a wider range of experimental conditions and it was found that measured and predicted values of the minimum spouting flowrate and pressure drop differed by about 10.3% and 20.0%, respectively.It is shown that the spouted bed in a conical column is stable when the inlet tube diameter is less than 25 particle diameters.
Carbon monoxide hydrogenation over cobalt catalyst in a tube‐wall reactor: Part 1. Experimental studies
Authors: Dalai Ajay K. , Bakhshi Narendra N. 
Published: March 2009

AbstractEffects of temperature (250−275°C), pressure (0.1‐1.03 MPa) and feed gas exposure velocity (139‐722 μm/s) were studied on carbon monoxide hydrogenation in a tube‐wall reactor using plasma‐sprayed cobalt catalyst. The specific catalytic activity and hydrocarbon selectivity increased with an increase in pressure and temperature and a decrease in the exposure velocity. The results showed that the formation of olefins especially ethylene and propylene was favored at low pressures, low temperatures and high exposure velocities. This catalyst was found to be selective for C5+ hydrocarbons (27‐34 wt.%) at increased pressures (0.69‐1.03 MPa).
The behavior of ethylene glycol during the thermal solvolysis of cellulose
Authors: Vidal Pierre F. , Garnier Gil , Bouchard Jean , Overend Ralph P. , Chornet Esteban 
Published: March 2009

AbstractThe composition of the ethylene glycol solution resulting from cellulose thermal solvolysis, to produce microcrystal‐line cellulose, has been studied. Liquid and gas chromatographic analyses showed, a) little degradation of the ethylene glycol up to 280°C, and b) an acceleration of the degradation at higher temperatures in the presence of cellulose and glucose. Solubilized compounds resulting from the cellulose depolymerization although numerous were present in too low concentrations to warrant their recovery.
Feedback linearizing control of a fluidized bed reactor
Authors: Perrier M. , Aoufoussi H. , Chaouki J. , Chavarie C. , Dochain D. 
Published: March 2009

AbstractThe design of an adaptive nonlinear controller for the control of a fluidized bed reactor is derived by using exact linearization techniques. Reset action and parameter adaptation are used to make more robust the precise compensation of nonlinear terms, which is called for in the linearization technique. A nonlinear antiwindup mechanism is introduced to handle reset windup problem and to provide fast response without large overshoot. Simulation results show that the proposed adaptive controller guarantees good setpoint tracking. The developed estimation algorithm allows accurate estimation of the parameters for which the regressor component is not zero.
An interior point method implementation for solving large planning problems in the oil refinery industry
Authors: Ponnambalam Kumaraswamy , Vannelli Anthony , Woo Stephen 
Published: March 2009

AbstractMulti‐period planning problems in the oil and refinery industry are typically large, sparse, staircase/band diagonal structured and nonlinear optimization problems. Successive linear programming (SLP) type methods have been widely used for solving these planning problems. But, it has long been recognized that the simplex method used in solving linear programs requires a large number of iterations for staircase/band diagonal structured problems. In this paper, we report results of an application of a recently developed interior point method that promises to be many times faster than the simplex method for multi‐period planning problems. However, to facilitate the use of interior point method in the current SLP algorithms a hybrid method combining the interior point method and the simplex method is developed. Therefore, the results determined with this hybrid method are qualitatively equivalent to that obtained with the simplex method alone. The CPU times corresponding to the hybrid method are compared with the CPU times of simplex and dual affine methods. The new hybrid method generates a basic feasible solution of the linear programming problem and is approximately 7 times faster than the simplex method on the tested planning problems. Moreover, the interior point and hybrid methods become faster as the problem size increases.
Effect of liquid viscosity on gas holdups in a reversed flow jet loop reactor
Authors: Padmavathi G. , Rao K. Remananda 
Published: March 2009

AbstractThe effect of draft tube diameter and liquid viscosity on overall and annulus gas holdups were studied in a reversed flow jet loop reactor. The draft tube diameter to reader diameter ratio (Dd / D) and liquid viscosity were varied in the ranges 0.34‐0.67 and 1.5‐43 mPa. s, respectively. The maximum gas holdup was obtained when the Dd / D value ranged btween 0.47 and 0.61. The gas holdup decreased with increasing viscosity. Empirical correlations are presented to predict the gas holdups.