Catalogue en ligne Bibliothèque Ecole Nationale Polytechnique d'Alger

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8285–8311

Titre :	Dynamics of flow structures and transport phenomena, 2. relationship with design objectives and design optimization
Type de document :	texte imprimé
Auteurs :	Channamallikarjun S. Mathpati, Auteur ; Mandar V. Tabib, Auteur ; Sagar S. Deshpande, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8285–8311
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Flow structures Fluid dynamics techniques Computational fluid dynamics techniques
Résumé :	There have been several approaches in the literature to identify and characterize flow structures qualitatively as well as quantitatively. In the first part of this review, the methodologies and applications of various experimental fluid dynamics and computational fluid dynamics techniques, as well as mathematical techniques, have been discussed. Their chronological developments, and relative merits and demerits, have been presented to allow readers to make a judgment as to which techniques to adopt. In the present part of the review series, a stepwise procedure is suggested for the design of equipment using flow structure knowledge. An attempt has been made to relate the structure properties (such as age, penetration depth, size, shape, and energy content distribution) to the design parameters (such as mixing time, heat- and mass-transfer coefficient, drag coefficient, dissipation rate, etc.). This understanding of flow structures has brought improvements in the formulations of heuristic models of mass and heat transfer. This review makes an effort in developing insights into the views of earlier established analytic and heuristic theories of heat and mass transfer. The recently revealed dynamics of flow structures (as uncovered through the use of various techniques) has helped in furthering the efforts of developing new theories of heat, mass, and momentum transfer. Such an understanding between the structure dynamics and the transport phenomena has helped in the optimization of flow pattern (for instance, maximization of ratios of heat and mass transfer, as well as mixing, with respect to energy input). In this direction, some success stories have been described that have already been implemented in industry and have good potential for implementation.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900396k

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8244–8284

Titre :	Dynamics of flow structures and transport phenomena, 1. experimental and numerical techniques for identification and energy content of flow structures
Type de document :	texte imprimé
Auteurs :	Jyeshtharaj B. Joshi, Auteur ; Mandar V. Tabib, Auteur ; Sagar S. Deshpande, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8244–8284
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Flow structures Experimental fluid dynamics techniques Computational fluid dynamics techniques
Résumé :	Most chemical engineering equipment is operated in the turbulent regime. The flow patterns in this equipment are complex and are characterized by flow structures of wide range of length and time scales. The accurate quantification of these flow structures is very difficult and, hence, the present design practices are still empirical. Abundant literature is available on understanding of these flow structures, but in very few cases efforts have been made to improve the design procedures with this knowledge. There have been several approaches in the literature to identify and characterize the flow structures qualitatively as well as quantitatively. In the last few decades, several numerical as well as experimental methods have been developed that are complementary to each other with the onset of better computational and experimental facilities. In the present work, the methodologies and applications of various experimental fluid dynamics (EFD) techniques (namely, point measurement techniques such as hot film anemometry, laser Doppler velocimetry, and planar measurement techniques such as particle image velocimetry (PIV), high speed photography, Schlieren shadowgraphy, and the recent volume measurement techniques such as holographic PIV, stereo PIV, etc.), and the computational fluid dynamics (CFD) techniques (such as direct numerical simulation (DNS) and large eddy simulation (LES)) have been discussed. Their chronological developments, relative merits, and demerits have been presented to enable readers to make a judgment as to which experimental/numerical technique to adopt. Also, several notable mathematical quantifiers are reviewed (such as quadrant technique, variable integral time average technique, spectral analysis, proper orthogonal decomposition, discrete and continuous wavelet transform, eddy isolation methodology, hybrid POD−Wavelet technique, etc.). All three of these tools (computational, experimental, and mathematical) have evolved over the past 6−7 decades and have shed light on the physics behind the formation and dynamics of various flow structures. The work ends with addressing the present issues, the existing knowledge gaps, and the path forward in this field.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie8012506

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8237–8243

Titre :	Bubble column with electrolytes : gas holdup and flow regimes
Type de document :	texte imprimé
Auteurs :	Sandra Orvalho, Auteur ; Marek C. Ruzicka, Auteur ; Jiri Drahos, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8237–8243
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Scale bubble column Electrolytes Aqueous solutions
Résumé :	Experiments were performed in a laboratory scale bubble column, to investigate the effect of electrolytes (inorganic salts) on the behavior of bubbly mixtures. Aqueous solutions of three salts were studied, Na2SO4 (p.a. grade), NaCl (p.a. grade), and NaCl (kitchen quality). The gas holdup was measured, and the prevailing flow regime was determined. A simplified method for determining the regime transition based on the spline function was suggested and successfully tested. The main goal was to find whether the dual effect of the electrolyte on the gas holdup and homogeneous regime stability reported earlier for CaCl2 occurs also with other compounds. We confirmed this dual effect for two more solutions. The measurements with NaCl (p.a. grade) were most likely corrupted by salt crystallization inside the orifices of the perforated plate.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900263d

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8232–8236

Titre :	Modeling dependence of creep recovery behavior on relaxation time distribution of aging colloidal suspensions
Type de document :	texte imprimé
Auteurs :	Yogesh M. Joshi, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8232–8236
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Scaling model Creep-recovery Colloidal suspensions
Résumé :	A scaling model is developed to correlate relaxation time distribution of soft glassy materials to ultimate recovery. We propose that in the limit of creep-recovery time smaller than age, time translational invariance can be applied to aging soft materials. In such a limit, multimode linear viscoelastic model with Spriggs relaxation spectrum predicts enhancement in the ultimate recovery with broadening of the relaxation time distribution. We analyze these results in the context of creep-recovery behavior of aqueous suspension of laponite with varying concentration of salt.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801894z

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8219–8231

Titre :	Mixed convection from a circular cylinder to power law fluids
Type de document :	texte imprimé
Auteurs :	A. A. Soares, Auteur ; J. Anacleto, Auteur ; L. Caramelo, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8219–8231
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Heat transfer characteristics Circular cylinder Mixed convection regime
Résumé :	The heat transfer characteristics from a circular cylinder immersed in power law fluids have been studied in the mixed convection regime when the imposed flow is oriented normal to the direction of gravity. The continuity, momentum, and thermal energy equations have been solved numerically using a second-order finite difference method to obtain the streamline, surface viscosity, and vorticity patterns, to map the temperature field near the cylinder and to determine the local and surface-averaged values of the Nusselt number. Overall, mixed convection distorts streamline and isotherm patterns and increases the drag coefficient as well as the rate of heat transfer from the circular cylinder. New results showing the complex dependence of all these parameters on power law index (n = 0.6, 0.8, 1, 1.6), Prandtl number (= 1,100), Reynolds number (1−30), and the Richardson number (0, 1, and 3) are presented herein. Over this range of conditions, the flow is assumed to be steady, as is the case for Newtonian fluids.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801187k

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8211–8218

Titre :	Tensile deformation and failure of thin films of aging laponite suspension
Type de document :	texte imprimé
Auteurs :	Asima Shaukat, Auteur ; Yogesh M. Joshi, Auteur ; Ashutosh Sharma, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8211–8218
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Tensile deformation Failure Visco-elastic thin films
Résumé :	In this paper, we study deformation, failure, and breakage of visco-elastic thin films of aging laponite suspension under a tensile deformation field. Aqueous suspension of laponite is known to undergo waiting time dependent evolution of its microstructure, also known as aging, which is accompanied by an increase in the elastic modulus and relaxation time. In the velocity controlled tensile deformation experiments, we observed that the dependence of force and dissipated energy on velocity and initial thickness of the film is intermediate to a Newtonian fluid and a yield stress fluid. For a fixed waiting time, strain at break and dissipated energy increased with velocity but decreased with initial thickness. With an increase in age, the strain at break and dissipated energy showed a decrease suggesting enhanced brittle behavior with an increase in waiting time, which may be caused by restricted relaxation modes due to aging. In a force controlled mode, decrease in strain at failure at higher age also suggested enhanced brittleness with an increase in waiting time. Remarkably, the constant force tensile deformation data up to the point of failure showed experimental time−aging time superposition that gave an independent estimation of relaxation time and elastic modulus dependence on age.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie9006326

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8205–8210

Titre :	In-situ UV−visible and Raman spectroscopy for gas−liquid−solid systems
Type de document :	texte imprimé
Auteurs :	C. P. Stemmet, Auteur ; J. C. Schouten, Auteur ; T.A. Nijhuis, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8205–8210
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	UV−vis and Raman spectroscopy Multiphase reactor Bubble column
Résumé :	This paper presents the use of UV−vis and Raman spectroscopy to measure the state of a solid in a multiphase reactor. A slurry of particles and a packed bubble column were used. As this study is a proof of principle a model for an active catalyst system, insoluble pH indicators deposited on the particles and on a solid foam packing (used as the packing material in the packed bubble column) are used. This insoluble pH indicator has different UV−vis and Raman spectra according to the liquid pH. The experimental results indicate that for the slurry the spectra obtained from the moving particles can be used to characterize the state of the pH indicator. Bubbles in the packed bubble column result in disturbances in the UV−vis and Raman spectra collected from the pH indicator adsorbed to the solid surface and this interference is removed successfully with a newly developed tolerance-and-averaging method.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801984w

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8193–8204

Titre :	Two-phase flow in minichannels : hydrodynamics, pressure drop, and residence time distribution
Type de document :	texte imprimé
Auteurs :	A. A. Kulkarni, Auteur ; V. S. Kalyani, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8193–8204
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Mini-channels Two-phase flow Flow rate ratio
Résumé :	Two-phase flow in mini-channels (1 mm × 1.5 mm × 430 mm and 1.5 mm × 0.5 mm × 430 mm serpentine channel geometry) made in different materials (SS 316, PMMA and Teflon) was studied at different flow rate ratio (0.66, 1.0 and 1.56) of the two immiscible fluids. A dual syringe pump was used to pump the fluids (air−water and water-kerosene) through the channels. For characterization of the two phase flow, experiments were carried out to measure the slug size distribution and relevant hydrodynamic properties, pressure drop across a single serpentine unit (i.e., one sinusoidal unit that includes two 180° return bends connected by a straight portion of 20 mm) and also the residence time distribution of water. In all the cases, the effect of material of fabrication on the hydrodynamics was significant. Apart from flow rates and flow rate ratio of the two fluids, the slug size distribution was seen to have a strong effect of the channel orientation (vertical, horizontal) and also the flow direction (up-flow and down-flow). In the RTD studies, the response curve observed at the end of the channel was significantly different than the published literature. The reasons for such observations are discussed in detail.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801937x

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8186–8192

Titre :	CFD simulation of bubble columns : modeling of nonuniform gas distribution at sparger
Type de document :	texte imprimé
Auteurs :	M. R. Rampure, Auteur ; S. M. Mahajani, Auteur ; V. V. Ranade, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8186–8192
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Bubble columns Plate spargers Nonuniform gas distribution 3D CFD model
Résumé :	Most laboratory bubble columns are equipped with sieve plate spargers. The sieve plate spargers are known to lead to nonuniform gas distribution. It is important to account for such nonuniform gas distribution at the sparger in the computational model before experimental data collected from such columns are used to fit the model parameters. In this article, such an attempt is made. A detailed, 3D CFD model was developed to simulate unsteady gas−liquid flows in bubble columns with sieve plate spargers. The sensitivity of the nonuniformity of gas distribution at the sparger with sparger resistance was examined. The model predictions were compared with the experimental data. The developed model and presented results will be useful for simulating industrial bubble columns.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie8018593

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8180–8185

Titre :	Foamability of liquid particle suspensions : a modeling study
Type de document :	texte imprimé
Auteurs :	Krishna Vijayaraghavan, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8180–8185
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Liquid particle suspensions Foamability Monte Carlo simulations Integral equations
Résumé :	Recent experiments on the foamability of liquid particle suspensions (with a particle size varying from nanometers to micrometers in diameter and in the absence of any surfactants) have shown that the foamability correlates well with the degree of particle coverage at the air−liquid surface. Furthermore, these experiments have also revealed foam inhibition due to the aggregation or clustering of particles in the bulk at high particle concentrations. The present study is aimed at theoretically modeling the observed phenomena. Theoretical analyses based on Monte Carlo simulations and the integral equations of statistical mechanics are used to model the particle aggregation phenomena in the bulk. The radial distribution functions, which show the particle packing density, are analyzed to obtain the effective energy of interaction between the particles. The maximum in foaminess due to the adsorption of particles on the air−liquid surface and clustering of particles in the bulk is explained. The modeling results are in good agreement with the experimental observations on foaminess with small particles.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801741q

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8172–8179

Titre :	Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model
Type de document :	texte imprimé
Auteurs :	Jianhua Chen, Auteur ; Ning Yang, Auteur ; Wei Ge, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8172–8179
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Regime transition Bubble columns Dual-bubble-size model Computational fluid dynamics simulation
Résumé :	This article investigates the two regime transition points for bubble columns with the so-called dual-bubble-size (DBS) model featuring the utilization of a stability condition to analyze the compromise between dominant mechanisms. Our previous work indicated that the second point could be reasonably predicted and physically interpreted by the DBS model for various gas−liquid systems. This work further clarifies the relationship between the bifurcation of energy dissipation and of structural parameters and the regime transition. It is found that the bifurcation of energy dissipation exists for both the gas−liquid and gas−solid systems and can be used to predict and understand regime transition in multiphase flow. Then the DBS model is incorporated into the two-fluid model for calculating interphase coupling, and a computational fluid dynamics (CFD) calculation is performed to simulate a bubble column. The “shoulder” on the gas hold-up curve can be observed in the simulation with the new coupling method, and the second transition point predicted from the CFD simulation is consistent with experiments and the calculation of the DBS model. Sparger effects are investigated through the two simulation cases for uniform aeration and local aeration, and the radial distribution of local hydrodynamic parameters is comparable with experimental data in the literature.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801644d

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8159–8171

Titre :	Hydrodynamic simulation of horizontal slurry pipeline flow using ANSYS-CFX
Type de document :	texte imprimé
Auteurs :	Kalekudithi Ekambara, Auteur ; R. Sean Sanders, Auteur ; K. Nandakumar, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8159–8171
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Solid−liquid (slurry) pipeline flows Three-dimensional hydrodynamic model ANSYS-CFX
Résumé :	The behavior of horizontal solid−liquid (slurry) pipeline flows was predicted using a transient three-dimensional (3D) hydrodynamic model based on the kinetic theory of granular flows. Computational fluid dynamics (CFD) simulation results, obtained using a commercial CFD software package, ANSYS-CFX, were compared with a number of experimental data sets available in the literature. The simulations were carried out to investigate the effect of in situ solids volume concentration (8 to 45%), particle size (90 to 500 μm), mixture velocity (1.5 to 5.5 m/s), and pipe diameter (50 to 500 mm) on local, time-averaged solids concentration profiles, particle and liquid velocity profiles, and frictional pressure loss. Excellent agreement between the model predictions and the experimental data was obtained. The experimental and simulated results indicate that the particles are asymmetrically distributed in the vertical plane with the degree of asymmetry increasing with increasing particle size. Once the particles are sufficiently large, concentration profiles are dependent only on the in situ solids volume fraction. The present CFD model requires no experimentally determined slurry pipeline flow data for parameter tuning, and thus can be considered to be superior to commonly used, correlation-based empirical models.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801505z

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8148–8158

Titre :	Three-dimensional deformation dynamics of trailing vortex structures in a stirred vessel
Type de document :	texte imprimé
Auteurs :	Yann Bouremel, Auteur ; Michael Yianneskis, Auteur ; Andrea Ducci, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8148–8158
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Three-dimensional deformation dynamics Vortical structures Stirred vessels
Résumé :	Novel three-dimensional methodologies suitable for the characterization and quantification of the deformation dynamics resulting from vortical structures in stirred vessels are presented. The analytical approaches are developed in the context of the three-dimensional deformation encountered by a spherical fluid element in the vicinity of the trailing vortices around a Rushton impeller and allow the identification of the rate and type of dynamics (stretching, compression, biaxial strain, or biaxial compression) encountered by such an element in the vortex flow field, as well as the resulting surface deformation at different parts of the vortex. The results facilitate a more in-depth understanding of the deformation processes involved in fluid mixing in a stirred vessel, and their implications for enhancement of mixing in such processes are discussed.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801481v

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8134–8147

Titre :	Validation of two-fluid simulations of a pseudo-two-dimensional bubble column with uniform and nonuniform aeration
Type de document :	texte imprimé
Auteurs :	Sarah M. Monahan, Auteur ; Rodney O. Fox, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8134–8147
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Bubble column Multiphase flow
Résumé :	The multiphase flow simulated in this work corresponds to the pseudo-2D bubble-column experiments at Delft University of Technology (Harteveld et al. Can. J. Chem. Eng. 2003, 81, 389−394). As in the work of Monahan and Fox (AIChE J. 2007, 53, 9−18), the complete set of interphase force models includes drag, added-mass, lift, rotation, and strain. The simulation results are presented in the form of comparisons with the experimental data for the time-averaged gas holdup and the instantaneous and time-averaged air and liquid velocity fields. Overall, the qualitative and quantitative comparisons between experiments and simulations are satisfactory for both uniform and nonuniform aeration. In particular, the model predicts the flow patterns observed in the experiments, but in some cases at slightly different values of the amount of aeration. In the latter cases, it is shown that changing the model parameters does not improve the agreement with experiments. However, changing the liquid-velocity boundary condition from zero stress to zero slip leads to a small improvement.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801202x

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8121–8133

Titre :	Population balance modeling of liquid-liquid dispersions in homogeneous continuous-flow stirred tank
Type de document :	texte imprimé
Auteurs :	Singh, K. K., Auteur ; S. M. Mahajani, Auteur ; K. T. Shenoy, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8121–8133
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Population balance modeling Dilute phosphoric acid n-paraffin Tributyl phosphate Di-2-ethyl hexyl phosphoric acid
Résumé :	This work presents population balance modeling to predict representative drop sizes and drop size distributions in dispersions of dilute phosphoric acid in a mixture of n-paraffin, tributyl phosphate, and di-2-ethyl hexyl phosphoric acid (D2EHPA) created in a continuous-flow stirred tank agitated with a top-shrouded pump-mix impeller having four trapezoidal blades. The stirred tank has been assumed to be homogeneous. Three population balance models, differing in droplet breakage rate models, have been evaluated. A part of the experimental data has been used to obtain the optimum values of the parameters of all the three models. The remaining part of the experimental data has been used to compare the models for their ability to predict the representative drop diameters and the number probability density distributions. On the basis of this comparison, the best model has been identified.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie800901b

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8109–8120

Titre :	Numerical simulations of bubble formation and rise in microchannels
Type de document :	texte imprimé
Auteurs :	Deepak Goel, Auteur ; Vivek V. Buwa, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8109–8120
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Microchannels Gas−liquid flow Bubbles
Résumé :	Gas−liquid flow in microchannels is of fundamental importance to many engineering applications involving microreactors, monolith reactors, microheat exchangers, and several other microfluidic devices. Slug flow, characterized by motion of long bubbles, also referred to as Taylor bubbles, is the most important of the different two-phase flow regimes observed in microchannels. In this work, the formation of bubbles and their rise in circular capillaries in the Taylor flow regime is investigated by using the volume-of-fluid method. The dynamics of formation and rise of Taylor bubbles in glass capillaries of 1, 0.5, 0.75, and 0.3 mm diameter for air−water and air−octane systems was simulated. The effects of superficial gas and liquid velocities, channel geometry (nozzle wall thickness, nozzle diameter, capillary diameter), wall adhesion (contact angle), and fluid properties (surface tension, viscosity) on the dynamics of bubble formation were investigated. The predicted bubble shapes and bubble formation periods were validated using the experimental data reported by Salman et al. (Salman, W.; Gavriilidis, A.; Angeli, P. Chem. Eng. Sci. 2006, 61, 6653−6666) for a wide range of experimental parameters. Such experimentally validated computational flow models will be useful to simulate the mass transfer and reactions in microcapillaries/channels.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie800806f#cor1

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8098–8108

Titre :	Gas-solid turbulent flow in a circulating fluidized bed riser : numerical study of binary particle systems
Type de document :	texte imprimé
Auteurs :	Y. He, Auteur ; N. G. Deen, Auteur ; M. van Sint Annaland, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8098–8108
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Turbulent gas-particle multiphase flow Circulating fluidized bed riser Discrete particle model Navier−Stokes equations Subgrid scale stresses
Résumé :	Numerical simulations were performed of a turbulent gas-particle multiphase flow in a circulating fluidized bed riser using a hard-sphere discrete particle model (DPM) for the particle phase and the Navier−Stokes equations for the gas phase, where the subgrid scale stresses (SGS) were modeled with the SGS model proposed by Vreman.(1) The model enables the simulation of systems with an arbitrary particle size distribution. In this work, binary mixtures of particles with different diameters were studied. From the numerical results it is found that the particles display size distribution in both horizontal and vertical directions. Small particles have a higher vertical particle velocity than the large particles. With increasing superficial gas velocity, the vertical particle velocity is increased. The average particle velocity and concentration vary both in the horizontal and vertical directions. Finally, the numerical results are compared with the experimental and numerical results of Mathiesen et al.(2). It is found that the simulation results with Vreman’s SGS model agree better with the literature data than those obtained with a classical Smagorinsky(3) model, especially in the zone close to the wall.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie8015297

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8083–8090

Titre :	Hydrotropic extraction process for recovery of forskolin from coleus forskohlii roots
Type de document :	texte imprimé
Auteurs :	Sanjay P. Mishra, Auteur ; Vilas G. Gaikar, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8083–8090
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Hydrotropic solubilization Forskolin Coleus forskohlii root
Résumé :	A simple and rapid method based on hydrotropic solubilization is developed for isolation of forskolin from coleus forskohlii roots. The plant cells are permeabilized by aqueous hydrotrope solutions followed by extraction and solubilization of forskolin into the hydrotrope solutions of alkyl benzene sulfonates and carboxylates. The solubility of forskolin is increased by 350 times in the hydrotropic solutions and it is possible to recover 85% pure forskolin from the hydrotropic solutions by simple dilution with water. The purity of the recovered forskolin decreased from 85% to 70% on decreasing particle size of the roots. Nearly 80% of the forskolin having 50% purity was recovered from the coleus roots using 2.0 mol/dm3 aqueous sodium cumene sulfonate (Na−CS) solutions at 363 K. Na−CS showed the most efficient solubilization of forskolin from the Coleus roots among all the other hydrotropes.

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8068–8082

Titre :	1,3-propanediol from fossils versus biomass : a life cycle evaluation of emissions and ecological resources
Type de document :	texte imprimé
Auteurs :	Robert A. Urban, Auteur ; Bhavik R. Bakshi, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8068–8082
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Life cycle assessment Conventional process-based Hybrid economic input−output Hybrid ecologically based
Résumé :	Despite the popularity of life cycle assessment (LCA) for understanding the broader implications of technological alternatives, it faces challenges due to difficulties in defining the analysis boundary, uncertain data, and ignoring the role of ecological goods and services. The latter natural capital is essential for sustainability but is only considered partially in conventional LCA. Accounting for ecological resources introduces the challenge of how to aggregate resources of widely varying qualities such as sunlight, wood, water, and coal. Methods based on mass, energy, and exergy have been proposed and are evaluated in this work. In addition, this work aims to analyze three LCA techniques with different system boundaries: conventional process-based LCA, hybrid economic input−output LCA (EIO-LCA), and hybrid ecologically based LCA (Eco-LCA). These three methods are applied to the case study of 1,3-propanediol (PDO) produced via fossil-based and bio-based feedstocks. The results of this study indicate that a hierarchical set of metrics can be useful for gaining insight into the role of ecosystem resources in a life cycle. Among aggregation methods, ecological cumulative exergy consumption seems to provide meaningful results, but more empirical studies are needed. It is also determined that bio-based PDO is more attractive than fossil-based PDO because of less nonrenewable resource consumption and greenhouse gas emissions. However, bio-based PDO does rely more on land, water, and fertile soil. By determining the impact of making the current PDO demand entirely from corn, it is found that the consumption of natural resources relative to national consumption is very low. While producing PDO alone from corn may have a negligible impact in terms of emissions and resource use, switching other products to bio-based will have an additive effect, increasing the strain on some ecological goods and services. These impacts should be addressed before promoting the large scale production of bio-based products.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801612p

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8054–8067

Titre :	Biomimetic adaptation of the evolutionary algorithm, NSGA-II-aJG, using the biogenetic law of embryology for intelligent optimization
Type de document :	texte imprimé
Auteurs :	Manojkumar Ramteke, Auteur ; Santosh K. Gupta, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8054–8067
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Elitist nondominated sorting genetic algorithm Adapted jumping gene operator
Résumé :	Several of the recent optimization techniques have been adapted from nature. The elitist nondominated sorting genetic algorithm with the adapted jumping gene operator (NSGA-II-aJG) is one such evolutionary technique inspired by genetics. This algorithm is quite useful for solving multiobjective optimization problems. The drawback of these techniques is the inordinately large amount of computational effort required for solving real-life problems, even though these techniques are quite robust as compared to conventional techniques. Their use for online optimization is particularly limited. Many industrial optimization problems require frequent changes in the objective functions as well as the decision variables, even though the system itself remains the same. Surprisingly, no algorithm has been developed which makes use of previous information for solving a different problem for the same system in a comparatively short (computational) time. The algorithm developed in this study, namely, B-NSGA-II-aJG, carries this out more intelligently using the biogenetic law of embryology. This algorithm increases the speed of convergence significantly.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801592c

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8048–8053

Titre :	Oxidation of dimethyl sulfoxide in aqueous solution using microbubbles
Type de document :	texte imprimé
Auteurs :	Pan Li, Auteur ; Hideki Tsuge, Auteur ; Keiko Itoh, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8048–8053
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Dimethyl sulfoxide wastewater Semiconductor manufacturing industry Biological treatment
Résumé :	A large quantity of dimethyl sulfoxide (DMSO) wastewater is discharged from washing and rinsing processes in semiconductor manufacturing industry. Traditional biological treatment is known to be difficult for the treatment of DMSO-containing wastewater because of odor problems. Ozonation of DMSO combined with a biological process is suggested to be a cost-efficient treatment solution, whereas the application of ozone to wastewater treatment has been limited by its low utilization efficiency and high cost. In this study, we applied an ozone microbubble generator to increase ozone transfer efficiency in the aqueous solution. The oxidation of DMSO by ozone microbubbles was investigated in a bubble column reactor with an inner diameter of 20 cm. We studied the dependence of DMSO degradation on the gas and liquid flow rates. Experimental results indicate that the ozonation of DMSO is a first-order mass-transfer-controlled reaction and the reaction rate constant increases with increasing gas velocity. Ozone transfer ratio increases with decrease in gas flow rate.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801565v

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8037–8047

Titre :	Effect of competing reversible reactions on optimal operating policies for plants with recycle
Type de document :	texte imprimé
Auteurs :	Derek W. Griffin, Auteur ; Duncan A. Mellichamp, Auteur ; Michael F. Doherty, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8037–8047
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Optimal steady-state operating policies Plants with recycle Reversible reactions
Résumé :	A simple classification procedure for determining optimal steady-state operating policies for plants with recycle has recently been developed by Griffin et al. to cover complex process chemistries. (Griffin, D. W.; Mellichamp, D. A.; Doherty, M. F. AIChE J. 2008, 54, 2597). This procedure classifies a process chemistry into one of two groups of operating policies based solely on the reaction kinetics. The optimal operating policy for a bounded chemistry is to operate the reactor completely full for all production rates while a nonbounded chemistry may have a variable reactor volume subject to system constraints. The current work focuses on process chemistries with reversible reactions and demonstrates that the optimal operating policy can change depending on which reaction(s) is(are) reversible and the magnitude of the equilibrium constant(s). Process chemistries with a reversible desired reaction also exhibit multiple steady-states, but only one of the steady-states corresponds to feasible operating conditions.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801482z

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8030–8036

Titre :	Controlling the morphology of resorcinol−formaldehyde-based carbon xerogels by sol concentration, shearing, and surfactants
Type de document :	texte imprimé
Auteurs :	Chandra S. Sharma, Auteur ; Devendra K. Upadhyay, Auteur ; Ashutosh Sharma, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8030–8036
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Carbon xerogel microspheres Formaldehyde Nonionic surfactants Dilution ratio Hydrophilic−lipophilic balance
Résumé :	Carbon xerogel microspheres were synthesized by inverse emulsion polymerization of resorcinol with formaldehyde, followed by pyrolysis at 900 °C under nitrogen atmosphere. We have studied the effect of various synthesis parameters, including dilution ratio and hydrophilic−lipophilic balance (HLB) of nonionic surfactants, on the size and morphology of resulting structures. The average particle size of carbon microspheres could be modulated from 1 to 28 μm by varying the dilution ratio over 3 orders of magnitude. Increase in the HLB value and the amount of surfactants produced a variety of dense carbon, but open-architecture fractal-like structures. Three different methods of stirring, namely, magnetic, mechanical, and ultrasonication were applied during the inverse emulsification to produce carbon xerogel microstructures. Formation of a wide spectrum of nonporous carbon particle morphologies, including the highly branched, hierarchical microparticles, by tuning the synthesis conditions may have potential applications in printing technology, controlled drug delivery, biosensors, and carbon-based microelectromechanical systems (C-MEMS) including bio-MEMS.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900359w

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8024–8029

Titre :	The behavior of an oscillating particle attached to a gas−liquid surface
Type de document :	texte imprimé
Auteurs :	Paul Stevenson, Auteur ; Seher Ata, Auteur ; Geoffrey M. Evans, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8024–8029
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Force balance Gas-liquid surface Oscillating particle
Résumé :	A force balance is presented for a particle attached to the surface of a larger bubble that oscillates such as it would immediately after a coalescence event. Similar previous analyses have neglected the Basset history force, the added mass of the particles, and the drag force imparted by the fluid upon the particles. Methods of crudely estimating the upper-bound of the Basset history force and the drag are proposed, and it is shown that these, along with the d’Alembert force due to particle acceleration, govern the value of the compensating capillary force and therefore the position of the three-phase contact line. The weight, buoyancy, and hydrostatic force due to meniscus depression are insignificant. The position of the three-phase constant line demonstrates an approximately first order lag to a stimulus. Because of this, the true position of the three-phase contact line can be estimated, and this must require that the three-phase contact angle demonstrates oscillatory behavior. It is possible that this phase-lag may underpin the process of particle detachment.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900085d

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8014–8023

Titre :	Some mechanistic insights into the gelation of regenerated silk fibroin sol
Type de document :	texte imprimé
Auteurs :	Shailesh Nagarkar, Auteur ; Avinash Patil, Auteur ; Ashish Lele, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8014–8023
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Sol−gel transition Regenerated silk fibroin
Résumé :	We provide some new insights into the kinetics and mechanism of sol−gel transition as it pertains to regenerated silk fibroin, which is the principle structural protein of silkworm silk fiber. Silk fibroin was dissolved in lithium bromide and dialyzed against deionized water to prepare a regenerated fibroin solution. This solution was found to be unstable at lower pH and transformed into a colloidal gel. The kinetics and mechanism of the sol−gel transition were investigated using rheology and light scattering. We show that gelation proceeds in two steps. In the first step, a weak gel is formed almost immediately upon lowering the pH, while in the second step further gelation proceeds rapidly after a long induction time to form a self-similar structure.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801723f

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8007–8013

Titre :	Impact of internals on the gas holdup and bubble properties of a bubble column
Type de document :	texte imprimé
Auteurs :	Ahmed A. Youssef, Auteur ; Muthanna H. Al-Dahhan, Auteur
Année de publication :	2009
Article en page(s) :	pp. 8007–8013
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Internals Methanol synthesis Fischer-Tropsch process Gas holdup Bubble column
Résumé :	Most industrial applications involving bubble columns require the addition of internals for heat exchanging. However, most academic research on bubble columns has been performed in hollow (empty) ones. Hence, the impact of internals on the hydrodynamics of a bubble column has been insufficiently studied in the open literature. Accordingly, this study focuses on investigating the effect of internals that mimic those used in methanol synthesis (5% covered cross-sectional area) and the Fischer−Tropsch (FT) process (22% covered cross-sectional area) on the local gas holdup, gas−liquid interfacial area, bubble chord length, and bubble velocity distributions. The investigations have been performed using a four point optical probe in an 8 in. diameter column. An air−water system was used with superficial gas velocities up to 20 cm/s. An increase in gas holdup and interfacial area was obtained upon insertion of the internals, although the impact of the less dense internals (5% covered area) was not significant. However, in the case of dense internals, the bubble chord length decreased, yielding a decrease in the bubble velocity.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900266q

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7994–8006

Titre :	On the coupled solution of a combined population balance model using the least-squares spectral element method
Type de document :	texte imprimé
Auteurs :	Zhengjie Zhu, Auteur ; Carlos A. Dorao, Auteur ; D. Lucas, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7994–8006
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Cross-sectional averaged Population balance model Flow field Spectral element method
Résumé :	In this work, a cross-sectional averaged two-fluid model combined with a population balance model is applied to simulate the flow field and the bubble size distributions in a two-phase bubble column. The Martinez-Bazan breakage kernel and a modified Prince and Blanch coalescence kernel have been chosen to describe bubble breakage and bubble coalescence, respectively. In the present study, we discuss the use of a higher-order spectral element method—the least-squares method—to compute the system of equations in a coupled manner. The least-squares method is highly accurate and has a number of advantages over the conventional numerical methods like the finite difference and finite volume methods. In contrast to the finite volume method, when desinging an overall solution algorithm, this least-squares method ensures that all the continuity equations are satisfied individually and it deals with both the convective and diffusive terms stably and accurately. The novel iterative algorithm solves the flow and the population balance equation in a coupled manner. The model has been validated against experimental data obtained for two-phase flow in a bubble column. The predicted bubble size distribution and other flow quantities are in good agreement with the experimental data.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900088q

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7986–7993

Titre :	Effect of oxygen on cyclohexane oxidation : a stirred tank study
Type de document :	texte imprimé
Auteurs :	Radmila Jevtic, Auteur ; P. A. Ramachandran, Auteur ; Milorad P. Dudukovic, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7986–7993
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Cyclohexane oxidation Nylon-6 Nylon-6,6 Oxygen availability
Résumé :	Cyclohexane oxidation is the first step in the currently used technology for production of Nylon-6 and Nylon-6,6 which employs a two-stage process. In the first stage, cyclohexane is oxidized with air to 4−8% conversion at about 80% selectivity to cyclohexanol and cyclohexanone as desired products. In this study, we examined the effect of oxygen availability on the volumetric productivity, yield, and selectivity of this reaction by using a stirred autoclave operated free from mass transfer effects in a batch and “dead-end” semibatch mode. Both uncatalyzed and catalyzed systems were used. The experimental and the modeling results lead to the conclusion that increased oxygen availability improves the productivity and selectivity at the fixed cyclohexane conversion (4%) as the residence time required declines with the increase in oxygen concentration. The positive effect on the reaction rate of increased oxygen concentration is the same when such an increase is achieved at constant pressure by raising the mole fraction of oxygen in the feed or by raising the total pressure in the system at fixed oxygen mole fraction.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900093q

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7976–7985

Titre :	When is the quasi-steady-state approximation admissible in metabolic modeling? when admissible, what models are desirable?
Type de document :	texte imprimé
Auteurs :	Hyun-Seob Song, Auteur ; Doraiswami Ramkrishna, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7976–7985
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Quasi-steady-state approximation Metabolic modeling
Résumé :	A strategy is presented for scrutiny of the quasi-steady-state (QSS) approximation in metabolic modeling that involves tracking dynamic data on extracellular products in so-called flux, as well as yield vector spaces when the substrate uptake flux is perturbed sinusoidally about some average value with specified frequency and amplitude. Criteria accrue for the diagnosis of any violation (and its extent) of the QSS approximation and are applied to data produced by simulations from models free from the QSS approximation. It is shown that, even when the assumption is admissible, the choice of the appropriate QSS model depends on the frequency and amplitude of the perturbation. Three different QSS models in the literature, viz., dynamic flux balance analysis, the macroscopic bioreaction model, and the hybrid cybernetic model, are evaluated, and circumstances are identified when one or more of the QSS models might be valid, as well as when none of them are.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900075f

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7965–7975

Titre :	Dynamic modeling and simulation of ozonation in a semibatch bubble column reactor : decolorization and mineralization of azo dye orange II by ozone
Type de document :	texte imprimé
Auteurs :	Masahiro Tokumura, Auteur ; Takashi Katoh, Auteur ; Hiroki Ohata, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7965–7975
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Ozone decolorization Azo dye Orange II Mineralization Rate-based model Chemical reaction Gas−liquid mass transfer
Résumé :	Ozone decolorization and mineralization of azo dye Orange II were examined. In order to elucidate the dynamics of the oxidation process by ozone, the rate-based model consisting of the rates of chemical reaction and gas−liquid mass transfer was developed. The overall enhancement factor was introduced to correct the underestimation of mass transfer driving force for fast reactions. In modeling, nonideal mixing characteristics in the gas and liquid phases were described using a tanks-in-series model with backflow. The parameters in the proposed mixing model were determined on the basis of a multiple circulation cell model and a velocity profile of recirculatory flow in a bubble column. Experiments for decolorization and mineralization of Orange II were performed to verify the capability of the proposed model in a semibatch bubble column. The decolorization completed rather quickly. However, the mineralization characterized by the total organic carbon (TOC) was incomplete and its rate was rather slow. It was found that the decolorization rate decreased with the increase in the initial Orange II concentration and increased with increasing ozone gas injection rate, ozone dosage, and solution pH. The proposed model could reasonably describe the present experimental results for the dynamic changes and the steady state of decolorization, mineralization, dissolved ozone concentration, and ozone concentration in the outlet gas. The proposed model might effectively handle the prediction of ozone oxidation process in a semibatch bubble column.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie802009j

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7959–7964

Titre :	Modeling of NO removal over CuO/γ-Al2O3 catalyst in a bubbling fluidized bed reactor
Type de document :	texte imprimé
Auteurs :	Muhammad F. Irfan, Auteur ; Sang Done Kim, Auteur ; Muhammad R. Usman, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7959–7964
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	CuO/γ-Al2O3 catalyst Bubbling fluidized bed reactor
Résumé :	The NO reduction over CuO/γ-Al2O3 catalyst in a bubbling fluidized bed reactor has been determined on the basis of the two-phase model at the maximum conversion temperature of 300 °C. This temperature is critical as it deals maximum conversion, NH3 adsorption/desorption, and NH3 oxidation, which also takes place above this temperature and hence causes a decrease of NO reduction. The effects of superficial gas velocity (ug), [NH3]/[NO] molar ratio, and the static bed height (hs) on the reduction efficiency of NO over CuO/γ-Al2O3 as a bed material in a fluidized bed reactor with variation of reaction temperatures (rate constant, kr) have been determined, and a model has been developed for the NO removal process in a bubbling fluidized bed using the two-phase theory. The results are compared with the simulation results obtained through the Maple and MATLAB simulation tools.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie8018214

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7945–7958

Titre :	Characteristics of a confined impinging jet reactor : energy dissipation, homogeneous and heterogeneous reaction products, and effect of unequal flow
Type de document :	texte imprimé
Auteurs :	Shad W. Siddiqui, Auteur ; Yinan Zhao, Auteur ; Alena Kukukova, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7945–7958
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Confined impinging jet reactor Energy dissipation rate Micromixing efficiency Homogeneous reaction Heterogeneous precipitation reaction
Résumé :	The confined impinging jet reactor (CIJR) has attracted wide interest in the past few years because of the efficient micromixing that it offers. In this work, the CIJR is characterized over a wide range of mixing conditions, using three measures of performance: estimates of the energy dissipation rate, micromixing efficiency based on the yield of a homogeneous reaction, and particle size resulting from a heterogeneous precipitation reaction. The energy dissipation results showed very good agreement between four methods, with values up to 100 times greater than those observed in stirred tanks. The reactions showed a higher sensitivity to mixing conditions at higher concentrations, with less effect of mixing at high flow rates. The operation of the CIJR was very robust to changes in flow rate, with stable performance for up to a 30% difference in the inlet flows.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801562y

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7938–7944

Titre :	Studies of the interaction of ionic liquid and gas in a small-diameter bubble column
Type de document :	texte imprimé
Auteurs :	R. Kaji, Auteur ; D. Zhao, Auteur ; P. Licence, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7938–7944
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Gas bubbling Ionic liquid
Résumé :	Gas bubbling through a column of ionic liquid has been investigated using high-speed video and a conductivity method to measure a cross-sectionally averaged void fraction. For comparison, other liquids with similar physical properties, e.g., a glycerol/water mixture and glycerol/water with dissolved potassium chloride, were also employed. Air was used for the gas phase. The similarities and differences of flow characteristics were observed from the images. The differences in flow patterns were revealed by analysis of the time series of conductance signals in the form of the probability density function, autocorrelation, and power spectrum density. Furthermore, the velocities and frequencies of flow structures were deduced. The flow characteristics of ionic liquid were found to be similar to those of the other liquids studied.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie8014439

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7928–7937

Titre :	Simulating the dynamics of gas−solid flows in a multichannel microcirculating fluidized bed
Type de document :	texte imprimé
Auteurs :	Yi-Ning Wang, Auteur ; Faïçal Larachi, Auteur ; Shantanu Roy, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7928–7937
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Gas−solid flows Multichannel microcirculating fluidized-bed reactors Computational fluid dynamics (CFD) modeling
Résumé :	The dynamics of gas−solid flows and distribution in monolithic multichannel microcirculating fluidized-bed reactors was analyzed using a computational fluid dynamics (CFD) modeling approach. A 2D Euler−Euler multiphase model with the kinetic theory of granular flow has been solved for the detailed monolithic packing geometry. The assemblage of monolithic structured packings with through-flow gas-particulate flows is globally considered in the simulation to capture the dominant mechanisms contributing to the final overall aero/granular dynamics. Due to the complex nature of the interactions between gas and particulate phases and the stationary monolith backbone, one of the challenges in the design and operation of the monolith reactors is the prevention of flow maldistribution. The work presented in this paper forms the basis for a comprehensive reactor-scale model for exploring the intriguing possibilities that the proposed process intensification concept offers for chemical reactions of energy/environmental relevance such as biomass gasification and combustion.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie8012083

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7923–7927

Titre :	Ultrasound-assisted synthesis of biodiesel from palm fatty acid distillate
Type de document :	texte imprimé
Auteurs :	Vishwanath G. Deshmane, Auteur ; Parag R. Gogate, Auteur ; Aniruddha B. Pandit, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7923–7927
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Palm fatty acid distillate Biodiesel Ultrasonic irradiations
Résumé :	The present work aims at exploiting palm fatty acid distillate as a starting raw material for synthesis of biodiesel with the aim of reducing the cost of production. Esterification of palm fatty acid distillate (PFAD) with methanol in the presence of concentrated H2SO4 as a catalyst has been investigated in the presence of ultrasonic irradiations at 22 kHz frequency and 120 W as supplied power dissipation. The effect of different operating parameters such as molar ratio of reactants, catalyst quantity, and operating temperature have been studied with the aim of process optimization. It has been observed that ultrasound significantly enhances the rate of reaction and also the extent of equilibrium conversion. A certain degree of conversion attributed to heterogeneity of the system, which adds to mass transfer resistances under conventional approach, appears to get eliminated due to ultrasound. Conversion levels of more than 90% have been observed with the use of ultrasound in about 150 min under ambient operating conditions.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie800981v

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7915–7922

Titre :	Kinetic and mechanistic investigation of microwave-assisted lipase catalyzed synthesis of citronellyl acetate
Type de document :	texte imprimé
Auteurs :	Ganapati D. Yadav, Auteur ; Indrakant V. Borkar, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7915–7922
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Citronellyl acetate Chemical catalysis Biocatalysis
Résumé :	Citronellyl acetate (also known as citronellol acetate) is an important perfumery chemical which can be produced both by chemical catalysis and by biocatalysis. In the current work, Novozym 435 (Candida antarctica lipase B immobilized on polyacrylic resin) was employed to synthesize citronellol acetate directly from citronellol and vinyl acetate under the influence of microwave irradiation vis-à-vis conventional heating. The effects of various parameters affecting the conversion and initial rates of transesterification were studied to deduce the kinetics and mechanism. The enzyme inhibition was studied in conjunction with both modes of heating. Under microwave irradiation, there was an increase in lipase activity due to enhanced collision of molecules, which can in turn be attributed to an increase in the entropy of the system. The synergistic effect of reaction media and microwaves on lipase activity was analyzed. The enzyme is inhibited by alcohol, which is reduced significantly by microwaves. The analysis of the initial rate data and progress curve data showed that the reaction obeys the ping-pong bi−bi mechanism with inhibition by citronellol and vinyl acetate. The experimental and theoretical values match very well.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie800591c

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7910–7914

Titre :	Modeling in multiphase reactor design : solid phase residence time distribution in three-phase sparged reactors
Type de document :	texte imprimé
Auteurs :	Vivek P. Utgikar, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7910–7914
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Gas−liquid−noncatalytic solid reactions Residence time distribution Three-phase sparged reactors
Résumé :	Gas−liquid−noncatalytic solid reactions are typically conducted in three phase sparged reactors. Modeling of the particle size residence time distribution (RTD) and verification/validation of the models is essential for fundamental understanding and design of these multiphase reactors. A brief review and analysis of the RTD models reported in the literature is presented in this paper. Earlier investigations in this field typically employ the axial dispersion model to describe the RTD. It is shown that the tanks-in-series model can equally be applied in such cases. These single-parameter models are simplistic in nature and do not reflect accurately the flow behavior of solids in the three phase sparged reactors. Recent phenomenological approaches to modeling involve using a tanks-in-series model in parallel or countercurrent recycle mode with a plug flow reactor. These models have better accuracy but are also more complex and require specifications of several more parameters. Further developments in the field will be based on these models.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900067g

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7899–7909

Titre :	Coke formation and characterization during 1-hexene isomerization and oligomerization over H-ZSM-5 catalyst under supercritical conditions
Type de document :	texte imprimé
Auteurs :	Jiawei Wang, Auteur ; Faiza Hassan, Auteur ; Peter I. Chigada, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7899–7909
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	1-hexeneIsomerization Oligomerization Catalysts
Résumé :	The isomerization and oligomerization of 1-hexene was studied over ZSM-5 catalyst under sub- and supercritical conditions within a down-flow fixed bed reactor in the temperature range of 220−250 °C and pressure range 10−70 bar. The catalyst activity and the product selectivity were found to be dependent on the operation conditions. Reactions were carried out over beds with 10 and 0.5 g catalyst, the smaller bed being used to simulate coking in the top layer of the larger bed. The conversion of 1-hexene over the 10 g bed of catalyst was in the range 83−99%, depending upon the operating conditions and was stable during the test period. An increase of the reaction temperature from 220−250 °C led to higher selectivity toward oligomerization, as did increases in reaction pressure in the range 10−70 bar. The amount of coke deposited on the catalysts decreased from 18.8 wt % at 235 °C and 10 bar in the subcritical region to 10.4 wt % at 235 °C and 40 bar in the supercritical region. DRIFTS showed that deposited coke is mainly polyolefinic. Nitrogen sorption showed that following initial shallow pore filling over shorter contact times, the pore mouth subsequently became blocked and coke mainly formed on the outside of the zeolite crystallites. When operating with 0.5 g catalyst, some deactivation occurred under subcritical conditions, although not under supercritical conditions. It appeared that with the smaller catalyst mass oligomers were retained within the pore structure of ZSM-5. The results of the study demonstrate that adjustment of the operating temperature and pressure can be used to tune the product selectivity of the reaction and the total amount of coke deposited upon the catalyst is reduced by operating under supercritical conditions.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801466d

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7893–7898

Titre :	Adsorption of aqueous selenite [Se(IV)] species on synthetic layered double hydroxide materials
Type de document :	texte imprimé
Auteurs :	Sujata Mandal, Auteur ; S. Mayadevi, Auteur ; Bhaskar D. Kulkarni, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7893–7898
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Layered double hydroxide materials Selenite adsorption Kinetic model
Résumé :	Layered double hydroxide materials (Zn/Al, Mg/Al, Zn/Fe) with varying composition (M2+:M3+ molar ratio, x = 3, 2, 1, and 0.33) were synthesized and evaluated for their selenium adsorption characteristics in aqueous medium. Zn/Al and Mg/Al LDHs with x = 3 and 2, exhibited very high selenite adsorption capacity. XRD patterns of the pristine LDHs, LDH after selenite adsorption, and chloride ion leaching studies revealed that adsorption of selenium on the LDHs occurred through both surface adsorption and ion-exchange mechanism. The adsorption data was fitted to Langmuir and Freundlich isotherm models. A pseudo second-order kinetic model was used to describe the adsorption kinetics of selenite on LDH materials. Desorption of selenite ions in water from the LDH−Se matrix was studied up to 5 h.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900136s

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7876–7892

Titre :	(Gas)-liquid-solid circulating fluidized bed reactors : characteristics and applications
Type de document :	texte imprimé
Auteurs :	Arnab Atta, Auteur ; S. A. Razzak, Auteur ; K. D. P. Nigam, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7876–7892
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Circulating fluidized beds Gas-solid circulating fluidized beds Gas-liquid-solid circulating fluidized beds
Résumé :	Accepting considerable advantages of circulating fluidized beds (CFBs) over the conventional fluidized beds, there has been numerous studies on CFBs concentrating primarily on the development of gas−solid circulating fluidized beds (GSCFBs). However a substantial amount of research has also been devoted to other two types of CFBs, namely liquid−solid and gas−liquid−solid circulating fluidized beds (LS and GLSCFBs). In this effort, an attempt has been made to summarize and review the research and progresses made on the last two types of CFBs since the highlighting of their hydrodynamics and potential applications in various industries by Zhu et al. [Can. J. Chem. Eng. 2000, 78, 82−94]. The issues associated with its hydrodynamics, scale-up, and design have been discussed with a re-emphasis on its potential application for various cost-effective processes.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie900163t

[article]
in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7865–7875

Titre :	Underground coal gasification : a brief review of current status
Type de document :	texte imprimé
Auteurs :	Evgeny Shafirovich, Auteur ; Arvind Varma, Auteur
Année de publication :	2009
Article en page(s) :	pp. 7865–7875
Note générale :	Chemical engineering
Langues :	Anglais (eng)
Mots-clés :	Coal gasification Industrial reactors Liquid hydrocarbon fuels
Résumé :	Coal gasification is a promising option for the future use of coal. Similarly to gasification in industrial reactors, underground coal gasification (UCG) produces syngas, which can be used for power generation or for the production of liquid hydrocarbon fuels and other valuable chemical products. As compared with conventional mining and surface gasification, UCG promises lower capital/operating costs and also has other advantages, such as no human labor underground. In addition, UCG has the potential to be linked with carbon capture and sequestration. The increasing demand for energy, depletion of oil and gas resources, and threat of global climate change lead to growing interest in UCG throughout the world. In this article, we review the current status of this technology, focusing on recent developments in various countries.
En ligne :	http://pubs.acs.org/doi/abs/10.1021/ie801569r

Industrial & engineering chemistry research / Paul, Donald R. . Vol. 48 N° 17

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