bluuebunny/crossref_metadata_2025 huggingface dataset:
The temperature‐scanning adiabatic plug‐flow reactor
Authors: Wojciechowski B. W.
Published: July 2010

This work introduces the Temperature‐Scanning Adiabatic Plug‐Flow Reactor (TSAR‐PF), a fast and efficient method for studying kinetics. The proposed method of operation and data reduction offers an attractive alternative to the isothermal methods presently used in kinetic studies and catalyst evaluation and reduces the labour required to collect such data by some orders of magnitude, making studies over a broad range of conditions possible at reasonable cost.

The proposed experimental method involves ramping (scanning) of the input temperature to an adiabatic plug‐flow reactor while recording both conversion and output temperature. The interpretation of this data to yield rate parameters is described.
Simultaneous methanol removal and destruction from wastewater in a trickle‐bed reactor
Authors: Cheng S. , Chuang K. T.
Published: July 2010

The stripping of methanol from wastewater was studied in a trickle‐bed reactor packed with a mixture of hydrophobic catalyst and hydrophilic support. The process involves air stripping of methanol followed by a gas phase oxidation of methanol into CO2 and H2 O over a platinum catalyst. At temperatures between 25 and 70°C, the overall rate was found to be controlled by the stripping step. Since the oxidation results in a lower concentration of methanol in the gas phase, the increased driving force for interfacial mass transfer leads to higher overall methanol removal efficiency.
Modeling of batchwise xanthan production
Authors: Peters H.‐U. , Suh I.‐S. , Schumpe A. , Deckwer W.‐D.
Published: July 2010

An empirical model for the production of xanthan polysaccharide by batchwise cultivation of Xanthomonas campestris was developed. The effects of oxygen depletion in the liquid and bacterial growth rate on the xanthan production rate and the time‐course of the xanthan molar mass were taken into account. When the oxygen transfer was rate limiting in the non‐growth phase, the molar mass of the final xanthan product was lower than that observed in the absence of oxygen limitation. A constant feed of medium, containing citric acid, increased the xanthan productivity and allowed a polysaccharide concentration of 50 kg/m3 to be reached within 57 h. Low productivity observed in a 3 m3 reactor with small‐diameter Rushton turbines was attributed to stagnant zones in the wall region.
Spectral measurement of the complex refractive index of fly ashes of canadian lignite and sub‐bituminous coals
Authors: Lohi A. , Wynnyckyj J. R. , Rhodes E.
Published: July 2010

The complex spectral refractive index (absorption index) of fly ash from two generating stations burning Canadian lignite and sub‐bituminous coals have been examined by two different techniques. Ash samples collected at different combustion conditions were analyzed. It is shown that the absorption index of both ashes is in the range of 0.004 to 0.018 in the wavelength range of 0.7‐2.5 μm. The effects of presence of carbonaceous material in ashes, iron content and different operating (combustion) conditions are reported.
Heat transfer to newtonian and non‐newtonian liquids in a screw agitator and draft coil system
Authors: Carreau P. J. , Paris J. , Guérin P.
Published: July 2010

Heat transfer has been investigated for several Newtonian and non‐Newtonian liquids mixed in a flat bottomed vessel equipped with a screw agitator and a coil acting simultaneously as draft tube and heat exchanger. Heat transfer rates from coil to liquid were determined for different coil designs, rheological properties and operating conditions in the heating and cooling modes. A circulation Reynolds number is defined, the characteristic length being the effective height of the heat exchanger (the coil) and the characteristic velocity being the circulation velocity of the fluid which was determined experimentally. Using this Reynolds number, it was possible to establish a single correlation for the Nusselt number as a function of Reynolds and Prandtl numbers. Geometric ratios do not appear in this correlation which could adequately represent more than 200 experimental data. A similar single correlation could not be obtained when using the conventional mixing Reynolds number. This novel system is shown to be very efficient for handling rheologically complex fluids.
Model based control of a high purity distillation column
Authors: Douglas P. L. , Fountain P. S. , Sullivan G. R. , Zhou W.
Published: July 2010

In this paper, the problem of dual product composition control of an industrial high purity distillation column, a deisohexanizer (DIH), is addressed using a Generic Model Control framework. A dynamic simulation of the DIH was performed for preliminary studies of the performance of different controller strategies/algorithms. The performance of Generic Model Control incorporating different process models was studied. Process models are presented ranging from simple first order approximations to mechanistic short cut distillation models where a tradeoff between model complexity and model adaptivity is investigated. The different controllers were implemented and compared using a dynamic simulation of an industrial deisohexanizer (DIH) to select the best condidate controller. A controller using a nonlinear process model emerged as the best controller and was implemented on the actual process, resulting in improved performance over the original controller. Simulation results and industrial plant data are presented.
Flow Generated by an Aerated Rushton Impeller: Two‐phase PIV Experiments and Numerical Simulations
Authors: Deen Niels G. , Solberg Tron , Hjertager Bjørn H.
Published: July 2010

A two‐camera PIV technique was used to obtain angle resolved velocity and turbulence data of the flow in a lab‐scale stirred tank, equipped with a Rushton turbine. Two cases were investigated: a single‐phase flow and a gas‐liquid flow. In the former case, the classical radial jet flow pattern accompanied by two trailing vortices was observed. In the latter case, the velocity of the radial jet was reduced, and the vortices were diminished by the presence of the gas. Gas cavities clinging to the back of the impeller blades were observed. Both cases were also investigated with the use of three‐dimensional transient CFD simulations. For the single‐phase flow the simulations in the impeller region correspond very well with the experimental data. For the gas‐liquid flow both the mean and fluctuating liquid velocities in the impeller region are well predicted. This is also the case for the mean radial gas velocities.
Operational Characteristics of a New Energy‐saving Impeller for Gas‐Liquid Mixing
Authors: Vlaev Serafim D. , Mavros Paul , Seichter Pavel , Mann Reg
Published: July 2010

The fluid dynamic and mixing characteristics of a new hydrofoil impeller (termed Narcissus) for gas‐liquid mixing are reported. This impeller provides significant energy‐savings in bioreactor applications. Dye‐tracer visualization and CFD simulation have been used to uncover the prevailing flow patterns and the impeller liquid flow map is identified. Flow regime boundaries are shifted from those for disc‐style turbines. A mixing time corresponding to the turbulent mixing regime (i.e., Re > 104) is determined. The power characteristics are measured and compared with experimental data obtained for other impellers. The power number for the turbulent mixing regime for both cylindrical and square vessels was as low as 1. The aeration power at moderate Froude numbers (i.e., Fr < 1) decreased typically by only between 10 and 30%, confirming good gas‐handling capabilities for the new geometry. The gas hold‐up at a given power input was greater than for flat‐blade disc‐style turbines.
On the Comparison between Probability Density Function Models for CFD Applications
Authors: Fissore Davide , Marchisio Daniele L. , Barresi Antonello A.
Published: July 2010

Computational fluid dynamics (CFD) for modelling turbulent reacting flows is based on the Reynolds‐average approach and requires a micro‐mixing model for the chemical source that appears in an unclosed form. Three different approaches are presented in this work: full PDF, finite‐mode PDF and beta PDF. The comparison was carried out in an ideal perfectly mixed batch reactor, that corresponds to the cell considered by CFD codes; competitive‐consecutive and competitive‐parallel reaction schemes were used to test model performances. The comparison showed that the disagreements between the approaches in a certain range of operative conditions are acceptable. The prediction obtained by using the Finite‐Mode PDF model and the Beta PDF model are comparable. Nevertheless the Finite‐Mode PDF model presents the main advantage of being simpler and faster.
On the Applicability of the Grace Curve in Practical Mixing Operations
Authors: Stegeman Yvonne W. , Van De Vosse Frans N. , Meijer Han E. H.
Published: July 2010

Athough the Grace curve is often used to select the material components and optimal flow rates in blending operations, its validity for industrial mixing practice remains to be seen. Among other reasons, the flow field in industrial mixers is not homogeneous. This causes the actual shear/ elongation rate imposed upon a (moving) droplet to be time‐dependent. To investigate the importance thereof, analytical models are used which describe the droplet stretching rate as a function of the droplet shape, viscosity ratio and time‐varying capillary number. Both experiments and model predictions show that droplet breakup can be caused by inhomogeneous flow fields, even if the average capillary number is sub‐critical. Moreover, the model predicts how the critical capillary number is influenced by a non‐spherical initial shape. At higher aspect ratios the critical capillary number can be reduced significantly, especially for higher viscosity ratio droplets.
Dynamic Process Modelling using a PCA‐based Output Integrated Recurrent Neural Network
Authors: Qian Yu , Cheng Huanong , Li Xiuxi , Jiang Yanbin
Published: July 2010

A new methodology for modelling of dynamic process systems, the output integrated recurrent neural network (OIRNN), is presented in this paper. OIRNN can be regarded as a modified Jordan recurrent neural network, in which the past values for certain steps of the output variables are integrated with the input variables, and the original input variables are pre‐processed using principal component analysis (PCA) for the purpose of dimension reduction. The main advantage of the PCA‐based OIRNN is that the input dimension is reduced, so that the network can be used to model the dynamic behavior of multiple input multiple output (MIMO) systems effectively. The new method is illustrated with reference to the Tennessee‐Eastman process and compared with principal component regression and feedforward neural networks.
Using a New Interfacial Area Transport Equation to Predict Interfacial Area in Co‐current Jet Mixers
Authors: Yarbro Stephen L. , Long Richard L.
Published: July 2010

In multiphase operations, such as liquid‐liquid or gas‐liquid systems, the interfacial area affects the interfluid heat, mass and momentum transfer and ultimately, the overall equipment performance. To better understand the mixing process, we developed a multi‐fluid model that predicts interfacial area for kerosene‐water mixtures in co‐current jet mixers. The model has ensemble‐averaged conservation equations for each fluid and includes a transport equation, derived from an overall energy balance, for the interfacial area concentration. In the model, the mechanical energy of the continuous phase creates interfacial area. Comparing the final, one‐dimensional model to experimental data proved the model is accurate. Over 93% of the calculated and experimental data obtained from 0.027 inch and 0.041 inch diameter co‐current jet mixers compared within 15%.
Laminar Mixing in Eccentric Stirred Tank Systems
Authors: Alvarez Mario M. , Arratia Paulo E. , Muzzio Fernando J.
Published: July 2010

Laminar flow structure and mixing patterns in stirred tanks with eccentrically located impellers is examined using tracer visualization techniques and laser induced fluorescence (LIF). The displacement of the shaft from the centerline of the tank has a remarkable effect on the manifold structure of the flow: segregated regions of regular motion observed in concentric systems are destroyed, impeller mid‐plane separatrices are eliminated, and the axial circulation is greatly improved even in systems agitated even by radial impellers.
Unconventional Configuration Studies to Improve Mixing Times in Stirred Tanks
Authors: Ascanio Gabriel , Brito‐Bazán Magdalena , Brito‐De La Fuente Edmundo , Carreau Pierre J. , Tanguy Philippe A.
Published: July 2010

Dynamic perturbations and off‐centered single and dual mixing impeller configurations have been investigated to reduce mixing time with viscous fluids. Mixing times, measured with a color‐discoloration technique based on a fast acid‐base reaction, reveal the presence of both segregated and dead zones. A statistical design approach has been used to evaluate the effect of the impeller position as well as the dynamic conditions. Homogenization is significantly enhanced when a radial flow impeller is used under both off‐centered and dynamic perturbation conditions. In the case of an axial flow impeller, a combination of long clockwise times and short counter‐clockwise times give better mixing times. An enhanced homogenization is also observed when a dual impeller configuration is used.
Investigation of Flow Patterns in Continuous‐flow Stirred Vessels by Laser Doppler Velocimetry
Authors: Mavros Paul , Xuereb Catherine , Fořt Ivan , Bertrand Joël
Published: July 2010

The flow structure of a continuous‐flow reactor stirred by a Rushton turbine was investigated by laser Doppler velocimetry for two different mean residence time‐mixing time ratios. Velocity measurements were obtained for two inlet locations, corresponding to the incoming liquid stream being fed co‐currently or counter‐currently to the flow discharged by the turbine. In all investigated configurations and for all operating conditions, it was found that the flow disruption caused by the incoming liquid stream was observable mainly in the first vessel quarter, which followed the feed‐tube plane. From comparison of the velocities encountered in the various planes in the continuous‐flow reactor to the velocities of the batch reactor, it was also concluded that it may be possible to intensify the usage of the turbine‐stirred vessel by decreasing the characteristic times ratio, without considerable flow by‐pass and/or short‐circuiting problems.
The Influence of Viscosity Ratio on Mixing Effectiveness in a Two‐fluid Laminar Motionless Mixer
Authors: Ventresca Amy L. , Cao Qing , Prasad Ajay K.
Published: July 2010

An investigation of dependence of laminar mixing efficiency of a motionless mixer upon viscosity ratio at low Reynolds number (⩽3) was performed. Viscosity ratios up to 340 were investigated. The liquids were aqueous solutions of carboxymethylcellulose (CMC). Two transparent liquid streams, one marked with a fluorescing dye, were injected into a pipe housing five elements of an SMX mixer. The degree of mixing was evaluated by imaging a downstream cross‐section of pipe using laser induced fluorescence (LIF). Highly resolved spatial variations of fluorescence intensity were recorded using a CCD camera. Mathematical evaluations using correlograms, scale of segregation, COV, and intensity histograms are presented.
An Aqueous Phase Equilibrium Calculation Algorithm
Authors: Makkuni Ajay , Phoenix Aaron V. , Rohani Sohrab
Published: July 2010

A multiphase chemical equilibrium algorithm is developed which can be used with aqueous systems. The algorithm uses an average chemical potential for each species as a reference chemical potential. Incipient phases can be identified and their proximity to appearance can be determined through their tangent plane distance. Illustrative examples include the calculation of CaSO4 solubility and the calculation of vapour pressures above an SO2‐NaCl‐H2O system, including the prediction of a three‐phase equilibrium. The algorithm proved robust and versatile. The appearance of incipient phases was easily tracked. Future work needs to be done to optimize damping/acceleration coefficients in the calculations.
Gas Hold‐Up in Stirred Tank Reactors in the Presence of Inorganic Electrolytes
Authors: Yawalkar Archis A. , Heesink Albertus B. M. , Versteeg Geert F. , Pangarkar Vishwas G.
Published: July 2010

Gas hold‐up (ϵG) in air‐aqueous electrolyte solutions in stirred tank reactors (STR) is correlated using a relative gas dispersion parameter, N/Ncd and a surface tension factor (STF), (c/z)(dδ/dc)2. For electrolyte concentration below transition concentration (ct) a single correlation in the form of ϵG = f(N/Ncd, vvm, STF) shows good agreement with gas hold‐up data over a wide range of system and operating conditions. Above ct no effect of STF on gas hold‐up is observed and the correlation obtained is of the form ϵG = f(N/Ncd, vvm). Data available in the literature on large STR show good fit with the proposed correlation.
Solids Circulation Flux and Gas Bypassing in a Pressurized Spout‐fluid Bed with a Draft Tube
Authors: Xiao Rui , Zhang Mingyao , Jin Baosheng , Liu Xiangdong
Published: July 2010

An experimental study on solids circulation flux and gas bypassing of a spout‐fluid bed with a draft tube at elevated pressures up to 600 kPa was performed in a 200 mm diameter cylindrical steel column with a 608 conical distributor. Glass beads with mean diameter 2.067 mm were used as bed materials to investigate the effect of operating conditions and geometric configuration on the solids circulation flux and the gas distribution between the annulus and the draft tube. A novel technique has been developed to measure the solids fluxes under pressure, and gas (CO2) traces have been employed to investigate gas bypassing characteristics. The solids circulation flux is greatly enhanced when operating pressure and auxiliary gas flowrate are increased, and it is also strongly influenced by geometric configuration. Two experimental relations are proposed for predicting solids circulation flux enhancement factors.
Flow of a FENE Fluid in Packed Beds or Porous Media
Authors: Kozicki William
Published: July 2010

An analysis describing viscoelastic flow of a FENE fluid in packed beds or porous media is presented based on the capillary hybrid model of the flow. A close similarity is revealed between the functional relationship of the reduced elongational viscosity to and that relating the reduced mean elongational viscosity λH ϵ to the Deborah number which is utilized in the flow expressions. The agreement obtained between the predicted and experimentally determined evaluations of the resistance factor, including the effects of variation of polymer concentration, molecular weight and solvent quality was found to be satisfactory. Onset Reynolds numbers for enhanced flow resistance are also predicted successfully.
Prediction of the Crevice Corrosion Incubation Period of Passive Metals at Elevated Temperatures: Part II — Model Verification and Simulation
Authors: Heppner Kevin L. , Evitts Richard W. , Postlethwaite John
Published: July 2010

A flexible computational model for the initiation of crevice corrosion has been developed. Based upon a mechanistic theory, empiricisms do not limit the scope of this work. The model is formulated in a previous paper and this sequel publication showcases the performance of the algorithm. Designed for widespread applicability, passive crevice corrosion of metals may be modelled in suitable electrolytes. The initiation of crevice corrosion has been simulated for several passive metals. Reaffirming past observations, higher temperatures are predicted detrimental to the passivity of metals. The predictions are compared with the experimental work of others and excellent agreement is seen between the simulated chemical composition of the crevice solution and experimental reality.
An Extensive Analysis on the Start‐up of a Simple Distillation Column with Multiple Steady States
Authors: Benz Sonia J. , Scenna Nicolas J.
Published: July 2010

The impact of start‐up procedures on the behaviour of simple distillation columns with multiple steady states is analyzed. A well‐known system with hysteresis is studied in this paper and transient responses for a binary distillation column yielding different steady states during the start‐up operation are shown. Several dynamic simulation results showing an interesting behaviour are presented. Through the examination of the profile evolutions corresponding to given start‐up policies, it can be seen how the column arrives to different steady states. It is shown that it is possible to identify a set of critical values for the start‐up supervision. Also, guidelines of general validity are achieved with the aim of finding the appropriate start‐up policy to obtain the desired solution.
NiMo Supported on Faujasite‐modified Al2O3 as Catalysts for the Hydrotreatment of a Light Cycle Oil/Straight Run Gas Oil Mixture
Authors: Marín Celia , Escobar José , Galván Ernesto , Murrieta Florentino , Zárate René , Cortés Víctor
Published: July 2010

A study on the hydrotreating performance of sulfided NiMo supported in NH4+Y‐ and H+Y‐modified Al2O3 is reported. The effect of the addition of the corresponding NiMo‐exchanged zeolites was also investigated. The materials were characterized (by N2 physisorption and surface acidity measurements) and evaluated in the upgrading of a middle distillates (LCO‐SRGO) mixture under industrial conditions. The main effects of the integration of the NiMo‐exchanged zeolite (from the NH4+‐faujasite) were an improvement of textural properties and the creation of strong surface Lewis sites. The corresponding sulfided formulations showed higher hydrodesulfurization and hydrodearomatization activities than the catalyst prepared from the protonic zeolite.
A Trend to the Production of Calcium Hydroxide and Precipitated Calcium Carbonate with Defined Properties
Authors: Lõhmus Hilja , Räni Ahto , Kallavus Urve , Reiska Rein
Published: July 2010

In this paper, production of precipitated calcium carbonate (PCC) with required particle size and morphological structure, along with its dependence on technological parameters and the properties of Ca(OH)2, is discussed. The effect of the reaction environment on the kinetics of CaO hydration and the formation of crystals in water suspension was established. A remarkable difference in the system's restoration ability after stirring was observed. The hydration process is initially controlled by a kinetic mechanism, followed by a diffusion‐controlled process. The dissolution speed of lime hydrated to suspension is eight times higher than that of lime hydrated to powder. Particles of hydrated lime appeared in various forms.
Neural Optimization of Fed‐batch Streptokinase Fermentation in a Non‐ideal Bioreactor
Authors: Patnaik Pratap R.
Published: July 2010

Microbial fermentations involving two or more kinds of competing cells and operating under realistic conditions are difficult to monitor, model and optimize by model‐based methods. They deviate from ideal behavior in two significant aspects: incomplete dispersion in the broth and the influx of disturbances. The approach here has been to optimize the filtered noise and dispersion on‐line through neural networks. This method has been applied to the fed‐batch production of streptokinase (SK). The culture has two kinds of cells — active (or productive) and inactive — and their growth is inhibited by the substrate and the primary metabolite (lactic acid). Using simulated data, the fermentation was optimized by a system of three neural networks, updated continually during successive time intervals. Such sequential optimization with dynamic filtering of inflow noise generated better cell growth and SK activity than static optimization and even an ideal fermentation.
Thermal Sensor to Monitor Mechanical Properties in Polymer/Fiber Composite Molding
Authors: Rouison David , Varejka Milena , Picot Jules
Published: July 2010

Multi‐layered samples of 1) continuous fiber axially aligned and 2) random oriented mat glass fiber composites were manually prepared for a fiber content ranging from zero to 20% (vol.). The uniaxially aligned samples displayed linear relations between both normalized elastic modulus and normalized thermal conductivity, and fiber content, for axially applied load and heat flux. For the random mat composite samples, similar results were obtained, with symmetry displayed in the plane of the mat. In both cases, measured axial thermal conductivity permits an evaluation of the axial elastic modulus. The Mathis surface probe used (US patent #5,795,064) is demonstrated as a non‐intrusive indirect method of obtaining thermal conductivity for heat flux parallel (i.e. axial or transverse) to the plane of a sample. The method shows potential for use as an in‐line monitoring device for the mechanical properties of molded composites.
A Mathematic Model for Direct Causticization of Na2CO3 with TiO2 in a Semi‐batch Reactor
Authors: Zeng Le , Van Heiningen Adriaan R. P.
Published: July 2010

A mathematic model was developed for direct causticization of sodium carbonate with titanium dioxide in a semi‐batch reactor. The model predictions of the titanate yield and pentatitanate yield showed a reasonable agreement with the experimental data from a pilot‐scale fluidized bed operating in semi‐batch mode. The rate constant of the present model was generally consistent with those obtained from the small‐scale batch experiments in the literature. A new rate constant considering carbonate conversion to pentatitanate was introduced. All the results provided support that the solid‐state direct causticization of sodium carbonate with titanium dioxide in a semi‐batch fluidized bed follows the shrinking‐core diffusion model.
On the Characteristic Drying Rate Approach to Correlating Experimental Results of the Drying of Moist Porous Materials
Authors: Chen Xiao Dong
Published: July 2010

Schlunder's model of a surface, is the only fundamental attempt to explain the constant drying rate phenomena, for materials with pore sizes of a few microns. Here, a direct comparison between this approach and the conventional mass transfer (CMT) theory has been made, by extending the approach to incorporate cell sizes of food, plant materials and to low water contents. Contrast to CMT, the extended Schlunder's model analysis suggests that the boundary layer thickness have an effect on the relative drying rate. Some new experimental results are also presented to support one viewpoint regarding the characteristic drying rate method.
Compatibilization of Polymer Blends
Authors: Utracki Leszek A.
Published: July 2010

Most polymer blends are immiscible and need to be compatibilized. The compatibilization must accomplish: (i) optimization of the interfacial tension; (ii) stabilize the morphology against high stresses during forming; and (iii) enhance adhesion between the phases in the solid state. Compatibilization is accomplished either by addition of a compatibilizer or by reactive processing. This review will focus on the three aspects: description of the interphase, compatibilization by addition and reactive compatibilization.
Morphology in Immiscible Polymer Blends During Solidification of an Amorphous Dispersed Phase under Shearing
Authors: Deyrail Yves , Michel Alain , Cassagnau Philippe
Published: July 2010

Solidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene‐methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break‐up times of PC fibers were taken into account. Shear rate and quenching‐time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching.
Dependence of the Morphology Development on the Kinetics of Reactive Melt Blending of Immiscible Polymers
Authors: Yin Z , Koulic C , Pagnoulle C , Jérôme R
Published: July 2010

Poly(methyl methacrylate) (PMMA) containing 50 wt% of anthracene (anth) labeled reactive PMMA chains [thus end‐capped by an anhydride (anh) or an isocyanate (NCO)] has been melt blended with polystyrene containing 33 wt% of chains end‐capped by an aliphatic amine (PS‐NH2) at 180°C. Conversion of anth‐PMMA‐anh and anth‐PMMA‐NCO into PMMA‐b‐PS copolymers has been determined by SEC with a UV detector. The interfacial reaction mainly occurs in the initial mixing stage (⩽1.0 min), although at a rate which depends on the reactive groups attached to PMMA. Moreover, this interfacial reaction rate controls how the phase morphology is developed.
Synthesis of Oligoester α,ω‐diols by Alcoholysis of PET through the Reactive Extrusion Process
Authors: Michel Alain , Cassagnau Philippe , Dannoux Morgane
Published: July 2010

The alcoholysis of PET with diols in the presence of dibutyltinoxide was carried out in a twin‐screw extruder with residence times of 1 min and without solvent. The reaction led to scissions of PET chains and to the synthesis of oligoester α,ω‐diols with average number molecular weights of about 1000 g·mol—1 characterised by conventional techniques such as NMR, SEC and MALDI‐TOF. The alcoholysis kinetics was studied with a rheological tool under selected conditions, and it was shown that this reaction is quite compatible with the residence times in an extruder. This study clearly shows that the oligoesters synthesised by reactive extrusion have characteristics similar to the oligoesters synthesised by batch processes over many hours. Furthermore, the melting temperature of these oligoesters can be controlled between room temperature and 220°C by using diols with different structures for the alcoholysis.
Polymer‐Clay Nanocomposites Based on Blends of Polyamide‐6 and Polyethylene
Authors: Mehrabzadeh Mahmood , Kamal Musa R.
Published: July 2010

The preparation of polyamide‐6/clay, high‐density polyethylene/clay, and high‐density polyethylene/ polyamide‐6/clay nanocomposites is considered. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier Transform Infrared (FTIR) measurements show that the clay enhances the crystallization of the γ‐form of polyamide‐6. The clay also acts as a nucleation agent and causes a reduction of spherulitte size. Scanning electron microscopy (SEM) analysis of fracture surfaces shows that the clay reduces the PA‐6 particle size in the HDPE/PA‐6/clay nanocomposites and changes the morphology. Mechanical properties and the effect of maleated polyethylene are also reported.
Quantitative Analysis of Mixer‐Type Rheometers using the Couette Analogy
Authors: Aït‐Kadi Abdellatif , Marchal Philippe , Choplin Lionel , Chrissemant Anne‐Sophie , Bousmina Mosto
Published: July 2010

A procedure based on a Couette analogy, to quantitatively analyze torque/rotor speed data in order to extract viscosity/shear‐rate curves using non‐conventional geometries is presented. It is first validated using a relatively simple geometry for which the equivalent internal radius used in the analogy can be analytically obtained. The results showed that the equivalent internal radius depends only slightly on the nature of the fluid and that there is an optimal radial position r* in the analog Couette gap where the calculations can be easily performed for computing the viscosity/shear‐rate data from torque/rotational speed data. The experimental results with complex geometries and complex fluids are found to coincide, within experimental errors, with those obtained using standard geometries over a wide range of shear rates. The approach is also found to be very useful to evaluate shear‐rate and viscosity data in Couette viscometers when large gaps are used with non‐Newtonian fluids.
Diffusion of One‐ and Two‐Component Fluids into Polymeric Membranes
Authors: Afif Ali E. L. , Grmela Miroslav
Published: July 2010

The starting point of this paper is a model of the non‐Fickian diffusion of a simple fluid into a polymeric medium that has been introduced in El Afif and Grmela (2002). The model is extended to a mixture consisting of two simple fluids and one polymeric medium. The effects of the polymeric medium on diffusion are included in the formulations through the use of relative momenta playing the role of internal variables. In ternary mixtures, new phenomena arise due to cross‐coupling effects. As a consequence, the single diffusion Deborah number in binary mixtures becomes a 2 × 2 matrix in ternary mixtures. Two specific examples for which experimental data are available are investigated in detail.
Peculiarities of the Thermodynamics of Electrolyte Solutions: A Critical Discussion
Authors: Wilczek‐Vera Grazyna , Vera Juan H.
Published: July 2010

Differences in the thermodynamic treatment of electrolyte and nonelectrolyte solutions are highlighted. The relations between expressions for concentrations are stated and the need to consider the presence of ions is emphasized. Examples are presented to show that the activity coefficient of a particular ion depends on the nature of the other ions in the solution. An overview is given of the state of development — and shortcomings — of methods to measure the activity coefficient of individual ions. Pitfalls in the use of polynomials to evaluate the mean ionic activity from measurements of the activity of the solvent are emphasized and solutions proposed. The interpretation of the mean ionic activity coefficient of weak electrolytes is discussed. The relation between the excess Gibbs energy and the activity coefficients of the species in solutions is reviewed and the relation between the McMillan‐Mayer and Lewis‐Randall frameworks is commented. An abstract of the basic equations for electrolyte solution thermodynamics is appended.
Thermodynamics and Stoichiometry of Reactions between Hydrogen Sulfide and Concentrated Sulfuric Acid
Authors: Wang Hui , Dalla Ivo G. , Chuang Lana , Chuang Karl T.
Published: July 2010

A thermodynamic analysis of the possible reactions between hydrogen sulfide and concentrated sulfuric acid shows that four reactions are feasible. However, only two of these reactions apparently occur in experiments at 1 atm and 0°C to 150°C. Hydrogen sulfide is first oxidized by molecular sulfuric acid, forming SO2, sulfur and water, and then the H2S may react with the dissolved product, SO2, to generate sulfur and water. The stoichiometry of the consecutive reactions and their dependence on acid concentration were determined experimentally using mass balance measurements. The results of this study suggest a possible alternative method for sulfur removal and recovery that has more advantages.
Free Convective Mass Transfer Behaviour of Inclined Cylinders with Active Ends
Authors: Nirdosh Inderjit , Sedahmed Gomma
Published: July 2010

Rates of mass transfer at inclined cylinders with active ends were determined under natural convection conditions by measuring the limiting current of copper deposition from acidified copper sulphate. Physical properties of the solution, cylinder dimensions and inclination were varied to produce a ScGr range of 1.53 × 109 to 7 × 1010. Under these conditions the data for different orientations were correlated by Sh = 1.075 (ScGr)0.242. The characteristic length used in obtaining Sh and Gr was calculated by dividing the cylinder surface area by the cylinder perimeter projected onto the horizontal plane. At high CuSO4 concentrations a reasonable agreement was found between the experimental rate of mass transfer and that calculated by summing the rate of mass transfer at individual surfaces of the cylinder. Deviations were observed at low CuSO4 concentrations, and the possible causes of the deviations were explained.
Propylene Solubility in Toluene and Isododecane
Authors: Dariva Cláudio , Lovisi Humberto , Mariac Luis C. Santa , Coutinho Fernanda M. B. , Oliveira José Vladimir , Pinto José Carlos
Published: July 2010

Propylene solubility in toluene and isododecane (2,2,4,6,6‐Pentamethylheptane, CA Registry# 13475‐82‐6) was measured at different temperatures and pressures, similar to the ones normally used to carry out propylene polymerizations through metallocene and Ziegler‐Natta catalysts. Experimental data were obtained with a gravimetric method, where experimental liquid phase compositions are measured at known temperature and pressure conditions. The experimental data were modeled with two different models: the Wilson excess Gibbs free energy model and an empirical model. Both modeling approaches may be recommended for analysis of kinetic data obtained for slurry propylene polymerizations in toluene and isododecane.
Mixing Time in a Short Bubble Column
Authors: Ravinath M , Kasat Gopal R. , Pandit Aniruddha B.
Published: July 2010

Mixing time measurements have been carried out in a 0.2m I.D. short bubble column (Hc/D ⩽ 5) with different spargers and for different clear liquid height to diameter (HC/D) ratios. Superficial gas velocity has been varied in the range of 0.01m/s to 0.1m/s. Effect of bulk fluid viscosity on the mixing time has also been studied. The circulation cell model, with two fitted parameters viz. number of circulation cells, S and the inter‐cell exchange velocity, Ve, has been used to predict and explain the variation in mixing time and the flow pattern in the short bubble column for different types of spargers.
Interfacial Area and Liquid‐Side Volumetric Mass Transfer Coefficient in a Downflow Bubble Column
Authors: Mandal Ajay , Kundu Gautam , Mukherjee Dibyendu
Published: July 2010

An experimental investigation was made to measure interfacial area, a, and liquid‐side volumetric mass transfer coefficient, kLa, in a downflow bubble column by chemical methods viz., absorbing CO2 in aqueous sodium hydroxide and sodium carbonate/bicarbonate buffer solution respectively. The effect of gas and liquid flowrate and nozzle sizes on a and kLa were investigated. The experimental data obtained in the present system were analyzed and correlations were developed to predict a and kLa in terms of superficial gas velocity. The variation of a and kLa with specific power input were shown in graphical plot and compared with other gas‐liquid systems.
Ultrasonic Measurement for Two/Three‐Phase Flow Detection
Authors: Zheng Ying
Published: July 2010

Ultrasonic technique offers a good potential for phase holdup measurements in multiphase systems. Experiments were performed in an expanded fluidized bed consisting of water, air bubbles and/or glass beads. In this research note, the instantaneous signals of ultrasound were, for the first time, analyzed for the purpose of phase holdup determination. The results show that the fluctuations of the speed and attenuation of ultrasound are a well‐defined function of solid and gas holdups in a multiphase system.
Extraction of Copper, Nickel and Cobalt from Indian Ocean Polymetallic Nodules
Authors: Agarwal Har P. , Goodrich James D.
Published: July 2010

Various processes used for the recovery of valuable metals such as copper, nickel and cobalt from marine manganese nodules has been reviewed and an effective process for their extraction has been described.
Recovery of Tritium from Wastewater Generated by Decommissioning of Gas Cooled Reactors (GCR)
Authors: Takeshita Kenji , Nnakano Yoshio , Shimizu Masami
Published: July 2010

The recovery of tritium from wastewater generated by the decommissioning of a 166‐MWe GCR, Tokai‐1, nuclear reactor was evaluated. The dimensions of two tritium separation columns, water distillation process and hydrogen‐isotope exchange with hydrophobic Pt‐catalyst, were evaluated numerically under the assumptions that the recovery of tritium from the wastewater would be completed in five years and the wastewater after the recovery of tritium would be suitable for release into the environment. It was found that, in addition to lower steam, the column was smaller than that for the water distillation process. The hydrogen‐isotope exchange process was suitable for the treatment of wastewater, not only for a process design point of view but also for a reduction of energy consumption.
Flow Regime Identification in a Bubble Column Based on both Kolmogorov Entropy and Quality of Mixedness Derived from CAERPT Data
Authors: Nedeltchev Stoyan , Kumar Sailesh B. , Dudukovic Milorad P.
Published: July 2010

Computer‐automated radioactive particle tracking (CARPT) data obtained in a 0.162 m air‐water bubble column operated at ambient pressure have been analysed. The superficial gas velocity (Ug) has been varied in the range 0.02‐0.12 m/s under constant liquid height 1.04 m. A perforated plate (82 holes ø 0.4 mm, free plate area 0.05 %) distributor has been used. The Kolmogorov entropy (KE) vs.Ugallows identification of the transition velocity (Utrans= 0.064 m/s) between bubbly and transition regimes. KE models for both regimes have been also developed. The quality of mixedness (QM) concept shows that QM(upper zone) ⊕ QM(lower zone) atUtrans= 0.064 m/s.
Bubble Dynamics Measurements Using Four‐Point Optical Probe
Authors: Xue Junli , Al‐Dahhan Muthanna , Dudukovic M. P. , Mudde R. F.
Published: July 2010

By conducting an analysis of the measurement errors it was found that bubble dynamics obtained by two‐point probes can be highly inaccurate. A four‐point optical probe with appropriate data processing algorithm has been developed so that the bubble velocity vector can be obtained. This probe provides directly the value of specific gas‐liquid interfacial area. However, for obtaining accurate values of bubble velocity and size, the four‐point probe must be calibrated by a CCD camera at the same conditions. Calibration columns have been developed for this purpose where the bubble size and velocity can be varied to calibrate the measurements by the four‐point optical probe against a CCD camera.
Dynamics of a Bubble Column: Influence of Gas Distribution on Coherent Structures
Authors: Harteveld Wouter K. , Mudde Robert F. , Van Den Akker Harrie E. A.
Published: July 2010

The influence of the pattern of gas distribution on the dynamics of a bubble column is studied. LDA and glass fiber probe measurements were performed in a 15 cm column, aerated in well‐controlled patterns using a special distributor. Superficial gas velocities of 0.015 m/s to 0.023 m/s were investigated. Uniform aeration gives very uniform gas distribution. The familiar large‐scale circulation and structures are absent. Non‐uniform gas‐injection introduces dynamic structures in the entrance region. Large‐scale structures are absent in the flow above the entrance region, independent of the gas injection pattern.
Gas Holdup in a Fiber Suspension
Authors: Su Xuefeng , Heindel Theodore J.
Published: July 2010

This paper investigates the effects of fiber mass fraction and length on gas holdup and flow regime transition. The experiments are performed using three different Rayon fiber lengths (3, 6, and 12 mm) over a range of superficial gas velocities (Ug ⩽ 18 cm/s) and a range of fiber mass fractions (0 ⩽ C ⩽ 1.8%) in a 15.24 cm diameter bubble column, in which air is continuously bubbled through a fixed volume of a fiber suspension. Experimental results show that increasing the fiber mass fraction tends to decrease the overall gas holdup when the fiber mass fraction is less than a certain value, which depends on fiber length. Fiber length influences the gas holdup when C ⩽ 1.4%, and increasing fiber length reduces the overall gas holdup. Homogeneous, transitional, and heterogeneous flow conditions are observed at low fiber mass fractions, but when C ⩽ 0.6%, purely heterogeneous flow conditions are observed. The flow regime transition is not significantly affected by fiber length.
A Method for the Detection of Defluidized Zones in Slurry Bubble Columns
Authors: Emami Ahad , Briens Cedric
Published: July 2010

The formation of defluidized zones was studied in a laboratory slurry bubble column equipped with heat transfer probes. The probes were small thermistors 2.4 mm in diameter. Dionized water and air were used as a liquid and gas phase, respectively. Solids were fine ceramic particles with mean size of 19.2 μm and density of 2244 kg/m3. The effects of solids holdup (up to 30 wt% on gas free basis), gas superficial velocity (0.01‐0.09 m/s), sparger height (0.01‐0.09 m) on defluidized zones formation was studied. Cycle analysis of the local heat transfer fluctuations reliably detected the local formation of defluidized zones for each condition.
The Mechanisms of Bubble Coalescence in a Non‐Newtonian Fluid
Authors: Lin Tsao‐Jen , Lin Gen‐Ming
Published: July 2010

The coalescing mechanism of two in‐line oblate‐cusped bubbles rising in a non‐Newtonian fluid has been qualitatively and quantitatively studied by using particle image analyzer. Through effects of the shear thinning and viscoelasticity on the flow structure, the acceleration of the trailing bubble to the leading bubble is evident. While two bubbles are getting closer, the drained liquid is circulated to the back of the trailing bubble. To encounter these dynamic flow structures, the bubble shape evolution for the leading bubble in each stage is from oblate‐cusped to elongated oblate‐cusped, to invert pentagonal, and to oblate. Suppressed by the trailing bubble and the flow structure, the shape of leading bubble changes from oblate‐cusped to oblate, to flattened oblate, and to flattened oblate with concave surface.
Bubble Motion in Non‐Newtonian Fluids and Suspensions
Authors: Frank Xavier , Li Huai Z. , Funfschilling Denis , Burdin Florence , Ma Youguang
Published: July 2010

The present paper reports a study of the motion of air bubbles in both non‐Newtonian fluids and fluid‐solid (laponite) suspensions. Quantitative information concerning the bubble rise velocity was obtained. In particular, the acceleration mechanism of the rise velocity in fluids was investigated by both a modern technique — Particle Image Velocimetry and a classical method — birefringence visualization. An analytical modeling is proposed to compute the rise velocity of a bubble train with the memory effects. Finally, the visualization demonstrates that the bubble shape and rise velocity in a suspension are very complicated due to the displacement of solid particles by bubbles.
Dynamic Gas Disengagement in a High‐Pressure Bubble Column
Authors: Jordan Uwe , Saxena Alok K. , Schumpe Adrian
Published: July 2010

Bubble disengagement after stopping the gas supply is analyzed based on the concept of constant slip velocity; it is compared with the approaches used by previous investigators. The technique has been applied to study the gas density effect (0.17 to 46.6 kg·m—3) on the gas hold‐up structure in a bubble column with organic liquids (toluene, ethanol, 1‐butanol, decalin) and tap water. With increasing gas density, the large bubble rise velocity decreases; this indicates smaller bubble size. The small bubble hold‐up is correlated with the gas and the liquid properties whereas the large bubble hold‐up is hardly affected.