bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study and CFD Simulation of Hydrodynamic Behaviours in an External Loop Airlift Slurry Reactor
Authors: Wang Tiefeng , Wang Jinfu , Jin Yong
Published: July 2010

The local hydrodynamic behaviours in an external loop airlift slurry reactor, including the gas holdup, bubble rise velocity, bubble size, were measured with a fibre optic probe. The liquid circulation velocity was measured with an ultrasound Doppler velocimetry. Two‐dimensional simulations were carried out in the framework of Two‐Fluid formulation coupled with a k‐ϵ turbulence model. The lateral forces and interphase turbulence were taken into account and good agreement between the experimental and simulation results was obtained. The simulations show that the lateral forces and interphase turbulence have noticeable influence and should be included in the CFD model.
Modelling of Inclusion Re‐entrainment During Filtration
Authors: Kocaefe Duygu , Murray‐Chiasson Audrey , Kocaefe YaşAr , Waite Peter
Published: July 2010

During filtration, the release of deposited inclusions back to the main flow under certain conditions is called re‐entrainment. In this study, re‐entrainment was investigated experimentally in a pilot scale filter under continuous flow as well as interrupted flow conditions. Also, one‐dimensional mathematical model simulating the global behaviour of filter bed was developed and validated by comparing its predictions with the experimental results. This model solves the mass conservation equations for the inclusions. A deposition/re‐entrainment sub‐model was incorporated into the filter model. The model predictions were in good agreement with the experimental data.
Single‐stage Treatment in Selective Hydrogenation of Acetylene over CDS Type of Pd‐Ag/Al2O3 Catalyst
Authors: Chen Wen‐Shing , Wei Kuo‐Ming
Published: July 2010

The (computer designed shape) CDS type of Pd‐Ag/Al2O3 catalyst in single‐stage reactor provides superior catalytic activity and selectivity of ethylene in comparison with those of existed two‐stage reactors packed with G‐58B catalyst under industrial operating conditions. In this research, the contents of palladium and silver of catalysts were analyzed by inductive coupling plasma (ICP). The X‐ray photoelectron spectroscopy (XPS) showed that Pd‐Ag alloy has been formed. Higher yield of ethylene may be interpreted by both geometric and electronic effect induced from silver metal. By means of Pyrolysis/GC/MS analysis of used catalysts, the components of carbonaceous deposits were found to be n‐alkenes, including n‐C8 ∼ n‐C16 or n‐C18, which may result from oligomerization of acetylene.
Distributions of Crystal Size from DSC Melting Traces for Polyethylenes
Authors: Feng Lijun , Kamal Musa R.
Published: July 2010

Melting curves, obtained by differential scanning calorimetry, are used to estimate crystal size distributions. The proposed theoretical analysis is applied to different types of polyethylene, including high‐density polyethylene (HDPE), metallocene catalyzed linear low‐density polyethylenes (m‐LLDPE), blends of m‐LLDPEs, and Ziegler‐Natta catalyzed LLDPEs (ZN‐LLDPE). Theoretical predictions are in agreement with experimental results. A generalized melting temperature equation successfully predicts the melting temperatures of all the LLDPEs, although it was initially proposed for homogeneous copolymers with excluded comonomers. A new definition of the heat of fusion for pure crystals is proposed. This heat of fusion can be calculated from the average crystal size or the crystal size number distribution.
A Comparative Study of Combined Feedforward/Feedback Model Predictive Control for Nonlinear Systems
Authors: Chu Ji‐Zheng , Jang Shi‐Shang , Chen Yu‐Nan
Published: July 2010

Model predictive control (MPC) provides a natural framework to realize feedforward and feedback control for nonlinear systems where the effect of disturbances (DVs) cannot be separated from that of manipulated variables (MVs). This study examines the performance of MPC with measured DVs as partial inputs of the model used, which is termed as combined feedforward/feedback MPC (CMPC) in contrast to conventional MPC using a model without input of any measured DV. In the simulation of a pH process, we demonstrate the clear superiority of CMPC over MPC. In the experiment with a bench‐scale ethanol and water distillation column, CMPC and MPC using artificial neural network (ANN) models are applied to the dual temperature control problem. External recurrent neural networks (ERNs) with and without a measured DV (feed rate of the column) as their partial input are built and employed in the experiment, with a result that inclusion of the measured DV in the model makes CMPC perform significantly better than MPC. To strengthen practical experience in applying ANN‐based MPC, a detailed procedure of the experiment is also documented.
Gas Hold‐up and Liquid Circulation Velocity in Gas‐Liquid‐Solid Airlift Reactors
Authors: Popović Milan K. , Kiefner Andreas W. , Bajpai Rakesh K.
Published: July 2010

Simple empirical correlations for gas hold‐up and liquid circulation velocity in two‐ and three‐phase airlift reactors are presented in this paper and their applicability has been demonstrated. The empirical correlations are good alternatives to the semi‐theoretical drift‐flux approach to predictions of gas hold‐ups and liquid circulation velocities in airlift reactors.
Decolorization of RR‐120 Dye Using Ozone and Ozone/UV in a Semi‐Batch Reactor
Authors: Kazemi Mohammad , Mohammadzadeh Jafar S. Soltan , Khoshfetrat Ali B. , Kaynejad Mohammad A.
Published: July 2010

Treatability of RR‐120 aqueous dye solutions using O3 and O3/UV was studied in a bench scale set‐up. Reduction in colour and chemical oxygen demand (COD) under various pH and initial dye concentrations were investigated. Pseudo first order reaction rate was satisfactorily used for kinetic interpretations in destruction of the dye. The results showed that decolorization with O3 was faster at neutral pH values. While use of UV had a small effect on ozonation at low pH values, UV radiation had a considerable effect at pH values of 7 and above. It was found that ozone utilization efficiency of higher than 95% could be attained in the experimental set up.
The Yield Stress of Gas/Liquid/Fibre Suspensions
Authors: Pettersson Johan , Rasmuson Anders
Published: July 2010

Yield stress measurements of gas/liquid/fibre suspensions, were conducted to examine the effect of gas concentration as well as fibre concentration. Obtaining a well mixed stable pulp suspension with gas was difficult. A transparent model system consisting of glass fibres submersed in refractive index matched liquid gave stable suspensions and had the additional advantage of allowing visual observations. The measurements were performed in a baffled shear tester and concentrations were in the range of 0–12.5% vol. gas and 8–14% wt. fibres. Results show that yield stress decreases with increasing gas fraction for constant fibre concentrations. Since the fibre concentration is defined in the liquid phase, the amount of fibres decreases with increasing gas concentration. This fact alone partly explains the decrease in yield stress, but the gas also has a direct impact on the decrease in yield stress. Further, as expected, the yield stress increases with increasing fibre concentrations when the gas fraction is kept constant.
A Review of Recent Technological Advances in the Brightening of High‐Yield Pulps
Authors: Ni Yonghao
Published: July 2010

Peroxide brightening/bleaching is an important unit operation for pulp and paper mills producing value‐added paper grades containing bleached mechanical pulps. In this paper, a number of process innovations have been discussed. They include:

hydrosulphite assisted chelation process, the so‐called Qy process;

DTPA spray;

PN2process;

PMprocess;

Mg(OH)2‐based peroxide process.

It will be shown that these processes can improve the peroxide brightening/bleaching processes in terms of (1) decreasing the production cost, (2) improving the product quality, and (3) decreasing the environmental impact.
Hydrodynamic Characteristics of a Powder‐Particle Spouted Bed with Powder Entrained in Spouting Gas
Authors: Zhu Qunyi , Lim C. Jim , Epstein Norman , Bi Hsiaotao T.
Published: July 2010

Spouting of 3.7 mm polyvinyl chloride particles in a cone‐based cylindrical column is subjected to entrainment of FCC powder in the spouting air. It is found that the powder entrainment reduces the minimum spouting velocity, increases the bed pressure drop and reduces the maximum spoutable bed height. At any given bed height and value of U/Ums, there is a critical value of powder loading ratio above which spouting gives way to slugging.
Écoulement de Taylor‐Couette en géométrie finie et à surface libre
Authors: Ammar Mahamdia , Ahcène Bouabdallah , Eddine Skali Salah
Published: July 2010

Les réacteurs de type de Taylor‐Couette sont une application relativement récente dans le domaine du génie des procédés. La stabilité et la structure de l'écoulement dans ce dispositif sont examinées sous les effets combinés de la surface libre et de la hauteur de fluide dans l'espace annulaire. L'exploration des régimes d'écoulement est réalisée en fonction du nombre de Taylor Ta pour différentes valeurs du rapport d'aspect Γ. Au moyen de la vélocimétrie ultrasonore (UVP) on détermine le profil moyen de vitesse axiale et la longueur d'onde axiale. On procède également à l'analyse spectrale par transformée rapide de Fourier des fluctuations associées aux valeurs moyennes de la vitesse en vue d'analyser la structure de l'écoulement. On vise particulièrement à vérifier, selon la hauteur de remplissage et la vitesse de rotation imposée, la présence ou l'absence de l'onde azimutale. On met en évidence les effets de la surface libre et du rapport d'aspect sur les conditions d'apparition de la deuxième instabilité. L'analyse des fluctuations montre que l'apparition du régime d'ondes azimutales (wavy mode) est retardé quand le rapport d'aspect diminue. En dessous d'une valeur critique notée Γc = 10, le régime d'ondes azimutales n'est plus observé.
On Criteria for Occurrence of Azeotropes in Isothermal and Isobaric Binary Systems
Authors: Missen Ronald W.
Published: July 2010

Criteria are developed for the occurrence of azeotropes in binary nonelectrolyte systems for both isothermal and isobaric situations in terms of liquid‐phase activity coefficients at infinite dilution (γ∞). In the case of isothermal systems at temperature T, for a positive azeotrope, γ∞lvc≥ p*mvc/p*lvc where lvc refers to the less volatile component, mvc to the more volatile component, and p* to saturation vapour pressure at T; for a negative azeotrope, γ∞mvc≤ p*lvc/p*mvc. In the case of isobaric systems at pressure P, for a minimum‐boiling azeotrope, γ∞lvc(TBmvc) ≥ P/p*lvc(TBmvc), where TB refers to the boiling point at P; for a maximum‐boiling azeotrope, γ∞mvc (TBlvc) ≤ P/p*mvc(TBlvc). The criteria are also given in terms of the parameters of selected correlations for the excess molar Gibbs function (gE). Examples of the use of the criteria are provided. Various methods that generate values of γ∞ can be used in conjunction with the criteria, for example, in screening procedures.
Attainment of PI Achievable Performance for Linear SISO Processes with Deadtime by Iterative Tuning
Authors: Goradia D. B. , Lakshminarayanan S. , Rangaiah G. P.
Published: July 2010

This work presents a practical scheme to attain PI achievable performance (the performance achievable with a proportional integral (PI) controller) for linear SISO processes with dead time driven by stochastic disturbances. It uses a combination of a quantitative measure called Control Loop Performance Index (CLPI) and signature plots of the closed loop disturbance impulse response (IR) to arrive at PI achievable performance in an iterative manner. The proposed methodology requires only routine operating data and knowledge of the process delay, and its efficacy is illustrated through several case studies.
Recyclage d'un déchet, une boue rouge, comme catalyseur pour l'élimination des composés organiques volatils
Authors: Lamonier J. F. , Wyrwalski F. , Leclercq G. , Aboukaïs A.
Published: July 2010

Le potentiel catalytique d'une boue rouge, déchet de la fabrication de l'alumine, a été évalué dans l'oxydation des COV et notamment du toluène. Séchée, elle contient essentiellement Al(OH)3 et Fe2O3. Il s'est avéré qu'une calcination de la boue rouge sous flux d'air à 500 °C conduit à la formation de Al2O3 et Fe2O3, oxydes qui sont actifs et sélectifs en CO2 dans la réaction d'oxydation du toluène. L'activité de la boue rouge peut être directement corrélée à la quantité de fer présente dans l'échantillon. En effet, la vitesse spécifique (par gramme de Fe2O3) de la réaction chimique en présence de la boue rouge est similaire à celle observée en présence d'un oxyde de fer Fe2O3 pur.
A Study on Hydrodynamics and Heat Transfer in a Bubble Column Reactor with Yeast and Bacterial Cell Suspensions
Authors: Kantarci Nigar , Ulgen Kutlu O. , Borak Fahir
Published: July 2010

Hydrodynamics and heat transfer experiments were carried out in a slurry bubble column with air‐water‐yeast cells and air‐water‐bacteria cells systems to investigate gas hold‐up, bubble characteristics and heat transfer coefficients with cell concentrations of 0.1% w/w and 0.4% w/w and superficial gas velocity up to 0.20 m/s. The gas hold‐ups and heat transfer coefficients were found to increase with increasing gas velocity and cell concentration. The heat transfer coefficients were higher at the centre of the column as compared to the near wall region. The development of empirical correlations to predict the heat transfer coefficient in two‐ and three‐phase systems was carried out with ±15% confidence interval at most.
Dispersion and Mass Transfer Effects on the Performance of an Immobilized Lipase Packed Bed Reactor During the Hydrolysis of Rice Bran Oil
Authors: Murty V. Ramachandra , Bhat Jayadev , Muniswaran P. K. A. , Sivasankaran S.
Published: July 2010

The performance of an immobilized packed bed reactor for the hydrolysis of rice bran oil has been investigated and can be well described by a dispersion model with an average standard deviation of 0.0388. Global mass transfer coefficients estimated using the model and experimental data ranged from 0.095‐0.482 min−1, depending on substrate flow rates. A dimensionless mass transfer correlation between the Sherwood number and the Reynolds number was obtained as NSh = 3.96 ×NRe2.07.
Improvement of the Fluidizability of Cohesive Powders through Mixing with Small Proportions of Group A Particles
Authors: Ajbar A. , Alhumazi K. , Asif M.
Published: July 2010

The gas fluidization behaviour of fine cohesive powders, classified as Geldart group C, is known to be characterized by cracks and channels leading to severe non‐homogeneities in the bed. Geldart group A particles, on the other hand, are known to show more homogeneous and regular fluidization behaviour. This paper studies the effects of the addition of small proportions of group A on the fluidization behaviour of a group C powder. Differential pressure fluctuations data at a sampling frequency of 200 Hz were recorded for two cases. In the first case, the bed contained only group C powder while in the second case small amounts of group A particles were added to the existing group C powder. Visual/image observations coupled with time series analysis showed that the addition of small proportions of group A particles substantially improved the fluidization behaviour of the bed even at low superficial gas velocities, leading to a more uniform fluidization. Evaluation of mean and standard deviations has shown the advantage of mixing the two powders as it allowed larger pressure fluctuations and smaller standard deviations. Power spectra, on the other hand, showed that unlike group C, for which fluctuations were small in magnitude and broadband in structure, the mixture showed stronger periodic behaviour as result of the attenuation of the small and rapid fluctuations caused by the flow of gas in the cracks and channels. Advanced methods such as the principal component analysis of the embedded trajectories allowed a quantitative comparison between the fluidization behaviour of the two systems.
Catalytic Activity of Copper Oxide Impregnated HZSM‐5 in Methanol Conversion to Liquid Hydrocarbons
Authors: Zaidi H. A. , Pant K. K.
Published: July 2010

A number of CuO/HZSM‐5 catalysts have been studied in a small scale fixed bed reactor for the conversion of methanol to gasoline range hydrocarbons at 673 K and at one atmospheric pressure. All the catalysts were prepared by wet impregnation technique. The copper oxide loading over HZSM‐5 (Si/Al=45) catalyst was studied in the range of 0 to 9 wt%. XRD, surface area analyzer, metal trace analyzer, SEM techniques and TGA were used to characterize the catalysts. Incorporation of CuO onto HZSM‐5 zeolite significantly increased conversion and liquid hydrocarbon product yields. The major liquid products of the reactions were ethyl benzene, toluene, xylene, isopropyl benzene, ethyl toluene, trimethyl benzene and tetramethyl benzene. The maximum methanol conversion and hydrocarbon product yield was obtained at a copper oxide loading of 7 wt%. Effect of run time on conversion and product distribution was also investigated to compare the performance of these catalysts and coke on the catalyst was determined. Effect of space‐time and temperature on methanol conversion and products yield with 7 wt% CuO/HZSM‐5 has also been investigated and analyzed qualitatively.
Dissolution Rate of BTEX Contaminants in Water
Authors: Njobuenwu Derrick O. , Amadi Stephen A. , Ukpaka Peter C.
Published: July 2010

The BTEX group of contaminants consists of benzene, ethylbenzene, toluene, and three isomers of xylene. The dissolution rate, solubility, slick area and mass transfer coefficient were examined for the BTEX. The release of BTEXs into the environment is influenced by their fate and transport mechanisms. Thus, the fate and transport mechanisms are affected by the contaminant characteristics, which vary with the different BTEX compounds. A comprehensive model has been developed to simulate the molecular dissolution rate of BTEX contaminants in a natural water stream. The developed model modifies the work of Cohen et al. (1980) by considering the physicochemical properties of the BTEX compounds and physical processes relevant to the spreading of contaminants in the sea. The model shows that Benzene with greater solubility in water and dissolution coefficient has the largest dissolution rate while o‐xylene with the biggest density has the lowest dissolution rate because of its low fraction. The benzene dissolution rate is about 2.6, 20.6 times that of Toluene, ethylbenzene, respectively, but with a varying proportion with the xylenes. The model has been validated against the theories of mass transfer rate at the surface at appropriate surface area. The developed model can be found useful in prediction and monitoring the dissolution rate of contaminants in soil and water systems.
Assessment by Microscopy of the Coverage of Sludge Flocs by a Nano‐scale Surface Layer
Authors: Pazin Dorothy , Lott John N. A. , West M. Marcia , Leppard Gary G.
Published: July 2010

Flocs are irregularly shaped suspended particles of complex structure and composition that occur naturally in aquatic systems. In water treatment facilities, the settling of flocs is extremely important. Transmission electron microscopy was used to quantify the formation of a nano‐scale surface layer on flocs from two laboratory bioreactors modelling a biological wastewater treatment facility. By comparing different floc populations, we demonstrated that flocs that settled quickly out of wastewater had a significant amount of this layer, whereas those with little nano‐scale surface layer had poor settling properties. This morphological feature of floc ultrastructure may permit engineering manipulations that promote floc settling.
Molecular Modelling—an Enabling Technology for Chemical Engineers
Authors: Choi Phillip
Published: July 2010

This article briefly describes the basic concepts involved in the two most commonly used molecular modelling methods—molecular dynamics (MD) and Monte Carlo (MC). The methods are particularly useful for studying structures at the length scale of nanometre. Two examples (both are on the study of the miscibility of polyolefin blends) are used to illustrate the techniques. It is demonstrated that it is the nano‐scaled structures formed by the segments of the constituent polyolefins that prevent them from mixing with each other. The examples also show that selection of specific method (MD or MC) depends on the nature of the problem in hand. In general, MC is more efficient than MD in terms of generating equilibrated structure while MD can provide information about the dynamics of a system. This is simply because MD requires the solution of equations of motion (a set of second order differential equations) while MC does not. Nonetheless, both methods need a reasonably accurate force field.
Thermal Blending Time Associated With a Charge of Hot Particles Added to a Fluidized Bed of Uniform Temperature
Authors: Brown W. A. , Pinchuk R. , Pinchuk M. , Diep J. , Weber M. E. , Kiel D.
Published: July 2010

The process of heat transfer between particles in a fluidized bed is important for many industrial fluidized bed processes. The problem associated with studying this phenomenon is the confounding effect of particle mixing on heat transfer. The work described here was undertaken to describe the process in which heat is added to a fluid bed process by adding a hot charge of particles to a colder fluidized bed. The rate of heat transfer in this instance can have a significant impact on performance of the fluid bed process, depending upon its application. Both the method of analysis and the results of the work are applicable to other fluidized bed processes, particularly those associated with the thermal upgrading of heavy oil.

The method of data analysis, based on binomial statistics, allowed useful data to be extracted from a complex system without the need for a large number of experiments. The analysis also allowed for some assessment of the relative importance of mixing and heat transfer, which has not been possible with other approaches. The results of the experiments were further explored using a bubbling bed model that incorporated both heat transfer and solids mixing. This allowed for the formation of a conceptual model, validated by the experimentation, that explains the relative functions of the two transfer processes in the dispersion of heat from a hot charge of particles to the bulk of a fluidized bed.
On Determination of Azeotrope Coordinates from gE for Binary Isothermal and Isobaric Systems
Authors: Missen Ronald W.
Published: July 2010

A relatively simple procedure is described to calculate the coordinates, temperature (Taz), pressure (Paz), and composition (x1az), of an azeotrope (for either an isothermal or isobaric binary system at low pressure and with a single or double homogeneous azeotrope) from an expression for the liquid‐phase excess molar Gibbs function (gE). General results are based on (∂gE/∂x1)az = RTaz ln[p2*(Taz)/p1*(Taz)], and Paz = (γ1p1*)az = (γ2p2*)az, where R is the gas constant, p* is saturation vapour pressure, and γ is liquid‐phase activity coefficient. Specific results are given for the Redlich‐Kister, van Laar, Wilson, and NRTL equations. Numerical examples are provided for both an isothermal and an isobaric system. The procedure provides a means to obtain azeotrope coordinates that are consistent with a gE expression obtained either from experimental data or from a model. It is applicable to polyazeotropy, whereas the criteria given previously are generally not applicable to polyazeotropy.
Optimum Production and Characterization of Thermostable Amylolytic Enzymes from B. stearothermophilus GRE1
Authors: Hossain S. M. Z. , Haki G. D. , Rakshit S. K.
Published: July 2010

Optimum production of extracellular, thermostable amylolytic enzymes (α and β‐amylase) by a newly isolated bacterium, Bacillus stearothermophilus, was investigated in a batch bioreactor. Starch and lactose at 1.0% and 3.0% (w/v) respectively were found to be optimum for maximum enzyme production. Optimization of cultural conditions (pH 7.0 and temperature 45°C) resulted in high bacterial specific growth rate (0.64 h−1), yielding 2.20 gL−1 biomass, 11.43 UmL−1 α‐amylase and 10.04 UmL−1 of β‐amylase. Hydrolysis of native starches from wheat, cassava, corn and potato at 60°C using the crude enzyme showed 60‐80% saccharification with potato starch showing the least and wheat starch showing the greatest hydrolysis. The Km and Vmax values of the crude α‐amylase for starch were 4.78 mg starch/mL and 6.67 mg/mL.min respectively.
Dependence of Holdup on Height in a Pulsed Plate Column Based on Binary Liquid‐Liquid Equilibrium Data
Authors: Montazer‐Rahmati M. M. , Safdari S. J. , Akhgari H.
Published: July 2010

Holdup has been measured at various frequencies, amplitudes, continuous and dispersed phase flow rates for binary systems in a pulsed plate column capable of providing samples at various heights. The binary systems have been so selected as to cover a wide spectrum of interfacial tensions. Dispersed phase holdup was found to increase with height in a logarithmic fashion at conditions away from the flooding point and to become almost invariant with height near flooding conditions. The interfacial tension of the binary system has a large effect on the dispersed phase holdup. In systems having low interfacial tension, a small increase in any of the parameters can increase the holdup significantly and lead to flooding. In systems having high interfacial tension, on the other hand, variations in system parameters do not affect system performance significantly.
Dynamic Modelling and Prediction of Cytotoxicity on Microelectronic cell Sensor Array
Authors: Huang Biao , Xing James Z.
Published: July 2010

A real‐time cell electronic sensing (RT‐CES) system has been used for label‐free dynamic measurements of cell responses to toxicant. Cells are grown onto the surfaces of the microelectronic sensors. Changes in cell number expressed as cell index (CI) have been recorded on‐line as time series. The CI data are used for dynamic modelling or parameter estimation for cell cytotoxicity process. We consider two dynamic modelling approaches, namely data‐based system identification and first principle modelling. It is shown that data‐based system identification can provide a quick solution for the cytotoxicity dynamic models and is effective for short‐term predictions. It, however, can be poor for long‐term predictions, particularly if there is no output correction, i.e., when the model is used for simulation. In view of this, the first principle modelling approach by considering fundamental physical principles such as toxicant transport is explored. For long‐term prediction or simulation, the prediction performance for some of cytotoxicity process is dramatically improved using the models obtained from the latter approach. This happens only if the underlying mechanism is truly understood. Through several cytotoxicity modelling and validation studies, it is shown that the black box modelling and first principle modelling both should be considered in challenging modelling problems such as the cytotoxicity. Pros and cons of the two modelling approaches are discussed.
Near Wall Studies of Pulp Suspension Flow Using LDA
Authors: Pettersson A. Johan , Wikström Tomas , Rasmuson Anders
Published: July 2010

A detailed study of the flow behaviour in the near wall region of pulp suspensions up to 4.7% have been performed using Laser Doppler Anemometry (LDA) in pipe flow. Axial mean velocity profiles show a distinct plug flow and an increase of the plug region as the flow rate decreases and fibre concentration increases.

An attempt is made to relate the LDA data‐rate to fibre concentration, which indicates a dilution region at 1‐2 mm from the wall that is larger than the annulus region. The dilution region increases with increasing flow rate, decreasing concentration and when using longer pulp fibres.
A New Group Contribution Method based on Equation of State Parameters to Evaluate the Critical Properties of Simple and Complex Molecules
Authors: Valderrama José O. , Alvarez Víctor H.
Published: July 2010

A new group contribution method to evaluate the critical properties (temperature, pressure and volume) is presented and applied to estimate the critical properties of biomolecules. Similar to other group contribution methods, the one proposed here divides the molecule into conveniently defined groups and evaluates the properties as the sum of the different contributions according to a specified model equation for each of the properties. The proposed method consists of a one‐step calculation that uses simple model equations and does not require additional data besides the knowledge of the structure of the molecule, except for isomers. For these substances the normal boiling temperature, the molecular mass and the number of atoms in the molecule are used to distinguish among isomers. The method is applicable to high molecular weight compounds, as most biomolecules and large molecules present in natural products.
Kinetics of Liquid‐Phase Hydrogenation of Iso‐valeraldehyde to Iso‐amyl Alcohol Over A Ru/Al2O3 Catalyst
Authors: Tike Manoj A. , Mahajani Vijaykumar V.
Published: July 2010

The liquid‐phase catalytic hydrogenation of iso‐valeraldehyde to iso‐amyl alcohol was studied in a slurry reactor. The kinetics of liquid‐phase hydrogenation of iso‐valeraldehyde over a 5% Ru/Al2O3 catalyst was studied in the range of temperature 373‐393 K and H2 pressure 0.68‐2.72 MPa using 2‐propanol as the solvent. The selectivity to iso‐amyl alcohol was 100%. The kinetic data were analyzed using a simple power law model. A single site Langmuir‐Hinshelwood type model suggesting dissociative adsorption of hydrogen and surface reaction as the rate‐controlling step provided the best fit of the experimental data. The catalyst could be reused thrice without any loss in activity.
Influence of Non‐Condensable Gases on the Dynamic Behaviour of an Auto‐Refrigerated CSTR Polymerization Reactor
Authors: de Toledo Eduardo Coselli Vasco , Martini Rogerio Favinha , Maciel Maria Regina Wolf , Filho Rubens Maciel
Published: July 2010

A polymerization reactor connected to a semi‐flooded horizontal condenser is presented. A model of the process was developed, taking into account the influence of non‐condensable gases in the system. The results obtained show that the model developed was able to reproduce the major dynamic characteristics, even with the presence of non‐condensable gases. It is shown that the non‐condensable gases have great influence on the reactor state, which never reaches a steady‐state; these gases accumulate in the system, increasing the pressure and temperature, and reducing the area of contact and the mass of liquid, therefore needing to be purged regularly, otherwise the system will collapse.
Influence of Polymer Type and Structure on Polymer Modified Asphalt Concrete Mix
Authors: Hussein Ibnelwaleed A. , Wahhab Hamad I. Al‐Abdul , Iqbal Mohammad H.
Published: July 2010

Two low‐density polyethylene (LDPE) resins and two ethyl vinyl acetate (EVA) polymers were used to modify asphalt binder, and then mixed with asphalt concrete according to Marshall Method of mix design (ASTM D 1559). Effect of weight average molecular weight (Mw) of LDPE and vinyl acetate (VA) content of EVA was studied by performing Marshall Stability, moisture susceptibility (AASHTO T 283‐89), resilient modulus (MR) and permanent deformation (rutting) tests. EVA with low VA content showed lower stability loss in Marshall Stability test and improved resistance in moisture susceptibility test in comparison to hot mix asphalt concrete mix (HMA) and other polymer modified asphalt concrete mixes (PMAMs). Higher MR and better rutting resistance were observed for PMAMs than that of HMA. This elastic behaviour of modified asphalt correlates very well with the MR and rutting resistance properties of PMAM.
Reaction Engineering Studies on the Biodegradation of Anthracene on Bioremediation of Diesel Contaminated Soil Using Acinetobacter sp. (ATCC No. 14293)
Authors: Roy Ruma , Bhattacharya Pinaki , Chowdhury Ranjana
Published: July 2010

In the present investigation bio‐degradation of anthracene, a polyaromatic hydrocarbon, from its simulated mixture in methanol, has been studied using a monoculture strain, (Acinetobacter sp. (ATCC No. 14293)), within the concentration range 500‐800 mg/dm3. In a separate attempt bioremediation of diesel contaminated soil to reduce total aromatic content using the same bacterial strain has been carried out. The main emphasis of this investigation is to understand the complex reaction engineering behaviour involved in both the above bioprocess systems. It is observed that while Monod's classical substrate uninhibited model can be used for simulation purpose for the biodegradation of anthracene, the reaction engineering behaviour of the bioremediation of soil can be expressed by coupling Monod's classical equation with first order cell decay rate. In both the cases the concerned intrinsic kinetic parameters have been evaluated.
Layer Inversion and Bed Contraction in Down‐Flow Binary‐Solid Liquid‐Fluidized Beds
Authors: Escudié R. , Epstein N. , Grace J. R. , Bi H. T.
Published: July 2010

Experiments were carried out on downward‐flow water‐fluidized binary mixture of spheres selected for possible layer inversion. With the two binaries tested (relatively high‐density large particles mixed with lower‐density smaller particles), only one of the five possible steps of the layer inversion progression was clearly identified for the higher liquid velocities, a mixed layer being observed at the top of the column close to the distributor. This layer manifested a bed contraction so large that its bulk density was lower than those of its constituent mono‐components at the same liquid velocity, which determined its location within the column. The voidage of the mixed layer could be predicted with good accuracy (<0.7%) by regression of the Westman packed bed equation with one adjustable parameter.
Measuring Flow Velocity and Uniformity in a Model Batch Digester Using Electrical Resistance Tomography
Authors: Lee Q. F. , Bennington C. P. J.
Published: July 2010

The literature shows that the extent of delignification in batch digesters varies as a function of chip location in the vessel. This non‐uniformity may be exacerbated by a number of factors but is commonly attributed to poor and/or non‐uniform liquor flow through the reactor (which causes poor chemical and heat distribution to the chip mass during the cook). Electrical resistance tomography (ERT) was used to evaluate the uniformity of liquor flow in a laboratory model digester under scaled industrial conditions (a 1:15 geometrically scaled vessel, a vessel to particle diameter ratio of 93:1 to minimize wall effects, and close approximation of liquor superficial velocity and pore Reynolds number). Local interstitial flow velocities were measured using pixel‐pixel cross correlation techniques. It was possible to create uniform zones in the digester, but a stagnation point was observed in the centre of the vessel at the screen level. This point coincides with the location of highest kappa numbers (lowest degree of cooking) reported in industrial tests.
Production of 4‐Hydroxybutyl Acrylate and Its Reaction Kinetics over Amberlyst 15 Catalyst
Authors: Yang Jung‐Il , Cho Soon‐Haeng , Kim Hak‐Joo , Joo Hyunku , Jung Heon , Lee Kwan‐Young
Published: July 2010

Esterification of acrylic acid (AA) with 1,4‐butanediol (BD) was carried out over a solid acid catalyst to produce 4‐hydroxybutyl acrylate (HBA), an environmentally benign coating agent. The Amberlyst 15 catalyst was more active for the reaction than other ion exchanged resin catalysts such as Amberlyst 35 and DOWEX HCR‐S(E). The quasi‐homogeneous model was chosen to express the esterification reaction kinetics over Amberlyst 15. The stirring speed was changed from 300 rpm to 750 rpm and the reaction rate showed no influence of external mass transfer. The reaction temperature was varied from 100°C to 120°C to calculate activation energies of the reactions. The calculated activation energies were 58.3 kJ/mol and 86.7 kJ/mol for HBA and BDA (1,4‐butanediol diacrylate, by‐product) productions, respectively. The catalyst concentration was also changed from 0.0043 g/ml to 0.0171 g/ml to find its effect on the rate constant. The complete kinetic equation of esterification to produce HBA over the Amberlyst 15 catalyst based on the quasi‐homogeneous model was developed.
Hydrogen Yield from Low Temperature Steam Reforming of Ethanol
Authors: Das Nikhil K. , Dalai Ajay K. , Ranganathan R.
Published: July 2010

Low temperature steam reforming of ethanol in the temperature range of 200–360°C was studied to maximize the production of H2. The optimum reaction conditions in presence of a suitable catalyst can produce mainly the desired products H2and CO2. Cu/Al2O3catalysts with six different concentrations ranging from 0 to 10 wt.% Mn, were prepared, characterized and studied for the ethanol‐steam reforming reaction. Maximum ethanol conversion of 60.7% and hydrogen yield of 3.74 (mol H2/ mol ethanol converted) were observed at 360°C for catalyst with 2.5 wt.% Mn loading.
An Improved LES on Dense Particle‐Liquid Turbulent Flows Using Integrated Boltzmann Equations
Authors: Tang Xuelin , Wu Jing
Published: July 2010

An improved large eddy simulation (LES) using a dynamic second‐order subgrid stress (SGS) model has been developed for simulating dense particle‐liquid two‐phase turbulent flows. The governing equations of each phase are obtained from a microscopic point of view, using the kinetic theory of molecular gas. They are derived by multiplying the Boltzmann equation of each phase by property parameters and integrating over the velocity space. An inter‐particle collision term is included in the governing equation of the particle phase. Assuming a Maxwellian distribution of the velocity for particle‐phase, an inter‐particle collision term is derived.
Entrainment Rate of Coarse Particles at Different Temperatures in Gas Fluidized Beds
Authors: Choi Jeong‐Hoo , Kim Sang Done , Grace John R.
Published: July 2010

Based on available experimental data, an empirical relationship is developed for the entrainment rate of coarse particles at the exit of gas‐fluidized beds, including the effects of fine particles in the bed, temperature, gas velocity, particle size and density, and column size. It predicts well the influence of fine particles on the entrainment rate of coarse particles, taking into account the momentum of the fine particles and the effect of superficial gas velocity. It also accounts well for the influence of temperature at different solid densities and gas velocities.
Modèles Hydrodynamiques pour la Séparation des Courants dans un Décanteur Pilote
Authors: Berthiaux Henri , Lavin Antonio Guttierrez , De Las Heras Julio Bueno , Alvarez Marisol Muñiz
Published: July 2010

Malgré son emploi généralisé dans l'industrie, la décantation est une opération qui n'a pas encore révélé toutes ses facettes. En particulier, les aspects hydrodynamiques sont par nature complexes du fait de la dépendance des volumes identifiables aux conditions opératoires, ce qui a une conséquence indéniable sur le comportement de l'équipement en régime transitoire.
Sulphation Characteristics of Paper Sludge Ash
Authors: Roh Seon Ah , Kim Sang Don
Published: July 2010

The effects of SO2 concentration and particle size on sulphation of paper sludge ash were determined in a thermobalance reactor. The activation energy and pre‐exponential factor of sulphation reaction of sludge ash were determined based on the uniform‐reaction model. From the X‐ray diffraction analysis, only CaSO4 formation is observed without any other sulphation compounds. The outer pore of the sludge ash is not blocked by CaSO4 and the sulphation occurs uniformly throughout the ash. The uniform distributions of CaO and other inert minerals in the ash provide uniform sulphation with good penetration of SO2 into pores of the sludge ash without pore blocking during sulphation of CaO.
Soret Diffusion and Non‐Ideal Dufour Conduction in Macroporous Catalysts with Exothermic Chemical Reaction at Large Intrapellet Damköhler Numbers
Authors: Belfiore Laurence A.
Published: July 2010

The adiabatic temperature rise in catalytic pellets is predicted from a modified version of the Prater equation. Onsager reciprocal relations for coupled heat and mass transfer are violated in an analysis of thermal diffusion in macroporous catalysts with exothermic chemical reaction when Dufour conduction (i.e., the diffusion‐thermo effect) is neglected. In this contribution, Dufour conduction is analyzed for both ideal and non‐ideal pseudo‐binary gas mixtures that simulate the production of methanol from carbon monoxide and hydrogen. In the diffusion‐controlled regime at large intrapellet Damköhler numbers where intermolecular collisions provide the dominant resistance to mass transfer within the catalytic pores, temperatures in the catalytic core could be much greater than predictions based on the original Prater equation when the Prater number exceeds 0.30. The molecular flux of thermal energy includes Fourier's law, the interdiffusional flux, and Dufour conduction. Diffusional mass flux includes Fick's law and the Soret effect. All physicochemical properties of the reactive gas mixture exhibit temperature dependence. There is essentially no difference between maximum intrapellet temperature predictions that include or neglect ideal Dufour conduction when external catalytic surface temperatures range from 300‐400 K and thermal diffusion enhances the flux of “smaller” reactants toward the centre of the catalyst. For “large‐molecule reactants” that participate in exothermic reactions, thermal diffusion opposes Fick's law and Dufour conduction opposes Fourier's law. Under these conditions, it is demonstrated that core temperatures are overestimated by neglecting both off‐diagonal coupling mechanisms (i.e., Soret diffusion and Dufour conduction). Prater numbers greater than unity and unrealistically high gas pressures are required to distinguish between maximum intrapellet temperatures for ideal and real gas simulations, where the latter consider two‐body interactions for Lennard‐Jones molecules in the virial equation of state.
Simulations of Bubble Column Reactors Using a Volume of Fluid Approach: Effect of Air Distributor
Authors: Akhtar M. Abid , Tadé Moses , Pareek Vishnu
Published: July 2010

Two‐ and three‐dimensional numerical simulations have been performed on a laboratory scale bubble column reactor using a volume‐of‐fluid approach. The effect of hole‐size and superficial gas velocity on the bubble size distribution and their trajectories has been investigated on a 20 cm diameter and 1 m high cylindrical reactor. All simulations were performed in a transient manner using a FLUENT solver. Surface tension between two phases has been modelled as a body force with a constant value. Turbulence was modelled using the k‐ϵ turbulence approach. A comparison between simulation predictions and the reported experimental studies has shown a good agreement.
A Quasi‐Steady State Shell and Shrinking Core Approach to the Drying of Porous Particles and an Example of Parameter Identification
Authors: Manganaro James L.
Published: July 2010

A quasi‐steady state shell and shrinking core approach which recognizes heat and mass transfer resistances in both the gas and particle phases for drying of a porous particle is proposed. A mean field model (constant properties) using this approach was embedded in a spreadsheet combined with a genetic algorithm for parameter identification to provide an easy means of characterizing the drying process from drying data. In drying, assuming a mean field, four major parameters are typically unknown: two related to the process (heat and mass transfer coefficients) and two which incorporate porous particle properties (shell thermal conductivity and vapour diffusivity). It is shown how these four parameters may be determined from experimental drying data. The model was applied to data for spouted bed drying of rice. For the particular case studied, external heat transfer was found to be the controlling mode, although resistance to moisture diffusion within the particle is important. The approach presented admits of future refinements to improve its scope and utility.
Butyl Acrylate/Vinyl Acetate Emulsion‐Based Pressure‐Sensitive Adhesives: Empirical Modelling of Final Properties
Authors: Jovanovic Renata , Dubé Marc A.
Published: July 2010

The influence of the amounts of acrylic acid, chain transfer agent and anionic stabilizer on polymer microstructural properties and final adhesive performance of BA/VAc emulsion‐based PSAs on stainless‐steel and high‐density polyethylene substrates was investigated using a Box‐Behnken experimental design for 15 runs. The resulting data were empirically modelled. For each final adhesive property (i.e., loop tack, shear and peel strength), different models were found to fit the data. Similar models for loop tack and peel strength were found to be adequate for different PSA thicknesses on the same substrate. AA and SDS had significant effects on loop tack as did the AA‐SDS and CTA‐SDS two‐factor interactions. Quadratic peel strength models were found to adequately describe the data for SS substrate cases with a noticeable absence of any interaction parameters. The shear strength models were similar regardless of the substrate or thickness of the adhesive (e.g. in all models, AA and CTA, as well as their second‐order interactions, were the significant factors).
Modelling Carbon Dioxide Corrosion with Film Crystallization and Erosion
Authors: Kennell Glyn F. , Heppner Kevin L. , Evitts Richard W.
Published: July 2010

This paper presents a model of carbon dioxide corrosion in a steel straight pipe under turbulent flow, which includes protective iron carbonate film formation, film undermining, and film erosion. The flow field was discretized using a finite volume technique, with mass transport of dissolved species accounted for with an infinitely dilute solution model. The experimental results of Nesic and Lee, Corrosion 59, 616–628 (2003) were accurately predicted and transient corrosion trends for several temperatures and carbon dioxide partial pressures were determined. The model calculates thinner but denser films at higher fluid flow rates, which corresponds to the experimental trend obtained by Schmitt and Mueller, NACE International, Paper 44 (1999).
Design and Techno‐Economic Analysis of a Process for Transforming Pig Manure into a Value‐Added Product
Authors: Fugère Mylène , Farand Patrice , Chabot Rock , Stuart Paul
Published: July 2010

This study involves the design and techno‐economic analysis of a process that couples biodrying and conventional drying to increase the economic value of liquid pig manure sludge, by transforming it into a stable organic fertilizer. The process has significant environmental benefits compared to other disposal methods, especially considering recent legislative changes restricting the spreading of liquid pig manure, and at the same time provides a return on investment. It was found that the rate of return for the process was 14%, but could reach 25% if the price of the fertilizer product increases as expected.
Identification of Multivariable Delay Processes in Presence of Nonzero Initial Conditions and Disturbances
Authors: Wang Qing‐Guo , Hang Chang Chieh , Liu Min , Tang Wei
Published: July 2010

In this paper, a robust identification method is proposed for multiple‐input and multiple‐output (MIMO) continuous‐time processes with multiple time delays. Suitable multiple integrations are constructed and regression equations linear in the aggregate parameters are derived with the use of the test responses and their multiple integrals. The multiple time delays are estimated by solving some algebraic equations without iteration and the other process model parameters are then recovered. Its effectiveness is demonstrated through simulation and real‐time testing.