bluuebunny/crossref_metadata_2025 huggingface dataset:
Line tension and wettability effects on reduced gravity nucleate boiling heat transfer
Authors: Alexander K. L. , Li Dongqing
Published: March 2009

Line tension has a significant influence on contact angle during boiling at normal gravity, but previous studies conducted at reduced gravity levels have not considered this parameter. Models were developed to study the validity of neglecting line tension and to examine the influence of contact angle on heat transfer in reduced gravity. It was shown that, although line tension may have an effect at normal gravity, line tension effects are insignificant in reduced gravity. A more non‐wetting liquid on a solid surface has significantly increased heat transfer from the surface to a bubble due to a larger departure radius.
Observer based nonlinear quadratic dynamic matrix control for state space and input/output models
Authors: Gattu Gangadhar , Zafiriou Evanghelos
Published: March 2009

An observer based nonlinear Quadratic Dynamic Matrix Control (QDMC) algorithm is developed for use with nonlinear input‐output (I/O) and state space models. It generalizes and extends previously published nonlinear QDMC algorithms. The extension to I/O models is particularly important due to the increased use of neural networks and other types of nonlinear black box models in the chemical industry. Disturbance rejection and offset free tracking is addressed in a general setting utilizing concepts from filtering theory. Various kinds of disturbance models can be incorporated in the formulation. Even though nonlinear models are utilized for model prediction, the on‐line optimization is formulated as a single Quadratic Program, thus preserving the computational advantages of nonlinear QDMC as compared to Model Predictive Control algorithms based on nonlinear programming techniques. The examples illustrate parameter tuning for open‐loop unstable and stable processes and point out both benefits and shortcomings of the algorithm.
The solubility of ethane in triethylene glycol monomethyl ether
Authors: Henni Amr , Mather Alan E.
Published: March 2009

The solubility of ethane in triethylene glycol monomethyl ether (TEGMME) has been measured at 40, 70 and 100°C at pressures up to 9.2 MPa. The solubility data obtained are compared with those of ethane in other physical solvents. The results were correlated with the Peng‐Robinson (1976) equation of state and the interaction parameters were obtained. Henry's constants were also determined.
Detection and analysis of transition from annular to intermittent flow in vertical tubes
Authors: Das Ramkrishna , Pattanayak S.
Published: March 2009

In vertical co‐current gas‐liquid flow, the transition from annular to intermittent flow occurs when gas core becomes interrupted by liquid bridges due to the instability of the interfacial capillary waves. An analytical model is formulated to explain the liquid bridging in terms of the growth of finite amplitude interfacial capillary waves. Experimental results show that the longest wave length, which is associated with the transition, is about eight times the wave length of waves moving with the velocity of the liquid film.
The effects of polystyrene beads and nylon fibres on the permeability of compressed wood fibre pads
Authors: Chan A. K. T. , Pelton R. H. , Zhu S. , Baird M. H. I.
Published: March 2009

The influence of polystyrene beads (80 μm) and nylon fibres on the water permeability of bleached kraft wood pulp fibre pads was measured and the results were regressed to the Kozeny‐Carman equation. SEM micrographs of pad cross sections showed that the beads, which were uniformly distributed, had little effect on pad structure whereas the long rigid nylon fibres made the pads more difficult to compress.

The pad specific surface areas and swollen volumes were linear functions of the content of beads or nylon fibres. This suggests that the fibre pad permeability characteristics could be adequately modeled from the linear superposition of geometric properties of the pad constituents.
Etude théorique du refroidissement et de la protection d'une paroi plane inclinée par un film liquide ruisselant en présence d'un écoulement gazeux
Authors: Daïf A. , Agunaoun A. , Grisenti M. , Ilidrissi A.
Published: March 2009

The main purpose of this research is the interest in gas–liquid interfacial heat and mass transfer. The investigation is of a much broader interest because it relates to the basic problem of the interaction of a gas stream and a thin liquid film, a situation that is frequently encountered in engineering. A numerical method is presented which allows to treat the film running on a plane or cylindrical plate with an exact localisation of the gas–liquid interface. The application of this model in the case of an inclined plate shows the effectiveness by a liquid film of protecting an insulated plate from injurious effects of the hot gases. When an important hot flux is imposed to the plate, the temperature elevation can be controlled. Comparisons with numerical results of other authors are satisfying.
Batch drying kinetics of corn in a novel rotating jet spouted bed
Authors: Jumah R. Y. , Mujumdar A. S. , Raghavan G. S. V.
Published: March 2009

The batch drying kinetics of corn as a test material were investigated experimentally in a novel rotating jet spouted bed (RJSB) using both continuous and intermittent (on/off) spouting and heating schemes. The parameters investigated include inlet air temperature, bed height, superficial air velocity, nozzle diameter, distributor rotational speed and intermittency of spouting and heat input. The results indicate that the drying kinetics are comparable with conventional spouted and fluidized beds for slow drying materials and that intermittent drying can save up to 40% of the thermal energy as well as air consumption with better quality product.
Effect of temperature on recombinant protein production using the Bm5/Bm5.NPV expression system
Authors: Andersen J. N. , Sriram P. G. , Kalogerakis N. , Behie L. A.
Published: March 2009

A series of experiments have been conducted using a recombinant baculovirus/insect cell expression system (Bm5/Bm5.NPV.CAT) to establish the optimum temperature for both cell growth and virus infection. Bm5 cell growth was found to be limited at temperatures below 22°C and ceased completely at temperatures above 34°C. In the range between 24 and 28°C, final cell densities always reached 96% of the highest achievable viable cell density. The shortest population doubling time was obtained at 28°C. Overall, a consistent increase in metabolism with increasing temperatures was observed. During the infection/viral replication phase, an increase in the temperature from 25 to 31°C resulted in a faster decrease in viable cell density and an earlier production of chloramphenicol acetyltransferase (CAT). Furthermore, protein yield at temperatures above 28°C was significantly reduced. Overall, the best temperature for the infection phase for the Bm5/Bm5.NPV expression system was found to be 25°C when the cells are cultured in serum free media.
Side‐outlet spouted bed with draft tube: Effect of varying the position of the outlet
Authors: Brereton C. M. H. , Epstein N. , Grace J. R.
Published: March 2009

The vector form of the Ergun equation was used to numerically predict gas phase streamlines, residence time distributions, chemical conversions and pressure drops in the annulus of a side‐outlet spouted bed with an internal draft tube. By varying the position of the side‐outlet, it was demonstrated that there exists an optimum location for this outlet at which conversion is a maximum and which shows a greatly improved gas phase residence time distribution in the annulus compared with a conventional spouted bed unit.
Wave phenomena in the packed‐bed reactor: Their relation to the differential‐flow instability
Authors: Yakhnin V. Z. , Rovinsky A. B. , Menzinger M.
Published: March 2009

The steady state of a non‐isothermal packed‐bed reactor (PBR) is convectively unstable in the sense that upstream perturbations are amplified in the course of their downstream propagation before they are washed out by the flow. The differential‐flow instability (DIFI) that underlies this dynamics arises from the different rates of transport of heat and matter in the PBR and from the autocatalytic nature of the reaction heat. In the PBR with recycle, the DIFI has an absolute character and it results in self‐sustained, periodic wave activity. The DIFI‐concept provides a theoretical framework for interpreting and analysing several types of wave phenomena in PBRs.
Coalescence model of particles in coaxial impinging streams
Authors: Berman Yuli , Tamir Abraham
Published: March 2009

Coalescence is mainly affected by particle‐to‐particle collisions. A new model based on an equation expressing the condition for interparticle collision rate as well as the equation of motion of a single particle, has been developed for coaxial impinging streams. The model assumes that coalescence takes place only between small and large particles. In addition to the drag force usually influencing the behavior in impinging streams, the force acting on a large particle due to its collisions with small particles, has also been accounted for in the equation of motion. The effect of the change of the mass of the large particles on the acceleration due to coalescence with small particles, has also been included in the model. The model enables one to predict the composition of the product after coalescence from the composition of the feed and the operating conditions of the coalescentor.
Étude du refroidissement avec solidification d'un fluide pseudoplastique thermodépendant
Authors: Tafkir S. , Nouar C. , Lebouché M. , Devienne R.
Published: March 2009

On étudie numériquement et expérimentalement le transfert thermique dans le cas de fluides pseudoplastiques très consistants s'écoulant à l'intérieur d'une canalisation cylindrique horizontale, l'extérieur de la canalisation étant soumise à un échange convectif considéré comme constant. Le cas envisagé étant celui du refroidissement, il doit ětre tenu compte de l'apparition éventuelle d'un dépǒt de glace. De plus, les variations des propriétés rhéologiques avec la température ont été prises en compte.
Characterization of reverse osmosis and nanofiltration membranes by an automated system
Authors: Kusberg D. J. C. , Lebrun R. E. , Kumar A.
Published: March 2009

Nanofiltration membranes have been characterized by computer controlled permeation experiments to provide certified results. This method records a real‐time history of operating conditions and allows the incorporation of variations in the calculations of derived parameters. The effects of temperature and physical properties of feed on permeation have been evaluated and incorporated in models describing fluid flow trough membranes. As the influence of initial experimental conditions in nanofiltration is very significant, a method based on system mass‐transfer coefficient is proposed in order to verify the accuracy of the results.
Ammonia decomposition in coal gasification atmospheres
Authors: Chambers Allan , Yoshii Yasuo , Inada Tooru , Miyamoto Tomohiko
Published: March 2009

Ammonia present in the product gas from coal gasification may increase NOx emissions from IGCC systems. A fixed bed reactor was used to study the effect of calcined limestone (CaO) on NH3 decomposition and reaction of NH3 and NO. Reactions at temperatures to 900°C in helium and in gas compositions typical of air‐blown gasifiers were studied. Although CaO enhanced ammonia decomposition in helium, reaction in the gasification atmosphere resulted in the loss of this catalytic activity. Increasing the total pressure further reduced the rate of NH3 decomposition. CaO enhanced conversion of NO to NH3 in gasification atmospheres.
Process control utilizing data based multivariate statistical models
Authors: Chen Gang , Mcavoy Thomas J.
Published: March 2009

A process control approach using steady state multivariate statistical models is presented. The goal of this control approach is to improve product quality when the quality measurements are not available on line, or they have long time delays. Principal Component Analysis (PCA) is used to compress information from the process measurements down to a lower dimensional score space, where a control goal is specified using the approach of Piovoso and Kosanovich (1992). A new statistical controller is designed to control the equivalent score space representation of the process. The issue of how to account for the correlation structure of input variables when closing a feedback loop around the PCA model is specifically addressed. A binary distillation column and the Tennessee Eastman process are used for demonstrating the new control approach.
Kinetics of peracetic acid decomposition: Part I: Spontaneous decomposition at typical pulp bleaching conditions
Authors: Yuan Z. , Ni Y. , Van Heiningen A. R. P.
Published: March 2009

Peracetic acid may become one of alternative non‐chlorine bleaching chemicals in the production of fully bleached chemical pulps. In this paper, the stability of peracetic acid was studied in an aqueous solution under conditions most likely encountered in the industrial processes. It was found that three potential reactions, namely i) the spontaneous decomposition, ii) the hydrolysis and iii) the transition metal catalyzed decomposition, are responsible for the consumption of peracetic acid. Furthermore, the kinetics of the spontaneous decomposition was developed. It was found that the reaction follows a second‐order kinetics with the maximum rate at pH 8.2, which is the pKa of peracetic acid. Finally, the developed kinetic equation can describe very well the experimental results obtained in this study as well as the earlier data from Koubek (1964).
The role of poly (ethylene oxide)‐water solution phase behaviour in the retention of fibre fines and clay
Authors: Khoultchaev Khizyr K H. , Kerekes Richard J. , Englezos Peter
Published: March 2009

The retention of fibre fines and clay particles in chemi‐thermo‐mechanical pulp (CTMP) suspensions with poly (ethylene oxide) as a retention aid was investigated. The experiments were conducted at 303 and 343 K. These two temperatures correspond to points below and above the Lower Critical Solution Temperature (LCST) of a 0.005 mass% Poly (ethylene oxide) solution in the presence of 2 mol/L KCl. The KCl was added to lower the LCST to a temperature near papermaking conditions. Poly (ethylene oxide) with molar masses of 1 × 106 and 5 × 106 Da was used.

All the LCST measurements of the poly (ethylene oxide)‐KCl system agree with those in the literature. The retention study revealed that considerably more fibre fines as well as clay are retained at temperatures above the LCST. In particular, the average fibre fines retention was 5.9 percent at 303 K and 22.1 percent at 343 K when the poly (ethylene oxide) with the molar mass of 1 × 106 Da was used. Clay retention was also measured and found to be 5.0 and 15.9% at 303 and 343 K, respectively. Higher retention values were obtained when the polymer with a molar mass of 5 × 106 Da was used. At 303 K the fibre fines retention was 55.0%, whereas at 343 K it was 82.2%. The corresponding clay retentions were 31.7 and 71.9%.
Vapour permeation applied for the separation of water from organic compounds and gases using asymmetric polyetherimide/polyvinylpyrrolidone capillary tubes
Authors: Cranford R. J. , Roy C. , Matsuura T.
Published: March 2009

Asymmetric integrally skinned capillary tubes were produced from the polymers PEI (polyetherimide) and PVP (polyvinylpyrrolidone) for vapour permeation modules which were applied for the separation of water from organic compounds and gases. Water treatment and recovery of desirable organic compounds was achieved. The capillary tubes had intrinsic permeability coefficients of 7.5 × 10−7 mol/m2·s·Pa for water and 1.6 × 10−9 mol/m2·s·Pa for 1‐propanol for a 1:1 mass ratio vapour feed mixture under pyrolysis conditions. The vapour was fed at the interior of the capillary tubes with total pressure of 30 kPa; the permeate total pressure was 14 kPa, and the temperature was 86°C. Modules, with surface areas up to 1.0 m2, were constructed and tested with feed flow rates as high as 4 kg/h with a process development unit. Tests were performed with the vapours from wood chips and contaminated soils subjected to vacuum pyrolysis.
Viscosimetric studies on 2‐methoxyethanol + 1,2‐dimethoxyethane binary mixtures from −10 to 80°c
Authors: Corradini Fulvio , Franchini Giancarlo , Marchetti Andrea , Tagliazucchi Mara , Tassi Lorenzo
Published: March 2009

The kinematic viscosities (v) were measured for nine binary solvent mixtures of 2‐methoxyethanol (ME) + 1,2‐dimethoxyethane (DME) at nineteen temperatures ranging from −10 to +80°C. The experimental data have been used to test some empirical equations of the type v = v(T), v = v(X1) and v = v(T, X1). The viscosities of all the mixtures increase from the values of pure DME to that of ME as the mole fraction of ME increases, and always yield a negative excess property (vE) at all the investigated temperatures. Furthermore, thermodynamic parameters of viscous flow have been evaluated on the basis of the Eyring theory. The excess free energy of activation of viscous flow (ΔGE) vs X2 plot suggests the presence of a stable hetero‐adduct, having ME : DME = 1 : 1 stoichiometric ratio.
Reactive extraction of 6‐aminopenicillanic acid with aliquat‐336: Equilibrium and kinetics
Authors: Bora M. M. , Ghosh A. C. , Dutta N. N. , Mathur R. K.
Published: March 2009

The reactive extraction of 6‐aminopenicillanic acid (6‐APA) from aqueous buffer solution has been studied using a liquid anion exchanger, tricaprylylmethyl ammonium chloride (Aliquat‐336) in n‐butyl acetate as the solvent. The extraction equilibrium constant and partition coefficient increase with increase in pH up to a limiting value of pH, beyond which extraction decreases due to coextraction of OH− and buffer anions and hydrolytic decomposition of 6‐APA. The experimental data could be predicted from an equilibrium model which takes into account the ideal behaviour of the two liquid phases. The coextraction of the buffer anion under low pH conditions was found to be negligible. The extraction rate measured in a stirred cell of constant interfacial area appears to be dependent on the interfacial mass transfer of the reactive species as well as on the interfacial reaction through its dependence on the concentration of 6‐APA in the aqueous and organic phases, respectively.
Gassed power draw of mixed impeller systems
Authors: Myers Kevin J. , Russell Molly I. , Bakker André
Published: March 2009

A technique is proposed to predict the gassed power draw of mixed impeller systems as a weighted average of the gassed power draws of the individual impellers. The success of this method requires determining the gassed power draws of the individual impellers in the proper gassed environment. In the case of the upper impellers, this environment is provided by a rubber membrane sparger that distributes the gas evenly over the vessel cross section. Extensive comparisons of experimental gassed power draws of mixed impeller systems with model predictions verify the accuracy of the proposed technique.
Angular porosity distributions in fixed packed beds of low diameter aspect ratio
Authors: Mueller Gary E.
Published: March 2009

The angular porosity distribution for fixed packed beds of monosized spheres in cylindrical containers with low diameter aspect ratios (1 ≤ D/d ≤ 2) is determined from the spheres' center coordinates. By dividing the packed bed into a large number of identical wedge‐shaped segments, the angular porosity distribution is established from the local angular porosity and the angular positions within the cylindrical container. A correlation which accurately predicts the local angular porosity is determined from the angular porosity distributions. The correlation is a function of D/d and the angular position in the cylindrical container.
The determination of possibility of multiple steady states for complex catalytic reactions in an isothermal CSTR
Authors: Li Hsing‐Ya
Published: March 2009

A class of complex reaction networks with deficiency from two to six, involving isothermal catalytic reactions in a continuous flow stirred tank reactor (CSTR), is determined to have the capacity to admit multiple positive steady states by implementation of the combination of the Deficiency One Algorithm and the Subnetwork Corollary. A set of rate constants and two corresponding positive steady states, one stable and the other one unstable, are constructed for four examples.
Mathematical modelling of formation heat treatment process
Authors: Jamaluddin A. K. M. , Bowen C. T. , Hasan M.
Published: March 2009

A novel matrix stimulation concept, formation heat treatment (FHT), which involves the application of intense heat around the near‐wellbore region for the treatment of water blockage and clay related formation damage in water sensitive formations previously was developed and presented in the literature. The FHT process involves the application of intense heat around the wellbore using a downhole heater. The heat is conveyed to the near‐wellbore region using an inert gas flowing through a downhole heater.

To understand the heat transfer and fluid‐flow characteristics of the FHT process, a transient two‐dimensional mathematical model has been developed and is presented in this paper. The model is based on coupling the momentum and energy‐balance equations for the wellbore gas with the surrounding porous formation. The presence of the heater across the net pay (sandface) is taken into account in the energy equation as a localized volumetric heat source. A control‐volume based finite‐difference scheme is used to solve the model equations on a staggered grid. Parametric studies indicate that by injecting a suitable quantity of gas through the tube and annulus, and by adjusting the power input to the downhole heater, the temperature near the wellbore can be favourably controlled.
Study of the molar mass of grafted polystyrene onto cellulose by the probability indices optimization
Authors: Statiukha O. , Bataille P. , Statiukha G.
Published: March 2009

Graft polymerization of styrene onto cellulose was investigated using ceric ions redox systems as initiator. The effects of reactant concentrations and of processing variables on the molar mass of grafted styrene on the cellulose were studied. A statistical model with the D‐optimal design was used to describe the system. The optimum polystyrene molar mass obtained by simulation was compared to experimental data. The optimal reaction conditions for such a reaction were determined.
Wall effects on terminal velocity of small drops in newtonian and non‐newtonian fluids
Authors: Chhabra R. P. , Bangun J.
Published: March 2009

This work investigated the extent of the wall effects on the free falling velocity of fluid spheres in quiescent Newtonian and pseudoplastic non‐Newtonian media. The terminal velocity has been measured as a function of the physical properties of the both dispersed and continuous phases, and of falling tube diameter. It is shown that inthecreeDing flow region (Re « 1) and for the conditions when the viscosity of the dispersed phase is much smaller khan khat of khe continuous phase, the extent of wall effect is determined only by the ratio of the sizes of the settling fluid sphere and of the vessel. The same analytical relation correlates well the data for both Newtonian and non Newtonian continuous media in the range d/D < 0.45.
Ejector performance in a co‐current gas‐liquid downflow bubble column
Authors: Kundu Gautam , Mukherjee Dibyendu , Mitra Arun K.
Published: March 2009

Performance of an ejector system in a two‐phase downflow bubble column has been evaluated with respect to the energy dissipation during coaxial flow of liquid and gas in a parallel throat and divergent diffiser and during gas—liquid mixing in the column. Experiments were carried out in a 51.6 mm i.d. column with five different nozzles. Three systems, namely air—water, air‐kerosene and air—paraffin were used. Correlations have been developed for predicting the ejector loss coefficient as well as mixing loss coefficient as a function of different physical and dynamic variables of the system.
Influence of phase orientation on dynamic interfacial tension measured by drop volume tensiometry
Authors: Wu Dongmin , Hornof Vladimir
Published: March 2009

In processes involving two liquid phases, such as enhanced oil recovery, one phase is often present in a drop form (drop phase) while the other is in continuous form (bulk phase). In the present paper, the effect of such phase orientation on dynamic interfacial tension between the two phases formed by the partially miscible system composed of butanol‐1 and water has been investigated by using the method of drop volume tensiometry. With butanol‐rich (butanol‐1 saturated by water) as the drop phase and water‐rich (water saturated by butanol‐1) as the bulk phase, the interfacial tension is 1.70 ± 0.02 mN/m. The interfacial tension for water‐rich as the drop phase is almost identical at 1.72 ± 0.03 mN/m. Addition of a surfactant, sodium dodecyl sulfate, to the system has been studied. When the surfactant is added to the drop phase (either butanol‐rich or water‐rich), the magnitude of the decrease in interfacial tension is smaller than when surfactant is added to the bulk phase (water‐rich or butanol‐rich) or to both phases. Under otherwise identical conditions, when the water‐rich acts as the drop phase, the apparent interfacial tension is higher than that when the butanol‐rich acts as the drop phase.
A model of ceramic membrane fouling during heavy oil ultrafiltration
Authors: Duong Anna , Smith Kevin J.
Published: March 2009

Fouling of asymmetric, single tube ceramic membranes during ultrafiltration of Cold Lake heavy oil, is described by a pore restriction fouling model that predicts reduced permeate flux but increased asphaltene rejection with increased time‐on‐stream. Application of the model to experimental data showed that a 2nd‐order rate of asphaltene adsorption/deposition within the membrane pores, described the data better than a 1st‐order model. The asphaltene molecular radius, estimated as a parameter of the model, was in the range 3.8 ‐ 14.2 nm, depending on the membrane pore diameter. These values are in good agreement with previously published estimates of asphaltene particle size, determined using different experimental techniques.
Oxidation of low concentrations of hydrogen sulphide: Process optimization and kinetic studies
Authors: Yang Aimin , Tollefson Eric L. , Dalai Ajay K.
Published: March 2009

Low concentrations (e.g. < 3) of H2 S in natural gas can be selectively oxidized over an “granular Hydrodarco” activated carbon catalyst to elemental sulphur, water and a small fraction of by‐product sulphur dioxide, SO2. To optimize the H2 S catalytic oxidation process, the process was conducted in the temperature range 125—200 °C, at pressures 230—3200 kPa, with the O/H2 S ratio being varied from 1.05 to 1.20 and using different types of sour and acid gases as feed. The optimum temperature was determined to be approximately 175 °C for high H2 S conversion and low SO2 production with an O/H2 S ratio 1.05 times the stoichiometric ratio. The life of the activated carbon catalyst has been extended by removing heavy hydrocarbons from the feed gas. The process has been performed at elevated pressures to increase H2 S conversion, to maintain it for a longer period and to minimize SO2 production. The process is not impeded by water vapour up to 10 mol% in the feed gas containing low concentrations of CO2 (< 1.0). A decrease in H2 S conversion and an increase in SO2 production were obtained with an increase in water vapour in the feed gas containing a high percentage of CO2. The process works well with “sour natural gas” containing approximately 1% H2 S and with “acid gas” containing both H2 S and CO2. It gives somewhat higher H2 S conversion and low SO2 production with feed gas containing low concentrations of CO2. A kinetics study to determine the rate‐controlling step for the H2 S catalytic oxidation reaction over “granular Hydrodarco” activated carbon has been conducted. It was concluded that either adsorption of O2 or H2 S from the bulk phase onto the catalyst surface is the rate‐controlling step of the H2 S catalytic oxidation reaction.
Modeling infinite dilution activity coefficients of organic‐aqueous systems using a modified regular solution equation and cubic equations‐of‐state
Authors: Bader Mansovr S. H. , Gasem Khalid A. M.
Published: March 2009

Expressions derived from the regular solution equation and the generalized cubic equations‐of‐state (EOS) were employed to model the infinite dilute activity coefficient (γ∞) of organic‐aqueous systems. A database of 119 organic species in aqueous systems, divided into six classes, was gathered for models evaluations. The use of the molar density, the first order molecular connectivity, and the dipole moment appear to be adequate correlating variables for describing the structural dependence of the residual part in the modified regular solution equation (MRS). The Soave‐Redlich‐Kwong (SRK) and Peng‐Robinson (PR) were specified and employed in the generalized cubic EOS form. The excess activity coefficient concept was used in the SRK and PR EOS models to account for the deficiency of EOS in dealing with highly non‐ideal or polar systems. The abilities of two existing correlation models along with two modified versions of the UNIFAC model were also assessed. The proposed models provide creditable equations for correlating γ∞ of organic‐aqueous systems.
Rising velocity of a swarm of spherical bubbles in power law fluids at high reynolds numbers
Authors: Chhabra R. P.
Published: March 2009

In this work, a theoretical scheme for estimating the rise velocity of a swarm of spherical bubbles through quiescent power law liquids at high Reynolds number is developed. The inter‐bubble interactions have been accounted for by the use of a cell model. The effect of the power law index and the volume fraction of the gas on the rise velocity is elucidated. Depending upon the degree of shearthinning behaviour and the gas fraction, the swarm may rise slower or faster than a single bubble. This behaviour has been explained qualitatively in terms of two competing mechanisms.
Transient heat transfer in a fixed bed of slab‐shaped and spherical particles with intraparticle conduction
Authors: Sheikholeslami Roya , Watktnson A. Paul
Published: March 2009

The mathematical equations for heat transfer between a flowing fluid and both slab‐shaped and spherical particles with intraparticle conduction in a fixed bed, are numerically solved using the method of lines. The solution for spherical particles was used to confirm previous results for zero and non‐zero Biot numbers. Conditions are identified under which heat transfer to beds of slabs should not be approximated by available solutions for spheres.
Gas‐solid mass transfer in a rotating drum
Authors: Javhari Ritika , Gray Murray R. , Masliyah Jacob H.
Published: March 2009

Gas‐solid volumetric mass transfer coefficients (kSA) were measured in a rotary drum by evaporation of n‐decane into dry air from the surface of porous solids. The effect of drum rotational speed, N (0.09 to 2.0 min−1), solids volume fraction, η (0.043 to 0.25) and the presence of baffles on kSA were investigated. In the presence of baffles, kSA was independent of ηand higher than in the case of a rolling bed where no baffles were present. For the rolling bed case, kSA increased with increasing η. Mass transfer in the rolling bed was modeled based on the particle motion.
Ethanol‐water pulping: Cooking variables optimization
Authors: Gilarrahz M. A. , Oliet M. , Rodriguez F. , Tijero J.
Published: March 2009

The ethanol‐based pulping of Eucalyptus globulus by the ALCELL® process was studied to determine the optimum cooking conditions. In the first set of experiments the influence of chip size, chip impregnation, liquor‐to‐wood ratio and cooking additives was studied. Once the more convenient values for these variables were established according to kappa number, yield and viscosity, a surface response method was used to determine the influence of cooking temperature, cooking time and ethanol concentration on autocatalyzed pulping process. The developed models indicate that a high screened pulp yield (56%) and acceptable kappa number (23) and viscosity (1030 mL/g) can be obtained when cooking conditions are around 185°C, 110 min and 50% of ethanol.
Non‐isothermal micromixing in turbulent liquids: Theory and experiment
Authors: Baldyga Jerzy , Bourne John R. , Walker Benedikt
Published: March 2009

Partial segregation of reagents occurs when reaction rates exceed mixing rates and frequently causes product distributions to be mixing‐dependent. A simultaneous temperature segregation, whereby the temperature in a reaction zone differs from that in its surroundings, has rarely been considered when mixing reagents in the liquid phase. The Prandtl number is usually sufficiently small that engulfment, not thermal conduction, determines the local temperature. The engulfment model of micromixing can then be extended by a heat balance to specify this temperature. To evaluate this model, a new pair of fast competitive reactions (neutralisation and acetal hydrolysis) has been characterised thermochemically and kinetically. A Mettler RC1 calorimeter was operated under isothermal and adiabatic conditions with various stirrer speeds and HCl was slowly added to a mixture of NaOH and 2,2‐dimethoxypropane. Measured hydrolysis yields compared quite well with the extended engulfment model, although temperature segregation was of minor importance. It was also unimportant in other reaction systems (simultaneous neutralisation and ester hydrolysis; diazo coupling) employed earlier to study micromixing. Suggestions for further work are made.
The use of mixing‐sensitive chemical reactions to study mixing in dispersed fibre systems: Adsorption of reactants and product dyes on the dispersed phase
Authors: Mmbaga Joseph P. , Bennington Chad P. J.
Published: March 2009

Mixing‐sensitive chemical reactions conducted under controlled conditions can be used to qualitatively and quantitatively assess mixing in aqueous systems. These reactions are typically competitive reactions where the distribution of products is used to quantify mixing. This technique is valuable for studying both mixing and local energy dissipation in dispersed systems where the opacity of the suspension prevents the use of other techniques. However, correct interpretation of the test results requires that adsorption of reactants and product dyes on the dispersed phase be known. The adsorption of the reactants and product dyes formed in the mixing‐sensitive azo coupling between mixtures of 1‐ and 2‐ naphthol and diazotized sulfanilic acid was measured in aqueous suspensions of nylon, polyethylene, fibreglass and kraft pulp fibres. The polyethylene fibre did not adsorb the reactants or product dyes. The nylon, fibreglass and kraft fibres adsorbed both reactants and product dyes, with adsorption described by Langmuir isotherms. Accounting for the adsorption of dye on the dispersed phase allowed correct interpretation of mixing in the aqueous phase of the dispersions. This technique is evaluated for mixing assessment in suspensions of nylon fibre and fully bleached kraft (FBK) pulp in a medium‐intensity mixer.
Process viscometry of complex fluids and suspensions with helical ribbon agitators
Authors: La Fuente Edmundo Brito‐De , Nava Jose A. , Lopez Luzmaria , Medina Luis , Ascanio Gabriel , Tanguy Philippe A.
Published: March 2009

The viscosity of highly inelastic shear thinning fluids and aqueous suspensions of kaolin clay particles has been investigated using a helical ribbon impeller fitted to a rheometer. Viscosity data for the single phase non‐Newtonian fluids adequately processed with a generalized Reynolds number based on the impeller tip speed are shown to superimpose very well to the results obtained with a cone and plate rheometer. In the case of the two‐phase system, it is shown that the data treatment for single phase system can be extended. The helical ribbon impeller yields more stable viscosity values than with the traditional geometries and no spurious flow phenomena (i.e., sedimentation, slip at the wall, etc.) was observed, making this system a superior device for suspension rheology over cone and plate and Couette flow rheometers.
Characterization of dispersed hydroprocessing catalysts prepared in reversed micelles
Authors: Hall Andrew G. , Duangchan Apinya , Smith Kevin J.
Published: March 2009

Fe, Co and Ni particles were prepared in water/polyoxyethylene‐4‐laurylether/n‐hexane and water/polyoxyethylene‐4‐laurylether/decahydronaphthalene microemulsions by reduction of metal nitrates dissolved in the water pools of the reversed micelles. The particles were mostly monodispersed with average diameters in the range 8 to 23 nm, as determined by dynamic light scattering (DLS). However, significantly smaller size estimates were obtained using transmission electron microscopy (TEM). The average DLS particle diameters increased with increased average diameter of the reversed micelles, and the diameter of the reversed micelles increased with an increase in the microemulsion water: surfactant ratio and metal ion concentration. The diameter of the reversed micelles was also dependent upon the metal dissolved in the water pool, increasing in the order Ni < Co < Fe. These trends are explained in terms of changes that occur to the microemulsion hydrophilic‐lipophilic balance. Preparation of nickel and cobalt sulfides by sulfidation of the metal salt with H2S at low temperature, yielded much larger diameter particles (average diameter 75 nm). Measurement of the activity of the sulfided catalysts showed that the Co catalyst was more active than the Ni catalyst for the hydrocracking of diphenylmethane, and Co was more effective than Fe in reducing coke yield during Cold Lake residue hydroprocessing.
Kinetics and extraction of phenol in phase‐transfer catalyzed reaction
Authors: Wu Ho‐Shing , Liu Chien‐Bang
Published: March 2009

Under two‐phase conditions, the feasibility of extracting/removing phenol from aqueous alkaline medium via reaction with allyl bromide dissolved in dichloromethane was investigated using phase‐transfer catalysts in a stirred cell. The effects of the concentrations of base, reactant and catalyst, and temperature were also evaluated to obtain the optimum reaction conditions. According to these results, the extractive efficiency of phenolic substances varied strongly with increasing base concentration. The specific extraction rate, diffusivity, mass transfer coefficient and distribution coefficient of an intermediate product were determined to explain the reaction mechanism by the proposed theoretical model. During reaction, the concentration of the intermediate product in the organic phase was also measured, and a simulation method was used to examine the mass transfer behavior of the intermediate product in the liquid‐liquid system.
Evaluation des dépôts d'aérosols par thermo et diffusiophorèse lors de l'ecoulement dans une conduite cylindrique — applications aux essais tuba diffusiophorèse
Authors: Zoulalian André , Albiol Thierry
Published: March 2009

Dans l'hypothèse d'un accident sévère sur un réacteur nucléaire à eau pressurisée, les aérosols émis par le coeur du réacteur seront entraînés par un écoulement gazeux constitué de vapeur d'eau et d'incondensables. Dans le circuit primaire et plus précisément au niveau du générateur de vapeur, ces aérosols se déposeront sur la paroi du faisceau tubulaire par thermo et diffusiophorèse. L'analyse des bilans de matière et d'énergie montre que dans le cas d'un écoulement stationnaire dans un tube cylindrique à température de paroi constante, l'efficacité des dépôts d'aérosols par thermo et diffusiophorèse peut être estimée à partir de la connaissance de deux grandeurs thermohydrauliques que sont l'efficacité de condensation et la température moyenne du fluide à la sortie du tube. Les expressions théoriques trouvées permettent de rendre compte de manière satisfaisante des résultats obtenus lors du programme expérimental “Tuba diffusiophorèse” de l'Institut de Protection et de Sûreté Nucléaire. Enfin, l'analyse simultanée des deux types de dépôts est plus représentative qu'une analyse associant de manière indépendante les deux types de dépôt.
Sodium aluminosilicate crystal formation in alkaline solutions relevant to closed cycle kraft pulp mills
Authors: Park Hyeon , Englezos Peter
Published: March 2009

Metal ions, such as those of Al, Si, and Ca known as non‐process elements (NPEs), are a major concern in the development of technology for achieving closed cycle operation in Kraft pulp mills. For example, the build‐up of NPEs such as Al and Si ions causes sodium aluminosilicate complex formation in the recovery cycle of Kraft pulp mills. These complexes precipitate on process equipment and are very hard to remove. The purpose of this study is to supply basic data on the precipitation conditions for such complexes. These data can be used to develop process models for design and optimization of closed mills. The precipitation conditions of sodium aluminosilicate complexes in synthetic green and white liquors were determined. In the experiments, the effects of varying the A1/Si ratio and concentrations of OH‐, Na2S, CO32‐, and SO42‐ were studied. The structure of the precipitates was identified by X‐ray diffraction, thermo‐gravimetry and chemical analysis. The precipitates were found to have the structure of hydroxysodalite and/or sodalite.
Control of the product distribution in the hydrogenation of vegetable oils over nickel on silica catalysts
Authors: González‐Marcos M. Pilar , Gutiérrez‐Ortiz José I. , De Elguea Cristina González‐Ortiz , Alvarez Jon I. , González‐Velasco Juan R.
Published: March 2009

Several nickel on silica catalysts, prepared by impregnation or precipitation/deposition, and a commercial catalyst were tested for activity and selectivity in the sunflower seed oil hydrogenation. An average turn‐over frequency of 2.57 s−1 was found for the catalysts, assuming inaccessibility of nickel in pores smaller than 2 nm and a constant nickel surface concentration poisoned by the reaction mixture. After studying the mass‐transfer steps, the effect of temperature (373‐453 K) and pressure (101‐608 kPa) on reaction rates in the kinetic regime was analyzed, and the corresponding apparent activation energies and reaction orders were obtained. Conclusions on the effect of temperature and pressure on the selectivity to the preferential hydrogenation of polyunsaturates (So) and to the formation of trans‐isomers ((Strans)0) in the kinetic regime were derived from the results. Finally, a similar analysis was carried out when diffusion limitations were known to be present.
Unsteady mass transfer between a slender bubble and a viscous liquid in a simple extensional flow
Authors: Favelukis Moshe
Published: March 2009

Unsteady mass transfer between a slender bubble and a viscous Newtonian liquid in a simple extensional and creeping flow has been studied. The exact analytical solution, at large Peclet numbers, has been obtained using similarity transformations and by the method of characteristics. It was determined that when a dimensionless time (the strength of the flow multiplied by the time) is greater than 2, then steady state is, in practice, obtained.
Propriétés rédox de fullerènes fonctionnalisés
Authors: Boudon Corinne , Gisselbrecht Jean‐Paul , Gross Maurice , Thiel Walter , Cardullo Francesca , Seiler Paul , Isaacs Lyle , Nierengarten Jean‐François , Haldimann Richard F. , Diederich François , Mordasini‐Denti Tiziana
Published: March 2009

Les propriétés physico‐chimiques du C60 laissent présager son utilisation comme brique élémentaire dans la synthèse de nouveaux matériaux. La fonctionnalisation de fullerènes modifiant ces propriétés, nous avons, pour toute une série de fullerènes hautement fonctionnalisés, étudié les modifications de leurs propriétés physico‐chimiques et plus particulièrement électrochimiques. Cette mise au point rassemble les résultats obtenus lors de nos études électrochimiques de fullerènes C60 mono et poly‐fonctionnalisés de manière covalente. L'objectif est d'analyser les corrélations susceptibles d'exister entre les propriétés rédox des fullerènes et le degré, le motif et la nature de la fonctionnalisation du C60. Pour effectuer cette étude, une série de fullerènes fonctionnalisés sur les positions [6,6] ont été synthétisés. Cette série unique de mono‐ et poly‐adduits permet effectivement l'étude des modifications des propriétés physiques et électrochimiques en fonction du degré, du motif et de la nature de la fonctionnalisation. Les résultats obtenus sont comparés aux données de la littérature.
Gas—liquid mixing studies with multiple up‐ and down‐pumping hydrofoil impellers: Power characteristics and mixing time
Authors: Hari‐Prajitno Danawati , Mishra Ved P. , Takenaka Katsuhide , Bujalski Waldemar , Nienow Alvin W. , Mckemmie Jack
Published: March 2009

Axial flow impellers with hydrofoil blades, APV‐B2, i. e., B2‐30 and B2‐45 (30° and 45° angle of attack of blades) have recently been designed, mainly for use in the up‐pumping mode, and some new results are reported here for single, dual and triple impeller configurations in the turbulent flow regime. The results are compared with dual Lightnin' A‐315's pumping downwards as they have traditionally been used and with dual radial flow Rushton turbines. The ungassed power numbers of the APV‐B2's are low, allowing these impellers to be used at large impeller‐to‐tank diameter ratios. The drop in Pg/P is lower with all combinations of APV‐B2 impellers, i. e., for single, dual and triple impellers when compared to other configurations tested. Torque fluctuations are less than those with single or dual down pumping axial hydrofoils. Mixing times measured using a decolourisation technique for dual and triple impeller configurations of APV‐B2 under unaerated and aerated conditions showed that the mixing times are much shorter than those for the dual Rushton turbine and similar to those found for dual down‐pumping A‐315's. Detailed mixing characteristics and flow patterns for the dual and triple APV‐B2's are also discussed.
Catalytic steam pyrolysis of a selected saturated hydrocarbon on calcined mineral particles
Authors: Taralas Georgios
Published: March 2009

At a total pressure of 101.3 kPa, and in the presence of water vapor (P = 32 kPa), the impact of commercially available Norwegian and Swedish quarried mineral rocks on the gaseous product yields and selectivities generated during the catalytic steam pyrolysis of n‐heptane (Pn‐C7H16, = 2.9‐4.7 kPa) in the intermediate temperature range of 973–1073 K and GHSV 1200–4000 h−1 was investigated. The results indicate that the choice of calcined mineral particles as the bed material influences the product distribution of alkenes. In particular, calcined dolomites [CaMg(O)2] suppressed the evolution of unsaturated and aromatic hydrocarbon species; however, the formation of ethylene (C2H4) was correlated. A Langmuir‐Hinshelwood mechanism has also been proposed to describe the rate equation of the vapor‐phase steam pyrolysis of n‐heptane on calcined dolomite at 973 K.
Gas holdup in homogeneous and heterogeneous gas—liquid bubble column reactors
Authors: Sarrafi Amir , Müller‐Steinhagen Hans , Smith John M. , Jamialahmadi Mohammad
Published: March 2009

The velocity‐holdup relationship is the most important design parameter for gas—liquid bubble column reactors, providing the basis for the prediction of heat and mass transfer coefficients and information on hydrodynamic conditions. A summary of the literature on gas holdup in bubble columns is supplemented by new experimental results which extend the data range. A criterion for the gas velocity leading to the transition between homogeneous and heterogeneous regimes for perforated plate gas distributors has been developed. Correlations for gas holdup in both regimes are developed and verified against both new and existing data.