bluuebunny/crossref_metadata_2025 huggingface dataset:
Étude hydrodynamique des lits fluidisés sous vide et sous haute température
Authors: Ruvalcaba J. Ramiro Rodriguez , Caussat Brigitte , Hemati Merhdji , Couderc Jean‐Pierre
Published: March 2009

After having analyzed the few literature results concerning fluidized beds hydrodynamics under reduced pressure, new theoretical elements are proposed which provide an estimation of the beginning and finishing fluidization velocities. Numerous experimental results(Umfapp, Umb, Ump, ϵmf, ϵmb, ϵmp), obtained at 20 and 500°C, are then presented for several sub‐atmospheric pressures. Finally, f& the first time, at leastto our knowledge, by high frequency recording pressure drops through the bed, the influence of pressure decreases on the hydrodynamics is accurately analyzed.
Numerical study of laminar condensation of downward flowing vapour on a single horizontal cylinder or a bank of tubes
Authors: Asbik Mohamed , Daif Abdallah , Panday Prabodh Kumar , Khmou Ahmed
Published: March 2009

The results of numerical calculations for the downward flow of pure vapour condensing on horizontal tubes are presented. An implicit finite difference method is used. The equality of shear stress at the liquid—vapour interface is used as the coupling condition between the two phases. The inertia and convection terms are retained in the analysis. The vapour phase velocity is obtained from potential flow. The method of source density distribution on the body surface is used for the determination of the vapour flow in tube banks. The effect of flooding produced by condensation on upper tubes is taken into account by assuming that the vapour velocity field is not affected by the condensate flow from one tube to another. The results presented show that the vapour boundary layer separation depends on the Froude number. The heat transfer in the intertube space is analyzed and compared with the theoretical and experimental results of other authors. Good agreement is shown.
Laminar flow in certain ducts of symmetric cross section
Authors: Wang C. Y.
Published: March 2009

Viscous flow in certain symmetrical ducts can be solved by a modified Levy's method with internal matching. The method is simple, efficient and accurate. Approximate analytic formulas are also derived for the extreme cases. It is found that cutting convex corners has little effect on the flow rate, but a centered core, however slender, decreases flow dramatically. The graphs for flow rates are useful for the design of ell, cross and nested square ducts and also for the prediction of the permeability of parallel‐structured porous media.
Kinetics of leaching of tunisian phosphate ore particles in dilute phosphoric acid solutions
Authors: Brahim Faouzi Ben , Mgaidi Arbi , Elmaaoui Mohamed
Published: March 2009

Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P2O5). When the temperature rises from 25 to 90°C, for a given particle size, the mass‐transfer coefficients, kL°, vary from 3 × 10−3 to 8 × 10−3 m ·s−1. The corresponding diffusion coefficients, D, lies between 6 × 10−7 and 27 × 10−7 m2·s−1. Activation energy is equal to 14 kJ·mol−1 and values of kL°, at 25°C, are in the range of 0.28 × 10−3 and 4 × 10−3 m·s−1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction.
Chromic acid removal by anion exchange
Authors: Tan Henry K. S.
Published: March 2009

The kinetics of dilute chromic acid removal by anion exchange was studied using a batch system. Rate model formulated for total Cr(VI) removal based on film diffusion control was applied. This rate model was shown to adequately fit the experimental rate data. In addition, column experimental runs were performed by using 20‐50 mesh anion resin with feed solution containing 0.2 g/L CrO3. The bed heights of 15, 25 and 35 cm and flow rates ranging from 1.02 cm/s to 2.38 cm/s were employed in the experiments. Linear driving force rate expression based on film diffusion rate control was incorporated in the model equations for simulation of column performance. The kinetic parameter and equilibrium relation in the rate equation were obtained independently either by separate experiments or from data available in the literature. Satisfactory agreements between experimental and calculated breakthrough curves were obtained.
Catalytic conversion of palm oil to fuels and chemicals
Authors: Leng Tan Yee , Mohamed Abdul Rahman , Bhatia Subhash
Published: March 2009

The conversion of palm oil to hydrocarbons using a shape selective zeolite catalyst is reported in this work. Palm oil was passed over HZSM‐5 catalyst in a fixed bed micro‐reactor and the reactor was operated at atmospheric pressure, a temperature range of 360 to 420°C and weight hourly space velocity (WHSV) of 2 to 4 h−1. The main objective was to study the effect of reaction temperature and oil space velocity on the conversion and selectivity of gasoline range hydrocarbons. The results show that 40 to 70wt% of the palm oil can be converted to aromatics and hydrocarbons in the gasoline, diesel and kerosene range, light gases, coke and water. The maximum gasoline range hydrocarbons yield of 40wt% of total product formed was obtained at 400°C and 2 h−1 space velocity.
A new direct‐synthesis tuning method for pi‐controllers
Authors: Jung Chan Sul , Song Hyung Keun , Hyun Jae Chun
Published: March 2009

A new efficient tuning method for proportional‐integral (PI) controllers is proposed using overdamped closed‐loop dynamics of the system. In line with other direct‐synthesis and IMC methods, this new approach uses the desired closed‐loop response to satisfy usual control and tuning objectives, but unlike the most other tuning methods hitherto‐reported for PID controllers, it does not require that a process model be identified. Yet this new direct‐synthesis (NDS) method is capable of making the controller perform the dual control functions of both good set‐point tracking and disturbance rejection. Furthermore, it turns out that the new tuning method works equally well for difficult cases like large time delay and nonminimum phase processes. Finally, it can be said that this NDS method can be easily implemented and understood by the plant operating personnel because it has been developed emphasizing its on‐site utility.
Bed‐to‐wall heat transfer in a downer reactor
Authors: Kim Yong Jeon , Bang Jin Hwan , Kim Sang Done
Published: March 2009

The effects of superficial gas velocity (0.5 to 4.5 m/s), solid circulating rate (0 to 40 kg/m2·s), suspension density (0 to 19 kg/m3) and particle sizes (83, 103, 163, 236 μm) on the bed‐to‐wall heat transfer coefficient have been determined in a downer reactor (0.1 m I. D. × 3.5 m high). Bed‐to‐wall heat transfer coefficient increases with increasing suspension density. The heat transfer coefficient by gas convection played a significant role, especially at lower solid circulation rates or suspension densities and larger particle sizes. At a given particle suspension density in the downer reactor, the heat transfer coefficient increases with decreasing particle size. A model is proposed to predict the bed‐to‐wall heat transfer coefficient in a downer reactor.
Mass transfer and influence of the local catalyst activity on the conversion in a riser reactor
Authors: Venderbosch Rob H. , Prins Wolter , Van Swaaij Wim P. M.
Published: March 2009

Gas–solids contacting in risers has been studied based on measurements of mass transfer controlled CO oxidation over a Pt/γ‐alumina catalyst, and on experimental results published by Ouyang et al. (1995) for the kinetically controlled ozone decomposition. In the present experiments, the catalyst activity was varied by mixing the active catalyst particles with similar, but inert γ‐alumina particles (in ratios from 150 to 2500 m3inert/m3cat), whereas Ouyang and co‐workers varied the operating temperature ( de 300 à to 500 K). Mass transfer controlled CO oxidation occurs at temperatures above 750 K. A negative square root dependency has been observed for the relationship between the Sherwood number and the solid hold‐up. Increasing the gas velocity always improves the gas–solids contacting. The local catalyst activity appears to be an important parameter. As an important conclusion of the present work, it can be stated that at a high local activity, the conversion rate per unit volume of catalyst decreases significantly due to local depletion of reactant.
Novel technologies of VOC decontamination in fixed, moving and fluidized catalyst‐adsorbent beds
Authors: Dolidovich Alexandre F. , Akhremkova Galina S. , Efremtsev Vyacheslav S.
Published: March 2009

Some findings are reported on theoretical and experimental research studies of mechanical, structural, physical and chemical properties, micro‐and macrokinetic adsorptive, catalytic and regenerative characteristics of heterogeneous alumina catalyst‐adsorbents used for decontamination of individual volatile organic compounds (VOC) and their multicomponent mixtures. Data on fluid dynamics, heat and mass transfer in fixed, gravity‐moving and fluidized beds in novel energy‐saving (i) adsorptive, (ii) adsorptive‐catalytic, (iii) thermocatalytic with a quasistationary fluidized and (iiii) with a fixed catalyst beds and deep intercyclic heat recovery of purification systems are obtained and discussed. Correlations are suggested to calculate a number of investigated parameters, and the schematics and operating principles of these technologies are described.
On the measurements of regime transition in high‐pressure bubble columns
Authors: Lin T.‐J. , Tsuchiya K. , Fan Liang‐Shih
Published: March 2009

Two approaches are adopted in this study to identify the flow transition in a bubble column from the homogeneous regime to the heterogeneous regime at pressures up to 15.2 MPa and temperatures up to 78°C. These approaches, which yield essentially identical results, include those based on the standard deviation of the pressure fluctuation and the drift flux model. The experimental results obtained indicate that the regime transition velocity is delayed when the system pressure and temperature increase. The correlation proposed for the transition velocity by Wilkinson et al. (1992) predicts the present results to a reasonable extent, provided that the experimentally measured values for the physical properties of the fluids are used in the correlation. It is clear, however, that an improved correlation or model is needed for a quantitative account of the transition velocity for high‐pressure bubble column systems with different gas distributing capability.
The onset of liquid entrainment during discharge from two branches on an inclined wall
Authors: Hassan Ibrahim G. , Sims Grant E. , Soliman Hassan M. , Kowalski Janusz E.
Published: March 2009

A theoretical investigation has been conducted for predicting the critical liquid height at the onset of liquid entrainment during dual discharge from a stratified two‐phase region through branches mounted on an inclined flat wall. The centerlines of the two branches are parallel and they fall in a common vertical plane. Two models have been developed; a simplified point‐sink model and a more‐accurate finite‐branch model. Predictions from the two models are shown to be in good agreement for the condition of high flow rates from the branches, while the finite‐branch model is necessary for accurate predictions at low branch flow rates. This behaviour has been confirmed experimentally for the vertical‐wall configuration.
Determination expérimentale et prédiction des temps de circulation et de mélange pour un système d'agitation hélicoïdal
Authors: Delaplace Guillaume , Leuliet Jean‐Claude , Dieulot Jean‐Yves , Brienne Jean‐Paul
Published: March 2009

The homogenization efficiency of an atypicalhelical ribbon impeller was investigated. In a first part, circulation and mixting times for Newtonian fluidshave been determiend byuse of conductivity and thermal methods. A transferfunction model havebeen used to fit response curves obtained after tracer injections. The proposed model only depends on twoparametrs. Variations of these two parametrs have been correlated wtih the rotational impeller speed and the Reynolds numbervalue. This work allowsus to prdict, whatever flow regimes and process conditions (viscosity, rotatiional impeller speed), the mixing process performance.
Corrosion des aciers et superalliages inoxydables en eau tritiée ‐ influence du tritium et des espèces radiolytiques
Authors: Bellanger Gilbert
Published: March 2009

To better understand the phenomena in metl equipment corrosion in tritiated water, a study of the behavior of oxide layers on a cobalt‐based stainless superalloy was made in this highly radioactive medium. The oxide characteristics are modified from the corrosion potential, in passivity and up to teh passivity and transpassivity limits. The corrosion of oxide sublayers, as exfoliation of the oxide, was shown. This would appear to be due to diffusion of tritiated species in the oxide. These species accumulate at the oxide‐alloy interface, thus modifying the number of charge carriers in te oxide.
Hydrodynamics and particle collection in turbulent bed contactor
Authors: Gimenes Marcelino L. , Handley Douglas
Published: March 2009

Perforated spheres with 10% and 25% free area, oblate spheroids and the conventional plain spheres were tested as packing medium in a Turbulent Bed Contactor (TBC). Hydrodynamics and particle collection experiments were carried out in a column having 0.264 m diameter, at 3 static bed heights and several gas and liquid flow rates. Alumina (1.5 to 5.5 μm) was used as test powder for particle collection experiments. The higher efficiency of particle collection, the lower bed expansions and the higher fluidization velocities of perforated spheres, indicates that this packing type is suitable as contacting medium for particle collection in TBCs.
Transient response of granular bed motion in rotary kiln
Authors: Sriram V. , Sai P. S. T.
Published: March 2009

A non linear model proposed by Perron and Bui (1994), which focuses on the dynamics of slow mode to predict the transient response induced by step changes in operating variables in the motion of the granular bed in a rotary kiln, was validated for different experimental conditions. The variables include feed rate of solids, inclination and rotational speed of the kiln, and dam height. The validity of the model for step changes in two or more variables at a time was also verified.
Plasmid stability analysis in a non‐homogeneous bioreactor for a recombinant fed‐batch fermentation
Authors: Patnaik Pratap R.
Published: March 2009

Fed‐batch fermentation for tryptophan synthetase by a recombinant Escherichia coli strain has been analyzed through a model incorporating segregational loss of the plasmid pPLc23trpAl and imperfect macromixing of the broth. These features become significant in large fermentation vessels, where fluid circulation in the bioreactor influences the rates of cell growth and productivity. A simple model consisting of two interacting reactors describes the degree of macromixing, which is characterized by the respective (internal) dilution rates. Controlled imperfect macromixing is superior to other methods in arresting, and even reversing, the normal decline in the concentration of recombinant cells, thereby providing a method to exploit the non‐homogeneity of the broth in large bioreactors. Some physical implications are discussed.
Dispositif simple et performant pour disperser un gaz dans un liquide en vue d'effectuer des réactions chimiques ou biochimiques en présence ou non de particules solides
Authors: Botton Roger
Published: March 2009

The proposed system is a vertical liquid jet issuing from an orifice near the surface of a gas–liquid mixture. The jet sucks gas, then penetrates into a coaxial pipe until it hits a horizontal impact plate and disperses into the gas–liquid mixture. The coaxial tube has holes in its upper part to recycle the mixture. The performace of this gas–liquid contacting device are very good. Experimental relations are given and possible applications are examined. One example of reactor calculation is given.
Removal of acetic acid from water by catalytic distillation. Part 1: Experimental studies
Authors: Xu Zhanping , Afacan Artin , Chuang Karl T.
Published: March 2009

Catalytic distillation experiments were carried out in a 100 mm diameter column for the removal of dilute acetic acid from water. The column was installed with a novel internal composed of alternating a dualflow tray and a catalyst basket. Amberlyst 15 was used as a catalyst to accelerate the esterification of acetic acid with methanol. The effects of various operating parameters on the acid removal were investigated. For the feed which contains 2.5 to 9.9 wt% of acetic acid in water, more than 50 wt% of acetic acid can be recovered as methyl acetate in the 1.5 meter high test column.
Catalytic combustion of methane in a monolith washcoat: Effect of water inhibition on the effectiveness factor
Authors: Hayes Robert E. , Awdry Serpil , Kolaczkowski Stan T.
Published: March 2009

This paper reports the results of a numerical investigation of the diffusion and reaction of methane in the washcoat of a catalytic monolith reactor. The kinetic rate expression used is an empirical equation determined experimentally for a palladium oxide catalyst. The effect of water inhibition on the reaction rate is included in the model. A multi‐species diffusion and reaction model is used to simulate the process. The model is solved in a 2‐D space using a finite element method. It is observed that the inhibiting effect of water tends to lower the observed reaction rate and that a higher surface water concentration results in an increase in the observed effectiveness factor. The effectiveness factor depends on three dimensionless parameters. Strong diffusion limitation can lead to high water concentrations at the interior of the catalytic washcoat.
Liquid holdup measurement techniques in laboratory high pressure trickle Bed Reactors
Authors: Al‐Dahhan Muthanna , Highfill Wes
Published: March 2009

Three different techniques, which are tracer, drainage and weighing methods, are used to measure liquid holdup in a laboratory trickle‐bed reactor operated under high pressure. The holdup measurements are compared to determine the applicability of these methods at high pressure operation. It was found that tracer and drainage techniques give comparable values for the total liquid holdup. Although several investigators recommended the weighing method over the others based on their experiments performed at atmospheric conditions, it was found that the weighing method failed to measure liquid holdup properly at high pressure operation.
Model studies on the mechanism of endotoxin adsorption on flat‐sheet microfiltration membrane adsorbers
Authors: Anspach F. Birger , Petsch Dagmar , Deckwer Wolf‐Dieter
Published: March 2009

The adsorption of endotoxin from E.coli O 111:B4 and bovine serum albumin on membrane adsorbers with the ligands polymyxin B, L‐histidine, deoxycholate, poly(L‐lysine), poly(ethyleneimine) and diethylaminoethyl was studied under equilibrium and dynamic conditions. Apparent association constants varied between 30 and 30 000 mL/mg for endotoxin, whereas with BSA only approximately 1 mL/mg was found on average. With all ligands a reduction of the removal efficiency was experienced in the presence of BSA, which was used as model protein. Detailed analysis of the influence of BSA on the association constants as well as the equilibrium and dynamic capacities of endotoxin adsorption demonstrated that endotoxin and BSA molecules recognize distinct binding centres on the membrane adsorbers. Competition for binding sites plays a less important role than assumed so far. It is concluded that interactions of endotoxin with protein molecules in solutions are limiting endotoxin clearance from protein solutions. With net‐positively charged proteins, electrostatic interactions yield protein‐endotoxin complexes. Net‐negatively charged proteins attract endotoxin by the mediation of calcium ions that are derived from endotoxin micelles and vesicles. In the latter case, endotoxin clearance can be significantly improved by the addition of EDTA.
Extractive distillation of 2‐methoxy‐2‐methylpropane + ethanol using 1‐butanol as entrainer: Equilibria and simulation
Authors: Arce Alberto , Rodil Eva , Soto Ana
Published: March 2009

Isobaric (101.32 kPa) liquid‐vapour equilibrium data for the system 1‐butanol + ethanol + 2‐methoxy‐2‐methylpropane (MTBE) were determined and fitted with Wilson, NRTL and UNIQUAC equations, and their prediction by various group contribution methods (ASOG and modified and unmodified UNIFAC methods) was examined. The NRTL equation was used to calculate, by simulation, the influence of plate number and entrainer/feed flow ratio on the quantity and composition of the distillate afforded by extractive distillation of azeotropic MTBE + ethanol using 1‐butanol as the entrainer. The quantity of distillate and its MTBE content both increased with plate number, and the quantity of distillate also increased with entrainer/feed flow rate ratio.
Hypochlorite production on Ru‐Sn binary oxide electrode and its application in treatment of dye wastewater
Authors: Yang Chien‐Hsin
Published: March 2009

Ruthenium‐tin binary oxides [(Ru+Sn)O2] were coated on titanium substrates by thermal decomposition. The surface morphologies and elemental analyses of these electrodes were examined by means of scanning electron microscopy. The electrochemical behaviours were characterized by cyclic voltammetry and linear‐scan voltammetry (LSV) methods. The effects of electrolysis condition for the current efficiency (CE) of hypochlorite production on binary (Ru+Sn)O2 electrodes and the treatment of a high salt‐containing dye wastewater using this hypochlorite were also investigated. The highest CE for hypochlorite production exists on an RS3 (40 to 80 mol% Sn in coating solution) electrode. The major factors influencing CE for hypochlorite production are the electrolyte flow rate, current density, and chloride (Cl‐) concentration. Major factors affecting energy yield are current density, Cl‐ concentration, and electrode distance. For low current density (300 mA.cm−2), high Cl‐ concentration (1 mol.L−1), and 0.45 cm electrode separation, a high specific energy is obtained. The RS3 electrode exhibits the best removal of organics and chromophor groups in the dye wastewater. On this electrode, better removal of organics and chromophor groups is obtained at 300 mA.cm−2. The colour of black‐red dye wastewater becomes light yellow when a charge of 792 A·min was passed, while the chemical oxygen demand (COD) of this wastewater is decreased from 10500 mg.L−1 to 1250 mg.L−1.
Modeling the influence of mineral rocks, active in different hot gas conditioning systems and technologies, on the production of light α‐olefins
Authors: Taralas Georgios
Published: March 2009

A mechanistic reaction model of the pyrolysis of vaporized n‐heptane in the presence of steam (P ≈︁ 18&–32 kPa) is developed based on overall first‐order decomposition kinetics, which satisfactorily describes the experimental data. The mechanistic model predicted that calcined, naturally occurring and readily available mineral rocks, Swedish quarried calcium oxide (quicklime) and Norwegian (Norsk Hydro) magnesium oxide (dolomitic magnesium oxide) applied as the catalytic materials increase the conversion of the vaporized feedstock (P = 2.9–4.7 kPa) without changing the distribution of light α‐olefins (i.e., C2H4, C3+, C4H8), compared to pyrolysis in an empty reactor viz. thermal steam‐cracking. The simulation calls attention to the fact that the endothermic pyrolysis reaction of the alkane n‐heptane is proceeding not only in the homogeneous gas‐phase but also on the mineral particles (catalytic cracking) with the same mechanism.
Effects of oxygen supply condition and specific biofilm interfacial area on phenol removal rate in a three‐phase fluidized bed bioreactor
Authors: Hirata Akira , Meutia Ami Aminah , Osawa Makoto , Arai Manabu , Tsuneda Satoshi
Published: March 2009

The effects of oxygen supply conditions and specific biofilm interfacial area on the phenol removal rate in a three‐phase fluidized bed bioreactor were evaluated. The experimental data were well‐explained by the semi‐theoretical equation based on the assumption that the reaction rate follows first‐order reaction kinetics with respect to oxygen and zero‐order one with respect to phenol. Two cases, biological reaction as rate‐controlling step and oxygen absorption as rate‐controlling step, were both explicable by this semi‐theoretical equation. The maximum volumetric phenol removal rate was 27.4 kg·m−3·d−1.
Mechanism of selenium sorption by activated carbon
Authors: Jadhav Raja A. , Agnihotri Rajeev , Gupta Himanshu , Fan Liang‐Shih
Published: March 2009

Selenium, along with mercury and halides, represents one of the most volatile trace metallic emissions from coal‐fired combustors and utility boilers. This study investigates the potential of activated carbon in capturing gas phase selenium species in the low temperature range (125°C to 250°C) and elucidates the mechanism of interaction between selenium species and activated carbon. Selenium dioxide is chosen as the representative selenium species and experimental investigations are carried out in a differential bed reactor to illustrate the mechanism of SeO2 and carbon Interaction, Activated carbons with different structural properties are studied as adsorbents for selenium dioxide capture at low temperature. The capture mechanism is found to involve both physical and chemical adsorption in the low temperature range. At 125°C, about 1.5 wt% of selenium is captured at equillbrium. Carbon surface analyses and XPS studies confirm the presence of both elemental and oxide forms of selenium on the surface suggesting partial reduction of selenium dioxide to elemental selenium at carbon surface.
Modelling and analysis of membrane‐attached biofilms
Authors: Nicolella Cristiano , Pavasant Prasert , Livingston Andrew G.
Published: March 2009

The theory of diffusion and reaction has been applied to describe mass transfer and reaction phenomena in membrane‐attached biofilms (MABs) growing in extractive membrane bioreactors (EMBs), and to establish the rate‐limiting mechanisms in these systems. The model formulated accounts for substrate counter‐diffusion and two‐limiting‐substrate reaction within the biofilm. Model simulations are compared to experimental data obtained in a lab‐scale EMB and a simple case study is considered to show how MABs affect performance of EMBs. It is found that the organic substrate flux across the membrane is strongly affected by MABs, which constitute an additional resistance to mass transfer and in most cases reduce the flux across the membrane. As a result of the investigation, it is concluded that the decrease of flux in the presence of MABs, observed experimentally and predicted theoretically, is dominated by the resistance to organic substrate transfer caused by the biofilm.
Mixing behaviour of solids in multiple spouted beds
Authors: Saidutta M. B. , Murthy D. V. R.
Published: March 2009

Stimulus response experiments are conducted in four different rectangular columns having two and three spout cells. A pink‐coloured polymer material is used as bed material with ambient air as the spouting fluid. A pulse input of dark blue colour polymer material is used as the stimulus, when the column is operating under steady flow conditions, and the response measured. A mathematical model “plug flow‐mixed flow in series” is used to fit the experimental data and the model parameters are evaluated.
Coal combustion in O2/CO2 mixtures compared with air
Authors: Croiset Eric , Thambimuthu Kelly , Palmer Allan
Published: March 2009

As part of CO2 abatement strategies for climate change, we are investigating coal combusion behaviour in various O2/CO2 mixtures and in air. The goal is to simulate conditions of coal combustion with flue gas recirculation in order to maximize the CO2 concentration in the flue gas prior to its recovery. A western Canadian sub‐bituminous coal and a U.S. eastern bituminous coal were investigated. Thermal input was set at 0.21 MW with a flue gas oxygen concentration of 5 vol%. Experiments were done using various O2/CO2 mixtures and air. The oxygen concentration ranged from 21% to 42%. Up to 95% CO2 concentrations were achieved in the flue gas. This paper describes experimental results in terms of flame temperatures and pollutant emissions (NOx', SO2 and CO).
Beneficial combination of wet oxidation, membrane separation and biodegradation processes for treatment of polymer processing wastewaters
Authors: Mantzavinos Dionissios , Hellenbrand Rolf , Livingston Andrew G. , Metcalfe Ian S.
Published: March 2009

The treatment of a model wastewater containing polyethylene glycol of molecular weight (MW) 10 000 by means of combined chemical oxidative pretreatment, membrane separation and biological post‐treatment was investigated. Wet oxidation was employed as a chemical pretreatment process to convert the original, high MW polymer to lower MW compounds in an attempt to improve the biotreatability of the waste‐water. The partially oxidized effluents formed during wet oxidation at temperatures up to 403 K were separated by nanofiltration where larger molecules were recycled into the wet oxidation reactor, while the permeate leaving the filtration step was treated biologically. At a biological residence time (τB) of 12 h and 3 h, the resulting total organic carbon (TOC) removal in the biological step was as high as 94% and 87%, respectively. Conversely, a continuous aerobic biological process was found inadequate to completely mineralize the original wastewater, since at τb of 96 h only about 60% to 70% TOC removal was achieved, while at τb of 12 h the original wastewater was practically non‐biockgradable.
Experimental studies of liquid flow maldistribution in a random packed column
Authors: Yin Fuhe , Wang Zhongcheng , Afacan Artin , Nandakumar Krishnaswamy , Chuang Karl T.
Published: March 2009

Liquid flow distribution has been a major concern when scaling up random packed columns. This study concerns the measurements of liquid flow distribution in a large scale column packed with 25.4 mm stainless steel Pall rings. The liquid flow distribution was studied with packed bed height from 0.9 to 3.5 m, liquid flow rate from 2.91 to 6.66 kg/m2·s, and gas flow rate from 0 to 3.0 kg/m2·s. In addition, three systems, water/air, aqueous detergent solution/air and Isopar/air, were used to study the effect of liquid physical properties on liquid flow distribution, and two different liquid distributors were employed to test the effect of liquid distributor design. It was found that liquid flow distribution was strongly influenced by liquid distributor design, packed bed height, gas flow rate and liquid viscosity, slightly influenced by liquid flow rate, but not by liquid surface tension.
Methods for measuring the concentrations of SO2, and of gaseous reduced sulphur compounds in the combustion chamber of a circulating fluidized bed boiler
Authors: Fernández Maríaa Joséa , Kassman Håkan , Lyngfelt Anders
Published: March 2009

The present work was aimed at developing and improving methods for measurement of gaseous sulphur compounds in the combustion chamber of a fluidized bed boiler (FBB). The sampling of SO2 was improved by removing NH3 and H2O with a sorbent immediately after the probe. The concentration of reduced sulphur species was determined by means of two conventional SO2 analyzers and an intermediate converter, where the reduced species are oxidized to SO2. Gas phase sulphides were also sampled with a gas quenching probe by means of a basic solution which was subsequently analysed by wet chemistry. The methods were tested during coal combustion in a 12 MW circulating FBB without limestone for two cases of air‐staging.
Ventilation design of industrial premises through CFD modelling
Authors: Rota Renato , Canossa Luca , Nano Giuseppe
Published: March 2009

This work investigates a general ventilation system for reducing the health hazard in industrial premises. Several tests carried out in a laboratory mock‐up have been used to validate the reliability of a general‐purpose computational fluid dynamic model. The same model has been also used to compare the efficiency of different ventilation systems. This clearly indicated the different health hazard related to each configuration, thus allowing one to identify the configuration leading to the lower contamination in the breathing zone.
Determination of the activation energy and intrinsic rate constant of methane gas hydrate decomposition
Authors: Clarke Matthew , Bishnoi P. Raj
Published: March 2009

Experimental data on the kinetics of methane gas hydrate decomposition are reported. The isothermal/isobaric semi‐batch stirred‐tank reactor, used by Kim et al. (1987), was modified to include an on‐line particle size analyzer. The experiments were conducted at temperatures ranging from 274.65 K to 281.15 K and at pressures between 3.1 and 6.1 MPa. The model of Clarke and Bishnoi (1999, 2000) was used to determine the intrinsic rate constant. It was found that the activation energy for methane hydrate decomposition is 81 kJ/mol and the intrinsic rate constant of decomposition is 3.6 × 104 mol/m2 Pa.s.
Flow of solids in an interconnected fluidized beds system investigated using positron emission particle tracking
Authors: Stellema Cornelis S. , Gerritsen Albert W. , Kolar Zvonimir I. , de Goeij Jeroen J. M. , Van Den Bleek Cornelis M.
Published: March 2009

The technique of Positron Emission Particle Tracking (PEPT) is applied to analyse non‐intrusively solids flow in a laboratory scale Interconnected Fluidized Beds system. It is shown that, with a high performance tracking system, it is possible to extract from the data not only the Eulerian ensemble average velocity field, but also to reconstruct density profiles and to calculate mass flows in a solids circulation system. The most interesting flow characteristics inside the Interconnected Fluidized Bed system are highlighted. Although the data analysis is largely Eulerian, a first approach to a Lagrangian analysis has been performed through the computation of velocity autocorrelation functions. Characteristic frequencies of the solids movement could not be identified, but the velocity autocorrelations did provide insight in the dynamics of the solids movement.
Centrifugal degassing of highly viscous newtonian liquids
Authors: Kiljański Tomasz , Dziubiński Marek
Published: March 2009

The movement of gas bubbles in a Newtonian liquid under centrifugal forces was considered. Taking into account wall effects and the increase of bubble diameter during the movement caused by pressure decrease, equations for the bubble movement time in the case of entirely free and immobile bubble surface were derived. Experiments on centrifuging air bubbles showed that in the centrifuge the bubble retained a free surface even at much smaller diameters than under gravity forces. A dimensionless bubble diameter was defined and its critical value above which bubbles behaved as free ones was evaluated.
The fate of methane in a claus plant reaction furnace
Authors: Chin Hilton S. F. , Karan Kunal , Mehrotra Anil K. , Behie Leo A.
Published: March 2009

Experimental kinetic data are reported for key side reactions occurring in the front end [i. e. the reaction furnace (RF) and the waste heat boiler (WHB)] of modified Claus plants used for sulfur recovery from the sour gases evolved in the treatment of natural gas. An extensive experimental study was conducted in a high temperature tubular reactor system for two important homogenous gas‐phase reactions. Firstly, experiments were carried out to study the oxidation of hydrogen sulfide and methane mixtures in the presence of oxygen. Secondly, the reaction between methane and sulfur dioxide was investigated experimentally. These results showed that methane was much less competitive for oxygen than hydrogen sulfide. Hence, in a partially oxidizing environment of a RF, data showed that methane reacted significantly with other major sulfur containing species, as secondary reactions, to form COS and especially CS2. This is highly problematic from an environmental point of view.
A simplified mechanistic analysis of the hydration of magnesia
Authors: Birchal V. S. , Rocha S. D. F. , Mansur M. B. , Ciminelli V. S. T.
Published: March 2009

The kinetics of the hydration of magnesia to produce magnesium hydroxide is described by a kinetic model with no diffusive contribution, including an additional resistance to the reactive flux due to the transient variation of the porosity of the material during reaction. The proposed model has been applied to data from the literature and obtained by hydration of MgO samples with distinct physical characteristics. The model describes well the mechanism of hydration of powder and single crystal MgO in liquid and vapour water with temperatures varying from 35°C to 200°C.
Catalysis assisted plasma decomposition of benzene using dielectric barrier discharge
Authors: Sekiguchi Hidetoshi
Published: March 2009

Atmospheric non‐thermal plasma generated by dielectric barrier discharge was applied to decompose benzene with a sheet type catalyst of platinum supported by alumina. The experimental results indicated that an enhancement of the decomposition by the catalyst was achieved at low concentration of benzene. Ozone produced in the plasma seemed not to contribute to the decomposition. The deactivation of the catalyst was also observed due to decomposition products such as CO and a solid deposit. However a heating treatment could regenerate the catalyst. The results suggested the plasma‐catalyst hybrid reactor was the effective method to solve volatile organic compound (VOCs) problem.
Extension to mixtures of two robust hard‐sphere equations of state satisfying the ordered close‐packed limit
Authors: Ghotbi Cyrus , Vera Juan H.
Published: March 2009

Two new hard‐sphere EOS are proposed and tested using the same attractive potential terms used by the SAFT EOS. Generalized expressions for the pair RDF at contact value, the compressibility factor, and the excess chemical potentials have been derived. Extension to mixtures is tested using three mixing rules for multicomponent hard‐sphere fluids. The proposed EOS combined with the Santos et al. and the Barrio‐Solana mixing rules reproduced the compressibility factors and the excess chemical potentials more accurately than the Boublik‐Mansoori‐Camahan‐Starling‐Leland (BMCSL) EOS. However the pair RDF at contact value had larger deviations than those obtained with the BMCSL EOS. The combination of the proposed equations and the Barrio‐Solana mixing rule gave an accurate reproduction of the compressibility factor for binary hard‐sphere fluids with high diameter ratio even in the low concentration regions of the larger spheres.
Right Cardiac Thrombus in Transit Among Patients with Pulmonary Thromboemboli
Authors: Mollazadeh Reza , Ali Ostovan Mohammad , Abdi Ardekani Ali Reza
Published: March 2009

Background

This study was designed to investigate the prevalence, clinical and laboratory findings, and short‐term prognostic significance of mobile right cardiac thrombus (MRCT) among patients with pulmonary thromboembolism (PTE).

Methods

From January 2004 to November 2006, 12 of 100 patients admitted with a diagnosis of PTE had an MRCT. Diagnosis of in‐transit right‐sided thrombi was made when a wormlike elongated mass was detected. The primary end point was comparison of the mortality rate of MRCT (+) patients with that of MRCT (−) patients for an average of 8 months of follow‐up. The secondary end points were comparison of clinical and laboratory data between these 2 groups.

Results

All MRCT (+) patients but 1 had dyspnea, but just 2 patients had syncope during exertion. The most frequent electrocardiographic finding was T inversion in leads V1–V3 (75%). All 6 of the MRCT (+) patients who had a cardiac arrest in the hospital died in the hospital. In comparison, of the 88 MRCT (−) patients, 12 had a cardiorespiratory arrest, 4 of whom survived (hospital mortality rate of 50% versus 9%, respectively).

Conclusions

It seems that the presence of MRCT has prognostic significance, predicting a higher‐than‐average mortality rate. Copyright © 2009 Wiley Periodicals, Inc.
What explains the extent and content of social and environmental disclosures on corporate websites: a study of social and environmental reporting in Swedish listed corporations
Authors: Tagesson Torbjörn , Blank Veronica , Broberg Pernilla , Collin Sven‐Olof
Published: March 2009

The demand for information and transparency from corporations has increased over the last few years. Today, there are other information dissemination channels besides annual financial statements. One important channel is the Internet. The aim of this study is to explain the extent and content of social disclosure information on corporations' websites. The empirical data in this study is based on annual financial statements and such websites. A multi‐theoretical framework is used in order to explain the extent and content of social disclosures on corporate websites. The findings support the positive correlation of size and profitability with the content of social disclosure information on these websites. In general, State‐owned corporations disclose more social information on their websites than privately owned corporations do. There are significant differences between different industries. This is true regarding not only the extent of social disclosures, but also their content. Copyright © 2009 John Wiley & Sons, Ltd and ERP Environment.
Prolonged exclusive breastfeeding reduces autoimmune diabetes incidence and increases regulatory T‐cell frequency in bio‐breeding diabetes‐prone rats
Authors: Brugman S. , Visser J. T. J. , Hillebrands J. L. , Bos N. A. , Rozing J.
Published: March 2009

Background

Previously, we reported that exclusive breastfeeding delayed and partially protected bio‐breeding diabetes‐prone (BBDP) rats from spontaneous autoimmune diabetes development. To investigate whether this protection results from modulation of the (mucosal) immune system, the present study was designed to analyse the effect of nutrition early in life on the immune status of BBDP rats.

Methods

The breastfeeding period of BBDP pups was extended or not, while allowing half of the pups to eat during that period whereas the other half received only breast milk. Cytokine profiles as well as naturally occurring regulatory T‐cell frequencies were measured over time in the mesenteric lymph nodes (MLNs) and spleen.

Results

Prolonged exclusive breastfeeding partially protects against autoimmune diabetes development and resulted in elevated levels of natural regulatory T cells (CD4+ CD25+ FoxP3+) in MLNs and spleen directly after weaning and throughout life. Stimulation of MLN cells from rats that ingested solid food during the nursing period showed massive secretion of interferon gamma (IFN‐γ), interleukin (IL)‐4 and IL‐10, whereas MLN cells from exclusive breastfed rats did not. In contrast, transforming growth factor beta (TGF‐ß) was secreted equally by all groups.

Conclusions

Prolonged exclusive breastfeeding partially protects BBDP rats from autoimmune diabetes development. Interestingly, ingestion of solid food during the weaning period completely abolishes this protective effect. The protective effect of exclusive breastfeeding correlates with higher levels of naturally occurring regulatory T cells throughout life and low cytokine secretion at weaning. Copyright © 2009 John Wiley & Sons, Ltd.
Mitotic patterns in the migrating lateral line cells of zebrafish embryos
Authors: Laguerre Laurent , Ghysen Alain , Dambly‐Chaudière Christine
Published: March 2009

The sense organs of the posterior lateral line system (neuromasts) are formed by a migrating primordium. In zebrafish, the primordium comprises approximately 100 cells at the onset of migration, and has deposited approximately 300 cells by the end of the process. Here, we report localized phases of mitotic activity and of mitotic quiescence within the migrating primordium. Quiescence in the leading region seems associated to the formation of a new prospective neuromast, whereas quiescence in the trailing region follows a wave of mitoses that synchronize trailing cells in G0/G1 phase, anticipating neuromast differentiation. Manipulating the size of the primordium does not lead to changes in the rate of cell proliferation. We also show that two mitoses often take place nearly synchronously in adjacent cells, suggestive of a determinate lineage. We conclude that proliferation in the migrating primordium follows a stereotyped pattern that closely anticipates the normal development of the system. Developmental Dynamics 238:1042–1051, 2009. © 2009 Wiley‐Liss, Inc.
The Synthesis of New HetPHOX Ligands and Their Application to the Intermolecular Asymmetric Heck Reaction
Authors: Fitzpatrick Martin O. , Muller‐Bunz Helge , Guiry Patrick J.
Published: March 2009

The synthesis of six members of the HetPHOX ligand class and the application of palladium complexes of these ligands to the intermolecular asymmetric Heck reaction is described. The tert‐leucinol‐derived ligands proved the most enantioselective, with palladium complexes of these ligands affording ee values of up to 96, 95 and 94 % in the phenylation, cyclohexenylation and naphthylation, respectively, of 2,3‐dihydrofuran. As an aid to the explanation of the observed selectivity a palladium complex of the most enantioselective ligand was prepared and an X‐ray crystal structure obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
On the effect of prior assumptions in Bayesian model averaging with applications to growth regression
Authors: Ley Eduardo , Steel Mark F.J.
Published: March 2009

We consider the problem of variable selection in linear regression models. Bayesian model averaging has become an important tool in empirical settings with large numbers of potential regressors and relatively limited numbers of observations. We examine the effect of a variety of prior assumptions on the inference concerning model size, posterior inclusion probabilities of regressors and on predictive performance. We illustrate these issues in the context of cross‐country growth regressions using three datasets with 41–67 potential drivers of growth and 72–93 observations. Finally, we recommend priors for use in this and related contexts. Copyright © 2009 John Wiley & Sons, Ltd.