bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrospun nanocomposites from polystyrene loaded with cellulose nanowhiskers
Authors: Rojas Orlando J. , Montero Gerardo A. , Habibi Youssef
Published: March 2009

Composite microfibers from polystyrene and cellulose nanowhiskers were produced by electrospinning. The morphology of the microfibers was examined by using scanning and transmission electron microscopies. Surface porosity, unique ribbon‐shapes, and the presence of twists along the fiber axis were observed in the composite microfibers. Thermomechanical properties of processed nanocomposites were studied by differential scanning calorimetry and dynamical mechanical analyses. The reinforcing effect of cellulose nanowhiskers was confirmed as the glassy modulus of electrospun microfibers increased with nanowhisker load. This effect is explained to be the result of mechanical percolation of cellulose nanowhiskers forming a stiff and continuous network held by hydrogen bonding. It is demonstrated that cellulose nanoparticles can be used effectively to reinforce hydrophobic matrices and to produce unique structural properties, enabling new functionalities and properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Differential Photoluminescent and Electrochemiluminescent Detection of Anions with a Modified Ruthenium(II)–Bipyridyl Complex
Authors: Berni Emanuela , Gosse Isabelle , Badocco Denis , Pastore Paolo , Sojic Neso , Pinet Sandra
Published: March 2009

Different lights, different selectivies: Luminescence of a new guanidinium 3,3′‐functionalized bipyridyl–RuII complex has been studied for sensing of several anions. L‐Glutamate and dihydrogenphosphate are both detected by photoluminescence and electrochemiluminescence. However, the complex displays differential selectivities for these anions depending on the sensing channels (see scheme).

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A new guanidinium 3,3′‐functionalized bipyridylruthenium(II) complex has been prepared for the differential sensing of L‐glutamate and dihydrogenphosphate anions depending on the luminescent detection scheme. The effects of such anions on the photoluminescent (PL) and electrochemiluminescent (ECL) properties of the complex have been investigated and compared. The PL intensity increases up to fourfold in the presence of L‐glutamate. The increase of intensity in the presence of dihydrogenphosphate is weaker and no change in PL intensity is observed in presence of acetate, iodide, or chloride anions. With n‐tripropylamine, ECL emission of the RuII complex is initiated at 1.45 V versus Ag/AgCl/KCl and the ECL intensity increases only in the presence of dihydrogenphosphate. Indeed, L‐glutamate is already oxidized at the relatively high potential required for ECL generation and thus it does not affect the ECL signal. The comparison of the competitive ECL and PL assays in a mixture of anions confirms the differential detection of L‐glutamate and of dihydrogenphosphate. Thus, both sensing channels (i.e., PL and ECL) show different selectivities depending on the nature and on the electroactivity of the target anions. Multianion analysis is demonstrated in competitive assays using complementary detection methods.
Methane‐Propylene homologation and reactivity of surface carbon on modified Ni‐Al2O3 catalysts
Authors: Liu Qingdong , Smith Kevin J.
Published: March 2009

Modified Ni catalysts supported on alumina and reduced in CH4 have been investigated for the synthesis of C4 hydrocarbons from CH4 and C3H6. Addition of K or P to the Ni/Al2O3 catalyst increased C4 selectivity and C3H6 conversion. A maximum selectivity to the desired C4 product of 9 mol % was obtained at 350°C and 101 kPa with a feed gas composition of 90 mol% CH4/10 mol% C3H6, but the catalyst activity declined rapidly with time‐on‐stream. Large amounts of unreactive carbon were deposited on the catalyst surface following reduction in CH4 and reaction in CH4/C3H6. However, the relative amount of a much more reactive species identified from Temperature‐Programmed‐Surface‐Reaction that was formed in the presence of CH4 and C3H6, is shown to correlate with the catalyst C4 yield. Both the C4 yield and the relative amount of this low temperature carbonaceous species increased in the order Ni<Ni/P<Ni/K.
A combined model of mass transfer coefficients for contaminated drop liquid‐liquid systems
Authors: Slater M. J.
Published: March 2009

Mass transfer rates to and from drops in liquid‐liquid extraction equipment are often likely to be reduced by the presence of surface active contaminants. For industrial column design circumstances it is ideally required to account for the extent of contamination in a quantitative manner yet existing design procedures do not allow this to be done for the typical intermediate Reynolds number region of 10 to 100. A method is proposed for correcting continuous phase and drop mass transfer coefficients for the deleterious effects of contamination using only one contamination parameter which needs to be determined experimentally.
On the timing of primary fragmentation during bituminous coal particle devolatilisation in a fluidized bed combustor
Authors: Stubington John F. , Moss Brendan
Published: March 2009

The times at which devolatilising coal particles fragmented were compared with their devolatilisation times in a fluidized bed combustor. Whereas the devolatilisation times were similar, the time to first fragmentation varied markedly from coal to coal. Immediate fragmentation was attributed to thermal shock. Fragmentation during the first 1/3 of the devolatilisation time was attributed to the internal pressure generated from restricted transport of volatiles through the pores in the coal structure. Fragmentation near the end of devolatilisation may occur due to weakening of the coal structure by loss of volatiles. Primary fragmentation did not affect the devolatilisation time, even for coals which fragmented early in their devolatilisation time.
Drag on chains and agglomerates of spheres in viscous newtonian and power law fluids
Authors: Chhabra R. P. , Singh Tushar , Nandrajog S.
Published: March 2009

New experimental data on the free settling velocity of straight chains (up to twenty spheres) and planar clusters of touching spheres in Newionian and power law media are reported. The results embrace the following ranges of conditions: 0.65 ≤ n ≤ 1; Re < ‐ 2.5 and 1.22 < m < 48.87 Pa·sn. The straight chain drag measurements are in line with theoretical predictions for Newtonian fluids. The present results in power law fluids seem to suggest that it is possible to express the drag on a straight chain of spheres in terms of that on a single sphere of equal volume. Limited results with planar clusters are satisfactorily correlated using a volume equivalent sphere diameter.
Hydrodynamics of circulating fluidized bed risers: A review
Authors: Berruti F. , Pugsley T. S. , Godfroy L. , Chaouki J. , Patience G. S.
Published: March 2009

Any vessel in which solids are transported upward by a gas stream and then recycled to the bottom may be classified as a Circulating Fluidized Bed (CFB). We describe possible CFB operating regimes in the context of this broad classification and highlight commercial processes that employ CFB technology and potential applications. Process design and development require a fundamental understanding of gas and solids hydrodynamics — solids hold‐up, mixing and velocity distribution. We discuss techniques used to measure solids mass flux, which is a critical parameter for both design and control. In the last decade, significant research efforts have been devoted to new experimental techniques to measure both gas and solids spatial and temporal distribution. We list these techniques and detail the different modelling approaches that have emerged based on the new data. Characterization of the data is still incomplete and the available models require further refinement to reliably predict the effect of scale, operating conditions and particle characteristics on hydrodynamics.
The characteristics of cluster in a high density circulating fluidized bed
Authors: Wei Fei , Yang Guo‐Qiang , Jin Yong , Yu Zhi‐Qing
Published: March 2009

The cluster images in a high density circulating fluidized bed (HDCFB) measured by a one‐dimensional optical fiber image analysis system are studied. The experimental results show that the characteristics of cluster in the riser vary greatly at different operating conditions. The radial cluster size, the cluster interception time and the probability of cluster appearance increase with bed density and decrease with gas velocity. Based on the analysis of the cluster image at various operating conditions, correlations of the radial cluster size, the cluster interception time and the probability of cluster appearance in a HDCFB are proposed. It is found that they are related to local solids concentration and gas velocity.
Modelling of induced aeration in turbine aerators by use of radial basis function neural networks
Authors: Aldrich C. , Van Deventer J. S. J.
Published: March 2009

Gas induction in agitated vessels with turbine impellers can be modelled accurately by means of radial basis function neural nets. The results obtained with the radial basis neural net were significantly better than those obtained by multivariate regression models or standard back propagation neural nets. Moreover, by using the radial basis function neural net model, it was possible to conduct a sensitivity analysis of the variables affecting aeration. Increased medium density showed a strong adverse effect, while variation of the viscosity can cause an increase or a decrease in the rate of aeration, depending on the prevailing process conditions.
Gas‐liquid mass transfer in two and three‐phase upflows through a vertical tube
Authors: Ishida Kazuhiko , Enda Shigeyuki , Kikuchi Ken‐Ichi , Takahashi Hiroshi
Published: March 2009

Oxygen absorption rates were measured to determine volumetric coefficients of gas‐liquid mass transfer coefficients kLa in gas‐liquid and gas‐liquid‐solid upward flows through a vertical tube. The liquid was deionized water or aqueous glycerol solution, and the solids were glass beads or polystyrene beads. The dependencies of kLa on gas velocity, liquid velocity, temperature, solid material, and solid concentration were examined. The experimental results were correlated with empirical equations. The mechanisms of the solid loading effect are discussed.
An LDA study of the turbulent flow field in a baffled vessel agitated by an axial, down‐pumping hydrofoil impeller
Authors: Jaworski Z. , Nienow A. W. , Dyster K. N.
Published: March 2009

The turbulent flow of water in a cylindrical, baffled vessel with an axial flow hydrofoil impeller, either a Chemineer HE3 (CHE3) or a Prochem Maxflo T (PMT), has been studied using a laser Doppler anemometer. Using ensemble averaging, the mean axial and radial flow and the associated fluctuating components were obtained for the whole of the vessel; plus similar data for the tangential component close to the impeller. Assuming axial symmetry, flow rates were calculated as were flow numbers and circulation flow numbers. Power numbers were also determined. All the data obtained were used to compare the circulation efficiency of the two hydrofoils plus a pitched blade and a Rushton turbine. This comparison showed that the CHE3 required a power input of about 2/3 of that for the PMT and about 1/3 of that for the pitched blade and Rushton turbine to obtain the same axial‐radial circulation in the tankz.
Statistical assessment of gas/liquid mass transfer in slurry‐phase propylene polymerization process
Authors: Li J. , Tekie Z. , Mohammad A. , Morsi B. I.
Published: March 2009

A statistical approach was developed to investigate the effects of pressure, temperature, mixing speed and solid concentration on kLa for gaseous hydrogen, ethylene, and propylene in liquid n‐hexane containing solid polypropylene powder in a 4‐litre agitated reactor. The solubilities of the gases appeared to follow Henry's Law. Statistical correlations to predict kLa were proposed and response surfaces were constructed. kLa values appeared to reach a maximum around 15 mass% and sharply decrease above 30 mass%. The effects of pressure and temperature on kLa were found to depend on the gas‐liquid system and operating conditions used.
Mixing of a lateral gas stream in a two‐dimensional riser of a circulating fluidized bed
Authors: Marzocchella Antonio , Arena Umberto
Published: March 2009

A cold model of a circulating fluidized bed having a two‐dimensional riser, with a 12 × 120 mm section and a 6.4 m height, was equipped with a device to inject a lateral gas stream along the riser. The apparatus was operated under conditions ranging from those characteristic of combustors to those of gas‐conversion processes. Flow structures in the interaction region between the rising gas—solids suspension and the lateral gas stream were studied by means of a motion analysis system. Three main configurations were identified. The ratio between the momentum of the lateral gas stream and that of the rising suspension was found to be the parameter able to discriminate among the three configurations. A satisfactory agreement was found with mixing data obtained using a cylindrical riser.
Experimental study of the fluidic mixing in a cylindrical reactor
Authors: Orfaniotis A. , Fonade C. , Lalane M. , Doubrovine N.
Published: March 2009

An experimental study of fluidic mixing in a cylindrical reactor was conducted in order to determine the effects of jet position and liquid viscosity. The tests were carried out in a tank of 0.09 m3 liquid volume using eight conductimetric probes to measure the mixing time. Relative jet positions leading to an impinging flow structure have been found to be less efficient than shear flow configurations. Mixing time and inhomogeneity correlations extending the previous results of Simon and Fonade (1993) are put forward for mixing by steady or unsteady jets.
Gas and particle flow patterns in cyclones at room and elevated temperatures
Authors: Patterson P. A. , Munz R. J.
Published: March 2009

Experimental results are presented for a study of gas and particle flows in a 102 mm diameter conventional cyclone operated at temperatures between 300 and 2000 K. Inlet gas velocities ranged from 3 to 42 m/s. Particle deposition patterns and the measurements of local pressures were used to determine the flow patterns and velocity profiles within the cyclone. A “Reynolds Number” has been defined based on the mean inlet velocity and the hydraulic diameter of the annulus between the cyclone wall and the gas outlet duct. An empirical equation was derived to correlate the ratio of the wall tangential velocity to the mean inlet velocity with this Reynolds Number.
Relationship between solids formation, residuum conversion, liquid yields and losses during athabasca bitumen processing in the presence of a variety of chemicals
Authors: Sanford Emerson C. , Xu Chun Ming
Published: March 2009

Conditions were chosen for the batch processing of Athabasca bitumen such that approximately 8% of the feed was converted to solids under an atmosphere of nitrogen. When hydrogen or tetralin was used, the amount of solids formed was cut in half. The combination of hydrogen and tetralin decreased the amount of solids formed by one‐half again. These conditions were used to study radical trapping reactions and hydrogen transfer under a variety of conditions using solids formation as a measure of reaction. None of the reagents used decreased solids formation significantly, and many increased the retrograde reaction. Correlations between solids formation (2–25% of feed) and yields and conversions showed that CCR conversion and sulfur conversion were not correlated with solids formation but nitrogen and vanadium conversions were. Most significant was the finding that losses (yields of gases) were constant for the 29 runs, at constant residuum conversion. Gases must be formed as a result of the initial thermally induced carbon‐to‐carbon bond breaking step in order for the yield to be independent of solids formation. Distillate yields decreased as solids formation increased.
A new policy for the estimation of the course of supersaturation in batch crystallization
Authors: Fevotte G. , Klein J. P.
Published: March 2009

A continuing effort is being made in the development of on‐line sensors for the monitoring and control of crystallization processes. Applied on‐line calorimetry provides an estimate of the instantaneous heat release due to crystallization advancement. Two approaches to the implementation of such “soft sensors” are described and difficulties arising in the case of on‐line multipurpose non‐isothermal applications are outlined. Off‐line estimates of concentration and super‐saturation profiles during typical batch evaporative crystallizations are reported. Particular attention is paid to the detection of second, late nucleation bursts occurring in cases of poor crystal growth and rapid temperature decay.
An alternative method for evaluation of intrinsic viscosity
Authors: Kozicki W. , Kuang P. Q.
Published: March 2009

An alternative method for determination of intrinsic viscosities is described which evolves from the application of l'Hǒpital's rule to the expression defining the intrinsic viscosity. The method yields independent evaluations of the intrinsic viscosity and does not involve extrapolation beyond the range of experimental data or rely on a theoretical expression associated with such extrapolations. The application of the method is illustrated and comparisons are included with the results obtained by traditional approaches.
Simulation of airlift pumps for deep water wells
Authors: Nenes A. , Assimacopoulos D. , Markatos N. , Mitsoulis E.
Published: March 2009

A mathematical model for the simulation of water airlift pumps is developed, based on the “interspersed continua” approximation for two‐phase flow systems, together with an algorithm that selects the appropriate friction correlation for specific flow regimes. The model presented can either predict the water or air flow rate for a given airlift system. Predictions obtained by the model were compared with a series of experiments performed by the Greek Institute of Geological and Mineral Exploration and were found to be in good agreement. The present predictions are far superior to those obtained by an existing simple model currently in general use.
A simple experimental test of the lifshitz‐van der waals/acid‐base approach to determine interfacial tensions
Authors: Kwok D. Y. , Neumann A. W.
Published: March 2009

The Lifsthitz‐van der Waals/acid‐base approach is shown to yield liquid–liquid interfacial tensions incompatible with experimental results.
Residence time distribution of the liquid in two‐phase cocurrent downflow in packed beds: Air/newtonian and non‐newtonian liquid systems
Authors: Iliuta I. , Thyrion F. C. , Muntean O.
Published: March 2009

New data on the liquid residence time distribution for two‐phase downflow of air‐Newtonian and non‐Newtonian liquids through packed beds of porous and non‐porous particles are presented. The piston‐dispersion‐exchange model is used to describe the liquid flow. With porous particles the dynamic evolution of the tracer concentration in the particles is described in terms of diffusion phenomena. The axial dispersion is very important in the case of two‐phase downflow of air‐water (trickle flow regime) and air‐CMC systems through fixed beds with porous particles, and is negligible in the case of non‐porous particles. With the porous particles, a key value is the effective diffusion coefficient of the tracer in the pores of the particles.
Degradation of alkanolamine blends by carbon dioxide
Authors: Dawodu Olukayode Fatai , Meisen Axel
Published: March 2009

Aqueous solutions of MDEA, MDEA + DEA and MDEA + MEA containing 4.2 kmol/m3 total amine, were contacted with CO2 at a partial pressure of 2.58 MPa and temperatures ranging from 120 to 180°C, in a stainless steel batch reactor. The reaction products include the known degradation compounds of the amines as well as products formed from secondary interactions in the amine blends. The rate of degradation was first order in the amines and, in magnitude, followed the sequence MDEA < MEA < DEA. Furthermore, the rate constant for MDEA was independent of amine substitution level and blend constituents. From a practical standpoint, MDEA + DEA blends would require frequent DEA make‐up to maintain treating efficiency.
Diffusion of lignin macromolecules within the fibre walls of kraft pulp. Part I: Determination of the diffusion coefficient under alkaline conditions
Authors: Li J. , Phoenix A. , Macleod J. M.
Published: March 2009

The intrinsic rate of diffusion of soluble lignin from fibre walls to bulk liquor has never been determined previously because of experimental difficulties; for example, the diffusion rate determined in a stirred cell is affected by the mechanical action of stirring. In our work, the intrinsic rate of diffusion of lignin macromolecules from the fibre walls of a softwood kraft pulp was determined under alkaline conditions using a displacement cell which eliminated external heat and mass transfer resistances and pulp fibre disturbances. The effects of such experimental conditions as pulp bed height and liquid flow rate were studied. The diffusion rate can be described by a diffusion model for a hollow cylinder with a very wide range of diffusion coefficients. The diffusion rate increased with increasing pH. Our results provide a new understanding of the lignin diffusion process in fibre walls, which is affected by the size of lignin molecules and the pores, and by the electrostatic interactions between intrafibre pore walls and lignin.
Quantitative analysis of combined impingement and through air drying of paper
Authors: Chen G. , Crotogino R. H. , Douglas W. J. M.
Published: March 2009

Models were developed and verified to represent the water removal rate data of the two components of combined impingement and through air drying process. Eight physically meaningful parameters were identified, determined, correlated and analyzed. The increasing rate period is extended by impingement water removal. Constant impingement water removal decreases linearly with through flow ratio at a fixed impingement exhaust air flow. Constant through flow water removal is independent of the impingement air. Critical moisture content relates with through flow ratio parabolically. The maximum through flow water removal rate depends on the slope of the paper temperature increase and the extent of the secondary increasing rate period which increases with paper basis weight and drying air temperature, but decreases with through flow ratio and initial moisture content.
Cold flow velocity measurements in recovery boilers: Part I: Interaction of primary and secondary air flows
Authors: Karidio I. , Uloth V. , Markovic C. , Thorn P.
Published: March 2009

Cold air flow velocities were measured in a commercial recovery boiler during shutdown periods, using hot‐wire anemometers, modified to indicate direction. Five tests were carried out using different primary and secondary air configurations. The conditions tested included arrangements recommended by others to improve gas flow uniformity, as well as unrealistic extremes to be used in the evaluation of computational fluid dynamic models. The measurements demonstrated the inherent unsteadiness of recovery boiler flows and confirmed that balanced air flows through opposed walls result in a central region of high velocity upward flow. Interlacing of the secondary air significantly reduced the peak velocity and flattened the upward velocity profile at the liquor gun level.
Characterization of the surface area of overflow droplets generated by a gas‐lift pump under reduced pressure
Authors: Lee Hi Sun , Harris Ralph
Published: March 2009

Water‐modelling experiments were carried out to characterize the surface area of overflow droplets generated by a gas‐lift pump under reduced pressure as a function of various operating parameters, namely, top pressure, gas flow rate, nozzle submergence, lift ratio and riser diameter. The liquid phase mass transfer coefficient was obtained by applying the penetration theory (Treybal, 1980; Bird et al., 1960) to the overflow generated from the riser. Under reduced pressure, churn‐turbulent flow, consisting of distorted bullet‐shaped bubbles, was predominant in the flow regime. The increase of liquid circulation rate and flight time and the decrease of droplet size increased the refining rate. Because of the large droplet size, the refining rate of molten metals was smaller than that of water.
Minimum spouting velocity of conical spouted beds
Authors: Bi H. T. , Macchi A. , Chaouki J. , Legros R.
Published: March 2009

Existing correlations for predicting minimum spouting velocity in conical spouted beds have been found to give poor agreement with available literature data. A new correlation has been developed based on literature data to give much better prediction of the minimum spouting velocity for both small and pilot‐scale conical‐spouted beds.
The solubility of HFC125, HFC134a, HFC143a and HFC152a in n‐eicosane, n‐hexadecane, n‐tridecane and 2, 6, 10, 14‐tetramethylpentadecane
Authors: Wahlström åsa , Vamling Lennart
Published: March 2009

The solubility of 1, 1, 1, 2,2‐pentafluoroethane (HFC125), 1, 1, 1, 2‐tetrafluoroethane (HFC134a), 1, 1, 1‐trifluoroethane (HFC143a) and 1,1‐difluoroethane (HFC152a) in four well‐known hydrocarbons have been measured at temperatures between 293.15 and 363.15 K and pressures between 0.05 and 2 MPa. Henry's constant, and the activity coefficient for HFCs at infinite dilution, have been derived for measurements below 0.28 MPa. The measurements were made with an isochoric method and their uncertainty is less than 2% for Henry's constant and less than 3% at high pressure. For several mixtures, the experimental data have been correlated with the UNIQUAC method and binary interaction parameters have been derived, resulting in a deviation from the data of less than 4%.
The optimum plate aspect ratio for the best performance in a flat‐plate thermal diffusion column of the frazier scheme
Authors: Yeh Ho‐Ming
Published: March 2009

The effects of plate aspect ratio on the degree of separation, production rate and plate surface area in a flat‐plate thermal diffusion column of the Frazier scheme, have been investigated. Theoretical considerations show that when the thermal diffusion columns of the Frazier scheme are constructed with the best plate aspect ratio, maximum separation, maximum production rate or minimum plate surface area can be obtained. The optimum plate aspect ratio for maximum separation is obtained with given production rate and plate surface area, while that for maximum production rate is determined with the degree of separation and plate surface area fixed, and that for minimum plate surface area is estimated with known degree of separation and production rate. It is interesting that the optimum plate aspect ratio for maximum separation is exactly the same as that for minimum plate surface area. The maximum separation and maximum production rate are achieved without changing any total expenditure, while the design with minimum plate surface area results in minimizing the total expense.
Bubbling from nozzles submerged in water: Transitions between bubbling regimes
Authors: Kyriakides N. K. , Kastrinakis E. G. , Nychas S. G. , Goulas A.
Published: March 2009

The bubble formation and coalescence phenomena above submerged nozzles having diameters between 1 and 7 mm were studied visually in a stagnant water column. Air was supplied at the nozzles under constant flow rate conditions and the field of view extended from the nozzle exit up to 14 cm above it. The air Reynolds number based on the nozzle diameter covered a range between 50 and 40000. The study was focused on a unified description of the bubbling phenomena, beginning from the single bubble formation up to the jet formation, and the transitions between the various bubbling regions. It was concluded that for nozzles, as injector devices and for the air/water system investigated, the Reynolds number is the controlling variable for the bubbling phenomena above the nozzles and for the transition between the various bubbling regions.
Numerical and physical modeling of the permeability of paper to CMC and coating liquids
Authors: Poulin N. , Tanguy P. A. , Aspler J. , Larrondo L.
Published: March 2009

The penetration of CMC solutions and coating liquids into paper sheets was investigated experimentally and modeled using a Lucas‐Washburn equation (Lepoutre, 1978) adequately modified to account for the dynamic contact angle and the coating fluid rheology. A numerical simulation of the fluid penetration based on the finite element resolution of the Navier‐Stokes equations was carried out as well. The numerical predictions and the predictions of the Lucas‐Washburn equation were compared with the experimental data showing the limitations of the models.
Operation of a catalytic reverse flow reactor for the purification of air contaminated with volatile organic compounds
Authors: Van De Beld L. , Westerterp K. R.
Published: March 2009

Catalytic oxidation in a reverse flow reactor is an attractive process for the decontamination of air polluted with volatile organic compounds (VOCs). In this paper several aspects of operating this type of reactor for air purification under strongly varying conditions will be discussed.

For a successfit operation of such reactor a minimum amount of combustibles is required, and a simple theory is developed to predict this minimum value. This minimum amount is strongly influenced by the reaction kinetics, the heat transport in the packed bed and the adiabaticity of the reactor. To cope with a too low temperature level in the reactor for a complete conversion, an electrical heating device should be installed in the centre of the reactor bed to increase locally the temperature rapidly and efficiently. To control the maximum temperature in case of too high concentrations, extra air should be added to the feed.
Corresponding‐states and parachor models for the calculation of interfacial tensions
Authors: Zuo You‐Xiang , Stenby Erling H.
Published: March 2009

A generalized corresponding‐states model based on two reference fluids and a parachor correlation were developed for the prediction of interfacial tensions for non‐polar and weakly polar pure fluids and mixtures. Pure methane and n‐octane were chosen as reference fluids of the corresponding‐states model. The two models were tested on 86 pure substances, more than 30 binary and multicomponent mixtures, 11 naphtha reformate cuts, 6 petroleum cuts and 2 North Sea oil mixtures. The calculated results were found to be in good agreement with experimental data.
Kinetic models for non‐homogeneous complex systems with a time‐dependent rate constant
Authors: Montané Daniel , Overend Ralph P. , Chornet Esteban
Published: March 2009

This paper discusses a phenomenological kinetic model which describes the conversion of complex non‐homogeneous systems. The model embodies the concept of a severity parameter as a descriptor of the extent of reaction of the complex system. Temperature, time and catalyst concentration are simply and conveniently regrouped in the definition of the severity parameter. The link between our model and formal kinetics can be made via a time‐dependent rate constant. Such dependency expresses the concept that in a complex non‐homogeneous system the chemical acts leading to reaction are first order processes constrained either by microstructural effects, diffusional limitations, geometric discontinuities, or in generic terms by fractal considerations. The observable effect is the change in reactivity with extent (or time) of reaction. Our approach permits to model such systems via a set of four key markers characteristic of the overall reaction. The development of the model, the significance of the markers and their application to the hydrolysis of lignocellulosic biomass as a case study are presented and discussed.
Optimisation de l'hydrolyse des protéines du lactosérum en utilisant des détergents commerciaux enzymatiques et non‐enzymatiques
Authors: Argüello M. Ángeles , Elzo Dominique , Riera Francisco A. , Álvarez Ricardo
Published: March 2009

L'objectif principal de ce travail est la caractérisation des effets produits par l'utilisation de détergents commerciaux sur les protéines du lactosérum, dans le but de sélectionner un détergent efficace pour le nettoyage des membranes inorganiques colmatées dans les procédés de fractionnement de ces protéines. On a étudié l'influence des variables temps, pH, température et concentration du détergent sur le degré d'hydrolyse du substrat (protéines du lactosérum). On a déterminé aussi le type et la taille des peptides produits au cours de l'hydrolyse. Les résultats les plus performants on été obtenus avec le détergent P3‐Ultrasil 62.
Bubble size and mass transfer coefficients in dual‐impeller agitated reactors
Authors: Bouaifi Mounir , Roustan Michel
Published: March 2009

The study relates to the mass transfer and the bubble size in a non standard vessel equipped with various dual‐impeller combinations. The effects of the rotational speed, gas flow rate, impeller type and diameter are investigated. The volumetric mass transfer coefficient kLa and the bubble size dbs were studied. The liquid side mass transfer coefficient kL and the volumetric interfacial area a were estimated separately. A comparison has been made with some existing correlations.
Numerical investigation of the performance of several static mixers
Authors: Rauline Damien , Tanguy Philippe A. , Le Blévec Jean‐Marc , Bousquet Jacques
Published: March 2009

The performance of six static mixer (Kenics, Inliner, LPD, Cleveland, SMX and ISG) are compared using 3D numerical simulations in laminar creeping flow regime. Numerical pressure drop results are tested against experimental ones, showing overall a good agreement. Besides pressure drop, four criteria (extensional efficiency, stretching, mean shear rate and intensity of segregation) are chosen to compare the static mixers. It appears that Kenics, Inliner, LPD and Cleveland mixers are rather similar. The ISG mixer seems better than this first group of mixers, but pressure drop is too high compared to other advantages. From our numerical results, SMX appears to be the most efficient of the six compared static mixers.
Matériaux anodiques pour électrolyseurs
Authors: Devilliers Didier , Groult Henri
Published: March 2009

Cet article passe en revue les principaux types de matériaux anodiques actuellement utilisés dans les électrolyseurs industriels. Les mécanismes des réactions mises en jeu sont détaillés dans chaque cas, des exemples d'application et les perspectives offertes sont analysés. Une place importante est dédiée au carbone et aux oxydes de métaux précieux qui ont conduit au développement des “anodes dimensionnellement stables”. Dans ce dernier cas, on décrit le phénomène de désactivation par formation d'une couche passive entre le métal substrat et l'oxyde électrocatalytique.
Simulations of the effect of hydrodynamic conditions and properties of membranes on the catalytic performance of a fluidized‐bed membrane reactor for partial oxidation of methane
Authors: Ostrowski Thomas , Mleczko Leslaw
Published: March 2009

In a fluidized‐bed membrane reactor the selectivity of separation can be controlled by influencing the hydrodynamics of the fluidized bed. In this reactor type, with the mass transport limitation between bubbles and the emulsion phase, even with the non‐selective membranes, high selectivity of separation can be achieved. This opens the possibility for applications of membrane reactors for reaction systems for which selective membranes do not exist, e.g. when Knudsen‐type membranes or form‐selective separation can not be applied. This paper is aimed at explaining the interaction between the selectivity of separation and the hydrodynamics of the fluidized bed by means of simulations that were performed for a fluidized‐bed membrane reactor for catalytic partial oxidation of methane.
Removal of acetic acid from water by catalytic distillation. Part 2: Modeling and simulation studies
Authors: Xu Zhanping , Afacan Artin , Chuang Karl T.
Published: March 2009

A simulation program has been established by incorporating basic models for reaction kinetics, vapor–liquid equilibrium and mass transfer into Aspen Plus (Aspen Technology Inc., 1996) to simulate the catalytic distillation process for the removal of dilute acetic acid from water. The simulated concentration profiles agree well with those measured under various operating conditions.
Equilibrium conditions for the hydrogen sulfide hydrate formation in the presence of electrolytes and methanol
Authors: Mahadev Kal N. , Bishnoi P. Raj
Published: March 2009

Natural gas industry encounters systems that consist of gases like CO2 and H2S, and aqueous solutions of methanol and mixed electrolytes. A knowledge of the phase behavior of such systems, including hydrate formation, is essential in gas production and the design of facilities for gas transportation and processing. Recently, Dholabhai et al. (1997, 1996) and Bishnoi and Dholabhai (1998) described equilibrium conditions for CO2 and gas mixtures containing CO2 in the presence of methanol, electrolytes and ethylene glycol. In the present work aqueous three phase (aqueous liquid solution, vapor and incipient hydrate) equilibrium conditions of H2S hydrate formation in aqueous solutions of electrolytes and methanol are measured in the temperature range of 272 to 294 K and pressure range of 0.3 to 1.0 MPa. A ‘full view’ sapphire variable volume cell with a movable piston is used to obtain the experimental data.
Characterization of an airlift reactor with helical flow promoters
Authors: Schlötelburg Cord , Popovic Milan , Gluz Michail , Merchuk Jose C.
Published: March 2009

The helical flow promoter (HFP), inserted in the downcomer of an airlift reactor (ALR), generates a helical flow pattern in the circulating gas–liquid (solid) mixture. Data on the fluidization capacity, gas holdup, liquid velocity and mass transfer rate for two‐ and three‐phase systems with two different carboxymethylcellulose solutions collected in a 58 L ALR‐HFP are presented and compared with those of common pneumatic reactors. Generally, an increasing solid concentration led to a slight decrease in gas holdup and liquid velocity but to a considerable decrease in mass transfer rates. Insertion of HFPs produced a significantly enhanced fluidization capacity of solid particles compared to the common systems.
Production of liquid fuels from waste plastics
Authors: Scotp Donald S. , Majerski Piotr , Piskorz Jan , Radlein Desmond , Barnickel Michael
Published: March 2009

Exploratory work was carried out to develop a process for conversion of mixed plastic wastes into liquid transportation fuels or petrochemicals. The concept used is based on thermal depolymerization of the polymers in a suitable solvent followed by catalytic conversion of the resulting polymeric fragments into hydrocarbons with boiling points below 525°C. The process is carried out batch‐wise over a zeolite catalyst at temperatures from 350°C to 450°C and at atmospheric pressure. No hydrogen is used and volatile products formed are continuously removed from the reactor. Tests were carried out on polyethylene and polypropylene alone, and on mixtures of the two. Finally, a synthetic mixture of four different plastics was tested. From 90% to 98% of the plastic was converted to gases or distillable hydrocarbons. Of this yield, from 20% to 55% was gas, primarily propylenes and butylenes, and from 32% to 70% was a light hydrocarbon oil. Very little non‐distillable coke or residue was formed. The use of mixtures did not affect the high conversions obtained, but the results could only be approximately predicted based on a pro‐rating of results for the individual components.
(Gas‐)liquid‐solid circulating fluidized beds and their potential applications to bioreactor engineering
Authors: Zhu Jing‐Xu (Jesse) , Karamanev Dimitre G. , Bassi Amarjeet S. , Zheng Ying
Published: March 2009

Compared with conventional fluidized beds, circulating fluidized beds have many advantages including better interfacial contacting and reduced backmixing (Lim et al., 1995). While there are many reports on the gas—solid circulating fluidized systems, liquid—solid and gas—liquid—solid circulating fluidized bed systems have been scantily studied. However, extending current knowledge obtained in gas—solid systems to liquid—solids and gas—liquid—solid three‐phase systems is shown to open new horizons for applications of circulating fluidized bed technology and expected to lead to the development of highly efficient liquid—solid and gas—liquid—solid reactors, especially for the ever growing field of biotechnology. In order to fully appreciate the potential of those two types of liquid phase circulating fluidized beds, recent progress is reviewed in this article. Their potential applications to biochemical processes are also discussed.
Thermal and catalytic upgrading of a biomass‐derived oil in a dual reaction system
Authors: Srinivas Srimat T. , Dalai Ajay K. , Bakhshi Narendra N.
Published: March 2009

The thermal and catalytic upgrsding of bio‐oil to liquid fuels was studied at atmospheric pressure in a dual reactor system over HZSM‐5, silica‐alumina and a mixed catalyst containing HZSM‐5 and silica‐alumina. This bio‐oil was produced by the rapid thermal processing of the maple wood. In this work, the intent was to improve the catalyst life. Therefore, the first reactor containing no catalyst facilitated thermal cracking of blo‐oil whereas the second reactor containing the desired catalyst upgraded the thermally cracked products. The effects of process variables such as reaction temperature (350°C to 410°C), space velocity (1.8 to 7.2 h−1) and catalyst type on the amounts and quality of organic liquid product (OLP) were investigated, In the case of HZSM‐5 catalyst, the yield of OLP was maximum at 27.2 wt% whereas the selectivity for aromatic hydrocarbons was maximum at 83 wt%. The selectivities towards aromatics and aliphatic hydrocarbons were highest for mixed and silica‐alumina catalysts, respectively. In all catalyst cases, maximum OLP was produced at an optimum reaction temperature of 370°C in both reactors, and at higher space velocity. The gaseous product consisted of CO and CO2, and C1‐C6 hydrocarbons, which amounted to about 20 to 30 wt% of bio‐oil. The catalysts were deactivated due to coking and were regenerated to achieve their original activity.
A new expression of the Ks factor for helical ribbon agitators
Authors: Delaplace Guillaume , Leuliet Jean‐Claude
Published: March 2009

The purpose of this note is to present a new model that is able to predict an effective shear rate in a vessel equipped with helical ribbon agitators, when mixing shear‐thinning fluids. This model is based on well established results obtained for non‐Newtonian flow in cylindrical ducts.
On the validity of the gradient diffusion approach as applied to modelling particle dispersion in a turbulent gaseous flow
Authors: Lightstone Marilyn F. , Raithby George D.
Published: March 2009

This paper develops a criterion for predicting when gradient diffusion should adequately predict the dispersion of particles in simple gaseous turbulent flows such as round jets or the decay region of a grid‐generated turbulent flow. The development of this criterion involves deriving the solution to the gradient diffusion model by another route, where the assumptions required to yield the solution can be carefully considered. This derivation also provides an expression for the particle diffusivity. The model is then applied to two flows where particulate dispersion has been measured experimentally: flow behind a turbulence‐generating grid, and a round jet flow. Under conditions where the criterion for gradient diffusion is satisfied, good agreement is found between measurement and theory.
Model study of the direct causticization reaction between sodium trititanate and sodium carbonate
Authors: Nohlgren Ingrid , Theliander Hans , Zhuang Qianlin , Van Heiningen Adriaan R. P.
Published: March 2009

The solid state reaction between sodium tri‐titanate and sodium carbonate, forming mainly sodium pentatitanate, was investigated. Experiments were carried out in a micro‐differential reactor made of quartz glass at various temperatures between 800°C and 880°C and in a pilot fluidized bed reactor operated in a semi‐batch mode. In the former reactor, basic kinetic data was obtained by measuring the release of carbon dioxide. Different kinetic models were considered to describe the conversion, such as the Valensi‐Carter model for diffusion controlled reaction rates and the phase‐boundary model for first‐order reaction kinetics. Furthermore, a model that included both diffusion in the solid material and the chemical kinetics was derived. This model described the experimental data obtained in the micro‐differential reactor very well. However, for the fluidized bed experiments, these different kinetic models did not accurately describe the experimental data. Therefore, an improved model was developed, which also took into account the time taken for the reactants to achieve physical contact. This model gave good agreement with the experimental data.
Fault isolation in nonlinear systems with structured partial principal component analysis and clustering analysis
Authors: Huang Yunbing , Mcavoy Thomas J. , Gertler Janos
Published: March 2009

Partial principal component analysis (PCA) and parity relations are proven to be useful methods in fault isolation. To overcome the limitation of applying partial PCA to nonlinear problems, a new approach utilizing clustering analysis is proposed. By dividing a partial data set into smaller subsets, one can build more accurate PCA models with fewer principal components, and isolate faults with higher precision. Simulations on a 2 × 2 nonlinear system and the Tennessee Eastman (TE) process show the advantages of using the clustered partial PCA method over other nonlinear approaches.
Analyse des signaux temporels de pression dans un lit fluidisé turbulent de FCC
Authors: Taxil Isabelle , Bayle Jérome , Gauthier Thierry , Guigon Pierre , Archimbault Fabien
Published: March 2009

Le régime turbulent des lits fluidisés est un régime intermédiaire entre la fluidisation bullaire et le transport que l'on peut caractériser par l'analyse des enregistrements de pression en paroi dans le temps. Nos résultats expérimentaux confirment que l'analyse statistique de ces signaux permet de délimiter le régime turbulent. Une analyse fréquentielle originale montre de plus qu'il n'y a pas de changement systématique de fréquence dominante dans le régime turbulent, mais que les spectres fréquentiels s'enrichissent. L'analyse stochastique des signaux par la méthode de Hurst conduit à la měme conclusion.
Treatment of olive mill washing water by ultrafiltration
Authors: Mameri Nabil , Halet Farid , Drouiche Madani , Grib Hocine , Lounici Hakim , Belhocine Djamila , Pauss André , Piron Dominique
Published: March 2009

Olive oil production requires important quantities of washing water containing low oil concentrations, but classical processes used to recover or to eliminate this oil are ineffective. This study presents a membrane technique to treat olive oil mill washing water using different commercial ultrafiltration membranes: one organic (PCI) and two ceramic (Ceraver) membranes. The influence of the hydrodynamic parameters (transmembrane pressure and flow rate) and the cut‐off membranes on the efficiency of the ultrafiltration process was evaluated, and it was shown the organic PCI membrane could reduce pollution due to organic matter by decreasing the value of the Chemical oxygen demand by about 90%. Moreover, the nature of the ultrafine pore membrane appeared to be an important parameter which may strongly increase or decrease the capacity of the membrane. The membrane cut‐off did not have a strong influence on the performance of the process but if the membrane pores were too large the stability of the dynamically formed membrane decreased at transmembrane pressures greater than 0.2 MPa.