bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of charged additives and heat pretreatment on the dewatering of fuel‐grade peat
Authors: Cooper D.G. , Eccles E.R.A. , Sheppard J.D. 
Published: March 2009

AbstractThe addition of salt, mineral acid or polyelectrolyte or the preheating of fuel‐grade peat results in significant improvement of the amount of water released during mechanical pressing.The charged species all act by suppressing the charge on the colloidal particles and, for different reasons, organic salts, protons and polyelectrolytes are all more effective than simple inorganic salts. The cations with large organic portions, including surfactants, have an augmented adsorption to the particle surface because of the hydrophobic effect. The polyelectrolytes are strongly associated with the particles because of the chelate effect. Protons are very effective because they can actually neutralize the net charge on the particle surface by forming covalent bonds with the acid functions.The mechanism by which heat pretreatment improves dewatering is not caused by suppression of the surface charge. The effect could be due to melting or softening of peat waxes causing alterations of surface features which improve water release. It is also possible that heating provides sufficient energy to overcome the energy barrier keeping the particles apart.
De‐t‐butylation of t‐butylphenols over dealuminated zeolites in liquid‐solid system
Authors: Takahashi Takeshige , Kai Takami , Tashiro Masashi 
Published: March 2009

AbstractLiquid‐solid phase de‐t‐butylation of p‐t‐butylphenols was carried out over original and dealuminated zeolites to determine the effect of catalyst pore size and acidity on the reaction rate and catalyst fouling rate. The de‐t‐butylation rate over the original zeolites was mainly dependent upon their micro pore sizes. Although the dealumination by acid leaching decreased strong acid sites, the de‐t‐butylation rate over dealuminated HY zeolite was higher than that on the original zeolite. The present dealumination is a useful method to prepare an acid catalyst for de‐t‐butylation in a liquid‐solid system.
Models and methods of simulating gas pipeline blowdown
Authors: Botros K. K. , Jungowski W. M. , Weiss M. H. 
Published: March 2009

AbstractEstimation of gas pipeline blowdown time requires the determination of the pressure‐time history for the unsteady discharge of gas through a blowdown stack open to the atmosphere. Computational procedures entail various assumptions whose validity and contributions to the accuracy are often not assessed. This paper discusses the computational models and solution methods and further assesses the significance of the various assumptions involved.Volume and pipe models, numerical and analytical methods of solution, effects of stack entrance and friction losses and discharge coefficient are evaluated. The accuracy of a particular model or method of solution is greatly dependent on the fL/D ratio of the pipe section under blowdown. Comparison with field measurements of a straight pipe section and a complicated compressor station yard piping enabled evaluation of the above models.
Steady state hydrodynamics and mass transfer characteristics of a karr extraction column
Authors: Camurdan M. C. , Baird M. H. I. , Taylor P. A. 
Published: March 2009

AbstractThe steady state hydrodynamics of the holdup in a 15 cm column agree quite well with mechanistic predictions at conditions approaching flooding. In the presence of mass transfer (acetic acid from the dispersed kerosene phase to the continuous water phase), the holdup data below flooding are not well predicted by the model due to enhanced droplet coalescence. The prediction of holdup at flooding is a function of the ratio of the flow rates but is independent of the physicochemical properties of the extraction system, and therefore can be used to estimate the flooding holdup regardless of the occurrence of mass transfer. In the second part of the paper, steady state mass transfer characteristics of the column were also simulated using a mechanistic model. Despite the difficulty of estimating parameters such as the mass transfer coefficient, the model curves could be arbitrarily adjusted to fit observed exit concentrations. These steady state results provide useful insights on the non‐linearity of the system from a control viewpoint.
Factors affecting cake resistance in non‐Newtonian filtration
Authors: Kozicki W. 
Published: March 2009

AbstractA methodology for evaluation of surface effects including polymer adsorption‐gel formation or slip within the pores of a filter cake has been developed and applied to constant pressure filtration of calcium carbonate in aqueous hydroxyethyl cellulose (Natrosol 250G, Hercules Powder Company) slurries. The fundamental framework of non‐Newtonian filtration is generalized to include the Blake, Kozeny‐Ergun and Kozeny‐Carman cake models and the cake resistances γK and αR, in conjunction with the correction terms JRN and Jgen, within a unified framework. Relationships are developed between the latter quantities and the effect of the bed model on the evaluations of the filtration characteristics is delineated.Significant polymer adsorption‐gel formation was found to take place in the constant pressure filtration of calcium carbonate in aqueous Natrosol 250G slurries. The resultant cake porosities were larger and the effective cake porosities lower than comparable porosities for cakes deposited from water slurries.The wide variation of JRN with the characteristic index N is attributed to the small size of the slurry particles. Polymer adsorption is shown to extend, and slip on the particle surface to reduce the variation of JRN with N.
Natural convection in liquid encapsulated czochralski growth of gallium arsenide
Authors: Sabhapathy P. , Salcudean M. E. 
Published: March 2009

AbstractThe natural convection in the melt during LEC growth of GaAs is studied numerically for a crucible radius of 0.1 m, melt heights 0.025 m and 0.05 m, and crystal radii 0.025 m and 0.05 m. When only the crucible side wall is heated, the flow is unicellular moving up the side wall, along the melt‐encapsulant interface, downward beneath the crystal, and along the bottom toward the side wall. With heating at the top of the crucible, the side wall temperature can be lowered without freezing the melt near the melt‐encapsulant interface. The flow is often multi‐cellular when the bottom of the crucible is heated. An optimum heating at the top and bottom of the crucible can flatten the isotherms near the crystal‐melt interface and improve the diameter control.
Adsorptive separation of Kr from N2‐Part II. Development of a pilot unit
Authors: Tezel F. H. , Ruthven D. M. , Boniface H. A. , Sridhar T. S. 
Published: March 2009

AbstractDesign and development of a pilot scale chromatographic process for separation of trace amounts of krypton from a nitrogen atmosphere is described. The system uses a large column (1.20 m × 0.055 m i.d.) packed with H‐mordenite adsorbent and operated under overload conditions. A preliminary economic evaluation suggests that this process is competitive with the conventional cryogenic distillation process.
Sparged loop reactors
Authors: Joshi J. B. , Ranade V. V. , Gharat S. D. , Lele S. S. 
Published: March 2009

AbstractCirculating bubble columns or loop reactors form one of the important classes of modified bubble columns. The present paper analyses the performance of external loop air lift reactors (EL‐ALR). The EL‐ALR has many advantageous features especially at large scale. These arise from its feature of having controlled liquid circulation which is the key parameter for the design and operation of EL‐ALR contactors. Therefore, a reliable and generalised circulation model has been presented. The reliability of the model depends on the accuracy of the predictive methods for the gas hold‐up and the two‐phase fractional pressure drop. Detailed analysis of these fundamental parameters of gas‐liquid flows has been presented. The effects of design (area ratio of riser to downcomer, height to diameter ratio and volume of reactor) and operating (gas flow rates and sparging locations) parameters on the performance of the EL‐ALR have been analysed in detail. A rational basis has been developed for the estimation of pressure drop, mixing time and mass transfer coefficient. An optimum combination of design and operating parameters has been suggested and a criterion has been developed for the optimum location of spargers. An attempt has been made to provide critical analysis of the published information and to construct a coherent picture of EL‐ALR.
Generic model control — A case study revisited
Authors: Harris T. J. , Mclellan P. J. 
Published: March 2009

AbstractThe application of the Generic Model Control (GMC) algorithm to the control of an evaporator has been reported recently by Lee et al. (1989). The results of their case study are claimed to demonstrate the superiority of the nonlinear GMC algorithm over conventional techniques including Dynamic Matrix Control. In this note it is shown that for the evaporator example the improved performance arises primarily from the full multivariable and feedforward nature of the control law, rather than from the nonlinear nature of GMC.
Impingement heat transfer under a confined slot jet. Part I: Effect of surface throughflow
Authors: Polat S. , Mujumdar A. S. , Douglas W. J. M. 
Published: March 2009

AbstractLocal and average heat transfer coefficients were measured for a confined turbulent slot jet impinging on a permeable surface at which there may be throughflow. Local Nusselt number was obtained using a unique porous sensor designed for measurement of local heat transfer at a permeable surface which is subjected to rapidly and widely varying heat transfer. Measurements were performed for a wide range of jet Reynolds number and throughflow rates. Convective heat transfer coefficients was found to be enhanced by throughflow, and the enhancement factor in terms of Stanton number to be independent of jet Reynolds number and of extent of heat transfer area.
Interaction between micro‐ and macro‐mixing during reactions in agitated tanks
Authors: Thoma S. , Ranade V. V. , Bourne J. R. 
Published: March 2009

AbstractThe present investigation focusses on the interactions between micro‐and macro‐mixing in a stirred tank reactor, operated in the semi‐batch mode. With long feed times only micromixing controls reaction, but below a critical feed time macroscopic gradients also become important. Experiments generated a coherent data set which can be used as a design guide and also for model validation. A competitive, consecutive azocoupling reaction was carried out, whereby imperfect mixing produces finite values of XS (yield of secondary product) which can be conveniently used as a mixing index. The influences of feed location, feed rate, stirrer speed, concentrations and vessel size on selectivity were studied. The micromixing model of Baldyga and Bourne (1989) was extended to include interactions between macro‐and micro‐mixing and should be valid for feed times below the critical value, although not so short as the macromixing time in the vessel. Model predictions were compared with the experimental results.
Forced convection subcooled boiling of binary mixtures
Authors: Sivagnanam P. , Balakrishnan A. R. , Varma Y. B. G. 
Published: March 2009

AbstractA mode based on an additive mechanism of heat transfer is proposed for forced convection subcooled boiling of binary mixtures. The contributing modes of heat transfer are: (i) the heat transferred as latent heat by the rising bubbles, (ii) the heat transferred as the heat contained in the superheated thermal layer that is removed from the surface in the wake of the rising bubbles and (iii) the single phase forced convection heat transfer from the heating surface not influenced by the bubbles. Experimental data from the literature on binary systems show good agreement with the model, validating the postulated mechanism.
Convection naturelle transitoire dans les liquides à viscosité variable
Authors: Maslouhi A. , Robillard L. 
Published: March 2009

AbstractOn étudie le rǒle de la viscosité dépendant linéairement de la température sur la convection laminaire le long d'une plaque verticale soumise à un flux de chaleur constant. L'analyse est basée sur la résolution numérique des équations de couche limite instationnaire utilisant une procédure implicite de différences finies. On présente les profils de vitesse de température et du nombre de Nusselt à l'état permanent et dans la période transitoire. En régime transitoire, les champs de vitesse et de température atteignent une valeur maximale avant de décroǐtre légèrement jusqà leurs valeurs permanentes. Ce phénomène appelé “overshoot”, peut ětre amplifié ou atténué selon les valeurs que l'on donne au paramètre sans dimension caractérisant la variation de la viscosité.
Carbon monoxide hydrogenation over cobalt catalyst in a tube‐wall reactor: Part II. Modelling studies
Authors: Dalai A. K. , Esmai M. N. , Bakhshi N. N. 
Published: March 2009

AbstractA mathematical model was developed to predict the performance of Fischer‐Tropsch Synthesis over cobalt catalyst in a tube‐wall reactor. Comparison was made between model predictions and previous experimental results (part 1 of this paper) for pressures 0.35‐1.03 MPa, temperatures 250−275°C, and exposure velocities 139‐722 μ/s. The agreement was good. The model predicts an increase in methanation activity with temperature. Carbon monoxide and hydrogen conversions, and water and carbon dioxide concentrations increase along the reactor axis. With an increase in exposure velocity, hydrocarbons and carbon dioxide production increase, but water production decreases. However, the water‐gas shift activity increases continuously along the reactor axis. The model is based on two‐dimensional transport equations, and employs the orthogonal collocation method in its numerical predictions.
Production of annatto concentrates in spouted beds
Authors: Massarani G. , Passos M. L. , Barreto D. W. 
Published: March 2009

AbstractAnnatto is composed of a natural reddish‐yellow pigment, which is commonly used in the food, cosmetic and pharmaceutical industries. This pigment is easily extracted from Bixa orellana seeds by particle impact and attrition rather than by solvent extraction. Seeds must be dried at a safe temperature to preserve the pigment quality. Experiments show that the annatto powder produced in a non‐conventional spouted bed has a high pigment content and is thus suitable for commercial use. A comparative analysis of the bixin extraction in different systems demonstrates that this spouted bed unit can be competitive for commercial applications. Hydrodynamic and drying parameters were studied to improve the powder production rate in this unit.
Influence of geometry on gas holdups in a reversed flow jet loop reactor
Authors: Padmavathi G. , Remananda Rao K. 
Published: March 2009

AbstractThe effects of ratio of draft tube to reactor diameter (Dd/D), liquid nozzle diameter (dN), aeration tube diameter (dG) and immersion height of the two‐fluid nozzle into the draft tube (HN) on overall and annulus gas holdups for the air‐water system were evaluated experimentally in a reversed flow jet loop reactor over wide ranges of gas and liquid flow rates. Both the gas holdups increased with increasing gas and liquid flow rates and with decreasing dN and HN. The influence of dG on gas holdups is found to vary with gas flow rates. Correlations are proposed to predict gas holdups.
Solid‐liquid equilibria in the ternary system nacl‐kcl‐h2o
Authors: Farelo F. , Von Brachel G. , Offermann H. 
Published: March 2009

AbstractBinary and ternary solubility data were measured for the NaCl‐KCl‐H2O system in the temperature range 293‐360 K using a standard visual method. The solid‐liquid phase diagram of the ternary system was calculated from the binary data and from the activity coefficients of the electrolytes evaluated by the Pitzer model. Some empirical functions of temperature were used to describe the virial coefficients. The calculated ternary solubilities were compared with the experimental values yielding a very good agreement. Therefore, it was possible to conclude that, in the range of concentration and temperature studied, the Pitzer model provides an excellent representation of the activity coefficients, thus allowing the accurate prediction of solubilities in the ternary system.
Hydrogen evolution in alkaline solution on electrolytic nickel‐cobalt and nickel‐iron deposited with different bath compositions and current densities
Authors: Fan Chonglun , Piron D. L. , Meilleur M. , Marin L.‐P. 
Published: March 2009

AbstractNickel‐cobalt and nickel‐iron electrodeposits were characterized as hydrogen electrodes in alkaline water electrolysis (6 mol/L KOH, 25°C). The nickel‐based codeposits were fabricated with different bath compositions and at different current densities. The hydrogen evolution in water electrolysis on the nickel‐based codeposits was apparently enhanced as compared with that on nickel. The improvement of the electrocatalytic behaviour of the hydrogen electrodes is attributed to their composition and an increase of their active surface, which are dependent on the electrodeposition conditions.
Computer‐aided Measurement of Vapor‐Liquid Equilibrium in a Still
Authors: Hiaki Toshihiko , Yamato Kazutaka , Miyazawa Hajime , Kojlma Kazuo 
Published: March 2009

AbstractIsothermal vapor‐liquid equilibria were measured using a still with the aid of a computer for control of the temperature and measurement of the total pressure. The measurements were made with circulation of both the vapor and liquid phases in a still of the Rogalski and Malanowski type (1980). The isobaric vapor‐liquid equilibria were measured for the benzene + 2‐propanol system at 101.3 kPa in order to test the consistency of results obtained with this still. Isothermal vapor‐liquid equilibria were measured for the 2,3‐dimethylbutane + methanol system at 313.15 K. The experimental data were correlated with the Wilson (1964) equation.
Co‐Extraction — Selective stripping for the recovery of nickel and copper from the leach liquor of ocean nodules
Authors: Pandey B. D. , Bagchi D. , Kumar Vinay 
Published: March 2009

AbstractFerromanganese deep sea nodules of the Indian Ocean have recently been recognised as a potential source of metals like copper, nickel, cobalt and manganese. For the treatment of the sea nodules following the reduction roast‐ammonia leach process, the leach liquor containing copper, nickel and cobalt was processed to separate and recover these metals by solvent extraction (SX) using 25% LIX 64N in kerosene. Almost quantitative extraction of copper and nickel was realized in a continuous run. During nickel stripping, the small amount of copper in the nickel solution was removed by incorporating a copper extraction step using 10% LIX 64N in kerosene. The purified pregnant nickel electrolyte was electrowon in a non‐diaphragm cell. Copper was similarly recovered by electrowinning (EW). A closed circuit of SX‐EW was run to produce cathodes of nickel and copper with energy consumptions of 3.85 and 2.01 kWh/kg for the respective metals.
The maximum spoutable bed heights of fine particles spouted with air
Authors: Çeçen Ayşe 
Published: March 2009

AbstractThe maximum spoutable bed heights of systems of fine glass spheres spouted with air are studied in flat based semi circular columns of 80 and 152.4 mm diameters using particles with average diameters ranging from 0.3 to 1.3 mm.New correlations are proposed to predict the maximum spoutable bed heights of air spouted fine particle systems. It is concluded that the influence of the column diameter on the maximum spoutable bed height is significantly decreased compared to coarse particle systems and that it further varies with particle size within the fine particle spouting regime. Data reported in the literature agree with the proposed correlations.
Mass transfer enhancement of acetic acid across a plane kerosene/water interface by an electric field
Authors: Glitzenstein A. , Tamir A. , Oren Y. 
Published: March 2009

AbstractThe intensification of mass transfer of acetic acid from kerosene into water across a plane interface by the application of an electric field normal to the interface is investigated.The application of an electric field affects mainly mass transport through the bulk of the organic phase rather than the interface. In the range (5–30) × 104 V/m the mass transfer coefficient changes from 8 × 10−6 to 2 × 10−5 m/s. A model based on the movement of electric charges in the organic phase indicates that a Sherwood‐Grashof correlation for free convection only is also suitable for the electrically driven process if the Grashof number is modified to take into account the effect of the electric field on the movement of the electric charges.
Cinétique de la calcination du coke de pétrole en atmosphères neutre et oxydante
Authors: Dubuisson C. , Charette A. , Kocaefe D. 
Published: March 2009

AbstractUne étude cinétique de la dévolatilisation d'échantillons représentatifs de coke de pétrole est menée sous des conditions proches de celles existant dans les fours industriels de calcination. On analyse les effets de la nature du milieu (neutre ou oxydant), du taux de chauffage et du pourcentage d'oxygène en milieu oxydant. Les expériences sont réalisées dans un four à induction et mettent en oeuvre des analyses thermogravimétriques et chromatographiques. Les résultats montrent que, sous certaines conditions, la nature du milieu influence le processus de dévolatilisation. En atmosphère oxydante, un taux de chauffage faible et un contenu faible en matières volatiles favorisent une attaque du coke par l'oxygène. Les comportements réactionnels sont établis en suivant les concentrations de CH4, H2, CO et CO2. Dans les régions où le coke n'est pas attaqué, un modèle cinétique permet de comparer les paramètres (ordre de réaction, énergie d'activation et facteur pré‐exponentiel) caractérisant le phénomène de dévolatilisation dans les deux milieux (neutre et oxydant). On constate que le milieu oxydant favorise une augmentation de l'énergie d'activation.
Déformation subie par une nappe de mercure soumise à l'impact d'un jet liquide bidimensionnel immergé
Authors: Bensmaili A. , Coeuret F. 
Published: March 2009

AbstractLe travail étudie la déformation subie par une nappe de mercure recevant perpendiculairement un jet liquide immergé bidimensionnel de faible épaisseur. On a fait varier la largeur du jet, le nombre de Reynolds d'injection et la hauteur du jet. On a mesuré expérimentalement la profondeur et le diamètre de la cavité faite par le jet dans la nappe de mercure et on a comparé les valeurs obtenues à des expressions théoriques de la littérature. En dépit de l'échelle relativement réduite, le comportement du système étudié est décrit convenablement par des modèles proposés pour des sytèmes à grande échelle.