bluuebunny/crossref_metadata_2025_split huggingface dataset:
Etude numérique et paramétrique de la combustion de particules d'aluminium
Authors: Basse T. , Daniel E. , Loraud J. C. 
Published: March 2009

AbstractDans le but de prendre en compte la réactivité des particules d'aluminium issues de la combustion des pains de prop ergol solide qui sont placés dans les lanceurs spatiaux, plusieurs modèles numériques ont été éprouvés. Notre choix s'est rapidement porté sur le modèle de Law puisqu'il permet de transiter continǔment d'une goutte d'aluminium à une goutte d'oxyde et de connaǐtre la taille du residu en fin de combustion ceci pouvant expliquer les dépǒts importants observés dans les moteurs fusée. En vue d'y étudiér les couplages écoulement / combustion, la combustion de gouttes d'aluminium a été largement analysée au travers de calculs 0D mettant en évidence les principaux rouages du processus de combustion.
The characterization of solid residues from PFBC boilers
Authors: Anthony Edward J. , Iribarne Agripina P. , Iribarne Julio V. 
Published: March 2009

AbstractPFBC is one of the two important advanced fossil fuel technologies, now available. It permits the combustion of fossil fuels with extremely low emissions, while also achieving high electrical conversion efficiencies. However, relatively little is known about the ash characteristics, despite the existence of several demonstration units. This study looks at bed and cyclone ash from two of these boilers, the Spanish PFBC plant at Escatron in Spain, and the Tidd plant in Brilliant, Ohio. In particular, these ashes are examined using both conventional and some newly developed techniques in order to determine their chemical speciation. This work confirms the ashes have extremely low free lime contents (1% or less), and extremely low elemental carbon. More surprisingly, the existence of significant amounts of dolomite in the cyclone ashes from the Tidd plant has been demonstrated, and significant quantities of other calcium compounds (i.e. silicates, ferrites etc.) have also been shown in the bed ashes from the Spanish plant. One other interesting observation is the presence of low levels of sulphides in the ashes from the Escatrón unit, and its total absence from the Tidd unit which used dolomite rather than calcitic limestone. These results also clearly indicate that ashes from PFBC plants are likely to be significantly easier to dispose of in landfills than AFBC ashes, and should have considerably better potential for use in cemen‐titious applications.
Power consumption and mass transfer in agitated gas‐liquid columns: A comparative study
Authors: Gagnon Hélène , Lounès Mustapha , Thibault Jules 
Published: March 2009

AbstractPower consumption, gas holdup and oxygen mass transfer in agitated gas‐liquid columns have been studied for an air‐water system. Measurements have been carried out in a reciprocating plate reactor using five different types of perforated plates and in a stirred tank reactor with one, two and three Rushton turbines, a helical ribbon impeller with and without surface baffles. Each mixing vessel had an identical geometry with a working volume of 17 L. For reciprocating plate stacks, the gas holdup is a complex function of the perforation diameter, the frequency of agitation and the gas superficial velocity. For radial‐type mixing devices, the gas holdup increases more rapidly with the speed of rotation for the helical ribbon. The power imparted to the fluid by the mixing device is independent of the gas superficial velocity for the plate stacks and the helical ribbon impeller for a given frequency or speed of agitation whereas it decreases for Rushton turbines. The correlation of the power consumption obtained for all mixing devices plotted against the reciprocating frequency or speed of rotation to the third power shows a linear fit. KLa values were correlated very well with the power input per unit volume and superficial gas velocity for all mixing devices. At lower power input per unit volume, KLa is a function of only the gas superficial velocity. At higher input power per unit volume, KLa increases rapidly with an increase in the intensity of agitation. Reciprocating plates with larger diameter perforations led to higher KLa values whereas the lowest KLa were obtained with the helical ribbon impeller. Correlations for one and three Rushton impeller assemblies were almost identical whereas measured KLa were much higher for the two‐impeller assembly due to the presence of a highly mixed zone in the vicinity of the dissolved oxygen probe.
Unsuspended mass of solid particles in stirred tanks
Authors: Brucato Alberto , Brucato Valerio 
Published: March 2009

AbstractAn original technique for the determination of the fraction of unsuspended solid particles at agitation speeds smaller than Njs, is proposed. The technique is based on the “twin‐systems” concept and is completed by a suitable tracing and detection technique for the solid phase. Results obtained with a fully baffled tank stirred by a Rushton turbine impeller show that the fraction of solids never leaving the tank bottom can be simply correlated to the ratio between agitation speed and Zwietering's complete suspension speed. It is shown that at agitator speeds of about 80% of Zwietering's complete suspension speed, practically all particles but a few, are already suspended. This finding implies that large energy and installation cost savings can be achieved, with respect to current design practices, without significantly affecting the solid‐liquid mixing performance.
Agitation power for solid‐liquid suspensions containing large particles
Authors: Bubbico Roberto , Cave Sergio Di , Mazzarotta Barbara 
Published: March 2009

AbstractThe agitation power required by liquid‐solid suspensions of large PVC discs (4.3 mm) and sand granules (1.29 mm) in water was measured for various solids concentration, up to 16% by volume, using 5 different impellers. In all cases the dispersed power increased with increasing solids content, more than expected based on the suspension density. The solid phase actually dissipates energy due to particle‐liquid friction and in the collisions of the particles. The amount of energy dispersed according to these mechanisms is generally low, but becomes evident with the large particles as the solid concentration increases above 4%.
Calculation of the particle size distribution in suspension polymerization using a compartment‐mixing model
Authors: Vivaldo‐Lima Eduardo , Wood Philip E. , Hamielec Archie E. , Penlidis Alexander 
Published: March 2009

AbstractA modelling strategy for effective estimation of the particle size distribution (PSD) in suspension polymerization is presented. The strategy consists of coupling a population balance equation (PBE) and a compartment‐mixing (CM) model to account for the non‐homogeneous mixing in the tank reactor. The values for the rate of energy dissipation of each compartment are estimated from Computational Fluid Dynamics (CFD) calculations and experimental reports on systems with the same agitator and geometric characteristics. Model predictions using the CM model are compared with predictions that assume homogeneous mixing and experimental data on PSD from styrene and divinylbenzene pilot‐plant suspension polymerization reactors of 1 and 5 L with Rushton and PBT impellers.
Effect of blade pitch on the structure of the trailing vortex around rushton turbine impellers
Authors: Lu Wei‐Ming , Yang Bing‐Shiou 
Published: March 2009

AbstractEffect of blade number on the structure of the trailing vortex around the Rushton turbine impeller is examined by analyzing the data of mean velocities, deformation rates, turbulent kinetic energy and energy dissipation rates for 2‐, 4‐, 6‐ and 8‐straight blades disk turbine impellers in a baffled standard geometry stirred tank. The data of Sauter mean bubble diameter near the blade tip are combined with the turbulent characteristics around the vortex to discuss how the blade number and the strength of the vortex affect the performance of the gas dispersion around the Rushton turbines under a low gassing rate. The results of this analysis show that if power input per each blade is the same, the impeller having four blades not only has the strongest average mean deformation rates and the largest turbulent kinetic energy, but also disperses the smallest average bubbles under the same gassing rate.
A study of an up‐ and a down‐pumping wide blade hydrofoil impeller: Part I. LDA measurements
Authors: Mishra Ved P. , Dyster Kate N. , Nienow Alvin W. , Mckemmie Jack , Jaworski Zdzislaw 
Published: March 2009

AbstractA wide blade, high solidity ratio, axial flow hydrofoil impeller has been developed particularly for gas dispersion when used in the upward‐pumping mode. It has a low power number so that a relatively low torque is required when using it with a large impeller to tank diameter ratio, a commonly desired aim of retrofitting. As part of the work characterising these impellers, laser Doppler anemometry has been used to study the single phase flow both down‐ and up‐pumping, the latter for the first time. Mean and root‐mean‐square velocities were measured throughout a fully baffled, flat bottomed cylindrical tank. When down‐pumping, the discharge flow was almost axial but when up‐pumping, it had a strong radial component. Turbulence energy dissipation rates in the impeller region and the discharge stream when up‐pumping were found to be higher than those when down‐pumping. In both modes, the impeller was found to have a high circulation efficiency. In Part II, the data presented here are used for obtaining computational fluid dynamic solutions of the flow field.
Numerical prediction of wall mass transfer rates in turbulent flow through a 90° two‐dimensional bend
Authors: Bergstrom Donald J. , Bender Trevor , Adamopoulos George , Postlethwaite John 
Published: March 2009

AbstractThe present paper reports a numerical study of mass transfer in a curved channel flow using a low Reynolds number k–ε model modified to include the influence of curvature on the turbulent transport. Predictions were obtained of flow through a 90° 2‐D bend for Reynolds numbers of Re = 2 × 104, 105 and 106, curvature ratio's of Rc/d = 1, 1.5 and 3, and Schmidt numbers of Sc = 500, 1 500 and 5 000. Based on the numerial simulations, the value of the mass transfer coefficient, k, was observed to generally decrease and increase along the inner and outer walls, respectively, compared to the value in a straight duct. The behaviour appears to be sensitive to both the curvature ratio and Reynolds number, being most pronounced for the case of tight bends and low Reynolds numbers.
The solubility of methane in aqueous solutions of monoethanolamine, diethanolamine and triethanolamine
Authors: Carroll John J. , Jou Fang‐Yuan , Mather Alan E. , Otto Frederick D. 
Published: March 2009

AbstractThe solubility of methane in 3 kmol/m3 solutions of monoethanolamine, diethanolamine, and triethanolamine was measured from 25° to 125°C and pressures up to about 13 MPa. Measurements were also made for the solubility of methane in water at 25° to 125°C and pressures up to 18 MPa in order to confirm the accuracy of the experimental technique. It is demonstrated that methane is more soluble (in terms of mole fraction) in the amine solution than in pure water. Furthermore, the solubility is an increasing function of the size of the alkanolamine. The solubility data were modeled using a Henry's‐law approach and the results summarized in terms of salting‐in coefficients.
Application of iterative dynamic programming to optimal control of a distiltation column
Authors: Fikar Miroslav , Latif Abderrazak M. , Fournier Frantz , Creff Yann 
Published: March 2009

AbstractIterative Dynamic Programming (IDP) is proven to be a useful technique for solving constrained dynamic optimisation problems. A high purity binary distillation column model has been chosen to investigate some of the IDP properties as well as its applicability. The investigated problems cover transitions from one steady state to another with the minimization of a quadratic cost function with associated terminal constraints.
Two‐liquid flotation of fine oxide particles with 8‐hydroxyquinoline
Authors: Kusaka E. , Maegawa K. , Nakahiro Y. , Fukunaka Y. , Ninae M. 
Published: March 2009

AbstractThe two‐liquid flotation of fine oxide particles has been investigated using a chelating‐type collector of oxine and the isooctane‐water two‐liquids system. The recovery was enhanced in a certain pH range. The oil‐floatability during two‐liquid flotation was concerned with the oxine adsorption on the solids. In addition, solution‐chemical calculations indicated that the reactivity of the metal cation with oxine based upon a surface precipitation model was closely related to the adsorbability of oxine and, hence, to the oil‐floatability of the solids. Also, the possible conditions for collection by two‐liquid flotation were experimentally determined and were related to the solution‐chemical criterion.
Heat transfer between FCC catalyst and an electrically heated horizontal cylinder in a circulating fluidized bed
Authors: Courbariaux Yann , Pugsley Todd , Couturier Michel 
Published: March 2009

AbstractThe heat transfer coefficient between a suspension of FCC particles and a horizontal cylindrical heat transfer probe inserted into the riser or the standpipe of a CFB has been quantified. With the heat transfer probe located in the riser 4.75 meters above the L‐valve, and solids mass flux varied between 0 to 100 kg/(m2·s), the heat transfer coefficient ranged from 70 W/(m2·K) to 475 W/(m2·K). On a plot of heat transfer coefficient versus solids mass flux, three zones have been identified, which correspond to the difference in the flow structure of the solids around the heat transfer probe as the solids mass flux increases. Also, measurements were taken of the radial solids flux in two orthogonal directions using an isokinetic sampling system. The data shows the asymmetry due to the perturbations introduced by the heat transfer probe. Finally, the heat transfer in the downcomer was investigated. It has been found that the magnitude of the heat transfer coefficient in the downcomer is dominated by the solids flux; variation in gas bypassing in the standpipe has little effect. Results obtained by traversing the heat transfer probe across the diameter of the standpipe suggest that the heat transfer coefficient is nearly independent of radial position within the standpipe.
Characterization of gas fluidized beds of group C, A and B particles based on pressure fluctuations
Authors: Bai Dingrong , Grace John R. , Zhu Jing‐Xu 
Published: March 2009

AbstractPressure fluctuation data were obtained with a quick response transducer at a sampling frequency of 100 Hz for periods of 100 s (i.e. 10,000 points) in order to characterize the gas‐solid flow behaviour of fluidized beds of six powders. For beds of Geldart group B and group A particles, the occurrence and movement of bubbles caused vigourous pressure fluctuations of relatively large scale and weak dominant frequency. For beds of group C particles, on the other hand, pressure fluctuations were significantly smaller in scale and exhibited large dominant frequencies, with no clear formation of bubbles. The standard deviation of pressure fluctuations was markedly higher for the group A particles than for the group C powders. Group C particles could be characterized by gas voids and channels which exhibit periodic behavior, while beds of group A and B particles behaved in a less periodic manner and were dominated by more random and intensive bubble motion. Chaotic time series analysis was carried out for the six different species of particles. The Hurst exponent demonstrated differences between the three different powder groups. The two‐phase character of gas‐solids flow was more distinguishable for the group B and A powders than for the group C powders.
Pressure losses in orifices for the flow of gas‐non‐newtonian liquids
Authors: Samanta Arun Kumar , Banerjee Tapan Kumar , Das Sudip Kumar 
Published: March 2009

AbstractAn investigation has been carried out to evaluate the two‐phase pressure drop for gas‐non‐Newtonian liquid flow across orifices. The method of dimensional analysis was used to correlate the experimental data. The correlation developed predicts the two‐phase frictional pressure drop across the orifices with acceptable statistical accuracy.
The effects of temperature and viscosity on glucose diffusivity through saccharomyces cerevisiae biofilms
Authors: Converti Attilio , Zilli Mario , Arni Saleh , Di Felice Renzo , Del Borghi Marco 
Published: March 2009

AbstractThe present study helps us to understand the effects of temperature and viscosity on bioprocesses in immobilized cell bioreactors. Glucose diffusivities through Saccharomyces cerevisiae biofilms are experimentally investigated at variable biofilm thickness, temperature, and concentration of carboxymethylcellulose (CMC) used as viscosity‐raising additive. Comparing these experimental values with those for free diffusion of glucose in water shows us that biofilm strongly reduces diffusivity (about 74%), mainly due to a decrease in the effective diffusion area. Only a slight increase in diffusivity is observed when biofilm thickness is increased. In addition, the results obtained in this work demonstrate that the well‐known empirical equations of Wilke and Chang, and of Guzman and Andrade can be combined to a relationship which takes into account the simultaneous effects of temperature and viscosity on the effective glucose diffusivity. This equation appears to be valid in glucose aqueous solutions whether or not biofilm is used, whereas it is not applicable when viscosity‐raising additives, such as CMC, are used.
An experimental study of double‐to‐single‐loop transition in stirred vessels
Authors: Montante G. , Brucato A. , Lee K. C. , Yianneskis M. 
Published: March 2009

AbstractThe velocity characteristics of the flows in a fully baffled vessel of diameter T = 290 mm stirred by a Rushton impeller of diameter D = T/3 were investigated by means of laser‐Doppler anemometry measurements. The effects of clearance and rotational speed on the flow patterns in the vessel were studied. It was found that at impeller clearances from the bottom of the vessel (C) around 0.2 T the characteristic double‐loop flow pattern undergoes a transition to a single‐loop one with the impeller stream direction becoming partly axial and being inclined at around 25 to 30° to the horizontal. The impeller stream inclination varied with radial distance from the impeller, as well as with angular position between blades (blade angle). Impeller speed was found to have no effect on the flow pattern or the mean velocities and turbulence levels normalized by Vtip for C/T > 0.20 or C/T ≤ 0.15. The flow structure measured with C = 0.15T is described in detail and the implications of the data for fluid mixing in stirred vessels are discussed.
Theoretical and experimental analysis of methane steam reforming in a membrane reactor
Authors: Madia Giuseppe S. , Barbieri Giuseppe , Drioli Enrico 
Published: March 2009

AbstractThermal effects on methane steam reforming process were analyzed, in a Pd‐Ag (23wt%) membrane reactor as a function of several parameters, such as temperature, reactant and sweep‐gas flow rate, and reactant molar ratio. Heat transfer from the oven was very important for the outlet methane conversion, which also depends on the temperature profile along the reactor. In particular, when the reactant flow rate was high the conversion degree decreased because the energy supplied was not sufficient to maintain the temperature in the reactor. A non‐isothermal mathematical model was presented which reproduced the experimental data.
Optimization of air distribution in direct reduction process in rotary kilns
Authors: Ramakrishnan V. , Sai P. S. T. 
Published: March 2009

AbstractAn algorithm for optimization of the air distribution in direct reduction process in rotary kilns akin to the SL/RN process is proposed, based on Pontryagin's continuous maximum principle. The optimum air distribution has been obtained for given operating conditions. The optimum air distribution has been found to have a definite pattern with small changes due to variation in process conditions. Air distribution has been found to be the most important parameter, which could be suitably chosen to obtain desired operating conditions. The influence of operating parameters, such as iron and carbon concentration in the charge, oxide and coal reactivity, have been studied and the process behaviour has been analyzed. Performance of the process has been observed to improve for an increase in oxide and coal reactivity and iron and carbon concentrations in the charge.
Mixing in multiple‐impeller stirred tank reactors with boiling liquids
Authors: Dohi Naoki , Matsuda Yukimasa , Itano Norihiro , Shimizu Kazuhiro , Wa Kimio Mineka , Wase Yoshinorika 
Published: March 2009

AbstractMixing in a boil‐off mechanically stirred tank reactor with multiple impellers was examined. Power consumption and gas hold‐up were measured in boiling water in a 0.2 m i.d. stirred tank reactor with three four‐pitched blade downflow disk turbines. Vapour was generated from both the immersed ring heater and the impellers. At low vapour generation rates, vapour was mainly generated from the impellers rather than from the heater, whereas nucleation occurred at the heater instead of the impeller at higher vapour generation rates. The mechanical power consumption decreased due to vapour generation. The change in boiling‐to‐non‐boiling mechanical power ratio with varying impeller rotational speed and boiling rate was complicated and not monotonous except at higher impeller speeds and boiling rates. The gas hold‐ups increased with increasing vapour generation rate but were rather small as compared to those in cold gas dispersing systems. Empirical correlations for power consumption and gas hold‐up in boiling liquids were developed using the present experimental data.
kL a correlation established on the basis of a neural network model
Authors: Yang He , Fang Bais. , Reuss Matthias 
Published: March 2009

AbstractA kL a correlation has been developed with the aid of a neural network model. The neural network model has served as a non‐linear relationship performer correlating the volumetric mass transfer coefficient kL a in stirred tank reactors with the operating conditions, reactor geometry and material properties. In order to achieve an optimum correlation, experimental data taken from different sources have been used to train the network. The correlation obtained in this way is able to predict kL a in stirrer tanks reasonably well, if the operating conditions, reactor geometry and material properties fall into the trained ranges. Although the experimental data were widely spread and could only be fitted to individual correlations, the neural network is in a position to give a general correlation for all the data.
Polyethyleneimine‐containing sol‐gels as novel sorbents for the removal of cadmium from aqueous solutions
Authors: Bahrami Shirin , Bassi Amarjeet S. , Yanful Ernest 
Published: March 2009

AbstractThe removal of cadmium ions from aqueous solutions is described using polyethyleneimine (PEI) entrapped in sol‐gel matrices. The process is optimized with respect to operating conditions and both sorption and desorption are considered. The sorption process followed the Langmuir isotherm, and the corresponding Langmuir constants qmax and Kdwere found to be 80.64 mg Cd2+/g PEI and 236.36 mg/L, respectively, using the immobilized PEI polymer. More than 90% of the cadmium could be recovered in 2 h using 2 M NaCl solutions. This technique has potential applications in the recovery of cadmium in aqueous waste streams.