bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increase in the thermal stability during the methanation of CO2 over a Rh catalyst prepared from an amorphous alloy
Authors: Kai T. , Yamasaki Y. , Takahashi T. , Masumoto T. , Kimura H. 
Published: March 2009

AbstractThe hydrogenation of CO2 was investigated over a Rh catalyst prepared from an amorphous Rh20Zr80 alloy. After the reaction, the catalyst was regenerated by oxidation in air and reduction in H2. It was observed that the reaction activity increased with the repetition of regeneration. We also prepared the Rh/ZrO2 catalyst by the conventional impregnation method. The difference in the turnover frequency between the alloy‐precursor catalyst and the conventionally prepared catalyst was small. For the alloy‐precursor catalyst, however, the conversion and CH4 selectivity were stable at 723 K, whereas the conversion and CH4 selectivity decreased with time‐on‐stream even at 673 K for the catalyst prepared by the conventional impregnation method.
Design of stirred vessels with gas entrained from free liquid surface
Authors: Patwardhan Ashwin W. , Joshi Jyeshtharaj B. 
Published: March 2009

AbstractIn this review, the literature on surface aerators is critically analysed. In a number of studies, the critical speed for the onset of surface aeration has been correlated with the geometry of the system and the operating conditions. The studies on the rate of surface aeration, gas hold‐up, mass transfer coefficients are inadequate for the design and scale‐up. A comparison of the available designs, in terms of gas hold‐up, and mass transfer coefficient is presented. A mathematical model has been proposed for surface aeration. Guidelines have been given for the selection of impeller configuration and overall design of surface aerators. Suggestions have been made for future studies in this area.
Solids suspension with up‐pumping pitched‐blade and high‐efficiency impellers
Authors: Myers Kevin J. , Bakker André 
Published: March 2009

AbstractThe use of axial‐flow impellers in the up‐pumping mode has been increasing, but little performance and design information is available. Up‐pumping pitched‐blade and high‐efficiency impellers have been studied in solids suspension applications, and their performance has been compared to and contrasted with that of the more conventional down‐pumping mode. Just‐suspended speed data has been interpreted in terms of two literature correlations that can be used for design purposes. Just‐suspended torque and power requirements are presented, as well as turbulent power number and flow pattern data. In general, the just‐suspended torque and power requirements of up‐pumping pitched‐blade and high‐efficiency impellers are substantially higher than those of the down‐pumping mode. However, if a large impeller diameter is required to avoid critical speed limitations or to achieve sufficient power inputs at high solids loadings, then up‐pumping impellers may be a viable option.
Drop break‐up in intermittent turbulence: Maximum stable and transient sizes of drops
Authors: Baldyga Jerzy , Podgórska Wioletta 
Published: March 2009

AbstractA multifractal method describing the fine‐scale structure of turbulence, including its intermittency, is applied to derive the drop breakage functions for drops whose diameter falls within the inertial subrange of turbulence, including effects of the viscosity of the dispersed phase. The model predicts well the transient drop size distributions of dispersions undergoing breakage at long stirring times. Concepts of quasi‐stable and asymptotically stable drop sizes are presented and discussed in relation to the exponent on the Weber number. The functions for drop break‐up in the viscous subrange are proposed and discussed.
Phase inversion studies in liquid‐liquid dispersions
Authors: Norato Michael A. , Tavlarides Lawrence L. , Tsouris Costas 
Published: March 2009

AbstractA study of the phase inversion behavior of liquid‐liquid dispersions in stirred vessels is performed for liquids of various physical properties at various operating conditions. Physical parameters studied are density (867 to 1180 kg/m3), viscosity (0.00096 to 0.00378 Pa·s), and interfacial tension (0.0089 to 0.0323 N/m). Ambivalence region plots are presented and compared with results reported in the literature. Experiments are performed to examine the effects of impeller type and impeller‐to‐tank diameter ratio (D/T) on the ambivalence behavior. Also, phase inversion time experiments are performed to investigate the time required for complete phase inversion under various dynamic conditions. The traditional method of plotting the organic phase volume fraction at phase inversion against the agitation speed at that condition is compared with the method of plotting the initially dispersed phase volume fraction at phase inversion against the agitation speed at that condition. A hysteresis phenomenon is shown in phase inversion from O/W to W/O and W/O to O/W dispersions. Also, it is shown that, depending on the physical properties of the dispersed and continuous phases, phase inversion may occur when the agitation speed is increased or decreased.
Hydrodynamics of pressurized spouted beds
Authors: He Yan‐Long , Lim Choonj J. , Grace John R. 
Published: March 2009

AbstractExperiments were carried out in a pressurized spouted bed with pressures up to 345 kPa. The minimum spouting velocity was found to decrease with increasing pressure. Comparison of the experimental minimum spouting velocities with the Mathur‐Gishler (1955) equation gave unsatisfactory agreement. The maximum spoutable bed height, Hm, and spout diameters increased with increasing bed pressure. The McNab and Bridgwater (1977) equation consistently overestimated Hm for large or heavy particles and underestimated Hm for small particles, with the deviations between the predicted and experimental values being greater at high bed pressures. Although the McNab (1972) equation gave good predictions of average spout diameters for beds at ambient pressure, it gave poor predictions at elevated pressures, with errors up to 66%. For a given fluid‐solid combination and column geometry the longitudinal pressure profile in the annulus was found to be independent of bed pressure. Five fairly distinct flow regimes were observed, and spoutability could be improved by increasing bed pressure.
Ion exchange equilibria in binary and ternary systems
Authors: Boyer William D. A. , Baird Malcolm H. I. , Nirdosh I. 
Published: March 2009

AbstractSimple mathematical models for binary and ternary ion exchange equilibria were developed to predict selectivity coefficients and resin capacities from a simple experiment to within acceptable engineering accuracy limits. Batch equilibrium experimental investigations were undertaken to test the models for binary systems (Ni‐Na, Cu‐Na, Zn‐Na, Cd‐Na and Pb‐Na) and ternary systems (Ni‐Cu‐Na, Cd‐Ni‐Na, Cd‐Cu‐Na and Pb‐Cu‐Na) with a commercial DOWEX HCR‐W2 resin. Binary parameters were used to predict ternary equilibria. It was found that good agreement between the predicted and experimental values was obtained when the binary selectivity coefficients of the two competing heavy metal ions in the ternary system were either almost equal or differed by a factor as large as five.
Flow development in a gas‐solids downer fluidized bed
Authors: Zhang Hui , Zhu Jing‐Xu , Bergougnou Maurice A. 
Published: March 2009

AbstractThe development of gas and solids flow structure was studied in a 9.5 m high and 0.10 m diameter, gas‐solids cocurrent downflow circulating fluidized bed (downer). Local solids concentration and particle velocity were measured using two separate optical fibre probes at different radial positions on several axial levels along the downer. The results show that the flow development is significantly influenced by the operating conditions. For most of the conditions under which the experiments were conducted, the gas‐solids flow reaches its fully developed zone within 3 to 8 m away from the entrance. On the other hand, the development zone can extend as long as the downer itself, under certain conditions. When the solids circulation rate is over 100 kg/m2s, an increasing solids circulation rate largely extends the length of radial flow development. It is found that the flow developments in the core and at the wall are not quite simultaneous. For solids concentration, the core develops more quickly at low gas velocities and the wall region develops faster at high gas velocities. For particle velocity, higher gas velocity speeds up the development of the wall region but does not significantly affect the development of the core region. The wall region is much more sensitive to the change of superficial gas velocity than the core region. At high superficial gas velocities (> 7 m/s), a “semi‐dead” region is observed in the fully developed zone adjacent to the wall where the dilute solids are moving at a very low velocity.
Effects of the gas/solids distributor on the local and overall solids distribution in a downer reactor
Authors: Lehner Peter , Wirth Karl‐Ernst 
Published: March 2009

AbstractIn the last few years, the downer has been proposed as a new reactor for gas/solids reactions. Compared to state‐of‐the‐art riser reactors, the cocurrent downflow of gas and solids should lead to a more uniform flow structure, close to plug flow. Experimental studies showed, that the gas/solids distributor at the top of the reactor is significantly influencing the flow pattern in a downer reactor. Local information about the solids concentration is indispensable for a thorough characterization of the flow structure in gas/solids flows. To obtain this information, x‐ray computed tomography has been used for the experimental investigations.
The NO and N2O formation mechanism under circulating fluidized bed combustor conditions: From the single particle to the pilot‐scale
Authors: Winter Franz , Löffler Gerhard , Wartha Christian , Hofbauer Hermann , Preto Fernando , Anthony Edward J. 
Published: March 2009

AbstractThe NO and N2O formation mechanism is studied starting from a single fuel particle burning under well‐defined conditions up to a pilot‐scale circulating fluidized bed combustor (CFBC). The fuel, petroleum coke, was the same in all tests and care has been taken to obtain chemical similarity between the different units: a formation rate unit, a laboratory‐scale and a pilot‐scale CFBC. A detailed single particle NO/N2O formation model has been developed and incorporated in a CFBC NO/N2O emission model. To thoroughly test the modeled NO/N2O mechanism, the iodine addition method has been used in all units.
The axial hydrodynamic behavior in a liquid‐solid circulating fluidized bed
Authors: Zheng Ying , Zhu Jing‐Xu , Wen Jianzhang , Martin Steve A. , Bassi Amarjeet S. , Margaritis Argyrios 
Published: March 2009

AbstractBased on experimental results from a 7.6 cm I. D. and 3 m high liquid–solid circulating fluidized bed, the liquid–solid circulating fluidization regime has been separated into two zones: the initial circulating fluidization zone and the fully developed circulating fluidization zone. The distinct hydrodynamic behavior and the influence of particle properties in the two circulating fluidization zones have been studied. The overall flow structure in LSCFB, although still somewhat non–uniform, is much more uniform than that in a gas‐solid CFB. Our experimental results also show that the axial flow characteristics and the regime transition can be strongly affected by the particle density. The stable operation range of the circulating fluidization system and the influences of some associated factors, such as the solids inventory and the particle density, were also investigated for the first time.
Hydrodynamic characteristics of magnetically stabilized fluidized admixture beds of iron and copper particles
Authors: Saxena Satish C. , Wu Wei Y. 
Published: March 2009

AbstractHydrodynamic characteristics of fluidized beds of pure iron (1416 μm), copper (934 μ) and their admixture (25, 50 and 75 mass %) particles when exposed to a uniform magnetic field collinear with the gas flow are investigated. Bed pressure‐drop data taken as a function of increasing and decreasing gas velocities (up to about 8 m/s) for different values of magnetic‐field intensity over a wide range (0 to 17 272 A/m) are employed to determine the superficial minimum bubbling and fluidization gas velocities at ambient temperature and pressure. The minimum bubbling velocity is found to increase with an increase in the value of the magnetic‐field intensity, as well as with the mass fraction of magnetizable particles in the bed. These data are correlated with an empirical relation, as well as with a semi‐theoretical expression. The bed voidage data are also generated and analyzed, as also the bed quality fluidization in terms of interparticle magnetic forces. These hydrodynamic properties of magnetically stabilized fluidized‐bed reactors are useful in their design and operation for a variety of chemical and biochemical applications.
Local measurements for the study of external loop airlift hydrodynamics
Authors: Utiger Marianne , Guy Christophe , Stuber Frank , Duquenne Anne‐Marie , Delmas Henri 
Published: March 2009

AbstractHot‐film anemometry and an optical biprobe are used to measure local flow characteristics in the riser of an external loop airlift reactor. Important flow asymmetries are observed above the sparger and developing flow persists through a large part of the riser. As gas flow rate increases, radial gas hold‐up profiles change from relatively flat to parabolic while the shape of radial liquid velocity profiles remains constant and Sauter bubble diameter increases. At large gas superficial velocities, slip velocity is found to deviate considerably from the frequently used value of 0.25 m/s. Local measurements allow a better understanding of two‐phase flow in airlift reactors and can be used for CFD‐modeling development and validation.
Use of new reaction kinetics for COS formation to achieve reduced sulfur emissions from claus plants
Authors: Karan Kunal , Mehrotra Anil K. , Behie Leo A. 
Published: March 2009

AbstractA simulation study of COS formation in the tubes of the waste heat boiler (WHB) located just after the reaction furnace of a Claus plant is reported. First, the kinetics of the COS forming reaction were obtained from a recently completed experimental program in our laboratory. The predictions for COS formation from the newly developed kinetic model were compared with the data from an actual industrial waste heat boiler and found to be in good agreement. The simulation results showed that up to a 50% reduction in the COS production may be achieved by operating the WHB at the maximum allowable gas mass velocity in the WHB tubes coupled with the use of a smaller diameter tube. These reductions have major implications on the overall sulfur recovery from Claus plants.
Wet oxidation of bleach plant effluent: Effects of pH on the oxidation with or without a Pd/Al2O3 catalyst
Authors: Zhang Qinglin , Chuang Karl T. 
Published: March 2009

AbstractWet oxidation of acidic bleach plant effluent was carried out at 423K and 1.5 MPa in a slurry reactor. The influence of pH of the bleach plant effluent was evaluated for both catalytic and non‐catalytic oxidation in the liquid phase. The stability of the heterogeneous catalysts was investigated by measuring the extent of metal leaching into the solution. The pH of wastewater solution was found to influence significantly both the rate of total organic carbon (TOC) removal and the stability of the Pd/Al2O3 catalyst. Leaching of palladium and alumina occurred mostly at pH 2 and pH 11 under experimental conditions. With Pd/Al2O3, comparable rates of TOC removal were obtained in the pH range of 5 to 9 without significant leaching of both palladium and alumina. No metal leaching was observed using the Pd‐Pt/Al2O3 catalyst at an initial pH value of 7. Implications of these experimental results for designing a catalytic wet oxidation process are discussed. A novel approach has been proposed for the treatment of effluents from softwood Kraft pulp mills.
Estimation of phase velocities at flooding point in packed columns for any gas/liquid system
Authors: Kuźniewska‐lach Irena 
Published: March 2009

AbstractA method for the estimation of gas velocity at the flooding point of various packings, based on such fundamental parameters as the porosity and specific surface of the packing itself, has been developed and introduced herein. The proposed relationships can be applied to the computation of rectification and absorption towers alike, within a wide range of physical/chemical properties of the gas and liquid phases. The method presented in this paper should be particularly useful for estimating the flooding‐point gas velocity of new packing elements, mostly, because it needs no empirical constants to be determined.
Methanol‐based pulping of eucalyptus globulus
Authors: Gilarranz M. A. , Oliet M. , Rodriguez F. , Tijero J. 
Published: March 2009

AbstractThe autocatalyzed pulping of Eucalyptus globulus wood with methanol‐water mixtures was studied. A surface response design was employed to develop mathematical models describing the pulp properties as a function of cooking time, cooking temperature and methanol concentration. The ranges studied for these variables were 40–120 min, 170‐200°C and 30‐70% (w/w), respectively. The pulp properties modeled were kappa number, total yield, screenings content, screened yield and viscosity. Under the optimum cooking conditions pulps with low kappa number and acceptable viscosity can be obtained with a high yield.
Sunflower protein precipitation in a tubular precipitator
Authors: Raphael Matheo , Rohani Sohrab 
Published: March 2009

AbstractIsoelectric precipitation of sunflower protein was carried out in a 20 m long, 6 mm internal diameter glass tubular precipitator. Effects of feed flow rate, protein concentration in the feed stream, and mean residence time on particle size distribution (PSD) were studied. The population balance equation (PBE) for the tubular precipitator was solved using the orthogonal collocation multiple shooting method. A simulated annealing method was used to determine the precipitation kinetic parameters for the nucleation rate, growth rate, aggregation rate, and breakage rate from the experimental data. Due to the lack of experimental data on the kinetics of sunflower protein precipitation in the literature, the extracted kinetics from our experiments were used to evaluate the predictive capability of the present model for experiments whose results had not been used to derive the kinetics. The model predictions of the particle size distribution along the tubular precipitator showed better agreement with the experimental data for large particles in comparison to the small particles (< 10 μm).
Developmental studies of an adaptive on‐line softsensor for biological wastewater treatments
Authors: Jose L. , Sanchez Garcia , Campbell Robinson W. , Budman Hector 
Published: March 2009

AbstractEfficient monitoring and automatic control systems for biological wastewater treatment processes, especially those dealing with bioinhibitory pollutants, such as phenol, are urgently required in order to meet increasingly stringent environmental regulations. Practical on‐line sensors of variables that describe water quality, such as BOD or individual toxic pollutants such as phenol, are not commercially available; e.g. phenol is generally monitored off‐line by spectrofluorometry. Inference software sensors could be an attractive alternative for on‐line monitoring of these variables. As a first step towards the development of inferential sensors for biological wastewater treatment processes, we consider in this study, a simplistic version of such a process which consists of a continuous culture of Pseudomonas putida Q5 degrading phenol. In this work, we propose a neural network based inferential sensor for phenol monitoring using on‐line biomass concentration measurements by spectrophotometry. The network was built with wavelets as the basis functions and the adaptive algorithm for the weights was based on a Lyapunov stability analysis. Predicted phenol output of the network showed good agreement with experimental data, over fairly broad ranges of inlet phenol concentration and dilution rate step changes. Simulations were conducted to find convergence conditions and to investigate possible sources for errors in phenol estimates.
Transfert photonique dans un photoréacteur à écoulement tourbillonnaire
Authors: Pruvost Jérémy , Legrand Jack , Legentilhomme Patrick 
Published: March 2009

AbstractLe transfert photonique est évalué pour deux conditions hydrodynamiques différentes dans un photoréacteur annulare: un écoulement tourbillonnaire non entretenu généré par une entrée tangentielle et un écoulement axial généré par une entrée radiale. Le coefficient de transfert photonique est déterminé graCce à la photoréduction homogène du ferri‐oxalate de potassium. La comparaison des deux types d'écoulement est réalisée pour une solution aqueuse et pour une suspension de noir animal dans un milieu de faible pénétration de la lumière. Cette étude met en évidence l'intérět des écoulements tridimensionnels pour l'augmentation de l'efficacité des photoréacteurs.
The development of a medium for the in vitro expansion of mammalian neural stem cells
Authors: Sen Arindom , Behie Leo A. 
Published: March 2009

AbstractA new medium, PPRF‐m2, has been developed for the in vitro expansion of murine neural stem cells. Neural stem cells (NSC) are primitive cells that have the capability to give rise to all of the cells that comprise the central nervous system (CNS). PPRF‐m2 was developed in part by examining key aspects of a commercial NSC medium used in our laboratory, and includes the basal media combination RPMI/DMEM/F12 in a 1:1:1 volumetric ratio supplemented with a hormone mixture, sodium bicarbonate (21.4 g/L), Hepes (4.3 g/L), glucose (1.75 g/L), glutamine (0.14 g/L), epidermal growth factor (20 μg/L) and basic fibroblast growth factor (10 μg/L). Cells inoculated into PPRF‐m2 effectively doubled 4 times in 5 days to achieve a maximum viable cell density of 1.2 × 106 cells/mL in stationary culture. This was approximately 650% higher than the maximum cell density achieved in the commercial NSC medium. In addition, the PPRF‐m2 cultures were observed to contain less cellular debris, and the cells were less granular and exhibited a lower degree of attachment. Immunocytochemistry revealed that cells grown in PPRF‐m2 retained the ability to generate neurons, astrocytes, and oligodendrocytes.
Mixing of miscible liquids with density differences: Effect of volume and density of the tracer fluid
Authors: Gogate Parag R. , Pandit Aniruddha B. 
Published: March 2009

AbstractThe effect on the mixing time of the density difference between the tracer fluid and the bulk, the type and geometry of the impeller, and the amount of the fluid added as a tracer, has been investigated in a tank with diameter of 0.31 m. The amount of tracer pulse has been varied in the range of 2 to 8% of the bulk volume and the density difference between two fluids has been varied in the range of 54 to 145 kg/m3. A generalized correlation has been developed for the prediction of dimensionless mixing time (Nθ) in terms of amount of the tracer fluid, density differences between the bulk and the tracer liquid and the pumping effectiveness of the impeller. A pitched blade downflow turbine with diameter as small as possible is the most energy efficient among the impellers studied in this work.