bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement and Correlation of Critical Gas and Liquid Velocities for Complete Circulation of Solid Particles in External Loop Airlift Bubble Columns
Authors: Nakao Katsumi , Azakami Fumio , Furumoto Keiji , Yoshimoto Makoto , Fukunaga Kimitoshi 
Published: July 2010

AbstractThe external loop airlift bubble column provides an easy way of good contacting among gas, liquid and solid phases due to a relatively high recirculating liquid velocity UL. The critical gas and liquid velocities for complete circulation of solid particles, UG,C and UL,C, were measured in two different scales of columns with air, tap water and aqueous CMC solutions, and ion exchange resin and glass beads (155∼3834 µm) were employed. The UG,C was determined as the inflection point on the plot of the pressure drop due to the suspended solid particles in the downcomer as a function of the gas velocity UG. The critical liquid velocity UL,C corresponding to the UG,C was obtained from the measured relationship between UL and UG. As a result, a unified dimensionless empirical correlation of UL,C was obtained within an error of ±20% and a dimensionless empirical relationship between UL and UG was developed within an error of ±15%.
2D Slurry Bubble Column Hydrodynamic Phenomena Clarified with a 3D Gas—Liquid Model
Authors: Kluytmans Jeroen H. J. , Van Wachem Berend G. M. , Kuster Ben F. M. , Krishna Rajamani , Schouten Jaap C. 
Published: July 2010

AbstractThe gas hold‐up in a 2D bubble column is modelled using a 3D gas hold‐up model. The influence of the scale of 2D bubble columns on several parameters, for instance, transition gas hold‐up, transition gas velocity, and bubble rise velocities, is investigated and related to 3D bubble columns. By adapting the rise velocity of the large bubbles of an existing 3D bubble column model (Krishna et al., 2001a), the gas hold‐up in both the homogeneous and the heterogeneous regime can be described satisfactorily. By adjusting the transition points only, it is also possible to describe the gas hold‐up in systems containing small amounts of carbon particles and electrolyte. The smallest dimension of the 2D slurry bubble column, the column thickness, influences the location of the regime transition point. In the heterogeneous regime, however, it is only the largest column dimension, the column width, that influences the gas hold‐up. These observations together enable proper 2D/3D bubble column comparison in future studies.
Polysulfide Generation Using MnO2 Catalyzed Oxidation of White Liquor
Authors: Eriksson Johanna C. E. , Bennington Chad P. J. 
Published: July 2010

AbstractThe effect of mixing intensity and oxygen partial pressure on the generation efficiency of polysulfide using the catalytic oxidation of sodium sulfide by manganese dioxide was studied in a high‐intensity batch‐operated reactor. Synthetic white liquor was used in the study. Reaction parameters included the impeller speed (power dissipation), oxygen partial pressure and catalyst type. Increased power dissipation increased the rate, yield and selectivity of polysulfide generation up to an oxygen partial pressure of 230 kPa. Increased oxygen pressure increased the rate of polysulfide formation (to the 0.69 ± 0.12 power) but decreased yield and selectivity. The rate of thiosulfate generation (inferred using a mass balance) exhibited an induction period that was longest at low oxygen partial pressures.
Gas‐Liquid‐Solid Reactions of Polyvinyl Alcohol on Oxidation Treatments for Environmental Pollution Remediation
Authors: Silva Adrián M. T. , Vaz Ricardo N. P. , Quinta‐Ferreira Rosa M. , Levec Janez 
Published: July 2010

AbstractPolyvinyl alcohol (PVA) oxidation in liquid‐phase was studied in a batch high‐pressure reactor at 140 to 240°C and 0.7 MPa oxygen partial pressure. The two‐phase (gas‐liquid) non‐catalytic wet oxidation was compared with a three‐phase system (gas‐liquid‐solid) using CuO‐ZnO/Al2O3 and Mn‐Ce‐O oxides catalysts. This study pointed out oxidation processes as quite promising technologies for industrial effluents containing PVA, leading to high reductions in PVA and total organic carbon (TOC) levels. Catalysts showed high activity at 180°C and carbon adsorption was not observed; Mn‐Ce‐O showed significant leaching to the liquid‐phase, compared with CuO‐ZnO/Al2O3. Acetic and formic acids were detected as refractory compounds for oxidation.
Some Effects of Particle Wettability in Agitated Solid‐Gas‐Liquid Systems: Gas‐Liquid Mass Transfer and the Dispersion of Floating Solids
Authors: Gentile Fabio , Oleschko Holger , Veverka Premek , Machoň Vaclav , Paglianti Alessandro , Bujalski Waldemar , Etchells Arthur W. , Nienow Alvin W. 
Published: July 2010

AbstractTwo‐ and three‐phase systems have been studied using particles that are water‐wetted and denser than water and with similar sized, small floating particles, both wetted and non‐wetted. The parameters investigated have been the agitator speed required to disperse the different types of particles under sparged and non‐sparged conditions and rates of gas‐liquid mass transfer. With the wetted, dense particles, only at concentrations of > ∼20% w/w did the kLa fall significantly (by ∼20 to 30%) whilst solid suspension followed the trends of earlier work. With the less dense particles, even with < ∼1% w/w that were not wetted, it was very difficult to disperse them throughout the liquid phase, though up‐pumping impellers were more effective than radial. In addition, bubble size significantly increased and kLa fell by a factor of 2 to 3. With the wetted, less dense ones up to 2% w/w, uniform dispersion was achieved even at much lower speeds and kLa did not change compared to the case without solids.
Numerical Simulations of an Oscillating Internal‐loop Airlift Reactor
Authors: Oey Ridwan S. , Mudde Robert F. , Van Den Akker Harrie E. A. 
Published: July 2010

AbstractThe Two‐Fluid formulation coupled with a k‐ϵ turbulence model is used for CFD (Computational Fluid Dynamics) analysis of a gas‐liquid flow in an internal‐loop airlift reactor. The studied airlift reactor consist of a riser section interconnected at top and bottom with 2 down‐comer sections. Several flow regimes can be distinguished (Van Benthum et al., 1999), which all have their characteristic features. Flow oscillations have been measured in these type of geometries at certain regimes of the gas flow‐rate. The occurrence of the instabilities showed to be sensitive to the superficial velocity, the free surface height and the location of the inlet. The trend of the predicted dynamical behavior is similar to what was found experimentally: the oscillation period is decreasing with higher gas flow rates.
Effect of Gas Holdup on Current Density Distribution in Horizontal Electrolysis Cell
Authors: Tsuge Hideki , Tozawa Kazuhiro , Muguruma Yukinori , Kawabe Masaki , Abe Masaki , Sagiyama Masaru 
Published: July 2010

AbstractIn the electroplating industry, it is essential to know and control the current density distribution in the electroplating cell. To make clear the behaviour of gas bubbles produced in the horizontal electroplating cell, the effects of the electrolyte velocity and average current density on the current density distribution in the cell were investigated. The increase in overall resistance and the resulting non‐uniformity in current density distribution in the horizontal electrolysis cell were theoretically discussed by modifying Tobias concept derived for the vertical electrolysis cell.
Destruction of Halogenated Plastics in a Molten Salt Oxidation Reactor
Authors: Yang Hee‐Chul , Cho Yong‐Jun , Yun Jong‐Sung , Kim Joon‐Hyung 
Published: July 2010

AbstractHalogenated plastics such as PVC pipe, PTFE tube, and latex gloves were test‐burned in a bench‐scale molten salt oxidation reactor. Hydrogen halides (HCl and HF) and free halogens (Cl2 and F2) first released by the thermal decomposition of halogenated plastics (PVC and PTFE) were nearly completely collected in the hot sodium carbonate salt bath. Compared to halogen collection, sulfur collection was not complete and SO2 emission for rubber gloves decreased with stoichiometric air ratio. The entrainment of spiked metals and their fraction in the sub‐micron particle size range increased with the chlorine content as well as the operating temperature.
Combined PIV/PTV‐Measurements for the Analysis of Bubble Interactions and Coalescence in a Turbulent Flow
Authors: Bröder Dirk , Sommerfeld Martin 
Published: July 2010

AbstractIn order to allow more reliable modeling of coalescence processes in turbulent bubbly flows, detailed experiments in a double loop reactor were performed. Narrow and essentially monomodal bubble size distributions in the range of 2 to 4 mm were created. For simultaneous measurements of bubble size, bubble velocity and liquid velocity a combined system of PIV and PTV was developed and applied. It was possible to determine bubble size distributions and mean, as well as fluctuating velocities for both phases. The spatial changes of the bubble size distribution, due to the influence of bubble coalescence, was analyzed and coalescence rates were calculated.
The Influence of Periodic Operation on the Effective Radial Thermal Conductivity in Trickle Bed Reactors
Authors: Borremans Didier , Rode Sabine , Carré Patrick , Wild Gabriel 
Published: July 2010

AbstractThe effect of a periodic liquid feed on the effective radial heat conductivity, Λr, in a trickle bed was investigated. The mean Λr under periodic operation was found to be well estimated by time‐weighed averaging of steady state values. The actual effect of periodic operation can therefore be predicted by the shape of the Λr, uL — curve in steady state operation. The effect of periodic operation is attenuated with decreasing gas flow rates and with decreasing liquid flow rate amplitudes in a bed of spherical particles. Practically no effect was observed with cylindrical particles.
On the Influence of Liquid Distribution on Heat Transfer Parameters in Trickle Bed Systems
Authors: Mariani Néstor J. , Mazza Germán D. , Martínez Osvaldo M. , Cukierman Ana L. , Barreto Guillermo F. 
Published: July 2010

AbstractThe aim of this work is to analyse experimental results on radial heat transfer in a packed bed column with cocurrent downflow of liquid and gas, focused on the influence of radial liquid distribution and column to particle diameter ratio. For this purpose, two kinds of measurements were carried out: radial liquid distribution and radial temperature profiles. Heat transfer data as analysed with a model consisting of two regions: a lumped wall region up to a distance of a particle radius from the tube wall, and a distributed core region covering the rest of the bed. Three parameters arose: the radial effective thermal conductivity of the core region (ker,c), the heat transfer coefficient between both zones (hI), and the heat transfer coefficient from the wall region to the tube wall (hw,w). Suitable correlations for the mentioned parameters as a function of gas and liquid Reynolds number and particle diameter were developed.
Mechanism of Local Fluidization in Converging Packed Beds
Authors: Zhang Baoquan , Liu Xiufeng , Zhu Huiming 
Published: July 2010

AbstractThe velocity profile on the bed surface of two‐dimensional linear‐converging beds with 15° and 30° wall angles was measured at different superficial velocities using hot‐wire anemometry. The results of the velocity measurements indicate that local fluidization in the corners is caused by the geometry‐induced maldistribution of fluid flow, and it occurs when the velocity in the corners exceeds the minimum fluidization velocity of particles. The results of pressure measurements within the bed show the same trend as the velocity profile, providing a qualitative verification of the velocity profile measurement. It is shown that the variation of measured pressure drop over the bed with velocity does not agree with the Ergun equation at high superficial velocities due to the severe maldistribution of fluid flow.
Optimal Design and Optimal Operation of Separate Heat Pump Distillation
Authors: Zhu Ping , Feng Xiao 
Published: July 2010

AbstractFor a distillation system, in which relative volatility is large in low composition range and small in high composition range, using separate heat pump distillation (SHPD) can markedly save energy. In this paper, vapour flow rate to compressor is proposed as a parameter for system optimization, from the viewpoint of system energy balance. This parameter can be used for both optimal design and optimal operation of SHPD. Mathematical models for optimal design and optimal operation are formulated to minimize total annual cost and annual operating cost respectively. Optimal design of SHPD is performed and evaluated through process simulation, for a typical case study for the distillation of ethanol‐water system. The results show that SHPD has notable energy saving and economic benefit when compared with conventional distillation. Optimal operation of SHPD is also evaluated for changes in feed composition which is an operating variable.
Mechanistic Modelling of the Catalytic Pyrolysis of Methylcyclohexane
Authors: Singh Om. V. , Pant K. K. 
Published: July 2010

AbstractA detailed chemical kinetic mechanism describing the thermal and catalytic cracking of methylcyclohexane over a 12CaO.7Al2O3 catalyst is presented. The model is based on balanced equations for both molecular and radical species describing an experimental fixed‐bed reactor system. The mechanistic model is based on overall first‐order decomposition kinetics, which satisfactorily describes experimental data. The simulated product distributions show a reasonably good agreement with the experimental results and confirm the hypothesis that the catalyst does not affect the pyrolysis mechanism and only increases the rate of the initiation steps.
Modelling and Control of an Industrial Multiple‐Effect Evaporator System
Authors: Costa Andréa O. S. , Lima Enrique L. 
Published: July 2010

AbstractA study has been conducted of the modeling and control of an industrial multiple‐effect evaporator system used for black liquor recovery. The developed model is a combination of phenomenological and empirical (neural networks) approaches, based on industrial data. An advanced model‐predictive control strategy, allowing for manipulated variable constraints, compares favorably with a classical PID‐based scheme.
Studies on the Effects of Certain Non‐dimensional Groups on Dynamic Simultaneous Adsorption Behaviour of Carbon Dioxide and Moisture in Molecular Sieve, 5A
Authors: Ghoshal Aloke K. , Samanta Amar N. , Maiti Binoy R. 
Published: July 2010

AbstractA non‐isothermal model based on linear driving force approximation for a system like CO2 – moisture – N2 – molecular sieve, 5A predicted the experimental results satisfactorily for simultaneous adsorption of CO2 and moisture in a fixed bed. Moisture being the strongly adsorbed component forces carbon dioxide (weakly adsorbed component) to be rolled up. The thermophysical and transport properties of moisture mainly governs the dynamics of the process, control or manipulation of which could give better separation by adsorption of one component from the other lying together in a stream. The major parameters are inlet adsorbate concentration, particle Reynolds number, bed diameter to bed length ratio, Schmidt number, Equilibrium Distribution coefficient, Sherwood number, and Kutateladze number.
Local Bubble Dynamics and Macroscopic Flow Structure in Bubble Columns with Different Scales
Authors: Chen Wei , Tsutsumi Atsushi , Otawara Kentaro , Shigaki Yoshiki 
Published: July 2010

AbstractLocal bubble behaviours were investigated in three bubble columns with different diameters of 200, 400 and 800 mm. By means of a novel single‐tip optical fibre probe employing laser Doppler technique, the local gas holdup, bubble frequency, bubble size and velocity were measured simultaneously at different locations of the columns. Measurements were performed in air‐water system at superficial gas velocities up to 90 mm/s. The averaged profiles and instantaneous measurements were analyzed and compared for different columns. The presence of a coherent gross circulation structure spanning the entire column diameter in the larger column rather than a pair of symmetrical circulation cells observed in the smaller columns has been confirmed.
Experimental Studies on Hydration of Partially Sulphated CFBC Ash
Authors: Wu Yinghai , Anthony Edward J. , Jia Lufei 
Published: July 2010

AbstractThe hydration of partially‐sulphated fluidized bed combustor (FBC) ash with water was carried out at laboratory scale. The bottom ash fractions and the as‐received fly ash were hydrated for different lengths of time, at different temperatures between 5°C and 80°C. The free lime and calcium hydroxide content in the samples were analyzed before and after the hydration process. Scanning electron microscopy (SEM) with an energy dispersive X‐ray system (EDX) was employed to investigate the physical characteristics of the samples. X‐ray diffractograms (XRD) were used to obtain information on the phase composition. The current results show that, during the hydration treatment, the unreacted CaO in the partially‐sulphated material can be almost quantitatively converted to Ca(OH)2 but that the free lime content is not constant. It is also clear that effectiveness of the hydration depends on hydration time and temperature. In addition, the behaviour of different particle size fractions is different and there is evidence that the hydration of CaO is not the only reaction occurring in this system.
Régimes d'écoulement et mesure de l'épaisseur d'un film liquide ruisselant autour d'un tube horizontal
Authors: Louahlia‐Gualous Hasna , Baonga Jean Bosco , Panday Prabodh Kumar 
Published: July 2010

AbstractCet article présente les résultats d'une étude expérimentale sur la structure de l'écoulement et sur la mesure de l'épaisseur d'un film liquide ruisselant autour d'un tube horizontal. Il décrit la technique utilisée pour mesurer l'épaisseur du film en se basant sur la méthode de fluorescence induite par laser. Les essais ont été effectués avec le mélange eau/fluorescéine à une température constante et à la pression atmosphérique. En faisant varier le débit d'écoulement, plusieurs régimes d'écoulement sont identifiés. Nous avons mesuré la longueur d'onde en fonction du nombre de Reynolds du film. Les transitions entre les différents régimes d'écoulement sont étudiées en mettant en évidence le phénoméne d'hystérésis. Les valeurs des longueurs d'onde adimensionnelles sont comparées aux résultats de Hu et Jacobi (1998). Les résultats obtenus montrent l'évolution locale de l'épaisseur du film autour du cylindre. Ils sont comparés aux résultats de Rogers et Goindi (1989), Rogers (1986) et de Chyu et Bergles (1987). Une expression de l'évolution locale de l'épaisseur du film liquide est proposée en se basant sur les résultats des mesures.
Evolution of the Population of Bubbles in 2D Fluidized Beds
Authors: Prieto Juan J. , García Mónica , Ramos Guadalupe , Guardiola Jesús 
Published: July 2010

AbstractThe size of the bubbles in a solid‐gas 2D fluidized bed was estimated by image capture and digitalization using a CCD camera. It was confirmed that the size distribution for the bubbles in a slice of the bed was skewed, varying with the location of the slice. The results were analyzed using the Agarwal (1985) model, which is based on a population balance. For this model, four adjustable parameters are required, as well as the knowledge of bubble size just above the distributor. Experimental data were compared with values predicted by the model. The parameters that the model needs were obtained by three procedures: i) the constants supplied by Agarwal (1985) and Rowe and Everett (1972); ii) the parameters obtained from experimental data for a 1 cm wide slice bed; and iii) the parameters obtained by fitting the bubble diameter to all the bubbles in the bed. The second and third methods provided the best results.
Determination of Minimum Spouting Velocities in Conical Spouted Beds
Authors: Wang Zhiguo , Bi Hsiaotao T. , Lim C Jim , Su Pengcheng 
Published: July 2010

AbstractMinimum spouting velocities in conical spouted beds have been obtained from pressure drops versus the superficial gas velocity curves, based on both increasing and decreasing the superficial gas velocity. It has been shown that the minimum spouting velocity from decreasing the superficial gas velocity is lower than from increasing the superficial gas velocity in most cases. This phenomenon is similar to that in conventional spouted beds and different from the early works. The experimental results also showed that there isn't significant difference in the pressure drop and Ums under identical operating conditions between semi‐circular and circular conical spouted beds, and the same Ums can be obtained from absolute pressure drops at any position above the gas inlet. The Ums is found to increase with increasing the cone angle and static bed height, as well as the gas inlet diameter to a less extent.
Characterization of Gas Spouted Beds Using the Rescaled Range Analysis
Authors: Xu Jian , Bao Xiaojun , Wei Weisheng , Shen Shikong , Bi H. T. , Grace J. R. , Lim C. J. 
Published: July 2010

AbstractDifferential pressure fluctuation measurements were conducted in a gas spouted bed of 120 mm in diameter at different axial and radial positions. Hurst's rescaled range analysis of the differential pressure fluctuation signals was successfully employed to recognize different flow regimes, i.e. packed bed, stable spouting and unstable spouting, and characterize their transitions. Obvious two‐phase behaviour, as suggested by two Hurst exponents, was observed in the stable spouting regime. It had also been found that the spouting behaviour in deeper spouted beds was significantly different from that in shallow spouted beds. The influences of measurement location and bed height on the Hurst exponents were discussed.
Voidage Profiles in a Slot‐Rectangular Spouted Bed
Authors: Freitas Luiz A. P. , Mitsutani Kenji , Lim C Jim , Grace John R. , Wei Weisheng 
Published: July 2010

AbstractLocal voidages were determined using optical fibre probes for 1.4 and 2.4 mm glass beads in slot‐rectangular spouted beds of width 150 mm. The effects of air inlet flow rate, slot width and bed thickness were investigated. Spout widths were determined from standard deviations of local voidage fluctuations. Both spout and annulus voidages increased with increasing air flow. Annulus voidages were usually higher than corresponding loose‐packed voidages and decreased with increasing height. Annulus and spout voidages were very sensitive to the air entry slot width and particle diameter. With increasing height, spouts became increasingly circular (three‐dimensional), despite the initial rectangular geometry.
Behaviour of Cohesive Powders in a Powder‐Particle Spouted Bed
Authors: Ishikura Toshifumi , Nagashima Hiroshi , Ide Mitsuharu 
Published: July 2010

AbstractBehaviour of cohesive powders in a powder‐particle spouted Bed (PPSB) has been investigated under several operating variables and solids properties. The elutriation rate constant based on the hold‐up of fine powders in the bed decreased with a decrease in the size of fine powders, and with an increase in the size of coarse particles under a constant superficial gas velocity. This finding is quite different from the elutriation phenomena of particles more than 100 µm in size. Moreover, the mean residence time of fine powders increased with a decrease in the superficial gas velocity and the size of fine powders, and decreased with a decrease in the size of coarse particles.