bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stationary State Model in Reforming HCFC22 (CHClF2) to Difluoromethylether (CH3OCHF2)
Authors: Kato Ryo , Nishiumi Hideo 
Published: July 2010

AbstractTo prevent the ozone layer depletion, we proposed a new dechlorination process at room temperature and atmospheric pressure. We have a strong interest in reforming reaction of chlorodifluoromethane (CHClF2, HCFC22) to difluoromethylether (CH3OCHF2), because fluoroethers are expected to be the third generation refrigerants. In a previous paper, we reported that the model that NaCl precipitation, which disturbed mixing of a solution, decreased the reaction rate as the reaction proceeded. In this work, we found that the concentration of HCFC22 was kept constant and smaller than the solubility. The Reaction rate constant k1 was estimated from NaCl production rate and volumetric coefficient KLa was estimated from material balance of HCFC22 in a solution at stationary state. Calculation results gave excellent agreement with experimental data.
Important Factors in Bubble Coalescence Modeling in Stirred Tank Reactors
Authors: Sudiyo Rahman , Virdung Torbjörn , Andersson Bengt 
Published: July 2010

AbstractBubble coalescence has been studied in a 2.6 L stirred tank. Instantaneous velocity fields were measured using PIV and corresponding turbulent kinetic energy, dissipation rate, various length and timescales were estimated. All of these data, combined with data of local gas hold‐up, bubble size and coalescence rate obtained with shadowgraph were used to assess bubble coalescence at different positions. Results show that bubble coalescence takes place mostly near the tank wall, especially on the leeward side of baffles. The most important factors affecting coalescence are gas hold‐up, fluctuation of liquid velocity, different rise velocities of bubbles, and trapping of bubbles in stationary and turbulent eddies.
Parametric Study of a Novel Basket Impeller Column
Authors: Safinski Tomasz , Adesina Adesoji A. , Young Brent R. 
Published: July 2010

AbstractThe Basket Impeller Column combines the mass transfer advantages of a spinning basket reactor with the practicality of a dual flow tray column to achieve controllable liquid holdup, as well as a potential solution to many of the problems plaguing current catalytic distillation internals. Sieve plate design, impeller size and speed, along with water and air, flow rates were explored in order to establish a feasible design. An optimal set of specifications was determined via statistical evaluation. Additional experiments were then conducted to obtain correlations for liquid holdup, gas holdup, froth height, pressure drop and power in terms of the significant hydraulic variables.
On the Numerical Modeling of Gas Absorption into Reactive Liquids in a Laminar Jet Absorber
Authors: Aboudheir Ahmed , Tontiwachwuthikul Paitoon , Chakma Amit , Idem Raphael 
Published: July 2010

AbstractA comprehensive numerically solved absorption‐rate/ kinetics model that takes into account the coupling between chemical equilibrium, mass transfer, and the chemical kinetics of all the possible chemical reactions involved was developed for the absorption of a gas into a reactive liquid. Also, absorption rate measurements to determine the kinetics of the process were obtained in a laminar jet absorber and used to validate this new model. The results show that the model used in conjunction with our numerical method is capable of predicting the gas absorption rates, enhancement factors, and the kinetics of the reaction. Also the model predicted kinetic data for the absorption of CO2 into monoethanolamine (MEA) solutions that were found to be in accordance with published kinetic data. These results show that the developed numerically solved absorption‐rate/kinetics model is both accurate and efficient.
Mass Transfer Characteristics in Gas‐liquid‐liquid System
Authors: Kundu Arunabha , Dumont Eric , Duquenne Anne‐Marie , Delmas Henri 
Published: July 2010

AbstractExperimental results of mass transfer in air‐water system with a dispersed immiscible organic liquid in a bubble column 0.076 m in diameter for seven different organic liquids at various hold‐up are presented. Experiments are carried out at gas superficial velocity in the range 0.0052‐0.026 m/s at 293 K. The volumetric mass transfer coefficient, kLa is determined by dynamic gas absorption technique. Overall gas hold‐up is also measured. Slight addition of n‐decane, dodecane and n‐heptane in air‐water medium significantly enhances mass transfer from the gas phase, to the continuous aqueous phase whereas toluene, anisole and 2‐ethyl‐1‐hexanol retard mass transfer.
Dynamics of Interfacial Mass Transfer in a Gas‐Dispersed System
Authors: Tsuchiya Katsumi , Ishida Toshiki , Saito Takayuki , Kajishima Takeo 
Published: July 2010

AbstractDynamics of mass transfer across gas—liquid interface in a gas‐dispersed system are examined via high‐sensitivity, high‐speed imaging. The dispersive dynamics of the dissolved component, CO2, into the liquid phase are visualized using laser‐induced fluorescence (LIF) with pH‐sensitive pyrene (HPTS) for both a single‐ and multi‐bubble systems. The fluctuating dynamics of the bubble surface are characterized by capillary waves associated with the bubble motion. Enhancement of the mass transfer is found to be associated with the (nonlinear) wave formation, influence of which could be included in modeling the mass‐transfer coefficient, apart from an physical account of the near‐surface concentration gradient.
CFD Simulation of Gas Chamber for Gas Distributor Design
Authors: Dhotre Mahesh T. , Joshi Jyeshtharaj B. 
Published: July 2010

AbstractThe gas chamber is an integral part of various gas‐liquid equipment such as packed columns, plate columns, bubble columns, etc. CFD simulation of the flow pattern was carried out in a gas chamber of square cross‐section and provided with sieve‐plate distributor. Velocities through all the holes were estimated for assessing the uniformity of the gas chamber distribution. The aspect ratio and superficial gas velocity were varied in the range of 0.5 to 4 and 0.02 to 0.2 m/s respectively. The effects of free area and hole diameter were investigated in the range of 0.6 to 6% and 3 to 9 mm respectively. The role of nozzle size and its location with respect to the distributor was analyzed on the uniformity of gas distribution.
Influence of Operating Conditions and Column Configuration on the Performance of Reactive Distillation Columns with Liquid—Liquid Separators
Authors: Klöker Markus , Kenig Eugeny Y. , Schmitt Markus , Althaus Klaus , Schoenmakers Hartmut , Markusse A Peter , Kwant Gerard 
Published: July 2010

AbstractThe synthesis of two different esters, ethyl acetate and hexyl acetate, by heterogeneously catalysed reactive distillation has been studied. The investigated column set‐ups were equipped with liquid—liquid separators for the distillate to separate water from the organic components. Experimental and theoretical investigations of operating conditions and different catalytic column internals, as well as different scales were performed. For the modelling and simulation of the reactive distillation columns, the rate‐based approach was applied. The simulation results are in satisfactory agreement with the experimental data. Performed simulation studies demonstrate the influence of both operating conditions and catalytic internals on the overall process performance.
Autocatalytic Cyclohexane Oxidation in a Bubble Column Reactor
Authors: Schäfer Rainer , Merten Clemens , Eigenberger Gerhart 
Published: July 2010

AbstractThe autocatalytic cyclohexane oxidation was investigated in a lab‐scale bubble column reactor with on‐line measurement of bubble sizes. Significant conversion was obtained at temperatures between 420 and 430 K. The main products were found to be cyclohexyl‐hydroperoxide, cyclohexanol and cyclohexanone. Rising oxygen concentrations favour the production of cyclohexanone. Temperature mainly affects the induction time. At conversion rates greater than 5 % bubble coalescence was inhibited, affecting bubble size distributions for gas hold‐ups above 1 %.
Measurements of Bubble Characteristics: Comparison Between Double Optical Probe and Imaging
Authors: Kiambi S. L. , Duquenne Anne‐Marie , Dupont J.‐B. , Colin C. , Risso F. , Delmas Henri 
Published: July 2010

AbstractThe objective of this study is to evaluate the accuracy of double optical probe technique in local two‐phase flow measurements. Able to provide both bubble velocity, chord length, and gas hold‐up, this technique involves nevertheless delicate signal treatment procedures and, being intrusive, depends on probe tips configurations and sizes. During probe‐bubble interactions, bubble surface is occasionally deformed and this can complicate measurements analysis. The current study is focussed on the rise of single bubbles of known sizes in still water (equivalent diameter of 2.15mm and 4.5mm). Bubble parameters obtained from digital image processing method and from a double optical probe are compared statistically.
A Novel Countercurrent Fixed Bed Reactor
Authors: Kundu Arunabha , Bej Shyamal K. , Nigam K. D. P. 
Published: July 2010

AbstractA new three‐phase reactor configuration having countercurrent flow of gas and liquid is proposed. The reactor had an internal diameter of 0.04 m and a catalyst bed height of 1 m. A spiral coil made out of wire gauge was inserted inside the fixed bed of catalyst. The gas preferentially passed through the void spaces created due to the presence of the coil. Hydrodynamic studies were conducted using water as liquid and air as gas. The effect of various parameters such as the configuration of the spiral coil, flow rate of gas and liquid on the pressure drop and liquid hold up of the catalyst bed were studied and were also compared with that of a conventional trickle bed reactor.
Selectivity, Hydrodynamics and Solvent Effects in a Monolith Cocurrent Downflow Contactor (CDC) Reactor
Authors: Winterbottoma Mike , Marwan Husin , Natividad Reyna 
Published: July 2010

AbstractThe liquid phase hydrogenation of 2‐butyne‐1,4‐diol (B) to cis‐2‐butene‐1,4,‐diol (C) was studied in a Monolith (CDC) Reactor. The effect of temperature, pressure, different solvents and gas and liquid feed rates on reaction rate and selectivity was determined. RTD measurements were made under different hydrodynamic conditions. The liquid flow was largely laminar with evidence of a stagnant wall film. Selectivity to C was observed to increase with hydrogen pressure and approaches 1 at high superficial gas velocities and conversion of B (>95%) as plug flow is approached. The flow regime was of influence on selectivity and kinetics, which was described by a dual site Langmuir‐Hinshelwood mechanism.
Effect of Gas Density on the Hydrodynamics of Bubble Columns and Three‐Phase Fluidized Beds
Authors: Macchi Arturo , Bi Hsiaotao , Grace John R. , McKnight Craig A. , Hackman Larry 
Published: July 2010

AbstractExperiments were performed at ambient temperature and pressure in a 127 mm inner diameter column with a 55% wt. aqueous glycerol solution, 6‐mm spherical borosilicate beads and four gases — helium, air, carbon dioxide and sulphur hexafluoride — giving a 35‐fold gas density range. The dispersed bubble flow regime was sustained to higher gas velocities and gas holdups for denser gases. This finding appears to be due to the reduction of the maximum stable bubble size (i.e. enhanced bubble break‐up), rather than to formation of smaller bubbles at the distributor with increasing gas density. The effect of gas density was significant both with and without the particles present, with gas holdup increasing, bed voidage increasing and liquid holdup decreasing with increasing gas density. The holdup correlations of Han et al. (1990) have been modified to incorporate the effect of gas density.
Prediction of Minimum Fluidization Velocity in Two and Three Phase Inverse Fluidized Beds
Authors: Renganathan Thiruvengadam , Krishnaiah Kamatam 
Published: July 2010

AbstractGeneralized equations for predicting minimum fluidization velocities in two‐phase L‐S and three‐phase G‐L‐S inverse fluidized bed are developed covering a wide range of variables using the experimental data obtained from the present work and that available in the literature. It is found that the classical Wen and Yu equation for predicting minimum fluidization velocity can satisfactorily be used for two‐phase inverse fluidized bed. A model based on empiricism and another based on the gas perturbed liquid model, which reduce to limiting conditions such as liquid solid and three‐phase batch liquid systems are proposed.
CO2 Mineral Sequestration: Chemically Enhanced Aqueous Carbonation of Serpentine
Authors: Park Ah‐Hyung Alissa , Jadhav Raja , Fan Liang‐Shih 
Published: July 2010

AbstractAs one of the greenhouse gases, it is essential to reduce CO2 emissions in order to stabilize CO2 levels in the atmosphere while allowing the continued use of fossil fuels. Abatement of CO2 by mineral carbonation has been proposed as one of the most promising methods for CO2 emission control in the flue gas from coal‐fired power plants. However, little is known about the fundamental characteristics of CO2‐mineral reactions. The overall goal of this study was to investigate the mechanisms of the aqueous reactions of CO2 with Mg‐bearing minerals. Specifically, the focus was on the enhancement of the mineral dissolution.
Modeling the Injection of Gas‐Liquid Jets into Fluidized Beds of Fine Particles
Authors: Ariyapadi Siva , Berruti Franco , Briens Cedric , Griffith Peter , Hulet Craig 
Published: July 2010

AbstractContacting of gas‐liquid jets with particles/ catalyst is essential in many fluidization processes. This paper discusses a momentum conservation model to determine the entrainment rate of solids and gas into a gas‐liquid jet, injected in a fluidized bed. A novel experimental technique developed by Felli (2002) is used to verify the model results. Correction factors to the initial momentum calculated from the homogenous model are addressed. The model predictions are in good agreement with the experimental data. The present model can be used to characterize the behaviour of gas‐liquid jets (fine sprays) injected into fluidized beds of fine particles.
Instability due to Viscosity Stratification Downstream of a Centerline Injector
Authors: Cao Qing , Ventresca Amy L. , Sreenivas K. R. , Prasad Ajay K. 
Published: July 2010

AbstractA common injector geometry upstream of a static mixer is the centerline injector. A flow instability can arise due to viscosity differences between the injected core‐flow and the outer co‐flow. This instability can adversely affect the effectiveness of the mixing operation. An experimental investigation of miscible viscosity‐stratified flow in a circular geometry was performed using Laser Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV). The experimental results for the stable region agree with the analytical results. The unstable region exhibits different modes depending on the viscosity ratio, volume flux ratio, and Reynolds number. The modes include wavy core‐flow with fissures and wavy core‐flow with core breakup. The time‐averaged experiment velocity profiles for the unstable core indicate a broadening of the jet at the centerline, which is consistent with the LIF visualization.
Spray Characteristics of Two‐phase Feed Nozzles
Authors: Ariyapadi Siva , Balachandar Ram , Berruti Franco 
Published: July 2010

AbstractThe present study focuses on understanding the spray characteristics of a turbulent gas‐liquid jet (Reliq = 24,000). Air and water are used as the test fluids. The angles of injection of the two phases upstream of the nozzle are varied (θ = 20°, 45° and 90°) and the effect of carrier gas on the droplet characteristics is are also investigated. The droplet size and velocity are non‐intrusively measured using a Phase‐Doppler Particle Analyzer (PDPA). In some respects, the characteristics of the present two‐phase jet are similar to those noticed in previous studies, while revealing some important differences. The centreline mean droplet velocities (15 ∼ 20 m/s) increase in the initial region of the jet, attain a maximum and then decrease at larger distances from the nozzle exit. Most of the entrainment occurs at the tip of the nozzle and the jet expansion rate decreases significantly at distances where the spray velocity profiles become self‐similar. A Lorentz‐type fit has been used to model the normalized radial velocity profiles. The results indicate that the test configuration with θ = 45° may be beneficial for the scenario discussed.
Hydrodynamic Model for Horizontal Two‐phase Flow Through Porous Media
Authors: Iliuta Ion , Fourar Mostafa , Larachi Faïçal 
Published: July 2010

AbstractA unidirectional, two‐fluid model based on the volume‐average mass and momentum balance equations was developed for the prediction of two‐phase pressure drop and external liquid hold‐up in horizontally positioned packed beds experiencing stratified, annular and dispersed bubble flow regimes. The so‐called slit model drag force closures were used for the stratified and annular flow regimes. In the case of dispersed bubble flow regime, the liquid‐solid interaction force was formulated on the basis of the Kozeny‐Carman equation by taking into account the presence of bubbles in reducing the available volume for the flowing liquid. The gas‐liquid interaction force was evaluated by using the respective solutions of drag coefficient for an isolated bubble in viscous and turbulent flows. The proposed drag force expressions for the different flow patterns occurring in the bed associated with the two‐fluid model resulted in a predictive method requiring no adjustable parameter to describe the hydrodynamics for horizontal two‐phase flow in packed beds.
Further Understanding of the Chemistry of Manganese‐Induced Peroxide Decomposition
Authors: Wekesa Moses , Ni Yonghao 
Published: July 2010

AbstractManganese is the most effective catalyst for the hydrogen peroxide decomposition during peroxide bleaching used in the pulp and paper industry. We studied the chemistry involved in this project. The results showed that Mn2+ and Mn3+ are present during the course of the reaction. We followed the Mn2+ and Mn3+ concentrations during the course. It was found that a steady state of Mn3+ concentration was attained until the hydrogen peroxide concentration was zero. At this time, the Mn3+ concentration was maximum, then it decreased due to the disproportionation to form MnO2. Removal of O2 from the system slowed down the rate of decomposition. The detailed reactions involved were discussed.
Spiral Wound Reverse Osmosis Modules Decomposition into Elementary Units by Analyzing Stimulus Response Experiments: Characterization of the Solute Transfer across the Membrane
Authors: Roth Estelle , Fabre Bernard , Accary Armand 
Published: July 2010

AbstractA model for spiral wound reverse osmosis modules FT30‐4040 has been developed by analyzing stimulus response experiments. Perfect mixing cells represent edthe flow and dispersed plug flow represented the membrane. The model was based on phenomenological equations describing the permeation. The identification of the Peclet number and the space‐time characterizing each dispersed plug flow led to the estimation of the tracer dispersion coefficient in the membrane. Ones new and two used composite reverse osmosis modules were tested. The decrease of the rejection properties of the used membranes was linked to the apparition of new plug flows with high dispersion coefficients within the membrane.
A Rheological Model for the Interface of Immiscible Polymer Melt in Blending Process
Authors: Zhou Chixing , Yu Wei 
Published: July 2010

AbstractWe used an area density tensor as an interface variable of immiscible polymer blend. A phenomenological model for the evolution of such area density tensor in flow fields was established based on the concept of non‐equilibrium thermodynamics of complex polymeric fluids, without the limitations of passive mixing. Phase deformation, break up, relaxation, coalescence effect, as well as non‐affine deformation of the dispersed phase with matrix are all considered in the model. The model predictions show that interfacial slip greatly affects the morphology evolution. The influences of other factors, such as volume fraction, shear rate, interfacial tension, and viscosity ratio, on interfacial area development are also discussed.
Flow Characterization of a Three‐Phase Circulating Fluidized Bed Using an Ultrasonic Technique
Authors: Vatanakull Maytinee , Zheng Ying , Couturier Michel 
Published: July 2010

AbstractThe axial and radial distributions of solid and gas holdups were investigated in an air‐water‐glass bead circulating fluidized bed (GLSCFB) using a new ultrasonic technique, with a new method based on signal fluctuations. The cross‐sectional averaged gas and solid holdups measured at two axial positions appear to be similar at all studied operating conditions. The radial non‐uniformity decreases with increasing liquid velocity but does not change with an increasing solid circulating rate. The radial distribution of gas holdup was more uniform for 1.3 mm beads than for 433 µm glass beads.
Measurement of Turbulent Mixing in a Confined Wake Flow Using Combined PIV and PLIF
Authors: Hjertager Lene K. , Hjertager Bjørn H. , Deen Niels G. , Solberg Tron 
Published: July 2010

AbstractTurbulent mixing in a confined wake flow was studied by using the combined PIV/PLIF technique to measure instantaneous concentration and velocity fields. Measurements were performed at two slightly overlapping areas in the initial mixing zone and at an area at the end of the channel. The measurements revealed that there is a recirculation zone right behind the block that gives an increased mixing effect in this area. The measurement at the end of the channel shows that the concentration distribution is quite uniform, but the two streams are not completely mixed.
Amplification of Periodic Temperature Disturbances in a Packed‐Bed Reactor: CO Oxidation over a CuO/Al2O3 Catalyst
Authors: Na‐Ranong Duangkamol , Jaree Attasak , Hudgins Robert R. , Budman Hector M. , Silveston Peter L. , Menzinger Michael 
Published: July 2010

AbstractAmplification of periodic variations of input temperature in a product‐inhibited reaction — CO oxidation over CuO‐γ‐Al2O3 — was investigated experimentally in an insulated packed‐bed reactor. At steady state the temperature profile was elongated compared with that of a reactant‐inhibited CO oxidation over Pt/Al2O3, studied elsewhere. Under periodic operation, amplitudes of the resulting travelling temperature waves, monitored downstream from the reaction front, were amplified to a greater extent than those in the reactant‐inhibited CO oxidation over Pt/Al2O3. The magnitude of the amplification depended on the perturbation frequency and showed resonance behaviour. The magnitude decreased monotonically with increasing perturbation amplitude.
Experimental Study of Influence of the Impeller Spacing on Flow Behaviour of Double‐Impeller Stirred Tank
Authors: Xueming Shao , Xiaoling Liu , Yulin Li 
Published: July 2010

AbstractThe flow fields in the stirred tank with three different kinds of combined double‐impeller agitators: disc turbine + disc turbine (DT‐DT, radial impeller), pitched blade turbine + pitched blade turbine (PTD‐PTD, axial impeller) and pitched blade turbine + disc turbine (PTD‐DT), were investigated in detail by using laser Doppler anemometry. The two‐dimensional mean velocity field and the distribution of turbulence intensity were obtained for different impeller spacings. The experimental results show that the impeller spacing has a significant influence on the flow field. To improve flow homogeneity and agitator efficiency, the appropriate impeller spacing should be in the range of 1/2 to 2/3 of the tank diameter.