bluuebunny/crossref_metadata_2025 huggingface dataset:
ChemInform Abstract: Extra‐Large‐Pore Zeolites: Bridging the Gap Between Micro and Mesoporous Structures
Authors: Jiang Jiuxing , Yu Jihong , Corma Avelino
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Allosteric Ligands for G Protein‐Coupled Receptors: A Novel Strategy with Attractive Therapeutic Opportunities
Authors: De Amici Marco , Dallanoce Clelia , Holzgrabe Ulrike , Traenkle Christian , Mohr Klaus
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis of Substituted Phthalocyanines
Authors: Nemykin Victor N. , Lukyanets Evgeny A.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Heteroatoms Moving Protons: Synthetic and Mechanistic Studies of Bifunctional Organometallic Catalysis
Authors: Grotjahn Douglas B.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Metallothioneins: Unparalleled Diversity in Structures and Functions for Metal Ion Homeostasis and More
Authors: Blindauer Claudia A. , Leszczyszyn Oksana I.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Copper Mining in Streptomyces: Enzymes, Natural Products and Development
Authors: Worrall Jonathan A. R. , Vijgenboom Erik
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Nanoparticle‐Based Biologic Mimetics
Authors: Cliffel David E. , Turner Brian N. , Huffman Brian J.
Published: July 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Fluidization characteristics of printed circuit board plastic particles with different sizes
Authors: Guo Qingjie , Liu Yongzhuo , Wang Minghua
Published: July 2010

The experiments were carried out in a fluidized bed of 56 mm in diameter and 1 600 mm in height to determine the fluidization characteristics of four sizes of printed circuit board plastic (PCBP) particles. It indicates that the fluidization characteristics of PCBP particles depend on the average size and particle type. 123 µm PCBP particles (1#), belonging to Geldart A group with strong viscous force, whose fluidization behaviours was similar to those of Geldart C, was difficult to fluidize. Whereas, 275 µm (2#), 354 µm (3#), and 423 µm (4#) PCBP particles, belonging to Geldart B, were fluidized smoothly. The bed collapsing process is composed of three stages: the bubble escaping stage, the sedimentation stage, and the solid consolidation stage. The collapsing process of 1# PCBP particle lasts 6 s or long. 2#, 3#, and 4# PCBP particles, Geldart group B particles, collapse process consists of the bubble escaping stage and the solid consolidation stage. The minimum fluidization velocities from modified Ergun Equation were agreement with experimental data for 2#, 3#, and 4# PCBP particles.
Optimum design of integrated liquid recovery plants by variable population size genetic algorithm
Authors: Mehrpooya Mehdi , Vatani Ali , Mousavian S. M. Ali
Published: July 2010

Increase in the price of energy sources as well as economic problems have caused cryogenic natural gas plants to become more complex and efficient. After selecting the process configuration, the flow rate, pressure, and temperature of the process fluid streams are determining factors which should be tuned in order to find the optimum condition. Products specification and operating costs of the plant are two significant parameters which should be considered in an optimal design. Moreover, process design limitations contribute to the problem being more difficult. This paper shows how the optimal operating point in an integrated NGL recovery plant can be found through solving a complex constrained optimization problem. A Variable Population size Genetic Algorithm (VPGA) was used for optimization. As well, the role of VPGA algorithm parameters in solving the process design problems is investigated in this study. The analysis showed that the VPGA method has better performance compared to the general GA methods. The plant‐wide net profit increases 12493360 $/year only by changing the selected operating conditions to its optimal value.
Absorption of co2 into aqueous tertiary amine/mea solutions
Authors: Rangwala H. A. , Morrell B. R. , Mather A. E. , Otto F. D.
Published: July 2010

Absorption rates for CO2 into aqueous solutions of TEA, MDEA and blends of MEA with MDEA and TEA were measured in a stirred cell by a method similar to that used by Laddha and Danckwerts (1981). Second order rate constants for CO2‐TEA and CO2‐MDEA were obtained from the single amine data for temperatures in the range of 25‐60°C.

A modified pseudo first order model based on the film theory is used to predict the rate of absorption of CO2 into mixed amine solutions. This model accounts for the variation of amine concentration in the film and assumes a shuttle mechanism for rate enhancement. Bulk liquid concentrations of the various species present are obtained from a simplified thermodynamic model. The model predicts absorption rates that are in agreement with experimental measurements.
Application of a bayesian regression method to the estimation of diffusivity in hydrophilic gels
Authors: Anderson William A. , Reilly Park M. , Moo‐Young Murry , Legge Raymond L.
Published: July 2010

Knowledge of intraparticle reactant and product diffusivities is important for catalytic reaction engineering purposes, including systems where enzymes or microbial cells are entrapped within hydrophilic gel particles. In this work, a Bayesian regression method was applied to estimate diffusivities from dynamic solute uptake experimental data. This method accounted for non‐uniformity in the particle sizes. Typically, diffusivities are experimentally determined for these gel matrices by monitoring the dynamic uptake of a solute into several hundred small particles. The diffusivity is then estimated using a mathematical approach based on a single particle case. This approach is only appropriate when variations in radius are small. The Bayesian regression technique was found to be suitable for accounting for the nonlinear effect of radius distribution on diffusivity estimates. It was also possible by this method, to incorporate experimental data for partition coefficients, so that appropriate confidence limits on the diffusivity estimate could be obtained.
Numerical simulation of short‐dwell coaters: Steady state flow patterns and pressure distributions
Authors: Cao Zhenlei , Esmail M. Nabil
Published: July 2010

The steady state flow in a short‐dwell coater has been simulated by solving the two‐dimensional Navier‐Stokes equations in the primary pressure and velocity variables for substrate Reynolds numbers up to 1000. The small opening under the blade has very little effect on the flow patterns in the coating pond. However, it does have a significant effect on the pressure field in the pond. The pressure on the substrate surface, which controls liquid penetration during application, has a maximum value under the blade, near its tip. Low coating weights and high coating speeds lead to higher maximum pressure on the substrate. The operating pressure which must be applied to the blade can be predicted for a given coating weight and substrate velocity. For high substrate speeds and low coating weights, higher operating pressures are needed to keep the blade in position.
The maximum‐power test for gross errors in the original constraints in data reconciliation
Authors: Crowe Cameron M.
Published: July 2010

The detection of gross errors in the reconciliation of process measurement data is an important step in removing their distorting effects on the corrected data. Tests of maximum power (MP), based on the normal distribution, are known for the detection of gross errors in the measurements and for the constraints, but only for those remaining after the removal of unmeasured flows. Here, the MP tests are derived for the original constraints, which allows the direct detection of gross errors in species balances around individual process units. It is shown that the square of the MP test statistic is precisely equal to the reduction in the weighted sum of squares of the adjustments which results from the deletion of that constraint. The test is illustrated with two examples.
Prediction of Gas‐Phase Adsorption Isotherms Using Neural Nets
Authors: Basu Sukanta , Henshaw Paul F. , Biswas Nihar , Kwan Hon K.
Published: July 2010

This study investigated a number of models (the modified Sips', Dubinin‐Astakhov's, VSM theory, the generalized Khan et al.'s model and a simple artificial neural network (ANN)) to predict the effect of temperature on equilibrium adsorption of hydrocarbon gases and vapors on activated carbon. Published data on the adsorption of methane, ethane and propane on activated carbon at 311 K to 505 K were used to estimate the parameters of the conventional models and train the network. Then, the conventional models and the ANN were used to predict the isotherm at a single temperature for each adsorbate, and these results were compared with experimental data. It was found that the ANN model had a lower mean relative error than the conventional models.
CFD Simulations of Three‐dimensional Wall Jets in a Stirred Tank
Authors: Bhattacharya Sujit , Kresta Suzanne M.
Published: July 2010

The flow near the tank wall in a stirred tank driven by a 45° pitched‐blade turbine is simulated with Multiple Reference Frames, the k‐e turbulence model and standard wall functions. The results are compared to the three‐dimensional wall jet identified in a previous paper. The self‐similar velocity profiles in the jet are predicted satisfactorily, but the decay of the local maximum velocity and jet expansion are underpredicted. The underlying physical reasons for this failure are investigated. The effect of impeller size and position on the impingement point of the impeller discharge and the jet core velocity are well predicted by the simulations. The results provide a benchmark for CFD/MRF in the bulk of a stirred tank, identifying where CFD over‐ or underpredicts performance.
Simple Model to Evaluate Loading/Flooding Transition in Aerated Vessels Stirred by Rushton Disc Turbines
Authors: Paglianti Alessandro
Published: July 2010

Prediction of the flooding/loading transition in an aerated stirred tank is crucial for the correct design of aerated stirred tank reactors. Despite the importance of this problem, only semiempirical equations are available at the moment. This work provides a simple mechanistic model for predicting the flooding/ loading transition in stirred tank reactors equipped with Rushton turbines. This model could be a useful one, since it allows the user to scale‐up agitated vessels easily. It has only been tested for Rushton turbines, but because the model is based simply on mass balances, energy balances and continuity equations, it could also be used with other impellers after a few modifications.
Critical Impeller Speed for Suspending Solids in Aerated Agitation Tanks
Authors: Zhu Yonggang , Wu Jie
Published: July 2010

Systematic measurements have been carried out in agitated gas‐liquid‐solids systems to determine the just off‐bottom suspension speed. A variety of solids sizes, solids concentrations, impeller sizes and tank sizes are used. The difference between the just off‐bottom suspension speeds with and without gas sparging does not show a linear relationship with the gassing rate and the relation is system‐dependent. The relative just off‐bottom suspension speed RJSS = Njsg / Njs is found to be dependent only on the just suspension aeration number Najs = Qg / NjsD3 and, for DT6 impellers, the relation is RJSS = 1 + mNanjs with the values of 2.6 and 0.7 for m and n, respectively. The relation is independent of the impeller size, solids size, solids loading and tank size, and can be used to scale up laboratory data to full‐scale mixing vessels. Data from different studies support the present findings.
Power Consumption in the Turbulent Regime for a Coaxial Mixer
Authors: Tanguy Philippe A. , Thibault Francis
Published: July 2010

The power consumption of a new coaxial mixer composed of an anchor impeller and a pitched‐blade turbine impeller, and a series of rods operated in a contra‐rotating mode has been characterized experimentally in the turbulent regime. It is shown that both the power curve and the turbulent power number vary significantly with the speed ratio between the impellers. Likewise with single impeller mixers, the transition regime starts at a Reynolds number above 100 and the turbulent regime between 103 and 104 irrespective of the definition of the Reynolds number used.
Morphology Development in Kenics Static Mixers (Application of the Extended Mapping Method)
Authors: Galaktionov Oleksiy S. , Anderson Patrick D. , Peters Gerrit W. M. , Meijer Han E. H.
Published: July 2010

This paper addresses the interfacial area generation in Kenics static mixers using a new method. A statistical description of the microstructure development is obtained using the extended mapping method, which is restricted to systems with negligible interfacial tension. However, the layered structures created in a Kenics are a good example where interfacial tension does not play an important role (the layered structure is retained). The extended mapping method is adopted to the special flow conditions in spatially periodic flows. The efficiency of the interface generation for different mixer layouts is compared and additional attention is given to the distribution of the interfacial area across the mixer. It is shown that the extended mapping method enables us to find the blade configuration that optimizes the mixing performance, in accordance to the standard mapping method, but now including much more details concerning the microstructure development in this chaotic flow.
Pressure Drop and Mass Transfer Study in Static Mixers with Gas Continuous Phase
Authors: Couvert Annabelle , Péculier Marie‐France , Laplanche Alain
Published: July 2010

The aim of this work was to characterize both the influence of the gas and the liquid flow rates on the pressure drop generated by static mixers type Sülzer, and on the mass transfer performances of these gas‐liquid contactors. The originality of this work rests on the use of the static mixers with a gas continuous phase. Several configurations were studied: vertical upward flow, vertical downward flow, and horizontal positions, with one to five mixing elements. It was concluded that the pressure drop is mainly generated by the gas phase, whatever the configuration chosen. Moreover, the volumetric mass transfer coefficients kLa found were lower than those obtained with the same static mixers used in classic conditions (that is with a liquid continuous phase), but greater than values obtained with classic reactors like bubble columns or packed columns. The efficiency of these gas‐liquid reactors was found high, as well as the energy dissipated, unfortunately.
Gas—Liquid Mass Transfer Coefficient in Stirred Tank Reactors
Authors: Yawalkar Archis A. , Heesink Albertus B. M. , Versteeg Geert F. , Pangarkar Vishwas G.
Published: July 2010

Volumetric gas—liquid mass transfer coefficient (kLa) data available in the literature for larger tanks (T = 0.39 m to 2.7 m) have been analyzed on the basis of relative dispersion parameter, N/Ncd. It was observed that at a given superficial gas velocity (VG), kLa values were approximately the same irrespective of geometric configuration (size of the tank, type and size of the impellers, type of the sparger, etc.) at a particular N/Ncd. A single correlation based on N/Ncd is presented which shows satisfactory agreement with the kLa data of different workers.
Preparation and Kinetic Considerations for the Dissolution of Cr‐substituted Iron Oxides in Reductive‐complexing Formulations
Authors: Manjanna Jayappa , Venkateswaran Gopala
Published: July 2010

The dissolution rate coefficients of Cr‐substituted (0‐20 at.% Cr) iron oxides viz. hematite and magnetite were determined by using an inverse cubic rate (ICR) law applicable for spherical particles as well as by a general kinetic equation (GKE) applicable for polydispersed particles. An attempt is made to compare both the treatments for different kinds of dissolution profiles obtained by employing oxides with narrow particle size distribution in V(II)‐EDTA and citric acid‐EDTA‐ascorbic acid formulations at 353±5K. The dissolution profiles could be classified into three types based on the nature of oxide and formulations. It is observed that both ICR and GKE treat the dissolution course as a function of decrease in fraction of undissolved mass, m/m0. The dissolution rate coefficients determined by ICR and GKE have shown the similar trend of decrease with increasing Cr content of the oxides and was ascribed to lattice stabilization.
Prediction of High‐Pressure Phase Equilibria using Cubic EOS: What Can Be Learned?
Authors: Polishuk Ilya , Stateva Roumiana P. , Wisniak Jaime , Segura Hugo
Published: July 2010

Modern semi‐empirical cubic EOSs are usually attached by complex functionalities, such as Huron‐Vidal (HV)‐type mixing rules. Although this practice improves the flexibility of the models, it also complicates consideration of an overall picture of phase behavior. As a result, GE‐based equations are usually adjusted to the experimental data by way of a local fit. The latter approach tends to ignore that different regions of the thermodynamic phase space are closely inter‐related. The present study demonstrates that the contribution of (HV)‐type mixing rules to predicting high‐pressure phase equilibria can be quite modest and that in addition they may generate non‐realistic phase diagrams.
Predicting the Distribution Constants of Butane Extraction of Organic Pollutants from Aqueous Solubility
Authors: Teo Khay‐Chuan , Yang Chun , Xu Yan‐Rong
Published: July 2010

The n‐butane/water distribution constant is one of the key parameters in determining the extraction efficiency. Experimental results on 34 organic compounds illustrated that a fundamental linear relationship exists between the distribution constant and the aqueous solubility of the solute. The relationship can be broadly applied to many different classes of chemical compounds as well as to many different solvent extraction systems. The linear equation obtained by a regression method allows one to estimate the distribution constant and predict the result of butane extraction if the aqueous solubility of certain solute is available.
Integrated Scheme of Natural Gas Usage with Minimum Production of Entropy
Authors: Granovskii Michael S. , Safonov Mikhail S. , Pozharskii Sergey B.
Published: July 2010

Three schemes of the gas turbine cycle have been analyzed from the point of view of the second law of thermodynamics: the conventional gas turbine cycle, where natural gas (methane) is oxidized by air; a closed gas turbine cycle, in which methane is oxidized by oxygen; and a proposed gas turbine cycle, in which the methane is first converted to synthesis gas (a mixture of carbon oxide and hydrogen), then part of the synthesis gas is oxidized by oxygen for electric energy generation while the rest is withdrawn from the power cycle for production of methanol, ether, synthetic fuel, etc. It has been shown that the third integrated scheme of natural gas usage provides minimum entropy increase as well as suppression of toxic nitrogen oxides generation in combustion products. Therefore, it could be considered as a prospective energy‐saving technology.
Linear Viscoelastic Properties of Suspensions of Rigid Hairy Particles in a Polymeric Matrix
Authors: Dagréou Sylvie , Kasseh Abdeslam , Allal Ahmed , Marin Gérard , Aït‐Kadi Abdellatif
Published: July 2010

The aim of this work is to use a recently developed statistical model of dispersions with non‐hydrodynamic interactions (Dagréou et al., 2002) to describe the linear viscoelastic properties of suspensions of rigid hairy particles in a polymeric matrix. We first present numerical simulations of our model applied to this system; we demonstrate that taking physical interactions into account allows one to predict the complex relaxation behaviour of filled polymers. We then compare the statistical model to experimental results on suspensions of grafted silica particles in a polystyrene matrix and show that they are in reasonable agreement up to volume fractions close to percolation.
Molecular Weight Polydispersity Effects on Diffusion at Polymer/Polymer Interfaces
Authors: Qiu Hua , Bousmina Mosto
Published: July 2010

The effect of molecular weight distribution (MWD) on diffusion at symmetric polymer/polymer interfaces is investigated by rheological tools. A new model allowing the determination of a self‐diffusion coefficient of polydisperse polymer systems is presented. The model is based on the double reptation theory and Doi and Edwards' molecular dynamics applied to A/A polymers brought into intimate contact in the molten state. The material parameters for the model are obtained from linear oscillatory shear experiments, in which the dynamic shear modulus is measured in parallel plate geometry under a small amplitude of deformation as a function of time and frequency for a sandwich‐like assembly. The experiments were conducted on polystyrene (PS) blends with constant weight average molecular weight (Mw) but with variable number average molecular weights (Mn). The measured self‐diffusion coefficients showed that the presence of short molecules in the blend increases the mean value of the self‐diffusion coefficient and the magnitude of such increase can be quantitatively evaluated by the proposed model.
Hydrophobic Interactions in Silane‐Treated Silica Suspensions and Bitumen Emulsions
Authors: Sanders R Sean , Chow Ross S. , Masliyah Jacob H.
Published: July 2010

In the extraction of bitumen from Canada's oil sands reserves, bitumen droplet coalescence is an important factor in determining the efficacy of the separation process. In a simplified analysis of bitumen droplet interactions, the relative contributions of classical DLVO and non‐DLVO forces occurring between a bitumen droplet and surface‐treated planar collector were evaluated using the impinging jet cell technique. Initial experiments were conducted using a system consisting of silane‐treated silica particles and a hydrophobic collector. This system is known to exhibit attractive non‐DLVO interactions as was clearly demonstrated by the present study. The attachment of bitumen droplets onto two different hydrophobic collectors was then examined. Results of these experiments indicate that bitumen droplet interactions involve an additional repulsive force that may be attributable to the heterogeneous nature of the droplet surface.
Model and Simulation of a Ported Kiln for Iron Oxide Pellet Induration
Authors: Davis Richard A. , Englund David J.
Published: July 2010

A mathematical model of a ported kiln for iron oxide pelletizing was developed to simulate the effects of under‐bed air injection on kiln fuel requirements and magnetite oxidation. A tanks‐in‐series model was used to set up material and energy balance equations for countercurrent flow of solids and gas through the kiln. The diffusion‐limited, shrinking core model was used for the magnetite oxidation reaction kinetics. The port air distribution in the model was adjusted by global optimization to minimize the fuel requirement. The simulation results show that magnetite oxidation may be completed in the kiln with significant fuel savings.
Modelling of Hydrothermal‐Mechanical Expression of Brown Coal
Authors: Guo Jian , Tiu Carlos , Uhlherr Peter H. T.
Published: July 2010

The large water content of brown coal can be reduced by hydrothermal‐mechanical expression (HME). The HME process combines the advantages of hydrothermal dewatering and mechanical dewatering and consequently, with low input of energy, produces dry, dense and hydrophobic coal. The mechanism of the HME process is analysed using the theory of one‐dimensional consolidation. A Terzaghi‐Voigt combined model is used to model the HME process operated at high temperature and pressure. The temperature‐related behaviours of some important model coefficients including the consolidation coefficient and the creep constant are identified. The model prediction for moisture reduction during expression agrees well with experimental data.
Measurement of Solid Circulation Patterns in Liquid—Solid and Gas—Liquid—Solid Fluidized Beds
Authors: Barghi Shahzad , Briens Cedric L. , Bergougnou Maurice A.
Published: July 2010

Solid circulation patterns were determined by measuring collisions between tracer particles and cylindrical probes in liquid—solid and gas—liquid—solid fluidized beds. Special probes were used to obtain two‐ and three‐dimensional views of particle motion. Circulation patterns for 3 and 5 mm glass beads were studied. Mixing cells, which had been formed at low liquid velocities, grew in size and eventually merged as the liquid velocity increased. The flow patterns of smaller particles having the same density as bed particles and particles lighter than bed particles (graphite particles) with the same size were also measured.
Decreasing the Sampling Time Interval in Radioactive Particle Tracking
Authors: Mostoufi Navid , Kennedy Gregory , Chaouki Jamal
Published: July 2010

The study of the movement of solids in multiphase reactors using radioactive particle tracking is currently limited to fairly modest particle velocities because of count‐rate limitations of the detection system. In this work, this restriction was overcome by increasing the activity of the radioactive tracer, by decreasing the sampling time interval and by modifying the particle tracking software to recognize which detectors were saturated and to use only the data from the remaining unsaturated detectors. Higher tracer activity resulted in lower standard deviation of the calculated tracer coordinates.
Two‐Phase Bubbly Flow Structure in Large‐Diameter Vertical Pipes
Authors: Shoukri Mamdouh , Hassan Ibrahim , Gerges Ihab
Published: July 2010

The two‐phase flow structure of an air‐water, bubbly, upward flow in a 20 cm diameter pipe is presented with particular emphasis on the local interfacial area concentration. The radial distribution of void fraction, bubble velocity, bubble size, bubble frequency, and interfacial area concentration were measured using a local dual‐optical probe. The experimental results showed that the saddle‐type distribution of void fraction and interfacial area concentration, which are common for bubbly flow in small diameter pipes, only appeared in the present experiments under conditions of very low area‐averaged void fraction (<ϵ> < 0.04). The values for the interfacial area concentration were higher in large diameter pipes when compared with data obtained under the same flow conditions in small pipes. The area‐averaged void fraction data were correlated using the drift‐flux model.
Kinetic Modeling of Liquid Phase Oxidation of Cyclohexane
Authors: Bhattacharya Arijit , Mungikar Amol
Published: July 2010

A kinetic model for the liquid phase oxidation (LPO) of cyclohexane has been derived using a reaction network based on a consistent free radical mechanism. It was demonstrated that on embedding this rate model within the overall model of a semi‐batch gas‐liquid reactor (SBR) one can predict the time variation of the dissolved oxygen concentration and the rate of oxygen absorption which compare fairly closely with some well regarded published experimental data. The model is distinguished by easy extendibility and modularity whereby it could be tailored to predict, in the context of a SBR, cyclohexane conversion and ketone‐alcohol (K‐A) product selectivity levels as observed in commercial plants and in the published data on pilot plant experimentation. The model is expected to be of use in the design and scale‐up of LPO reactors.
Energy Dissipation at the Slug Nose and the Modeling of Solids Transport in Intermittent Flow
Authors: Stevenson Paul , Thorpe Rex B.
Published: July 2010

It is shown, by means of Lagrangian momentum and power balances across the slug nose in slug flow, that the power dissipated due to sudden expansion of the fluid in the film immediately downstream of the slug nose is greater than the power lost due to viscous action at the pipe wall but that it may not be large enough to materially aid particle transport. This has the implication that sand transport in intermittent flow may be considered as transport in a hybrid flow of hydraulic conveying and stratified flow when the length of the mixing section at the slug nose is short compared to the length of the slug body.
Natural Convection in Heat Generating Oval Porous Enclosures: A Non‐Darcian Model
Authors: Das Subrat , Sahoo Ranjit Kumar , Morsi Yos S.
Published: July 2010

This paper presents a series of numerical simulations dealing with the problem of natural convection flows and associated heat transfer in an enclosure filled with a fluid‐saturated porous medium. The analysis is based on the finite element technique and incorporates the Brinkman‐extended Darcy model for an oval enclosure. The numerical results obtained for a modified Rayleigh number, Ra, Darcy number, Da, offset, E, and eccentricity, e, are presented and discussed. The numerical predictions for a square enclosure compared well with published data. It is found that any increase in Da or Ra results in a higher fluid velocity that is responsible for shifting the core of the flow. Moreover, at higher ovality (E = 0.5), asymmetric flow is observed even at the lower range of Rayleigh number (Ra ⩽ 20), which may be attributed to the effect of curved isothermal wall.
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

The 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

The 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

The 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

Polyvinyl 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

Two‐ 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

The 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

In 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

Halogenated 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

In 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

The 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

The 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

The 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

For 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

A 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

A 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

A 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

Local 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.