bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of wall velocities on the determination of optimal separation times in electrical field flow fractionation (EFFF)
Authors: Pascal Jennifer , Oyanader Mario , Arce Pedro E.
Published: May 2010

Electrical field flow fractionation (EFFF) has two perpendicular driving forces that help to produce an optimal separation of solute in a mixture [Giddings, Science 1993; 260:1456–1465]. For Couette flow based devices, the ratio of the velocity of the capillary walls offers an extra parameter that can be exploited to enhance the efficiency of EFFF applications. The analysis of the effects of this parameter on optimal times of separation is the subject matter of this contribution. The use of this additional parameter increases flexibility in the design of new devices for the improvement of the separation of solutes, such as proteins, DNA, and pharmaceuticals, as it will be illustrated with the results of this analysis (Jaroszeski et al., 2000; Trinh et al., 1999). The analysis has been illustrated by selecting parameter values that represent a number of potential useful applications. A set of five parameters (i.e., z, the valence; µ, electrophoretic mobility; Pe, Peclet number; Ω, the orthogonal applied electrical field; and R, the ratio of channel wall velocities) has been combined to obtain the best operating conditions for optimal separation of solutes. Results indicate that R, the ratio of the channel wall velocities, is actually the most important driving parameter.
Direct meso‐scale simulations of fibres in turbulent liquid flow
Authors: Derksen J. J.
Published: May 2010

A procedure for direct, meso‐scale simulations of flexible fibres immersed in liquid flow is introduced. The fibres are composed of chains of spherical particles connected through ball joints with the bending stiffness of the joints as a variable. The motion of the fibres and the liquid is two‐way coupled with full resolution of the solid–liquid interface. First the simulation procedure is validated by means of an analytical solution for sphere doublets in zero‐Reynolds simple shear flow. Subsequently we use the numerical method to study inertial flows with fibres, more specifically the interaction of a fibre with isotropic turbulence.
Development of airlift bubble column dispersed with micro‐bubbles
Authors: Yasuda Keiji , Wang Yufei , Haneda Koichi , Naito Testuya , Bando Yoshiyuki , Takeyama Tomokiyo , Kawase Yasuhito
Published: May 2010

Micro‐bubbles were dispersed in the bubble column with draft tube, and the length and diameter of draft tube were changed. The flow characteristics in air–water system were measured. Ozone gas and methylene‐blue aqueous solution were used, and the decomposition performance was examined. With increasing draft tube length, both the gas holdup and liquid velocity in the annular section increased. When the diameter ratio of draft tube to column was about 0.5, both the gas holdup and liquid circulation flow rate had maxima. For the decomposition by using ozone, the installation of draft tube enhanced the mass transfer and decomposition performance.
Gas–liquid interfacial area in the oxygen absorption to oil‐in‐water emulsions in an airlift reactor
Authors: Gómez‐Díaz D. , Gomes N. , Teixeira J. A. , Belo I.
Published: May 2010

The present work includes an exhaustive study about gas–liquid interfacial area between gas phase and liquid heterogeneous medium generated in an airlift bioreactor. The system studied is composed by water, methyl ricinoleate (MR), and Tween‐80, since it is the base of the medium used for the production of γ‐decalactone, a peach‐like aroma compound of industrial interest that can be produced biotechnologically through the biotransformation of ricinoleic acid, by the yeast Yarrowia lipolytica. Experimental results allow describing the hydrodynamic behaviour of the gas phase into the biphasic medium.
Simulation of direct leaching of zinc concentrate in a non‐ideally mixed CSTR
Authors: Lampinen Matti , Laari Arto , Turunen Ilkka
Published: May 2010

A simulation model for direct leaching of zinc concentrate in a continuous non‐ideally mixed stirred tank reactor (CSTR) is presented. The model takes into account the surface reactions between zinc in the solids and ferric iron ions in the liquid phase, oxidation of ferrous iron back to ferric iron, gas–liquid mass transfer of oxygen, decrease of particle size as the reaction proceeds, and the effect of hydrostatic pressure on the oxygen dissolution rate. The model is pseudo‐homogeneous and is approximative in the sense that it neglects the effects of particle size distributions and population balances of the concentrate particles.
Determination of tanshinone I, tanshinone IIA, and cryptotanshinone in Salvia miltiorrhiza bunge and urine sample by HPLC
Authors: Tian Minglei , Row Kyung Ho
Published: May 2010

A simple and sensitive HPLC method to detect tanshinone I, tanshinone IIA, and cryptotanshinone in human urine was developed and validated. Chromatographic separation was achieved on a C18 column (4.6 mm × 250 mm, 5 µm) using a mixture of methanol/water (78:22 v/v, containing 0.5% acetic acid) as the mobile phase at a flow rate of 0.5 mL/min with UV detector at 254 nm. The calibration curve of tanshinones was linear over a range of 1.0 × 10−4 – 1.0 mg/mL. The limit of quantification (LOQ) was found to be 57.0, 76.0, and 45.0 ng/mL, respectively. This method can estimate the pharmacokinetic parameters of tanshinones in human urine after the intravenous and intraperitoneal administration of stanchions.
Effect of solid material and surfactant presence on interactions of bubbles with horizontal solid surface
Authors: Fujasová‐Zedníková Mária , Vobecká Lucie , Vejrazka Jiri
Published: May 2010

The interaction of a bubble with an immersed horizontal solid surface is studied experimentally. The effect of presence of a surfactant (limited to a specific nonionic surfactant, α‐terpineol, of various concentrations) and of surface material (cleaned glass, polypropylene, polyethylene, and Teflon) is investigated. The study focuses on two particular stages of the interaction, (i) the process of bubble bounce, which includes a collision and subsequent rebound from the solid surface, and (ii) the bubble attachment, which occurs after collision in time much longer than the duration of bounce and also after disappearance of all visible bubble movement. It is observed that the effect of the surface material on the bouncing is minor, possibly due to the liquid film separating the bubble and the solid surface. The presence of surfactant significantly affects the bouncing process. It not only decreases the initial bubble velocity, but also diminishes the bubble deformation after the collision and suppresses the bubble rebound from the surface. No rebound from the surface is observed in the most concentrated (1 × 10−3 mol/L) α‐terpineol solution. The adhesion time depends both on the solid material and α‐terpineol concentration. If the α‐terpineol concentration is increased, the adhesion time increases in the case of polypropylene surface, while it decreases in the case of polyethylene and Teflon surfaces. Results of this study are relevant for the description of attachment mechanism and to determine the proper conditions for selective flotation of plastics.
Kinetics and mass transfer in hydroformylation—bulk or film reaction?
Authors: Bernas Andreas , Wärnå Johan , Mäki‐Arvela Päivi , Murzin Dmitry Yu , Salmi Tapio
Published: May 2010

The kinetics of a gas–liquid reaction, alkene hydroformylation was studied in the presence of a homogeneous catalyst in a pressurised laboratory‐scale semibatch reactor. Hydroformylation of propene to isobutyraldehyde and n‐butyraldehyde was carried out at 70–115°C and 1–15 bar pressure in 2,2,4‐trimethyl‐1,3‐pentanediol monoisobutyrate solvent with rhodium catalyst using the ligands cyclohexyl diphenylphosphine. In order to evaluate the influence of mass transfer, experiments were made using varied stirring rate from 100 to 1000 rpm at 100°C and 10 MPa syngas pressure. Only at higher stirrings rates, the reaction took place in the kinetic regime. A reactor model was developed comprising both complex kinetics and liquid‐phase mass transfer. The model was based on the theory of reactive films. The model is able to predict under which circumstances the hydroformylation process is affected by liquid‐phase diffusion of the reactants. Experimental data and model simulations are presented for the hydroformylation of propene in the presence of a homogeneous rhodium catalyst.
Organic coated solids in athabasca bitumen: Characterization and process implications
Authors: Bensebaa Farid , Kotlyar Luba S. , Sparks Bryan D. , Chung Keng H.
Published: May 2010

Bitumen, separated from oil sands by the hot water extraction process, contains ultra‐fine (< 200 nm), inorganic solids (BS). Surfaces of BS particles are coated with toluene insoluble organic matter (TIOM). This organic material is polar and aromatic with contributions from both humic and asphaltene‐like components. Although the surfaces of BS particles are dominated by TIOM, the coverage is patchy rather than continuous. As a result, these solids are capable of stabilizing fine water emulsions in the bitumen phase. The nature of the organic matter on the surfaces of the particles is such that it has a high propensity to form coke. Therefore, these particles can also play a role in fouling on equipment and catalysts.
Modelling transverse mixing in a rolling drum
Authors: Van Puyvelde Dennis R. , Wilson Michael A. , Young Brent R. , Schmidt S. James
Published: May 2010

In this paper, a new model of transverse mixing in a rotating drum is derived from dynamic data collected from an experimental rig. Since the active layer has often been declared as the zone that is responsible for the mixing of solids in a rolling bed, the active layer was characterized so that its properties could be predicted for a wide range of experimental conditions. The mixing model consisted of two correlations, one to predict the mixing rate in the drum and the other to predict the final contact between the two materials. These correlations were linked back to the operational variables of the drum, such as the drumfs loading, size and rotational velocity. By combining these two correlations the time required to fully mix the material in the drum could be predicted. The mixing model was tested against independent data and good agreement was observed between the experimentally derived results and those predicted by the mixing model. Furthermore, this mixing model was designed such that it would be easily applicable to different sized drums. The extrapolation ability was tested on different smaller‐sized drums and found to agree considerably with experimental results.
Control of fines suspension density in the fines loop of a continuous KCl crystallizer using transmittance measurement and an FBRM® probe
Authors: Tadayyon Abdulsamad , Rohani Sohrab
Published: May 2010

The control of crystal size distribution (CSD) is investigated in a 1.5 L laboratory cooling KCl crystallizer using fines dissolution rate as the manipulated variable. The controlled variable was either the fines suspension density in the fines withdrawal loop, measured by an innovative double‐sensor turbidity meter manufactured in‐house, or the chord length distribution (CLD) measured by the Focused Beam Reflectance Measurement (FBRM®) probe (model: Par‐Tec® 100, Lasentec®, Redmond, WA). It was shown that effective control of mean crystal size and fines suspension density in the presence of setpoint and disturbance changes is feasible with both control schemes. The double sensor turbidity sensor proved to be very rugged even in the presence of insoluble clay background particles. The FBRM® probe was more sensitive and capable of detecting particle breakage and flocculation.
Imaging in powder technology from visualization to measurement: Application to shape quantification
Authors: Vivier Hervé , Pons Marie‐Noëlle , Bernard‐Michel Bruno
Published: May 2010

Image analysis tools and statistical procedures have been developed to quantify particle shape. Three copper sulfate crystallization processes have been carried out and the effects of process operating parameters upon crystal morphology have been studied as well as the relationships between morphology and powder end use properties. Both aspects give the capability to master end‐use properties by the process parameters. It is also shown that size distribution without morphology is deficient to globally characterize a powder and to describe its behaviour.
Deposition velocities for newtonian slurries in turbulent flow
Authors: Gillies Randall G. , Schaan Jason , Sumner Robert J. , McKibben Melissa J. , Shook Clifton A.
Published: May 2010

In this contribution both new and previously published deposition velocity data for aqueous Newtonian slurries are incorporated in a correlation which complements the earlier predictions of Durand, Wilson and A.D. Thomas. Most of the new data has been obtained for slurries of narrowly sized sand particles of median diameter ranging between 90 and 420 μm, in pipes of diameter between 0.05 and 0.5 m. The data were obtained in laboratory investigations under isothermal flow conditions.
A laboratory investigation of horizontal well heavy oil—water flows
Authors: McKibben Melissa J. , Gillies Randall G. , Shook Clifton A.
Published: May 2010

Experimental simulations of model well‐bore flows in laboratory pipelines show that frictional energy losses (i.e., pressure drops) are reduced when water is present with heavy oil. The reduction has been shown to increase with the water fraction. The mixtures are not oil in water emulsions in the classical sense of the term. At the low axial velocities which characterize wellbore flows, the flow regime is inherently intermittent. Using a variety of methods the structure of the flow has been examined to identify the flow regime and the cause of the reduced pressure gradients. It has been found that the water travels as large slugs and that oil is invariably present at the wall when the mixture flows through a steel pipe. The evidence suggests that a significant fraction of the oil is transported within the water slugs. A tentative flow regime boundary between the regions of intermittent and continuous water‐assisted flow is proposed in terms of the mixture Froude number and the injected water fraction.
Predicting pressure gradients in heavy oil—water pipelines
Authors: McKibben Melissa J. , Gillies Randall G. , Shook Clifton A.
Published: May 2010

Experimental investigations of the flow of water‐heavy oil mixtures at velocities typical of oil‐field gathering systems show that continuous water assisted flow at very low pressure gradients can be achieved. The principal criterion to be satisfied in establishing this desirable flow regime appears to be use of sufficient water, with the velocity also playing a role. It also appears that oil viscosity and water fraction effects on pressure gradient are small provided the beneficial flow regime is established. The flows resemble core‐annular flow, which has been observed previously in Bitumen froth and water‐heavy oil flows, with an oil layer on the pipe wall. However, the correlation for pressure gradient is somewhat different from that reported previously for Bitumen froth flows.
Une nouvelle technologie d'appareils de dépôt chimique en phase vapeur. Partie 1 : Présentation et analyse des résultats expérimentaux
Authors: Vergnes Hugues , Duverneuil Patrick , Couderc Jean‐Pierre
Published: May 2010

Cet article présente une nouvelle technologie d'appareils de dépôt chimique en phase vapeur qui a été développée afin de supprimer plusieurs problèmes rencontrés dans l'industrie microélectronique. En outre, cette technologie permet de concevoir un modèle réduit parfaitement représentatif du réacteur industriel, très utile pour effectuer des développements plus rationnels de nouvelles applications. La première partie de cet article décrit les réacteurs puis présente et analyse un ensemble de résultats expérimentaux. Quatre types de dépôts, de complexité croissante, ont été choisis pour effectuer une comparaison détaillée entre les performances de la nouvelle technologie et celles des réacteurs que les industries microélectroniques utilisent classiquement.
Effects of pressure and impingement angle in flaming processes
Authors: Liakos Harilaos H. , Koukou Maria K. , Markatos Nikolaos C. , Founti Maria A.
Published: May 2010

This work investigates the effects of varying the pressure of the mixture reactants and the angle of impingement on the performance characteristics of a turbulent premixed jet flame impinging on a solid surface. These effects are important for the design of torches and flaming machines used for material and metal cutting and forming. The combustion and flow characteristics are modelled using a finite volume computational approach. Based on the simulation results, it is shown that, by increasing the pressure of the mixture reactants, the flame‐surface interaction mechanisms are modified. Changing the impingement angle increases the role of chemical kinetics and reduces maximum temperature values due to increased local flame extinction. The heat released and temperature predictions are compared to experimental data and the agreement is satisfactory.
Formation of needle‐like lepidocrocite fine particles by oxidation of an aqueous suspension of ferrous hydroxide in a bubble column
Authors: Cho Hae‐Man , Kawasaki Hiroyuki , Kumazawa Hidehiro
Published: May 2010

Fine particles of needle‐like lepidocrocite (γ‐FeOOH) were synthesized by the oxidation of aqueous suspensions of ferrous hydroxide using a bubble column with draft tube at a constant temperature ranging from 20°C to 30°C. The oxidation steps leading to green rust (an intermediate) and lepidocrocite (final product), termed Step I and II, respectively, could be described apparently as first order, with respect to oxygen, and zero order, with respect to total ferrous species. When the concentration of oxygen in the feed stream was varied under a constant gas velocity, the mean size based on the major axis of needle‐like particle decreased from 0.60 to 0.35 μm with increasing oxidation rate. When the gas velocity was varied under a constant oxygen concentration, the particle size was almost independent of the oxidation rate and was equal to ca. 0.6 μm. By the addition of a small amount of sodium dihydrogenphosphate (NaH2PO4), the major axis could be reduced to 0.2 μm with the minor axis and the oxidation rate almost unchanged.
Self‐sustained oscillations in opposed impinging jets in an enclosure
Authors: Johnson David A. , Wood Philip E.
Published: May 2010

The flow of jets in confining enclosures has significant application in many engineering processes. In particular, the impingement of axisymmetric jets in a confined space has been examined using flow visualization, laser Doppler anemometry, and numerical simulations. Several flow regions were found; stable steady, regular oscillatory, and irregular oscillatory. Initially, a steady flow field existed for all arrangements for Red < ˜90 (based on the nozzle diameter d, the fluid kinematic viscosity v and the volumetric flow rate Q through the nozzle (Q = πd2/4Uavg)) but subsequent increments in the fluid velocity caused a regularly oscillating flow field to emerge. The onset of the oscillations and the upper limit of finite oscillations were found to be a function of the Red, and the nozzle diameter to chamber dimension ratio. Steady numerical simulations predicted the steady flow field well and good agreement was obtained in unsteady simulations of the oscillating flow field. The oscillating flow field is considered to be a class of self‐sustaining oscillations where instabilities in the jet shear layer are amplified because of feed back from pressure disturbances in the impingement region.
Instabilities when using a standard (T/3) rushton turbine for stirring as foam disruption (SAFD)
Authors: Boon Lotte A. , Bujalski Waldemar , Nienow Alvin W. , Hoeks Frans W.J.M.M. , Van Der Lans Rob G.J.M.
Published: May 2010

The concept of using the upper stirrer for foam disruption in a bioreactor agitated by multiple impellers has recently been published by Hoeks et al. (1997). This concept, stirring as foam disruption (SAFD), was shown by them to be effective with a range of impellers. However, the commonly used (so‐called) standard Rushton turbine of one‐third the fermenter diameter was not included. This paper fills that important gap. By measuring the foam height, the holdup, the power draw and the velocities of the liquid in the dispersion just below its top surface, it is concluded that the SAFD concept does not work well with the standard Rushton turbine. This is because the amount of broth for which foam can be disrupted is less than that found with all the other impellers tested to date; and even when foam disruption occurs, significant flow instabilities and torque fluctuations are found. Perhaps the poor performance of this impeller, which has been used so frequently in industry and in academic studies, explains why the concept of SAFD was not developed earlier.
Development of a novel non‐contact proximity gauge for thickness measurement of soft deposits and its application in fouling studies
Authors: Tuladhar T. R. , Paterson W. R. , Macleod N. , Wilson D. I.
Published: May 2010

This paper describes the development of a novel proximity gauging technique for soft deposits, exploiting a siphon effect. This non‐contact technique has the capability to measure the thickness of soft deposits on a surface in situ and in real time. A theoretical model of performance has been developed and its validity demonstrated by calibration experiments. Local thickness measurements of soft deposits such as whey protein deposit, supermarket butter and sticky foam on metal surfaces had an accuracy of ±20 μm for a deposit thickness of 500 to 1000 μm. The potential of this technique for on‐line monitoring of fouling and cleaning processes in liquid environments is demonstrated by preliminary studies of alkali (NaOH) cleaning of whey protein deposits from stainless steel surfaces.
Influence des principaux paramètres opératoires sur le dépôt de silicium à partir de silane par CVD en lit fluidisé en vue de limiter les problèmes d'agglomération
Authors: Ramiro Ruvalcaba J. Rodriguez , Caussat Brigitte , Hemati Merhdji , Couderc Jean‐Pierre
Published: May 2010

Le dépôt CVD de silicium à partir de silane sur des poudres d'un lit fluidisé constitue une technique de modification de surface efficace et flexible, qui présente cependant l'inconvénient majeur de voir la couche de particules s'agglomérer au‐delà d'une certaine concentration d'entrée en réactif. C'est pour progresser dans la compréhension de ce phénomène que des conditions opératoires jusqu'alors peu explorées, couvrant des températures inférieures à 550°C, ont été étudiées à la fois expérimentalement et par voie théorique, à l'aide de modèles globaux de simulation de type Kato et Wen. L'influence des principaux paramètres opératoires a été analysée en détail, non seulement sur le plan de l'efficacité globale du procédé, mais aussi en ce qui concerne le comportement thermique du lit fluidisé, directement lié aux mouvements des particules solides, et done à I'éventuelle prise en masse de la couche.
Simulation of fine particle formation by precipitation using computational fluid dynamics
Authors: Piton Damien , Fox Rodney O. , Marcant Bruno
Published: May 2010

The 4‐environment generalized micromixing (4‐EGM) model is applied to describe turbulent mixing and precipitation of barium sulfate in a tubular reactor. The model is implemented in the commercial computational fluid dynamics (CFD) software Fluent. The CFD code is first used to solve for the hydrodynamic fields (velocity, turbulence kinetic energy, turbulent energy dissipation). The species concentrations and moments of the crystal size distribution (CSD) are then computed using user‐defined transport equations. CFD simulations are performed for the tubular reactor used in an earlier experimental study of barium sulfate precipitation. The 4‐EGM CFD results are shown to compare favourably to CFD results found using the presumed beta PDF model. The latter has previously been shown to yield good agreement with experimental data for the mean crystal size at the outlet of the tubular reactor.
Gas flow regime changes in a bubble column filled with a fibre suspension
Authors: Heindel Theodore J.
Published: May 2010

Gas flow characteristics in opaque fibre suspensions have been captured on film using a stop‐motion X‐ray imaging technique called flash X‐ray radiography (FXR). Gas flows in a bubble column filled with various cellulose fibre suspensions from 0% (an air–water system) to 5% by mass have been observed. The gas flow regime changes from vortical to churn‐turbulent as the fibre concentration increases for a fixed superficial gas velocity. Two new gas flow regimes, identified as surge churn‐turbulent and discrete channel flow, have also been recorded at high fibre concentrations.
Radial nonuniformity index (RNI) in fluidized beds and other multiphase flow systems
Authors: Zhu Jing‐Xu (Jesse) , Manyele Samwel V.
Published: May 2010

The radial nonuniformity index (RNI) is a new non‐dimensional index recently devised to quantify the extent of radial variations of flow parameters in fluidized beds and other multiphase flow systems. The index, defined as the ratio of the standard deviation of the given flow parameter in the radial direction to the maximum practically possible standard deviation of that particular parameter, is shown to be an excellent measure of the radial flow structure. This index allows the use of a single value to summarize the radial variation of a given flow parameter. The higher the value of the RNI the less uniform is the flow, and vice versa. Using this technique, radial distributions of local solids concentration and particle velocities from different circulating fluidized bed systems (gas‐solid and liquid‐solid, upflow and downflow) were examined. It has been found that the RNI can be confidently related to the flow conditions in the circulating fluidized beds, and more insight understanding has been achieved.
Application of an air‐operated two impinging streams extractor in liquid‐liquid extraction and comparison with other contactor types
Authors: Dehkordi Asghar Molaei , Kaghazchi Tahereh , Sohrabi Morteza
Published: May 2010

Extraction of succinic acid by means of normal butanol from its aqueous solutions (BSW), acetic acid by means of distilled water from kerosene (WAK) and iodine by means of kerosene from its aqueous solution (KIW) have been investigated in an air‐operated two impinging streams extractor (AOTISE) with spray nozzles. The effects of air flow rate, solutions flow rate, extractor length and diameter as well as modes of operation and impinging streams on extraction efficiency have been investigated. These results indicate that AOTISE is an efficient device for extraction processes. In addition, the overall volumetric mass transfer coefficients (KLa) are reported. The latter coefficients are important in design and may be used to compare the performance capability of various kinds of extractors.
CO2N2 and CO2CH4 binary adsorption isotherms with H‐ZSM5: The importance of experimental data regression with the concentration pulse method
Authors: Harlick Peter J. E. , Tezel F. Handan
Published: May 2010

A novel functional form for describing the binary Kp data obtained with concentration pulse chromatography has been developed. The application of the novel function set was evaluated by studying the binary CO2‐CH4 and CO2‐N2 systems using H‐ZSM‐5 as the adsorbent with SiO2/Al2O3 ratios of 30 and 280. Pure isotherms at 40°C, up to 100 kPa pressure and binary isotherms at 40°C and 100 kPa total pressure have been determined using the concentration pulse method. The results from the use of the novel function set show that a small deviation of the regression curve from the experimental data will result with differences in the binary isotherms.
Extended kalman filter‐based nonlinear model predictive control of a continuous KCl‐NaCl crystallizer
Authors: Tadayyon Abdulsamad , Rohani Sohrab
Published: May 2010

An extended Kalman filter (EKF)‐based nonlinear quadratic dynamic matrix control (EQDMC) for an evaporative cooling draft‐tube baffled (DTB) KCl crystallizer is developed. The controller is used to maintain the productivity, crystal mean size and impurity of crystals. Since these controlled variables are not directly measurable, the EKF is used to estimate them. The nonlinear controller is a combination of an extended linear dynamic matrix control (EDMC) and the quadratic dynamic matrix control (QDMC). This combination provided good control of the system despite the process nonlinearity, constraints, and inadequate reliable online measurement of the controlled variables. The performance of the controller in the presence of plant/model mismatch, disturbance, wrong estimation and simultaneous step changes in the controller setpoints is discussed.
Fuzzy multi‐model based adaptive predictive control and its application to thermoplastic injection molding
Authors: Li Mingzhong , Yang Yi , Gao Furong , Wang Fuli
Published: May 2010

Many chemical processes are inherently nonlinear. A single linear model is ineffective for these processes. Several local linear models may be developed for different operating conditions. A combination of these local models, through a fuzzy logic representation, results in an overall model for a wider operation range. In this paper, on‐line improvements and a fuzzy multi‐model have been proposed for predictive control implementation. Firstly, assuming that the premises of the fuzzy rules keep their original structures, the linear parameters in the rule consequents are on‐line updated by a weighted recursive least squares algorithm at each sample interval. Secondly, a batch learning algorithm is proposed to tune the fuzzy rule premises using a competitive learning algorithm. The effectiveness of the proposed improvements is demonstrated with experimental applications to the filling velocity control of thermoplastic injection molding
Dynamic simulation and control of a paper machine wet end
Authors: Yap Eddy F. , Kwok K. Ezra , Dumont Guy A.
Published: May 2010

A good simulation model for paper machines can be used to identify deficiencies in the design, bottlenecks during operation, and regions of poor control. It also allows users to test their hypotheses and innovations without potentially causing major upsets and reducing throughput. In this work, a dynamic model of the wet end system has been developed using the IDEASTM platform, describing the distribution of fines, fillers and fibres throughout the system. The model was then tested at steady state with mill data for the low‐ash and high‐ash production grades, and the results show that over 70% of the predicted values had only 5% deviation. The dynamic simulation was also used to show that the retention aid controller would react in the wrong direction due to changes in the wire pit consistency and the stock ratio would cause major changes in stream compositions and consistencies of the wet end.
Cold and hot gas filtration using a novel mobile granular bed with an inner fluidized section
Authors: Abatzoglou Nicolas , Gagnon Martin , Chornet Esteban
Published: May 2010

Two experimental studies were conducted with a novel moving granular bed filter (NMGBF). The first one was performed on a cold and dry mock‐up module operated at room temperature and was aimed at a) proving the concept, b) establishing the operating patterns and flow profiles and c) optimizing the operating conditions. The gas flowrate and the geometry of the filter were the main variables studied. The second study was conducted on a prototype hot filter PDU (Process Development Unit) under real time operating conditions. The filter was one of the modules of a hot‐gas‐conditioning‐train in a fluidized bed gasifier. Results showed similar particles collection efficiency for hot‐ and cold‐dry filtration. The filter showed an efficiency of 99.9% over 55 h filtration time for particles larger than 1 μm, while for submicronic particles the efficiency is between 84% and 96% (weight basis). This paper presents and discusses the apparatus, the experimental methods and conditions as well as characteristic results on the two prototypes used.
γ‐Alumina supported Cu‐Ni bimetallic catalysts: Characterization and selective hydrogenation of 1,3‐butadiene
Authors: Kang Min , Song Min Woo , Kim Tae Won , Kim Kyung Lim
Published: May 2010

Addition of a second metal often improves the selectivity of a supported catalyst for the hydrogenation of 1,3‐butadiene. Catalysts containing 15 wt% Ni and varying amounts of Cu were prepared and characterized by TPR, XRD and XPS. The Cu‐Ni interaction affects the reduction behavior of the catalysts. TPR result shows that the synergetic effect of copper and nickel modifies the capability of metal to combine with hydrogen in bulk phase. The Ni 2p spectra in XPS shows significant shifts toward lower binding energies with increasing copper loading. From XRD results it is represented that aggregation of nickel occurs more easily due to the copper addition. The adding of copper on Ni/Al2O3 makes the conversion rate decreased and increases the selectivity to 1‐butene.
A catalyst deposited over the external surface of the reactor tubes—A new solution for carrying out heterogeneous catalytic processes
Authors: Anastasov Asen I. , Nikolov Valentin A.
Published: May 2010

A mathematical model of a new reactor design has been proposed. In the new reactor the catalyst is deposited over the external surface of the tubes, where the coolant flows. The widespread industrial process of oxidation of o‐xylene into phthalic anhydride was investigated. The results obtained show significant advantages of the new design in comparison with the conventional fixed bed reactor operating in the industry. They are: much higher productivity, easily controlled temperature regime, raised selectivity and decrease content of side products, as well as an opportunity for additional feed‐in of the reagent along the reactor height. The technological regime of the oxidation process was optimized.
Modelling and economic analysis of gas production from hydrates by depressurization method
Authors: Khataniar Santanu , Kamath Vidyadhar A. , Omenihu Sunday D. , Patil Shirish L. , Dandekar Abhijit Y.
Published: May 2010

Gas production from a hydrate reservoir involves decomposition of the solid hydrate. An analytical model is developed to predict reservoir performance for gas production by the depressurization method from a hydrate reservoir containing associated free gas. The model is developed by combining the intrinsic kinetics of hydrate decomposition, which is of interest to chemical engineers, with gas inflow performance relationship and material balance equations. An economic analysis model is also developed and incorporated with the reservoir performance model. These models are used in a case study of gas production from a hydrate reservoir in the Alaskan North Slope. The results show that gas transportation cost is the main factor controlling feasibility of commercial gas production. The hydrate zone contributes significantly to overall reservoir performance by arresting pressure decline and maintaining gas production rate.
Perturbation signal design for neural network based identification of multivariable nonlinear systems
Authors: Kulkarni Pankaj S. , Gudi Ravindra D.
Published: May 2010

The paper focuses on issues in experimental design for identification of nonlinear multivariable systems. Perturbation signal design is analyzed for a hybrid model structure consisting of linear and neural network structures. Input signals, designed to minimize the effects of nonlinearities during the linear model identification for the multivariable case, have been proposed and its properties have been theoretically established. The superiority of the proposed perturbation signal and the hybrid model has been demonstrated through extensive cross validations. The utility of the obtained models for control has also been proved through a case study involving MPC of a nonlinear multivariable neutralization plant.
The mixing sensitivity of polysulphide generation
Authors: Dobson Heather K. , Bennington Chad P.J.
Published: May 2010

The effect of mixing and mass transfer on polysulphide generation by catalytic oxidation of sodium sulphide was studied using two batch‐operated reactors. One was a sparged reactor operated at atmospheric pressure and low mixing intensities (0.37 to 28 W/kg), the other was an unsparged pressurized reactor characterized by high mixing intensities (17 to 3100 W/kg). The reaction parameters examined included the impeller speed, sparged gas flowrate, oxygen partial pressure, and catalyst loading and type. In both reactors the maximum polysulphide yield, selectivity and rate of formation increased with increasing energy dissipation. Increased gas sparging increased the rate of reaction, but had little effect on either yield or selectivity. Increased oxygen partial pressure increased the rate of oxidation but decreased both the yield and selectivity. The type of catalyst dramatically affected the yield of polysulphide produced for a given set of reaction conditions with improved mixing increasing reaction rate, yield and selectivity.
Rheological examination of temperature dependence of conventional and polymer‐modified road bitumens
Authors: Zupančič Andreja , Žumer Miha
Published: May 2010

Rheological characterization of two types of road bitumens, conventional and polymer‐modified, has been examined in the temperature range between 20°C and 140°C. Tests were carried out before and after ageing following a thin‐film oven test. Polymer‐modified bitumens exhibit non‐Newtonian behaviour up to the 120°C due to a complex secondary structure formed by added polymers. For conventional bitumens, Newtonian behaviour was observed above 60°C. Special attention was paid to measurements and to analysis of the dynamic data of oscillatory shear. The mechanical spectra in a wide frequency range have been obtained using the WLF time‐temperature superposition principle. The analysis of viscoelastic data clearly showed the differences between the two types of bitumen. Conventional bitumens were more sensitive to temperature and to the ageing effects. For polymer modified bitumens, the elastic contribution to viscoelastic response was more pronounced, and independent of temperature and ageing.
Bubble coalescence and its effect on dynamic foam stability
Authors: Cho Yoon Seong , Laskowski Janusz S.
Published: May 2010

The size of bubbles generated using a single‐hole sparger, a multi‐hole sparger and a flotation cell were measured. While the size of bubbles generated from the single‐hole sparger does not depend on frother concentration, the bubble size strongly depends on frother concentration when the multi‐hole sparges, or flotation cell, are utilized. The bubbles size ceases to depend on frother at the concentrations exceeding the value characteristic for each frother and referred to as the critical coalescence (CCC). All the bubble size vs. frother concentration curves converge on a single curve. Aqueous solutions of the frothers that are characterized by low CCC values from foams quite stable under dynamic conditions. Since bubble coalescence can be inhibited by frother concentrations exceeding the CCC, sparing systems can be studied and compared only at frother concentrations that exceed CCC.
Flow regimes in a turbulent bed contactor
Authors: Albert Bruce E.R. , Pillutla Sai S.T. , Kamatam Krishnaiah
Published: May 2010

Experiments were conducted in a turbulent bed contactor (TBC) with and without downcomer operating in Type I and Type II modes to obtain the flow regime maps. The variables include flow rate of the gas and liquid phases, size and density of the particles, bed height, free open area of the supporting grid, and diameter and weir height of the downcomer. Static, partially fluidized, completely fluidized, flooding and annular regimes are identified depending on geometric and operating conditions. The effect of these variables on flow maps is discussed and correlations are proposed for delineating the flow regimes.
Pressure buildup in gas‐liquid flow through packed beds due to deposition of fine particles
Authors: Gray Murray R. , Srinivasan Naras , Masliyah Jacob H.
Published: May 2010

In order to understand the increase in pressure drop in hydrotreating reactors due to deposition of fine solids, experiments were conducted with a model suspension of kaolin clay in kerosene. The suspension was circulated through packed beds of catalyst pellets in the trickle‐flow and pulse‐flow regimes, and the increase in pressure drop measured as a function of particle concentration in the bed. The increase in pressure drop was linear with particle concentrations over the range 0–60 kg.m−3. A consistent approach to modeling the pressure drop behavior was to determine an effective porosity of the packed bed as a function of the concentration of fine particles, then use this porosity in the Ergun equation as a basis for calculating the two‐phase pressure drop.
Free convective mass transfer at horizontal single screens and arrays of horizontal screens in relation to electrochemical reactor design
Authors: Sedahmed Gomma H. , Nirdosh Inder
Published: May 2010

Rates of free convection mass transfer at horizontal screens made of woven cylindrical wires were studied by measuring the limiting current of copper deposition from acidified copper sulphate solutions for a horizontal screen surrounded by a cylindrical counter‐electrode. Variables studied were screen characteristic parameters and the physical properties of solutions. The data were correlated by a new mass transfer correlation. Mass transfer measurements at arrays of separated horizontal screens revealed that screen spacing has a little effect on the rate of array mass transfer. On the other hand, increasing the number of screens per array was found to decrease the rate of array mass transfer. Implications of the present results for the design and operation of electrochemical reactors suitable for heavy metal removal from waste water and electrosynthesis are noted.
Effects of O2 on aqueous SO2 leaching of Co, Cu and Ni from discard smelter slag
Authors: Ahmed Isaac B. , Gbor Philip K. , Jia Charles Q.
Published: May 2010

In the leaching of non‐ferrous smelter slag with a dissolved gas mixture of SO2 and O2, the behaviour of Co, Cu, Ni, Zn and Fe was studied in a 1‐L batch reactor. The parameters investigated include PSO2, PO2, temperature, particle size and pH. Co, Zn and Fe behaved similarly while Ni and Cu displayed distinguishable characters. The addition of O2 prevented the precipitation of Cu after dissolution, and increased acidity of the leaching solution. The increase in acid strength resulted in an increase in the extraction of Co, Zn and Fe. The effect of acidity on Cu and Ni extraction was however much weaker. The combination of SO2 and O2 was found to be a more effective oxidant of Fe(II) to Fe(III) than O2 alone. Simultaneous extraction of valuable metals and removal of Fe could be achieved by leaching at pH of 3 to 4. Maximum selectivities obtained for Co, Ni and Cu over Fe were 300, 2000 and 4000, respectively.
Modeling of a process for removal of metal ions by electromigration and electrodeposition
Authors: Mondal Kanchan , Pattanayak Jayasree , Wiltowski Tomasz S. , Lalvani Shashi B. , Mandich Nenad V.
Published: May 2010

A mathematical model for the removal of impurities of the metal ions of Fe, Ni, and Cu from hard chromium plating solution by electromigration and subsequent electrodeposition has been developed and presented. Experimental data for the metal removal at 45°C and constant cell voltage using o‐phosphoric acid as the catholyte are presented. Up to 36% iron and 29% nickel removal is obtained over about 25 h. The copper removal rate is observed to be approximately four times greater than the rate of nickel removal. The experimental data were found to closely match results predicted from the model developed. The inherent model parameters such as mobility, diffusivity, mass transfer coefficient and metal deposition rate constants were estimated. The calculated values of these parameters are found to be in good agreement with the published data.
z‐Transform and adaptive signal processing in analysis of tracer data
Authors: Furman Leszek
Published: May 2010

In the field of data processing, the common practice is to interpret tracer‐determined residence time distributions (RTDs) of particles through different arrangements of elementary flow models. However, such analysis needs an a priori chosen arrangement of these models, and some information carried by the RTD curve may be lost. This paper presents a competitive method based on adaptive filtering in a z‐transform domain, and it may give better insight into flow patterns in a steady‐state flow system. A physical interpretation of the transfer function was developed. The application of this modelling to the interpretation of radiotracer data from recent studies in different industry sectors is presented.
Distribution of the free and oil‐trapped air bubbles in simulated broths containing fungal biomass
Authors: Larralde‐Corona C. Patricia , Córdova Ma. Soledad , Galindo Enrique
Published: May 2010

The location of air bubbles (i.e. inside oil drops or free in the aqueous phase) was studied by image analysis as a function of the oil and biomass concentrations in a 2 L stirred tank using a simulated fermentation medium (aqueoussalt solution, castor oil, air and fungal biomass) agitated by a Rushton turbine. The solid (fungal) phase plays an important role in defining the location of bubbles, as the percentage (in bubble volume) of bubbles trapped in oil increases threefold when biomass is added to the medium. The bubbles located inside oil drops were found to occupy 60% of the total bubble volume and to be 40% smaller than those which were non‐oil associated. This phenomenon has important implications for oxygen mass transfer in multiphase fermentations.
Linear viscoelasticity and stress growth in blood
Authors: Sun Ning , De Kee Daniel
Published: May 2010

This note complements a previous publication where we used first order kinetics to describe biofluid behavior, especially blood, in the cases of simple shear flow, hysteresis and yield stress. Here, we extend the model and consider the viscoelastic properties of blood. Specifically, we look at small amplitude oscillatory flow and stress growth. Successful comparisons of model predictions with blood data are produced.
A novel technique for local mass transfer measurements
Authors: Trass Olev , Mahinpey Nader , Ojha Matadial , Johnston K. Wayne
Published: May 2010

A novel electrodeposition technique is developed to estimate time‐averaged convective local mass transfer coefficients. This method is based on the diffusion‐controlled deposition rate of copper. With an electrolyte solution consisting of H2SO4 and CuSO4, copper is dissolved at the anode and deposited onto the nickel cathode. The thickness of the copper, measured with an optical microscope, provides an estimate of the time‐averaged local mass transfer coefficient for the given location, and by depositing multiple layers, the coefficients under different flow conditions can be obtained from one cathode. The results for laminar flow in a smooth, round pipe showed good agreement with those calculated from the analytical Leveque solution. Results were also obtained for turbulent flow and demonstrate the potential for acquiring convective local mass transfer coefficients for various flow configurations.