bluuebunny/crossref_metadata_2025_split huggingface dataset:
Review on Mixing Characteristics in Solid‐Liquid and Solid‐Liquid‐Gas Reactor Vessels
Authors: Kasat Gopal R. , Pandit Aniruddha B. 
Published: July 2010

AbstractMechanically agitated reactors with single and multiple impeller systems are used in the industry for the various three‐phase mixing processes such as crystallization, fermentation, and hydrogenation, etc. The paper reviews the experimental work reported in the literature along with different techniques used for the measurement of the specific quantities such as minimum or critical impeller speed for solid suspension. The work critically surveys the literature and makes specific recommendations for the use of appropriate correlations and conditions to be used for the success of such equipment. This assessment will put all the relevant literature on a common footing and will help to validate work reported earlier.
Dibenzothiophene HDS Over Sulphided CoMo on High‐Silica USY Zeolites
Authors: Lara Gerardo , Escobar José , De Los Reyes José A , Barrera María C. , Colín José A. , Murrieta Florentino R. 
Published: July 2010

AbstractUSY faujasites (SiO2/Al2O3 = 12, 30 and 80) were used as hydrodesulphurization (HDS) catalyst supports. Mo, Co and P were impregnated at two concentrations: ∼12.5, ∼3 and ∼1.6 mass %; ∼18, ∼5.5 and ∼2.2 mass % (CL and HL series, respectively). Surface acidity decreased after Co‐Mo‐P deposition. Sulphided catalysts were tested in dibenzothiophene (DBT) HDS (320°C, 5.59 MPa). The HDS rate slightly increased with both SiO2 content and Co‐Mo‐P loading. High selectivity to hydrogenated products suggested deficient Mo promotion in CL solids. Improved Mo promotion by Co (HL series) could be responsible for higher activity and marked selectivity to desulphurization to biphenyl.
Viscoelastic (Non‐Fickian) Diffusion
Authors: De Kee D. , Liu Q. , Hinestroza J. 
Published: July 2010

AbstractThis review paper deals with mass transport in macromolecular materials. The study of mass transport through polymeric composite materials for example has applications in a variety of areas such as coatings, packaging and gas separations, to name just a few. Here we discuss several models for diffusion as well as several experimental techniques. In particular, we discuss models for case II diffusion, from a continuum mechanics point of view as well as via a mesoscopic theory. Variables such as temperature, molecular structure and mechanical deformation, affecting mass transport are also discussed.
Geometrical Models for Tortuosity of Streamlines in Three‐Dimensional Porous Media
Authors: Yun Meijuan , Yu Boming , Xu Peng , Wu Jinsui 
Published: July 2010

AbstractBased on the assumption that some particles in porous media are unrestrictedly overlapped and hence of different configurations, this paper presents three three‐dimensional geometry models for tortuosity of streamlines in porous media with spherical, cubic and plate‐like particles, respectively. The proposed models are expressed as a function of porosity with no empirical constant, and they are helpful for understanding the physical mechanism for tortuosity of flow paths in three‐dimensional porous media. The model predictions are compared with those from the available correlations obtained by experimental data, and good agreement is found between them.
Cometabolic Transformation of 2‐Chlorophenol and 4‐Chlorophenol in the Presence of Phenol by Pseudomonas putida
Authors: Loh Kai‐Chee , Wu Tingting 
Published: July 2010

AbstractBiotransformation of 2‐chlorophenol (2‐cp) and 4‐chlorophenol (4‐cp) in the presence of phenol by Pseudomonas putida (ATCC 49451) was investigated. Strain ATCC 49451 was unable to utilize 2‐cp and 4‐cp as the sole carbon and energy source. In the presence of phenol as a growth substrate, 2‐cp and 4‐cp could be transformed through cometabolism. It was found, however, that cell growth and phenol degradation were strongly inhibited by the presence of 2‐cp and 4‐cp. A much longer lag phase (19 h versus 3 h) occurred with the mere addition of 40 mg/L 2‐cp and 100 mg/L 4‐cp. Further increase in 2‐cp and 4‐cp concentrations resulted in incomplete transformation: only 80% of the initial 100 mg/L 4cp and 50% of the initial 40 mg/L 2‐cp could be degraded in the presence of 200 mg/L phenol. Interactions between substrates affected cell growth and substrates degradation significantly and both 2‐cp and 4‐cp were toxic to the cells. Kinetic models for cell growth as well as substrate transformation were established to simulate the experimental data. The form of the kinetic models and magnitude of the model parameters (K2 = 5.62 mg/L > K3 = 3.57 mg/L; kd2 = 17.8 mg/L < kd3 = 51.5 mg/L) indicate that 2‐cp and 4‐cp exhibited different inhibition and toxicity effects on the cells and their degradation capacities. Kinetics also revealed that the toxicity effect of the chlorophenols dominated over the competitive inhibition effect.
A Short Note on Steady State Behaviour of a Petlyuk Distillation Column by Using a Non‐Equilibrium Stage Model
Authors: Abad‐Zarate Erika Fabiola , Segovia‐Hernández Juan Gabriel , Hernández Salvador , Uribe‐Ramírez Agustín R. 
Published: July 2010

AbstractA Petlyuk distillation column, considering equilibrium and non‐equilibrium stage models, was studied. Rigorous simulations were conducted using Aspen Plus™ RATEFRAC Module for the separation of ternary mixtures. According to the equilibrium model, the energy‐efficient design of the Petlyuk column requires that the intermediate component be extracted from the maximum point in the composition profile in the main column. It was found that, for the intermediate component, mass transfer occurs from the vapour to the liquid phase from the top of the column to the stage where the side stream is extracted, from this point mass transfer occurs in the opposite direction. This point, considering the non‐equilibrium model, corresponds to the stage in which the net mass transfer rate is zero. For the case of two segments per stage, it was found that the heat duties predicted by the equilibrium model are significantly lower than those obtained by using the non‐equilibrium model, which is consistent with previous reported results. However, it is important to say that despite the higher energy duty predicted by the non‐equilibrium model; both models predict significant energy savings.
Comparison of Antioxidant Activity of Ethanolic Extracts of Propolis Obtained by Different Extraction Methods
Authors: Jun Xi 
Published: July 2010

AbstractThe antioxidant activities of the ethanolic extracts of propolis obtained by different extraction methods (high hydrostatic pressure extraction, leaching at room temperature and heat reflux extraction) were investigated in relationship to their total polyphenol and flavonoid contents by two different assays, namely, the β‐carotene bleaching and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical scavenging assay systems. The results showed that the ethanolic extracts of propolis obtained by high hydrostatic pressure extraction and leaching at room temperature had relatively strong antioxidant activities, which may be correlated with the total polyphenol and flavonoid contents. Antioxidant activities of ethanolic extracts of propolis obtained by high hydrostatic pressure extraction were the same as those of ethanolic extracts of propolis obtained by leaching at room temperature. Leaching at room temperature usually needs a few days, and can take even more than 7 d, while high hydrostatic pressure extraction needs only 1 min. These findings further illustrate that the high hydrostatic pressure extraction has a bright prospect for extracting flavonoids from propolis.
Mass Transport Through PDMS/Clay Nanocomposite Membranes
Authors: Liu Quan , de Kee Daniel 
Published: July 2010

AbstractPoly(dimethylsiloxane)/clay nanocomposite membranes have been synthesized and mass transport properties through those nanocomposite membranes have been investigated. The effect of mechanical deformation on the transport properties of the PDMS (nanocomposite) membranes has also been studied. With the introduction of clay particles into the polymer matrix, mass transport is reduced, likely due to the longer diffusion path, which slows the diffusion process. The effect of membrane extension on diffusion is more complicated. Under small deformation, the permeation flux decreases, but under high deformation, it shows an enhanced diffusion. As the clay particle concentration increased, the effect of external deformation is reduced, and an enhanced diffusion is observed.
Association Equation of State for Hydrogen‐Bonded Substances
Authors: Vafaie‐Sefti Mohsen , Modarress Hamid , Meibodi Majid Emami , Mousavi‐Dehghani Seyyed Ali 
Published: July 2010

AbstractAn association equation of state (AEOS) has been proposed for hydrogen‐bonded compounds. To obtain this AEOS, the compressibility factor was assumed to consist of two parts: the physical part due to physical interactions of molecules; and the chemical part due to molecular association by hydrogen bonding of molecules. The physical part of the compressibility factor was represented by the MMM EOS for non‐polar compounds proposed by Mohsen‐Nia et al., Fluid Phase Equilib. 206, 27‐39 (2003), and the chemical part of the compressibility factor was deduced by proposing a molecular association model of infinite series.
A Simple Modification of the Pitzer Method to Predict Second Virial Coefficients
Authors: Vetere Alessandro 
Published: July 2010

AbstractA simple modification of the Pitzer relation to calculate second virial coefficients of polar compounds is proposed. The proposed modification is based on the use of a new parameter, β, which embodies both the contributions of acentricity and polarity to second virial coefficient values. The analytical form of the Pitzer relation is preserved and its performances are improved. Rules are given to calculate β for several classes of compounds which require only the knowledge of a few well known properties of pure compounds. A comparison between the new method and the Pitzer‐Tsonopoulos relation is made on the basis of the experimental Bi data of nearly 50 compounds.
Frictional Pressure Drop of Air Non‐Newtonian Liquid Flow through Helical Coils in Horizontal Orientation
Authors: Biswas Asit Baran , Das Sudip Kumar 
Published: July 2010

AbstractInvestigations have been carried out to evaluate the two‐phase frictional pressure drop for air non‐Newtonian liquid flow through helical coils in horizontal orientation. The experiments performed using 36 different helical coils and 4 different concentrations of sodium salt of carboxymethyl—cellulose (SCMC) as non‐Newtonian liquids. The effects of air and liquid flow rate, coil diameter, helix angle and liquid properties‐ on two‐phase frictional pressure drop have been discussed. An attempt has been made to fit the experimental two‐phase frictional pressure drop data by the Lockhart and Martinelli, Chem. Eng. Prog. 45, 39–48 (1949) correlation and the modified Lockhart‐Martinelli correlation as presented by different authors. In another approach, friction factor method was adopted to correlate the experimental data by dimensional analysis. The correlation developed predicts the two‐phase frictional pressure drop with acceptable statistical accuracy.
Detection and Diagnosis of Plant‐Wide Oscillations
Authors: Shoukat Choudhury M. A. A. , Kariwala Vinay , Thornhill Nina F. , Douke Hisato , Shah Sirish L. , Takada Haruo , Forbes J. Fraser 
Published: July 2010

AbstractThis paper presents some emerging techniques for detection and root‐cause diagnosis of plant‐wide oscillations, and demonstrates their efficacy through a successful industrial case study. The recently proposed autocorrelation function based method (Thornhill et al., J. Proc. Control 13, 91–100, 2003a) is used for detection of oscillations in the process measurements. Signals having common oscillations are analyzed for the presence of valve stiction using higher order statistical methods (Choudhury et al., Automatica 40, 1719–1728, 2004b). A method employing changes in controller gain is proposed for distinguishing an internally generated oscillation from an external oscillatory disturbance. This method of changing controller gain is used to confirm the presence of control valve stiction. The proposed techniques have been used successfully to identify the root cause of plant‐wide oscillations in an industrial case study using routine operating data.
Miscibility Determination from Gas‐Oil Interfacial Tension and P‐R Equation of State
Authors: Ayirala Subhash C. , Rao Dandina N. 
Published: July 2010

AbstractRecently a new experimental technique of vanishing interfacial tension (VIT) has been developed to enable rapid and cost‐effective determination of miscibility in gas‐oil systems. In this study, VIT experiments have been extended to two standard gas‐oil systems of n‐decane‐CO2 and live decane‐CO2 at elevated pressures and temperatures. The VIT miscibilities of the two standard gas‐oil systems and the two reservoir crude oil‐gas systems, namely Rainbow Keg River (RKR) and Terra Nova, were compared with Peng‐Robinson (P‐R) equation of state (EOS) calculations. The close match of VIT miscibilities with other conventional experimental techniques in the standard gas‐oil systems, as well as the reasonable match obtained with untuned PR‐EOS calculations for several systems studied, clearly demonstrates the sound conceptual basis of VIT technique to determine fluid‐fluid miscibility in multi‐component hydrocarbon systems.
Modelling Gas Holdup in Flotation Column Froths
Authors: Bhole Manish R. , Joshi Jyeshtharaj B. 
Published: July 2010

AbstractA one‐dimensional steady‐state model is developed for the prediction of axial variation of the gas holdup in flotation column froths. Froth is considered as an inverse fluidized bed of bubbles and hence the frictional pressure gradient is obtained based on the energy balance. Pressure gradient can also be obtained from the Ergun equation with adjustable constants. The model correctly captures the effect of superficial gas velocity, superficial liquid velocity and bubble diameter on the variation of the gas holdup along the froth height. The predictions of the model are in agreement with the experimental data from the literature.
The Use of Simplified or Misspecified Models: Linear Case
Authors: Wu Shaohua , Harris T. J. , Mcauley K. B. 
Published: July 2010

AbstractSimplified models have many appealing properties and sometimes give better parameter estimates and model predictions, in sense of mean‐squared‐error, than extended models, especially when the data are not informative. In this paper, we summarize extensive quantitative and qualitative results in the literature concerned with using simplified or misspecified models. Based on confidence intervals and hypothesis tests, we develop a practical strategy to help modellers decide whether a simplified model should be used, and point out the difficulty in making such a decision. We also evaluate several methods for statistical inference for simplified or misspecified models.
On‐Line Feedback Control for Optimal Periodic Control Problems
Authors: Höffner Kai , Hudon Nicolas , Guay Martin 
Published: July 2010

AbstractIn this paper a method for generating periodic orbits for a class of non‐linear systems is presented. A periodic Hamiltonian system is defined as the target equilibrium for non‐linear systems in strict feedback form. A parameter dependent non‐linear periodic system description is introduced for a two‐dimensional subsystem and extended to higher dimensions using backstepping. Extremum seeking is used as a parameter update law that guarantees the convergence of the system to the optimal periodic orbit with respect to a given parameterization. The procedure resulted in an on‐line feedback control implementation that typically steers the system to a suboptimal solution that nevertheless improves the static optimization solution. Typical examples from optimal periodic control literature are used to illustrate the application of this approach.
Simulation‐Based Design of Dual‐Mode Controller for Non‐Linear Processes
Authors: Lee Jong Min , Lee Jay H. 
Published: July 2010

AbstractThis paper presents a simulation‐based approach for designing a non‐linear override control scheme to improve the performance of a local linear controller. The higher‐level non‐linear controller monitors the dynamic state of the system and calculates an override control action whenever the system is predicted to move outside an acceptable operating regime under the local controller. The design of the non‐linear override controller is based on a cost‐to‐go function, which is constructed by using simulation or operation data. The cost‐to‐go function delineates the admissible region of state space within which the local controller is effective, thereby yielding a switching rule.
Approximate Pole Placement with Dominance for Continuous Delay Systems by PID Controllers
Authors: Wang Qing‐Guo , Liu Min , Hang Chang Chieh 
Published: July 2010

AbstractIt is well known that a continuous‐time feedback system with time delay has infinite spectrum and it is not possible to assign such infinite spectrum with a finite‐dimensional controller. In such a case, only the partial pole placement may be feasible and hopefully some of the assigned poles are dominant. But there is no easy way to guarantee dominance of the desired poles. In this paper, an analytical PID design method is proposed for continuous‐time delay systems to achieve approximate pole placement with dominance. Its idea is to bypass continuous infinite spectrum problem by converting a delay process to a rational discrete model and getting back continuous PID controller from its discrete form designed for the model with pole placement. Simulation results are included to illustrate the effectiveness of this method.
Kinetics of Colloidal Particle Deposition to a Solid Surface from Pressure Driven Microchannel Flows
Authors: Unni H. N. , Yang C. 
Published: July 2010

AbstractKinetics of colloidal particles deposition onto a solid surface in hydrodynamic flows was studied. A phenomenological mathematical model was presented to analyze the particle deposition from pressure‐driven flows in a parallel‐plate microchannel. The two‐dimensional mass transport equation incorporating hydrodynamic convection, particle diffusion, gravity force and DLVO colloidal forces (i.e., the van der Waals and electrical double‐layer forces) was solved numerically using a finite difference method to obtain the dimensionless particle deposition rates expressed by the Sherwood number. The numerical predictions of the Sherwood number were compared with the results of videomicroscopic experiments conducted under various physicochemical conditions including electrolyte concentration, particle size and hydrodynamic flow intensity in terms of the Reynolds number, and reasonable good agreement was found.
Hydrodynamic Cell Model: General Formulation and Comparative Analysis of Different Approaches
Authors: Zholkovskiy Emiliy K. , Shilov Vladimir N. , Masliyah Jacob H. , Bondarenko Mykola P. 
Published: July 2010

AbstractThis paper is concerned with the Cell Model method of addressing hydrodynamic flow through system of solid particles. The starting point of the analysis is the general problem formulation intended for describing a pressure driven flow through a diaphragm which can be considered as a set of representative cells having arbitrary shape and containing any number of particles. Using the general problem formulation, the hydrodynamic field inside an individual representative cell is interrelated with the applied pressure difference and the external flow velocity. To this end, four relationships containing integrals over the outer boundary of a representative cell are derived in the paper. Assuming that the representative cell is a sphere containing a single particle in the centre, the derived general relationships are transformed into outer cell boundary conditions employed in the literature by different authors. The general number of the obtained outer boundary conditions is more than the required number. Accordingly, by choosing different sets of the outer boundary conditions, different models are considered and compared with each other and with the results obtained by others for regular particle arrays. The common and different features of the hydrodynamic and electrodynamic versions of the Cell Model approaches are analyzed. Finally, it is discussed which version of the cell model gives the best approximation while describing pressure and electrically driven flows through a diaphragm and sedimentation of particles.
The Limits of Fine and Coarse Particle Flotation
Authors: De F. Gontijo Carlos , Fornasiero Daniel , Ralston John 
Published: July 2010

AbstractThe flotation behaviour of quartz particles was studied over the particle size range from 0.5 µm to 1000 µm and for advancing water contact angles between 0° and 83°. Flotation was performed in a column and in a Rushton turbine cell. Particle contact angle threshold values, below which the particles could not be floated, were identified for the particle size range 0.5–1000 µm, under different hydrodynamic conditions. The flotation response of the particles, either in a column or in a mechanically agitated cell with a similar bubble size, was comparable. Turbulence plays a role, as does bubble‐particle aggregate velocity and bubble size. The stability of the bubble‐particle aggregate controls the maximum floatable particle size of coarse particles. For fine particles, the flotation limit is dictated by the energy required to rupture the intervening liquid film between the particle and bubble. Flotation of very fine and large particles is facilitated with small bubbles and high contact angles. These results greatly extend our earlier observations and theoretical predictions.
Role of Pressure in Coking of Thin Films of Bitumen
Authors: Gray Murray R. , Le Tuyet , Wu Xin A. 
Published: July 2010

AbstractAn important step in the formation of product from feed in a fluidized‐bed coker is the evolution of product and coke from layers of vacuum residue on the surfaces of heated particles and from liquid inside agglomerates of liquid and solid. In the present study, the yield of coke from Athabasca vacuum residue was measured using a reactor based on rapid induction heating of thin films of liquid feed on the surface of pieces of Curie‐point alloy. This approach allowed measurement of the yield of coke at pressures from 101–652 kPa, temperatures of 503 and 530°C, and reaction times from 10 to 240 s. When the liquid was reacted in thin films of ca. 20 µm, the effects of temperature and pressure on coke yield were insignificant. As the film thickness was increased to 120 µm, the yield of coke increased at all conditions. The yield of coke from thicker films was only sensitive to total pressure at 503°C reaction temperature, when the pressure was increased from 377 kPa to 652 kPa. Observable bubbling due to cracking reactions during coking was suppressed by increasing pressure, and the transition from quiescent liquid to bubbling liquid increased from circa 26 µm at 101.3 kPa to 78 µm at 652 kPa at 503°C. The bubbling transition was much less sensitive to pressure at 530°C, falling in the range from 22 µm to 43 µm as pressure increased from 101.3 to 652 kPa. These results suggest that the most important effect of pressure will be on the physical behaviour of liquid feed, due to its impact on bubble evolution from liquid inside agglomerates of liquid and solid particles. Depending on the liquid/solid ratio in an agglomerate, the formation of bubbles inside such a structure would make it weaker and easier to disperse on the fluidized bed reactor.