bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas—liquid dispersion and mixing characteristics and heat transfer in a stirred vessel
Authors: Xu G. J. , Li Y. M. , Hou Z. Z. , Feng L. F. , Wang K. 
Published: March 2009

AbstractProperties of gas—liquid dispersion and mixing of seven types of impellers were studied and compared in a stirred vessel with aeration. New correlations for the properties including critical dispersion impeller speed, dispersion regime, power consumption, gas hold‐up, discharge flow number and discharge efficiency have been developed.The fluid/wall heat transfer was also studied with several types of dual impeller combinations. There is a critical impeller speed which determines how aeration changes the heat transfer coefficient. Operating conditions influence heat transfer interactively by three factors, which can be expressed by proper dimensionless variables.
Modelling a circulating fluidized bed riser reactor with gas—solids downflow at the wall
Authors: Puchyr David M. J. , Mehrotra Anil K. , Behie Leo A. , Kalogerakis Nicolas E. 
Published: March 2009

AbstractA predictive model was developed for the fully developed zone of a circulating fluidized bed (CFB) riser reactor operating in the fast fluidization regime that overcomes limitations of existing models. The model accounts for the upward flow of gas and solids in the core and downward flow of the two phases in the annulus. Additionally, a numerical solution methodology for the simulation of a riser reactor employing the hydrodynamic model was devised. A simulation was performed using the fast, main Claus reaction to demonstrate the effects of backmixing in the fast fluidization regime. It was found that the molar flow rates of the reactants leaving a fast fluidized CFB riser reactor were significantly higher than those leaving an identical reactor operating in the pneumatic transport regime.
Investigation of coke extraction from zeolite‐HY under supercritical and near‐critical conditions
Authors: Niu Fenghui , Hofmann Hanns 
Published: March 2009

AbstractIn‐situ regeneration of deactivated catalysts by dissolving coke or coke precursors with supercritical reaction fluids is of important economical significance. Investigations of coke extraction on zeolite‐HY were performed in a gradientless reactor under supercritical and near‐critical conditions with ethylbenzene disproportionation as a test reaction and n‐butane or n‐pentane as inert. Experimental results illustrate the large ability of coke extraction under supercritical conditions. The influences of the experimental conditions on the ethylbenzene disproportionation and the coke extraction are discussed. Under appropriate supercritical conditions the coking and the coke extraction can reach an equilibrium, so that no further deactivation of the catalyst was observed. Several regularities about coke extraction on the surface of the catalyst are proposed.
Study on a cool storage system using HCFC (Hydro‐Chloro‐Fluoro‐Carbon)‐141B (CCI2 FCH3) (1, 1‐dichloro‐1‐fluoro‐ethane) clathrate
Authors: Tanii T. , Minemoto M. , Nakazawa K. , Ando Y. 
Published: March 2009

AbstractAn experimental study was performed to obtain design data for a cool storage system using HCFC‐141b (1, 1‐dichloro‐1‐fluoro‐ethane) clathrate, which is a more effective cool storage system than ice. The addition of a 0.05 mass% surfactant enabled HCFC‐141b clathrate formation/decomposition up to 40 mass% of clathrate concentration. The addition of ethylene glycol caused the clathrate formation/decomposition temperature to decrease, resulting in the acquisition of more cooled water.
Prediction of solubility for HFC working fluids in model substances for compressor oils
Authors: Wahlström åsa , Vamling Lennart 
Published: March 2009

AbstractThis study is a first step towards the prediction of the behaviour of working fluids and compressor oils. Different thermodynamic models are investigated and a modified Flory‐Huggins‐based predictive model, termed MFH, is proposed for solubility of HFCs in long‐chained hydrocarbons. From experimental data, 7 general parameters have been fitted for the MFH model to describe 14 binary systems. The UNIQUAC model demands 28 specific parameters without the possibility of extending their validity to other mixtures. A predictive UNIFAC model requires 8 general parameters, but its uncertainty, 17%. is poor compared to the MFH model's 7%.
Gas permeation and isobutane dehydrogenation over very thinPd/ceramic membranes
Authors: Shu J. , Grandjean B. P. A. , Kaliaguine S. , Ciavarella P. , Giroir‐Fendler A. , Dalmon J.‐A. 
Published: March 2009

AbstractAn attempt was made in this study to prepare very thin palladium membranes.Pdwas electrolessly deposited on the inner side surface of a mesoporous ceramic tube using a peristaltic pump to circulate the electroless solution through the tube. To obtain defect‐freePdmembranes, a two‐step deposition procedure from a dilutePd2+bath and a concentratedPd2+bath was practised with great care to avoid the difficulties associated with the mismatch of thermal expansion coefficients betweenPdand the ceramic substrate. The various membranes produced were characterized through a study of their permeation behaviors. A densePdmembrane about 2 μm thick was permselective to hydrogen. It was found that in this very thinPdmembrane case, the hydrogen permeation flux was better correlated to hydrogen pressure using a power higher than 0.5, showing deviation from Sieverts' law. To evaluate the efficiency of the prepared thinPd/ceramic membranes,iso‐butane dehydrogenation was used as a model reaction. Enhanced dehydrogenation yields were obtained in the membrane reactor due to the separation of hydrogen from the reaction medium.
Flow patterns in a pilot plant‐scale turbulent fluidized bed reactor: Concurrent application of tracers and fiber optic sensors
Authors: Farag H. I. , Grislingås A. , Ege P. E. , De Lasa H. I. 
Published: March 2009

AbstractHydrodynamics of a turbulent fluidized bed is studied by means of the concurrent application of fiber optic sensors and a helium tracer.It is observed that in the vicinity of the column wall there is a high bubble activity region. Low bubble activity and negative bubble velocities are reported for the dense phase near the column centre‐line region.A temperature increase from 22 to 145°C results in a more homogeneous turbulent fluidized bed with smaller bubbles and more gas flowing through an expanded dense bed emulsion phase.Mass transfer coefficients between bubble‐emulsion (kbe) and bubble‐annulus (kba) are evaluated. The dominant mass transfer path was the one from the bubbles to the annular region with kba being several times greater than kbe.
Methyl‐diethanolamine degradation — Mechanism and kinetics
Authors: Chakma A. , Meisen A. 
Published: March 2009

AbstractMethyl‐diethanolamine (MDEA) degradation reactions between aqueous solutions of MDEA and CO2 have been carried out in a 600 mL stirred autoclave under the following conditions: initial MDEA solution concentration 20‐50 mass%, solution temperature 100‐200°C, CO2 partial pressure 1.38‐4.24 MPa. It was found that MDEA degrades quite rapidly (although more slowly than diethanolamine under comparable conditions) at elevated temperatures and CO2 partial pressures. Degradation products are identified by gas chromatography and mass spectrometry (GC/MS). An MDEA degradation reaction mechanism and kinetic model predicting concentration changes is proposed and verified.
Mass transfer in horizontal flow channels with thermal gradients
Authors: Bendrich Guido , Shemilt Leslie W. 
Published: March 2009

AbstractMass transfer to a wall of a horizontal rectangular channel reactor was investigated by the limiting current technique for Reynolds numbers ranging from 200 to 32000. Overall mass transfer coefficients at various mass transfer surface angles were obtained while the reactor was operated under isothermal and non‐isothermal conditions. Dimensionless correlations were developed for isothermal flows from 25 to 55°C and for non‐isothermal flows with applied temperature differences up to 30°C. In the laminar flow range natural convection dominated, but under turbulent conditions combined natural and forced convection prevailed. Mass transfer was approximately doubled under optimum selection of channel surface rotation, temperature gradient and flow rate.
Nucleation site density in pool boiling of binary mixtures: Effect of surface micro‐roughness and surface and liquid physical properties
Authors: Benjamin R. J. , Balakrishnan A. R. 
Published: March 2009

AbstractThe nucleation site density (N/A) during pool boiling of binary mixtures has been experimentally examined in terms of the heating surface physical properties, the liquid physical properties, the vapour liquid equilibria and the surface micro‐roughness. The liquid mixtures used were acetone ‐ carbon tetrachloride and n‐hexane ‐ carbon tetrachloride. A parameter Ra, to characterize the micro‐roughness of the heating surface was defined as the average value of the peaks and valleys on the surface. The study shows that while at low Ra, values the physical properties of the liquid and the binary composition are not as important as the surface roughness; at higher Ra values the liquid properties and composition are also important. A correlation based on the present data has been proposed.
Alkaline cupric oxide and nitrobenzene oxidation of alcell® lignin
Authors: Hepditch Mona M. , Thring Ronald K 
Published: March 2009

AbstractA solvolysis lignin has been oxidatively degraded using nitrobenzene and cupric oxide (CuO) as catalysts. The effects of reaction conditions on lignin conversion to identifiable low molecular weight liquid products were quantified. Optimal yields of vanillin and syringaldehyde of 2.2 wt % and 5.9 wt % respectively were obtained using nitrobenzene at 180°C and 2h, whereas both were less than 1 wt % when CuO was used at 225°C and 1h, indicative of the milder oxidative power of CuO for this lignin. The higher total aldehyde yield from solvolysis lignin (8.2 wt %) than kraft lignin (5.1 wt %) when using nitrobenzene indicates it might be a better candidate for producing chemicals via oxidation.
The marangoni effect and enhanced oil recovery Part 2. Interfacial tension and drop instability
Authors: Lyford P. A. , Shallcross D. C. , Pratt H. R. C. , Grieser F. 
Published: March 2009

AbstractA computer‐based method is described for the determination of the interfacial tension between pendant and sessile drops in a surrounding continuous phase. This has been used to determine the effect on interfacial tension of increasing amounts of aliphatic alcohols, from methanol up to n‐octanol, equilibrated between a hydrocarbon solvent (Shellsol) and water. The results indicated large decreases in interfacial tension, with n‐butanol, followed by n‐propanol giving the greatest reduction. Measurements were also made of the rate of change of interfacial tension during the mass transfer of 2.5% of the alcohols between phases. Changes were observed for all alcohols from ethanol to n‐pentanol, the effect being greatest for transfer into water drops and out of solvent drops. Application of the linear stability theory of Sørensen to these results failed to predict the observed instability for transfer into solvent drops.
The effect of chloride on the HClO2‐HOCl2 reaction in a 4.5 mol/L sulfuric acid solution
Authors: Yin G. , Ni Y. 
Published: March 2009

AbstractThe chlorous acid reaction with hypochlorous acid (chlorine) may be responsible for the chlorine dioxide formation in a methanol based chlorine dioxide generation process. In this paper, the reaction between chlorous acid and hypochlorous acid in a 4.5 mol/L sulfuric acid solution was studied. It was found that chlorine dioxide is generated only if chloride is present. The underlying mechanism associated with the effect of chloride on the reaction was discussed.
Enhancement of the retention performance of the poly(ethylene oxide) — tannic acid system by poly (diallyldimethyl ammonium chloride)
Authors: Khoultchaev K. H. , Pang P. , Kerekes R. J. , Englezos P. 
Published: March 2009

AbstractThe retention performance of the poly(ethylene oxide) (PEO) and tannic acid (TA) dual system was studied in the presence of poly(diallyldimethyl ammonium chloride) (PDADMAC). The zeta potential, and size of the association complex between PEO and TA in the presence of PDADMAC as well as the infrared spectra of TA and the PEO‐TA system were also studied. It was shown that hydrogen bonds are formed between the phenolic and acidic groups of TA and the oxygen atoms of the PEO macromolecules. Moreover, it was found that the presence of small quantities of PDADMAC enhances the fibre fines and clay first pass retention. The maximum effect was observed with an amount of added PDADMAC equal to 20% of the amount of added PEO. Further addition of PDADMAC was found to decrease the retention probably because it re‐charges the surface to positive. When clay was replaced by ground calcium carbonate no retention improvement was detected. This is most likely due to the presence of calcium ions.
Scale‐up of mixing in gassed multi‐turbine agitated vessels
Authors: Vasconcelos Jorge M. T. , Alves Sebastião S. , Nienow Alvin W. , Bujalski Waldemar 
Published: March 2009

AbstractA mixing model previously developed for the determination of mixing time in gassed tanks stirred by multiple Rushton turbines (Vasconcelos et al., 1995) was verified for the additional scales of 0.39, 0.56 and 0.72 m vessel diameter. It is now shown that the single adjusted parameter previously required by the model, the air‐induced axial velocity parameter vax, is scale‐independent with an invariant value of 7 × 10−2 m/s. Model simulations, with tank and turbine diameters and the number of stages as the only required parameters, deviate 5% on average from the experimentally determined mixing time t0.05. The model is thus a valuable tool for scale‐up of this type of vessels.
Averaged and time‐resolved, full‐field (three‐dimensional), measurements of unsteady opposed jets
Authors: Zhao Yang , Brodkey Robert S. 
Published: March 2009

AbstractFull‐field, time‐resolved, velocity vector information was obtained for an opposing jet reactor. The velocities were measured by particle tracking velocimetry (PTV) over a range of jet Reynolds numbers (200–5000). The main results reported are for a Reynolds number of 200. Graphical representation of the extensive data fields cannot be conveniently reported here; however, examples are provided. A more thorough presentation is possible by using color and dynamic representations and these are provided at the URL (Uniform Resource Locator, i.e., the address for a location on the Internet) cited in Zhao and Brodkey (1998). It is important to emphasize that the velocity fields presented in this paper are experimental.
Validation of CFD simulations of a stirred tank using particle image velocimetry data
Authors: Sheng Jian , Meng Hui , Fox Rodney O. 
Published: March 2009

AbstractMethods for validating CFD simulations based on the Reynolds Average Navier‐Stokes equation (RANS) against Particle Image Velocimetry (PIV) measurements are investigated and applied to one of the most common problems in the chemical process industry — the prediction of flow field in a stirred vessel. A total of 1024 sequential instantaneous 2D velocity fields along the central axial plane of a stirred vessel with a P‐4 axial impeller are obtained through PIV measurement. From the PIV data, the mean velocity, turbulent kinetic energy, Reynolds stresses and dissipation rate fields are extracted. By introducing several tools to quantify the similarities and differences between two‐dimensional fields, CFD predictions of the flow field are validated against PIV data. Furthermore, using PIV and LDV data, the effect of boundary conditions on CFD simulation results is examined. The effect of different Reynolds stress closures on the flow prediction is also studied.
Direct prediction of the flows induced by a propeller in an agitated vessel using an unstructured mesh
Authors: Naude Isabelle , Xuereb Catherine , Bertrand Joél 
Published: March 2009

AbstractThe direct simulation of impellers with complex geometrical shapes has not yet been presented. The unstructured mesh with a multiple reference frame approach has to be used to model the system with complete fidelity. The ability of a new CFD unstructured package is investigated in a cylindrical baffled tank stirred by an industrial LUMPP LB propeller in turbulent flow. Different positions of the blade relative to the side‐wall baffles have been computed to study the time‐dependent flow fields. The computational results compared favourably with experimental LDA data, with pumping number and power number, but a great care should be put on the mesh quality since results are extremely sensitive. It is concluded that the multiple reference frame approach is suitable to design impeller optimized for a given application.
Gas chromatography — mass spectrometric determination of unsymdimethylhydrazine in soil and water by derivatization with aromatic aldehydes
Authors: Cathum Shamil , Atamaniouk Vladimir , Ananieva Lioudmila , Ladanowski Caroline , Whittaker Harry 
Published: March 2009

AbstractA gas chromatography — mass spectrometric method for determination of unsymdimethylhydrazine (UDMH) in soil and water has been developed. The method is based on derivatization of UDMH with 2‐nitrobenzaldehyde, 4‐nitrobenzaldehyde, 4‐chlorobenzaldeyhde, 4‐cyanobenzaldehyde, 4‐dimethyaminobenzaldehyde, benzaldehyde and furfuraldehyde, followed by analysis of the derivative using gas chromatography — mass spectrometry. The effect of ambient air and antioxidants (pyrogallol and TiCl3) to absorb dissolved oxygen from the reagents has been investigated. The method proves to be useful for UDMH analysis in soil and water, and has been used for environmental site assessment at a former missile base in Ukraine.
RTD studies in trickle bed reactors packed with porous particles
Authors: Saroha Anil K. , Nigam K. D. P. , Saxena Alok K. , Dixit Lalji 
Published: March 2009

AbstractThe residence time distribution (RTD) for liquid phase in a trickle bed reactor (TBR) has been experimentally studied for air‐water system. Experiments were performed in a 15.2 cm diameter column using commerical alumina extrudates with D/dp ratio equal to 75 to eliminate the radial flow differences. The range of liquid and gas flow rates covered was 3.76 < ReL < 9.3 and 0 < ReG < 2.92. The axial dispersion model was used to compute axial dispersion coefficient. The effect of liquid and gas flow rates on total liquid holdup and axial dispersion was investigated. The total liquid holdup has been correlated to liquid and gas flow rates.
The kinetics of sorption of basic dyes from aqueous solution by sphagnum moss peat
Authors: Ho Y. S. , Mckay G. 
Published: March 2009

AbstractThe kinetics of sorption of three basic dyes, namely, Chrysoidine (BO2), Astrazon Blue (BB3) and Astrazone Blue (BB69) onto sphagnum moss peat have been investigated. The study focuses on the application of three sorption kinetic models for predicting the uptake of basic dyes. The sorption behaviour is found to be second order, based on the assumption of a pseudo‐second order mechanism. The rate constant of sorption, the equilibrium capacity and initial sorption rate with the effect of various peat doses and initial dye concentrations have also been predicted.
High concentrations ammonia removal by the cyanobacterium plectonema boryanum in a photobioreactor system
Authors: Prakash Anand , Margaritis Argyrios , Saunders Richard C. , Vijayan Sivaraman 
Published: March 2009

AbstractThe potential application of the cyanobacterium Plectonema boryanum was investigated for the removal of ammonia from aqueous solution to meet the target concentration of below 0.02 mg/L free ammonia. This method can be applied as a final polishing step in a series of wastewater treatment steps to reduce the ammonia concentration to drinking water levels. The experiments were conducted in a 2 L photobioreactor using batch and semi‐batch modes of operation. The effect of important growth parameters such as temperature, light intensity and pH were investigated to identify their relative significance in a batch photobioreactor. Concentrations of ammonia in aqueous samples were varied up to 420 mg/L to study ammonia removal rates and growth of the cyanobacterium. The ammonia removal rates and maximum growth rates of the cyanobacterium were calculated and compared with other studies reported in literature. Repeated fed‐batch experiments demonstrate the viability of the process to reduce free ammonia in aqueous solutions to less than 0.02 mg/L. The results of this study demonstrate the potential application of cyanobacteria technology for ammonia removal at 100 mg/L of total ammonia and greater.
A numerical study of steady incompressible newtonian fluid flow over a disk at moderate reynolds numbers
Authors: Munshi Basudeb , Chhabra Rajendra P. , Ghoshdastidar Partha Sarathi 
Published: March 2009

AbstractThe hydrodynamic behaviour of a single thin disk settling steadily, broad face‐wise, in an incompressible Newtonian fluid has been investigated by solving the Navier‐Stokes equations numerically using an iterative procedure. The finite difference method has been used to map out the complete flow domain in terms of the values of the stream function and vorticity. Finally, the drag coefficient was evaluated by considering the energy dissipation. Extensive results on drag for a disk of thickness to diameter ratio of 0.05 show excellent agreement with the experimental, as well as, previous scant numerical results in the range 1 ≤ Re ≤ 100.
A radial void fraction correlation for packed bed tubes
Authors: Mueller Gary E. 
Published: March 2009

AbstractThe radial void fraction distribution of equal sized spheres in cylindrical packed bed tubes with low diameter aspect ratios (1 ≤ D/d ≤ 2) is determined from the spheres' center coordinates, the local radial void faction and the radial positions within the tubes. A correlation that closely predicts the local radial void fraction at a radial position is determined from the radial void fraction distributions. The correlation is a function of the diameter aspect ratio and the radial position in the cylindrical packed bed tubes.
The modified dynamic model of a riser type fluid catalytic cracking unit
Authors: Malay Pathanjali , Rohani Sohrab , Milne Bruce J. 
Published: March 2009

AbstractThe dynamic model developed by Ali and Rohani (1997) to describe the transient behavior of a fluid catalytic cracking (FCC) unit is modified (i) to incorporate the effect of volumetric expansion of the feed and product gases flowing in the riser reactor (ii) to consider the enhancement of mass and heat transfer coefficients due to high turbulence in the regenerator and (iii) to model the reactor and stripper as a continuous stirred tank. The modified model is validated using steady‐state plant data from an industrial unit (Consumer's Co‐operative Refineries Ltd., Regina, SK) and the results are found to be in good agreement.
Application of dynamic pressure probe technique to characterize a circulating fluidized bed
Authors: Pärssinen Janne H. , Hagelberg Pasi , Eilos Isto , Aittamaa Juhani 
Published: March 2009

AbstractIn this study a small diameter dynamic pressure probe was used to measure the flow characteristics and the annulus thickness in a circulating fluidized bed. The nonhomogeities of fluidization in the vertical and radial directions have been measured and the results are presented in a new way, as dynamic pressure against time. The diagrams reveal that the flow can, under certain conditions, exhibit significant reversals in the core areas. Particle size distribution in the vertical direction was also studied by using the quick‐closing valve technique. The pilot scale riser was cylindrical and the particles were typical FCC catalyst.