bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotary cylinders: Transverse bed motion prediction by rheological analysis
Authors: Perron J. , Bui R. T. 
Published: March 2009

AbstractA method for predicting the transverse motion of a granular bed in a rotary cylinder is proposed, based on a non‐Newtonian rheological model of the pseudo‐plastic type, i.e. with a flow behaviour index (n) between 0 and 1. For a good simulation of bed motion, the model must be able to adequately reproduce the bed velocity profile in both the upper (downward flowing) and the lower (upward moving) zones. It is shown that to do so there is the need to adjust not only the consistency index K but even more importantly the flow behaviour index, n. The mass and momentum conservation equations are solved by the CFD code FLUENT. The model is applied to the simulation of the motion of an alumina bed and the computed results compared with experimental data.
A transport‐oriented approach to residence time distributions and two‐phase chemical reactors
Authors: Rumschitzki David S. 
Published: March 2009

AbstractThis paper focuses on two‐phase (e.g., fluid‐solid catalyst) chemical reactors where one phase participates in the feed and effluent, first order chemical reactions proceed in the other phase and linear, species‐dependent, interphase transport connects the phases. A class of reactors exists in which the Laplace transform of the dynamic reaction/interphase transport equations reduces to essentially that of an effective set of first order reactions amongst effluent phase species only, in an imaginary single phase reactor.This result bears on scale‐up: Since the imaginary reactor simply scales with the usual residence time distribution, so too do reactors of this class scale with its analog. This easily measurable analog turns out to be just the non‐adsorbing tracer experiment. Significantly, certain reactors outside of this class do not scale likewise, even with first order chemistry; an example illustrates.The class in question includes, but is not limited to, fixed bed and Berty (CSTR) reactors. The analysis allows design inferences for two‐phase reactors, including fluidized beds.
Sodium silicate as a coke inhibitor during naphtha pyrolysis
Authors: Ghosh Kalyan K. , Kunzru Deepak 
Published: March 2009

AbstractRates of coke formation during steam pyrolysis of naphtha have been investigated in a jet‐stirred reactor both for sodium silicate coated and uncoated Inconel 600 surfaces in the temperature range of 1078–1108 K. Coke formation rates were significantly reduced on sodium silicate coated plates due to the passivation of the metal surface. However, the coking rates gradually increased with successive decokings of the coated surface.
Multiplicity of solutions in the optimization of a bifunctional catalyst blend in a tubular reactor
Authors: Luus Rein , Dittrich Joaichim , Keil Frerich J. 
Published: March 2009

AbstractThe reaction scheme for the isomerization and hydrogenation of methylcyclopentane using bifunctional catalyst is considered in a tubular reactor. The aim is to maximize the concentration of benzene at the outlet of the reactor by choosing the optimal blend of the catalyst along the reactor. When the problem was attempted by nonlinear programming employing sequential quadratic programming, twenty‐five local optima were obtained from 100 random starting conditions. By using iterative dynamic programming in addition to the best two local optima obtained by nonlinear programming, the global optimum was also obtained.
Digital simulation of industrial steam reformers for natural gas using heterogeneous models
Authors: Elnashaie S. S. E. H. , Adris A. M. , Soliman M. A. , Al‐Ubaid A. S. 
Published: March 2009

AbstractA model is developed for industrial natural gas steam reformers with top‐fired and side‐fired furnance design. The one‐dimensional heterogeneous model for catalyst tubes takes into account the intra‐particle diffusion resistances. Two approximations are used for the computation of the effective diffusivities via the Stefan‐Maxwell equations. The two‐point boundary value differential equations for the catalyst pellets are solved by a novel efficient and modified orthogonal collocation technique. The performance of the model has been checked in the case of two industrial reformers used in the ammonia and methanol industries in Egypt and Saudi Arabia.
Behaviour and removal of fine particles in a liquid‐solid spouted bed consisting of binary mixtures
Authors: Ishikura T. , Tanaka I. 
Published: March 2009

AbstractIn a liquid‐solid spouted bed system containing coarse and fine particles, the entrainment and elutriation of the separated fines were investigated with reference to variations in the pressure drop through the bed. The effect of operating parameters on the velocity corresponding to the beginning of entrainment of fines (Ube) was examined and a dimensionless correlation was proposed.The effect of operating parameters on the elutriation rate coefficient of fines at liquid velocities larger than their terminal settling velocity (Ul) also was studied. An empirical equation was proposed for a column height above TDH, the height of freeboard at which the elutriation rate becomes constant. It was recognized that the elutriation phenomenon was closely related to the length of the stratified particle transport bed when the ascending velocity of the elutriable particles at the top of bed becomes constant.
Hydrodynamics of shallow, conical spouted beds
Authors: Choi Michael , Meisen Axel 
Published: March 2009

AbstractExperiments were conducted with shallow beds, in the presence of atomizing air injected into the base, under the following conditions: Particles — urea, sulphur coated urea, polyethylene, polyformaldehyde and polystyrene; particle diameters (dp) – 2.1 to 2.8 mm; cone angle – 60°; cylindrical bed diameter (D) – 0.24 and 0.45 m; bed height (H) – 0.24 to 0.40 m; orifice diameter (di) – 21 to 35 mm; main spouting air (Qs) ≤ 37 L(actual)/s; atomizing air (Qa) ≤ 0.87 L(actual)/s. The minimum spouting velocity is well represented by:Ums = 13.5 (2gH)0.5 (dp/D')1.17 (D'i/D')0.372 (H/D')−0.148 [(τp ‐ τ)/τ]0.289where D' and D'i denote the modified column and orifice diameter, respectively. Qa, which affects D'i, significantly influenced the air velocity in the spout, but not the pressure profiles in the annulus. Morgan and Littman's (1980) correlation could be adapted to predict the experimental pressure profiles in the annulus.
Catalytic cracking of tar in biomass pyrolysis gas in the presence of calcined dolomite
Authors: Vassilatos V. , Taralas G. , Sjöström K. , Björnbom E. 
Published: March 2009

AbstractThe possibility of decreasing the content of tar in the fuel gas obtained by biomass pyrolysis has been studied. Catalytic cracking of the tar in presence of dolomite was used. Dolomite showed a high catalytic activity. The overall effect of the dolomite is to increase the gas yield by decreasing the tar yield. The dolomite and the steam used seem to affect the amount of naphthalene produced. By adjusting both the amounts of catalyst and steam, we were able to decrease significantly naphthalene (13 mg/kg dry substance biomass) and amount of tar (164 mg/kg dry substance biomass).
Friction factors and bubble dynamics in polymer solutions
Authors: De Kee D. , Carreau P. J. 
Published: March 2009

AbstractThis work reports on bubble dynamics in polymer solutions of various rheological character. Relations between the friction factor and the Reynolds number are discussed and master curves based on the results of Kawase and Moo‐Young are presented and analyzed using two different viscosity expressions. The theoretical results overpredict the friction coefficient except at very high deformation rates. The surface tension is shown to affect the shape of the bubbles but not their velocity, except for bubble volumes smaller than 10‐7 m3.
Lectrochemical oxidation of oxalate in alkaline solutions
Authors: Marsen J. , Hinatsu J.T. , Smith J.W. , Foulkes F.R. 
Published: March 2009

AbstractExperimental results show that the electrochemical oxidation of oxalate in alkaline solutions at lead dioxide anodes can be achieved at conditions of much higher alkalinity than previously reported in the literature using other types of electrodes. The oxalate in solutions containing 0.05 mol/L ∽0.1 mol/L sodium oxalate was anodically oxidized to carbonate with high efficiency in the presence of up to ∽0.1 mol/L NaOH at 70°C by using lead dioxide anodes doped with silver and tin. The addition of small amounts of silver and tin (e.g., 0.06% by weight) to lead dioxide films significantly increases the oxalate oxidation currents and current efficiencies. These metals can be incorporated into the lead dioxide films by in situ oxidation of lead‐silver‐tin alloys. Although oxalate could not be electrochemically oxidized using lead dioxide electrodes at extremely high pH's (greater than ∽ 14), reduction of the oxalate concentration to less than about 0.04 mol/L could be achieved at greater than 50% current efficiency at pH's up to about 13.
The solubility of carbon dioxide and hydrogen sulfide in a 35 wt% aqueous solution of methyldiethanolamine
Authors: Jou Fang‐Yuan , Carroll John J. , Mather Alan E. , Otto Frederick D. 
Published: March 2009

AbstractThe solubility of hydrogen sulfide and carbon dioxide in an aqueous solution containing 35 wt% methyldiethanolamine (MDEA) (3.04 kmol/m3, 4.52 mol/kg) has been measured at 40° and 100°C at partial pressures of the acid gas up to 530 kPa. Some data for hydrogen sulfide in a 50 wt% solution of MDEA (4.38 kmol/m3, 8.39 mol/kg) were also obtained. Also, densities of CO2‐aqueous MDEA solutions were measured at 40°C.
A group‐contribution correlation for predicting the acentric factors of organic compounds
Authors: Han Buxing , Peng Ding‐Yu 
Published: March 2009

AbstractA group‐contribution correlation has been developed for the estimation of the acentric factors of organic compounds. The novelty of the proposed method is that it involves the use of only the structural information of the compounds. For the 219 substances considered in this study, the calculated results deviate from the literature values by an average error of 4.2%.
Iterative parameter estimation for extraction of crystallization kinetics of potassium chloride from batch experiments
Authors: Dash S. R. , Rohani S. 
Published: March 2009

AbstractExtraction of crystallization kinetics, the fundamental information which governs the performance of a crystallization process, is characterized by experimental difficulties in MSMPR and mathematical difficulties in batch crystallization. Here, a rigorous approach is taken to estimate kinetic parameters from a batch crystallizer. The two step LaxWendorff technique is adapted for the solution of the population balance in a batch crystallizer and an iterative self‐correcting least squares algorithm is implemented for the estimation of the kinetic parameters. The need for multi‐response estimation as opposed to single‐response from terminal CSD is demonstrated. The kinetics extracted are average ones, representing primary and secondary nucleation kinetics. It is found that the kinetic parameters estimated by multi‐response technique have a superior predictive capability as opposed to those obtained using the terminal CSD only. An advantage of the proposed algorithm is that the measurement of course of supersaturation, which is difficult to perform, is not required.
Entrance laminar flows of viscoplastic fluids in concentric annuli
Authors: Round G. F. , Yu S. 
Published: March 2009

AbstractDeveloping flows of generalized Bingham (Herschel‐Bulkley) fluids in concentric annuli were studied numerically. A control volume approach based upon an upwinding finite difference technique was used to solve the equation of motion. The results in terms of velocity and pressure drop profiles are shown graphically. Radius ratios of 0.02, 0.2, 0.4 and 0.6; power‐law indices (n) of 0.7, 1.0 and 1.2; generalized Bingham numbers of 5, 10 and 15 were investigated. At present, there are no experimental results with which to make comparisons. However, there are results for fully developed flows and comparison has been made with these. In all cases the agreement was good.
Pyrolysis of canmet coprocessing residue in argon/hydrogen plasma
Authors: El‐Naas M. H. , Munzm R. J. , Berk D. 
Published: March 2009

AbstractThe continuous pyrolysis of CANMET coprocessing residue in argon/hydrogen plasma was studied for the temperature range 2700 to 3670 K using an induction plasma torch. Hydrogen was injected into the argon plasma tailflame at molar concentrations ranging from 0 to 23 %. The residue was continuously fed in liquid form to a laboratory‐scale reactor specially built for the study. The residue flow rate ranged from 6 to 9 g/min. A maximum of 10% of the residue pyrolysed with up to 90 % conversion to gaseous hydrocarbons. The rate of residue pyrolysis and the rate of formation of the gaseous products were found to be strongly dependent on the rate of heat transfer at the residue surface. The only gaseous products detected were acetylene, ethylene and methane. Some soot was produced, but no liquid hydrocarbons were detected.
The effect of oxygen upon the kinetics of glucose oxidase inactivation
Authors: Venugopal Ramakrishnan , Saviue Bradley A. 
Published: March 2009

AbstractThe effect of oxygen upon the inactivation rate of glucose oxidase was studied. Tests on enzyme stability during catalytic turnover were conducted under a range of oxygen partial pressures. A standard activity assay was used to monitor changes in glucose oxidase activity.Studies revealed that oxygen influenced the inactivation of glucose oxidase. Inactivation rates during catalytic turnover ranged between 0.01143 +/‐ 0.0016 h‐1 under 10 kPa oxygen to 0.04879 +/‐ 0.0023 h‐1under 101 kPa oxygen. Statistically different inactivation rates were obtained at oxygen partial pressures of 10,15, 21, 51, and 76 kPa. The enzymatic turnover number decreased from 11.0 X 104 to 5.7 X 104when the oxygen partial pressure increased from 10 to 101 kPa, suggesting that enzyme utilization was most efficient at low oxygen partial pressures (<15 kPa).
A simple correlation for estimating viscosities of solutions of salts in aqueous, non‐aqueous and mixed solvents applicable to high concentration, temperature and pressure
Authors: Kumar Anil 
Published: March 2009

AbstractA new correlation is proposed to correlate the viscosities of salt solutions in aqueous, non‐aqueous solvents and their mixtures. The correlation involves two parameters i.e. solvation number and ion‐solvent interaction coefficient, which are well‐documented quantities in the literature. The proposed correlation has been examined on the experimental viscosity data of salt solutions in aqueous, non‐aqueous and their mixtures up to 473 K and 31 MPa pressure. The salts with various ionic charges were employed for testing the proposed correlation. Several non‐aqueous solvents like dimethyl sulphoxide, alcohols and formamide were included for the data regression. The viscosities of these solutions can be correlated to within 0.7%.
Size distribution of drops formed from nozzles in liquid‐liquid systems at velocities below jetting
Authors: Karagiannis Constantinos , Papageorgiou Dimitrios , Stamatoudis Michael 
Published: March 2009

AbstractThe size distribution of drops formed from four different diameter nozzles (d=l.O, 1.6, 2.6 and 3.5 mm) was measured over the flow rate range of 0.17 to 3.0 cm3/s (below jetting). Kerosene was used as the dispersed phase and distilled water was used as the continuous phase. The experimental drop size distributions were described adequately by the upper limit number and volume distributions. Plots of the maximum and the minimum diameters versus the mean diameter yielded straight line with slopes of 1.11 and 0.87, respectively.
Analysis of the stratified / nonstratified transitional boundary in horizontal and slightly inclined condensing flows
Authors: Nitheanandan T. , Soliman H M. 
Published: March 2009

AbstractA mechanistic model has been developed for determining the stratified boundary for condensing flows in horizontal and slightly inclined tubes. Two formulations, a complete and a simplified version are considered for the equilibrium liquid level. Good agreement is found between the two formulations and generalized results were derived from the simplified version of the model. From these results, the effect of condensation is shown to be equivalent to adding a small upward inclination in adiabatic gas‐liquid flow. The predicted transition line is compared with flow‐regime data of different fluid properties, tube diameters, and inclinations. The predictions agreed reasonably well with the data.
Relative Supersaturation Ratio and Separation Factor in Crystallization with High Pressure C02
Authors: Chang Chiehming J. , Liou Yuchung , Lan Wen‐Jen 
Published: March 2009

AbstractCrystallization in the presence of high pressure gas as antisolvent could be applied for the recovery of valuable compounds from liquid solution. A study of separation behavior is presented here for a mixture of anthracene (AN) and anthraquinone (AQ) in cyclohexanone (CX) expanded with a gaseous antisolvent, CO2. The pressure range was 0.1 to 12 MPa; the temperature was either 292 or 313K. Separation factors were obtained from the measured salted‐out yields and the supersaturation of each solute could be also obtained for this pressure‐tuning crystallization. The separation factor varies almost linearly with relative supersaturation ratio in the crystallization of anthracene‐anthraquinone from cyclohexanone and CO2.
Surface conditioning for potash electrostatic separation
Authors: Zhou G. , Moon K. 
Published: March 2009

AbstractA simple apparatus for measuring contact charge was set up and utilized to identify and evaluate some effective chemicals for increasing contact charge between potash components. TiCl4 and FeCl2 · 4H20 increase contact potential by unevently raising the surface work functions of NaCl and KCl, while octanoic acid increases this potential by lowering the NaCl surface work function and slightly raising the KCl surface work function. Combinations of these two types of chemicals produce excellent results. Repetition of contacts affects the contact charge. The relationship between the amount of contact and potash contact charge was investigated, as was the effect of hematite contamination of sylvite contact charge.
Kinetics and mechanism of the vapour phase nitroxidation of toluene over nickel oxide‐aluminium oxide catalyst
Authors: Prasad R. , Garg A. , Mathews S. 
Published: March 2009

AbstractThe kinetics of the oxidation of toluene by nitric oxide over nickel oxide‐aluminium oxide catalyst has been studied in the temperature range 280‐380°C. A rate equation Rn= ktptknPn I (k1P1 + knPn) was deduced, assuming a steady state involving a two‐stage irreversible oxidation‐reduction process. The model represented the data satisfactorily for the conversion of toluene to benzonitrile.
Kinetics of hydrogen reduction of sodium sulfate mixed with sodium titanate
Authors: Zou X. , Avedesian M. M. , van Heiningen A. R. P. 
Published: March 2009

AbstractThe hydrogen reduction kinetics of solid sodium sulfate mixed with sodium titanate are studied in a thermogravimetric system. The conversion‐time curves of the hydrogen reduction are sigmoidal in shape and are well described by the nucleation and growth model up to about 60% conversion. The reduction rate of this mixture is much faster than that of pure sodium sulfate. In the deceleratory conversion period, the reduction is controlled by gas diffusion through a product layer. Activation energies of 302 and 179 kJ/mol are obtained, respectively, for the nucleation and growth, and diffusion limited period. The influence of hydrogen concentration, steam concentration, sodium sulfate fraction, and sodium sulfide addition is also studied. A reaction mechanism is proposed for the hydrogen reduction in the solid state.
Particle suspension hydrodynamics in a tapered gas agitated reactor
Authors: Kleijntjens R. H. , van der Lans R. G. J. M. , Luyben K. Ch. A. M. 
Published: March 2009

AbstractExperiments were carried out in a tapered gas agitated solid‐liquid‐gas (S‐L‐G) reactor at 4 reactor volumes (up to 4 m3 ) with 4 different slurry densities (up to 40 mass%). Using monodisperse sand particles (260 μm diameter) at a low specific power input (ranging from 50‐300 W/m3), minimal suspension was achieved. The spatial solids hold‐up distributions were determined using a specially designed sampling probe. In combination with a mathematical model, the measurements show that a decrease in the ratio of the eddy length and the particle diameter (le/dP) takes place at increasing slurry densities. At a solids hold‐up of about 0.4, the critical lower limit (l < le/dp < 5). below which no suspension state can exist, is reached.
Neural network based objective flow regime identification in air‐water two phase flow
Authors: Cai Shiqian , Toral Haluk , Qiu Jianhung , Archer John S. 
Published: March 2009

AbstractThe Kohonen self‐organising neural network was applied to identify flow regimes in horizontal air‐water flow. The neural network was trained with stochastic features derived from turbulent absolute pressure signals obtained across a range of flow regimes. The feature map succeeded in classifying samples into distinctive flow regime classes consistent with the visual flow regime observation.
Amelioration du transfert convectif de chaleur par l'écoulement pulse dans un fluide visqueux
Authors: Shuai X. , Cheng S. , Antonini G. 
Published: March 2009

AbstractLes effets de perturbations pulsatoires sur le transfert convectif de chaleur dans un fluide visqueux coulé en régime laminaire ont été étudiés dans un éhangeur de chaleur à tubes cylindriques coaxiaux, la plage de température expérimentale étant de 30°C a 45°C. Le fluide étudié dont la viscosité est douze fois supérieure à celle de l'eau à la tempé5rature ambiante est une solution aqueuse de glycérol à 60% par poids, le nombre de Reynolds des écoulements permanents varie de 150 à 1000. La présence des pulsations augmente de façon significative le transfert thermique, et ce à puissance mécanique dissipée identique. Nous avons en effet obtenu des améliorations du coefficient de transfert de plus de 300% grâe h fortes perturbations pulsatoires. Ainsi, des pulsations imposées à l'écoulement permanent représentent un moyen simple et efficace pour améliorer les échanges thermiques dans des fluides visqueux habituellement pompés en régime laminaire. Une corrélation établie à partir de nos données expérimentales en écoulement pulsé permet d'évaluer le nombre de Nusselt avec une erreur moyenne de 10%.
Thermal plasma production of fumed silica: The effect of quench conditions on thickening and thixotropic ability
Authors: Addona T. , Munz R. J. 
Published: March 2009

AbstractThe effect of quench conditions on the thickening and thixotropic ability of fumed silica was studied. The powder was generated by rapidly quenching a vapour stream containing SiO(g) with steam. Silicon monoxide vapour was produced by decomposing quartz in a transferred arc reactor using an Ar/NH,3 thermal plasma. The parameters investigated included pre‐quench temperature (1100‐2100 K), and supersaturation ratio (1 ‐ 107, quench rate (17000 ‐75000 K/s), and quench stoichiometry (27 ‐ 84). which was defined as the molar ratio of steam to SiO. The thickening and thixotropic ability of the powders increased with increasing quench rate and decreasing pre‐quench supersaturation. This was due to an increase in specific surface area. Use of large H2 O/SiO ratios caused a high degree of surface hydroxylation.