bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comportement des lits fluidisés en milieu viscoélastique
Authors: Briend P. , Chavarie C. , Tassart M. , Hlavacek B. 
Published: March 2009

AbstractThe flow of various fluids of different rheological behaviour has been studied in both fixed and fluidized beds. These fluids were water and aqueous solutions of glycerin, Carbopol and Separan AP‐30. For small Deborah numbers, the flow of Carbopol and Separan AP‐30 solutions thorough fixed beds is well described by the Ergun relation using the generalized Reynolds number of Christopher and Middleman (1965). Deviations from this behaviour are observed in fluidized beds as preferential flow paths easily occur near the distributor. These deviations are small for Newtonian fluids but take more importance with non‐Newtonian solutions and are increased by viscoelasticity.
Three phase flow of gasndashcoal slurry mixtures in vertical tubes
Authors: Kim S. D. , Choi J. H. 
Published: March 2009

AbstractThe pressure drop and liquid and slurry phase holdups of a cocurrent flow of gasNdashoil and gasNdashcoalNdashoil slurry mixture in cylindrical columns (1.85 and 2.85 cm‐ID) were investigated. The effect of viscosity (43.1‐315 cp) was determined using solutions of two different mineral oils and of four different concentrations of coalNdashoil mixtures.The liquid and slurry holdups increased with liquid flowrate and liquid viscosity and decreased with gas flow rate. For solid concentrations in the range 0‐35 wt% with the size of coal employed (0.07‐0.16 mm) the slurry behaved like a homogeneous Newtonian fluid. The data for frictional pressure drop and phase holdups were correlated in terms of the ratio of fluid velocity, and the Reynolds and Weber numbers of the liquid and slurry phases.
Pressure drop and separation efficiency in a flooded hydrocyclone
Authors: Witbeck Wayne O. , Woods Donald R. 
Published: March 2009

AbstractThe pressure drop and separation efficiency were measured of a hydrocyclone operating under flooded underflow or no air‐core conditions. The solids were glass spheres with a geometric number average diameter of 13 μm and a geometric standard deviation of 1.69. Water was the fluid. Other fixed variables included the solids feed concentration of 2265 mg/L, the glass hydrocarbon configuration following the optimal Rietema recommendations and the temperature. The variables were feed flowrate 0.44 to 0.63 L.s1 and volume split of 2.4:1 to 6.1:1; a factorial design was used.The pressure drop, ΔPs, was 4 to 7 times larger than that expected for air core operation and was correlated in terms of the capacity ratio Q/(ΔPs)0.47. The pressure drop was relatively independent of volume split.The separation efficiency was a much stronger function of volume split than of feed flowrate. The Dp(50) diameter at a feed flowrate of 0.63 L.s−1 lies between 4.3 to 9.2 μm; of the seven correlations available for predicting Dp(50), the approach of Rietema (1961) gives the best results. The experimentally measured reduced efficiency was less sharp than that reported by Yoshioka and Hotta (1955) and by the theory of Uematu et al. (1962).
Absorption of nitrogen dioxide and sulfur dioxide in methanol
Authors: Mohamed Rahoma S. , Klinzing George E. 
Published: March 2009

AbstractGas‐liquid chromatography was employed to determine the activity coefficients of NO2 and SO2 at infinite dilution in methanol. The infinite dilution activity coefficients at 301.2 K were found to be 15.5 ± 0.1 and 0.491 ± 0.055 for the systems NO2‐methanol and SO2‐methanol, respectively. These values were subsequently used along with the single parameter Wilson equation to predict vapor‐liquid equilibrium data for the systems NO2‐N2‐methanol and SO2‐N2‐methanol.
Thermal diffusivities of some porous oxides
Authors: Lin F. , Ford J. D. 
Published: March 2009

AbstractAn unsteady‐state method for determination of the thermal diffusivity of a porous sphere, based on direct contact condensation of steam, was developed. A modified formula relating thermal diffusivity to porosity was proposed from theoretical considerations. Experimental measurements on known solids showed good agreement with literature values. Unknown thermal diffusivities of some metallic oxides (in powder form) were determined at 60°C, with the following results:Cr2O3: α = 1.23 (10 6) m2/s: CuO: α = 2.63 (10 6) m2/s: Fe2O3: α = 1.02 (10 6) m2/s; V2O5: α = 1.14 (10 6) m2/s.
Measurements of velocity and concentration for a two‐phase turbulent jet
Authors: Subramanian Viswanath , Raman Narayanan 
Published: March 2009

AbstractThe velocity and concentration distributions for an axisymmetric air jet containing sand particles are determined in the fully developed region. Similarity of the profiles is seen beyond 40 nozzle radii downstream from the jet exit and entrainment is gradually suppressed with increase in the initial particle concentration.
Rapid build‐up of a pyrophoric polymer in ethylene plant deethanizer and depropanizer columns
Authors: Georgieff K. K. 
Published: March 2009

AbstractThe rapid build‐up of pyrophoric polymer in the deethanizer and depropanizer distillation columns in ethylene manufacture has resulted in many unscheduled shut‐downs. Polymer formed in the columns of an Eastern Canadian petrochemical plant was found to consist of a reactive copolymer of butadiene. It absorbed oxygen more rapidly and at lower temperatures than commercial polybutadiene. Some of the peroxidic oxygenated products, which were formed, decomposed exothermally in air at temperatures from ambient to 145°C. The mechanism of polymer formation, the products of oxidation, reagents for deactivating the polymer, and suggestions for reducing the rate of polymer formation and cleaning the columns are described.
Calculation of effectiveness factor for multiple claus reactions with single‐step rate‐controlling
Authors: Razzaghi Minoo , Lana Ivo G. Dalla 
Published: March 2009

AbstractMost of the bountiful literature on the calculation of effectiveness factors for catalyst particles deals with relatively simple reactions and kinetics. The performance of catalyst particles in the industrially important, modified Claus reaction introduces multiple reactions, sulphur vapour equilibria, non‐linear kinetics and limiting thermodynamic conversions into the calculation of local effectiveness factors. This analysis demonstrates a means for generating local effectiveness factors, during reactor design calculations by the use of a single calculated curve of versus a modified Thiele parameter for spherical particles.
An empirical correlation for viscosity of molten salt hydrates
Authors: Sharma S. K. , Jotshi C. K. , Singh Amrao 
Published: March 2009

AbstractAn empirical correlation between reduced viscosity and reduced temperature for molten salt hydrates showing Arrhenius behavior above their melting points has been reported. This correlation predicts the viscosity of molten salt hydrates at temperatures not more than 15 to 30°C above the melting points, within an accuracy of ±5%. Consistency tests for viscosity data using reduced parameters have been reported.
Natural convection in a heat generating fluid bounded by two horizontal concentric cylinders
Authors: Shekar B. Chandra , Vasseur P. , Robillard L. , Nguyen T. Hung 
Published: March 2009

AbstractConvective flow and heat transfer of a Boussinesq fluid contained between two horizontal concentric cylinders is investigated under the effects of two driving mechanisms – an externally‐imposed temperature gradient across the annulus, and a uniform internal heat generation. Numerical results for flow field and temperature distribution are obtained in terms of four dimensionless parameters, namely the radius ratio, R, the Prandtl number, Pr, the Rayleigh number, Ra*, and the ratio, S, between the characteristic temperature induced by internal heating and the applied temperature difference between the boundaries. Depending on the value of S, the flow pattern is made up of either one or two vortices in each half cavity, and heat is transferred into or out of the cavity through the hot wall. In particular, for a certain value of the applied temperature difference, the hot wall apparently acts as a thermally‐insulated boundary, the internal heat is completely lost through the cold wall, and the fluid undergoes a transition from a bicellular to a unicellular flow regime.
Ethylene oxide reactor: Safety according to operability analysis
Authors: Piccinini Norberto , Levy Guido 
Published: March 2009

AbstractA detailed account is given of operability analysis of the cooling system of an ethylene oxide reactor (30,000 t/yr) as a typical example of a particularly critical process.Although this method is purely qualitative, it proved very effective in revealing the more critical parts of the plant at the design stage, with the result that suitable modifications were introduced.This assertion is supported by the results of a fault tree analysis, which is also described with reference to a detailed example of a reactor feed and control circuit. It was found that operability analysis is of more general and ready applicability than fault tree analysis, since it does not require failure rate data.
Application of the fourier transform to the measurement of KLaL in non‐mechanically agitated contactors
Authors: André G. , Moo‐Young M. , Robinson C. W. 
Published: March 2009

AbstractThe authors recently proposed (André et al., 1981) a new method of measuring the overall volumetric mass transfer coefficient (KLaL) in gas‐liquid‐solid contactors of the bubble‐column type. The present paper deals with improved implementation of this method. The previous work showed that prior knowledge of the extent of backmixing in the gas phase was required in order to obtain reliable estimates of KLaL. It is shown here that parameter fitting in the frequency domain, using the Fourier transform of the response curves, may be used to estimate both KLaL and the extent of backmixing in the gas phase simultaneously. The main features of this particular approach are described in detail and are discussed in the light of experimental data obtained in two bench‐scale contactors (a bubble column and the novel inverted conical bottom contactor). In addition, the effect of contactor geometry and paper pulp addition on KLaL also is presented. It is shown that both the conventional bubble column and the novel contactor yield comparable gas‐liquid mass transfer rates.
A model for liquid‐liquid extraction column performance — The influence of drop size distribution on extraction efficiency
Authors: Zhang S. H. , Yu S. C. , Zhou Y. C. , Su Y. F. 
Published: March 2009

AbstractA precise model for predicting liquid‐liquid extraction column efficiency based upon assumed hydrodynamic, axial mixing and mass transfer behaviour has been formulated and solved numerically.The complex nature of the dispersed phase can be better described by drop‐size‐dependent residence time distribution (RTD). Both the variation of axial velocities due to drops of different sizes, i.e. forward mixing, and the axial dispersion for the drops of the same size have been considered in this model.The computed results reveal that the effects of both varying velocities and dispersion of drops on extraction efficiency are appreciable and cannot be neglected, and the efficiency may be overestimated if only a forward mixing model is adopted. The comparison of the experimental values of NODP with those predicted shows that the mass transfer data obtained in RDC agree well with the values predicted by the present model for the case of solute transfer in c→d direction, and are slightly higher than the predicted ones for the transfer in d→c direction.
Vapour liquid equilibrium calculations for dilute aqueous solutions of CO2, H2S, NH3 and NaOH to 300°C
Authors: Roberts Bruce E. , Tremaine Peter R. 
Published: March 2009

AbstractHenry's law constants for aqueous CO2, H2S and NH3 up to 300°C have been recalculated from literature vapour pressure, enthalpy and heat capacity data. The high vapour pressure of water above 150°C causes significant solute‐water interactions in the gas phase, which were calculated using the Peng‐Robinson cubic equation of state. The results were combined with selected ionization constant data to derive a vapour‐liquid equilibrium model for dilute solutions. The model reproduces experimental data for binary systems at solute molalities of up to 0.5 m at 100°C, 1.0 m above 250°C and ionic strengths below about 0.1 m.
Vapor‐liquid equilibria of the acetylacetone‐1,3‐dioxolane system
Authors: Comelli Fabio , Francesconi Romolo 
Published: March 2009

AbstractIsobaric vapor‐liquid equilibrium data on the mixture acetylacetone‐1,3‐dioxolane were obtained at P = 40, 66.67 and 98.67 kPa. Both keto and enol tautomers of acetylacetone were taken into account when checking the thermodynamic consistency of the data with the area test. The integral\documentclass{article}\pagestyle{empty}\begin{document}$ I = \int_{x_B = 1}^{x_B = 1} {\ln \left({\gamma _A /\gamma _B} \right)dx_B} $\end{document} is not zero and is higher than the estimated error of I, ΔI.Specific interactions among the tautomers and 1,3‐dioxolane are hypothesized to explain the non random deviations of I from the expected zero value.
Intraparticle mass transfer in bidispersed porous ion exchanger part I: Isotopic ion exchange
Authors: Yoshida Hiroyuki , Kataoka Takeshi , Ikeda Shigeru 
Published: March 2009

AbstractA simple theoretical equation of intraparticle effective diffusivity 𝒟e, in a bidispersed porous ion exchanger was derived under the assumption of parallel diffusion in the solid phase and the macropore. 𝒟e of Na+, CO2+, Zn2+ and Ce3+ in several MR‐type resins and other type of porous resins (P‐type resin) were measured by isotopic ion exchange. In MR‐type resin, 𝒟g was affected by the concentration of the bulk solution Co and was separated into a solid phase diffusivity 𝒟g and a macropore diffusivity 𝒟p by using the derived equation. Equations for estimating 𝒟g were obtained. The diffusivity ratio of 𝒟p to diffusivity in infinitely dilute aqueous solution for a monovalent ion agreed with the Neale and Neder's theoretical equation for tortuosity factor within 10%. In P‐type resin, it became clear that the effect of macropore diffusion is negligible. 𝒟e was little affected by Co. Separated 𝒟p was little larger than 𝒟g, and 𝒟g was nearly equal to 𝒟e. The equations for estimating 𝒟g of a P‐type resin were quite similar to those for gel‐type resins.
Intraparticle mass transfer in bidispersed porous ion exchanger part II: Mutual ion exchange
Authors: Yoshida Hiroyuki , Kataoka Takeshi 
Published: March 2009

AbstractIntraparticle mass transfer of mutual ion exchange in MR‐type resin was analyzed based on the assumption of parallel diffusion of counter ions in the solid phase and the macropore. Local equilibrium was also assumed between the concentration of counter ions in the solid phase and in the macropore, and the mass action law was applied. The Nernst‐Planck equation was applied to the fluxes of ions diffusing through the solid phase and the macropore. The derived equations were solved numerically by using macropore and solid phase diffusivities obtained earlier by isotopic ion exchange. The theoretical lines agreed fairly well with the experimental uptake curves of R‐H‐NaCl, R‐Na‐HCl, R‐Na‐Zn(NO3)2, R‐Zn‐NaNO3 and R‐H‐ZnCl2 systems. The lower the concentration of bulk solution Co is, the smaller the effect of Co on the ion exchange rate becomes. The experimental uptake curves of Co ≤ 0.01 (mmole/cm3) were not affected by Co but agreed fairly well with the theoretical line for solid phase diffusion control. An approximate estimation method for obtaining the uptake curve was also proposed. This method gave fairly good approximation for equal valence ion exchange and for R‐Na‐Zn(NO3)2 systems.
Liquid‐phase axial mixing study in a mobile bed contactor with low density particles
Authors: Rama O. P. , Rao D. P. , Rao V. Subba 
Published: March 2009

AbstractAxial mixing of the liquid phase in a 0.15 m ID mobile bed contactor has been studied for spherical, cork and irregular‐shaped particles of densities 53, 183 and 112 kg m−3, respectively, using the air‐water system. The range of gas and liquid flow rates covered were from 0.5 to 5 m s−1 and from 0.011 to 0.044 m s−1, respectively. The experimental breakthrough curves were interpreted by means of the axial dispersion model. Correlations for the Peclet number and axial dispersion coefficient have been proposed. The results indicate that near plug flow of the liquid phase could be achieved with higher static bed heights if the congregation of particles at the wall could be avoided.
The controlling quantity in cubic equations of state for phase equilibrium calculations
Authors: Adachi Yoshinori , Lu Benjamin C.‐Y. 
Published: March 2009

AbstractIt has been demonstrated that the vapor—liquid equilibrium values calculated from the modified Martin equation and the Clausius equation are identical to those obtained from a properly modified van der Waals equation of state.The reason for this observation is explained in this work in terms of the role of Ωa (= aPc/r2T) at specified state conditions. It is the controlling quantity in VLE calculations when simple van der Waals‐type equations of state together with the conventional mixing rules are used. Thus, equations capable of yielding identical values of Ωa give identical equilibrium values. The evidence and the mathematical proof of the relationship required for defining such a role for Ωa are presented.
The solubility of H2S and CO2 in a diethanolamine solution at low partial pressures
Authors: Lal D. , Otto F. D. , Mather A. E. 
Published: March 2009

AbstractThe solubility of H2S, CO2 and their mixtures in a 2.0 kmol m−3 aqueous solution of diethanolamine has been determined at 40°C and 100°C at partial pressures of the acid gases between 0.003 and 6.5 kPa. The results have been compared with values calculated by a method of prediction.
Prediction of the maximum spoutable height in spout‐fluid beds
Authors: Rao K. Babu , Husain Asghar , Rao Ch. Durgaprasada 
Published: March 2009

AbstractThe development of the semi‐theoretical correlation in Hadzisdmajlovic et al. (1983) for predicting the maximum spoutable height in a spout‐fluid bed, is observed to involve certain discrepancies. Based on their experimental data, a new correlation is proposed.
Fischer‐tropsch synthesis in bubble column slurry reactors on FE/K‐catalyst
Authors: Sanders E. , Ledakowicz S. , Deckwer W.‐D. 
Published: March 2009

AbstractFischer‐Tropsch synthesis (FTS) on K promoted Fe catalyst was studied in three bubble column slurry reactors (BCSR) of 2.5, 5, and 10 cm diameter. The objective was to check data reproducibility under conditions of arbitrary alterations of various parameters. First order rate constants evaluated on the basis of appropriate slurry reactor models were chosen as an approximate measure to characterize data reproducibility and catalyst activity. It was found that rate constants and hence reproducibility may differ by a factor of two if different batches and precipitations of catalyst are considered. Within the parameter ranges covered in this study this rule of thumb is valid irrespective of reactor diameter, type of sparger, catalyst concentration, temperature, pressure, and gas flow rate. The rate constants compare well with literature data.
Measurement of high‐temperature effective thermal conductivity of porous spheres
Authors: Barua S. K. , Wynnyckyj J. R. 
Published: March 2009

AbstractA new unsteady‐state method for measuring the high temperature effective thermal conductivity of porous spheres is described. The method is based on moving a spherical body from an enclosure at a low temperature into one at a higher temperature and measuring the surface temperature with a recording radiation pyrometer. The thermal conductivity is evaluated using the known relations between the dimensionless surface temperature and time. The apparatus requirements are discussed in detail.The thermal conductivities of calcined dolomite/silicon metal mixtures, of the type used in the production of magnesium, were measured at 750 to 1150°C with compaction pressures of 67 to 185 MPa both before and after reaction.
Dilute acid depolymerization of cellulose in aqueous phase: Experimental evidence of the significant presence of soluble oligomeric intermediates
Authors: Abatzoglov N. , Bouchard J. , Chornet E. , Overend R. P. 
Published: March 2009

AbstractThe objective of this investigation is to show that rapid hydrolysis can be achieved by passage of aqueous cellulosic suspensions (2–10% solids) through capillaries followed by sudden decompression and post‐treatment under dilutes acid conditions.Through detailed experimentation within the 200–240°C temperature range and at low sulfuric acid concentrations (0.2–1.0% w/w) it was found that liquefaction of the cellulose proceeds via extensive formation of soluble oligomeric intermediates.A simple kinetic model has been developed to explain the liquefaction‐saccharification patterns of the cellulose. The sequence considered is:Cellulose → Oligo‐derivatives → Glucose → Decomposition productsQuantitative values of the rate constants have been determined and a discussion on the selectivity of the overall reaction sequence is presented.
Vapor—liquid equilibria of acetonitrile‐1‐propanol mixtures
Authors: Prasad A. Ravi , Rao K. Venkateswara 
Published: March 2009

AbstractExperimental P‐T‐x data have been measured for acetonitrile‐1‐propanol mixtures. The Margules, UNIQUAC, UNIFAC and ASOG models and the method of Mixon et al. have been used to predict the vapor compositions from the P‐T‐x data. A good agreement has been found between the vapor compositions predicted by the above except in the case of UNIFAC. The parameters obtained by using the single set data treatment gave satisfactory representation of vapor liquid equilibria of acetonitrile‐1‐propanol mixtures.
PRSV2: A cubic equation of state for accurate vapor—liquid equilibria calculations
Authors: Stryjek R. , Vera J. H. 
Published: March 2009

AbstractA new temperature dependence for the attractive term of a modified Peng‐Robinson cubic equation of state is proposed. The three adjustable parameters required per pure compound are reported for over ninety compounds of industrial interest. General expressions for the use of different mixing rules for different pairs of compounds in a multicomponent mixture are presented. The mixing rule proposed by Huron and Vidal is reinterpreted to make it applicable in the genera) treatment.
The gas disengagement technique for studying gas holdup structure in bubble columns
Authors: Schumpe A. , Grund G. 
Published: March 2009

AbstractBy recording the drop in dispersion height after stopping the gas supply, the fractions of large and small bubbles, the respective swarm rise velocities, and the contributions to the overall gas flow can be determined. Some problems of the analysis are discussed in detail. The efficiency of the technique is demonstrated for the results obtained with two different gas distributors in a bubble column of 30 cm diameter.
Concentration‐dependent diffusivity of benzoic acid in water and its influence on the liquid–solid mass transfer
Authors: Irandoust Said , Andersson Bengt 
Published: March 2009

AbstractThe diffusion coefficient of benzoic acid in water at 25°C has been measured as a function of concentration using the Taylor dispersion technique. The diffusion coefficient was found to decrease from 1.25 × 10−9 m2/s to 1.07 × 10−9 m2/s when the concentration increased from 0.27 mol/m3 to 5.44 mol/m3. Two different models describing the concentration dependence of the diffusion coefficient have been developed. They are fitted to the measured data and experimental data from literature at infinite dilution (D = 1.57 × 10−9 m2/s) and at higher concentrations up to 20 mol/m1 (D = 0.75 × 10−9 m2/s). The significance of the concentration dependence is evaluated by measurement and by computer simulations of liquid–solid mass transfer in a tube. The simulations show that 0.80 × 10−9 m2/s is the constant diffusivity that gives the best approximation in dissolution studies.