bluuebunny/crossref_metadata_2025 huggingface dataset:
Récupération sélective du vanadium dans l'effluent d'un procédé de fabrication du blanc de titane
Authors: Lortie R. , Klvana D. , Paris J.
Published: March 2009

The selective recovery of vanadium from an effluent of a manufacturing process for titanium white (oxide) has been made. The process retained is based on the partial neutralization of the effluent by means of calcium carbonate and on the separation of metal hydroxides from calcium sulfate and the solution. The hydroxides are thereafter calcined in the presence of a sodium salt, so that sodium vanadate may then be extracted by washing with water. Vanadium is finally precipitated by the addition of ammonium chloride or pH adjustment.

The experimental results obtained in the laboratory study of the effluent neutralization, the calcination and leaching of the hydroxides and the vanadium precipitation are presented and discussed. The yields obtained in the various stages and their interdependance are also discussed.
Comportement des lits fluidisés en milieu viscoélastique
Authors: Briend P. , Chavarie C. , Tassart M. , Hlavacek B.
Published: March 2009

The 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

The 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

The 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

Gas‐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

An 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

The 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

The 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

Most 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

An 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

Convective 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

A 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

The 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

A 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

Henry'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

Isobaric 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

A 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

Intraparticle 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

Axial 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

It 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

The 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

The 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

Fischer‐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

A 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

The 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 products

Quantitative 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

Experimental 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

A 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

By 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

The 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.
A continuous process for recovery of sulfur from natural gas containing low concentrations of hydrogen sulfide
Authors: Ghosh Tushar K. , Tollefson Eric L.
Published: March 2009

A continuous catalytic process was developed to remove hydrogen sulfide from a natural gas stream using activated carbon as catalyst. The concentration range of hydrogen sulfide in the gas stream studied was 300–3000 ppmv (0.0126–0.126 moles/m3). Virtually 100 percent conversion of hydrogen sulfide was achieved by the combination of various parameters. The “field gas” employed in this study exhibited cracking of some heavier hydrocarbons and made the product sulfur slightly brown. These hydrocarbons should therefore be separated from the gas stream prior to the oxidation reaction. No carbon monoxide or carbon dioxide was produced during the oxidation of hydrogen sulfide.

It is concluded that the process described herein has the potential for the removal of hydrogen sulfide as sulfur from a sour natural gas stream on a continuous basis and could therefore eliminate an environmental problem which now exists.
Prediction of the volume correction factor in gas–liquid systems
Authors: Guha D.K. , De P.
Published: March 2009

An expression for the 'volume correction factor', which accounts for the fraction of the liquid volume remaining attached to the nozzle after drop detachment, has been arrived at after making a pertinent force balance. This expression has been compared with expressions of other investigators in the field. The final correlation, based on the derived equation and experimental data covering a wide range of clear liquids and nozzle diameters, gives a value of 0.35 for the volume correction factor. It may be utilised for theoretical estimation of the drop volume.
Performance analysis of the ring furnace used for baking industrial carbon electrodes
Authors: Bui R. T. , Charette A. , Bourgeois T. , Dernedde E.
Published: March 2009

A model is developed for the purpose of analyzing the performance of the ring furnace and the effect of various operational parameters on energy consumption, furnace behavior and product quality. The model combines an energy balance on the gaseous stream and a calculation of heat transfer inside the solids. The process is a semi‐continuous counterflow heat exchange, further complicated by other phenomena such as air infiltration into the flue, evolution of volatile matter, and heat losses. Several simulation runs are made which succeed in reproducing the various real‐life operating conditions, and predicting furnace behavior and efficiency for other conditions. The model proves to be a useful tool for the analysis of this important and costly equipment of the aluminium industry.
Transfert de matière liquide‐paroi et hydrodynamique de l'écoulement de couette‐taylor‐poiseuille biphasique
Authors: Legrand J. , Coeuret F.
Published: March 2009

Le travail étudie expérimentalement le transfert de matière liquide‐paroi en présence d'un écoulement biphasique (solide‐liquide ou liquide‐liquide) dans un espace annulaire cylindrique avec rotation du cylindre intérieur et débit axial (écoulement de Couette‐Taylor‐Poiseuille). L'existence d'une phase dispersée maintient le régime d'écoulement‐constitué par le mouvement axial de cellules tourbillonnaires toroïdalesNdashsur un domaine hydrodynamique beaucoup plus étendu que dans le cas d'un écoulement monophasique. Les coefficients de transfert de matière augmentent de manière très sensible avec la présence d'une phase disperséde; cette augmentation est měme importante (de 60 à 100 %) dans le cas d'une émulsion.
Sensitivities in representing the phase behaviour of gas‐bitumen systems
Authors: Fu C.‐T. , Puttagunta V. R. , Hsi C.
Published: March 2009

Two well‐known cubic equations of state (PR and MSRK) were used to test the sensitivity in predicting the vapour‐liquid equilibrium (VLE) properties of gas‐bitumen mixtures using a set of published critical parameters for bitumen. The predicted results were inconsistent and indicated the need to develop critical parameters that reflect compositional variations in bitumens. Sensitivity studies were also conducted using critical parameters developed by correlations based on compositional analyses of bitumens. It was shown that with these new parameters, both equations of state predict reliable VLE compositions and liquid phase densities. It was also found that there are minima in the critical temperature and critical pressure for the Athabasca bitumen, indicating that the new parameters are closer to the “true” values.
Gas hold‐up in highly viscous pseudoplastic non‐newtonian solutions in three phase sparged reactors
Authors: Dharwadkar S. V. , Sawant S. B. , Joshi J. B.
Published: March 2009

Gas hold‐up structure was studied in a three phase sparged reactor of 200 mm diameter. Air and aqueous solutions of carboxymethyl cellulose were used as gas and liquid phases. Spherical glass beads formed the solid phase. The superficial gas velocity, rheological properties, particle size and solid loading were varied over a wide range and their effects on gas hold‐up structure were studied. A correlation for the estimation of the gas hold‐up as a function of superficial gas velocity, apparent liquid viscosity, particle settling velocity and solid loading was established.
Design and optimization of the gel solar pond
Authors: Wilkins E. , Lee T. K.
Published: March 2009

The gel pond concept is a unique modification of the conventional salt gradient solar pond. It replaces the salinity gradient zone by a transparent polymer gel and thereby eliminates all problems of instability associated with the former. A framework for the preliminary design of a gel pond to serve different purposes has been presented here.

Heat extraction at constant pond storage zone temperatures of 40°–80°C at storage zone depths of 2–5 m has been considered and optimum pond dimensions have been predicted depending upon maximum and minimum heat load constraints. The computer simulations are carried out with the meteorological conditions for Albuquerque, New Mexico. For example, the simulations show that the gel pond can provide an average heat load of 107 W/m2, a typical domestic water heating requirement, at a constant pond temperature of 40°C with a storage zone depth of 4.0 m and gel thickness of 0.6 m. For the case of power generation, the pond can provide a minimum of 32 W/m2 at a constant pond temperature of 80°C with a storage zone depth of 4 m and gel thickness of 0.6 m. These factors combined with the easy operation and maintenance of the gel pond seem to make it a better alternative compared with the conventional salt gradient pond.
Solution of stiff convection‐diffusion differential equations using marquardt's method
Authors: Hayes R. E. , Tanguy P. A.
Published: March 2009

A modified Marquardt method is successfully used to solve a stiff non‐linear convection‐diffusion problem with chemical reaction. An efficient solution strategy is proposed and comparisons are made with classical iterative solution methods based on loading. The performance of the algorithm is illustrated with an implicit finite difference method.
Mathematical model for process design and simulation of dephlegmators (partial condensers) for binary mixtures
Authors: Cave Sergio Di , Mazzarotta Barbara , Sebastiani Enzo
Published: March 2009

A mathematical model of dephlegmation processes (i.e. of partial condensation with countercurrent flow of rising vapour and falling condensate) has been proposed and the results of the simulation have been compared with those of five series of experimental runs carried out with two different binary systems. The agreement between calculated and measured values of the variables (compositions, temperatures, heat transfer surface) has been found satisfactory. Moreover, the extent of the rectification obtained from the experimental runs is generally small and appears to be slightly sensitive to both the temperature and the flow rate of the coolant.
Measurement of large gas‐liquid interfacial areas by the light transmission method
Authors: Urua Ini J. , Del Cerro M. C. G.
Published: March 2009

Theoretical formulations previously put forward to account for the effect of multiple scattering in the measurement of gas‐liquid interfacial areas, at high AL values, are critically assessed. It is shown that inconsistencies arising from these can be satisfactorily resolved on the basis of the theory of Al Taweel et al. (1984) and experimental data available in the literature for the evaluation of the different parameters associated with the theory. An equation is proposed for the calculation of large gas‐liquid interfacial areas for AL ≤ 280 and excellent agreement between predicted and experimental values is demonstrated.
Viscosity of compressed cold lake bitumen
Authors: Mehrotra Anil K. , Svrcek William Y.
Published: March 2009

Viscosity data over a temperature range of 37‐115°C and a pressure range of 0‐10 MPa gauge are presented for a Cold Lake bitumen sample. These data show that the compression of Cold Lake bitumen results in a significant increase in its viscosity. Results are compared with those from a similar study on an Athabasca bitumen sample. Also presented are two correlations for the effects of pressure and temperature on the viscosity of Cold Lake bitumen.
Role of capillary and viscous forces in mobilization of residual oil
Authors: Patel K. , Greaves M.
Published: March 2009

Experimental results are reported for a series of microemulsion displacement tests carried out in a consolidated core of medium permeability (1.75 μm2). The interfacial tension and viscosity were varied from 0.02 to 32.0 mN/m and 2.0 to 26.0 mN · s/m2, respectively. The amount of oil unrecovered is correlated as a function of capillary number, Nc. Results are compared with those obtained by other workers who used porous media of low permeability and the relative importance of capillary and viscous forces at various stages of oil mobilization is discussed.
Enzymatic hydrolysis of a Populus deltoides Substrate from a Thermo‐mechanical Treatment of Medium Consistency Slurries
Authors: ČApek‐MÉNard E. , Preiss B. , Bouchard J. , Chornet E. , Jaulin L. , Overend R. P.
Published: March 2009

Ground Populus deltoides was pretreated using a thermo‐mechanical process in which shear forces are applied by rapid passage of concentrated slurries (10‐14%) through homogenizing valves. The process permits accurate control of operational parameters to induce varying degrees of ultrastructure modification in the substrate. The poplar was pretreated at two levels of severity in the absence of mineral acid and a process time of the order of 2 minutes. The high severity pretreated substrate was more susceptible than commercial α‐cellulose to enzymatic saccharification by T. reesei cellulase supplemented with cellobiase (glucose yields of 103 ± 6% and 76.2 ± 1.8% respectively in 48 hours).
The kinetic rate of combustion of electrode carbon in the temperature range of 1000‐1200 k
Authors: Halder P. K. , Basu P.
Published: March 2009

Kinetic rates of combustion of electrode carbon particles were measured in a temperature range of 1000‐1200 K. Spherical carbon particles of size 7‐9 mm are burnt in hot streams of nitrogen‐oxygen mixtures. The velocity and the temperature of the mixture were varied. To compensate for the mass transfer resistance to the flow of oxygen to the carbon surface a mass transfer experiment was carried out in the same apparatus.

By using mass transfer coefficients from the above experiment kinetic rates are analysed statistically to give the following Arrhenius type correlation of the kinetic rate:

where n is in the range of 0.3 to 0.5.
Effects of oil phase viscosity on interfacial tension behaviour of oil/alkaline systems as measured by the spinning drop tensiometer
Authors: Neale Graham H. , Khulbe Kailash C. , Hornof Vladimir
Published: March 2009

This note examines the effects of oil phase viscosity on the interfacial tension of reacting systems (acidic crude oils in contact with alkaline solutions) as measured by the Spinning Drop Tensiometer. Surfactants are produced by chemical reactions at the interface, thereby causing the shape of the oil droplet in the tensiometer to change continuously. The rates of droplet elongation/contraction are necessarily influenced by the oil phase viscosity, thereby affecting directly the measured interfacial tension. The principal conclusion of this work is that although oil phase viscosity exerts a significant effect on the dynamic interfacial tension after attainment of the minimum value, it makes for only a small absolute change in the magnitude of the minimum interfacial tension itself.
Periodic operation of transport reactors for catalytic reactions
Authors: Sivakumar S. , Chidambaram M. , Shankar H. S.
Published: March 2009

Based on plug flow of gas and catalyst particles and concentration dependent deactivation kinetics, the performance of transport reactors under a periodic (rectangular pulse) inlet concentration is analysed for improvement in conversion and extent of catalyst decay. The effects of reaction and deactivation orders, reaction and deactivation constant groups, and γ (cycle split) on the performance of the reactors are evaluated theoretically. For reaction orders greater than one, periodic operation improves conversion. Resonance behaviour is observed for certain combinations of parameters. For identical operating conditions vertical upflow, downflow and horizontal flow reactors are compared. Conversion in upflow reactors is higher than that in either horizontal flow or downflow reactors. However, catalyst decay is the least in downflow reactors.
Two classes of anionic surfactants and their significance in hot water processing of oil sands
Authors: Schramm Laurier L. , Smith Russell G.
Published: March 2009

In hot water flotation of bitumen from Athabasca oil sands, two types of primary oil recovery response to sodium hydroxide addition are identified. Natural carboxylate surfactants can promote bitumen separation and flotation under certain process conditions, while a second, more polar, class of natural anionic surfactants can promote separation and flotation under different process conditions. As a result, some oil sands exhibit two recovery peaks as a function of sodium hydroxide addition. The phenomena are explained in terms of different sodium hydroxide additions required to reach critical surfactant concentrations specific to each surfactant class. The concept provides a means for interpreting a wide range of processibility phenomena.
The statistical properties and utility of rational functions models
Authors: Ratkowsky D. A.
Published: March 2009

Rational functions, also called “inverse polynomials”, have been used as approximations to a wide range of mathematical functions and integrals in computer applications. A fairly general rational functions model with a single regressor variable and three to five parameters, capable of fitting a wide variety of ascending and descending curves, including sigmoidal curves and curves with maxima and minima, was considered here. Good fits to a wide range of data were obtained, and generally, the model exhibited “close‐to‐linear” estimation behavior. Such behavior guarantees convergence to the least squares estimates using the Gauss‐Newton algorithm in only a few iterations starting with a set of “reasonable” initial estimates.
Characteristics of jet fuels produced from hydrogenated shale oils
Authors: Mukherjee N. L.
Published: March 2009

Shale oils from the United States (Geokinetics, Occidental, Paraho and Tosco II) were hydrotreated, fractionated into jet fuel cuts (boiling range 121–300°C), then characterized to evaluate their suitability as jet fuels. Nitrogen content was considerably higher, though the amount of hydrogen was relatively lower, than in typical petroleum jet fuels. Sulfur content was significantly below the acceptable limit. Trace metal contents in shale oil jet fuels were below the maximum levels for those in petroleum jet fuels. Vanadium, copper, lead and alkali metals were not present. Physical properties, except freezing points, were comparable to those of standard jet fuels.
Traitement par une méthode d'éléments finis de modèles de colonnes de rectification discontinue à garnissage
Authors: Aly S. , Pibouleau L. , Domenech S.
Published: March 2009

Les auteurs présenters des modèles mathématiques traduisant différentes représentations du fonctionnement d'une colonne de rectification discontinue à garnissage. On traite dans une première partie le fonctionnement en régime stationnaire à reflux total en considérant un écoulement piston du flux liquide et de la vapeur auxquels on superpose le phénomène de dispersion axiale et radiale. Les équations sont résolues par une méthode d'éléments finis de type Galerkine ainsi que par une méthode de différences finies. L'exploitation du modèle de fonctionnement en régime stationnaire avec dispersion axiale et radiale a permis de constater que cette dernière peut ětre négligée dans la plupart des cas. Par contre, l'étude du fonctionnement dynamique a montré que l'introduction du phénomène de dispersion axiale était toujours nécessaire pour représenter la réalité physique de façon satisfaisante.
A stochastic interpretation of convective transport enhancement by external force fields
Authors: Fahidy Thomas Z.
Published: March 2009

The enhancing effect of external force fields on convection occurring at solid‐fluid interfaces is interpreted by means of a simple stochastic relationship derived from the Erlang formula in the theory of Markov processes.
Surface phenomena and hydrodynamic effects on the deposition of pseudomonas fluorescens
Authors: Pinheiro M. M. , Melo L. F. , Bott T. R. , Pinheiro J. D. , Leitão L.
Published: March 2009

Biofilm adhesion to metals (copper, aluminium and brass) was studied at two different velocities and pH values of 7 and 9. Both bacteria and metals showed negative surface charges at those values of pH, which tends to slow down adhesion. Film densities increased with the fluid velocity and were also affected by the pH and by the growth rate of the bacteria. Long duration tests based on heat transfer measurements were run at five different fluid velocities and at pH = 7, showing in general an asymptotic behaviour and a control of deposition by adhesion and growth phenomena.
The influence of fluid elasticity on wall effects for creeping sphere motion in cylindrical tubes
Authors: Chhabra R. P. , Uhlherr P. H. T.
Published: March 2009

Experimental results are presented of wall effect for the slow motion of spheres in elastic, constant‐viscosity liquids. The results are correlated in terms of diameter ratio for d/D < 0.3, and Weissenberg number We < 5. Weissenberg number is defined as We = 2θVm/d, with θ the Maxwellian relaxation time (θ = N1/2τγ).

The wall effect is found to be adequately described by Newtonian expressions for small Weissenberg number, We < 0.01. For larger values of the Weissenberg number, We > 0.2, virtually no wall effect is discernible; the small effect observed is correlated by the wall factor expression

The wall effect observed is ascribed to the influence of fluid elasticity alone, since all the fluids used were elastic to a greater or lesser extent, but showed no shear thinning.
Hydrodynamics and liquid phase axial mixing in orifice pipe reactor
Authors: Lali A. M. , Khare A. S. , Joshi J. B. , Eapen A. C. , Rao S. M. , Yelgaonkar V. N. , Ajmera R. L.
Published: March 2009

Two phase flow in a horizontal pipe, with orifice plates placed at regular intervals as obstructions, was studied for the effect of phase velocities on flow patterns, fractional phase hold‐ups, pressure drop and liquid phase axial dispersion. Radioactive technetium‐99m (as an aqueous solution of sodium pertechnatate) was used as tracer. A pulse injection technique with two point measurements was employed. Three different orifice diameters were used (8 mm, 16 mm, and 20 mm) in a pipe diameter of 32 mm. The orifice spacing was 500 mm in all cases. Superficial gas (air) velocity was varied over a range from 0.02 m/s to 1.0 m/s and superficial liquid (water) velocity from 0.03 m/s to 0.85 m/s.

Different flow patterns under different flow conditions were identified and a generalised flow map is presented. Variations in hold‐ups and pressure drop with flow patterns have been explained. Rational correlations have been developed for fractional phase hold‐ups and pressure drop. A preliminary comparison of two phase gas‐liquid flow in a horizontal pipe with orifice obstructions (to be called orifice pipe reactor), as a gas‐liquid contacting device, is made with a conventional bubble column reactor. Recommendations have been made for future work.
An accelerated successive substitution method for single stage flash calculations
Authors: Gupta Anup K. , Bishnoi P. R. , Kalogerakis N.
Published: March 2009

An acceleration technique, based on the Dominant Eigenvalue Method of Orbach and Crowe (1971), is proposed to accelerate a successive substitution method in which liquid and vapor compositions are used as the iteration variables. The performance of this scheme is compared with the accelerated successive substitution method of Mehra et al. (1983) and the General Dominant Eigenvalue Method (GDEM) of Crowe and Nishio (1975) as implemented by Michelsen (1982, 1987) which iterate upon the equilibrium ratios. The proposed acceleration scheme exhibits a less oscillatory behavior during convergence, and requires less storage than the accelerated methods using the K‐factors as the iteration variables. However, the number of thermodynamic evaluations is comparable with that of Mehra et al. (1983) and is more than that of Michelsen (1982, 1987).
Conjugate heat transfer in turbulent falling liquid films
Authors: Gorla R. S. R. , Maloney T.
Published: March 2009

Heat transfer characteristics for a falling turbulent liquid film flow over a fin are analyzed using the conjugate convection‐conduction theory. Numerical results are obtained from a simultaneous solution of the energy equations of the fluid and the fin. Results are presented for the fin temperature distribution, dimensionless heat transfer coefficients, local heat fluxes, and fin efficiencies.
A gas‐solid reaction model — Variable temperature, pressure and structural parameters
Authors: Hastaoglu M. A. , Hassam M. S.
Published: March 2009

Diffusion and reactions in a porous pellet are treated as transient, nonisothermal, nonisobaric processes. Continuity and energy balance equations are solved simultaneously for temperature and concentration profiles in the pellet. Conductive, convective as well as radiative heat transfer are included. The ‘dusty gas’ flux model is used to describe the transport of diffusing gases. Viscous, bulk and concentration gradient terms have been included. Structural changes with reaction are accounted by considering the effect of changing grain radius on porosity and pore diameter.

The model predictions match conversion trends for carbon gasification over a temperature range of 800 to 1100°C investigated experimentally.