bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment of complex silver arsenide concentrate in nitric acid system
Authors: Kunda Wasyl
Published: March 2009

A complex silver arsenide‐sulphide concentrate containing bismuth, cobalt, nickel, copper, zinc, lead and iron as major constituents, was leached in nitric acid. The leach solution, which contained 95% to 99% of the Ag, Bi, Co, Ni, Cu, As and Fe present in the ore, was further processed to separate the metals into the following fractions: (1) silver chloride, (2) bismuth oxychloride and/or hydroxide, (3) arsenic‐iron precipitate and (4) Ni‐Co‐Cu‐Zn sulphide.

Silver was precipitated from solution with sodium chloride. Bismuth oxychloride‐hydroxide and arsenic‐iron were precipitated by controlled ammonia addition and cobalt‐nickel‐copper‐zinc sulphides were precipitated with ammonium sulphide.

Silver chloride was further processed to a high purity silver powder by heat treatment with sodium carbonate.

The parameters controlling each processing step are discussed.
Measurement of binary diffusion coefficient of gases and organic vapours by chromatography
Authors: Pathak B. K. , Singh V. N. , Singh P. C.
Published: March 2009

The binary diffusion of organic vapours such as benzene, nitrobenzene, aniline, n‐hexane, acetone, ethyl alcohol and toluene in H2, Ar and N2 at different temperatures and the diffusion coefficients of the gas pairs; Ar‐O2, Ar‐N2, Ar‐SO2, N2‐NH3, N2‐O2, N2‐CO2 & N2‐SO2 at 25°C have been studied using a gas chromatograph (GCHF‐18). Good agreement was found between observed and theoretically calculated values of diffusion coefficients.
Surface shear viscosity of straight chain (c15 to c20) fatty acids
Authors: Moo‐Young M. , Fulford G. D. , Deysarkar Asoke K.
Published: March 2009

Experiments were carried out to measure surface shear viscosities of a series of straight chain fatty acids from C15 to C20. The experimental results indicated that members of the series with even‐numbered C‐atoms were essentially surface‐Newtonian in behaviour with viscosity increasing with increasing chain length. However, members of the series with odd‐numbered C‐atoms were surface pseudoplastic and the degree of pseudo‐plasticity decreased with increase in chain length. The experimental results also indicated that aging of surface‐active solutions increases their surface shear viscosities.
Implementation and demonstration of a quasi‐steady‐state controller for yeast fermentation
Authors: Kalogerakis N. , Boyle T. J.
Published: March 2009

Earlier work has presented the need for, and the structure of, a control system to force fed batch fermentations to a quasi‐steady‐state (QSS) rapidly. Necessary modifications to this controller to permit it to be implemented on a computer‐coupled laboratory fermentor are presented. These include use of manual sampling to obtain reliable cell concentration data and the use of stream blending to achieve the desired control actions. The implementation is via a DDC loop structure which achieves proportional feedback control, calibrated decoupling of response models, and non‐linear time‐varying actuator constraints. The experimental run presented shows the desired rapid response of cell concentration with evidence of no interaction between cell and substrate, even though the manipulated variables are saturated throughout much of the transient.
A flexible solution method for generalized equilibrium stage columns
Authors: Li M. C. , Frost R. J.
Published: March 2009

This paper presents a flexible solution method for the process design and simulation of generalized equilibrium stage absorption or distillation columns for solving a wide range of multistage, multicomponent separation problems in the petroleum or petrochemical industries. Although the model was developed to increase the control flexibility of product components in a solution, it was found that it also increases the efficiency of convergence at the expense of greater core usage. The mathematical model includes overall material balances, component material balances, energy balances, summation equations and specification equations. These nonlinear equations are solved simultaneously via the matrix partitioning technique together with the popular Newton‐Raphson iterative algorithm. The method is applicable for both absorption and distillation columns with multiple feeds and sidedraws. This model will offer more flexible choices of the column specifications such as tray temperature, overhead product rate, reflux ratio, boilup ratio, tray vapor/liquid flow and product purity/recovery. The composition dependent equilibrium and enthalpy correlations such as Chao‐Seader, Grayson‐Streed, and Soave‐Redlich‐Kwong are incorporated into the mathematical model. Most problems can be easily converged with less than ten iterations.
Electromagnetic sensing of slurry concentration
Authors: Peters J. , Shook C. A.
Published: March 2009

Fluctuations in the output voltage from a conventional magnetic flux flowmeter have been shown to depend upon mean velocity and slurry concentration. Since reliable values of mean velocity can be obtained from time‐average voltages, the fluctuations could be used to sense slurry concentration

The relationship between the fluctuations and slurry concentration depends on particle and fluid properties so that calibration would be required. However with further progress in understanding of vertical slurry flows, the relationship may be predictable.
Effect of geometrical arrangement and interdrop forces on coalescence time
Authors: Vohra D. K. , Hartland S.
Published: March 2009

According to the Reynolds' equation the time taken for a thin film to reach a critical thickness at which rupture occurs is a function of the film area and applied force. It follows that the coalescence time of a liquid drop is greatly affected by its geometrical configuration. If the drop is unconstrained the coalescence time increases when a vertical force is applied to the drop, but if the drop is constrained by the presence of surrounding drops its coalescence time decreases as the applied force increases. This explains why the rate of coalescence at the disengaging interface of a close‐packed dispersion increases with the dispersion height. The coalescence time for a planar film is usually less than for the spherical film formed between a drop and its homophase which explains why near‐horizontal surfaces inserted into close‐packed dispersion increase the rate of coalescence. The coalescence time of a drop in a close‐packed dispersion decreases as it approaches the disengaging interface. This means that the volume rate of coalescence at the interface may equal the disperse phase throughout without the necessity for interdrop coalescence. When the applied pressure is much greater than the van der Waals pressure, as in a close‐packed dispersion, the critical film thickness is itself a function of the film area and applied force, but this has little effect on the above conclusions. When the applied pressure is much less than the van der Waals pressure, as in a loose‐packed dispersion, the critical film thickness is only a function of the film area and the affect of the applied force on the coalescence time is then increased.
Computer generated time & distance values of nutrient constituents with applications to timed‐release capsules
Authors: Forgacs C. , O'Brien R. N.
Published: March 2009

The diffusion equation for infinite cylindrical sources has been solved for the boundary conditions appropriate to timed‐release fertilizer pellets. The solution was tested against experimental results of the distortion of the image of a grind illuminated by laser light and recorded on video tape. The optical theory was examined for validity using Fermat's Principle. A computer program was developed to predict concentration as a function of time and distance with sufficient flexibility to allow for multiple sources and any other variation which can be accounted for by change of diffusion coefficient.
The kinetics of dissolved oxygen reaction in aqueous sodium dithionite solutions
Authors: Kawagoe Mikio , Robinson Campbell W.
Published: March 2009

The kinetics of the reaction between dissolved oxygen and sodium dithionite in alkaline aqueous solution was investigated in a stirred cell. For dithionite concentrations below 0.08 kmol/m3 and sodium hydroxide concentrations from 0.044 to 0.27 kmol/m3, the results show the reaction to be first order in dithionite and zero order in oxygen. The Arrhenius activation energy was determined to be 76.2 MJ/kmol in the temperature range 15 to 34°C. Addition of other electrolytes (sodium sulphate or potassium chloride) had no effect on the kinetics.
Thermodynamic availability analysis of fractional distillation with vapour compression
Authors: Mostafa Hamdi A.
Published: March 2009

Thermodynamic analysis based on the concept of availability or energy arising from the second law of thermodynamics is a useful tool for process development and design. The exergy is especially useful for analysing processes containing different forms and qualities of energy. In these cases the analysis based on the first law could not give meaningful results.

The work attempts to show in what circumstances the compression of the overhead vapour from a distillation column and the use of condensing vapours to reboil the bottoms is preferred to the conventional scheme. To achieve this goal, the thermodynamic energy coefficient of performance of the system is calculated as a function of system properties, column pressure, degree of separation, compression ratio and number of plates. The results of calculations indicate the effect of each variable on the thermodynamic performance of distillation with vapour compression and point out directions for process improvement.
Methanation of carbon monoxide catalyzed by nickel/zeolite y and nickel/ η‐alumina; effect of reduction time
Authors: Bhatia S. , Bakhshi N. N. , Mathews J. F.
Published: March 2009

The catalytic behavior of three nickel catalysts, viz. nickel supported on η‐alumina and nickel supported on zeolite Y (prepared by impregnation and ion exchange methods) were investigated for the methanation reaction. All the catalysts were reduced in flowing hydrogen at 723 K for times varying from 6 h to 24 h. The catalytic activities of these catalysts were determined using a differential flow reactor. The catalysts were characterized using the techniques of hydrogen chemisorption and x‐ray diffraction.

Nickel metal areas were found to increase with reduction time for all catalysts. X‐ray diffraction studies showed that crystallite size varied with reduction time in the case of Ni/zeolite Y catalyst (both impregnated and ion exchanged). Turnover numbers were found to vary with crystallite size and the maximum values of the turnover number were obtained for the catalysts having crystallite sizes of 14‐16 nm. There appears to be strong evidence that reduction time can have an effect on catalytic activity; possibly by its effect on crystallite size.

The effect of support on catalytic activity was more complicated as there appeared to be an interaction with reduction time. However, nickel/η‐alumina appeared to be a more active catalyst than nickel/zeolite Y.
Annular bed reactor‐methanation of carbon dioxide
Authors: Davis Mark , Fairweather Graeme , Yamanis John
Published: March 2009

Catalytic methanation of carbon dioxide has been studied in a new type of annular bed reactor. In this new design, the central core is packed with large inert spheres; the catalyst occupies the annular space between the inert spheres and the wall. A first‐generation model, representing insothermal operation of the annular bed, prepicts improved conversion for the packed compared to the unpacked‐core reactor.
Kinetics and mechanism of deactivation by fouling of a silica‐alumina catalyst in the gaseous phase dehydration of isoamyl alcohol
Authors: Corella Jose , Asua Jose M.
Published: March 2009

The kinetics and mechanism of the deactivation by fouling of a silica‐alumina catalyst in the dehydration of isoamyl alcohol in gas phase have been investigated. It has been found that deactivation takes place in series with the main reaction by coverage of active sites. The kinetic equation of deactivation is of the Langmuir‐Hinshelwood type, and the parameters have been determined from the data obtained in an isothermal reactor.
Thermal decomposition of pyrite in a fluidized bed
Authors: Monteiro J.L.F.
Published: March 2009

The thermal decomposition of pyrite was investigated in a silica batch fluidized bed reactor, in the temperature range 594 to 625°C. Particles were sampled during each run and those partially reacted showed a sharp reaction front. An equilibrium between pyrite and the resulting pyrrhotite is maintained until the central core of pyrite has disappeared, after which the reaction proceeds uniformly throughout the particle forming pyrrhotites with successsively lower sulfur contents. The reaction rate was sensitive to temperature, particle size and gas velocity. Application of the shrinking core model is consistent with heat transfer as the controlling step.
Wet oxidation of glucose
Authors: Skaates J. M. , Briggs B. A. , Lamparter R. A. , Baillod C. R.
Published: March 2009

Wet oxidation is used to oxidize organic substances at a controlled rate in an aqueous medium at elevated temperatures and pressures. Aqueous glucose solutions were oxidized with pure oxygen at four different temperatures in the range 176.7°C to 260.0°C, and at an oxygen pressure of 2.3 MPa. Three distinct stages of wet oxidation were found — induction, rapid oxidation, and slow oxidation. During the rapid oxidation period the reaction was assumed to be confined to a thin liquid layer next to the gas‐liquid interface. The activation energy for the rapid oxidation period was estimated to be 130 ± 20 kJ/mol. Acetic acid was found to accelerate the rate of wet oxidation of glucose only slightly.
Experimental determination of air‐h2s equilibria under claus furnace conditions
Authors: Bennett Howard A. , Meisen Axel
Published: March 2009

Since little fundamental information is available on the Claus furnace, equilibrium compositions of air‐H2S mixtures were calculated for temperatures and O2/H2S ratios ranging from 600 to 2000°K and 0 to 1, respectively. Sulphur yields were found to increase marginally when O2/H2S ratios less than 0.5 (stoichiometric) are used. Feed impurities such as H2O, CO2 and NH3 generally diminish the sulphur yields.

To determine equilibrium compositions experimentally, known air‐H2S mixtures were reacted in the range of 800 to 1500°K and the products were analyzed chromatographically. The measurements for H2S dissociation agreed well with theory and Raymont's experimental data; the results for H2S oxidation showed the same trends as theoretical predictions, but did not agree quantitatively. Reasons for the discrepancies and their practical implications are discussed.
Synergistic surfactant mixtures containing lignosulphonates
Authors: Hornof Vladimir , Neale Graham , Bourgeois Paul
Published: March 2009

Enhanced oil recovery (EOR) schemes have been gaining importance over the past several years. Of the various methods being tested, surfactant (or micellar) flooding appears to be one of the most promising ones. It involves injecting into the well the solution of a surfactant which reduces the inter‐facial tension between the displacing aqueous solution and the oil trapped in the reservoir. Depending on the concentration of the surfactant, oil displacement proceeds either by a miscible process (surfactant concentration > 10%) or by a immiscible process (surfactant concentration = 2–3%). Miscible flooding converts to the immiscible process as the system is diluted by connate (interstitial) water. Under immiscible conditions, the most significant parameter affecting recovery is the interfacial tension(1,2). Petroleum sulfonates are perhaps the most important group of surfactants capable of producing very low interfacial tensions between crude oil and the water phase. Their relatively high cost, however, renders many potential applications uneconomical.
Three‐phase fluidization: Some knowledge gaps
Authors: Epstein Norman
Published: March 2009

The most recent review by østergaard — on the fluid mechanics of three‐phase fluidized beds — is updated and broadened, and the more manifest knowledge gaps are identified. A systematic classification of the various modes of three‐phase fluidization is presented in order to provide some perspective on the research which has been done and on that which has yet to be done.
Entrained coal gasifiers: Modeling the particle acceleration
Authors: De Lasa H. , Mok L. K.
Published: March 2009

A conceptual model for the design of an entrained bed reactor is proposed in this article. This mathematical model simulates the continuous changes on the properties of both solid and gas phases inside the reactor. The model also computes the required reactor length for a specific coal conversion. Furthermore, a computer simulation is presented to illustrate the crucial continuous particle acceleration resulting of the coal gasification. We believe this effect must be considered for any appropriate particle residence time definition.
Dispersion of aqueous polymer solutions injected from a point source into turbulent water flows
Authors: El Riedy O. K. , Latto B.
Published: March 2009

The dispersion of water and aqueous polymer, when injected from a point source along the flow centre line into two‐dimensional, fully developed and uniform turbulent flows with flow Reynolds numbers of the order of 4.6 × 105, have been studied experimentally. Concentration profiles at five locations were obtained for injection concentrations and velocities in the ranges 0 to 1000 w.p.p.m. and equal to or less than the local flow velocity. The concentrations were assessed using a fluorescing dye technique.

Empirical equations describing the radial and longitudinal concentration field as a function of the injection and flow parameter are given. A universal concentration profile, independent of the injection flow rate and concentration and length of injection source tube, and valid for water and for polymer solution, under both fully developed and uniform flow, is also presented. The results indicate that the turbulent dispersion of polymer solution is suppressed compared to that of water.
Co‐current stratified flow of immiscible liquids: Velocity distribution and pressure gradient in the laminar‐laminar and laminar‐turbulent regimes
Authors: Wang Chester C‐C , Charles M. E.
Published: March 2009

Further studies on the co‐current stratified flow of two immiscible liquids in closed conduits with emphasis on the laminar‐laminar and laminar‐turbulent regimes are reported. Experimental velocity distributions obtained using a photo‐chromic dye technique and pressure gradients for the flow of oil/water and oil/ethanol‐water systems in a rectangular conduit are compared with predictions developed from fundamental concepts. The agreement between the experimental data and the predictions are very satisfactory in both flow regimes. As a consequence, further work should now be focussed on the turbulent‐turbulent regime.
The plug flow model for mass transfer in three‐phase fluidized beds and bubble columns
Authors: Alvarez‐Cuenca M. , Nerenberg M. A.
Published: March 2009

The plug flow model (PFM), overwhelmingly used to describe mass transfer in bubble columns and three‐phase fluidized beds, has never been critically tested. This study analyzes the PFM single parameter, KLa, to quantify mass transfer in the forementioned systems.

Particular attention is paid to the mass transfer features of the zone near the distributor (grid zone) largely ignored until now. This study, carried out under the largest gas and liquid flow rates ever published, for similar types of systems, indicates the presence of two well defined mass transfer zones. These features invalidate, for design purposes, the use of the PFM. However, it still can be used as a qualitative mass transfer indicator. This has permitted a comparison between the mass transfer efficiency of bubble columns and three‐phase fluidized beds with the conclusion that three‐phase fluidized bed of 0.5 cm particles can compete successfully with bubble columns.
Hierarchical control of a train of continuous polymerization reactors
Authors: Kiparissides C. , Ponnuswamy S. R.
Published: March 2009

A multilayer control scheme is synthesized for a series of polymerization stirred tank reactors to control the monomer conversion over the reactor line. In this work two layers of control are implemented. In the' first level digital PI or self‐tuning regulators (STR) are used to control the reaction temperature of each reactor in the series by manipulating the flowrates of the coolant streams. In the second layer, a locally linear state space model, that can predict the monomer concentration in each reactor, is derived based on steady‐state energy balances. A quadratic performance index is then minimized to obtain the optimal reaction profile that will bring the monomer distribution over the reactor line to its desired target value.
Examination of a model for oscillating heterogeneously catalyzed reactions
Authors: Lynch David T. , Wanke Sieghard E.
Published: March 2009

Numerous cases of self‐sustained oscillations have been reported for heterogeneously catalyzed oxidation reactions. For these self‐sustained oscillations, the conversion of reactants varies with time in the absence of external perturbations. Several models have been proposed for these systems. One of these models is based on Langmuir‐Hinshelwood mechanisms involving an adsorbed species which acts as a buffer. Previous predictions based on this model have involved simplifying assumptions. Model predictions without these assumptions are presented in this paper. These results are compared with previously reported simulations.
Some ideas on cracking catalyst design
Authors: Corma A. , Wojciechowski B. W.
Published: March 2009

Progress in understanding the nature of cracking catalysts has led from the early recognition of the carbonium ion intermediate to the current view which ascribes cracking activity to the acidic nature of active sites. Here we develop the concept of acid catalysis to include the specific effects of Bronsted and Lewis acid sites on gas oil cracking. It is shown that these two types of sites react with specific substrates and that each has a characteristic kinetic behaviour. This leads us to suggest that careful control of the total site density and of the proportion of Bronsted/Lewis sites can result in a catalyst which is optimized for the feedstock, reactor configuration, and product distribution desired.
Photocatalytic oxidation of various compounds over TiO2 and other semiconductor oxides; Mechanistic considerations
Authors: Pichat P. , Herrmann J.‐M. , Courbon H. , Disdier J. , Mozzanega M.‐N.
Published: March 2009

A synthesis of studies on the photocatalytic oxidation of various compounds (isobutane, propene, alkyltoluenes, butanols, ammonia, halide ions in aqueous solution) is presented, TiO2 being the main photocatalyst. Comparisons are also made with other n‐type semiconductors: ZrO2, V2O5, Sb2O4, ZnO, SnO2, CeO2, WO3. Information about the mechanism has been obtained by (i) an examination of the photocatalytic isotopic exchange of oxygen in competition with the oxidation of a hydrocarbon, (ii) kinetics and photoconductivity measurements, and (iii) oxidation of butanols by NO. The main conclusions are that these reactions proceed in an adsorbed phase and that dissociated oxygen species play an essential role.
Synergetic effect of molybdenum dioxide on nickel in the catalytic hydrogenation of benzene
Authors: Astier M. , Bertrand A. , Teichner S. J.
Published: March 2009

Molybdenum dioxide is deposited on the form of an aerogel (in the autoclave) on nickel Mond. The catalytic activity for the hydrogenation of benzene into cyclohexane at 100°C depends on the proportion of MoO2 and on the temperature of a pretreatment in hydrogen. When this temperature is 440°C, the catalytic activity exceeds that of pure nickel Mond and exhibits a maximum for about 10% of MoO2. This synergetic effect, which is an exemple of a strong metal‐support interaction (SMSI), is explained by the incorporation into the surface of nickel Mond crystals of molybdenum produced by partial reduction of MoO2, with the formation of an inter‐metallic compound MoNi4.
Optimization of copper chloride based catalysts for ethylene oxyhydrochlorination
Authors: Arcoya Adolfo , Cortes Antonio , Seoane Xose L.
Published: March 2009

In this work we have studied the effect of adding Li, Na or K chloride to CuCl2 supported on α‐Al2O3, on its catalytic activity for the oxyhydrochlorination of ethylene to dichloroethane in a fixed bed reactor, at 573 K and atmospheric pressure. Both NaCl and KCl show a strong promoting effect. For the case of KCl, this effect has been further examined for a wide range of concentrations and a fixed amount of CuCl2 supported on either α‐Al2O3, γ‐Al2O3 or SiO2 gel. The catalytic and thermogravimetric results obtained indicate that KCl is very effective on the overall rate, even at low concentrations, particularly because it increases considerably the rate of reoxidation of the reduced form of the catalyst. In the case of the γ‐Al2O3 series, the promoting effect is only moderate.

Ethylene oxyhydrochlorination data for a series of α‐Al2O3 supported catalysts containing a constant K+/Cu2+ atomic ratio and increasing total amount of KCl + CuCl2 are shown. The activity curve shows a maximum for about 18 wt % total active phase.

Finally, the influence of Ce, Nd and Pr chlorides on the activity of CuCl2 + KCl supported on α‐Al2O3 is also shown. In the case of Pr, the entire range of Pr3+/Cu2+ atomic ratios has been examined. The results indicate that the rare earths, especially praseodymium, also have an additional positive effect on activity.
Estimation of liquid film mass transfer coefficients for columns randomly packed with partially wetted rings
Authors: Ponter Anthony B. , Au‐Yeung Patrick H.
Published: March 2009

A semitheoretical correlation based on an extension of the random length, random angle statistical model of Davidson (1959) is developed which predicts liquid film mass transfer coefficients in a column packed with partially wetted Raschig rings.

The method takes into account the ring size and the mixing which occurs at the packing junctions and allows an estimation of the effective length of a packing piece for a particular liquid viscosity. Predicted values of mass transfer coefficients are in good agreement with the experimental values obtained for the carbon dioxide‐water and carbon dioxide‐aqueous glycerol systems at 25°C reported by Mangers and Ponter (1980b) and other systems reported by Sherwood and Holloway (1940).
Étude des Caractéristiques de l'Ecoulement créé par une Turbine à Barreaux croisés dans une Cellule de Flottation — Influence du Nombre de Barreaux et de la Viscosité du Liquide I. • Détermination de la Capacité de Pompage et de l'Intensité de Turbulence
Authors: Costes J. , Alran C. , Couderc J.P.
Published: March 2009

Les vitesses moyennes, les fluctuations de vitesse, la capacité de pompage, les intensités de turbulence du courant de refoulement d'une turbine à barreaux croisés dans une cellule de flottation ont été déterminés par anémométrie à film chaud à différentes vitesses de rotation. Les influences du nombre de barreaux de la turbine et de la viscosité du liquide ont été étudiées.
Heterogeneous catalysis rate parameters in a gradientless reactor by the method of moments
Authors: Garza‐Tobias G. , Jimenez‐Ocana J. , Rosales M.A.
Published: March 2009

The transient behaviour of an internally‐recycled catalytic reactor has been studied accounting for the contributions from intraparticle diffusion, adsorption and surface reaction. Equations for the zeroth, first and second absolute moments of the break‐through curves are given in terms of the rate constants for the three elementary steps (first order processes are assumed throughout). The moments can be obtained from experimental break‐through curves and the rate parameters for adsorption and surface reaction then evaluated from such data. Simplified equations also are derived for the case of insignificant chemical reaction and this case is used to test the method experimentally. Values of the hydrogen adsorption equilibrium constant for γ‐alumina supported Co Mo‐Ni catalyst are reported.
The chemistry of catalyst poisoning and the time on stream theory
Authors: Viner M. R. , Wojciechowski B. W.
Published: March 2009

It is shown that concentration‐independent decay functions apply over a fairly wide range of poisoning mechanisms in which both products and reactants take some part in poisoning the active sites. The Time on Stream theory is therefore applicable to a wide range of decay mechanisms. In particular, it appears to be ideally suited to catalytic cracking, where the same intermediate carbonium ions are thought to lead to cracking as a main reaction or to poisoning as a side reaction.

Our considerations of the chemistry of poisoning and simulation of catalyst decay behaviour lend credence to the earlier analyses of various kinetic parameters which have been obtained from experimental data using the Time on Stream theory.
Simulation d'un réacteur catalytique à lit fixe (Oxydation du propène)
Authors: Djelveh G. , Gros J. B. , Bugarel R.
Published: March 2009

Un modèle bidimensionnel pseudo‐homogène est utilisé pour l'étude de comportement d'un réacteur catalytique à lit fixe d'oxydation du propène en acroléine. Les lois de vitesses utilisées sont les fonctions puissance de pressions partielles en oxygène et en propène. Les valeurs des paramètres thermiques Pehr et Bi nécessaires à la simulation sont obtenues directement à l'aide des profils de température en l'absence de réaction. Le modèle est intégré par une méthode de collocation orthogonale. Les résultats du modèle, à savoir les profils de températures et la concentration à la sortie du réacteur, sont comparés avec ceux obtenus expérimentalement.
Evaluation of capital cost data: Onsite utilities (industrial gases)
Authors: Woods Donald R. , Anderson Susan J. , Norman SILLS Suzanne L.
Published: March 2009

Capital cost correlations with capacity or with total investment are given for units supplying onsite industrial gases: compressed air, oxygen, nitrogen, inert atmospheres, high purity hydrogen, synthesis gas, ozone and acetylene. Costs are also given for units to remove carbon dioxide and water from gas streams. Correlations available in the literature and current data are compared. Graphs show the relative magnitudes of the different correlations, and the recommended correlation for each type of equipment is given. Some unit usages are given for producing some of the gases.
La flottation de spheres et de cylindres
Authors: Gapany P. , Leidi M. , Hartland S.
Published: March 2009

A study is made of the maximum weight of spherical and cylindrical particles which can be supported by a pendant bubble and at an infinite fluid/liquid interface. The maximum weight increases with the radius, the contact angle (measured through the lower fluid), the density difference between the two fluids and the interfacial tension. It follows that to ensure good flotation suface active agents must be added to increase the contact angle. The maximum particle weight which can be supported at an infinite interface is always greater than that which can be transported there by the pendant bubble.
Reacteur a electrode volumique a lit fixe: Taux de conversion et selectivite
Authors: Ratel A. , Routie R. , Lacoste G.
Published: March 2009

For the purpose of recovering silver from sulfuric acid solution, performance problems of a three‐dimensional electrode operating at sublimiting current are discussed here. Material and charge balances in the reactor lead to three differential equations for concentration, potential and current density, which are solved by a numerical method. In the case of flow from cathode to anode the kinetic term has been found to be constant. Design equations for this kind of reactor have also been established.
Effect of liquid wetting on catalyst effectiveness in trickle‐bed reactors
Authors: Capra V. , Sicardi S. , Gianetto A. , Smith J. M.
Published: March 2009

The liquid in trickle‐bed reactors falls in rivulets down over the catalyst particles. Heretofore, studies of the effect of fractional liquid coverage of the outer surface of the particle on reaction rate have ignored the distribution of the rivulets. A model has been developed in this paper for predicting the effect of number and size of the liquid rivulets. The system of equations has been solved numerically for a first order reaction for two types of reactions: a), one where the rate is determined by the reactant concentration in the liquid, and b), a reaction where the rate is controlled by reactant concentration in the gas phase, as in some hydrogenations.

The results show that intraparticle concentration profiles are strongly affected by the distribution and size of the rivulets. However, for both types of reactions the overall rate, as measured by an overall effectiveness factor, is not significantly affected. This result is important since it suggests that distribution and size of the liquid rivulets may be safely ignored in evaluating the effect of liquid coverage, or wetting efficiency, on the rate of reaction
Flow of stratified slurries through horizontal venturi meters
Authors: Shook C. A.
Published: March 2009

Stratified slurries flowing through horizontal venturi meters are shown to have discharge coefficients higher than values for homogeneous fluids. This effect increases with slurry concentration and decreases as the velocity increases. Predictions using a two‐layer model are qualitatively reasonable but inadequate knowledge of the effect of fluid lift forces makes quantitative prediction difficult.
Hydrodynamic and mass transfer characteristics of bubble and packed bubble columns with downcomer
Authors: Gopal J. S. , Sharma M. M.
Published: March 2009

The hydrodynamic and mass transfer characteristics of bubble and packed bubble columns with downcomer were investigated. The contactor consisted of two concentric columns of 0.11 and 0.2 m i.d., with the annulus acting as the downcomer. The packing used in this investigation was standard 16 mm stainless steel Pall rings. The superficial gas and liquid velocities, VG and VL, were varied from 0.01 to 0.09 and 1 × 10−3 to 8.8 × 10−3 m s−1 respectively.

Two flow patterns, namely the bubble and pulse flows were observed in the packed bubble column with downcomer, as shown by a flow map.

The liquid circulation velocity in both the contactors was observed to be constant throughout the ranges of VG and VL covered in this work. The effect of liquid viscosity (0.8 to 9.5 mPa ṁ s) and surface tension (45 to 72 mN m−1) on the flow pattern, liquid circulation, gas hold‐up and pressure drop was investigated. The pressure drop characteristics across the two contactors have been compared with those across a bubble column.

Values of the effective interfacial area, a, and the volumetric mass transfer coefficient, kL a, were measured by using chemical methods. Values of a as high as 180 and 700 m−1 and kL a as high as 0.075 and 0.22 s−1, in the bubble and packed bubble columns with downcomer, respectively, were obtained. The values of true liquid‐side mass transfer coefficient, kL, were found to be independent of VG and were of the order of 5.5 × 10−4 and 3.5 × 10−4 m s−1, respectively, in the two contactors.
Adsorption de colorants ioniques sur des fibres de laine carbonisees
Authors: Perineau Francis , Farag Karim , Molinier Jacques , Gaset Antoine
Published: March 2009

The study of the adsorption of an acid dye (AB‐80) and of a basic dye (BR‐22) has been carried out on charred woollen fibres, with a view to using that industrial waste material in the treatment of liquid effluents. The authors have first studied the dye diffusion; the diffusion of AB‐80 appeared much slower than that of BR‐22, due to the steric cumbersomeness of the AB‐80 molecule. As a result, the temperature effect on the diffusion, owing to its influence on the dye aggregation, was clearly more pronounced for AB‐80 than for BR‐22; that fact was confirmed by the determination of adsorption isotherms at different temperatures. Under favourable conditions, the curves indicated satisfactory adsorption values; as they were cither of type H (AB‐80) or L (Br‐22), they also indicated the efficiency of the aforesaid fibres in the treatment of slightly‐concentrated effluents. The above finding has been verified by a column treatment of an AB‐80 solution; it then showed the very strong influence of the contact time as well as a wall effect on the effluent purification. In the study conclusion, the results obtained in the treatment of an industrial effluent in a stirred reactor are presented.
Leaching in a bubble‐column slurry reactor
Authors: Reilly I. G. , Scott D. S. , Abou‐El‐Hassan M.
Published: March 2009

Experimental leaching runs were carried out in a continuous concurrent laboratory size bubble column 5.2 cm in internal diameter and 2.90 m tall. The system studied was the dissolution of a synthetic covellite (CuS) in ammoniacal solution in the presence of pure oxygen. Behaviour of the column with respect to gas holdup and solids concentration profiles was measured without reaction by using nitrogen in place of oxygen. Gas holdup values were in agreement with literature results. However, solids concentration profiles for the mixed particle size solid used were of a more complex nature than those obtained for uniformly sized solids.

Conversions obtained at various temperatures and gas and liquid velocities were analyzed in terms of the estimated rates of the individual rate processes occurring. From these results, gas absorption rate was clearly the controlling mechanism at high temperatures, and surface chemical reaction rate was controlling at low temperatures. Hence, the rate controlling steps can be identified in bubble column reactors from currently available literature correlations, together with independent kinetic measurements.
Transient behavior of recycle reactor with consecutive reaction
Authors: Ido T. , Goto M. , Goto S. , Teshima H.
Published: March 2009

Experimental and theoretical transient behavior of a recycle system were studied for a plug flow reactor with a mixing tank and a recycle line. The consecutive reaction chosen for experimental study was the hydrolysis of diethyl succinate through monoethyl succinate to succinic acid on a strong acid ion exchange resin at 50°C. Both realistic and simplified models were developed to simulate the transient behavior of the recycle system. The simplified model was more useful than the realistic model because analytical solutions could be obtained. The approach time to the steady state is presented for the recycle reactor.
Upgrading of delayed and fluid cokes from oil sand by desulfurization
Authors: Hall E. S. , Tollefson E. L. , George Z. M. , Schneider L.
Published: March 2009

Calcination of delayed and fluid oil sand cokes with alkaline reagents at high sodium/sulfur ratios followed by leaching gave almost complete desulfurization in terms of gaseous combustion products. Use of smaller proportions of alkaline reagents with hydrodesulfurization at 650 to 850°C also resulted in extensive removal of sulfur as hydrogen sulfide.
Coating flows with interfacial air drag. A nonlinear theory
Authors: Nigam K. D. P. , Esmail M. N.
Published: March 2009

The problem of the coating flow of a Newtonian liquid under the influence of a contiguous air flow is considered. The effect of the air flow is simulated by a constant tangential viscous shearing, calculated as the average skin friction per unit area of a boundary layer air flow over a smooth flat plate. Predictions are obtained for the liquid flow characteristics in cases of cocurrent and countercurrent forced air flows. Significant changes in the liquid film thickness start to occur when the absolute value of a dimensionless shearing number, Tn, exceeds 0.01. This value is not sensitive to the other flow parameters. The study is limited to low and moderate liquid Reynolds numbers, when the surface tension forces have considerable to noticeable effect.
Studies of the behavior of disturbance waves in annular two‐phase flow
Authors: Nencini Franco , Andreussi Paolo
Published: March 2009

Downward annular two‐phase flow (air‐water) has been examined experimentally. Statistical methods have been applied to calculate the flowrates associated with the hypothetical substrate flow and large wave flow. Agreement with actual Jiquid flowrates under varying gas flows is good. The constant thickness assumption is shown to give significant error. Main characteristics of large waves have also been determined.
Thermodynamics of ion exchange as an adsorption process
Authors: Novosad J. , Myers A. L.
Published: March 2009

A thermodynamic description of adsorption from liquid solutions can be used as a basis for a rigorous thermodynamic treatment of ion exchange. Previous treatments were based upon the implicit assumption that the resin phase contains only fixed ionic groups and bound counter‐ions. However, porous ion exchangers can also absorb (or adsorb) the solvent and electrolytes dissolved in it. The observed selectivity of the exchanger depends upon the amount of solvent adsorbed, so that the definition of the boundary (Gibbs dividing surface) between the solid exchanger and the bulk liquid solution becomes important. Instead of the usual counter‐ion selectivity, the variable which describes the uptake of electrolyte is the equivalent of the surface excess. This paper is concerned with the definition and properties of this variable and with the development of an integral thermodynamic consistency test.

On peut faire un traitement thermodynamique rigoureux de l'échange d'ions en utilisant une description thermodynamique de l'adsorption à partir de solutions liquides.
Mass transfer modelling for GS heavy water plants: Part 1: Point efficiency on GS sieve trays
Authors: Neuburg H. J. , Chuang K. T.
Published: March 2009

A model that takes into account the gas‐phase and liquid‐phase resistance to mass transfer has been developed, where the overall mass transfer coefficient (KOGa) is expressed as a function of the equivalent Sauter‐mean bubble diameter. This parameter was back calculated from mass transfer measurements made at a pilot plant on single pass sieve trays of 0.311 m diameter. Hydraulic parameters were measured for these trays as well. Mean bubble diameters were then correlated as a function of active area F‐factor and dispersion height for various tray geometries, and these correlations are used to predict point efficiencies on production plant trays up to 8.5 m in diameter.
Optimum performance data for the leaching of roasted chalcopyrite concentrate in a jet contactor
Authors: Jain R. C. , Madhavan S. , Acharjee D. K. , Gupta P. Sen
Published: March 2009

Chalcopyrite concentrate has been roasted in a mullite tube furnace and the optimum temperature of roasting determined. The roasted concentrate has been leached with dilute sulphuric acid in a jet contactor. Optimum performance data for leaching, namely temperature, particle size, slurry concentration, acid concentration, nozzle diameter and effective contactor height have been obtained. For predicting the copper concentration in the leached solution, an expression based on a diffusion model has been derived and compared with the experimental data. It has been observed that at low values of mixed phase velocity, the agreement is good, but at high values, the variation is relatively larger.
Combustion of low heating value fuels and wastes in the spouted bed
Authors: Arbib H. A. , Levy A.
Published: March 2009

In a spouted bed burner, the flow‐maintained vortex of particles operates as a heat exchanger, preheating the incoming mixture without diluting it. This makes it a combustor especially attractive for incinerating low heating value fuels and wastes.

Bench‐scale experimental studies were carried out to assess the ability of the spouted bed to burn efficiently poor fuels and waste materials in various aggregative states. The paper reports results of two series of experiments with gaseous and liquid fuel‐containing streams. High levels of hydrocarbon conversion and combustion efficiency were attained for mixtures that would not be combustible by other methods without an auxiliary fuel.
Computer control of holdup in a reciprocating plate extraction column
Authors: Taylor P. A. , Baird M. H. I. , Kusuma I.
Published: March 2009

This paper describes the application of computer control to a pilot scale (15 cm diameter) Reciprocating Plate Solvent Extraction Column. The system under investigation was kerosene dispersed in water without mass transfer between the phases. The control objective was the regulation and set point tracking of the holdup of the dispersed phase.

Dynamic tests showed that the column was a non‐minimum phase, dead‐time process with asymmetric, non‐linear gains and time constants.

Fixed parameter controllers of increasing complexity; PID, Dahlin algorithm, and minimum variance, were compared to an adaptive controller, the self tuning regulator. These controllers were applied in feedback and combined feedback‐feedforward configurations.
A one‐dimensional model of plug flow pneumatic conveying
Authors: Chan Shu‐Ming , Remple D. , Shook C. A. , Esmail M. N.
Published: March 2009

A one‐dimensional model of pulse or plug flow is proposed. This type of flow is observed at high mass ratios of solids to gas and requires gas velocities orders of magnitude less than dilute phase systems.

Plug stability criteria are examined by considering the axial interparticle stresses within single plugs and the effect of the radial transmission of these stresses on wall friction. Establishment of the fluid pressure gradient within the plug and the existence of a settled layer of solids in the interplug space are shown to be important requirements.

These concepts are used in the formulation of an empirical pressure drop equation which is used in the correlation of experimental data. Comparison of predicted and experimental values is reasonable for the air‐sand system considered.

The model should be of value in the planning and interpretation of future experimental studies.
Transfert de chaleur entre une couche fluidisee bidimensionnelle et une paroi
Authors: Granier M. , Riba J. P. , Couderc J. P.
Published: March 2009

Heat transfer between a wall and a two‐dimensional fluidized bed has been studied. The fluidized bed remains isothermal for thicknesses as small as 8 mm, with significant values of the heat transfer coefficient up to the wall of the column.

The bubbling properties in the two‐dimensional bed have been recorded using a rapid cine camera. These data have been used to test several heat transfer models. A convenient agreement has been obtained when taking into account a wall contact resistance term.
Evaluation et comparaison des parameters de la dispersion axiale dans les deux phases d'une colonne extraction à plateaux alternatifs
Authors: Bensalem A. , Steiner L. , Hartland S.
Published: March 2009

The impulse response technique for the injection of a tracer has been applied to both liquid phases in a pilot plant sized reciprocating plate extraction column of the type introduced by Karr. The responses obtained have been interpreted using the piston flow model, and employing three analysis techniques to determine the Péclet number, Pe, and the residence time, π, namely the moments method, the least‐squares method in the time and frequency domains and the Vergnes' method.

The least‐square method was found to give the most coherent results, even for the dispersed phase, because this method is less sensitive to instrument drift (noise) than the two other methods.

The piston flow model successfully described and correlated the longitudinal mixing in the continuous phase, and fairly well for the dispersed phase.