bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlations for prediction of molecular diffusivities in liquids at infinite dilution
Authors: Wong C. F. , Hayduk W.
Published: March 2009

Diffusivities measured at 278.2 K to 323.2 K are reported for propene in acetic acid, acetone, n‐butanol, chloroben‐zene, N, N dimethyl formamide, ethyl acetate and n‐octane. Measurements were made utilizing the steady‐state capil‐lary cell method. It was found that the diffusivities were reduced in the associating solvents when compared with those obtained in non‐polar solvents at the same temperature. Three new empirical correlations have been developed for the prediction of diffusivities in liquids at infinite dilution and these are: for n‐alkane solutions, for dissolved gases in organic solvents, and for dissolved gases in water.
Process control: An overview and personal perspective
Authors: Fisher D. Grant
Published: March 2009

This paper presents an overview and personnal perspective on recent developments and current practice in computer process model. The basic concepts behind conventional process control are reviewed to provide a starting point for the non‐control specialist and process engineer. The ensuing sections on Internal Model Control (IMC), Model Predictive Control (MPC) and adaptive control illustrate the evolution of control technology from the traditional multiloop strategies to the modern, multivariable, model‐based, computer control systems now being used in industry. The paper does not provide a complete, critical review of process control. However, the discussion and the recommended references should provide a good starting point for anyone wanting to become familiar with current practice and some of the new directions of process control.
Feedback control of crystal size distribution in a continuous cooling crystallizer
Authors: Rohani S. , Paine K.
Published: March 2009

Control of crystal size distribution (CSD) in a 21.8 L continuous cooling KCl crystallizer was attempted. Feed saturated at 54°C with potash, nearly saturated with NaCl and containing 0.75 g MgSO4/100 g of H2 O was cooled to the crystallizer temperature at 40°C. The control scheme consisted of a proportional‐integral controller with the rate of fines dissolution/removal as the input variable and the fines suspension density (crystals smaller than 150 μm) as the output variable. The measured/controlled variable was a temperature difference, ΔT, corresponding to the temperature of a slurry sample containing representative fines, before and after the fines were dissolved by heating. An increase in the product weight‐mean crystal size and a decrease in the coefficient of variation of product were observed in the controlled runs.
Experimental studies on heat transfer with phase change on diverging‐converging surfaces
Authors: Chakravarty T. K. , Narayanan C. M. , Bhattacharyya B. C.
Published: March 2009

Attempts have been made to study experimentally condensation of pure vapours on the inside surfaces of vertical diverging‐converging tubes. The work highlights the significant augmentation in heat transfer efficiency achievable in film condensation on surfaces that are of diverging‐converging geometry. The dependence of the augmentation phenomena on the geometric characteristics of the heat transfer surface, such as angle of constriction and number of segments in series, and also on the operating parameters such as fluid flow rate and fluid inlet temperature, is also discussed.
Mathematical modelling of protein diffusion in microcapsules: A comparison with experimental results
Authors: Kwok W. Y. , Kiparissides C. , Yuet P. , Harris T. J. , Goosen M. F. A.
Published: March 2009

The objective of this study was to develop a general diffusion model for describing mass transport phenomena and membrane diffusivities in alginate—polylysine (PLL) microcapsules. Good agreement between calculated and experimental protein concentration profiles was obtained based on a microcapsule model, consisting of a capsule membrane containing a partially impermeable alginate gel core with a decreasing gel pore size towards the centre of the capsule. The apparent size of the impermeable gel core and the capsule membrane permeability were directly dependent on the size of the diffusing protein and the alginate‐PLL reaction time. The presence of this impermeable core may hinder the commercial and clinical use of these microcapsules in cell culture engineering and cell transplantation by affecting cell viability.
Animal cell bioreactors — recent advances and challenges to scale‐up
Authors: Hu Wei‐Shou , Peshwa Madhusudan V.
Published: March 2009

The demand for animal cell derived products has stimulated the development of bioreactors in the last decade. Most of those developments allow a higher cell concentration to be achieved in the bioreactor than in the past, primarily by means of the continuous flow of culture medium and a mechanism of cell retention. The advantages and technological challenges of some of these developments are discussed. Lagging behind the bioreactor developments is the strategy for culture operation and optimization. The need for suitable kinetic models to describe animal cell growth is emphasized.
Adaptive neural models for on‐line prediction in fermentation
Authors: Van Breusegem Vincent , Thibault Jules , Chéruy Arlette
Published: March 2009

This paper deals with on‐line prediction of fermentation variables by neural network techniques. It is shown that the accuracy of the on‐line prediction based on a neural model, obtained from an initial learning sequence, decreases when kinetic changes occur during the course of the fermentation. Therefore, sliding window learning schemes are proposed. For a given network structure, the proposed learning procedures progressively refresh the knowledge integrated within an initial neural model. The influence of the length of the learning window, the number of iterations and the initial neural model on the predictive accuracy of adaptive neural models are investigated. Sliding window learning schemes can be also used when fermentation measurements are delayed and/or infrequent.
Suspension codeposition in electrowinning cells: The role of hydrodynamics
Authors: Graydon J. W. , Kirk D. W.
Published: March 2009

Electrolytic codeposition of particles suspended in a plating bath constitutes a novel method for producing certain alloys. The suitability of this approach for the manufacture of copper‐phosphorus alloy from a suspension of red phosphorus in acid copper sulphate solution was assessed in a scaled, full‐depth, transparent electrowinning cell operated continuously. The suspension was maintained both by the jetting of recirculated electrolyte and by the natural flows of electrolyte and anodic bubbles. Smooth thick deposits of copper containing acceptably uniform, optimal levels of phosphorus were produced. The vertical variation of phosphorus in the cathode is explained by a detailed consideration of hydrodynamic flow near the cathode.
An application of a cascaded self tuning regulator to a karr solvent extraction column
Authors: Camvrdan M. C. , Taylor P. A. , Baird M. H. I.
Published: March 2009

An application of a cascaded Clarke‐Gawthrop self tuning regulator (STR) to a Karr liquid‐liquid solvent extraction column is presented. The Karr column, a reciprocating plate column, exhibits nonlinear asymmetric responses which are complex functions of the operating conditions and requires adaptive control in order to prevent instability. The outer loop of this cascade scheme controls the extract concentration of the continuous phase while the inner loop controls the hydrodynamic holdup in the column and prevents flooding. The manipulated variable was the frequency of reciprocation. The STR‐STR cascade arrangement is compared with a fixed parameter Proportional plus Integral (PI) controller in the outer loop and an STR in the inner loop.
Bulk polymerization in tubular reactors I. Experimental observations on fouling
Authors: Cunningham M. F. , O'Driscoll K. F. , Mahabadi H. K.
Published: March 2009

Conditions under which fouling (polymer deposition) occurs in tubular polymerization reactors were studied using bulk methyl methacrylate polymerizations at 70°. It was demonstrated that reactor orientation and flow direction have a significant effect on fouling behaviour. Natural convection becomes increasingly important as concentration gradients in the reactor increase. Using the optimum reactor configuration determined in the first part of the study, a feasible operating region for the reactor was established, thereby permitting selection of conditions which will prevent reactor fouling.
The influence of aluminum alkyls on the polymerization of ethylene with SiO2/MgCl2‐supported TiCl4 catalysts
Authors: Lynch David T. , Jejelowo M. Olukayode , Wanke Sieghard E.
Published: March 2009

The influence of different aluminum alkyls (diethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri‐n‐hexylaluminum, tri‐n‐octylaluminum and isoprenylaluminum) on the ethylene polymerization activity of a laboratory prepared high‐activity SiO2/MgCl2‐supported TiCl4 catalyst has been investigated. A slurry reactor (decane diluent) was used for measuring rates of polymerization. The average molar mass, the breadth of the molar mass distribution, the polymerization activity, and the shapes of the activity‐time profiles, were strongly dependent on the nature of the aluminum alkyl. For several of the cocatalysts used, the catalytic activity approached a constant value after a certain amount of time under reaction conditions. In this constant activity region, a first‐order dependence of the polymerization rate on the monomer concentration was found for all of the systems examined. However, the activation energy of the polymerization reaction was found to depend strongly on the type of cocatalyst which was used.
CO2 gasification kinetics of two alberta coal chars
Authors: Kovacik G. , Chambers A. , Özüm B.
Published: March 2009

CO2 gasification kinetics of chars from two Alberta coals (Obed Mountain, high volatile bituminous and Highvale, subbituminous) have been studied using a thermogravimetric analyzer (TGA) and a fixed bed reactor. Charification and gasification reactions were performed sequentially in both the TGA instrument and in the fixed bed reactor to simulate real gasifier operating conditions. TGA and fixed bed data were processed numerically to evaluate the kinetic rate of CO2 gasification of the chars. Calculated gasification kinetics could be correlated using both the volume reaction and the grain models. Activation energies of the kinetic rate constants were near 200 kJ/mol for both Highvale and Obed Mountain coal chars using the TGA data. The activation energies calculated for the Obed Mountain coal char using the fixed bed reactor were about 250 kJ/mol. For all the cases studied the calculated activation energies were nearly the same for both the volume and grain reaction models.
Modelling of circulating fluidized bed combustion of a char
Authors: Arena Umberto , Malandrino Alberto , Massimilla Leopoldo
Published: March 2009

The combustion of a char in the 41 mm ID riser of a laboratory circulating fluidized bed combustor has been investigated at different air excesses and rates of solids (char and sand) circulating in the loop. Riser performance was characterized by an axial oxygen concentration profile as well as by the overall carbon content and particle size distribution. The proposed model accounts for carbon surface reaction, intraparticle and external diffusion, and attrition. External diffusion effects were relevant in the riser dense region where char was potentially entrapped in large clusters of inert solids. Experimental data and results of the model calculations are in satisfactory agreement.
A fluidized bed membrane reactor for the steam reforming of methane
Authors: Adris A. M. , Elnashaie S. S. E. H. , Hughes R.
Published: March 2009

In the present investigation a realistic two‐phase model accounting for the change in the total number of moles accompanying the reaction is utilized to explore a novel reactor configuration suggested for the methane steam reforming process. The suggested design is basically a fluidized bed reactor equipped with a bundle of membrane tubes. These tubes remove the main product, hydrogen, from the reacting gas mixture and drive the reaction beyond its thermodynamic equilibrium. The proposed novel design is also equipped with sodium heat pipes which act as a thermal flux transformer to provide the large amount of heat needed by the endothermic reaction through a relatively small heat transfer surface, assuring better reactor compactness. Two options for fluid routing through the membrane tubes are proposed; each is suitable for a certain industrial application. The performance of this novel configuration is compared with that of an industrial fixed bed steam reformer and the comparison shows the potential advantages of the suggested configuration.
Kinetics of desulfurization of hydrogen sulfide using metallic copper as a desulfurizer
Authors: Chen Qiyuan , Li Lili , Hepler Loren G.
Published: March 2009

The kinetics of desulfurization of hydrogen sulfide, using metallic copper as desulfurizer, have been investigated over a range of temperatures and pressures of hydrogen sulfide. Our results indicate that there are two stages of reaction; activation energies for the first and second stages are 63 kJ/mol and 38 kJ/mol, respectively. Possible reaction mechanisms in which the initial rate is controlled by interface reaction and the later stage is controlled by diffusion through or in the Cu2S layer are consistent with the experimental data.
Axial mixing and mass transfer in a vibrating perforated plate extraction column
Authors: Baird M. H. I. , Rao N. V. Rama , Vijayan S.
Published: March 2009

The axial mixing and countercurrent mass transfer characteristics of a 5 cm diameter extraction column agitated by vibrating perforated Teflon plates have been investigated. The dispersed phase was an organic liquid (usually kerosene) and the continuous phase was water. Axial mixing was measured in both phases using pulse tracer techniques; in the continuous phase the axial mixing was estimated to have a significant effect on mass transfer, but axial mixing in the dispersed phase had a negligible effect. Mass transfer was measured for several different solutes; n‐butyric acid, benzoic acid and phenol. The overall heights of a transfer unit (cont. phase) were in the order of 10‐20 cm for the organic‐acids but higher for transfer of phenol from very dilute solutions. The characteristics of the vibrating plate column have been compared with those of other types of extractor and suggestions are made for further development.
Modeling and application of a semibatch coaxial two‐impinging‐stream contactor for dissolution of solids
Authors: Tamir Abraham , Glitzenstein Azar
Published: March 2009

A semibatch, coaxial, two‐impinging‐stream (TIS) contactor was developed and tested for dissolving solid particles of sodium‐nitrate, sodium‐nitrite and urea in water. The feature of the contractor lies in the possibility of increasing and controlling the mean residence time of the particles in the reactor.

The mass transfer coefficients determined in the semibatch device, where the water was in a continuous flow and the particles remained in the reactor for a certain period of time, can also be applied to a continuous TIS device. The comparison of mass transfer coefficients with values of other well‐known devices indicated that they are among the highest and that the present contactor is very effective.

A physical model was established for the behaviour of the dissolving particles which yielded a two‐parameter correlation for predicting the Sherwood number as a function of the operational parameters.
Absorption of carbon dioxide in alkanolamines in the presence of fine activated carbon particles
Authors: Saha A. K. , Bandyopadhyay S. S. , Biswas A. K.
Published: March 2009

The rates of absorption of CO2 into water and 0.1 kmol/m3 aqueous solutions of MEA, DEA and AMP were measured in a stirred cell with a flat gas‐liquid interface in the presence of fine activated carbon particles. Experiments showed that the rates of absorption increased significantly with increases in the loading of activated carbon up to about 6 kg/m3 and thereafter remained constant.
Hydrogenation activity of an amorphous Pd‐Zr alloy held in an alumina matrix
Authors: Takahashi Takeshige , Abe Kazumasa , Kai Takami , Kimura Hisamichi , Masumoto Takeshi
Published: March 2009

The hydrogenation of benzene has been carried out over a catalyst prepared from an amorphous Pd‐Zr alloy held in an alumina matrix. The catalytic activity was compared with that over the alloy cut into 1 mm fragments. It was found that the fixed alloy in the alumina had not only higher catalytic activity, but also a smaller catalyst fouling rate than the fragments of the alloy.

The effect of palladium content in the amorphous alloy on the hydrogenation activity was examined. It was found that the initial activity increased with the fraction of palladium. However, the activity of the catalyst which had the highest palladium content decreased with repeated regeneration and reaction, whereas the activity of the other catalysts reached a stable value.
Minimum fluid flowrate, pressure drop and stability of a conical spouted bed
Authors: Povrenovié D. S. , Hadžismajlovié Dž E. , Grbavčić Ž B. , Vuković D. V. , Littman H.
Published: March 2009

A model for calculating the minimum spouting flowrate and pressure drop in a conical spouted bed has been developed and described in our previous paper (Hadžismajlovi et al., 1986). In the present work, this model was examined at a wider range of experimental conditions and it was found that measured and predicted values of the minimum spouting flowrate and pressure drop differed by about 10.3% and 20.0%, respectively.

It is shown that the spouted bed in a conical column is stable when the inlet tube diameter is less than 25 particle diameters.
Carbon monoxide hydrogenation over cobalt catalyst in a tube‐wall reactor: Part 1. Experimental studies
Authors: Dalai Ajay K. , Bakhshi Narendra N.
Published: March 2009

Effects of temperature (250−275°C), pressure (0.1‐1.03 MPa) and feed gas exposure velocity (139‐722 μm/s) were studied on carbon monoxide hydrogenation in a tube‐wall reactor using plasma‐sprayed cobalt catalyst. The specific catalytic activity and hydrocarbon selectivity increased with an increase in pressure and temperature and a decrease in the exposure velocity. The results showed that the formation of olefins especially ethylene and propylene was favored at low pressures, low temperatures and high exposure velocities. This catalyst was found to be selective for C5+ hydrocarbons (27‐34 wt.%) at increased pressures (0.69‐1.03 MPa).
The behavior of ethylene glycol during the thermal solvolysis of cellulose
Authors: Vidal Pierre F. , Garnier Gil , Bouchard Jean , Overend Ralph P. , Chornet Esteban
Published: March 2009

The composition of the ethylene glycol solution resulting from cellulose thermal solvolysis, to produce microcrystal‐line cellulose, has been studied. Liquid and gas chromatographic analyses showed, a) little degradation of the ethylene glycol up to 280°C, and b) an acceleration of the degradation at higher temperatures in the presence of cellulose and glucose. Solubilized compounds resulting from the cellulose depolymerization although numerous were present in too low concentrations to warrant their recovery.
Feedback linearizing control of a fluidized bed reactor
Authors: Perrier M. , Aoufoussi H. , Chaouki J. , Chavarie C. , Dochain D.
Published: March 2009

The design of an adaptive nonlinear controller for the control of a fluidized bed reactor is derived by using exact linearization techniques. Reset action and parameter adaptation are used to make more robust the precise compensation of nonlinear terms, which is called for in the linearization technique. A nonlinear antiwindup mechanism is introduced to handle reset windup problem and to provide fast response without large overshoot. Simulation results show that the proposed adaptive controller guarantees good setpoint tracking. The developed estimation algorithm allows accurate estimation of the parameters for which the regressor component is not zero.
An interior point method implementation for solving large planning problems in the oil refinery industry
Authors: Ponnambalam Kumaraswamy , Vannelli Anthony , Woo Stephen
Published: March 2009

Multi‐period planning problems in the oil and refinery industry are typically large, sparse, staircase/band diagonal structured and nonlinear optimization problems. Successive linear programming (SLP) type methods have been widely used for solving these planning problems. But, it has long been recognized that the simplex method used in solving linear programs requires a large number of iterations for staircase/band diagonal structured problems. In this paper, we report results of an application of a recently developed interior point method that promises to be many times faster than the simplex method for multi‐period planning problems. However, to facilitate the use of interior point method in the current SLP algorithms a hybrid method combining the interior point method and the simplex method is developed. Therefore, the results determined with this hybrid method are qualitatively equivalent to that obtained with the simplex method alone. The CPU times corresponding to the hybrid method are compared with the CPU times of simplex and dual affine methods. The new hybrid method generates a basic feasible solution of the linear programming problem and is approximately 7 times faster than the simplex method on the tested planning problems. Moreover, the interior point and hybrid methods become faster as the problem size increases.
Effect of liquid viscosity on gas holdups in a reversed flow jet loop reactor
Authors: Padmavathi G. , Rao K. Remananda
Published: March 2009

The effect of draft tube diameter and liquid viscosity on overall and annulus gas holdups were studied in a reversed flow jet loop reactor. The draft tube diameter to reader diameter ratio (Dd / D) and liquid viscosity were varied in the ranges 0.34‐0.67 and 1.5‐43 mPa. s, respectively. The maximum gas holdup was obtained when the Dd / D value ranged btween 0.47 and 0.61. The gas holdup decreased with increasing viscosity. Empirical correlations are presented to predict the gas holdups.
Application of gas‐liquid chromatography to the study of gas‐bitumen interactions
Authors: Smith John , Patterson Donald
Published: March 2009

Gas‐liquid chromatography (glc) has been used (Xu and Hepler, 1990) to obtain Henry's Law constants and infinite dilution activity coefficients for hydrocarbon and other vapour‐phase solutes in two bitumens, Athabasca and Wolf Lake. Thermodynamic interaction between components widely different in molar mass can, however, be characterized by mass‐fraction rather than mole‐fraction based quantities and by the χ parameter, as has been the practice with polymer systems. The new parameters have been calculated and reveal more unfavorable interactions of the solutes with Wolf Lake than with the Athabasca material.
Multi‐dimensional model of a spouted bed
Authors: Krzywanski R. S. , Epstein N. , Bowen B. D.
Published: March 2009

A multi‐dimensional model is developed to describe the fluid and particle dynamic behaviour of spouted beds. The position of the spout‐annulus interface is determined by a variational analysis. Two‐fluid equations are used to represent gas and solids motions in the spout while the vector Ergun equation and soil mechanics equations are employed to describe, respectively, gas and solids behaviour in the annulus. Using numerical finite difference methods, the set of governing equations is solved subject to carefully chosen boundary conditions. The model predictions of key hydrodynamic characteristics are in reasonable agreement with available measured data selected from the literature to represent a wide range of experimental conditions.
Effects of fuel type and operating conditions on SO2 emission in fluidized bed combustion
Authors: Zhang J. Q. , Jones W. E. , Lav I. T. , Friedrich F. D.
Published: March 2009

The SO2 emission from six fluidized bed combustors was examined. Approximately 71.5% of the fuel sulphur was found to be emitted as SO2 in sorbent‐free tests. General observations on the effects of Ca/S molar ratio, limestone size and recycle systems are presented. The effects of limestone type and superficial velocity were found to be insignificant, as was the effect of bed temperature in the range 800‐950°C. In tests with fine solid and liquid fuels, circulating FBC's were found to provide significantly better sulphur capture than bubbling FBC's.
Précipitations sélectives des métaux solubilisés biologiquement de boues aérobies d'épuration
Authors: Couillard D. , Mercier G.
Published: March 2009

La précipitation sélective et successive des métaux provenant de la solubilisation biologique (Thiobacillus ferrooxidans) des métaux des boues d'épuration a été étudiée. En parallèle, des figures théoriques représentant la solubilité des hydroxydes et des carbonates des métaux (Ca, Mg, Fe, Al, Cu, Zn, Ni, Cd, Mn) et de leur complexes sont comparées aux valeurs expérimentales. Le pH a été augmenté par étapes à l'aide de Ca(OH)2. Le précipité d'hydroxyde de fer, le moins contaminé, fut obtenu à pH 3.5. Les pH théoriques de précipitation acceptable des métaux ont été identifyés comme: Fe+3 à pH 3.2, Al+3 À pH 4.7, Cu+1 é a pH 6.9, Zn+2 à A pH 8.15, Ni+2 à pH 8.4 et Mn+2 a pH 9.1 et s'approchent des valeurs théoriques. L'ion hydroxyde contrǒle la solubilité de Ca, Mg et Cu. Un précipité avec environ 20% de Cu peut étre obtenu à pH 7 aprés que l'hydroxyde ferrique ait été précipité. La récupération des métaux autre que le fer est donc possible.
Kinematic viscosity studies of the binary ethane‐ 1,2‐diol/ n, n‐dimethylformamide solvent system at various temperatures
Authors: Corrandini Fulvio , Marchetti Andrea , Tagliazucchi Mara , Tassi Lorenzo , Tosi Giuseppe
Published: March 2009

Kinematic viscosity data (ν) are presented for ethane‐1,2‐diol, for N, N‐dimethylformamide and for nine binary mixtures in the ‐ 10°C to 80°C temperature range. The experimental data were fitted by several empirical relations such as Grunberg‐Nissan (1949), McAllister (1960), Heric (1966), Lobe (1973), Auslander (1964) and polynomial equations. Some considerations regarding the meaning of the obtained adjustment parameters are made. Furthermore, a new best fit equation is proposed and its validity has been compared to that of the other relations on the basis of the reproducibility of the experimental data.
Phase equilibria of crude oils using the continuous thermodynamics approach
Authors: Koral Sunil L. , Sayegh Selim G. , George Albert E.
Published: March 2009

This paper deals with the application of continuous thermodynamics to light and heavy oil systems using the Peng‐ Robinson equation of state. The composition of the high molar mass components in a reservoir oil is described by a continuous distribution function of some characterizing quantity, e.g. molar mass or boiling temperature. Numerical Gaussian quadrature methods are used to generate pseudo‐components and their mole fractions from distribution data. Several examples are presented for phase equilibria of solvent/crude oil systems. The results showed that semi‐infinite distribution functions, such as the Γ function, cannot be applied to all cases, e.g. dew point calculations. The Gauss‐ Legendre quadrature method coupled with spline fitting worked best for heavy oil systems.
A three‐dimensional finite element analysis of the effect of reynolds number on extrudate swell of newtonian liquids from square dies
Authors: Gifford W. A.
Published: March 2009

The effect of Reynolds number upon the extrusion of a Newtonian fluid exiting a square die is examined. It is shown that the extrudate swells at low Reynolds number but contracts at high ones. At zero Reynolds number, the maximum die swell ratio of 1.2 occurs. A swell ratio of one occurs at a Reynolds number of about 24. At large Reynolds numbers, the extrudate contracts to a circular cross‐section with a swell ratio of 0.9611.
Non‐darcy forced convective heat transfer in a channel embedded in a non‐newtonian inelastic fluid‐saturated porous medium
Authors: Nakayama A. , Shenoy A. V.
Published: March 2009

The present analysis investigates non‐Darcy forced convective heat transfer in a channel confined by two parallel walls subjected to uniform heat flux in a highly porous medium saturated with a non‐Newtonian power‐law fluid. Extensive numerical integrations have been carried out utilizing the Brinkman‐Forchheimer extension of the Darcy model in order to study the effects of pseudoplasticity, and Brinkman and Forchheimer terms on the heat transfer characteristics.
Extraction of phenols: Ii. distribution data for binary and multicomponent mixtures of phenols, countercurrent extraction performance and model validation
Authors: Bízek V. , Hor áč J. , Koušová M. , Komers R. , Proch ázka J. , Heyberger A.
Published: March 2009

The distribution of binary mixtures of phenol with o‐, m‐ or p‐cresol between aqueous solutions of NaOH and toluene or methyl‐isobutyl‐ketone (MIBK) was investigated. A mathematical model of the distribution was formulated and its parameters were evaluated for each phenol/cresol/solvent combination. The extraction of phenolics from a coal tar fraction with aqueous solutions of sodium phenates was carried out in a countercurrent cascade of four equilibrium stages. The back extraction of phenolics from the aqueous extract was carried out as a triple extraction with pure solvent. A mathematical simulation of the multicomponent, multistage experiments was realized with the DOOM algorithm using an extension of the equilibrium model, formulated for binary mixtures.
Modélisation numérique du transfert de matière dans un écoulement annulaire faiblement tourbillonnaire non‐entretenu
Authors: Legentilhomme P. , Legrand J.
Published: March 2009

Ce travail est consacré à la modélisation de ľhydrodynamique et du transfert de matière lors de ľécoulement tourbillonnaire laminaire produit par une entrée tangentielle dans un espace annulaire cylindrique. Les équations du mouvement et de diffusion‐convection, simplifiées en utilisant la théorie de la couche limite, sont résolues par une méthode implicite aux différences finies. Bien que cette mèthode ne permette pas de traiter les écoulements fortement tourbillonnaires ou ceux où se produisent des phénomènes de recirculation, ce travail nous a cependant permis de soulever un problème intéressant quant à la validité des hypothèses de la théorie de la couche limite pour la détermination du transfert de matière pour des nombres de Schmidt élevés.
Residence time distribution analysis from a continuous couette flow device around critical taylor number
Authors: Pudjiono P. I. , Tavare N. S.
Published: March 2009

This paper presents an experimental study of residence time distribution (RTD) analysis by pulse response technique in a continuous Couette flow device with rotating inner cylinder and stationary outer cylinder. Two kinds of experimental tests using pulses of tracer dye solution and particles resulting from a fast precipitation were performed in the region near the critical Taylor number characterizing boundary between laminar and laminar vortex flow. For most experiments performed in laminar and laminar vortex flow regime around the critical Taylor number over the ranges 0 < Ta < 120 and 0 < Re < 5.5 the normalized response can be described by a dispersion model. The results of the critical Taylor number as characterized by the minimum dispersion number appear consistent with both theoretical predictions and other empirical observations.
Electrodeposition of catalytically active nickel for the oxygen evolution reaction — effects of anionic composition
Authors: Miao H. J. , Piron D. L.
Published: March 2009

Nickel electrodes were prepared by electrodeposition in electrolytes of various anionic compositions. The deposition conditions and bath types were evaluated with special emphasis on the electrocatalytic properties for the oxygen evolution reaction (OER). Electrochemical characterizations in a 5 mol/L KOH solution at 25°C showed that the electrode deposited from the chloride bath, having a low Tafel slope of 50 mV/dec and an overpotential of 396 mV at 100 mA/cm2, is the most catalytically active among electrodes prepared in electrolytes of various anionic compositions. The electrode activity for the OER is related to the real surface areas, which depend on the anion compositions in the deposition bath and the deposition conditions.
A cubic simplified perturbed hard‐chain equation of state for fluids with chainlike molecules
Authors: Wang Li‐Sheng , Guo Tian‐Min
Published: March 2009

The simplified version of the perturbed hard‐chain theory (SPHCT) developed by Kim et al. (1986) is modified by reformulating the attractive portion of the canonical partition function for mixtures, and replacing the repulsive portion by a simple simulated expression. The final equation of state developed is cubic in volume. The test results on pure fluids, binary/multi‐component mixtures and reservoir fluids indicate that the CSPHC EOS retains the advantages of the original PHCT, and significant improvements over the SPHCT in predicting the VLE of heavy hydrocarbon‐containing/CO2‐containing mixtures, and liquid phase density are observed.
Performance assessment measures for univariate feedforward/feedback control
Authors: Desborough Lane , Harris Thomas
Published: March 2009

An analysis of variance for univariate feedforward/feedback systems has been derived which allows the variance contributions due to both disturbances and controllers to be established. A performance index which assesses the performance of the overall control scheme has been developed. Estimates of the analysis of variance and performance index can be obtained using ordinary closed loop data and least squares regression. These quantities can be used on‐line or off‐line for either the design of new controllers or as a means of assessing the performance of existing feedforward/feedback control schemes. The practicality of the results in the paper are demonstrated using simulated and industrial data.
Characteristic equations and robust stability of a simplified predictive control algorithm
Authors: Gupta Yash P.
Published: March 2009

In predictive control, control calculations are done such that the difference between the desired and the predicted response of the process is minimized. The number of points on the prediction horizon at which the error is minimized and the number of future control moves considered affect the on‐line computational effort involved in the solution of the constrained optimization problem. Earlier papers have shown that the control performance obtained using the DMC algorithm can also be obtained by using a simplified algorithm where the error is minimized at one point and one future control move is calculated. Because of its computational advantages, the simplified algorithm is analyzed further in this paper. Its transfer function is compared with the transfer function of the DMC algorithm. Characteristic equations to select tuning parameters are presented. The paper also compares the robust stability of the simplified and the DMC algorithms on SISO and MIMO process models. The results provide additional support to the viability of the simplified algorithm and thus indicate that it is possible for some processes to benefit from predictive control with only modest computational resources.
Problem‐oriented modules for process simulation. resolution strategies for simulation and optimization
Authors: Montagna Jorge Marcelo
Published: March 2009

A new resolution strategy is presented to overcome short‐comings of the sequential modular process flowsheeting. Following a logic flow of information, different from the material flow of streams in the flowsheet, changes the mathematical structure of the system of equations that models the units. New programs have been generated, very different from traditional modules.

Deciding an appropriate resolution strategy usually leads to a dramatic reduction in required CPU times and to an increased flexibility to handle different problems. The simulation convergence and process optimization can be approached from a different perspective.
Carbon monoxide reduction of sodium sulfate mixed with sodium titanate
Authors: Zou X. , Avedesian M. M. , Van heiningen A. R. P.
Published: March 2009

The solid state reduction kinetics by carbon monoxide of sodium sulfate mixed with sodium titanate are studied in a thermogravimetric system at 670‐750°C. It is found that the reduction of this mixture is much faster than that of pure sodium sulfate. The conversion‐time curves of the model mixtures are sigmoidal in shape and well described by the nucleation and growth kinetic model. The activation energy is 420 kJ/mol. The influence of the CO and CO2, concentration, mass fraction of sodium titanate and addition of sodium sulfide catalyst are investigated. Based on the present experiments and literature results, a mechanism is proposed for the CO reduction.
A study of vapour‐liquid equilibria for the binary mixtures hcfc22/cfc114, hcfc22/hcfc142b and hcfc22/hfc152a
Authors: Ström Krister H. U. , Grén Urban B.
Published: March 2009

Experimental data for vapour liquid equilibrium for the three non‐azeotropic mixtures HCFC22ICFC114 (CHClFz/CzClzF4), HCFC22IHCFC142b (CHClFz/Cz,/H3ClFz) and HCFC221HFC152a (CHClFz/CzH4Fz) and vapour pressure for the pure components have been measured in pressure range up to 1.8 MPa. In a comparative study the deviations between experimental and calculated data for three correlation methods are presented. The three methods are the equations of state according to Lee‐Kesler (1975) and Carnahan‐Starling‐de Santis (1976) and the activity coefficient model by Wilson (1964).

Interaction parameters have been fitted from experimental data to the mixing rules proposed to the two equations of state and the activity coefficient parameters have been determined in the Wilson (1964) model. All three methods studied give good conformity with experimental data for the three mixtures examined.
Separation sequencing. use of information distance
Authors: Iordache Octavian , Corriou Jean‐Pierre , Tondeur Daniel
Published: March 2009

A fast process synthesis procedure is developed for generating preliminary separation schemes. The main approach is based on similarity indices obtained from chemical, physical and operating properties between two chemical species in a separation scheme. For the whole set of species, a similarity matrix results. On this basis, algorithms for classifying chemical species and generating separation sequences are developed. A distance between flowsheets is used in order to compare different separation schemes with one another or to some reference cases. The weights of the properties and heuristics are adjusted to account for well‐known optimal cases. Changes in the number of considered separation properties and in their hierarchy are also used to improve the procedure. The algorithm requires very little calculation and can even be implemented by hand in the simplest cases. Extensions of the algorithm include the use of actual values of the separation properties instead of boolean ones and the generation of non‐sharp flowsheets.
Visualization of meso‐ and micro‐mixing status in flow system by high speed stroboscopic microscopic photography
Authors: Chen Jianfeng , Chen Bin , Chen Gantang
Published: March 2009

A new visualization technique, the High Speed Stroboscopic Microscopic Photography with spatial resolution of 6.7 m̈m and time resolution of 8 m̈S was developed and first used in this work to visualize the performance of fluid elements in the meso‐ and micro‐mixing processes. From the large amount of pictures taken by this technique, it was found that the fine structure of micro‐fluid‐elements having sizes less than λK looks mainly like slices, especially at higher turbulence in which stochastic elongation and stretching play a dominant role in the deformation of the micro‐elements. Finally, the meso‐ and micro‐mixing processes were ascribed as composed of three consecutive stages: (1) turbulent dispersion, by which the large eddies of sizes larger than λK are dispersed into ones of sizes of λK, (2) stochastic elongation and/or stretching, and (3) molecular diffusion, by which the whole system becomes homogeneous in the molecular scale.
Concentration forcing of isothermal plug‐flow reactors for autocatalytic reactions
Authors: Chidambaram M.
Published: March 2009

The performance of isothermal plug‐flow reactors under feed concentration forcing is analysed for improvement in average yield of product B for a homogeneous autocatalytic reaction, A →k1 A1 →k2 A, →k3 B, where A1 or A2 has an activity influence on the reaction rate constant k1. The performance of the periodically forced reactor with the autocatalytic reaction is compared with that of the corresponding uncatalysed reaction.
Absorption of radiation by substances at “high” concentrations: A new equation and process monitoring applications
Authors: Thatipamala R. , Hill G. A. , Rohani S.
Published: March 2009

Beer‐Lambert's law has a wide range of applications, spanning the fields of pure sciences and engineering, and is commonly used for the determination of the concentration of an optically sensitive compound, at “low” concentrations. In this report it is shown that a log‐log expression, log(T/T0) = K log(C/C0), accurately models experimental data (±3%) for four different absorbing species, at “high” concentrations. The dimensionless constant K is shown to be only a characteristic of the absorbing species, and independent of the spectrophotometer/cuvette system used. The new equation is used for on‐line monitoring of dynamic biomass concentration in a continuous bioreactor (CSTBR) for a step change in dilution rate.
Characterization and catalytic gasification of the aqueous by‐product from vacuum pyrolysis of biomass
Authors: Roy C. , Pakdel H. , Zhang H. G. , Elliott D. C.
Published: March 2009

Spruce wood residues were treated in a vacuum pyrolysis Process Development Unit with a throughput capacity of 28 kg/h. Two aqueous phase condensate samples with COD concentration varying between 190 and 255 g/L were produced and sequentially extracted with dichloromethane and ethylacetate solvents. The soluble organic matter was composed of acidic, phenolic, alcoholic and ketonic compounds. The insoluble fraction was sequentially distilled at 100 and 110°C under atmospheric pressure. Mainly water was recovered in the first distillate, while the second distillate contained 30.4% formic and acetic acids, 69.4% water and 0.2% residual organic compounds. The distillation residue was rich in oxygen and was essentially insoluble in any organic solvent. The two aqueous phase pyroligneous samples were treated in Bat‐telle's Thermochemical Environmental Energy System (TEESr̀), a registered service mark of Onsite*Ofsite, Inc. of Duarte, California, U.S.A. The results of the tests showed that similar results were obtained with either feedstock. In batch tests a COD reduction of 99% was achieved. The product gas composition was typically about 49% methane, 5% hydrogen, 1 % ethane and 45% carbon dioxide. Tests in a continuous stirred‐tank reactor produced reproducible data which can be used for process scale‐up. Catalyst lifetime was identified as needing further improvement. The preliminary results demonstrated the technical feasibility of the catalytic gasification process as a useful step in the recovery of energy from the secondary condensate stream and the cleanup of the by‐product water from vacuum pyrolysis of wood.
Acid hydrolysis of cellulose. part ii: Stochastic simulation using a monte carlo technique
Authors: Zin‐Eddine Dadach , JOSé‐Henrjque Pinto Q. , Kaliaguine Serge
Published: March 2009

A Monte Carlo procedure was developed to simulate cellulose acid hydrolysis at high temperatures. Both the kinetic information related to the model compound cellobiose and the morphological aspect of cellulose including crystalline, semi‐amorphous and amorphous zones were estimated from experimental data and introduced in a FORTRAN program. In our model of cellulose acid hydrolysis, the cleavage of a glycosidic bond and the degradation of glucose are considered as two irreversible reactions in series. For all the temperatures, the overall glucose disappearance rate constant used in our model, was higher than the experimental constant obtained from the degradation of pure glucose. The changes related to the effects of milling on the cellulose acid hydrolysis were successfully considered in the procedure. Finally, the observed good agreement between the simulated and the experimental data of glucose yield versus time proved that Monte Carlo simulation associated with a Markov chain is a flexible connection between cellobiose (model compound) and cellulose conversion reactions.
Calculation of excess molar volumes with different cubic equations of state and different mixing rules
Authors: Djordjević Bojan D. , Šerbanovlć Slobodan P. , Grozdanić Dušan K.
Published: March 2009

The effects of the simple composition‐dependent combining rules (conventional, Adachi‐Sugie and van Laar‐Stryjek‐Vera‐type) and Huron‐Vidal‐NRTL mixing rules and different cubic equations of state (Redlich‐Kwong, Soave‐Redlich‐Kwong, Peng‐Robinson and Peng‐Robinson‐Stryjek‐Vera) on excess molar volume correlation are examined. The results obtained for some asymmetric non‐ideal mixtures indicate very good agreement between correlated and experimental data in all cases when Huron‐Vidal‐NRTL mixing rules are coupled with the Peng‐Robinson‐Stryjek‐Vera equation of state.
Importance of using the correct impeller boundary conditions for CFD simulations of stirred tanks
Authors: Fokema M. D. , Kresta S. M. , Wood P. E.
Published: March 2009

Two experimentally determined sets of impeller boundary conditions were used to simulate the flow generated by a pitched blade turbine in a cylindrical baffled tank. Use of these two sets of boundary conditions in simulations with two different off bottom clearances led to the conclusion that the flow generated by a pitched blade impeller cannot be successfully predicted without considering the impeller location. Correct prediction of velocity fields in the tank required the correct specification of velocity boundary conditions. Successful prediction of the turbulent energy distribution required proper specification of the turbulence boundary conditions. There was almost no interaction between the velocity and turbulence fields. The turbulet kinetic energy dissipation rate was at a maximum close to the impeller in both geometries. Within this region the average dissipation rate was five and a half times greater that the average dissipation rate in the tank.
Changes in liquid hold‐up in foam and size of foam by perforated plates and contribution to mechanical foam‐breaking
Authors: Kuni M. , Onodera M. , Hosokaz K. , Yamagiwa K. , Ohkawa A.
Published: March 2009

Changes in the liquid hold‐up, ϵ, and the diameter of d, of a foam that are induced by perforated plates (PPs) and the contribution of PPs to foam‐breaking were studied. A foaming system containing a dilute detergent solution in a column with mechanical agitation fitted with a rotating‐disk foam‐breaker (MFRD) was used. After the foam passed through the PPs, ϵ and d decreased and increased, respectively. The use of PPs to achieve a maximum reduction in ϵ and a maximum increase in d is confirmed. It is also demonstrated that use of PPs contributes not only to improving the foam‐breaking performance of the MFRD, but also to power savings.