bluuebunny/crossref_metadata_2025 huggingface dataset:
The Adsorption of p‐nitrophenol on anion exchange resin at various temperatures
Authors: Huang Ting‐Chia , Cho Lan‐T'Ai
Published: March 2009

The isotherms of p‐nitrophenol adsorbed on the anion exchange resin Ionac AFP‐329 at temperatures in the range of 278.1 to 338.1 K are correlated with the Freundlich equation. The temperature dependences of the Freundlich constants and the effect of the amount adsorbed on the isosteric heat of adsorption are discussed. The results indicate that the relationships between k, n and temperature can be expressed as.

n = 0.00129 T

ln k = 5.12 – 0.0152 T

and

ln k = 5.05 – 11.63 n

and that the isosteric heat of adsorption varies linearly with the logarithm of amount adsorbed.
Rotary cylinders: Solid transport prediction by dimensional and rheological analysis
Authors: Perron J. , Bui R. T.
Published: March 2009

A semi‐experimental model for predicting the axial transport of the granular bed in a rotating cylinder is proposed. It is based on dimensional analysis and on the determination of an apparent viscosity characterizing the flow behaviour of the bed. Unknown constants in the model are determined either by analysis or by tuning with experimental data. An example of such tuning is shown to work well. The model is capable of giving, as a function of filling angle and friction angle, the axial velocity that varies along the cylinder axis. This is important for the control of the process taking place inside the cylinder.
Synthese du furyl‐2 oxiranne en milieu hétérogène solide‐liquide faiblement hydrate: Determination du régime de production, expression de la loi cinétique
Authors: Rakotondramanana Samuel , Borredon Elisabeth , Molinier Jacques
Published: March 2009

Afin d'étudier le transfert à plus grande échelle de la synthèse du furyl‐2 oxiranne à partir du furfural, les conditions opératoires les mieux adaptées ont été définies. Le domaine expérimental étant déterminé, l'utilisation d'une cuve agitée à alimentation et soutirage continus s'est avérée être la plus performante. Enfin, l'expression de la loi cinétique de la réaction d'époxydation a permis d'évaluer la production horaire en époxyde.
High yield production of microcrystalline cellulose by a thermo‐mechano‐solvolytic treatment
Authors: Garnier G. , Bouchard J. , Overend R. P. , Chornet E. , Vidal P. F.
Published: March 2009

By thermally treating a commercial cellulose in ethylene glycol, celluloses of controlled low degree of polymerization, DPr = 1000 to 70, can be derived. Two general behaviors are observed in the range studied. At first, the depolymerization reaction is predominant down to a DP equal to 130. Beyond this level, the depolymerization process leads to extensive solubilization of the cellulose. The treated celluloses have been analyzed by X‐ray diffraction, FTIR, TGA, elemental analysis and enzymatic hydrolysis. No chemical change of the cellulose could explain the two different behaviors. A physical modification in the form of depolymerization and destructuration is suspected.
Dynamics of adsorptive reactors I — Instantaneous nonlinear adsorption and finite zero order irreversible reaction
Authors: Loureiro José , Costa Carlos , Rodrigues Alírio
Published: March 2009

The dynamics of adsorptive reactors, in which the coupling of nonlinear Langmuir adsorption with zero order reaction A → B occurs, is considered. The method of characteristics is used to develop, analytically, the responses of fixed bed (plug flow) adsorber/reactors to step, pulse or Dirac inputs of reactant A. An increase in the breakthrough time of the column is observed as a consequence of the coupling of both phenomena.

The responses of CSTR adsorber/reactors to step or Dirac inputs of reactant A are derived, as well. A method for the determination of equilibrium and kinetic parameters is proposed.
Set‐point optimization of an adiabatic trickle‐bed reactor system
Authors: Chao Yung‐Cheng , Chang Jyh‐Shyong , Huang Hsiao‐Ping
Published: March 2009

A combined system parameter estimation and deactivation model identification procedure is proposed to create a grey model of an adiabatic residue hydrodesulfurization (RDS) trickle‐bed reactor. Using the resulting grey model, a precomputed set‐point table is used to optimize the set‐point of the RDS reactor unit. The objective function chosen is the predetermined reactor outlet sulfur content and the optimal set‐point is the reactor inlet temperature. Five crucial case studies using a dynamic simulator of an adiabatic RDS trickle‐bed reactor demonstrate the applicability of the proposed algorithm in developing optimal set‐points for a commercial process.
Porous gas distributors in bubble columns. Effect of liquid presence on distributor pressure drop. Effect of start‐up procedure on distributor performance
Authors: Prakash A. , Briens C. L.
Published: March 2009

Many bubble columns use porous gas distributors to obtain small bubbles and large mass transfer rates. The distributor pressure drop contributes greatly to the energy consumption of bubble columns. This study found that the presence of liquid increased this pressure drop by 200 to 900% at practical gas flowrates. A model was developed to predict this increase. It assumes that gas flows through a fraction only of the pores so as to minimize the distributor pressure drop.

The mass transfer performance of a porous distributor is affected by its startup procedure. The best performance was obtained by starting the gas flow before liquid was introduced into the column. A model was developed to explain these results.
Mass transfer in a trickle‐bed column packed with a mixture of hydrophobic and hydrophilic spheres
Authors: Rangwala H. A. , Otto F. D. , Wanke S. E. , Chuang K. T.
Published: March 2009

Rates of mass transfer have been measured in a trickle‐bed column packed with a mixture of hydrophobic and hydrophilic spheres. The results show that the interfacial area is a strong function of bed composition and liquid flow rates. The gas‐phase mass transfer coefficients are not affected by the nature of the bed and agree well with values predicted by the correlations available in the literature. The dynamic liquid hold‐up in a bed of hydrophilic spheres was found to be four to seven times higher than that in a bed of hydrophobic spheres.
Hydrolysis of carbonyl sulfide: Comparison to reactions of isocyanates
Authors: Ernst Wiliam R. , Chen Michael S. K. , Mitchell David L.
Published: March 2009

The hydrolysis of carbonyl suflfide (COS), catalyzed by tertiary amines, was studied in a gas‐liquid reactor at ambient conditions. Rate constants determined in a batch reactor were similar to those determined in a continuous flow reactor. A Bronsted plot of the reaction data over the amine basicity range, 0 < pKB < 14, suggested that both amine basicity and steric factors determine catalytic behavior. The reaction data suggest a mechanism analogous to one used to explain the base catalyzed reaction of isocyanates with hydroxyl compounds. The mechanism would involve complexation of COS with amine followed by hydrolysis of the complex.
Gas‐Liquid mass transfer in a three‐phase fluidized bed with floating bubble breakers
Authors: Kim Jong O. , Kim Sang D.
Published: March 2009

The effects of liquid and gas velocities, particle size and volume ratio of floating bubble breakers to solid particles (Vf/Vs) on both the volumetric mass transfer coefficient, kla, and the gas‐liquid interfacial area, a, have been determined in three‐phase fluidized beds with floating bubble breakers. Beds having a volume ratio (Vf/Vs) of about 0.15 showed a maximum increase in both kla and a of about 30% in comparison to that in the corresponding bed without floating bubble breakers. The volumetric mass transfer coefficient in three‐phase fluidized beds with or without floating bubble breakers can be estimated from the surface renewal frequency of liquid microeddies and the particle size.
In‐situ cleaning of packings in water distillation column with a surfactant
Authors: Chuang K. T. , Sutherland R. P.
Published: March 2009

A novel method for the in‐situ cleaning of fouled packing by injecting a suitable surfactant into a water distillation column has been examined. Experiments were carried out to determine the effectiveness of such a surfactant. Test data indicate that the injection of a low foaming non‐volatile surfactant, Triton CF‐32, in the feed water results in a significant improvement in the efficiency of a contaminated packing. It was found that the packing can be restored to its new conditions if the injection is maintained for a sufficient period of time. The surfactant can be easily removed from the bottoms product either by evaporation of the heavy water or carbon adsorption of the surfactant.
Preparation of hemolysate‐filled hexamethylene sebacamide microcapsules with controlled diameter
Authors: De Smet B. Poncelet , Neufeld R. J. , Poncelet D.
Published: March 2009

Hemolysate‐filled hexamethylene sebacamide microcapsules (nylon‐6, 10 membranes) were prepared by interfacial polymerization. Sheet lattice, frame lattice, turbine and marine impellers were tested to control the microcapsule mean diameter and size distribution parameters. Mean diameters ranging from 40 to 200 μm were obtained depending on the impeller type, rotational speed and emulsifier concentration. The size dispersion of microcapsule preparations was best controlled with a frame lattice impeller, achieving standard deviation values less than 40% of the mean diameter. The wire diameter and mesh dimensions of the impeller lattice had little effect on the distribution parameters.
Reaction of thiophene on CoMo/A12O3 catalysts of various loading at low hydrogen excess
Authors: Manninger I. , Paál Z. , Henze K. P. , De Joung G.
Published: March 2009

Co‐Mo/Al203 catalysts of various CoMo loadings were examined in the hydrodesulfurization (HDS) reaction of thiophene and tetrahydrothiophene at near stochiometric hydrogen: thiophene ratio. Good compensation plots were found for both reagents and all catalysts. Reversibly bound H2S blocks active sites of HDS. The most important reaction pathway leads to but‐1‐ene; more Co gives more but‐2‐ene. The hydrogenation of buta‐1, 3‐diene is about 100 times more rapid than that of but‐1‐ene. The activity of two neighboring sites with twofold coordinative unsaturation is suggested in buta‐1, 3‐diene hydrogenation. The possible effect of Al203 support on active sites is discussed.
Slurry filtrability of potash alum
Authors: Jones A. G. , Mydlarz J.
Published: March 2009

Crystal slurries produced both by cooling and by precipitation with acetone from aqueous solution in a continuous MSMPR crystallizer reported earlier (Jones and Mydlarz, 1990) are analysed in terms of the effect of their crystal size distribution and shape on filtrability characteristics.

Crystals produced by precipitation are much smaller but more highly agglomerated than those from cooling crystallization and give rise to lower filter bed permeabilities, a performance which is slightly improved by precipitant dilution. The overall particle size is, however, similar in both modes and is relatively insensitive to crystallizer operating conditions. The filtrability data for the precipitated crystals are compared with predictions of the Carman‐Kozeny equation, assuming an idealized crystal shape. Relatively large scatter is observed, with the Kozeny coefficient, K, being in the range 2 to 8.
Catalytic upgrading of liquid hydrocarbons derived from coprocessing of heavy oil and coal
Authors: George Zacheria Mathew
Published: March 2009

Coprocessing of heavy oil and coal under elevated temperature, hydrogen pressure and low space velocity resulted in a product slurry from which the fraction distilling below 430° C was catalytically upgraded over a commercial NiMo/Al2O3 catalyst in a flow reactor. At 400° C, 13.3 MPa (H2) and LHSV of 1.0 h−1 over 90% of sulfur and nitrogen could be removed, aromaticity reduced to 16% from 26% and the API gravity increased to 36.9 from 23.8. Hydrogen consumption under these conditions was considerably lower than that obtained for upgrading the oil sands coker gas oil. Activation energies for hydrodesulfurization and hydrodenitrogenation reactions were determined to be 59.5 and 120.4 kJ/mol, respectively.
Modelling of equilibrium solubility of CO2 and H2S in aqueous diglycolamine (DGA) solutions
Authors: Hu W. , Chakma A.
Published: March 2009

Information on acid gas solubility in solvents utilized is needed for the design of gas plants. A mathematical model for the prediction of equilibrium solubility of CO2 and H2S in aqueous 2‐amino‐2‐(ethoxy)ethanol (DGA) solutions is presented. The equilibrium constants, K1 and K2, representing a simple proton transfer reaction and the carbamate formation reaction, respectively, were found to be functions of temperature and free acid gas concentration. In addition, K2, was affected by DGA concentration as well. Model predictions agree favourably with experimental data.
An impinging–Streams reactor with two pairs of tangential air feeds
Authors: Bar Tami , Tamir Abraham
Published: March 2009

The original two–impinging steams devices have proved useful for processes in gas–solid Systems. A modified form of the original two–impinging–streams reactor, with two additional air streams, was explored. All four air streams are fed tangentially to the reactor. The Performance characteristics included the determination of the pressure drop on the reactor, limits of the gas and solid particle mass flow rate, the mean residence time of the particles, and the drying heat transfer, as a function of air flow rates of the secondary and major air streams.

The behaviour of the particles and their residence time distribution was investigated by applying a stochastic Markov chain model.

It was found that the secondary air stream increases the pressure drop on the reactor and the mean residence time of the particles along with their recycling in the reactor. On the other hand, the secondary air stream decreases the critical mass flow rate of the particles, delays their exit from the reactor and reduces the heat transfer coefficient in drying wet particles.
Drop size distribution in a graesser contactor
Authors: Al‐;Hemiri A. A. , Kareem A.
Published: March 2009

An investigation was conducted of drop size distribution in a Graesser contactor, employing five liquid – liquid systems, viz., kerosene/water, benzene/water, xylene/water, hexane/water and n–butyl acetate/water. A 100 mm (4 inch) diameter Graesser contactor was used for this purpose

It was found that the drop size distribution in a Graesser contactor obeys the upper – limit distribution expressed as:

where

A correlation was developed relating the Sauter mean diameter (d32) to other effective groups
A correlation for predicting diffusion coefficients in alkanes
Authors: Erkey C. , Rodden J. B. , Akgerman A.
Published: March 2009

A correlation was developed for predicting limiting mutual diffusion coefficients of gaseous and liquid solutes in normal alkane solvents with carbon numbers ranging from 7 to 28 at temperatures to 570 K. The functional form of the correlation is based on the rough hard sphere theory. The parameters needed in the correlation are the molecular weights and hard sphere diameters of the solute and solvent molecules and molar volume of the solvent. The data used in the development of the correlation included 143 measurements with solute/solvent molecular mass ratios ranging from 0.005 to 2.26 and size ratios ranging from 0.3 to 1.3. The average absolute error in predictions was only 6.3%. When the correlation was used to predict literature values for binary n‐alkane systems, the average absolute error was 16.7%.
New measures for robustness in linear multivariable feedback systems
Authors: Alatiqi Imad M.
Published: March 2009

New measures for robustness are proposed for linear multivariable control systems. A new theorem is presented to account for the controllability of systems that contain an integrating element, in the presence of additive uncertainties. The theorem leads to the definition of a sufficient condition for robust integral controllability: robustness margin (RM). The ratio of robustness margins for competing control or processs structures can be used to discriminate between these structures. These measures are useful, especially in design stages, since their calculation depends only on steady state information. Applications to several published distillation systems show the merits of these robustness measures.
Performance of a tubular elastic sparger
Authors: Weber M. E. , Loiselle E. , Charrier J.‐M.
Published: March 2009

Elastic spargers were made from natural latex rubber tubes by repeatedly piercing the tube wall with a lance‐shaped needle to make multiple, axially‐aligned, slit‐like punctures. Gas holdups, volumetric mass transfer coefficients and pressure drops were measured at several gas flowrates for single elastic spargers oriented vertically in a column of liquid, and compared with the corresponding measurements for a rigid sparger.
Flow transition for natural convective heat transfer in a porous medium saturated with water near 4°C
Authors: Islam M. R. , Chakma A. , Nandakumar K.
Published: March 2009

In this paper, the problem of buoyancy‐induced convection flow in water‐saturated porous media near 4°C is examined using a numerical model. Darcy's law is used to model flow behavior and a single equation convective heat transfer model is used for the energy equation. As the Boussinesq approximation is not valid for this case, a parabolic dependence of density on the temperature is used. Natural convection is generated and sustained by a uniform heat source. Flow behavior is governed by three natural parameters appearing in the model. They are: (i) dynamical parameter,

(ii) geometric parameter, γ = b/a; and (iii) wall temperature,

in relation to the reference temperature at the density extremum.

For certain ranges of θw (<0) and Gr, interesting density inversion effects are possible. Transient solutions are obtained for various aspect ratios and modified Grashof number values. For a wide range of Grashof number, steady state solutions could not be obtained. Flow mutations into periodic and chaotic solutions are investigated for a range of Grashof number (100 to 40,000) and aspect ratio values (1 to 10).
A simple model for a non‐isothermal adsorption column
Authors: Ruthven Douglas M. , Rojo J. Carlos
Published: March 2009

A simple analytic solution has been derived for the temperature response of a non‐isothermal adsorption column in which a small concentration of an irreversibly adsorbed species is removed. The model is shown to provide a reasonable representation of the experimentally observed behaviour of an ethanol drying column using 3A molecular sieve as the moisture selective adsorbent.
Gasification kinetics of oil sands coke
Authors: Nguyen Q. T. , Watkinson A. P.
Published: March 2009

Kinetics of steam gasification of delayed and fluid cokes derived from Athabasca bitumen have been studied in 6.35 cm diameter stirred and fixed bed reactors. Experiments were carried out at atmospheric pressure and at temperatures between 800°C and 930°C. The coke particle size ranged from 0.1 to 3.5 mm, and the steam partial pressure was varied from 15.2 to 60.6 kPa. Scanning electron microscopy, surface area analysis, and mercury porosimetry were employed to relate physical structure changes in the solids to experimental kinetic data. Several kinetic models for gasification were tested with the experimental gasification data. Rate expressions are presented for carbon conversion and for the release of sulphur.
Dynamic behavior of mixer‐settlers
Authors: Salem Abu Bakr , Sheirah Mohamad A.
Published: March 2009

A mathematical model has been developed to simulate and predict the dynamic behavior of liquid extraction counter current operations in mixer‐settler units. Murphree efficiency has been included in the model. The behavior of a multistage glass mixer‐settler has been studied under start‐up transient conditions. Very good agreement between the simulation results and the experimental findings have been obtained. The simulation results showed that this model can efficiently be used to determine the optimum number of stages, the capacity of each stage, the phase ratio and the time required for each unit to attain steady state conditions. Other controlling parameters in operating such units are investigated.
The mixing cells model applied to a fixed bed dryer
Authors: Costa Vitor A. F. , Figueiredo A. Rui A.
Published: March 2009

The system of Partial Differential Equations for the simultaneous heat and mass transfer in drying of a fixed bed is highly non‐linear, and the numerical resolution requires much computing time when a conventional finite‐difference scheme is employed. An Ordinary Differential Equations system with the same physical significance and of a stiff nature is obtained by the mixing cells model. The criterion for prescribing the number of cells is outlined and the computed temperature distributions are compared with those available from the literature. The method also enables simulation of the condensation of drying air over the product but, under such conditions, the computing time is greatly increased.
Solving dynamic equations for the collection and evaporation of an aerosol
Authors: Viljoen H. J. , Eyre D. , Wright C. J.
Published: March 2009

We investigate the coalescence of drops undergoing random Brownian motion and evaporation. The evolution of the drop size spectrum is determined by solving a partial integro‐differential equation with a kernel that describes the pairwise coalescence of drops. Numerical results for fuel injection with n‐octane suggest that the size distribution of drops is determined by two competing processes, namely coalescence and evaporation.
Forced oscillations of concentration in transport reactors
Authors: Prashant C. , Chidambaram M.
Published: March 2009

The performance of a transport catalytic reactor is analysed for an adsorption/desorption type model with Eley‐Rideal surface kinetics with square wave oscillations in the feed concentration. The inlet average concentration of both the reactants over a period is assumed to be constant. Significant improvement in the yield of product is obtained by increasing the feed concentration of both the reactants in the first fraction of a period. The effect of adsorption capacity of the catalyst, reaction rate constants, and inlet feed mean concentration of the reactants are evaluated. The deactivation of active sites, due to product inhibition, introduces resonance in the yield versus cycle split. The yield of product shows a minimum with respect to cycle split for the type of forcing where one of the reactant concentrations increases and the second reactant concentration decreases in the first fraction of a period.
Traitement et valorisation des eaux usées agro‐alimentaires: Faisabilité du procédé aérobie thermophile pour un effluent d'abattoir
Authors: Couillard D. , Gariépy S.
Published: March 2009

La présente étude s'inscrit à I'inékrieur de travaux de développement d'un procédé de traitement des eaux usées permettant aussi la récuperation des éléments nutritifs contenus dans les effluents de I'industrie agro‐alimentaire. Un effluent d'abattoir a été soumis à une série d'essais à I'échelle du laboratoire a des températures de 45, 52 et 58°C. L'efficacité du procédé sur le plan traitement a été démontrée par l'enlèvement de plus de 90% de la demande chimique en oxyéne (DCO)pour tous les temps de séjour étudiés (6, 12, 18, 24 et 30 heures)à 21 45 et 52°C. Le contenu en protéines brutes de la biomasse recueillie atteignait en moyenne prés de 70% sur une base sèhe, et la composition en acidés aminks de la protéine s'est révélee adéquate pour introduction à titre de concentré dans les rations alimentaires du porc et de la volaille.
The development of a deep knowledge diagnostic expert system using fault tree analysis information
Authors: Adamson M. S. , Roberge P. R.
Published: March 2009

In this paper a diagnostic Knowledge Based Expert System (KBES) prototype for a nuclear Auxiliary Boiler Feed System (ABFS) was developed. A commercial Expert System shell accesses heuristic production rules to quickly resolve the majority of common faults. Supplementing this are a series of C functions which access the Fault Tree data base previously developed during the licensing process. These functions perform diagnostics, give detailed explanations of failure mechanisms, and identify system failure risks through examination of cut sets. The capture of both heuristic and Fault Tree information has resulted in a more exhaustive diagnostic tool with a domain of application unrestricted by the limitations of previous operator experience.
Multi‐input adaptive‐predictive control of kamyr digester chip level
Authors: Allison B. J. , Dumont G. A. , Novak L. H.
Published: March 2009

This paper investigates the development and industrial application of a multi‐input/single‐output adaptive‐predictive Kamyr digester chip level controller based on Generalized Predictive Control (GPC). The controller simultaneously manipulates the blow flow and the chip meter to control the chip level. The chip meter is manipulated in a way which tends to maintain the desired production rate, while still leaving some room for control. The idea was to use the chip meter as a second input variable to reduce blow flow manipulation and, thereby, reduce disruptions to the chip column movement. The two‐input strategy decreased blow flow manipulation by more than 50% (compared to an otherwise equivalent one‐input scheme) without sacrificing output performance. However, the anticipated improvements in permanganate‐number variability were not achieved. The multi‐input strategy was discontinued after six months of operation.
Effect of the choice of final time in optimal control of nonlinear systems
Authors: Luus Rein
Published: March 2009

The choice of the final time, tj, in the optimal control of nonlinear systems is shown to be very important. By choosing tf to be small, and repeatedly optimizing the system operation over the short time intervals gives a highly oscillatory type of control for a particular nonlinear chemical reactor. The cumulative profit as compared to that obtained by choosing tf to be large, is substantially lower. In the operation of a batch reactor it is shown that if tf is small, bang‐bang control with singular sub‐arcs results. When tf is large, the optimal control policy tends to be relatively smooth and the profitability is substantially improved.
The effect of dehydration conditions on the adsorption and diffusion of propane and nitrogen in linde 5A zeolite
Authors: Tezel H. O. , Ruthven D. M.
Published: March 2009

Diffusion of propane and nitrogen in small crystals (3.6 μm) of zeolite 5A has been studied by conventional uptake rate measurements. The zeolite crystals were subjected to various pre‐treatments prior to propane and nitrogen adsorption. It is concluded that surface degradation due to pre‐treatment is not believed to occur to a significant extent since it has been observed that after a proper regeneration of the adsorbent, the diffusional properties of the system have been restored. It is suggested that the Ca++ cations which may initially obstruct the windows of the sieve become increasingly mobile with increasing sorbate concentration and move to sites within the cage. The results are broadly consistent with the study on the diffusional transition in zeolite NaX (Tezel et al., 1983).
The effect of specific growth rate and death rate on monoclonal antibody production in hybridoma chemostat cultures
Authors: Linardos Theodor I. , Kalogerakis Nicolas , Behie Leo A. , Lamontagne Louis R.
Published: March 2009

Experimental data collected from bench‐scale chemostat cultures of mouse‐mouse hybridoma cells have been used for the development of a kinetic model of monoclonal antibody production. The specific antibody productivity was found to be proportional to the specific death rate, indicating a stimulating effect of stress on the ability of the cells to produce antibody. The death rate was found to be an exponential function of the average cell age in the culture. Furthermore, a Generalized Maintenance Energy (GME) model is proposed, to take account of the effects of culture stress on the nutrient uptake rates. The proposed relationships agreed very well with other mouse‐mouse hybridoma chemostat culture data in the literature.
Approximate analytical solutions for a biofilm reactor model with Monod kinetics and product inhibition
Authors: Bhaskar G. V. , Bhamidimarri S. M. Rao
Published: March 2009

This paper presents a method for obtaining approximate analytical solutions based on a Taylor series linearization technique for a biofilm reactor with Monod kinetics and product inhibition. Of the two inhibition types investigated, the linear inhibition solution was in explicit form, while the exponential inhibition solution was in series form. The results of the approximate solution agree well with the numerically exact solution.
Enzyme mass transfer coefficient in aqueous two phase system using a packed extraction column
Authors: Patil T. A. , Jafarabad K. Rostami , Sawant S. B. , Joshi J. B.
Published: March 2009

Fractional dispersed phase hold‐up and dispersed side mass transfer coefficients for amyloglucosidase were measured in a 56 mm i.d. packed extraction column using a sodium sulphate‐polyethylene glycol 4000 system. Raschig rings (3 to 13.3 mm), Berl saddles (12 mm), Pall rings (12.6 mm), glass spheres (5.2 mm) and structured wire gauze were used as packings. The effect of packing size was investigated in the case of ceramic Raschig rings. The effect of phase composition of the aqueous phase system also was studied.

Correlations have been developed for fractional dispersed phase hold‐up and volumetric mass transfer coefficient with packing voidage, dry surface area of packings, superficial dispersed phase velocity and the liquid phase physical properties.
Kinetic model of parallel self‐poisoning in the catalytic hydrogenolysis of ethane on single‐type surface sites
Authors: Szamosi Janos , Kristyan Sandor
Published: March 2009

A kinetic model for parallel competitive self‐poisoning in the catalytic hydrogenolysis of ethane has been developed. It is assumed that molecular hydrogen is the bond‐splitting agent in the rate‐determining step, and self‐poisoning itself is reversible. In addition, all active surface sites are taken to be of the same kind. The model provides a satisfactory account of the experimentally observed kinetic behavior.
Procéadéa de solubilisation biologique des méataux dans les boues anaéarobies d'éapuration: Filtrabilitéa, neutralisation et teneurs en n et p des boues traitéaes
Authors: Couillard D. , Mercier G.
Published: March 2009

La solubilisation biologique des métaux lourds contenus dans des boues anaérobies d'épuration a été effectuée dans un réacteur en continu á deux temps de séjour (0.5, 0.75 jour). Suite á la filtration des boues traitées, les pourcentages du Cu et du Zn solubilisés sont passés de 92% et 94% á 78% et 77% dans la boue filtrée. Le fer reprécipite en grande partie dans les boues filtrées. Les boues traitées sont faciles á déshydrater. l'indice de filtrabilité (r0.5) des boues traitées est 38 fois inférieur a celui des boues anaérobies, sans ajout de polymère. Les r0.5 obtenus, inférieurs á 8 × 1012 m/kg, permettent la déshydratation des boues sans ajout de polymère par un filtre‐presse á plateaux. La centrifugation est aussi envisageable. l'azote total, le phosphore total ainsi que le phosphore hydrolysable restent inchangés tout au long du traitement. l'ammoniac est perdu á 47% dans le filtrat. La neutralisation des boues traitées (pH = 7) et du surnageant contaminé (pH = 10) requiert une faible quantité de base. La précipitation sélective de métaux devrait permettre une recuperation du Cu contenu dans les boues métalliques générées. Enfin, les résultats obtenus indiquent la préfaisabilité du procédé et une étude á l'echelle pilote devrait permettre la mise á l'échelle réelle du procédé.
Improving prediction of salt effect on vle of isopropyl alcohol‐h2o‐salt and methanol‐h2o‐salt systems with preferential association
Authors: Lee Liang‐Sun , Tsao Yung‐Zin , Yang Barry L. M.
Published: March 2009

When a salt is added to an azeotropic mixture, the azeotropic composition tends to shift or even disappear, due to salt‐in and salt‐out effects. Models from the literature are applied to calculate the vapor‐liquid equilibrium of systems of isopropyl alcohol H2O‐salt, and methanol H2O‐salt. Schmitt and Vogelpohl's model (1982) gives the best results. With the concept of preferential association, an improvement can be accomplished through the modified distribution factor of the salt associating with components of the mixture for the systems mentioned above.

Owing to the lack of solubility data of the salt in the individual components of the azeotropic mixture, the generality of this modification has not yet been demonstrated.
Étude d'un procédé de pyrolyse rapide du charbon dans un réacteur cyclone
Authors: Houzelot J. L. , Hilaire P. , Lebrun‐Cabon A. , Villermaux J. , Bertav R. , Isler D.
Published: March 2009

Experimental results on fast pyrolysis of coal in a steady state pilot reactor at a flowrate of 0.1 kg/h are examined in this article. The pyrolysis reactor is a cyclone. Using such a system it was possible to achieve simultaneously the reaction and the separation of semi‐cokes from volatiles produced by pyrolysis. A pump enabled gas recycling on the experimental setup and allowed a good hydrodynamic regime in the reactor. Only gases were recycled, liquids and tars being condensed and recovered.

Experiments were carried out on a Lorraine coal (Houve well). From 100 grams of coal, 60 grams of semi‐coke, 35 grams of liquids, and 5 grams of gas containing 66% hydrogen and 30% methane were obtained. For the interpretation of results, an experimental kinetics study on coal grain pyrolysis is presented for grains in the range of 2.5 to 20 mm and temperatures between 700 C and 1050 C.
Accelerated successive substitution schemes for bubble‐point and dew‐point calculations
Authors: Peng Ding‐Yu
Published: March 2009

The accelerated successive substitution (SS) algorithms developed by Mehra et al. for flash calculations have been extended to the prediction of saturation points. A transformation matrix which is used to calculate the acceleration parameter has been rewritten in a form that is applicable at the saturation conditions. Simple equations for estimating the initial values and recursive formulae according to which the iterates can be updated are presented. The proposed schemes were compared with the conventional SS method and a multivariate Newton's method. The comparison suggests that the accelerated SS schemes are more tolerant of poor initial values and sometimes more efficient than Newton's method.
Elucidation of mean voidage in packed beds
Authors: Foumeny E. A. , Moallemi H. A. , Mcgreavy C. , Castro J. A. A.
Published: March 2009

Mean voidage is a global structural property of packed beds and its accurate prediction is therefore of great significance in any plug‐flow type model. A general correlation has been developed which enables this parameter to be evaluated. The work reported here deals with mono‐size non‐porous spherical packing, but also tackles related issues such as size distribution and the way in which they influence the mean voidage. In addition, an attempt has been made to discuss the merits of alternative packing arrangements.
Phase equilibrium in the system water‐hydrogen sulphide: Hydrate‐forming conditions
Authors: Carroll John J. , Mather Alan E.
Published: March 2009

Recently revealed problems with the fluid phase equilibria data for the system H2S‐H2O as presented by Selleck et al. (1952) prompted this review of the hydrate‐forming conditions. The smoothed tables of Selleck et al. (1952) along the three‐phase loci are replaced with equations which are based on a critical review of all of the experimental data.
Deposition velocity correlation for water slurries
Authors: Gillies R. G. , Shook C. A.
Published: March 2009

a Correlation to predict the deposition velocity of aqueous slurries is presented. The correlation employs the viscosity and density of the mixture of fluid and (‐74 μm) particles, as well as the mass median diameter (d50) of the fraction coarser than 74 μm. The correlation is derived from isothermal flow experiments using pipelines of diameter between 0.053 and 0.495 m.
Drying in capillary‐porous cylindrical media
Authors: Robbins M. C. , Özişlik M. N.
Published: March 2009

Analytical solutions are presented for temperature and moisture distributions in a cylindrical capillary‐porous body using Luikov's model and employing a solution technique based on the decoupling of the simultaneous heat and mass diffusion problems. The relative importance of the dimensionless parameters governing drying is presented and a comparison of temperature and moisture profiles for the cylinder and the slab is given.
Marangoni and buoyant convection in a cylindrical cell under normal gravity
Authors: Szymczyk J. A.
Published: March 2009

The present paper deals with the investigation of thermocapillary and natural convection by applying a white light‐sheet technique for the simultaneous determination of the velocity and the temperature field. The oscillatory Marangoni convection has been visualized with differential interferometry. Streamlines, velocity profiles and isotherms are presented and discussed. A complete separation of a surface tension driven convection roll of hot fluid in the boundary layer and a buoyancy driven convection roll of colder fluid in the liquid volume was discovered. For large driving forces (large Marangoni number) inertia becomes effective and the interface becomes the source of localized eruptions.
Solvent extraction — the challenges of a “mature” technology
Authors: Baird M. H. I.
Published: March 2009

The solvent extraction area is perceived by some chemical engineers as being mature and fully developed. The present review shows that this is not the case. Many chemical engineering problems must be solved before equipment can be confidently designed from first principles. The review also outlines progress in extraction process chemistry, and in new techniques such as membrane extraction.
An improved correlation for turbulent drag reduction in dilute polymersolutions
Authors: Darby Ron , Pivsa‐Art Suchat
Published: March 2009

The model for turbulent drag reduction in dilute polymer solutions developed by Darby and Chang (1984), and modified by Darby et al. (1989) has been further refined to significantly improve its ability to represent data for a variety of polymer solutions over a wide range of conditions. It is also shown how the rheological parameters in the model can be obtained from two or three data points for turbulent flow, in lieu of laminar viscometric measurements. This technique is applied to a wide variety of turbulent drag reduction data taken from the literature to demonstrate the general applicability of the model. The model is also shown to be consistent with Virk's maximum drag reduction asymptote (Virk, 1975) in the high Reynolds number limit.
Effects of stagnant and dispersion conductivities on non‐darcian forced convection in square Packed‐Sphere channels
Authors: Chou F. C. , Chung P. Y. , Cheng C. J.
Published: March 2009

This paper presents a numerical and experimental investigation of the effects of stagnant and dispersion conductivities on non‐Darcian forced convection in square packed‐sphere channels. The theoretical prediction of Nusselt number are found to be in good agreement with the experimental data. A larger near‐wall damping of stagnant conductivity is found for the present water‐steel medium than for that described by the mixing rule based on the volume fraction. A nonlinear Peclet number dependence, Peλ and λ = 0,88, for dispersion conductivity is found to induce better agreement between the theoretical and experimental results especially for the cases of high Peclet number and high Dc/d.
A study of the dynamics of anodic copper dissolution in a NaCl/KSCN electrolyte
Authors: Gu Z. H. , Fahidy T. Z.
Published: March 2009

The oscillatory behaviour of the anodic dissolution of copper into an aqueous NaCl solution containing a small amount of thiocyanate ions has been studied experimentally in the absence and in the presence of a magnetic field. The latter has an inhibiting effect on the oscillation and, under specific conditions, it can fully suppress it.
Absorption kinetics of ozone in aqueous O‐cresol solutions
Authors: Beltran F. J. , Encinar J. M. , Garcia‐Araya J. F.
Published: March 2009

The kinetics of ortho‐cresol ozonation in water has been studied using the film theory. At most experimental conditions investigated, the kinetic regime of the absorption has been fast pseudo first order with respect to ozone. At 30°C mass transfer plays an important role in controlling the absorption rate of ozone. The selfdecomposition reaction of ozone does not take place because of the great reactivity of o‐cresol with ozone. Reaction rate constants have been determined at pH 7 for different temperatures below 30°C. The following Arrhenius equation was obtained:

kT = 2.2 × 1023 exp(‐11784/T), L/mol ṁ s

At temperatures below 30°C there exists an ozone partial pressure value above which the ozone absorption kinetic regime changes to fast second order regardless of experimental conditions.
Surface tensions and contact angles due to lignin sulphonates in the system: Liquid sulphur, aqueous zinc sulphate and zinc sulphide
Authors: Owusu George , Peters Ernest , Dreisinger David B.
Published: March 2009

Surface tension and contact angle measurements were made in the liquid sulphur‐aqueous zinc sulphate‐zinc sulphide system at superatmospheric pressures, and showed that, in the absence of surfactants, the liquid sulphur‐aqueous solution interfacial tension was 54.0 ± 1.0 mN/m, falling to 27.0‐30.0 mN/m when 0.3 g/L or more of lignin sulphonate was added to the solution. At the same time, the contact angle between liquid sulphur and the same solution increased from 80 ± 5° to 148 ± 5°. As a result, the work of adhesion between liquid sulphur and zinc sulphide falls from 63.7 mJ/m2 to about 5.3 mJ/m2. The results indicate that adsorption of lignin sulphonate occurs on both the mineral‐aqueous and the sulphur‐aqueous interfaces.
Rotary cylinders: Transverse bed motion prediction by rheological analysis
Authors: Perron J. , Bui R. T.
Published: March 2009

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

This paper focuses on two‐phase (e.g., fluid‐solid catalyst) chemical reactors where one phase participates in the feed and effluent, first order chemical reactions proceed in the other phase and linear, species‐dependent, interphase transport connects the phases. A class of reactors exists in which the Laplace transform of the dynamic reaction/interphase transport equations reduces to essentially that of an effective set of first order reactions amongst effluent phase species only, in an imaginary single phase reactor.

This result bears on scale‐up: Since the imaginary reactor simply scales with the usual residence time distribution, so too do reactors of this class scale with its analog. This easily measurable analog turns out to be just the non‐adsorbing tracer experiment. Significantly, certain reactors outside of this class do not scale likewise, even with first order chemistry; an example illustrates.

The class in question includes, but is not limited to, fixed bed and Berty (CSTR) reactors. The analysis allows design inferences for two‐phase reactors, including fluidized beds.
Sodium silicate as a coke inhibitor during naphtha pyrolysis
Authors: Ghosh Kalyan K. , Kunzru Deepak
Published: March 2009

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

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

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

In a liquid‐solid spouted bed system containing coarse and fine particles, the entrainment and elutriation of the separated fines were investigated with reference to variations in the pressure drop through the bed. The effect of operating parameters on the velocity corresponding to the beginning of entrainment of fines (Ube) was examined and a dimensionless correlation was proposed.

The effect of operating parameters on the elutriation rate coefficient of fines at liquid velocities larger than their terminal settling velocity (Ul) also was studied. An empirical equation was proposed for a column height above TDH, the height of freeboard at which the elutriation rate becomes constant. It was recognized that the elutriation phenomenon was closely related to the length of the stratified particle transport bed when the ascending velocity of the elutriable particles at the top of bed becomes constant.