bluuebunny/crossref_metadata_2025 huggingface dataset:
Deuterium exchange between hydrogen and water in a trickle bed reactor
Authors: Enright J. T. , Chuang T. T.
Published: March 2009

The catalyzed exchange of deuterium between hydrogen and liquid water has been studied as the basis for a heavy water production process. Platinum catalyst which had been waterproofed with Teflon was tested in a 0.2 m diameter trickle bed reactor at pressures and temperatures up to 6 MPa and 440 K. Extensive experimental data were used to test a model of the system which was developed from fundamental principles. It was found that mass transfer plays a very important role in the overall exchange and the conventional theory of vapour/liquid mass transfer does not adequately describe the absorption process. Modelling of the data has resulted in the postulation of a second method of mass transfer whereby HDO transfers directly from the catalyst to the bulk liquid phase.
Phase equilibria calculations with a modified redlich‐kwong equation of state
Authors: Medani M. S. , Hasan M. A.
Published: March 2009

A modified Redlich‐Kwong equation of state for pure substances in the liquid‐vapour coexisting phase region is suggested in which the fugacity coefficients of the two phases are equated and the resulting relationship is solved by assuming ωb to be temperature dependent while ωa remains constant. A generalised correlation for ωb is found with the acentric factor as a parameter. This approach is compared with the other two possible modifications, i.e. when ωa is a funtion of temperature while ωb is constant, and when both ωa and ωb are temperature dependent. Comparison revealed the excellent attainment of the equilibrium conditions when the proposed method is applied. Predicted volumetric properties and isothermal enthalpy departures of the liquid and vapour as well as the saturation vapour pressures are also compared which reveal the adequacy of the new modification.

With the application of the mixing rules, the proposed modified equation is successfully applied to VLE calculations for binary mixtures of different complexities.
Behaviour of shallow fluidized beds around immersed objects
Authors: Roche G. , Chavarie C.
Published: March 2009

Impermeable and permeable objects were immersed in a shallow gas fluidized bed. The pressure distribution on the surface of impermeable cylinders closely follows the principles of classical hydrostatics. The bottom half of larger bodies is nevertheless influenced by the presence of the bottom of the bed; the top half of completely immersed objects is covered by a defluidized zone which prevents reliable surface pressure measurments with the probes devised in this work. A defluidized zone is also readily formed around the surface of partially immersed porous objects. Experimental isobars measured in the bed around these objects were compared to the predictions of a model relying on a uniform potential flow approach. The agreement between the model and the data is generally good but the flow resistance definitely seems to be larger in the defluidized envelope. The defluidized zone seems to be considerably eroded by the brushing of gas bubbles.
Solids separation in a counter‐current fluidized cascade: Jetsam‐rich mixtures at total reflux
Authors: Muzyka D. , Beeckmans J. M. , Jeffs A.
Published: March 2009

The separation of cocoanut charcoal particles (mean size 342 μm) from salt particles (mean size 459 μm) was studied in a counter‐current gas fluidized cascade at total reflux, for a number of bed depths and paddle depths. In each case the experimental separation ratio RE was found to pass through a maximum when plotted against paddle velocity. The fluidized cascade was simulated by a mathematical model, which correctly predicted the general behaviour of the system under the various conditions studied.
Spouted bed collection of solid aerosols in the presence of electrical effects
Authors: Balasubramanian M. , Meisen A. , Mathur K. B.
Published: March 2009

A spouted bed of 1.7 mm cement clinker particles was previously found to be an efficient collector of liquid micronsize aerosols introduced into the bed with the spouting gas(1) With solid aerosols, however, collection efficiencies obtained were poor since these failed to adhere permanently to the target particles and were re‐entrained.

The present paper describes experimental work to overcome the re‐entrainment problem by making use of electrostatic forces. Solid latex aerosol particles (0.79 μm dia.) were electrified by a negative corona discharge and collected in a 15 cm diameter spouted bed of ABS plastic particles (2.5 mm cubes). The variables studied included corona voltage (0 to 9500 V), bed depth (0.3 to 0.5 m) and superficial gas velocity (0.23 to 0.85 m/s).

Spouted bed efficiencies with neutral aerosols ranged from 43 to 65% as against 72‐98% with charged aerosols The experimental results are interpreted using the two‐region model of a spouted bed, and invoking an enhancement factor for aerosol mass transfer due to electrical effects. The values of this factor ranged between 160 to 2300 under the conditions studied.
Solvent extraction of copper in a reciprocating plate column
Authors: Sharma R. N. , Baird M. H. I.
Published: March 2009

Equilibrium data for the distribution of copper between an aqueous solution and a 20% solution of di‐(2 ethyl hexyl) phosphoric acid in kerosene has been obtained by shake‐flask experiments. The capacity of the organic phase for copper is greatly improved when the ammonium salt of D2EHPA is used. The performance of a 5 cm diameter Karr reciprocating plate extraction column for continuous counter‐current extraction of copper by ammoniated D2EHPA has been measured. The results, expressed as heights of a transfer unit, have been compared with data for a non‐metallic system (kerosene/acetic acid/water) in the same column. The lowest H.T.U. values measured were 43 cm for copper transfer and 23 cm for acetic acid transfer, with the difference being attributed mainly to the lower molecular diffusivity in the copper/D2EHPA system.
Simulation of cyclic dynamics in isothermal gas‐solid reaction systems effects of the frequency of sinusoidal perturbation in the bulk gas concentration
Authors: Fan L. T. , Fan Liang‐Shih , Miyanami Kei
Published: March 2009

The dynamic responses of a gas‐solid reaction system to a sinusoidal perturbation in the bulk gas concentration are analyzed. Effects of the frequency variations on the gas and solid concentration profiles and the solid conversion are comprehensively examined based on the volume reaction model under the isothermal condition. The results show that the solid conversion can be accelerated as much as 50% and retarded as much as 50% depending on the frequency and the amplitude of the perturbation. The relationships between the reactant concentrations at the surface and the center are elucidated by means of phase‐plane plots.
Substrate‐inhibited microbiological regeneration of granular activated carbon
Authors: Sigurdson S. Paul , Robinson Campbell W.
Published: March 2009

A kinetic model of the microbiological regeneration of activated carbon is presented for the case where the adsorbate is inhibitory to the microbial‐growth‐associated bio‐oxidation process. The model is used to predict the regeneration time for specified combinations of microbial species (using growth kinetic constants determined in a carbon‐free system) and carbon type (adsorption isotherm). In addition to the foregoing parameters, computer simulations show that the spent carbon adsorbate loading, the carbon mass‐to‐fermentation broth volume ratio and the inoculum size also have a significant effect on the time required for batch in situ regeneration of a carbon column.

Experimental results are given for a granular carbon‐phenol‐bacteria (P. putida) system at several operating conditions; the observed regeneration times are in good agreement with predicted values. Once‐regenerated carbon retained 47 percent of the phenol equilibrium adsorption capacity of fresh carbon. No further loss of adsorption capacity was found for carbon which subsequently was regenerated two more times, i.e., for a total of three sequential microbiological regenerations.
Solubility of ethylene in several polar and non‐polar solvents
Authors: Sahgal A. , La H. M. , Hayduk W.
Published: March 2009

Solubilities of ethylene at atmospheric pressure and temperatures ranging from −9°C to 70°C are reported in solvents ranging from the non‐polar ones, heptane, dodecane, carbon tetrachloride, carbon disulfide and chlorobenzene to the highly polar ones, isopropanol, butanol and ethylene glycol. A useful relation was observed between ethylene solubilities in non‐polar solvents and those of methane, ethane and propane, along with the corresponding energy of vaporization at the normal boiling for those gases. In the highly polar solvents on the other hand, hydrogen bonding (H‐bonding) factors were found more useful in relating solubilities in one hydrogen bonding solvent to those in other hydrogen bonding solvents.
Prediction of heats of mixing of liquid mixtures containing alkane, chloroalkane and alcohol by an analytical group solution model
Authors: Lai Tu Tam , Doan‐Nguyen T. Huong , Vera Juan H. , Ratcliff Gerald A.
Published: March 2009

An analytical group solution model (AGSM) previously developed for the prediction of heats of mixing has been applied to ternary group, ternary component mixtures. A simple temperature dependence is proposed for the group interaction parameters. Temperature independent coefficients were obtained in the temperature range 15 to 35°C for mixtures containing CH2, OH and Cl groups. These coefficients allow the prediction of heat of mixing for binary or ternary mixtures containing alcohols, chloroalkanes and alkanes. Heats of mixing for the following systems are reported: 1‐chlorobutane and 2‐chlorobutane with both n‐hexane and n‐octanol at 35°C; n‐octanol — n‐hexane at 25 and 35°C; and three chords of the ternary system 1‐chlorobutane — n‐octanol — n‐hexane at 25 and 35°C.
Solubility and diffusivity of oxygen in aqueous sucrose solutions
Authors: Hikita H. , Asai S. , Azuma Y.
Published: March 2009

Solubility and diffusivity of oxygen in aqueous sucrose solutions of various concentrations were measured at temperatures from 15° to 45°C and at atmospheric pressure. The solubility of oxygen could be correlated well by the method of van Krevelen and Hoftijzer. The diffusivity of oxygen was found to be proportional to the −2/3 power of the viscosity of the solution.
Using a statistical multiresponse method of experimental design in a reaction network study
Authors: Boag I. F. , Bacon D. W. , Downie J.
Published: March 2009

A statistical design method for multiresponse models was used in an experimental study of a reaction network. The study involved the vanadia‐catalysed oxidation of o‐xylene using a recirculation reactor. Concentrations of reactants and temperature were used as operating variables, and the concentrations of products were the measured responses.

The published design procedure was modified by conducting several runs after each design evaluation to reduce computing costs while retaining the benefits of statistical design and analysis. This enabled network analysis to be conducted efficiently to the limits of the equipment, and pointed the way to improved estimates of the parameters.
Waves on thin films of pseudoplastic liquids
Authors: Tekic Miodrag N. , Mitrovic Milan
Published: March 2009

Wavy flow of a thin pseudoplastic fluid film down a smooth vertical plate has been analytically studied. A boundary layer equation of motion was solved to obtain expressions which permit the prediction of characteristic parameters values of pseudoplastic liquids in wave motion. The presented analysis gives better agreement between predicted and measured values of wavelength and critical regime for wave inception than the existing theories. Also a good agreement was obtained between predicted and measured values of the mean film thickness.
A study of factors affecting the ice nucleation temperature in a domestic water supply
Authors: Gilpin R. R.
Published: March 2009

The ice nuclation temperature in a typical water supply was measured and found in general to be in the range of —4° to —7°C. This amount of supercooling is very significant in a water main in that it will have a major effect on the way in which a pipe freezes. The effects of the temperature‐time history of the water, of the presence of certain nuclating agents and of mechanical vibration on the nucleation temperature were determined and were related to the behaviour of undissolved particulate matter in the water. In addition to determining the nucleation temperature in a water supply under various conditions this study also serves to illustrate some of the phenomena that can be expected in general when hetergeneous nucleation occurs.
Multistage multicomponent separation calculations using thermodynamic properties evaluated by the srk/pr equation of state
Authors: Shah M. K. , Bishnoi P. R.
Published: March 2009

A computational procedure using thermodynamic properties evaluated by the Soave‐Redlich‐Kwong' (SRK) equation of state or the Peng‐Robinson (PR) equation of state is developed for multistage multicomponent separation processes. The procedure makes use of the Ishii‐Otto convergence scheme with the proposed modifications for application with the equation of state. A new technique is developed to improve an initial estimation of temperature profile in a column. The computational procedure is tested on CDC CYBER 172 computer for a wide range of problems including lean oil absorbers, reboiled absorbers and fractionators and a debutaniser operating in a natural gas processing plant in Alberta. The computational results are compared with those obtained using the Chao‐Seader model for generating the required thermodynamic properties. It is concluded that the present computational procedure can be used more reliably over a wider range of processing conditions such as those involved in the cryogenic separation of natural gases and in the separation of heavy hydrocarbon mixtures.
Application des chaînes de markov discrétisées à la simulation des réacteurs chimiques
Authors: Masson H. A. , Tolley M. D.
Published: March 2009

Gibilaro et al(1) ont montré l'intérět du formalisme des chaǐnes de Markov(2), discrétisées dans le temps, pour la simulation de distribution de temps de séjour d'éléments fluides dans des mélangeurs imparfaits.

La présente note reprend brièvement les points essentiels de leur travail. On décrit ensuite quelques extensions de la théorie originale. On montre comment introduire les temps morts, une alimentation continue en traceur, et comment généraliser au cas de systèmes sièges de réactions chimiques.

Trois exemples simple illustrent la mise en oeuvre de l'algorithme et permettent de juger de la précision obtenue, par comparison avec les solutions analytiques (méthodes) de Merson et de Runge‐Kutta).
A kinetic model for continuous‐flow stirred biological reactors
Authors: Lo S. N. , Marchildon L. , Lakshmanan R. , Garceau J. J.
Published: March 2009

A kinetic model is proposed to describe the mechanisms of substrate removal in continuous‐flow, stirred bioteactors for bacterial autocatalytic reactions. A lumped parameter, defined as the average number of contacts between microorganisms and limiting substrate per unit time per unit of biomass, is used to study the overall effect of mixing on reactor performance. Under all the conditions studied, the overall effect is such that the larger the value of the parameter the better the reactor performance. The influence of formation and decomposition of cell‐substrate intermediate on substrate removal is also presented.
The influence of precipitated asphaltenes on sedimentation of particles in coal liquids
Authors: Verhoff F. H. , Lui S. S. , Henry J. D.
Published: March 2009

Antisolvent addition to coal liquids causes the precipitation of asphaltenes on mineral particles and increases their sedimentation rate. This paper develops a mathematical model of the sedimentation rate of a single particle or agglomerate of particles. It was found that if the difference in density between the solid and the precipitate is more than twice the difference in density between the precipite and the liquid, the sedimentation rate would decrease initially upon precipitation. A simple experiment was performed to confirm the prediction. Further it was found that the agglomeration of particles had a stronger effect upon the sedimentation than the changes in particle size.
Height and structure of the fountain region above spouted beds
Authors: Grace J. R. , Mathur K. B.
Published: March 2009

The height and structure of the fountain which forms in the freeboard region above the annular surface of a spouted bed is predicted based on equations of motion for particles entrained in the spout. Predicted fountain heights are in good agreement with a wide range of experimental values covering polystyrene particles, wheat, millet, glass beads and ammonium nitrate spouted in columns of diameter up to 0.292 m. A simplified procedure in which drag is ignored gives good results also under most circumstances of practical importance. The theoretical niodel proposed can be used to predict the voidage profile in the fountain core and the holdup of particles ill the freeboard, both of which may be useful in estimating the performance of spouted bed reactors.
Correlating parameters for axial dispersion in liquid fluidized systems
Authors: Krishnaswamy P. R. , Ganapathy R. , Shemilt L. W.
Published: March 2009

The dispersion coefficient, the time delay and the time constant, as parameters associated with models of liquid phase axial dispersion in fluidized systems, have been correlated using available literature data for fluidization involving a wide range of fluid and particle properties. The results permit prediction of these parameters from only a knowledge of the bed voidage. A comparison with Chung and Wen's1 correlation demonstrates the superiority of the present correlation.
Conversions and temperature rises in a laminar flow reactor for the hydration of acetic anhydride
Authors: Golding J. A. , Dussault R.
Published: March 2009

The hydration of acetic anhydride in concentrated solutions has been studied in a vertical laminar flow reactor. The effects of flowrate, reactant concentration and reaction conditions on conversions and temperature rises were studied. An effect of the initial acetic acid concentration was observed. Thus at low acid concentrations there was good agreement between experimental and prediction values. However, at high acid concentrations, above 1.2 mole/l acid, the reaction was apparently inhibited and experimental results were lower than predicted. Radial teniperatnre profiles were measured and found to be relatively flat despite the low Reynolds numbers existing iu the reactor.
Calculations of gas phase diffusion and reaction in heterogeneous catalysts the importance of viscous flow
Authors: Haynes Henry W.
Published: March 2009

The problem of multicomponent gas phase diffusion fora single overall reaction in porous catalysts is analyzed using the dusty‐gas theory. Recent authors have shown that neglecting internal pressure gradients results in modeling inconsistencies and errors in computation in small pore catalysts. However, calculations based upon kinetic theory estimates of the transport coefficients reveal that the viscous flow contribution to the component i molar flux can be neglected with excellent justification. The resulting equations are internally consistent and greatly simplified. For illustrative purposes the multicomponent example of P. Schneider7 is reformulated to take into account nonuniform pressure (but negligible viscous flux), and as a consequence the inconsistency noted in the original reference is removed. Two methods for computing the effectiveness factor are discussed.
Comparison of catalytic cracking on lax and lay catalysts
Authors: Yeh Jer‐Jeng , Wojciechowski B. W.
Published: March 2009

A comparison of the cracking activity and gasoline selectivity on LaX and LaY has shown that LaY is a superior catalyst both in terms of activity and in terms of gasoline selectivity at high conversions.

There is reason to believe that the LaX catalyst used in this work was partly diffusion limited within the crystallite and that the activity and selectivity of X catalysts can be improved by producing X sieves in microcrystalline form.
Vapor‐liquid equilibrium behavior of the ethane—n‐butane—n‐hexane system
Authors: Dingrani J. G. , Thodos George
Published: March 2009

A high pressure visual cell was designed and constructed for the study of vapor‐liquid equilibria of rnulticomponmt systems at elevated temperatures and pressures. One of the unique features of this vapor‐liquid equilibrium cell facility resides in the ability to measule pressures using a transducer connectcd directly to the equilibrium chamber of this cell. In addition, the design of this cell, incorporated the capability to permit the withdrawal of vapor and liquid microsamples from the respective phases in equilibrium. The composition of these microsamples was established with a gas chromatographic facility provided with a thermal conductivity detector. The overall performance of this vapor‐liquid equilibriiini facility was tested on the system ethane‐n‐butane for which reliable vapor‐liquid equilibrium data are already available in the literature.

Five different charges of the ethane‐n‐butane‐n‐hexane system were investigated with this facility for temperatures ranging from 48.3 up to 143.5°C and pressures up to 7619 kPa (75.19 atm). For these conditions, K‐values were established from the experimental measurements on this ternary system. K‐values calculated using the BWR‐method for conditions corresponding to the experimental measurements produced K‐constants that were in good agreement with the measured values. For these calculations, the original BWR‐equation, constants and mixing rules were employed.
Decompression wave velocities in natural gases in pipe lines
Authors: Groves T. K. , Bishnoi P. R. , Wallbridge J. M. E.
Published: March 2009

The events following rupture of a pipeline containing gas at high pressure are very similar to those following rupture of the diaphragm in a simple shock tube. A description of the decompression wave resulting from such a rupture, and its rate of propagation in natural gases is the primary purpose of this paper. A computer program is written to calculate decompression wave velocities. The required thermodynamic properties are calculated using the Soave‐Redlich‐Kwong (SRK) equation of state and the results of computed wave velocities are presented and compared to values observed in the decompression zone of a shock tube.
Comparison of several turbulence models for predicting flow patterns within confined jets
Authors: Tennankore K. N. , Steward F. R.
Published: March 2009

Numerical solutions of the differential equations governing isothermal and nonisothermal confined jets have been obtained for three different models of the turbulence correlation terms. The models used were

1) mixing length model

2) k‐l model

3) k‐e model

A comparison of the predictions with experimental data taken in a confined jet system indicates that in the absence of a measured distribution of the kinetic energy of turbulence at the entrance section the mixing length model provided the best results for the isothermal case. For the nonisothermal jets, however, it was found that the k‐e model gives better prediction than the other two models in spite of the lack of measured distributions for the kinetic energy of turbulence at the entrance.
The coalescence of n‐Hexane droplets in aqueous electrolyte solutions
Authors: Sagert Norman H. , Quinn Michael J.
Published: March 2009

Coalescence times, measured by high speed cinematography, are reported for n‐hexane droplets formed on adjacent nozzles in pure water and in dilute aqueous solutions of the electrolytes KCl, KBr, KI, NaCl, and Na2SO4. Coalescence times in pure water were 17 + 11 ms, in satisfactory agreement with recent theories of Ivanov and of Reed, Riolo and Hartland. Coalescence times increased on addition of electrolytes, except for KI. Limiting values of coalescence times in electrolyte solutions could be accounted for by the theories of Marrucci. Thus the Marrucci parameter crk2/λ may be taken as a guide to droplet coalescence in solutions of solutes such as electrolytes which only change interfacial tensions slightly. The coalescence times are larger than for air‐electrolyte solutions, largely because of the lower Hamaker‐London attraction with the present system.
Absorption of sulfur dioxide into limestone slurry in a stirred tank reactor
Authors: Uchida S. , Moriguchi H. , Maejima H. , Koide K. , Kageyama S.
Published: March 2009

An experimental study on the absorption of low concentration sulfur dioxide into limestone slurries in a stirred tank reactor has been performed. The absorption rates under various experimental conditions were measured and the absorption processes have been discussed. The analysis of the experimental data shows that the limestone dissolution process seems to play a very important role in the absorption.
Separation by thermodialysis of acetic acid aqueous solutions
Authors: Bellucci F. , Bobik M. , Drioli E. , Gaeta F.S. , Mita D.G. , Orlando G.
Published: March 2009

The effect of thermodialysis has been investigated in non‐ideal liquid mixtures, employing coarse, unselective porous partitions.

For the case investigated — aqueous solutions of acetic acid — the temperature differences applied across the partition induced remarkable separations of the components. This effect may be applicable to the purification of industrial wastes. Furthermore, the investigation of thermodialysis in non‐ideal solutions has provided valuable data, aiding to our understanding of the physical basis of the phenomenon.
Poisoning and regeneration of claus alumina catalysts
Authors: George Zacheria M.
Published: March 2009

Samples of poisoned alumina catalysts obtained from Claus sulfur recovery plants in Alberta have been regenerated. Poisoned catalysts had SO4=, NO3−, sulfur and carbon deposits, discoloration, and low surface areas. Whereas the Claus catalytic activity of the poisoned catalysts varied widely, regeneration uniformly enhanced the catalytic activity to the same level as fresh alumina. The activity comparisons were made under conditions similar to those of a third Claus converter of low partial pressures of H2S and SO2 and high partial pressure of H2O, where maximum catalytic activity is required to promote Claus reaction.
Gas‐solid reactions I: A grain‐cell model for complex reactions
Authors: Fahim M. A. , Wakao N. , Ford J. D.
Published: March 2009

A mathematical model has been developed to describe the progress of a consecutive reaction taking place in a porous spherical pellet composed of two solids. Two basic parameters are derived: a Thiele type modulus (H), and a kinetic‐structural parameter (γ). The system of partial differential equations representing the model has been solved numerically, to obtain conversion‐time relations as a function of the physical and kinetic parameters of the system. Highest conversions are obtained at low values of both γ and H.
Gas‐solid reactions II: Reduction of cobalt sulfide in the presence of calcium oxide
Authors: Fahim M. A. , Ford J. D.
Published: March 2009

The results of an experimental program to test the applicability of the grain‐cell model to complex gas‐solid reactions are presented. The hydrogen reduction of solid cobalt sulfide (CO9/8S) in the presence of calcium oxide was chosen for study. Powders of both solids were mixed in a molar ratio of 3.0 (CaO:Co9/8S), compressed into pellet form, then reduced by hydrogen in the temperature range 600‐800°C. The experimental results at different operating conditions were compared with the grain‐cell model, using the Thiele type modulus (H) as an adjustable parameter. In the presence of excess calcium oxide, the structural‐kinetic parameter (γ) was essentially zero, and (H) was found to be the effective parameter, controlling reduction rates. Good agreement between experimental results and model was obtained.
The discrete residence time distribution of a distillation colum operated with microprocessor controlled periodic cycling
Authors: Furzer I. A.
Published: March 2009

The fluid flow in a distillation column was studied by measurements of the discrete residence time distribution. The column, 100 mm in diameter was fitted with 5 sieve plates of 14.8% free area with a 6.1 mm hole diameter on a 635 mm plate spacing. The periodic control was obtained using a JOLT microprocessor system. An analysis of the discrete residence time distribution yielded the parameters in the (2S) model that describes the fluid flow. Modifications to the column internals are required to alter these parameters, if the maximum separation improvements are to be obtained.
Separation of organic mixtures by sequential gas‐liquid chromatography
Authors: Barker P. E. , Liodakis S. E. , Howari M. I.
Published: March 2009

A new sequential continuous chromatographic refiner (SCCR‐2) for high temperature production scale G.L.C. (gas‐liquid chromatographic) separations is described. In this equipment the counter‐current movement between the gas and liquid phase is simulated by sequencing a system of inlet and outlet port functions around twelve static 2.54 cm internal diameter and 61 cm long stainless steel columns. The versatility of the equipment has been demonstrated by the separation of equivolume mixtures of the halocarbons arklone P/genklene P, methylchloroacetate/ethyl lactate and ethyl caprate/ethyl laurate at temperatures of 60°, 105° and 160°C respectively. Throughputs between 21–75 cm3h−1 have been explored with product purities in excess of 99.8% achieved under certain process conditions.
Mixing of large particles in two‐dimensional gas fluidized beds
Authors: Fan L. T. , Chang Y.
Published: March 2009

The fluidization and solids mixing characteristics of very large particles were investigated in a two‐dimensional gas fluidized bed. Bubble or slug induced drift and gross solids circulation appeared to be the predominant solids mixing mechanisms in this large particle bed. The contribution from wake mixing appeared to be negligible and radial mixing was more rapid than axial mixing. Apparently, segregation in the axial direction resulted from preferential transportation of the lighter particles upwards with rising bubbles and from interparticle competition to fill the voidage created by the rising bubbles. No appreciable segregation occurred in the radial direction. A nonstationary random walk model has been developed to characterize mixing and segregation of fluidized large particles.
Integral conversion of SO2: Hysteresis and rate discontinuities
Authors: Kovenklioglu S. , Delancey G. B.
Published: March 2009

The oxidation of SO2 was carried out over an American Cyanamid V2O5 catalyst in an insulated integral reactor without significant interparticle resistances under the following conditions: 10 percent SO2‐air feed, feed temperatures in the range of 430°C to 590°C, 108 kPa pressure, and entrance temperatures of the gases in the annular heat exchanger from 400°C to 450°C, with one set of conversions being obtained without annular air flow. Gas analysis was accomplished by the oxidation of SO2 to SO3 with potassium permanganate. The method was fully tested before adoption. Final conversions in the range of 5 to 60 percent were observed. A hysteresis loop was found in the plane of outlet conversion versus the average feed temperature. The multiplicity is possibly stable but probably decays with the time constants in the order of days which is evident from the transient data that were obtained. A one dimensional model was able to correlate the conversion data through the Arrhenius rate parameters in the Boreskov‐Sokolova(8) rate expression which changed from A = 1.92 × 107 m3/(s·kg) and E = 151 MJ/kmol to A = 0.344 m3/(s·kg) and E = 33.5 MJ/kmol at a calculated temperature at the surface of the catalyst of 517°C. Similar behavior has been observed in other studies concerned with basic kinetic studies over catalyst pellets. The analogy between the behavior of the catalyst pellets and the behavior of the integral reactor can thus be fully drawn with respect to hysteresis and rate discontinuities.
Behaviour of V2O5 — catalyzed CO oxidation in the presence of inert, diluent gases
Authors: Silva A. E. M. , Hudgins R. R. , Silveston P. L.
Published: March 2009

A study was conducted on the oxidation of CO over an industrial potassium‐promoted V2O5 catalyst in order to study the influence of He, Ar, Kr, SF6 and C4F8 diluents on the reaction rate. A differential flow reactor was used between 400° and 440°C with partial pressures of CO2, O2 and diluents varied from approximately 7 to 150 kPa. All the diluents inhibited the reaction rate to varying degrees. Experiments were also performed in which one diluent gas was displaced by another in the reaction mixture. These experiments indicated that the diluents could be arranged in the following increasing order of sorptive interaction with the catalyst:

He or Ar < Kr < SF6 or C4F8

It was concluded that conventional site‐blockage was unable to explain the influence of the diluents. An adsorption interaction between the diluent and the surface complex of the rate limiting step was postulated to explain the inhibition of diluents in CO oxidation and the enhancement of diluents in SO2 oxidation on the same catalyst.
Ion exchange with irreversible reaction in deep fluidized beds
Authors: Koloini T. , ŽUmer M.
Published: March 2009

The exchange of CI− ion between dilute aqueous solutions of hydrochloric acid and the ion exchange resin IRA‐425 in fluidized beds was studied in a laboratory size column. Analysis of the experimental data showed that axial mixing of particles in deep beds was incomplete and also that packed and fluidized bed break‐through curves were similar. A model is proposed describing the bed as a series of mixing stages for solids with axially dispersed flow of liquid. Data are presented in support of such a concept.

An empirical method is proposed for prediction of the break‐through curves at various operating conditions, requiring only a very limited amount of experimentation.
A fluidized bed catalytic cracking regenerator model
Authors: Effects Grid , Errazu A. F. , Lasa H. I. De , Sarti F.
Published: March 2009

A grid model including thermal effects is proposed. The aim is the simulation of a fluidized catalytic cracking regenerator similar to the industrial unit of Destileria La Plata, YPF, Argentina.

It is demonstrated that a simple C.S.T.R. model without bypass of gas feed entering the bed provides a good approach for representing the fluidized bed including the grid region.

In addition, by means of the C.S.T.R. model, it is shown that there exist two characteristic operating regions: a zone where (Coo – Co) depends on the initial coke concentration and a zone where (Coo – Cc) is controlled by oxygen supply.
Thermodynamic properties of the system toluene — 1, 1, 1‐trichloroethane
Authors: Sundaram S. , Viswanath D. S.
Published: March 2009

Data on molar excess enthalpy on mixing at 298.15 K and 308.15 K, vapor‐liquid equilibrium, latent heats of vaporization at 91.444 kPa and vapor pressures for the system toluene – 1, 1, 1‐trichloroethane are presented. A simple adiabatic calorimeter designed for molar excess enthalpy measurements is described, tested and used.
Flow of slurries of coarse particles at high solids concentrations
Authors: Televantos Y. , Shook C. , Streat M. , Carleton A.
Published: March 2009

Using a lock hopper feeding system, gravel and coal shale slurries containing particles of median diameter approximately 4 mm were transported at high concentrations through a pipe of I.D. 7.87 cm at velocities below 3.5 m/s−1. In addition to the usual measurements of velocity, delivered concentration and hydraulic gradient, in‐situ concentrations and particle velocities were determined. With these measurements, a two‐layer model of stratified flow of the type proposed by Wilson was examined and found to give satisfactory predictions. Coefficients of wall friction were found to vary with velocity. Minimum values of these coefficients agreed with the results of direct shear tests. This variation could be attributed to stick‐slip processes at low velocities and a change in the nature of the interparticle stress at higher velocities.
A theory for effective solid stresses in the annulus of a spouted bed
Authors: McNab G. S. , Bridgwater J.
Published: March 2009

With a growing interest in the large scale application of spouted beds, it is important to assess the stresses generated in the annular solids. Factors such as bed height, fluid pressure gradient, spout radius, frictional conditions at spout and vessel walls, and the angle of internal friction of the solid particles may all affect the stresses. Here it is shown how all these variables may be included in an analytical model for the vertical stress distribution in a spouted bed. The approach proceeds through the determination of the mean effective stress on a horizontal plane of the bed is a function of height. Distribution factors, as employed by Walker for bins, are used to relate stresses at the spout wall and the vessel wall to the mean effective stress on a horizontal plane.
Quenching of pyrolysis products of p‐xylene in toluene‐kinetic studies of acetone‐soluble products
Authors: Kumar A. , Rao A. N. , Gupta S. K.
Published: March 2009

Pyrolysis of p‐xylene was carried out in a tubular reactor at partial pressures varying from 0.184 kPa to 2.199 kPa with steam as a diluent. The product stream was quenched in toluene, and the solid products formed in quenching were shown to consist of p‐cyclophane (acetone insoluble) and linear dimer, linear trimer and one immovable component (in TLC analysis) constituting the acetone‐soluble part. Their rates of formation in the quencher were experimentally determined. The kinetic model which was used to explain the rate data of p‐cyclophane formation(1) was extended to include the formation of linear dimer and trimer of p‐xylene. The rate expressions derived from the kinetic model were shown to be consistent with experimental results.
Simulation and design of distillation units for treatment of sulfite pulping condensates to recover methanol and furfural: Part I: Incorporation with an evaporation unit and use of secondary steam
Authors: Zacchi G. , Aly G.
Published: March 2009

A distillation unit was simulated using DESTLA, a computer program for steady‐state calculations of general multi‐component distillation units. Vapor‐liquid and liquid‐liquid equilibria were both computed by EQUIL, a computer program for computation and plotting of such equilibria. The simulations resulted in a distillation unit consisting of three columns. Energy consumed in the first column dominates the operating costs of the unit. The first of the three different alternatives studied for satisfying the energy requirements of the first column is presented. Incorporating the first column into an evaporation unit yields low steam consumption. However, a decrease in evaporation capacity due to the temperature drop in the first column and complex control design are the disadvantages associated with this alternative.
Heats of mixing of amine‐alcohol systems. An analytical group solution model approach
Authors: Siman Jaime E. , Vera Juan H.
Published: March 2009

Measured heats of mixing for amylamine with n‐propanol, n‐butanol and n‐pentanol at 15°C and 35°C are reported. This experimental information has been used together with other literature heats‐of‐mixing data on amine‐alcohol systems to test the ability of the extended Analytical Croup Solution Model (AGSM) to correlate and predict exothermic heats of mixing. Predictions for amine‐alcohol systems, not included in the set of reference systems, are good with the exception of the predictions for systems containing methanol.
Excess enthalpies of binary gaseous system ethylene + carbon dioxide by flow calorimetry
Authors: Ba Le B. , Kaliaguine Serge C. , Ramalho R. S.
Published: March 2009

Excess enthalpies in the gas phase for the ethylene‐carbon dioxide system have been measured by a continuous‐flow isothermal calorimeter. Excess enthalpies are presented for mol fractions ranging from approximately 0.15 to 0.85, at three temperatures: 298.15, 318.15 and 338.15 K. For each isotherm, measurements were made at four pressures: 1.036 MPa (150 psia), 2.072 MPa (300 psia), 3.454 (500 psia) and 4.835 MPa (700 psia). The experimental results are compared with predictions using the Benedict‐Webb‐Rubin and Redlich‐Kwong equations of state.
Mixing effects and hydrodynamics of vortex rings
Authors: Rohatgi A. , Baird M. H. I. , Wairegi T.
Published: March 2009

Vortex rings have been formed in water by impulsive flow through an orifice, and mixing effects due to the lings have been measured. Laboratory tests on the mixing of stratified layers of salt solution by vortex rings formed at a 6.35 cm diameter orifice have indicated that Froude number is an important factor in determining the energy efficiency of mixing. Field tests using a 25.4 cm orifice in Hamilton Harbour (18 m depth of water) have shown a small mixing effect. Further experiments with a 25.4 cm orifice in a test tank have shown that the vortex rings have a range of at least 30 m.
Convective heat transfer in a rotary kiln
Authors: Tscheng S. H. , Watkinson A. P.
Published: March 2009

An experimental study of convective heat transfer from hot air to the solid charge and walls in a non‐fired rotary kiln is reported. Ottawa sand was heated by passing it counter‐current to a flow of preheated air in a 2.5 m × 0.19 m I.D. rotary kiln. Axial temperature profiles of gas, wall and solids were measured. Local and average convective heat transfer coefficients from gas to solids and from gas to wall were determined assuming plug flow of gas and solids. Solid feed rates to 1750 kg/m2 h and air rates to 3300 kg/m2 h were investigated at rotational speeds to 6 r/min, holdup ratios to 17% and gas temperatures from 350–590 K. The gas/solids convective coefficient was found to depend on the gas through‐put and to a lesser extent on solids holdup and rotational speed. Over the range tested, the angle of kiln inclination, solids throughput and particle size showed no significant effect on heat transfer. Gas/wall coefficients were about a factor of ten below gas/solid coefficients. Heat transfer results are compared to the limited data available in the literature, and to commonly used equations. Correlations of the experimental data on gas/solids, and gas/wall coefficients are presented; data from the literature on the wall/solids heat transfer coefficient are summarized.
Theoretical analysis of laminar flow heat transfer in a flat‐duct wall reactor
Authors: Mori Shigeru , Inoue Toshiaki , Tanimoto Akira
Published: March 2009

Conjugated heat transfer in steady state was studied, assuming the interfacial reaction to be instantaneous and the flow to be a fully‐developed laminar condition. The thermal boundary condition at the outer surface of the duct wall is specified as the first kind or the third kind. Influences of the interfacial reaction, the conductance of the wall and the external convection on the heat transfer characteristics were found to be substantial through calculated numerical results of the interfacial temperature and the local Nusselt number. Cases with uniform interfacial heat source and without it were also examined under the third kind boundary condition.
Concentration multiplicity and stability for autocatalytic reactions in a continuous stirred‐tank reactor
Authors: Lin K. F.
Published: March 2009

Concentration multiplicity and stability for autocatalytic reactions of the type A + R → R + R with overall rate expression \documentclass{article}\pagestyle{empty}\begin{document}$ -{\rm r}_A = {\rm kC}_A^m {\rm C}_R^n $\end{document} in a continuous stirred‐tank reactor (CSTR) is analyzed in a rigorous way in this paper. Important parameters for multiplicity criteria are reaction orders m and n, dimensionless space time Θ, and the ratio P of feed concentration of R to that of A. Necessary conditions for the system to have multiple exit concentrations (conversions) are defined in the (m, n, P) space. Multiplicity is guaranteed by limiting the dimensionless space time in a proper range in addition to the necessary conditions. Stability analysis shows that there is no periodic oscillation for the system. The upper and lower steady states of multiple solutions are both asymptotically stable. A unique steady state is globally stable.
Cultivation of spirulina maxima in an annular photochemical reactor
Authors: Leduy A. , Therien N.
Published: March 2009

An 8‐L annular photochemical reactor has been designed and built for the cultivation of micro‐ or semi‐microalgae at the laboratory scale. It may be operated in batch or continuous mode and is controlled for pH, temperature, gas mixture ratio (CO2 and air), flow rate, light intensity and also illumination type (daylight or plant growth light) and mode (continuous or intermittent). It behaves as a perfect mixed reactor for all concentrations of algal cells. The reactor was used for the cultivation of the blue‐green alga Spirulina maxima in a synthetic medium in both batch and continuous operations. At the dilution rate of 0.24 day−1, the optimal productivity was 0.91 g/L‐day for biomass or 0.55 g/L‐day for protein. This is equivalent to 14.5 g/m2‐day for biomass or 8.7 g/m2‐day for protein. The optimal productivity as well as the chemical composition of the algal biomass were comparable to results obtained from pilot plant studies and reported in the current literature.
The effectiveness of static hold‐up for absorption with a chemical reaction in a packed trickle bed: General order kinetics
Authors: Patwardhan Vilas S.
Published: March 2009

The effectiveness f of the intetfacial area of the static hold‐up for absorption with a chemical reaction in a packed trickle bed depends upon both the hydrodynamics and the chemical kinetics. The dependence of f on operating conditions is investigated for a general [m,n] order kinetics, for a liquid phase controlled absorption process. The chemical reaction is assumed to be fast. The results are presented graphically for n > 0. Analytical expressions are developed for the special case of n =0.
Cristallisation du trihydrate d'alumine: Concentration d'équilibre et constante cinétique de croissance
Authors: Flament Frederic , Cloutier Leonce , Methot J.‐Claude
Published: March 2009

Experimental crystallization of alumina trihydrate from Bayer's process caustic solutions was performed at different temperatures and sodium hydroxide concentrations to obtain equilibrium concentrations of sodium aluminate. A first correlation is presented to predict the equilibrium state, and a second one for estimation of equilibrium concentration from initial crystallization conditions. This last equation can be utilized for mathematical models for industrial crystallization of alumina trihydrate. Results indicate equilibrium concentrations of alumina trihydrate which are 17% higher than those obtained experimentally from synthetic solutions and 10% higher than those from other types of industrial solutions. The apparent growth rate constant of particles has been evaluated for each experiment: results correlated by an empirical relation show that this constant is not only a function of temperature.