bluuebunny/crossref_metadata_2025 huggingface dataset:
Axial dispersion in gases flowing through small bore helical column
Authors: Singh P. C. , Singh S.
Published: March 2009

The results of an experimental study on the axial dispersion of gases flowing in helical columns under laminar flow conditions are reported. The ranges of variables covered are 26.6 < λ < 98; 10 < NRe < 100; 0.176 < NSc < 1.359. The measured dispersion coefficients are correlated with Reynolds, Schmidt and Dean groups. A single dimensionless parameter, NDc (NSe0,5, was found to correlate the data well. Up to NDe (NSc)0,5 =10, dispersions in straight and coiled tubes exhibit very similar axial dispersion behavior.
Numerical analysis of spouted‐bed hydrodynamics
Authors: Kürsad Dündar , Kilkis Birol
Published: March 2009

Some of the basic concerns in the analysis of spouted‐bed hydrodynamics are the flow pattern and the pressure field of the fluid and the spout shape. These are closely related with other design concerns such as spoutability, minimum spouting velocity and maximum spoutable bed depth. A computer program was developed in order to determine the flow pattern, pressure distribution in the fluid phase and the spout shape for a given operational condition. The computer program relies upon a two region model with a spout and annulus element for an axisymmetric bed. The paper presents some results for grain drying beds and compares them with the existing experimental data qualitatively.
The axial dispersed plug flow model for continuous counter‐current adsorbers
Authors: Ruthven Douglas M.
Published: March 2009

The theoretical expression for the height equivalent to a theoretical plate is derived for a continuous counter‐current adsorber and compared with the expression for a chromatographic system. The ratio of these quantities is generally about 0.5 under practical operating conditions but the precise relationship depends on the Peclet and Stanton numbers as well as on the counter‐current flow ratio.
Vapor pressure and heat of solution of sulfur dioxide in 1‐methyl‐2‐pyrrolidone and its aqueous solution
Authors: Walker Richard J. , Schwartz Cecil H. , Wildman David J.
Published: March 2009

A new method was developed to measure the vapor pressure of sulfur dioxide above various liquid absorbents. It was applied to pure 1‐methyl‐2‐pyrrolidone and its aqueous solution at 50°C to 91°C for SO2 loadings of 3.73 × 10 4 kg/kg to 2.16 × 10 −2 kg/kg. A chemical model was developed. The heat of solution was calculated from the dependence of the vapor pressure on temperature and was 3.98 × 107 J/kmol (exothermic) for pure 1‐methyl‐2‐pyrrolidone. The vapor pressures disagreed with the only previously published set of results but were confirmed by independent measurements with a gas chromatograph.
Flow and mixing in swirling flow in a sudden expansion
Authors: Hallett W. L. H. , Günther R.
Published: March 2009

Experiments have been performed on swirling air flow in a sudden expansion in a model of a chemical reactor to study the effect of swirl intensity on flow and mixing. At the highest swirl tested a central recirculation zone was formed, while at swirl intensities below the critical value required for central backflow a precession of the flow was discovered in which the flow entering the expansion was deflected away from the axis of symmetry and caused to precess around it. The effect of these flow patterns on the mixing of a tracer gas with the main flow was studied by measuring both time‐mean values and turbulent fluctuations of the concentration. The time‐mean measurements indicated mixing at all swirl levels to be about equally fast, but measurements of fluctuation intensities showed a much higher unmixedness at low swirl, corresponding to the large‐scale motions of the precessing flow.
Tar sand extractions with microemulsions and emulsions
Authors: Sarbar Mohammad , Brochu Charles , Boisvert Michel , Desnoyers Jacques E.
Published: March 2009

Extractions of bitumen from tar sands were studied in parallel with pseudo‐ternary phase diagrams for the dispersion of bitumen in microemulsions. The three components were an active mixture (aqueous solution of surfactant and cosurfactant), a cosolvent and bitumen. Both pure and commercial surfactants were investigated, and, in general, commercial surfactants were more effective than pure ones. There was general correlation between the dispersion phase diagrams and the extractions. The microemulsion using Dowfax 2A1 as surfactant was an exception, being quite effective as an extractant even though not much bitumen could be dispersed in it. Most experiments were made with 2‐butoxyethyanol (BE) as cosurfactant, although a few were also made with phenol and pyridine. The efficiency of the cosolvent decreased in the order toluene > naptha > kerosene. Except for the case where the surfactant was Atlas G3300, extractions were more effective at 80°C than 25°C. With anionic surfactants pH did not seem to have much effect on the extractions.
Direct contact heat transfer – a better way to high efficiency and compactness
Authors: Rao D. N. , Mohtadi M. F. , Hastaoglu M. A.
Published: March 2009

A new concept in direct contact heat transfer is proposed which consists of carrying out combustion, and maintaining the resulting flame, directly within a flowing stream of water. The concept has been experimentally demonstrated in a prototype designed to handle 1200 kg/h of water. The system comes to steady state within 30 seconds. The process yields thermal efficiencies up to 97.5% and heat transfer coefficients up to 14 times those found in industrial spray tower contactors. The novel process possesses a great potential for industrial applications, such as process hot water supply, enhanced oil recovery using hot water, and compact steam generators.
Liquefaction behaviour of alberta subbituminous coals
Authors: Moschopedis S. E. , özüm B.
Published: March 2009

Subbituminous coals from the major regions of Alberta were evaluated as feedstocks in a direct liquefaction process. Autoclave tests were based on a “two level factorial design” statistical analysis to obtain information on coal liquefaction characteristics. The strongest interaction is found between the liquefaction temperature and time.
Prospects for a high octane gasoline synthesis catalyst
Authors: Ahmad Adnan , Wojciechowski Bohdan W.
Published: March 2009

The thermodynamics of synthesis reactions relevant to the production of alcohols, aldehydes, olefins, paraffins and aromatics lead us to conclude that the direct synthesis of aromatics will be favoured at temperatures around 650 K. We also note that the exothermicity of such a synthesis will be some 20% lower than that in conventional Fischer Tropsch synthesis.
Fluid to particle heat transfer in fluidized beds of mixed‐sized particles
Authors: Chen Peishi , Pei David C. T.
Published: March 2009

New experimental work on fluid to particle heat transfer was carried out in a 13.3 cm diameter bed of narrow‐cut and mixed‐sized ferric oxide particles. It was shown that, the channelling effect should be considered for fine particle systems. A correlation including the channelling effect was obtained from the experimental results. The addition of coarser particles into the fine particle systems provides better fluidization behavior and results in an increase in fluid to particle heat transfer coefficient. The most effective content of coarser particles is about 25%, and the optimum particle diameter ratio is about seven.
Heat transfer from a heating helical coil immersed in a jet‐stirred vessel
Authors: Hsu Yung‐Chien , Shih Ruey‐Fwu
Published: March 2009

Heat transfer coefficients for heating helical coils immersed in a jet‐stirred vessel have been investigated. Geometric factors, such as the tube diameter, the pitch of the helical diameter, the jet nozzle diameter and the turn‐down angle of the jet nozzle, have been studied. Four process liquids of quite different physical properties (water, 70% glycerin, isopropyl alcohol, and KSK oil‐260) have been used as the heating mediums. The correlation developed for these Newtonian liquids is similar to that obtained for vessels with conventional mechanical agitators. The jet power requirement was also obtained from experimental data.
Effect of surface resistance on gas absorption accompanied by a chemical reaction in a gas—liquid contactor
Authors: Asolekar Shyam R. , Desai Dilip , Deshpande P. K. , Kumar R.
Published: March 2009

An analysis of gas absorption accompanied by chemical reaction in the presence of interfacial resistance is presented. The analysis indicates that the effect of interfacial resistance on interphase mass transfer is significantly higher in presence of a reaction compared to the pure absorption case. For fixed values of surface resistance and contact time, the difference between the amount of gas transferred across the interface with and without surface resistance increases as the value of reaction velocity increases. For ranges of contact time and surface resistance of practical relevance, the influence of surface resistance is too high to be neglected while designing gas‐liquid contactors.
Isobaric vapor—liquid equilibrium in binary mixtures of m‐ and p‐xylenes with cyclohexene and cyclohexanone
Authors: Comelli Fabio , Francesconi Romolo
Published: March 2009

The vapor‐liquid equilibrium data of the binary mixtures of m‐ and p‐xylenes with cyclohexene and cyclohexanone are determined at P = 40 and 98.67 kPa. The systems show a nearly ideal behavior with no remarkable difference in the activity coefficients of m‐ and p‐xylenes. The experimental data are correlated by the Wilson expression.
Combined heat and mass transfer in free convection about a sphere
Authors: Hasan M. , Mujumdar A. S.
Published: March 2009

Combined heat and mass transfer characteristics of laminar free convection flow about a sphere are studied analytically. The analysis assumes negligible interfacial velocities due to mass diffusion as well as insignificant diffusion‐thermo and thermo‐diffusion effects. The surface of the sphere is assumed to be at a uniform temperature and a uniform concentration. Boundary layer equations for the system are solved for the specific cases of convective diffusion of water vapor and naphthalene into air by the local similarity and the local nonsimilarity approaches. Numerical results of the local Sherwood number, the local Nusselt number and local wall shear stress obtained from the local nonsimilarity solutions are reported in a tabular form and the local similarity results are displayed graphically. In the analysis the cases of aiding and opposing thermal and concentration buoyancy forces are considered. Cumulative mass flow rates along with the dimensionless representative profiles of temperature, concentration and tangential velocities are presented for various combinations of parameters.
Catalytic cracking and skeletal isomerization of n‐Hexene on ZSM‐5 Zeolite
Authors: Abbot J. , Wojciechowski B. W.
Published: March 2009

The catalytic cracking and skeletal isomerization of n‐hexenes on 60/80 mesh ZSM‐5 zeolite were studied in the temperature range 350–405°C. By applying the time‐on‐stream theory, the products of the reaction were identified as primary, secondary or both according to their optimum performance envelope (OPE) curves on product selectivity plots.

The products of cracking were found to be almost exclusively mono‐olefins and those in the range C3‐C5 were found to be stable primary, or primary plus secondary products. No C1 was found, and only traces of C2 as ethylene. The observed product distributions can be explained by a dimerization‐cracking mechanism with no product species having more than twelve carbon atoms. The probability of a fragment undergoing further cracking before desorption increased with temperature and the observed initial selectivities must be corrected to account for this process.

Methylpentenes, formed as unstable primary products, were the main isomers produced by skeletal rearrangement, with those derived from more stable carbenium ions predominating.

Paraffins, coke and aromatics were found in small amounts only.
Gas absorption accompanied by an instantaneous irreversible reaction in laminar falling films of pseudoplastic liquids
Authors: Hikita Haruo , Ishimi Kosaku , Koroyasu Sadatoshi
Published: March 2009

Gas absorption accompanied by an instantaneous irreversible chemical reaction into laminar falling films of power‐law liquids was studied theoretically. The convective‐diffusion equations for a solute gas and a liquid‐phase reactant were solved numerically and the numerical solution for the reaction factor was obtained as a function of the Graetz number, the concentration ratio, the diffusivity ratio and the power‐law index of the liquid.
Contribution à l'étude du transfert de chaleur à la paroi dans les récteurs à lit fluidisé gaz‐liquide‐solide à faible vitesse de liquide
Authors: Saberian‐Broudjenni M. , Wild G. , Midoux N. , Charpentier J. C.
Published: March 2009

A study has been made of the wall to bed heat transfer in three‐phase fluidized beds with cocurrent upflow of the gas and the liquid, the liquid being the continuous phase. The experiments were done using five different liquids (tetra‐chloroethene, cyclohexane, kerosene, gas oil, water), three different kinds of particles (glass beads, porous alumina spheres and cylinders) at liquid velocities below 30 mm/s and gas velocities from 10 to 150 mm/s. The phenomena observed with a foaming liquid are described. Different literature correlations proved to be non‐applicable at the velocities used in this work; moreover, they are not able to take into account the influence of the nature of the liquid. Therefore, a new correlation which fits well our results is proposed. The areas requiring further investigation before a safe prediction of the wall heat transfer coefficient in three phase fluidized beds can be possible are detailed.
The correlation between the strength factor and the true tensile strength of agglomerate spheres
Authors: Wynnyckyj J. R.
Published: March 2009

Spheres were produced from an iron‐ore concentrate by balling and subsequent shaping, and cylinders were cut from these spheres. Experimental data are presented, correlating the factor L/D2 for the spheres with the failure stress of the cylinders. The latter was measured by the diametral compression (Brazilian) test.

The results confirm the direct proportionality between the two, but only above a minimum level of agglomerate matrix strength. At less than 120 kPa the relationship may become complex. A qualitative explanation is offered in terms of the stress‐deformation behaviour of the spheres and cylinders.
Performance of combined cobalt—nickel—zirconia and HZSM‐5 catalyst systems for carbon monoxide hydrogenation
Authors: Varma R. L. , Bakhshi N. N. , Mathews J. F. , Ng S. H.
Published: March 2009

The synthesis of hydrocarbons via hydrogenation of carbon monoxide was investigated over cobalt—nickel—zirconia catalysts of various compositions in combination with zeolite HZSM‐5 in “mixed bed” and “follow bed” arrangements. These combinations resulted in the formation of aromatics in amounts as high as 30‐35 wt% under relatively mild operating conditions (1 atm, 250–280°C). Although the olefinicity of C2 and C3 fractions in the product stream was higher in the mixed bed compared to the follow bed arrangement, the selectivities to aromatics were comparable in the two bed arrangements. The aromatic selectivity was found to be sensitive to operating conditions. The formation of aromatics was favored at high HZSM‐5/metal catalyst ratios, low space velocities and high reaction temperatures. The product distributions obtained using various metal/zeolite bifunctional catalysts have been discussed.
The effects of temperature on the partial wet oxidation of peat
Authors: Sheppard John D. , Robey Herbert L. , Mckim Mathew P.
Published: March 2009

The effects of three reaction temperatues, 180, 200 and 220°C, on the partial wet oxidation of peat were investigated. A stirred reactor with a five litre working volume and continuous feed of peat slurry and air was used for the experiments. The effluent was separated into liquid and solid fractions and analyzed to quantify the effects of temperature. The carbon content and heating value of the recovered solids increased with temperature but yields were lower. The composition of the wastewater was only slightly dependent on the reaction temperature, and in all cases contained high concentrations of organics.
Use of opposed jet flame stabilization in a downhole steam generator
Authors: Mohtadi M. F. , Sarkar S.
Published: March 2009

Use of opposed jet flame stabilization in a direct contact steam generator which can operate in the borehole of an oil well was successfully demonstrated. Flame stabilization was obtained using a coaxially placed mixing cup from which a jet of premixed methane and air was introduced counter‐currently into the main air stream. Stable combustion was achieved within a wide range of air/fuel ratios. Steam generation rates of up to 75 kg/h, evaporation efficiencies of up to 92% and combustion intensities approaching 12 MW/m3 could be sustained over prolonged periods. A logic ignition control system ensured the safe operation of the generator. Exhaust gas analysis showed only negligible amounts of unburned methane and less than 0.5% carbon monoxide, when operating the generator at equivalence ratios of around 1.2.
Dynamic study and control of crystal size distribution (CSD) in a KCL crystallizer
Authors: Rohani S.
Published: March 2009

Previous works on crystal size distribution (CSD) control have indicated that a successful control scheme requires on‐line measurement of nuclei density. Such measurements can only be performed using an extremely expensive particle size analyzer. Besides the cost, the accuracy of such analyzers is restricted to low concentration slurries.

In the present work an attempt is made to replace nuclei density by an alternative process variable which can be measured easily and inexpensively. Theoretical analysis of a KCl crystallizer shows that slurry density in the fines loop is an excellent substitute for nuclei density. Preliminary tests show that a turbidimeter can be used for measurement of slurry density in the fines loop.

Proportional direct feedback control based on measurement of slurry concentration in the fines loop and manipulation of fines removal rate is shown to stabilize an inherently unstable crystallizer. The ability of the control scheme to suppress outside disturbances is also verified.
Fonctionnement hydrodynamique d'une cellule d'électrophorèse: Elements de calcul
Authors: Biscans B. , Bertrand J. , Sanchez V.
Published: March 2009

L'électrophorèse à écoulement continu utilise un champ électrique pour séparer, selon leur mobilité, les constituants d'un échantillon introduit dans un fluide porteur. Au cours de cette séparation, des difficultés telles que l'électro‐osmose ou la convection thermique perturbent la qualité de la séparation.

Cette publication analyse les divers paramètres influençant le fonctionnement hydrodynamique de la cellule d'électrophorèse. Les équations de modélisation et les conditions de frontières correspondantes, leur conditionnement et leur résolution par une méthode aux différences finies, conduisent à mettre en évidence l'effet des perturbations hydrodynamiques générées par un tel système.
Process safety management of a fuel gas conditioning facility using fault tree analysis
Authors: Stevenson Felicia D. , Maher Steven T. , Sharp David R. , Sloane Barry D.
Published: March 2009

This paper discusses a process hazard management study of a fuel gas conditioning facility based on stateof‐the‐art fault tree analysis techniques. This facility lowers the water and hydrocarbon dewpoints of a high pressure fuel gas exposed to frigid temperatures during distribution. Using hazards checklists and guidelines as well as internal reviews, various process hazards were identified for this facility. Computerized fault tree analysis techniques were used to identify the failure sequences which could lead to process hazards, and analysts used these results to evaluate the impact of specific hazards upon process safety. Through recommendations presented in the study, the facility owner gained an increased awareness of potential problems and made modifications to reduce the possibility of a hazardous condition and subsequent catastrophic failure.
Factors affecting the kinetics of the heterogeneous oxidation of ammonium sulfite
Authors: Ahmad Nadeem , Eroǧlu İinci̇ , Gürkan Türker
Published: March 2009

Absorption of oxygen into 0.09 – 0.7 M solutions of ammonium sulfite was measured by utilizing a stirred cell. The concentration ranges of the cobalt sulfate catalyst was 5.5 × 10−5 – 4.7 × 10−3 M and that of oxygen in the gas phase 21 – 100%. The theory of absorption with fast pseudo‐nth order reaction was used to find the order of intrinsic rate of reaction with respect to reactants and the catalyst. Above a critical sulfite concentration the order in sulfite is zero, in O2 is 0.4 – 1, and in CoSO4 is 1. Under those conditions a proposed reaction mechanism yields orders of zero, 1, and 1, respectively. Below the critical point the order in sulfite is 2, indicating that another reaction mechanism is applicable. Although an increase of the ionic strength enhances the reaction rate slightly, an increase of pH from 7.6 to 8.5 causes a 1.4 fold increase. Under oxidative conditions deactivation of the catalyst and insoluble precipitate formation is observed.
Influence de la coalescence électrostatique sur le débit d'une colonne d'extraction à mélangeurs‐décanteurs
Authors: Kumar Anil , Ansermet François , Hartland Stanley
Published: March 2009

Ce papier décrit les effets d'un champ électrique sur la coalescence d'une dispersion aqueuse formée lors de l'extraction du cuivre à l'aide des réactifs du type LIX*. Les résultats d'expériences en batch sont appliqués à une colonne de mélangeurs‐décanteurs de conception nouvelle (MIXET) pour en améliorer les caractéristiques hydrodynamiques. Les débits peuvent ětre augmentés jusqu'à 3.5 fois pour une vitesse de rotation constante (ou la vitesse de rotation augmentée jusqu'à 1.7 fois à débit constant) par application d'un champ électrique continu pulsé.
Spontaneous, random oscillations in the rate of CO oxidation over Pt/Alumina
Authors: Chakrabarty T. , Hudgins R. R. , Silveston P. L.
Published: March 2009

This note reports a study of the effect of inert diluents alone or in mixtures on the well known spontaneous oscillations in CO oxidation over a Pt catalyst. Irregular oscillations were observed with a nitrogen diluent but not when this diluent was replaced by argon. Adding SF6 at levels above 3.3% to argon induced oscillations, but when a similar level of CO2 or H2O was added to the argon diluent, oscillations were not found. Oscillations were observed only at the feed composition where one of the bifurcated steady states vanished.
Flow in the annulus of a bed of fine particles spouted with water
Authors: Kim Seung Jai , Littman Howard
Published: March 2009

The flow in the annulus of a water spouted bed of glass particles (275 to 774 μm) was studied experimentally in a cylindrical half‐column 50.8 mm in diameter.

An axisymmetric model, which assumes Darcy flow in the annulus and uses the experimental spout pressure distribution, predicts the flow and pressure fields in the annulus. The substantial differences between this flowfield and that for coarse particle beds that are observed are caused by differences in the normalized interfacial pressure profile.

The model predicts that both the fluid velocity and the normalized fluid velocity at the top of the annulus decrease as the particle size and bed height are reduced. Particles are observed to enter the spout primarily near the spout inlet in agreement with predictions of the axial spout voidage distribution.

The residence time distribution of the fluid in the annulus is relatively broad and the measured residence times are about 25% higher than those calculated.
The onset of slugging in horizontal condensers
Authors: Rashwan F. A. , Soliman H. M.
Published: March 2009

A mechanism is proposed suggesting that the wavy‐slug transition during horizontal condensation is initiated by a hydraulic jump. Based on this mechanism, a simple empirical correlation is developed and shown to be consistent in magnitude and trend with data for different fluids and different tube diameters. Further, a theoretical model is constructed for stratified two‐phase flow near the end of the condensation path utilizing the principles of mass, momentum and energy conservation. Results from the model together with the proposed slugging mechanism succeeded in defining a theoretical wavy‐slug transition line which agrees well with experimental flow regime data for a wide range of operating conditions.
Recent developments in packed columns
Authors: Kunesh J. G.
Published: March 2009

Highlights of a recently concluded four year experimental program on random packings are presented. They include (a) a revised definition of loading to achieve better reproducibility; (b) discussion of the erratic behavior near the “flood” point which helps explain the scatter in the published “flood” data; (c) new data showing that with proper distribution, efficiency is stable over a broad range; and (d) controlled maldistribution studies leading to guidelines for distributor design, fabrication and installation. The need to precisely define commonly used terms is emphasized.
Adsorption‐desorption studies on the radium‐silica system
Authors: Nirdosh I. , Trembley W. B. , Muthuswami S. V. , Johnson C. R.
Published: March 2009

Adsorption of radium‐226 on quartz is investigated. Adsorption isotherms are obtained for crystalline and sulphuric and hydrochloric acid‐treated quartz samples at pH 1 and 10. Desorption of radium‐226 from silica with EDTA and an EDTA‐KC1 mixture is also studied. It is found that radium‐226 adsorbed on silica is difficult to desorb whereas radium deposited on silica as radium sulphate is easily removed in EDTA solutions.
Particle transport in fouling caused by kaolin‐water suspensions on copper tubes
Authors: Melo L. F. , Pinheiro J. D.
Published: March 2009

Particulate fouling tests were carried out using kaolin‐water suspensions flowing through an annular heat exchanger with a copper inner tube. The flow rate was changed from test to test, but the fluid temperature and pH, as well as the particle concentration, were maintained constant.

In the lower range of fluid velocities (<0.5 m/s), the deposition process seemed to be controlled by mass transfer. The corresponding experimental transport fluxes were compared to the predictions obtained with several models, showing that diffusion governed particle transport. The absolute values of the mass transfer fluxes and their dependences on the Reynolds number were satisfactorily predicted by some of the models.
Attrition of spherical electrode carbon particles during batch fluidized combustion
Authors: Halder P. K. , Salatino P. , Arena U.
Published: March 2009

Spherical electrode carbon particles prepared from carbon rods of dry cell batteries have been used to study the attrition behaviour in a bubbling fluidized bed combustor. Experiments have been conducted in a 40 mm I.D. and 1 m high fluidized bed combustor operated at 1 m/s superficial velocity. The bed was operated with nitrogen and with two different oxygen concentrations at 850°C to study the effect of combustion on attrition of these particles. The experimental technique used allowed the time resolution of attrited fines generation, providing detailed curves of attrition rates as a function of time. Attrition rate constants have been evaluated. Results show an enhancement of attrition due to combustion even for spherical, homogeneous and smooth particles.
Dehydration of 1‐phenylethanol over solid acidic catalysts
Authors: Takahashi Takeshige , Kai Takami , Tashiro Masashi
Published: March 2009

Dehydration of 1‐phenylethanol has been carried out over a solid acidic catalyst in order to examine the effect of the concentration of effective acid sites on the reaction rate, styrene selectivity and catalyst fouling. The reaction rate increased with the concentration of effective acid sites, while styrene selectivity decreased. The catalyst deactivation depended upon the concentration of the effective acid sites and also the size of the micro pores in the catalyst. Taking into account the reaction rate and selectivity, ALO‐4 alumina was the most suitable catalyst for the present reaction. An activation energy for the dehydration over ALO‐4 alumina was 83.8 kJ mol−1. The dehydration reaction could be a useful tool for the characterization of the nature of the acid sites.
A pyrolysis process for tar sands
Authors: Lechner C. A. , Liapis A. I. , Findley M. E.
Published: March 2009

A thermal processing system for tar sands is developed and analyzed. Based on the Utah tar sands studied, the process is found to be operable using combustion of coke and unconverted bitumen as the energy source. It is estimated that about 80% of the spent sand is required to be recycled to the pyrolyzer to provide this energy source.

The volumes for the pyrolyzer and kiln are calculated for appropriate descriptions of tar sand characteristics, and the kiln volume is found to be particularly sensitive to the choices of temperature, air supply, and particle size.
Studies on the inhomogeneous nature of the silent discharge reactor: Part 1. Experimental investigations
Authors: Khan A. A.
Published: March 2009

Commercial application of the silent discharge reactor is confined to its use for the manufacture of ozone. Free electron concentration in the reaction space is determined by the occurrence of electron avalanches between the dielectrics and generation of transient primary reaction zones (PRZ) where the electron –‐ molecule collision reactions take place. Experimental studies have been carried out in order to increase the frequency of occurrence of PRZs as well as to enhance the mean electron energy within an individual avalanche. The dielectric surface has been treated with P.T.F.E. to reduce the recombination rate of O‐atoms. Results indicated that both methods of modifying the current pulse train have influenced the pattern of utilization of electrical energy. Similarly a P.T.F.E. coated dielectric has been found to be more efficient than an ordinary glass dielectric.
A new approach to jet phenomena gas entrainment and recirculation in a bidimensional spouted fluidized bed
Authors: Freychet N. , Briens C. L. , Bergougnou M. A. , Large J. F.
Published: March 2009

Although gas jets injected into fluid beds fluctuate, previous models assumed that they were steady. A new model separates the bed in a zone in which the jet is never present and a zone in which the jet fluctuates (a point in this zone will alternately be in the jet and in the emulsion phase). Its predictions matched the rate of gas entrainment into the jet and the rate of gas recirculation between emulsion and jet which were observed in a large 2 dimensional bed equipped with a “V” grid and a central jet.
Multiplicity in the partial oxidation of propylene over a copper‐molybdena catalyst
Authors: Labastida‐Bardales J. R. , Hudgins R. R. , Silveston P. L.
Published: March 2009

Measurement of rates of formation of acrolein and acetaldehyde in the partial oxidation of propylene over a copper molybdate catalyst were made under steady‐state and transient modes. These measurements disclosed a rate of product formation multiplicity apparently attributable to the oxidation state of the catalyst and not to surface phenomena usually thought to be the source of hysteresis in catalytic systems.
A nonlinear pi(d) controller
Authors: Jutan Arthur
Published: March 2009

The PID control algorithm remains the most widely used in the process industries. This is due to its simplicity (three tuning parameters, fixed structure) and its ability to satisfy the majority of process control needs. Here, a new nonlinear algorithm (the PI(D)) is presented, which maintains the simplicity of the PID, but is nevertheless able to outperform it in both load and set point changes. Tuning formulae and response curves for the PI(D) controller are presented.
Quench time modeling in propane ultrapyrolysis
Authors: Nighswander John A. , Huntrods Richard S. , Mehrotra Anil K. , Behie Leo A.
Published: March 2009

Pyrolysis products from industrial cracking furnaces are commonly quenched indirectly in transfer line heat exchangers (TLX). To assess the performance of a TLX for a high severity furnace, a rigorous computer simulation of a TLX tube has been developed. The primary objective was to determine whether this method of indirect quenching can provide the extremely small quench times required for fast ultrapyrolysis reactions. Results indicate that extremely small quench times of approximately 10–15 ms can be achieved, typically dropping the temperature from 1100 to 900K. The model takes into account the effect of the thermal entrance region on heat transfer characteristics and can employ either a 10 equation molecular reaction scheme or an 80 equation radical reaction scheme for propane pyrolysis. The effects of adjusting the main process variables and of coke deposition on quenching performance are also discussed.
The effects of surface active agents on jet breakup in liquid‐liquid systems
Authors: Skelland A. H. P. , Walker Perry G.
Published: March 2009

An experimental study has been made of the effects of anionic, cationic and nonionic surface active agents on jet length, jet contraction and drop size resulting from the formation and breakup of liquid jets in another immiscible liquid, while undergoing mass transfer.

Correlations previously established for uncontaminated systems with various rates of mass transfer successfully fitted the present data, when used with the diminished value of interfacial tension caused by the surfactant. Variables included nozzle size, flow rate, and type and concentration of surfactant. Data were obtained from measurements on over 3,000 drops, plus jet lengths and jet diameters from 501 photographs.
Minimum tank volumes for CFST bioreactors in series
Authors: Hill Gordon A. , Robinson Campbell W.
Published: March 2009

The primary reactor type currently used in the production of microorganisms or microbial products is the stirred tank reactor (STR). If operated on a continuous flow basis (CFSTR) they become similar in performance to the primary reactor configuration used in most of the chemical industry.

In this work, microbial kinetics are considered in the design of CFSTRs in series. An equation is derived to predict the minimum possible total residence time to achieve any desired substrate conversion. The equation permits the use of a wide variety of growth kinetic models and is applied here to Monod, substrate inhibition and product inhibition cases. For the majority of cases, it is found that three optimally designed CFSTRs in series provide close to the minimum possible residence time for any desired substrate conversion.

A comparison to the use of a PFR is made for cases of both no‐recycle and biomass recycle to the CFSTR train. It is found that three CFSTRs, which are not equi‐volume, provide the same required total mean residence time as a PFR for Monod kinetics, but are significantly superior (i.e., less total volume required) to a PFR for substrate‐inhibited growth.
Letter to the editor: Re: Can. J. Chem. Eng. 66, No. 4, 703; Book Reviews. Editor, Can. J. Chem. Eng.
Authors: Habashi F.
Published: March 2009

Re: Can. J. Chem. Eng. 66, No. 4, 703; Book Reviews. Editor, Can. J. Chem. Eng.
Explicit forms for the calculation of heat and momentum transfer coefficients for vapour condensation on surfaces of various forms
Authors: de Souza‐Santos Marcio L.
Published: March 2009

A relatively simple method to calculate the heat and momentum transfer coefficients for the laminar condensation of pure vapours on surfaces of various forms is presented.

It can be applied generally to surfaces having a variety of geometrical forms. Examples of such applications are presented for the cases of: plane and exponential curved plate profiles, horizontal cylinders, sinusoidal plates and rotating discs and cones.

The mathematical treatment leads to explicit expressions for the parameters of the process, among them the heat transfer coefficients. It considers the effects of film acceleration and energy convection.

It must be stressed that the method is not intended to bring more precision than existing methods which take into account the mentioned effects, but is proposed as a generalized procedure for geometrical surface forms and also to speed the calculations for complicated condensation surface geometries. A guide for equipment designers is also provided.
Control of crystal size distribution in a batch cooling crystallizer
Authors: Rohani Sohrab , Tavare N. S. , Garside John
Published: March 2009

A control scheme for crystal size distribution (CSD) in a batch crystallizer, based on indirect measurement of fines suspension density and manipulation of fines dissolving rate, is proposed and implemented on a 27 L laboratory batch cooling crystallizer using the potash alum‐water system. The measured variable was a temperature difference related to the fines suspension density detected by a new fines sampling/suspension density measuring device proposed by Rohani and Paine (1987). Servo‐control of the fines suspension density was achieved using a conventional PI control mode. Two different cooling policies, namely, linear cooling and isothermal operation were examined and improvement in the final CSD was observed in both cases. The weight‐mean crystal size and the coefficient of variation of the end product showed a maximum improvement (larger mean size and smaller coefficient of variation) of 80% and 31% over the uncontrolled experiments, respectively. The weight fraction of fines (smaller than 150 μm) in the end product was decreased by a maximum of 99% over the uncontrolled run. Higher overall rates of fines dissolution led to a more uniform product with a larger weight‐mean crystal size at the expense of a small reduction in the rate of solids make.
The effect of the level of micromixing on the optimal design of cstr's performing michaëlis‐menten reactions
Authors: Malcata F. Xavier
Published: March 2009

An analytical formula for the calculation of the substrate conversion under complete segregation conditions in a CSTR performing a biochemical reaction following Michaëlis‐Menten kinetics is obtained. The errors on the expected conversion arising from using an optimal reactor design based on the assumption of complete micromixing conditions are discussed. Methods for the determination of the optimal reactor size profile for a series of CSTR's under complete segregation conditions are reported, using the minimum of the overall space time as the objective function.
Scale‐up of liquid‐liquid dispersions in stirred tanks
Authors: Okufi S. , De Ortiz E. S. Perez , Sawistowski H.
Published: March 2009

A study of local drop size, drop size distribution and holdup fraction was conducted for liquid‐liquid dispersions in three geometrically similar stirred tanks of standard configuration over a range of stirrer speeds and dispersed phase volume fractions. The tanks had diameter ratios 1:2:4, the smallest diameter being 11 cm. Two liquid‐liquid systems were used: n‐heptane‐water and n‐heptane containing different concentrations of di‐(2‐ethylhexyl) phosphoric acid dispersed in an aqueous sulphate solution. No significant local variations of the three parameters investigated were observed at constant stirrer speed and constant dispersed phase volume fraction. Measurements in the three tanks indicated that the rule of equal impeller tip speed provides the best scale‐up criterion for equal interfacial areas per unit volume of dispersion. A correlation was also proposed for the Sauter mean diameter.
The effect of the droplet volume and hydrocarbon chain length on the detachment force in the sulphur/hydrocarbon drop/sulphur system
Authors: Bialopiotrowicz Tomasz , Janczuk Bronislaw
Published: March 2009

Using a device constructed in our laboratory, measurements of the detachment force of a small sulphur plate from hydrocarbon drops of various volumes located on a large sulphur plate were carried out. Eleven aliphatic hydrocarbons in the series from n‐hexane to n‐hexadecane were used. Using the literature data for hydrocarbon‐water interfacial tensions and the contact angles for the system sulphur/hydrocarbon drop/water, the detachment force was also calculated from the Laplace equation. On the basis of the measured results it was found that the detachment force depends on the hydrocarbon drop volume and the type of hydrocarbon and that in the many cases there is a good agreement between the measured and calculated values of the detachment force. It was also found that there is a stepwise relationship between the detachment force and the number of carbon atoms in the hydrocarbon molecule.
Removal of fine particles from aqueous medium by flotation: Sodium dodecylbenzenesulfonate‐barium sulfate system
Authors: Kubota Katsuyuki , Harima Toshihiro , Hayashi Shinya
Published: March 2009

Insoluble barium sulfate particles were removed from water by a batch flotation technique using an anionic surfactant as a frother and collector. The measured particle concentrations are presented as a function of the elapsed time and compared with values predicted by a simple hydrodynamic collision model. The model predictions were in reasonable qualitative agreement with the experimental results. However, the attachment efficiency observed was found to be much smaller than unity, suggesting that an electrical repulsive force may affect the flotability. Accordingly, electrical mobilities for the air bubbles and the particles were measured by the electrophoresis method, and the energy barrier between the particles and the bubble surfaces was found to be relatively large.
Structure des écoulements dans une cuve à fond bombé agitée par une turbine de rushton
Authors: Magni F. , Costes J. , Bertrand J. , Couderc J. P.
Published: March 2009

La structure des écoulements générés par une turbine de Rushton est étudiée dans une cuve chicanée à fond bombé. contenant un volume d'eau de 50 litres. La technique de mesure utilisée est la vélocimétrie Doppler à laser.

Pour une vitesse de rotation de 65 tours par minute, les composantes radiale, tangentielle et axiale de la vitesse moyenne et de la moyenne quadratique des fluctuations de vitesse ont été déterminées en divers points du plan médian entre deux chicanes et dans deux plans verticaux voisins des chicanes. Les débits de circulation radiale, axiale et tangentiellc ont été calculés.

L'ensemble de ces résultats a permis de determiner trés finement les caractéristiques des écoulements moyen et fluctuant dans tout le volume de la cuve et de précker les influences des chicanes et du fond bombé.
Investigation of interfacial area and void fraction in upward, cocurrent gas‐liquid flow
Authors: Dejesus J. M. , Kawaji M.
Published: March 2009

Interfacial area was measured in cocurrent, gas‐liquid upward flow through a vertical, 2.54 cm I.D. and 2.67 m long tube by absorption of CO2 diluted in air into aqueous sodium hydroxide solution. Void fraction and pressure drop were also measured for superficial liquid velocities up to 1.3 m/s. Although the interfacial area exhibited a maximum and minimum with increasing superficial gas velocities at relatively high liquid flow rates as in previous experiments, several significant differences were found. Since the dissipation parameters proposed in the past to correlate interfacial area were found to be less than satisfactory, a new empirical relation is proposed, which can correlate most of the present data within ± 20%.
Performance of thermal energy storage unit using CaCl2‐NH3 system mixed with Ti
Authors: Yamamoto Hideki , Sanga Seiji , Tokunaga Junji , Sakamoto Yuuki
Published: March 2009

In order to develop an energy storage system using the reaction of solid CaCl2 with ammonia gas, various properties such as volume expansion of CaCl2 with ammoniation, activity of the chemical reaction for repeated cycles and influence of a metal additive on the heat transfer rate of the ammoniated salt were studied experimentally. The maximum volume after the reaction was 14–16 times of the ideal volume of CaCl2. No deactivation was observed on repeated cycles. The heat transfer rate of ammoniated salts (CaCl2 · nNH3) was improved by adding the metal, titanium. The time required for ammoniation of CaCl2 mixed with Ti was 10–30% shorter than for CaCl2 alone. Similar results were obtained by repeating the cycles of ammoniation and deammoniation.
Types of dispersion in agitated liquid‐liquid systems
Authors: Kato Satoru , Nakayama Eiichi , Kawasaki Junjiro
Published: March 2009

This paper describes phase inversion phenomena in stirred vessels. In particular, the effects of mechanical operating‐parameters on dispersion types were investigated. It was found that when the impeller stirring speed was lower than 400 rpm, the aqueous phase became continuous, while when it was higher than 1050 rpm, the phase which had the higher viscosity became dispersed. Surface active agents have strong effects on phase inversion phenomena.
Gas liquid contacting in reciprocating plate columns: I. hydrodynamics
Authors: Gomaa H. G. , Landau J. , Al Taweel A. M.
Published: March 2009

The hydrodynamic characteristics of a 10‐cm reciprocating plate column used for counter‐current gas‐liquid contacting was investigated. The values of gas holdup, interfacial area and maximum throughputs achievable in this unit put it in a favourable position in comparison with other types of contactors.
Liquid‐liquid extraction in a reciprocating screen plate column
Authors: Chen B. H. , Liu C. H.
Published: March 2009

A novel reciprocating‐plate liquid‐liquid extraction column is proposed. It features a simple design that utilizes as the plates mesh screens with a fractional free area larger than 64%.

A hydrodynamic and mass transfer study of the column was carried out in which the existence of a uniform liquid‐liquid dispersion throughout the column at relatively low speeds of plate reciprocation was confirmed. Experimental results show that in comparison with other reciprocating columns, the present column has these desirable qualities: (1) large dispersed phase holdup and overall mass transfer coefficient, (2) low power requirements, (3) high flow capacity.

A correlation of the dispersed phase holdup data based on slip and drop characteristic velocities is presented. The drop characteristic velocity for the screen plate column is empirically related to the power dissipation rate and system properties.

On propose une nouvelle colonne d'extraction liquide‐liquide munie de plateaux réciproques. Il s'agit d'une conception simple qui utilise comme plateaux des tamis à mailles avec une zone libre fractionnelle supérieure à 64%.