bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of temperature peak attenuation by catalyst dilution in a tubular packed‐bed reactor
Authors: Danziger D. , Popović D. , Schulz‐Ekloff G.
Published: March 2009

Temperature peak attenuation is an important problem for safe process control. Simulations of the axial temperature and product progression in stationary ammonia synthesis with different axial catalyst dilutions have been carried out. It is demonstrated that the requirement of temperature peak attenuation together with a maximum product yield can be met by an optimal catalyst dilution profile at the entrance of the bed.
Dispersed phase holdup and drop size distributions in reciprocating plate columns
Authors: Rao N. V. Rama , Srinivas N. S. , Varma Y. B. G.
Published: March 2009

The paper covers an experimental and theoretical investigation of the dispersed phase holdup and drop size distribution for gas‐liquid and liquid‐liquid counter‐current flow in reciprocating plate columns provided with plates having small hole size and free area. The response of the reciprocating plate column is similar to that of liquid‐pulsed columns exhibiting mixer‐settler and emulsion regions. The dispersed phase holdup depends on the dispersed phase flow rate, the vibrating speed of the plate stack, the plate geometry and the number of plates: it was found to be minimum at the transition between the mixer‐settler and emulsion regions.

The dispersed phase holdup is modeled incorporating apparent interstitial liquid velocity and the slip velocity to account for the non‐descriptive flow pattern between the phases.

The drop size distribution is satisfactorily represented on a Rosin–Rammler Chart. Sauter mean diameter, calculated from the distributions, indicated an advantage in the drop size‐power consumption relation when plates having small hole size and free area are used.

Equipment used for fluid‐fluid contacting is often broadly classified as either stagewise or differential contactors. The classification is further sub‐divided as gravity, mechanically‐agitated and pulse‐agitated, depending on the method adopted for interdispersing the phases. Pulse‐agitation involves the use of either reciprocating perforated plates moving vertically up and down the column, or pulsing a phase hydraulically keeping the internal structure of the column stationary.

The literature on reciprocating plate columns (RPC) primarily is concerned with the study of liquid‐liquid systems using perforated plates having large hole size and free area. This paper presents the dispersed phase holdup and drop size distributions for gas‐liquid and liquid‐liquid systems in reciprocating plate columns with small perforation diameter and free area for the plate.
Modelling of resonant behavior during forced cycling of catalytic reactors
Authors: Lynch David T.
Published: March 2009

A model, based on a Langmuir‐Hinshelwood type mechanism, for the oxidation of carbon monoxide on a platinum catalyst is presented. This model is used to explain resonant behavior which has been observed during forced feed composition cycling of catalytic reactors. This model further predicts that catalytic reactions can display pathological behavior under certain conditions of feed cycling in agreement with experimental observations.
Physical effects on Fischer–tropsch synthesis over composite Ru catalysts
Authors: Yang C.‐H. , Goodwin J. G.
Published: March 2009

Fischer–Tropsch synthesis was studied over composite catalysts formed by adding SiO2 to Ru/Al2O3 and to Ru/TiO2. The two Ru primary catalysts alone had reasonably similar catalytic properties for this synthesis. It was found that the presence of excess amounts of SiO2 with the primary Ru catalysts can produce significant changes in conversion and product selectivity, depending upon the support used. It is suggested that the effects produced by the physical presence of this inert material are due to a combination of primary catalyst activity, product selectivities, possible secondary reactions, heat and mass transfer effects, and reaction conditions. These results emphasize the importance of considering both physical and chemical effects when developing any composite catalyst mechanism.
An experimental laboratory fixed bed study on the atmospheric pressure gasification of poplar bark with steam
Authors: Kumar Ashwani , Mann R. S.
Published: March 2009

An experimental study has been made of the gasification of poplar bark particles exposed to a helium/water vapor atmosphere in a fixed‐bed reactor at 873–973 K. with and without silica catalyst. The effect of temperature on gas yields, calorific value and carbon conversion was evaluated for the pyrolytic conversion and steam‐char gasification stages. The kinetics of the production of various gases in catalytic steam‐char reaction has been studied.
Solubilities of gaseous butadiene and butene‐2 in possible extractive distillation solvents
Authors: Asatani Haruki , Hayduk Walter
Published: March 2009

Solubilities of 1,3‐butadiene and trans‐2‐butene are reported for a pressure of 101.325 kPa and temperatures ranging from 278 to 323 K in the solvents carbon disulfide, acetic acid, acetone, dimethyl formamide, dimethyl acetamide, and ethyl acetate. The solvents were chosen to attempt to elucidate the complex molecular interactions that occur with certain reactive gases and some commercial extractive distillation, as well as other solvents.
Interfacial tension behavior of athabasca bitumen/aqueous surfactant systems
Authors: Isaacs E. E. , Smolek K. F.
Published: March 2009

The spinning drop method was used to measure the interfacial tension of Athabasca bitumen in contact with an aqueous phase (D2O); variables included temperature, salinity, alkalinity, surfactant type (TRS 10–80, Suntech 5, sodium dodecyl sulfate), surfactant concentration, isopropyl alcohol concentration, bitumen drop size and age of interface. In the absence of surfactant, the bitumen/aqueous interfacial tension decreased with increasing temperature and salinity. Bitumen drops contacting alkaline medium exhibited interfacial tension minima below a pOH of three. In the presence of surfactant, the interfacial tension behavior was often complex. The interfacial tension‐concentration plot for Suntech 5 surfactant exhibited two CMC type discontinuities. Low interfacial tension (<0.01 mN m−1) was observed only in the presence of added electrolyte. Interfacial tension values were sensitive to the age of surfactant preparation and volume ratio of the oleic‐to‐aqueous phases. The interfacial tension of the bitumen/brine‐TRS 10–80 system increased upon addition of isopropyl alcohol. An increase in temperature required an increase in salinity to maintain a constant low interfacial tension. The experimental results are discussed in terms of changes in the structure of the amphiphile at the bitumen/aqueous interface.
Measurement of enthalpies of mixing in gaseous phase for the binary system carbon dioxide – hydrogen sulphide by an isothermal flow calorimeter
Authors: Barry Alpha O. , Kaliaguine Serge C. , Ramalho Rubens S.
Published: March 2009

Enthalpies of mixing for the binary system carbon dioxide – hydrogen sulphide were measured by means of an isothermal flow calorimeter at temperatures of 293.15. 305.15 and 313.15 K. For the first isotherm, excess enthalpy measurements were made at pressures of 0.507, 1.013 and 1.419 MPa. For the last two isotherms, these measurements were performed at pressures of 0.507, 1.013 and 1.520 MPa. The experimental data were treated by the same techniques described for the systems previously studied (Barry et al., 1982a, 1982b, 1982c).

Two types of binary interaction coefficients kij have been utilized for the prediction of experimental data from equations of state: coefficients kij independent of temperature and pressure, and kij's adjusted as function of temperature and pressure. A better prediction of the excess enthalpy experimental data was obtained from the latter series of binary interaction coefficients.
Estimation of the liquid‐phase enthalpy of mixing for the binary mixture 1,3 dioxolane‐water
Authors: Castellari Carlo , Francesconi Romolo , Bubani Bianca , Comelli Fabio
Published: March 2009

The liquid‐phase enthalpy of mixing δHm of the binary system 1,3 dioxolane‐water was calculated from existing isobaric liquid‐vapor equilibrium data.

The liquid‐vapor data were correlated by the equations of Margules (with three parameters), Redlich‐Kister (with four and five parameters), Wilson, NRTL and LEMF in order to obtain the unknown parameters. From the corresponding analytical expressions for GE the values of δHm were calculated and compared with reported experimental values. Only the Redlich‐Kister expressions provided calculated δHm curves showing the inversion of sign typical of the experimental curves, whereas the Wilson expression gave the best agreement between the calculated and the experimental values of the heat of mixing.

On a calculé l'enthalpie de mélange en phase liquide δHm du système binaire, 1,3 dioxolane‐eau, à partir des données isobares d'équilibre liquide‐vapeur.
Isobutane production with a catalytic reformer pretreater
Authors: Yan T. Y.
Published: March 2009

For some refineries, production of isobutane is economically viable; for others, isobutane self‐sufficiency is strategically important. However, a process unit specifically for isobutane production often is not justified.

A process has been developed to use an existing unit to produce isobutane on demand. In this process, the reformer pretreater is filled with a special catalyst with a high selectivity for desulfurization over hydrocracking. It can pretreat the reformer feed to low sulfur levels at low temperatures without significant hydrocracking; this selectivity can be further enhanced by temporary poisoning with nitrogen compounds.

The catalyst is also active for hydrocracking so that, when isobutane is in demand, a moderate increase in reactor temperature allows the production of butanes at a high iso‐to‐normal ratio while maintaining desulfurization. Preliminary tests indicate that catalyst stability appears excellent.
The minimum spouting velocity in conical beds
Authors: Kmieć Andrzej
Published: March 2009

A theoretical model, describing the equilibrium of forces resulting from gas flow resistance, bed weight and internal solid friction at the point of the minimum spouting velocity, is proposed.

An equation for predicting the minium spouting flow rate has been developed and verified by the experimental data obtained in 8 columns with diameters varying from 0.09 m to 0.9 m.
Studies on the solid circulation rate and gas bypassing in spouted fluid‐bed with a draft tube
Authors: Yang Wen‐Ching , Keairns Dale L.
Published: March 2009

Experiments were performed in a 28.6 cm diameter transparent semicircular vessel with a 9.6 cm diameter draft tube using polyethylene beads (ρs = 0.91 g/cm3) and hollow epoxy spheres (ρs = 0.21 g/cm3) as the bed material to study the effect of operating conditions, the distributor plate design, and the draft tube inlet configurations on the solid circulation rate and the gas distribution between the downcomer and the draft tube. Solid circulation rate was found to be strongly affected by the design configuration at the bottom of the draft tube and the downcomer, which provided different gas bypassing characteristics and resulted in different amount of aeration in the downcomer region.
Studies of spouted beds with small outlet‐inlet cross‐section ratios
Authors: Dolidovich A. F. , Efremtsev V. S.
Published: March 2009

An experimental study of the hydrodynamics, structure, mixing and interphase heat transfer of spouted beds of fine dispersed materials in conic‐cylindrical columns with the small outlet‐to‐inlet cross‐section ratio D/D0 ≤ 3 has been made by different methods. The effect of design and operation parameters on the shape, sizes and stability of a central core, the solid phase concentration variation in the core and annulus, the circulation rate, entrainment and heat transfer in the columns with D = 100 mm have been explored. Empirical correlations have been suggested for calculating pressure drops across such beds under the developed spouting conditions and for effective gas‐to‐solid phase heat transfer coefficients.
Thick coatings by thermo‐chemical deposition in spouted beds
Authors: Piccinini Norberto , Rovero Giorgio
Published: March 2009

Spouted beds are an established way of coating nuclear fuel microspheres with pyrolytic carbon or silicon carbide by high‐temperature thermochemical reactions. In recent years, similar coatings have aroused particular interest as bio‐compatible materials. This paper describes the differences between these two applications, and the changes that must be made to the coating process and furnace to control both the overall surface of the bed material and its increase in volume. It is shown that a satisfactory control can be achieved by continuous feeding of small particles, followed by the continuous withdrawal of variously coated particles. Experiments on two columns with internal diameter of 0.08 and 0.14 m, respectively, showed that segregation phenomena may occur, depending on the flow dynamics, and that the way in which a steady state is brought about will depend on the position of the discharge pipe in the bed.

Les lits “spoutés” constituent un moyen courant pour recouvrir des microsphères de combustible nucléaire de carbone pyrolytique ou de carbure de silicum, en employant des réactions thermochimiques à température élevée. Durant les dernières années, les recouvrements du type précité ont suscité un intérět particulier en raison de leur biocompatibilité.
Comparison of coal gasification in fluidized and spouted beds
Authors: Watkinson A. P. , Cheng G. , Prakash C. B.
Published: March 2009

Two sub‐bituminous coals, a bituminous coal and a reject coal of 55% ash were gasified with steam and air in a 0.31‐m dia. reactor operated in the fluidized and spouted bed modes. Inert beds of 1.1 mm dia. Ottawa sand and 2.1 mm dia. gravel provided stable fluidization and spouting respectively, at superficial velocities in the range 1.3–1.6 m/s. Coals of 1.19–3.36 mm diameter were fed to the gasifier at rates up to 45 kg/h and a range of air/coal ratios. For a given coal, results in the two systems were basically similar, although differences in gas heating value, gas yield and thermal efficiency were noted for some coals.
Estimation of liquid film mass transfer coefficients for randomly packed absorption columns
Authors: Au‐Yeung Patrick H. , Ponter Anthony B.
Published: March 2009

Empirical and theoretical correlations, published since 1940 are reported which predict liquid film mass transfer coefficients in packed columns. Brief comments on the usefulness of the equations are given together with the range of operating variables, where available. Dimensional constants in the empirical correlations have been recalculated for the cases where the original values were not in SI units.
Anodic oxidation of phenolics found in coal conversion effluents
Authors: Chettiar M. , Watkinson A. P.
Published: March 2009

Solutions of phenol, o‐cresol, p‐cresol, 2,3‐xylcnol, 3,4‐xylenol, resorcinol, and catechol at concentrations below I g/L were oxidized at constant current on a packed bed lead dioxide electrode with electrolyte recirculation. The effects of applied current and initial concentration on the extent of oxidation with time were explored. The observed ranking in ease of oxidation was phenol > 2,3‐xylenol > resorcinol > p‐cresol > 3,4‐xylenol > o‐cresol. Although the phenolics were largely destroyed, organic degradation products of the quinone and hydroquinone type remained in solution. A mixture of five monohydric phenols showed 96% destruction of phenolics, a 50% reduction in B.O.D. but a reduction in total organic carbon of only 22%.
Particle agglomeration and capture as a result of synergism between inertial impaction and eddy diffusion
Authors: Douglas P. L. , Dullien F. A. L. , Spink D. R.
Published: March 2009

Particle capture experiments conducted in turbulent cross flow with various aerosols involving liquid and/or solid particulates have resulted in collection efficiencies which are in excess of the values predicted by the various known models of particle capture, i.e., inertial impaction, interception and Brownian diffusion.

In one type of experiment the turbulent air stream, carrying submicron dust particles, is flowing past a cylindrical collector (such as a piece of wire) with its axis orientated perpendicular to the direction of flow. Collecting efficiencies ranging up to about 20% have been found under conditions where the conventional models of particle capture predict practically zero collection efficiencies.

In another type of experiment involving injecting a fog (2–80 μm diameter water droplets) into the dusty gas stream carrying submicron size dust particles which subsequently enters a slow turning fan. While passing through the fan, the fog agglomerates into raindrops while scavenging most of the dust particles. For example, a 0.8 μm median particle size aluminum silicate pigment was collected with 97–99.5% efficiency, the exact value depending on the operating conditions.

Theoretical analysis of these phenomena may be based on the idea of synergism involving inertial impaction and eddy diffusion: the smaller dust particles/drops are captured by the larger drops in the fan and the dust particles are captured by the wires because (a) there is a significant relative velocity between them and (b) because the particles undergo eddy diffusion.
Natural convection mass transfer to nonspherical objects at high rayleigh number
Authors: Weber M. E. , Astrauskas P. , Petsalis S.
Published: March 2009

Natural convection mass transfer measurements were made by the electrochemical method for spheres and eight nonspherical shapes in several orientations. Using a characteristic length which is sensitive to orientation, a natural convection correlation is proposed for objects of any shape having sphericities larger than 0.6.
Measurement of large gasndashliquid interfacial areas
Authors: Al Taweel A. M. , Divakarla R. , Gomaa H. G.
Published: March 2009

The light attenuation technique has been modified to expand the range of its applicability up to AL values of 460. This has been accomplished through the use of a laser as the source of monochromatic collimated light, and a very sensitive low‐bias picoammeter.

The data obtained using the photographic technique were found to agree reasonably well with those from light attenuation.
Bubble measurement in three‐phase fluidized beds using a u‐shaped optical fiber
Authors: De Lasa H. , Lee S. L. P. , Bergougnou M. A.
Published: March 2009

A photometric technique is being developed to study bubble behaviour in three‐phase fluidized beds constituted by fine particles. A custom made U‐shaped single core silica fiber (400 μm diameter) is used as the bubble sensor. A helium‐neon laser beam is introduced at one end of the U probe and the variation of the light intensity, occurring when a gas bubble contacts the sensor, is detected at the other end of the fiber. The velocity and axial length (cord) of the bubbles were measured by four such probes in a two dimensional bed. This technique could be applied to study the bubble behaviour and to provide experimental data for estimating the performance of reactors with severe operating conditions of high temperature and pressure.
Isokinetic probe sampling from slurry pipelines
Authors: Nasr‐El‐Din H. , Shook C. A. , Esmail M. N.
Published: March 2009

A theoretical and experimental study of the errors arising in sampling through probes projecting into the flow has been conducted. Water–sand slurries with particles of surface‐mean diameter between 0.165 and 0.72 mm were considered. Theoretical predictions were performed assuming the mixture could be described by the axisymmetric potential flow relationship. Satisfactory agreement in the important intermediate K value region was achieved for tapered or thin‐walled probes. However, significant errors arise when thick‐walled blunt probes are used.
Studies on chains of bubbles rising through quiescent liquid
Authors: Miyahara Toshiro , Kaseno Satoru , Takahashi Teruo
Published: March 2009

The liquid velocity profile induced by a chain of bubbles is studied theoretically and a comparison with measurements is made. The wake velocity and the bubble shape involved in the theoretical development are considered based on the wake theory and the previous empirical relation for single bubbles, respectively.

The shape and wake volume of chain bubbles can be treated in the same manner as those of single bubbles by using relative velocity. As a result, using the previous results of the drag coefficient and shape of single bubbles enables the prediction of the rising velocity of chain bubbles.
Gas absorption in laminar falling films of pseudoplastic liquids
Authors: Hikita H. , Ishimi K. , Hara M. , Matsunami T.
Published: March 2009

Gas absorption into laminar falling films of power‐law liquids was studied theoretically and experimentally. The convective‐diffusion equation was solved by the method of separation of variables and the analytical solution for the average Sherwood number was obtained as a function of the Graetz number and the power‐law index of the liquid. Experiments were carried out on the absorption of pure carbon dioxide, hydrogen and helium into aqueous kaolin slurries by using a long wetted‐wall column and the average absorption rates were measured as a function of the mass flow rate of the liquid. The experimental results were in good agreement with the theoretical predictions.
A classification of fischer–tropsch synthesis product distributions
Authors: Egiebor N. O. , Ungar K. R. , Wojciechowski B. W.
Published: March 2009

Two types of product distributions in Fischer–Tropsch synthesis have been observed; the “classical” distribution where successive carbon numbers contain homologous groups of compounds and the “non‐classical” where the product spectrum deviates from the above picture. It is proposed that the non‐classical distributions arise on bifunctional catalysts on which primary synthesis products are rapidly converted to isomeric secondary products.
Errors associated with the measurement of dew‐point loci for wide boiling mixtures
Authors: Veeranna Doddipatla , Husain Asghar
Published: March 2009

The normal practice to measure the dew‐point locus of a mixture is to use a static phase equilibrium still. In this technique, the condensate needed to observe cloud formation completely changes the composition of the mixture, leading to inaccurate dew‐point measurements. A careful analysis is made in this work to show the extent of the error in the dew‐point measurement using the static phase equilibrium still.
Grid leakage (weeping and dumping) in a pilot plant size gas fluidized bed
Authors: Briens C. L. , Bergougnou M. A.
Published: March 2009

Substantial grid leakage in large industrial fluidized beds is highly undesirable because it can lead, among other things, to grid erosion or plugging. Experiments have been carried out to study grid leakage using a cracking catalyst (arithmetic mean diameter 65 μm) in a 0.6 m diameter column. The flow pattern under the grid was charted with a hot wire anemometer. Micro‐isokinetic probes were developed to study the particle flux returning from the windbox towards the grid. Particles were sucked in isokinetically, recovered in a filter, weighed and analyzed for particle size in a Coulter counter. Upward particle fluxes at the grid were determined by extrapolation of the flux at various distances below the grid. Grid leakage was studied for grids of various geometries which had holes of 1.27 cm diameter. Various measurement methods, a model for re‐entrainment and correlations are given.
A new lubricants extraction process
Authors: Sankey B. M.
Published: March 2009

Development of a new process for the solvent extraction of lubricating oils, known as EXOL N, is described. The selection of N‐methyl‐2‐pyrrolidone (NMP) as solvent, the determination of its relevant properties, and its application through engineering and pilot‐plant studies are reviewed. This EXOL N process is now employed internationally in over a dozen full‐scale lube extraction plants.
Flow patterns for cylinders immersed in an aerated vibrated bed
Authors: Malhotra K. , Mujumdar A. S.
Published: March 2009

Pressure drop measurements and results of an extensive flow visualization study to examine the particle‐free air gap formation around horizontal, rigidly‐mounted circular cylinders in a two dimensional vibrated bed, are presented. Effects of particle size and surface stickiness as well as other key operating parameters viz. aeration rate and vibrational frequency were examined for single as well as multiple cylinder configurations in staggered and in‐line arrangements.
Multidimensional heat, mass and flow phenomena in gas stirred reactors
Authors: Salcudean M. , Lai K. Y. M. , Guthrie R. I. L.
Published: March 2009

Computations are presented for multi‐dimensional flows in gas‐stirred liquids contained in vertical cylindrical vessels. Mass, momentum, energy and concentration equations were solved for the buoyancy driven transient flows under investigation. Turbulence was simultated by using zero order and differential models of turbulence. The use of convective and diffusive time scales was analyzed. Reasonable agreement with available experimental data was observed.
Pyrolysis of western canadian coals in a spouted bed
Authors: Jarallah A. , Watkinson A. P.
Published: March 2009

Coal pyrolysis has been studied to determine conditions for maximum liquid yields from some Western Canadian coals. Gas, tar and char yields were determined for four coals in a 12.8 cm dia. reactor. A characteristic temperature for maximum tar yield existed for each coal at a fixed feed rate and particle size. A steady increase in tar yield was found as the average coal particle size was reduced from 2.28 to 0.65 mm. Composition of gas, and ultimate analyses of tar and char are presented as a function of operating temperature. A simple first‐order devolatilization model adequately describes the effects of coal feed rate, reaction time, and temperature on the yield of volatiles, but is insufficient to describe particle size effects.
Catalytic cracking and skeletal isomerization of n‐hexenes on HY zeolite
Authors: Abbot J. , Wojciechowski B. W.
Published: March 2009

The catalytic cracking and skeletal isomerization of n‐hexenes on 80/100 mesh HY zeolite has been studied in the temperature range 350–405°C, and compared with results previously obtained on ZSM‐5 zeolites.

Species with less than three carbon atoms were not observed as primary cracking products, with traces of ethylene formed only as a secondary product. Although propylene and propane may be formed partially by monomolecular cracking of n‐hexenes, the dominant cracking process is bimolecular. Dimerization, followed by disproportionation gives stable C3, C4 and C5 species, in addition to C9, C8 and C7 fragments. The probability of these larger fragments undergoing further cracking before desorption increases with temperature, but is significantly less than found on ZSM‐5 zeolites.

The main products of skeletal isomerization were monomethylpentenes, with those isomers which can originate from tertiary carbonium ions dominant. Dimethylbutenes were formed mainly as secondary products.

The rate of the dimerization‐cracking process in which two n‐hexene species participate is ⋍ six times slower than the reaction involving a monomethylpentene species and a linear hexene. The increase in the rate of the latter process with respect to the former is reduced on ZSM‐5, and this can be attributed to the narrower pore size within this zeolite.

In contrast to ZSM‐5, there is significant formation of alicyclics, paraffins and aromatic species. The residual coke was found to be considerably poorer in hydrogen content than comparable material formed on ZSM‐5.
The dissolution of activated titanium slag in dilute sulfuric acid
Authors: Toromanoff Ivo , Habashi Fathi
Published: March 2009

Finely ground titanium slag (–400 mesh) dissolves slowly in dilute H2SO4 (2–10 mol/L) in the temperature range 70–110°C, but attrition ground slag dissolves much faster under similar conditions. The process is strongly dependent on the speed of agitation in the region 345–1035 rpm, and has an activation energy of 28 kJ/mole TiO2, thus suggesting that the dissolution is controlled by diffusion through the boundary layer.
Particle residence times in the continuous spouting of mixtures
Authors: Cook H. H. , Bridgwater J.
Published: March 2009

A magnetic labelling technique has been used to examine particle residence time distributions in a continuous spouted bed. For a single particle species, the nearly perfect mixing observed found by others is confirmed. For a binary particle system, perfect mixing of each component is found, but the mean residence times are not equal. The ratio of mean residence times is found to be dependent on the fountain height and bed depth; the influence of some of the underlying physical mechanisms in the fountain, free surface and outlet regions can be seen.
Simulation of discontinuous population balance equation with integral constraint of growth rate expression
Authors: Chang Rong‐Yeu , Wang Maw‐Ling
Published: March 2009

An effective method based on the concept of continuous characteristics is developed to solve the continuous population equation with integral constraint of growth rate expression. This method can also be extended to solve a general form of a first order partial differential equation. A typical example of a class II MSMPR crystallization process at transient state is modelled and analyzed. The system which possesses originally a discontinuous population density function is transformed into a continuous one by appropriate treatment of the initial condition. The partial differential equation of the continuous population density function is solved by the shifted Legendre polynomials approximation and moments method simultaneously. The original discontinuous population density function is then transformed back from the calculated continuous one by the system characteristics. Very satisfactory computational results are obtained.
The thermal decomposition of granular and fluid soybean lecithins
Authors: Ross Robert A. , Lemay Réjean , Takacs Aniko M.
Published: March 2009

The effect of heat on the decomposition of two grades of soybean lecithin has been examined up to 600°C using differential scanning calorimetry and thermogravimetry. Studies were carried out in both air and argon and a kinetic analysis of the isothermal rates of reaction was attempted. Three principal decomposition stages were distinguished in argon and four in air for a water‐dispersible lecithin typical of the quality of the material used in many industrial applications. Gas chromatography showed that the principal gases evolved from 50 to 600°C in argon from the water‐dispersible lecithin in contact with aluminum surfaces were C1‐C6 hydrocarbons, carbon dioxide, carbon monoxide, water and traces of hydrogen.
Operating behaviour and crystallization mechanism of a sodium sulphate sodium phosphate mixture in a heat storage system
Authors: Fouda A. E. , Capes C. E. , Nakamura M.
Published: March 2009

The operating behaviour of a new salt hydrate mixture in a pilot heat storage unit using direct contact heat exchange has been investigated. The new storage medium is based on diluted Glauber's salt in which the excess water has been replaced by Na2HPO4 ṁ 12H2O as an active participant in the storage process.

Improved heat storage properties have been found with the new salt mixture. Sampling of the salt solution and deposited crystals during operation indicated that alternate independent crystallization of Glauber's salt and of the phosphate salt occurs. Simulations of the crystallization behaviour based on this assumed mechanism are described.
Modelling glucose/fructose isomerization with immobilized glucose isomerase in fixed and fluid bed reactors
Authors: Beck M. , Kiesser T. , Perrier M. , Bauer W.
Published: March 2009

Immobilized glucose isomerase is used to convert glucose to fructose in the production of “High Fructose Corn Syrup (HFCS)” by enzymatic starch hydrolysis. A reactor model was established analogous to heterogeneous catalytic reactor models, taking into account the effects of fluid/particle mass transfer, intraparticle transport, fluid bed expansion, backmixing and reversible kinetics. The kinetic data either for free enzymes and the biocatalyst particles were evaluated using laboratory scale stirred tank reactors. Fixed‐and fluid bed reactor experiments were performed. The comparison of calculated and experimental data show some deviation indicating that the correlations for mass transfer and back‐mixing for complex media, as used here, have to be checked.
Functional design of activated sludge processes with heavy metal inhibition
Authors: Tyagi R. D. , Couillard D. , Villeneuve J. P.
Published: March 2009

Based on a laboratory study of simulated synthetic waste, a kinetic model to describe the inhibitory effects of heavy metals on growth of microorganisms during the activated sludge process was developed. The kinetic equation involves the four biokinetic constants, μm, Ks, Kd and Y, and the two metal inhibition constants, n and c, which are respectively characteristic of a specific wastewater and the metals in question. The two control variables, cell recycle ratio and cell concentration in the recycle stream, can be used to minimize the inhibitory effects without increasing either the volume of the bioreactor or the residence time.
A comparison of the energy and product distribution from biomass gasifiers
Authors: Esplin G. J. , Fung D. P. C. , Hsu C. C.
Published: March 2009

A detailed analyses of the raw producer gas streams generated by a downdraft gasifier and by a fluidized‐bed gasifier are presented and are discussed in terms of raw gas clean‐up considerations and of energy conversion efficiency.

The major gasifier operating parameters such as fuel/air ratio, carbon conversion efficiency, net energy conversion efficiency, and producer gas heating value are then compared between seven operational gasifiers and a computer simulation model of a fluidized‐bed gasifier developed by Queen's University.

It is concluded that the Queen's University model correctly predicts that the fuel/air ratio is the single most important parameter for determining gasifier performance. Downdraft gasifiers exhibit superior energy conversion efficiency and producer gas quality because they utilize a higher fuel/air ratio than do fluidized bed gasifiers.
Hydrodynamique des contacteurs gaz—Liquide du type venturi à émulsion fonctionnant en autoaspiration
Authors: Labit C. , Lebeault J. M. , Zoulalian A. , Besson G.
Published: March 2009

Les contacteurs gaz–liquide du type venturi à émulsion peuvent ětre employés comme élément de transfert d'oxygène dans un bioréacteur.

Pour un fonctionnement du dispositif en autoaspiration, l'extrapolation nécessite la connaissance du débit gazeux autoaspiré en fonction de certains paramètres géométriques et opératoires.

À partir de mesures hydrodynamiques effectuées sur trois Venturis de diamètres de col différents, nous proposons une méthode expérimentale d'extrapolation permettant, pour un venturi de géométrie donnée, de calculer le débit gazeux autoaspiré en fonction du débit liquide recirculé.
Fischer—tropsch studies on a plasma‐sprayed iron catalyst in a tube‐wall reactor
Authors: Kapoor A. , Goyal S. K. , Bakhshi N. N.
Published: March 2009

Conversion of synthesis gas to gaseous and liquid fuels via Fischer–Tropsch (FT) synthesis is becoming increasingly important for future energy needs. Tube‐wall reactors (TWR) are gaining importance for FT synthesis because of simple construction and improved temperature control. In the literature, studies have been reported on the FT synthesis in a TWR using a flame‐sprayed iron catalyst. In the present work, we have examined the effect of temperature (250–275°C), pressure (3.45 × 105 – 6.89 × 105 Pa), exposure velocity (0.61 – 2.44 m3/h of gas at STP/m2 of catalyst superficial area) and feed composition (H2/CO ratio of 2 and 3) on the product yield and selectivity using a plasma‐sprayed iron catalyst in the TWR. The plasma‐sprayed iron catalyst gave slightly lower conversions but showed much higher C5 + product selectivity as compared to the flame‐sprayed catalyst. The product distribution shifted towards higher hydrocarbons at lower temperatures, higher pressures and lower exposure velocities. The product distribution followed Shultz‐Flory relationship and the chain growth probability factor α decreased slightly with increase in temperature. The catalyst also showed good regeneration characteristics.
Cyclic gasification of coal in a moving bed. A bench scale study
Authors: Parés José A. , Rodríquez Daniel A. , Gordon Alfredo L.
Published: March 2009

In an experimental gasifier with 3 kg/h of conversion capacity, studies were made in order to get experimental data on the production of combustible gas from coal by a cyclic gasification process. The material and energy balances and the composition data are presented for 8 runs gasifying coke or coal. An acceptable reproducibility of data was observed. It is possible to obtain a fuel gas with a high calorific value of 10 MJ/m3 using air.
Viscosity of compressed athabasca bitumen
Authors: Mehrotra Anil K. , Svrcek William Y.
Published: March 2009

New data for the effect of pressure and temperature on Athabasca bitumen viscosity are presented. The viscosity data cover a temperature range of 43–120°C and pressures up to 10 MPa. It is shown that the compression of bitumen results in a significant increase in its viscosity but only a small increase in its density. Also presented are correlations that include the effect of pressure and temperature on the viscosity of the bitumen.
Minimum fluidization velocity at elevated temperatures and pressures
Authors: Biń A. K.
Published: March 2009

A procedure based on the Ergun equation to predict the minimum fluidization velocity at elevated temperatures and pressures and for different gaseous fluidizing agents has been discussed and shown to be applicable for practical purposes.
Vented combustion of hydrogen—oxygen—diluent mixtures in a large volume
Authors: Kumar R. K.
Published: March 2009

Combustion of hydrogen‐oxygen‐diluent mixtures was carried out in a 2.3‐m‐diameter sphere with venting to a cylinder of 10.3‐m1 volume. It was found that stoichiometric hydrogen‐oxygen mixtures with helium as the primary diluent led to detonation for all hydrogen concentrations above 20% by volume. Addition of small amounts (5 to 10%) of a secondary diluent such as carbon dioxide or steam suppressed detonation. Carbon dioxide, because of its higher molecular weight, was found to be a better detonation suppressant than steam. Transition to detonation was more difficult to achieve at 100°C than at room temperature.
The mode of combustion of coal in a fluidised bed
Authors: Tomeczek Jerzy , Remarczyk Leonard
Published: March 2009

In this paper investigations of the mode of combustion of coal char in a fluidised bed at temperatures of 973–1173 K are presented. A reactor of 80 mm diameter has been continuously fed with particles of three different size ranges: 0.5–1.0 mm, 1.0–2.0 mm and 2.0–3.0 mm. Carbon loadings were in the range 20–60%. It has been shown that the particles of coal and of partially devolatilized char combust in the form of a shrinking sphere.
Prediction of drop size in rotating disc extractors
Authors: Kumar Arun , Hartland Stanley
Published: March 2009

Based on published drop size data in the absence of mass transfer, two equations for the prediction of drop diameter with a break‐point at disc Reynolds number equal to 50 000 are presented which predict the drop diameter to within 14%. The total range of disc Reynolds number covered is 1200 to 282 000. The same equations may be used when mass transfer occurs if only the preconstants are modified. The ranges of disc Reynolds number covered are 28 000 to 434 000 for transfer from the continuous to the dispersed phase and 9300 to 290 000 for transfer from the dispersed to the continuous phase, the average absolute relative deviation being 11% in both cases.
High resolution measurement of particle velocities in a spouted bed using laser‐doppler anemometry
Authors: Boulos M.I. , Waldie B.
Published: March 2009

A novel means of measuring particle velocities in spouted beds using laser‐doppler anemometry (L.D.A.) is described. L.D.A. is applied mainly in a back‐scatter mode to the spout and fountain of a half‐section bed. The fountain of a three dimensional bed can also be studied. L.D.A. is shown to be a powerful tool for measuring particle velocities in spouted beds. Statistically significant quantities of data are obtained with much higher resolution and in time scales orders of magnitude lower than with previous techniques. Previously unresolved aspects of particle motion, including wall effects in half‐section beds, can be quantified.
Hydrogenation of benzene, mono‐, di‐, and trimethylbenzenes over nickel catalysts supported on porous glass
Authors: Takahashi Takeshige , Yamashita Koji , Kai Takami , Fujiyoshi Issei
Published: March 2009

The hydrogenation of benzene and methyl‐benzenes was performed over a nickel catalyst supported on the porous glass prepared from borosilicate glass with an alumina content ranging from 3% to 5%. The micropore size of the porous glass decreased with increasing alumina content. Although the overall reaction rates of benzene and toluene did not significantly change with the alumina content in the borosilicate glass, the rate of 1,3,5‐trimethylbenzene, which is the bulkiest molecule among the hydrocarbons tested, decreased as the content of the alumina in the support increased. This result indicates that a catalyst support with molecular shape selectivity can be prepared from borosilicate glass containing alumina.
A finite element model of the ventilation pattern inside an industrial building I: Isothermal case
Authors: Tanguy P. A. , Dupuis M.
Published: March 2009

A numerical simulation of the air flow pattern in a building at constant temperature having several openings for air inlet and a chimney is presented. The modelling is based on the use of a Galerkin‐Uzawa finite element method (FEM) with quadratic elements, for reliability and cost‐effectiveness. Four different cases of ventilation conditions are investigated. Numerical results are compared to existing finite difference predictions and experimental data, and exhibit a noteworthy agreement.
A recycle reactor for measuring hydrogen isotope exchange kinetics under vapour phase and trickle bed conditions
Authors: Suppiah S. , Chuang K. T.
Published: March 2009

A recycle reactor system has been developed to measure the activities of catalysts for isotope exchange between hydrogen gas and water vapour. To allow testing of reasonably large quantities of catalysts, the reactor was operated with a high recirculating flow of hydrogen gas passing through a saturator to provide the water vapour required for the reaction. In this mode of operation, only a small spiking gas flow was required as feed compared to the very high feed flow that would be required for once‐through operation. The reactor was also operated as a trickle bed by recirculating the saturator water. By testing catalysts under both vapour and trickle bed modes, it was possible to investigate the effect of trickling water over the catalyst on the catalytic activity.

Kinetic exchange rates under vapour phase operation were calculated from both plug flow and well‐mixed reactor models. The former model was found to be the appropriate one for the ranges of operating conditions investigated. However, for trickle bed operation, the well‐mixed reactor model was found to be the suitable one.

Vapour phase and trickle bed tests done with random bed and structured bed catalysts indicated that the gas phase isotope exchange reaction was not impaired by the presence of liquid water in the reactor.
Noncatalytic conversion of residuum in two‐stage coal liquefaction
Authors: Stiegel G. J. , Lett R. G. , Cillo D. L. , Tischer R. E. , Narain N. K.
Published: March 2009

An experimental investigation was conducted to ascertain the contribution of thermal reactions in the hydroprocessing reactor of two‐stage liquefaction processes. Various solvent/residuum feedstocks were reacted in the absence of a catalyst at temperatures ranging from 655K to 728K. Detailed characterization of the composite and fractionated feedstock and product samples was performed to ascertain the extent of residuum conversion, heteroatom removal, and hydrogen rearrangement. The results showed that hydrogenation of the solvent portion of the feedstock neither enhances residuum conversion nor results in the transfer of hydrogen from the solvent to the residuum. Higher reaction temperatures also had little effect on the reactions involved. These results suggest that the conversion of residuum in the hydroprocessing reactor of two‐stage liquefaction processes must occur catalytically rather than thermally.
Gas hold‐up and mass transfer in a bubble column with viscoelastic fluids
Authors: Moo‐Young M. , Kawase Y.
Published: March 2009

The influence of viscoelasticity on gas hold‐up and the volumetric mass transfer coefficient in a bubble column is discussed and examined experimentally. It was found that the gas hold‐up increased due to an increase in the number of entrapped very small bubbles formed because of the elasticity of the liquid. On the other hand, a decrease in volumetric mass transfer coefficient due to the fluid elasticity was observed. Qualitative effects of an antifoam agent and a draft tube on the performance of the bubble column with viscoelastic fluids were also examined.
The diffusion of liquids in pores
Authors: Ternan Marten
Published: March 2009

An equation for the diffusion of solute molecules in pores filled with liquids has been developed. It has been found to represent the diffusion of a variety of materials, from simple molecules to fractions of petroleum asphaltenes.
The solubility of sulfur dioxide and hydrogen sulfide in associating solvents
Authors: Hayduk W. , Pahlevanzadeh H.
Published: March 2009

The solubilities of SO2 are reported in the solvents N, N‐dimethyl acetamide (DMA), N, N‐dimethyl formamide (DMF), ethyl acetate, acetonitrile, chlorobenzene, methanol, (1,2‐ethanediol) ethylene glycol and acetone for atmospheric pressure and for temperatures ranging from 268 K to 333 K (‐5°C to 60°C). Solubilities of H2S are also reported for the first five of the above‐mentioned solvents and for hexane for similar conditions. These gases and solvents exhibit extreme molecular interactions which are reflected in unusual solubility behavior. This paper is a continuing attempt in providing data and analyses for improving the understanding of gas solubilities in complex gas‐solvent systems. Solubilities expressed as hydrogen‐bonding factors have been found useful in systematically relating gas solubilities in one associating or reacting solvent to another chemically similar solvent. Thus, with a limited amount of data for gas solubilities, it is often possible to predict solubilities even in highly associated or reacting gas‐solvent solutions.
A comparison of the reactivity of various metal oxides with SO3
Authors: Steward F. R. , Karman D. , Kocaefe D.
Published: March 2009

Various metal oxides were reacted with SO3 to compare their reactivity as potential adsorbents of sulfur oxides from flue gas. ZnO was found to be the most reactive of the eleven studied, including two mixtures, a fly ash and a calcined oil shale.

It was found that a scanning electron microscope can be used to assess the reactivity of the oxide based on a rough estimation of internal pore structure from the micrograph of the particles.