bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas holdup and aerated power consumption in mechanically stirred tanks
Authors: Yung C. N. , Wong C. W. , Chang C. L.
Published: March 2009

Gas holdup and mechanical power consumption were measured in aerated aqueous nonelectrolyte and electrolyte systems. The experiments were performed in 0.4 m diameter cylindrical flat‐bottomed and hemispherical‐bottomed tanks. Standard six‐blade turbine (D/T = 0.225, 0.325, 0.45) and four‐blade paddle (D/T = 0.225, 0.325) were used over a wide range of gas sparging rate and power dissipation. A semiempirical correlation for holdup with dimensionless groups, i.e. impeller Weber number, aeration number and ratio of impeller diameter to tank diameter has been developed; however, this correlation did not fit the electrolyte solution data. The power consumption data of both the impeller types and tank bottom types were found to fit satisfactorily the Michel‐Miller correlation with 20% accuracy.
Rheological properties of oil sand bitumens
Authors: Dealy John M.
Published: March 2009

Bitumens extracted from oil sand taken from the Athabasca and Cold Lake regions of Alberta were studied by use of a Mechanical Spectrometer. A heavy crude produced in the Lloydminster area was also studied. Viscosity and first normal stress difference were measured as well as viscoelastic functions. The bitumens are mildly non‐Newtonian in shear and viscoelastic. The behavior is qualitatively similar to that observed in residual asphalts, but it is suggested that the bitumen maltenes form a better solvent for the asphaltenes than in the case with the asphalts. Concentration of solvent, asphaltenes and dispersed water have strong effects on the viscosity. These results are interpreted in terms of molecular aggregation.
Gas chromatographic study of binary diffusion of gases
Authors: Pathak Brajendra K. , Singh Prem C. , Singh Vishwa N.
Published: March 2009

A gas chromatographic study of binary diffusion of gas pairs: H2‐Air, H2‐Ar, H2‐O2 and H2‐N2 was conducted at 30°C in a gas chromatograph GCHF‐18 (East Germany) using Gow Mac filament as T.C. detector. Air, argon, oxygen and nitrogen were injected in flowing stream of hydrogen in a stainless steel halical column 4 mm in inside diameter and 3 meters in length. The arrested flow method was used for measuring the variance. The values of diffusion coefficients thus obtained were within −2.47 to +2.43% of the values by Fuller's correlation, 0.12 to 3.38% of the values by correlation of Chapman‐Enskog and −29.99 to −32.94% of the values by Gilliland's correlation.
Vapor‐liquid equilibrium in mixtures of 1,3 dioxolane‐water
Authors: Francesconi Romolo , Castellari Carlo , Arcelli Antonio , Comelli Fabio
Published: March 2009

Vapor‐liquid equilibrium measurements were carried out with a Stage‐Müller apparatus on mixtures of 1,3 dioxolane‐water at isobaric conditions. Thermodynamic consistency of data was checked, and liquid‐phase activity coefficients were correlated using Wilson's equation, which was applied to various groups of data, each with a restricted range of temperature variation. The parameters δkj of Wilson's equation proved to be independent of the temperature.
Solidification of a low peclet number fluid flow in a round pipe with the boundary condition of the third kind
Authors: Lee S. L. , Hwang G. J.
Published: March 2009

This paper presents a theoretical investigation on the solidification of a low Peclet number fluid flow in the thermal entrance region of a round pipe. The velocity is assumed laminar and fully developed throughout the pipe and the fluid temperature is taken to be uniform at X = −∞. The pipe wall is adiabatic at X ≤ 0 and is cooled convectively at X ≥ 0. The exact solution in the liquid and solid phase are obtained by using the method of separation of variables and constructing two sets of orthonormal functions from the nonorthogonal eigenfunctious at X = ± 0.

The solutions including temperature distributions, liquid‐solid interfaces and Nusselt numbers for the parameters, Bi = 20, 4, 0.4, 0.04, Pe = 1, 3, 5, 10, 20, 30, ∞ and the superheat ratios, ξ = (1 − θf)/θf, θf= 0.1, 0.2, …, 0.9 are presented in this paper. The length of ice‐free zone xf corresponding to Pe = ∞ are in excellent agreement with the existing solution.
Mass transfer coefficients in mechanically agitated gas—aqueous electrolyte dispersions
Authors: Hassan Ibrahim T. M. , Robinson Campbell W.
Published: March 2009

The oxygen transfer characteristics of gas‐aqueous electrolyte solution dispersions have been studied in a laboratory‐size, mechanically‐agitated tank equipped with a 6‐flat blade turbine of standard dimensions (DI/T = 1/3). The effects of mechanical agitation power input per unit volume (Pg/V), gas superficial velocity (vS) and aqueous‐phase ionic strength (Γ) upon the overall volumetric mass transfer coefficient (kL a) and the liquid‐phase mass transfer coefficient (kL) are presented. In the range of 0.2 ≤ Γ ≤ 1.2 kmol(ions)/m3, the results of this study indicate that kL increases with increasing Γ is independent of P/V for Pg/V < 2000 W/m3 but decreases with increasing Pg/V above that level and is independent of vs over the range of gas velocities studied. On the other hand, KL a was found to be dependent on all three variables (Pg/V, vg, and Γ).
Continuous phase axial mixing in rotary disk contactors
Authors: Venkataramana J. , Degaleesan T. E. , Laddha G. S.
Published: March 2009

This paper presents a review of important investigations on axial mixing in the continuous phase in rotary disk contactors (RDC) and analyses the various literature data in terms of the flow number (DR N/ue) and a geometry factor Gf. A new model equation has been developed to represent continuous phase axial mixing in the RDC taking into account the factors affecting the recirculation flow within the compartment and the main flow through the compartment in terms of disk‐Reynolds number and modified tube‐Reynolds number respectively. A satisfactory expression for Gf has been obtained on the basis of the present proposed model and analysis of data of available literature and those of the present work, covering laboratory and industrial size columns of 10 different investigators varying from 3.5 cm to 218 cm dia involving 19 different column geometries. The following forms of generalized correlation for continuous phase axial mixing in RDC have been suggested.
On the combinatorial part of the UNIFAC and UNIQUAC models
Authors: Kikic I. , Alessi P. , Rasmussen P. , Fredenslund A.
Published: March 2009

The excess Cibbs energy of liquid mixtures may be predicted using group contribution models (f.ex. UNIFAC and ASOG), or it may be correlated using molecular models such as UNIQUAC. Group contribution models and the UNIQUAC model contain a combinatorial contribution which accounts for size‐ and shape‐effects and a residual contribution which accounts for interactions among groups or molecules. A new expression for the combinatorial contribution is given which yields much improved predictions of the excess Gibbs energy of systems where the residual contribution may be expected to be zero (e.g., mixtures of aliphatic hydrocarbons). It is shown that it is advantageous to incorporate the new combinational expression into future modifications of the UNIFAC model.
The chlorination kinetics of zirconium dioxide in the presence of carbon
Authors: Bicerolu O. , Gauvin W. H.
Published: March 2009

The kinetics of the chlorination of compacted spherical pellets of zirconium dioxide and carbon were studied over a particle temperature range of 1400 to 1950 K. A plasma of pure chlorine generated by an induction torch provided both the high‐enthalpy field and the reacting gas. The influence on the rate of conversion of temperature, chlorine concentration and carbon content were determined experimentally. Based on both experimental and theoretical studies, rate equations were developed.

The rate of chlorination was influenced by the separation distance between ZrO2 and carbon particles in the pellets, hence a shrinking‐core model was not obeyed. Instead, a new reaction model was proposed. The experimental results provided adequate information for the selection of optimum conditions with respect to reactor type, temperature and carbon content for an industrial process.
The production of synthetic organic liquids from wood using a modified nickel catalyst
Authors: Boocock D. G. B. , Mackay D. , Franco H. , Lee P.
Published: March 2009

Extended batch reactions show that fast‐growing hybrid poplar suspended in water is completely converted to oil and some gas when stirred at 340°C in the presence of Raney nickel. The oil is less viscous when hydrogen is present at sufficiently high pressure. The catalyst is stable up to the maximum time studied (14 hours). The oils typically contain 77% carbon, 7.5‐8.5% hydrogen, and 12‐13% oxygen, have viscosities in the range 5000‐8000 mPa.s and higher heating values of around 35 MJ.kg−1. Nickel produced by reduction of nickel carbonate in situ is also an effective and more practical catalyst.
Intraparticle effects in char combustion steady state analysis
Authors: Srinivas B. , Amundson Neal R.
Published: March 2009

A model is developed to study the intraparticle effects of char combustion which incorporates the reactions, C + 1/202 → CO, CO + 1/202 → CO2 and CO2 + C → 2CO with appropriate intrinsic kinetics. Based on some limiting cases a feasibility region, inside which the solution should lie, is developed. In almost all cases the major product is CO with CO2 production 2 to 3 orders of magnitude lower. A maximum of three steady states is observed for the parameters chosen. The combustion rate decreases with increase in particle size and increase in boundary layer thickness. The solution structure depends strongly on the radiation conditions which obtain and on the transport properties inside the particle. The purpose of this study is to determine the effect of intraparticle transport without the confounding effects of other phenomena.
Surface mass transfer processes using peat as an adsorbent for dyestuffs
Authors: Mckay Gordon , Allen Stephen J.
Published: March 2009

The factors affecting the initial rate of Telon Blue (Acid) dye adsorption onto peat have been investigated. The surface mass transfer coefficients for the rate of dye removal from solution have been determined and correlated as the dimensionless mass transfer term Sh/Sc0.33. The function Sh/Sc0.33 has been correlated with respect to four variables, namely, agitation, initial dye concentration, peat particle size range and the temperature of the dye solution. The mass transfer term varies with T5.5, dp0.13, co−1.1 and R.P.M.0.26; consequently temperature has the most pronounced effect on the mass transfer coefficient.
Application of a linear‐three‐phase model to a fluidized‐bed reactor
Authors: Kuhne J. , Wippern D.
Published: March 2009

A linear three‐phase model for fluidized bed reactors is proposed. The progress of that model is, that it considers the adsorption of the gas on the solid particles, which will influence the residence time behavior of the system. The solution in the Laplace‐domain is given explicitly, the time‐domain solutions have been approximated by a numerical method. The applicability of the model is shown by means of a 19cm‐diameter fluidized bed.
Direct method for the prediction of expanded bed height in liquid‐solid fluidization
Authors: Ganguly U. P.
Published: March 2009

A simple correlation has been developed to predict the expansion of a liquid fluidized bed, consisting of particles varying in size and/or density, which is of the following form:

The relationship is valid over the voidage range from ϵmf to ϵr = 0.96 and gives directly the expanded bed height Le without the determination of the bed porosity ϵe as in existing correlations. The size and density of the solids varied from 30/40 to 72/80 mesh BSS and from 1.67 to 4.33 gm/cm3 respectively while the range of Ret varied from 0.12 to 43.66. The standard deviation for measurements on unicomponent and multicomponent systems has been calculated to be 11.5% and 19.6% respectively at an L/D ratio of 2.0.
On the real molecular weight of polyethylene oxide of high molecular weight in water
Authors: Wolff Claude
Published: March 2009

It is shown that water is close to being a theta solvent for polyethylene oxide which is highly aggregated in this solvent. This result is in agreement with the behaviour observed by hydrodynamic measurements (turbulent drag reduction and concentration and shear dependence of the viscosity). With the molecular weight correction proposed in this work, the onset drag reduction data obtained with Polyox agree well with Virk's theory.
Ozonation of cyanide with emphasis on gold mill wastewaters
Authors: Rowley W. J. , Otto F. D.
Published: March 2009

Mass transfer ami treatability studies were conducted in a stirred Danckwerts cell to investigate the ozonation of 1) simple cyanide, NaCN, and 2) cyanides found in the barren bleed of Giant Yellowknife Mines Limited. A theoretical analysis of the simultaneous absorption and reaction of ozone in a NaCN solution was used to calculate an overall second order rate‐constant for the reaction with ozone. The order of magnitude value at 23°C is 104 to 105 L/(mol.s). Enhancement factors for the ozonation of the barren bleed are in the range of 80 to 300 for bulk total cyanide concentrations of about 38 to 195 mg/L respectively.

Attainable treatment levels for cyanide and thiocyanate and stoichiometric relationships are presented along with an economic assessment for an ozone installation for the Giant Yellowknife Mines Limited case.
A preliminary study of the corrosiveness of methyl fuel/gasoline blends on materials used in automotive fuel systems
Authors: Foulkes F.R. , Kalia R.K. , Kirk D.W.
Published: March 2009

A preliminary study was made of the corrosiveness of 15% by volume methyl fuel/gasoline blends on materials conventionally used for gasoline service in automotive fuel systems. The presence of water, salt and air dramatically increased the corrosiveness of the fuel. Of the metals studied, aluminum was relatively unaffected, while copper, brass, steel (types 1181 and 1008), zinc and template all showed signs of corrosion. Non‐metallic samples, particularly expanded polyurethane and Buna‐N. underwent greater attack in the presence of methyl fuel. Conductivity measurements showed that the presence of water and salt in the fuel can cause galvanic corrosion to occur.
Theoretical and experimental studies of confined vortex flow
Authors: Reydon R. F. , Gauvin W. H.
Published: March 2009

A study of the air flow characteristics is reported for a vortex chamber 122 cm in diameter consisting of an upper cylindrical section 61 cm high and of a lower conical section 108 cm high. Measurements were made with a five‐channel pressure probe of the radial profiles of tangential and axial velocities, with varying inlet air velocity and axial distance from the top of the chamber. Measurements of the static pressure profiles were made simultaneously. Finally, the angle of flow of the air entering through the single tangential inlet could be adjusted, and its effects on the flow recorded.

From these results and from a theoretical analysis, generalized expressions for the tangential velocity profiles were obtained for the two regions of flow, forced‐vortex and quasi‐free vortex, which prevail in a confined vortex chamber, as a function of the entrance air velocity and of the radius at the point considered only. The angle of entering air was found to have no effect on the tangential velocity and only a minor effect on the static pressure distribution. The outlet diameter of the chamber was found to have a large effect on the profile of the axial velocities, reflecting the influence of the chamber static pressure on the latter.
A preliminary experimental investigation into the air‐lift pumping of shear‐thinning suspensions
Authors: Heywood Nigel I. , Michalowicz Robert A. , Charles Michael E.
Published: March 2009

In a recent article(1), it has been postulated that the air‐lift principle may be applied to the raising of liquids or suspensions possessing shear‐thinning Theological behaviour, in order that significant reductions in power requirement may be made compared with conventional mechanical pumping. Using a 41 mm i.d. riser, an experimental study of the raising of highly flocculated kaolin suspensions, at volumetric concentrations ranging from 8.1 to 18.4%, has confirmed that power savings are possible, provided that the isothermal efficiency of the compressor for air injection is substantially greater than mechanical pump efficiencies. Such power savings appear limited to a range of superficial air velocity in the air‐lift riser of 0.25 to 1.25 m.s.−1, and to suspensions containing a relatively high volumetric fraction of flocculated solids.
Rheological comparison of four blow molding resins
Authors: Garcia‐Hejon A. , Dealy J. M. , Kamal M. R.
Published: March 2009

For molten polymers, each theological property provides a different basis for comparison and characterization. This point is illustrated by reference to the results of an extensive testing program involving a series of four commercial blow molding resins, each produced by a different Canadian manufacturer. Three high density polyethylenes were studied at 170°C, while a polypropylene was studied at 190°C. Properties measured included viscosity, first normal stress difference, dynamic viscosity, storage modulus, extrudate swell as a function of time and shear rate, and stress growth functions for both shear and uniaxial elongation.
Effect of heat flux on pressure drop in low pressure flow boiling in a horizontal tube
Authors: Shoukri M. , Yanchis R. J. , Rhodes E.
Published: March 2009

There has been a lack of research specifically examining the effect of heat addition on frictional pressure drop in two phase flow systems. The work presented herein is a result of a series of experiments, using a low pressure steam‐water loop to investigate this effect. It was found that the application of constant heat flux results in a significant increase in frictional pressure drop at certain qualities. It was also found that increasing mass flux or decreasing system pressure shifts the maximum pressure drop towards lower qualities. The observed phenomenon is believed to be the result of liquidvapour interactions at the slug‐annular flow regime transition. This has been confirmed by flow pattern analysis using Mandhane's flow map.
Flow regime boundaries for an interior subchannel of a horizontal 37‐element bundle
Authors: Aly A. M. M.
Published: March 2009

A needle contact probe system has been constructed and used to determine flow regime transitions for an interior subchannel in the upper half of a 37‐element horizontal bundle (to include the effect of gravity separation) for adiabatic air‐water flow. For the experimental range considered (up to ˜15.5 K*s−1, 50% quality), five distinct flow regimes were identified. Using the equivalent hydraulic diameter concept and cross‐sectional average superficial velocities, air quality and total mass flux, flow regime maps were constructed. These maps are shown to deviate from pipe flow regime maps. The stratified smooth flow regime was never observed at the lowest flow rate considered due to the periodical disturbance of the flow by the bundle end plates and mid‐plane spacers.
Gasification of western canadian lignite coals
Authors: Heijden S. P. N. Van Der , Verma Arun
Published: March 2009

Samples of a typical Estevan lignite coal (empirical formula CH0.81 O0.25 N0.01 S0.003) with a heating value of 16.713 MJ/kg were gasified with air only and air/steam mixtures at near atmospheric and high pressures up to 6 MPa.

The carbon content of ash/char residues of the gasification reactions varied from 1.2% for air/steam reactions and was in the 16‐53% range for reactions using air only, For all experiments the end point was clearly indicated by a rapid change in oxygen concentration in the gas samples.

Plots of the fractional conversion of carbon as a function of time, showed high initial reaction rates as the volatile matter in coal is gasified. The rates diminish as the carbon is being consumed.

The heating values for the gas samples collected during each run showed a large correlation with the methane content of the sample.
The relative hydrogen saturation factor and its use for material balance analysis of underground coal gasification
Authors: Edwards Wayne C.
Published: March 2009

Steady oxygen and hydrogen conservation relationships for an underground coal gasification reactor were combined with a simple model for the evolution of oxygen and hydrogen within the gasifier to yield a relationship for the fraction of evolved carbon originating from char gasification. This relationship is independent of the flow terms due to injection and production of water, whether the gas which leaks from the gasifier is like injected gas or produced gas. The relationship is a function of a dimensionless parameter called the relative hydrogen saturation factor of the evolved gas. Equations based on the concept of the relative hydrogen saturation factor are given for the carbon recovery efficiency and the fraction of exploited coal which has been completely gasified.

Data from two field experiments were analysed. Results indicate that the relative hydrogen saturation factor is a valuable monitor of the relative importance of char gasification. The carbon recovery efficiency predicted by the analysis compares fairly well with the value measured from an excavation of a gasification site. The fraction of evolved carbon originating from char gasification, the carbon recovery efficiency, and the fraction of exploited coal which has been completely gasified are given for each field test.
Hydrogen adsorption measurements by the dynamic pulse method
Authors: Wanke S. E. , Lotochinski B. K. , Sidwell H. C.
Published: March 2009

Hydrogen adsorption uptakes by supported metal catalysts are commonly measured by the dynamic pulse technique. The pulse technique has several experimental advantages over the conventional static method, but the hydrogen uptakes measured by the pulse method are not easily interpreted. The measured pulse adsorption uptakes are influenced by the desorption of weakly adsorbed hydrogen. We found that the desorption of hydrogen at room temperature depends on the metal and the metal dispersion. We also found that hydrogen uptake measurements by the dynamic pulse method under well defined conditions are very reproducible.
The thermal conductivity of oils sands
Authors: Karim G. A. , Hanafi A.
Published: March 2009

Measurements have been made of the effective thermal conductivity of some samples of Athabasca oil sands using a steady state method over the temperature range 20°C – 120°C. The bitumen content of the samples was altered from its natural value by mixing with additional sand and the resulting values of the thermal conductivity were found to increase with increasing the oil content. Moreover, the effective thermal conductivity values were found to decrease with increasing temperature.
Effect of surface roughness on the rate of mass transfer to a pipe wall in the mass transfer entry region
Authors: Sedahmed G. H. , Soliman M. Nagy , El‐Kholy N. S.
Published: March 2009

Rates of mass transfer between a turbulently flowing solution and the inner wall of a rough tube were measured using an electrochemical technique involving the measurement of the limiting current of the cathodic reduction of potassium ferricyanide in a large excess of sodium hydroxide. Roughness was made by cutting V‐threads in the inner surface of the pipe. Four degrees of surface roughness with peak to valley height ranging from 0.047 to 0.833 mm were used. Reynolds number ranged from 5000 to 40000. Under these conditions it was found that surface roughness increases the rate of mass transfer by an amount ranging from 10% to 115% depending on the degree of roughness and Reynolds number. The data were correlated in the mass transfer entry region by the equation:
Propriétés photocatalytiques de Ta2O5/SiO2
Authors: Kaliaguine S. , Gnakoury M. , Roberge P. C.
Published: March 2009

The photocatalytic properties of deposited tantalum oxide (Ta2O5) on silica, in the reaction of photocatalytic oxidation of cyclohexane by oxygen, have been studied. The properties of this catalyst were compared with those of the previously studied system V2O5/SiO2, and it was concluded that the mobilities of V+5 and Ta+5 ions on the surface of silica under radiation arc verymuch different. This study was completed by an analysis of the diffuse reflectance spectra and a thermogravimetric analysis of the used catalysts. The conclusion was that the site active in the photocatalytic reaction, is hydrated during the oxidation of cyclohexane.
Hydrogenation of carbon monoxide over nickel zeolite catalysts — effect of reduction and calcination
Authors: Bajpai Pramod K. , Bakhshi Narendra N. , Mathews Joseph F.
Published: March 2009

NiNaY zeolite catalysts were prepared by successive ion exchange of NaY. The catalysts were characterized for BET surface area, nickel metal area, nickel crystallite size and crystallinity. The methanation of carbon monoxide was studied in a fixed bed reactor in the temperature range of 523–673 K. Specific activities for methanation were found to vary with nickel concentration and crystallite size. The values of nickel metal area and specific methanation activity for the uncalcined catalysts were found to be higher compared to those of calcined catalysts. The effect of reduction at 723 K on the zeolite base structure and the effects of calcining the catalyst on metal area, crystallite size and activity are discussed.
Hydrogen production by the catalytic steam reforming of methanol part 1: The thermodynamics
Authors: Amphlett J. C. , Evans M. J. , Jones R. A. , Mann R. F. , Weir R. D.
Published: March 2009

The thermodynamic equilibria involved in the catalytic steam reformation of methanol to produce hydrogen have been examined over the ranges of pressure 101–3040 kPa, temperature 400–700K and water to methanol feed ratio 1.5–0.67. Four models have been considered based upon possible reaction products and the equilibrium composition of each model calculated.

The presence of methane and carbon reduce the quantity and quality of hydrogen produced. The best condition for hydrogen production occurs at 500K in the model in which carbon (soot) and methane gas are excluded and where pressures are low, and water is in excess in the feed. To achieve these conditions in practice the reactions for methane formation, which is thermodynamically favoured, and the appearance of carbon (soot) must be inhibited.
Solubility of acetylene in several polar and non‐polar solvents and solvent mixtures
Authors: Miyano Y. , Hayduk W.
Published: March 2009

Solubilities of acetylene in pure solvents, hexane, cyclohexane, hexadecane, benzene, carbon disulfide, carbon tetrachloride, methanol, butanol and ethylene glycol, and mixtures, hexane‐hexadecane and butanol‐ethylene glycol, are reported at atmospheric pressure and temperatures ranging from 0 C to 50 C. Hydrogen bonding (H‐bonding) factors expressed by a simplified Margules equation were found useful to correlate the solubilities of gases in the pure solvents as well as the solvent mixtures.
Deactivation studies of nickel catalysts used in the methanation of carbon monoxide
Authors: Bajpai P. K. , Bakhshi N. N. , Mathews J. F.
Published: March 2009

Four laboratory prepared catalysts (Ni/Al2O3, NiNaY‐uncalcined, NiNaY‐calcined, NiCaY‐calcined) and a commercially available catalyst G‐87 were studied for their deactivation behavior over a period of 24 h at 573 k for various H2/CO ratios (3.1, 3.8, 6.4 and 24.5). The results indicated that the activities did not change much with time at H2/CO ratios of 3.8 and higher. Detailed measurement of catalytic activities, crystallite sizes, metal areas and carbon depositions were made at an H2/CO ratio of 3.1. These measurements indicated that sintering and carbon depositions occurred on all the catalysts thus deactivating the catalysts. An attempt has been made to explain the catalytic behavior in terms of crystallite size changes and carbon depositions. Limited regeneration studies of G‐87 and NiNaY‐calcinated catalysts have also been done.
The effect of surfactant on terminal velocity of and mass transfer from a fluid sphere in a non‐newtonian fluid
Authors: Kawase Y. , Ulbrecht J.J.
Published: March 2009

The effect of interfacial tension gradients on creeping flow past a fluid sphere (bubble or drop) in a non‐Newtonian fluid is investigated. The drag force and the Sherwood number for contaminated fluid spheres moving in a non‐Newtonian fluid are obtained by an approximate solution of equations of motion in the creeping flow regime. It has been found that surface‐active agents decrease both the terminal velocity and the mass transfer rate. The influence of the flow index of the power‐law on both the drag coefficient and the Sherwood number is superimposed over the influence of the interfacial tension gradient.

Comparisons between the present analysis and the available experimental data in the literature show reasonable agreement for the terminal velocity and the Sherwood number.
Separation of nitrocellulose fine particles from industrial effluent with organic polymers
Authors: Wang Lawrence K. , Pressman Maurice , Shuster William W. , Shade Ray W. , Bilgen Fusun , Lynch Thomas
Published: March 2009

Polymers were used in the experiments to determine optimum type and dosage requited for effective treatment of an industrial effluent containing nitrocellulose fine particles. It was found that (a) contact flocculation filtration was not effective for treating the nitrocellulose‐manufacturing wastewater due to the high initial turbidity; (b) mixing, flocculation, and settling of the wastewater with cationic polyelectrolyte and bentonite clay gave greater than 95% turbidity removal; (c) with the same optimum chemical dosages, mixing, flocculation and centrifugation also gave about 97% turbidity removal; and (d) with the same optimum chemical dosages, mixing, flocculation, sedimentation and filtration removed 99.9% of the wastewater turbidity.
Reactions and residence time distributions in motionless mixers
Authors: Nauman E.B.
Published: March 2009

Motionless mixers are modeled as open, circular tubes with parabolic velocity distributions except at a few isolated planes where radial mixing occurs via an instantaneous coordinate transformation. Possible transformations are constrained by continuity of volumetric flow. Complete flow inversion appears the theoretically optimal transformation, being superior to complete mixing.

A model consisting of intermediate planes of complete mixing approximates existing experimental data on the Kenics Static Mixer when four Kenics elements are made equivalent to a single plane of complete mixing. This model preserves the essential nature of a laminar flow residence time distribution while providing a relatively simple means of estimating mixer performance.
Laminar flow past a permeable sphere
Authors: Nandakumar K. , Masliyah Jacob H.
Published: March 2009

Flow past an isolated permeable sphere has been studied. The complete Navier‐Stokes equation governs the fluid motion outside the sphere, while Brinkman's extension of Darcy's Law is assumed to hold within the porous sphere. The Navier‐Stokes equation is solved using a finite difference scheme. The flow within the porous sphere is solved in two different ways, each being efficient over a particular range of Reynolds number. Drag Coefficients are presented for dimensionless permeability, β, of 5, 10, 15, and 30 and for Reynolds numbers up to 50. The computed drag coefficients are within 10% of the experimental values observed by Masliyah and Polikar for 15 < β > 33, the range covered in their work. Separation was observed only for β > 10. The onset of separation is delayed considerably in porous spheres.
Modeling of Shallow Fluidized Bed Reactors: I. analytic solution of a simplified model
Authors: Chang C. C. , Fan L. T. , Rong S. X.
Published: March 2009

A fairly general dynamic model for shallow fluidized bed reactors is developed, and analytic solutions for the governing equations of the model are obtained after some simplification. The bubble size, the lateral dispersion coefficient of solids, the level of the excess fluid reactant and the structure of the bed are examined to determine their effects on the conversion of solids. It has been shown that the conversion of solids is influenced profoundly by the bubble size and that it is advantageous to employ a shallow fluidized bed reactor if a high conversion of solids is required.
Liquefaction of aspen poplar wood
Authors: Eager R. L. , Mathews J. F. , Pepper J. M.
Published: March 2009

Dried and green aspen poplar wood suspended in water containing alkaline catalysts has been converted completely to an oil, water‐soluble chemicals and gases if heated for one hour in the presence of carbon monoxide in a rocking batch reactor. Within the ranges of parameters studied: temperature (593—633 K), nominal reaction times (0—1 h), water‐to‐wood ratio (0.5:1—5:1), catalyst (Na2CO3, K2CO3, NaOH), amount of catalyst (7.0—12.5 wt %) and initial hydrogen to carbon monoxide ratios (2:1—0:1), the water‐to‐wood ratio was most important. Oil yields of ˜50% with a carbon plus hydrogen content of ˜80% and representing a carbon recovery of ˜66% were obtained. The higher heats of combustion ranged from 32.2 to 36.0 MJ/kg.
Correlations for prediction of molecular diffusivities in liquids
Authors: Hayduk W. , Minhas B. S.
Published: March 2009

New correlations have been developed for diffusivities in liquids at infinite dilution for normal paraffin solutions, for aqueous solutions, as well as generally for polar and non‐polar solutions. The molar volume, parachor and radius of gyration for both solute and solvent were used as correlating parameters. The new correlations represent a significant improvement in accuracy for predicted diffusivities.
UNIFAC and infinite dilution activity coefficients
Authors: Alessi P. , Kikic I. , Fredenslund Aa. , Rasmussen P.
Published: March 2009

This paper deals with the possibility of estimating UNIFAC parameters from infinite dilution activity coefficients. Such activity coefficients can be obtained from gas chromatographic measurements (GLC).

In some cases the original UNIFAC equations do not represent very well the variations of the activity coefficients with the concentration in the very dilute regions. It is then not possible to estimate reliable parameters from infinite dilution activity coefficients alone.

It is shown that a recent modification of the combinatorial part of the UNIFAC equations allows for the estimation of UNIFAC parameters from infinite dilution activity coefficients for alkane—‐ketone, alkane—‐alcohol, and other mixtures.
Dynamics of adsorption columns with bacterial growth outside adsorbents
Authors: Tien Chi , Wang Shu‐Chieh
Published: March 2009

The dynamics of adsorption columns with the presence of bacterial activity was studied analytically and experimentally. The bacterial activity results in the formation of growing microbial films outside adsorbents. Equations describing the interaction between adsorption and bacterial growth were formulated and algorithms for their solutions developed. Experiments relating to the removal of valeric acid from aqueous solutions with granular carbon in the presence of denitrifying bacteria were performed to substantiate the analysis.
Coupling of mixing and microbial kinetics for evaluating the performance of bioreactors
Authors: Bajpai R. K. , Reuss M.
Published: March 2009

The effect of the dynamics of the mixing process in mechanically stirred bioreactors upon their performance has been investigated by using a circulation‐model for flow of fluid and a two‐environment‐model to account for the extent of micromixing in the vessel. With the help of an empirical kinetic model to depict the oxidative and the fermentative growth of bakers' yeast, experimentally observed effects of initial sugar concentrations upon critical dilution rates in continuous cultures of this system could be explained. Effect of different scales of operation upon productivities of fed‐batch cultures of bakers' yeast could also be satisfactorily predicted. A discrete simulation procedure was found to be a convenient tool in coupling the two‐environment circulation‐model of mixing with kinetics of microbial reactions.
Transformation of propene into acrylonitrile with nitric oxide over nickel oxide alumina catalyst in a continuous stirred tank reactor
Authors: Agbebavi James Thomas , Rouleau Denis , Pajonk Gerard
Published: March 2009

Catalytic transformation of propene (C3H6) with nitric oxide (NO) over nickel oxide alumina catalyst (2NiO, Al2O3) has been investigated using a continuous stirred tank reactor at temperatures varying from 270 to 400°C, under atmospheric pressure. The main products found were acrylonitrile (C3H3N) and carbon dioxide (CO2). The rate of formation of C3H3N and the rate of disappearance of C3H6 were both correlated by the same model based on a redox mechanism:

ri = kiokirPNOPHC/(kioPNO + kirPHC)

The constants in the rate equation were expressed as a function of temperature.
Elutriation characteristics of solids from liquid fluidized bed systems Part I: Onset of elutriation
Authors: Ganguly V. P.
Published: March 2009

Experimental data for the minimum elutriation velocity ume of solids for 134 different systems have been correlated by

The ranges of the different groups investigated were as follows:

For all of the experiments, the fluidizing liquid was water and the tube had an inside diameter of 4.92 cm. The standard deviation for the above correlation is 21.6 per cent.
Elutriation characteristics of solids from liquid fluidized bed systems Part II: Prediction of equilibrium bed concentration
Authors: Ganguly U. P.
Published: March 2009

During elutriation of binary mixtures of solids differing in size and/or density, it has been found that the rate of decrease in concentration of the finer/lighter component is very fast at the beginning, falls off gradually and assumes an asymptotic value towards the end. The bed at this latter condition seems to have attained a retentive capacity for finer/lighter particles and this concentration has been termed the equilibrium bed concentration, CE. For all practical purposes, this sets the lower limit which the concentration of the elutriating component in the bed can attain, i.e. the maximum degree of removal of the particles from the system under a given set of operating conditions. Based on the experimental values of CE obtained from concentration versus time plots, an empirical correlation has been proposed as follows:

The correlation coefficient and the per cent standard deviation have been calculated to be 0.943 and 20.0, respectively.
On the annular‐to‐wavy flow pattern transition during condensation inside horizontal tubes
Authors: Soliman H. M.
Published: March 2009

The annular to wavy and intermittent flow pattern transition during condensation inside horizontal tubes was investigated. Eight data sets corresponding to different tube diameters and different test fluids were used to test the predictions of several diabatic and adiabatic correlations. Deficiencies were found in these correlations which prevented consistent agreement with the data base. An improved correlation is proposed and shown to have a good deal of generality and accuracy in predicting this transition.
A chromatographic study of diffusion of single components and binary mixtures of gases in 4A and 5A zeolites
Authors: Kumar Ravi , Duncan Robert C. , Ruthven Douglas M.
Published: March 2009

Results of a chromatographic study of diffusion of light hydrocarbons and other permanent gases in 4A and 5A zeolites are reported. The data for CF4 and iC4Hm, on 4A sieve (no penetration of the zeolite lattice) suggest that micropore diffusion occurs primarily by a Knudsen mechanism. The majority of the measurements were made with small particles of crushed commercial pelleted zeolites under conditions of intracrystalline diffusion control. The dominance of intracrystalline resistance is shown by the similarity in the time constants obtained with different sizes of particle and the results are generally consistent with earlier gravimetric data. The data for the binary systems containing two adsorbed species are consistent with the simple hypothesis that each species in the mixture diffuses independently with the same intrinsic mobility as for single component diffusion at the same temperature. However, the actual diffusivity of a species in the binary mixture may differ from the pure component diffusivity due to differences in the form of the quilibrium isotherms.
Mass transfer modelling for GS heavy water plants: Part II: Tray efficiency on GS sieve trays
Authors: Neuburg H. J. , Chuang K. T.
Published: March 2009

A mass transfer model to predict tray efficiency on industrial GS process sieve trays is presented. Tray efficiencies are predicted from point efficiencies on large trays up to 8.5 m in diameter, by taking into account effects of liquid flow distribution, weeping, entrainment, gas mixing and liquid mixing in the downcomers. Predictions by the model agree with tray efficiencies measured at the heavy water plants.
Microscopic structure of athabasca oil sand
Authors: Takamura Koichi
Published: March 2009

A refined structural model for in situ oil sands is proposed in terms of the mutual arrangement of sand grains, fines, water and bitumen. In the Athabasca deposit, the sand grains consist mainly of quartz and their packing is such that the porosity is about 35%. In rich oil sand, 10–15% of the pore space is occupied by connate water whereas the remainder is occupied by bitumen. For lower grade oil sands, a direct correlation exists between the water content and the amount of fines (particles smaller than 44 μm) and an inverse correlation exists between the bitumen content and the amount of fines. These relationships are successfully explained in terms of the irreducible water saturation in a porous medium and the double layer interaction between sand and bitumen surfaces.
Methanation of carbon monoxide over alumina supported ni‐cu catalysts
Authors: Bajpai P. K. , Bakhshi N. N. , Dan‐Chu Liu , Mathews J. F.
Published: March 2009

Copper has been added as a second metal to a nickel‐dispersed‐on‐alumina methanation catalyst. Compared with the nickel catalysts without copper, the initial methanation activity was reduced drastically but the tendency to deactivate with time‐on‐stream was much less. There were also less carbon deposition and less sintering of metal particles with the copper‐added catalysts.
Species grouping in multicomponent adsorption calculations
Authors: Calligaris Mary Beth , Tien Chi
Published: March 2009

The validity of the assumption of species grouping, which combines several adsorbable species into a fewer number of pseudo‐species in adsorption calculations, was examined by comparing the equilibrium concentrations obtained from exact calculations with those obtained with the use of the assumption. It was found that if the adsorption affinities of the individual species exhibited by their single‐species isotherms are of the same order of magnitude, the use of the species grouping assumption yields acceptable results. This procedure applies to three situations, including those in which (a) all the species are grouped into a single pseudo‐species; (b) the various species are combined into several (but fewer) pseudo‐species; and (c) only some of the species are grouped, while the others remain individual species.
Evidence for bulk‐phase nitrogen dissolution in iron in catalytic ammonia synthesis
Authors: Jain A. K. , Hudgins R. R. , Silveston P. L.
Published: March 2009

Experiments were carried out in which the reactants, nitrogen and hydrogen were admitted to a fixed bed of triply‐promoted iron catalyst in the form of concentration step‐functions. Temperature was about 400°C, and total pressure was 2.38 MPs. The bed was stabilized with equimolal flows of hydrogen and nitrogen and then stepped up to pure hydrogen or down to pure nitrogen. From the rate of ammonia production, catalyst properties, and bed temperature behaviour, it was inferred that nitrogen is dissolved by the bulk phase of the iron catalyst. This result has important implications for a general model of transient and forced cyclic operation of catalyst beds.
Stabilization and destabilization of mineral fines‐bitumen‐water dispersions in tailings from oil sand extraction plants that use the hot water process
Authors: Hall E. Stanley , Tollefson Eric L.
Published: March 2009

Effects of acid and polyvalent cations on flocculation and settling of tailings dispersions from an oil sand extraction plant are used to develop a model for previously puzzling pH dependent aspects of the hot water process. The model features calcium‐bicarbonate surface complexes that reduce mineral fines‐bitumen interactions, destabilize bitumen‐water emulsions and enhance attachment of air bubbles to bituminous surfaces. Protonation of bicarbonate allows agglomeration through formation of calcium‐carboxylate bridging complexes at mineral‐bitumen interfaces.
Kinetics of the catalytic hydrogenation of 2‐Ethyl‐2‐Hexenal
Authors: Collins Dermot J. , Grimes David E. , Davis Burtron H.
Published: March 2009

2‐Ethyl‐2‐hexenal was hydrogenated over Raney Nickel and nickel boride in a batch slurry reactor. Using Raney Nickel, the reaction went to completion, and the formation of both 2‐ethylhexanal and 2‐ethylhexanol followed zero order kinetics.

Using nickel boride, the reaction ceased at the saturated aldehyde, with saturation of the double bond a zero order reaction. Unsaturated alcohol was not detected in any of the reaction mixtures.
Adsorption/desorption models: How useful for predicting reaction rates under cyclic operation
Authors: Jain Anil K. , Hudgins R. R. , Silveston P. L.
Published: March 2009

A computational study is reported of the behaviour of three catalytic reaction models containing conventional adsorption, desorption, and surface reaction steps under conditions of forced composition cycling in a mixed reactor. The models contained varying degrees of non‐linearity. With long cycle periods, the time‐average rate of reaction asymptotically approached the quasi‐steady state. Time‐average rate behaviour was found to be bounded by the asymptotes of quasi‐steady state rate under slow cycling, and the relaxed steady state under rapid cycling. It is concluded that the approach used until now to model catalytic reactions is very likely inadequate to describe the dynamics of forced cyclic operation observed in a number of experimental systems
Laminar dispersion in helically coiled tubes of square cross‐section
Authors: Saxena Alok K. , Nigam K. D. P.
Published: March 2009

In coiled tubes of non‐circular cross‐section the orientation of the cross‐sectional plane with respect to the direction of the centrifugal force has a significant effect on residence time distribution (RTD) which has been recognized for the first time. This aspect has been experimentally investigated in helically coiled tubes of square cross‐section, under the conditions of negligible and significant molecular diffusion.
Surface diffusion as rate determining step in activated chemisorption
Authors: Birnholtz Hella , Nir Avinoam , Lotan Noah , Aharoni Chaim
Published: March 2009

It is assumed that heterogeneous surfaces contain regions with various activation energies for adsorption. Adsorbate is taken up at regions of low activation energy and it migrates subsequently to regions of higher energy by surface diffusion. Surface diffusion is activated and it determines the rate of the overall adsorption process. Expressions derived on the basis of this model are consistent with Aharoni–Ungarish (1976) rule concerning the kinetics of chemisorption, viz the plot of the reciprocal of the rate against the time is sigmoid and the kinetics obey successively the Bangham Equation, the Elovich equation, and a first order equation.