bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of catalyst surface heterogeneity on the fischer‐tropsch synthesis
Authors: Rice N. M. , Hsu C. C. , Wojciechowski B. W. 
Published: March 2009

AbstractWe find that the surface energetic heterogeneity of Fischer‐Tropsch catalysts is either not important kinetically or may be masked by the effect of increasing molecular size, so that the classical Anderson‐Schulz‐Flory distribution is routinely observed in product distributions. The anomalous yields of C1 and C2 observed in many cases may also be due to surface heterogeneity but can in practice be readily, and more conveniently, accounted for by assigning individual rate constants to their formation.The “break” sometimes observed in ASF distributions cannot be explained by surface heterogeneity and is best explained by the presence of two distinct modes of product formation.
The entry length for slurries in horizontal pipeline flow
Authors: Colwell J.M. , Shook C.A. 
Published: March 2009

AbstractThe entry length for horizontal slurry pipeline flows has been determined experimentally using a pipeline of diameter 50 mm. Concentration and velocity distributions have been measured in the vertical direction at positions 6, 50 and 185 diameters downstream of the entrance.The measurements show that the entry length is of the order of 50 pipe diameters for sand slurries. High particle settling velocities give somewhat shorter lengths than intermediate settling velocities. With lower density polystyrene particles for which dispersive effects are important, the entry length is significantly greater than 50 diameters. The velocity distributions show that the velocity profiles develop concurrently with the concentration profiles. For sand slurries, a two‐dimensional simulation gives a satisfactory representation of the developing concentration profiles.
Role of the contact points between particles on the reactivity of solids
Authors: Hao Yu‐Jun , Tanaka Tatsuo 
Published: March 2009

AbstractThrough the exact number of contact points between the two components of a solids system, the reactivity of the solids is expressed in terms of the molar ratio, the particle size ratio and the nature of the reacting system. The theory is confirmed by existing experimental data, revealing that the contact points play an important role for wide ranges of reactivity of solids.
Process design for offshore oil and gas production in cold ocean environment
Authors: Sen D. C. 
Published: March 2009

AbstractMany considerations influence the design of offshore oil and gas processing facilities such as type of platform, weight and space limitations, environmental conditions, government regulations, drilling support, enhanced recovery, and logistics of supply and market factors. Some of these factors have major impacts on the design and make offshore facilities different from those on land.This paper discusses some typical case scenarios with particular emphasis on processing crude oil in a cold ocean environment such as the Grand Banks off Newfoundland or Beaufort Sea. It describes certain basic requirements for the process design on offshore platforms. Every design is unique for its particular situation.
Prediction of the thermal conductivity of liquids and liquid mixtures including crude oil fractions
Authors: Teja Amyn S. , Tarlneu Gilliane 
Published: March 2009

AbstractA new method based on the Effective Carbon Number is presented for the prediction of the thermal conductivity of liquids and liquid mixtures. The Effective Carbon Number for each substance of interest can be calculated from its thermal conductivity at a reduced temperature of 0.6. The thermal conductivities of isoalkanes, cycloalkanes, aro‐matics, alkanes, carboxylic acids, ketones, esters and aldehydes over a range of temperatures were predicted using this method and the results were compared with experimental values. The thermal conductivities of defined mixtures were also predicted using a quadratic mixing rule for the Effective Carbon Number. Lastly, the thermal conductivities of undefined mixtures such as crude oil fractions were calculated by treating each fraction as a single pseudocompo‐nent. In all cases studied, calculated results compared favorably with experimental values.
The effect of steam temperature on the economics of a cogeneration power plant
Authors: Ham R. W. , Douglas P. L. , Fulford G. 
Published: March 2009

AbstractUsing steady‐state simulation, we have evaluated the effect of boiler superheat and reheat temperatures on the economics of the utility section of a Bayer Alumina Plant. These economics were compared with those of a steam plant which purchased power.Under this study's nominal economic conditions, producing steam and purchasing electricity was the cheaper option. A sensitivity analysis showed that the cogeneration plant became the better choice when the local cost of electricity rose above 10C/kWh. The plant economics improved monotonically with superheat temperature as did the thermo‐dynamic efficiency. However, for reheat, the plant economics did not improve monotonically with temperature even though the thermodynamic eficiency did; thus improvement in the thermodynamic efficiency does not always yield improved economics.
On the effect of particle size on heat transfer in vertical upflow of gas‐solids suspension
Authors: Sivakumar S. , Chidambaram M. , Shankar H. S. 
Published: March 2009

AbstractThe occurrence of a minimum in heat transfer coefficient with particle diameter in a vertical upflow transport column as reported by Jepson et al. (1963) is explained by the minimum in total surface area of solid particles per unit volume of column with particle diameter. The minimum in the external surface area of solids in the column is shown to be due to the counteracting effects of increasing solids holdup with particle diameter and decreasing specific surface area of solid particles with increasing particle diameter.
On the numerical solution of differential algebraic equations
Authors: Audry‐Sanchez Javier 
Published: March 2009

AbstractA method is proposed to transform a system of differential algebraic equations (D.A.E.) to a system of ordinary differential equations (O.D.E.) which can be solved relatively easily by standard numerical techniques.Two examples, including a model of an absorption tower, are given to illustrate the utility of the method. The example problems reveal that this easily implemented technique offers significant savings in CPU time compared to the numerical solution of the untransformed D.A.E.s particularly when the algebraic equations are nonlinear.Furthermore, it appears to be faster and/or more reliable than other numerical schemes which have been recently developed for equations of this type.
Studies on the inhomogeneous nature of the silent discharge reactor: Part 2. kinetic simulation of a differential batch reactor
Authors: Khan A. A. , Howarth C. R. 
Published: March 2009

AbstractThe silent discharge reactor is characterised by a large number of randomly distributed discrete primary reaction zones (PRZ). These are transient in nature. Primary electron‐molecule collisions take place here with subsequent quenching of the atom‐molecule or free radical‐molecule processes. A model of a differential batch ozonizer has been proposed to study the influence of various forms of current pulse train, and the chemical activity of dielectric surface. The effect of multiple exposure of the reaction products to a series of electron avalanches has been evaluated. Finally the effects of temperature field and electron concentration within the electron avalanches have been studied.
Mixing and combustion in a shallow coal‐limestone fluidized bed combustor
Authors: Ho T. C. , Kirkpatrick M. , Hopper J. R. 
Published: March 2009

AbstractA model based on the Monte Carlo approach was developed to simulate the mixing and combustion behavior of a shallow coal‐limestone fluidized bed combustor. The model involved the coupling of two sub‐models: a combustion sub‐model based on the two‐phase concept of fluidization and a mixing sub‐model based on our previously developed dynamic mixing model.The combustion sub‐model considered both the volatile and char combustion. It assumed that the combustor consisted of three distinct phases, i.e., jet, bubble and emulsion, with combustion occurring only in the emulsion phase. The mixing sub‐model considered the upward or downward movement of a coal particle in the bed as being governed by certain probability laws; these laws were, in turn, affected by the bubbling hydrodynamics.In all, the combustor simulation model took into consideration the effects of coal feed rate, coal size distribution, limestone size, air flow rate and combustor temperature on the combustor behavior. The simulation results included the dynamic response of coal concentration profile, coal size distribution, coal particle elutriation rate as well as the mixing status between the coal and limestone particles.
Sedimentation of polydisperse concentrated suspensions
Authors: Al‐Naafá Mohammed.A. , Selim M. Sami 
Published: March 2009

AbstractGravity sedimentation of bidisperse and tridiperse concentrated suspensions have been studied both theoretically and experimentally. Experimental data were collected from batch settling tests using fully‐characterized colored spherical particles. Ten sizes of particles with three different densities were used in the sedimentation experiments. Varying proportions of each size were used and total solids concentration ranged from 13% to 45% by volume. Previously published and newly collected data were compared with predictions from six available models. These models include those of Lockett and Al‐Habbooby (1973), Mirza and Richardson (1979), Masliyah (1979), Reed and Anderson (1980), Selim et al. (1983a, 1983b), and Patwardhan and Tien (1985). Based on the present study and a similar study by Law et al. (1987) on bidisperse suspensions of heavy (sinking) and light (buoyant) particles, it is found that the Selim et al. model represents the data more accurately as compared to the other models.
Axial dispersion characteristics of three (liquid‐liquid‐solid) phase fluidized beds
Authors: Kim Sang D. , Lee Myung J. , Han Joo H. 
Published: March 2009

AbstractThe effects of the continuous and dispersed phase velocity and particle size on the axial dispersion of the continuous phase have been determined in two (liquid‐liquid) and three (liquid‐liquid‐solid) phase fluidized beds. In a cocurrent liquid‐liquid flow system, the axial dispersion coefficient increases with both the dispersed and continuous phase velocities. In three phase fluidized beds, the coefficient increases with dispersed phase velocity but it decreases with the particle size. Also the coefficient exhibits a maximum value with an increase in the continuous phase velocity at the lower dispersed phase velocities, but it increases with the continuous phase velocity at higher dispersed phase velocities. The axial dispersion coefficients in terms of Peclet number have been correlated in terms of the ratio of fluid velocities and the ratio of the particle size to column diameter, based on the isotropic turbulence theory.
Cyclone collection efficiencies at very high temperatures
Authors: Patterson P. A. , Munz R. J. 
Published: March 2009

AbstractExperimental results for gas‐solid separations in a 102 mm diameter conventional cyclone operated with air heated to temperatures between 300 K and 2 000 K, are presented. Overall and fractional collection efficiencies were measured for alumina and silica having particle sizes of 100% less than 44 μm and mass median diameters of 5.0 and 10.0 μm respectively. Inlet velocities ranged from three to 42 m/s and inlet dust loads were between 0.3 and 235 g/m3. The dust load had a strong influence on the collection efficiency and the loading effect was stronger at high temperatures.
Generic model control — A case study
Authors: Lee P. L. , Newell R. B. , Sullivan G. R. 
Published: March 2009

AbstractThis paper outlines the use of a process model directly in a control algorithm. The process considered, a forced circulation single‐stage evaporator, is a nonlinear interacting process. The control strategy employing a process model derived from fundamental mass and energy balances is shown to outperform single loop and predictive control strategies by a significant amount. The control structure is first presented in general form and then specifically applied to this process.
Dynamic and pseudodynamic modelling of transient and periodic CSTR operation
Authors: Klusacek K. , Hudgins R. R. , Silveston P. L. 
Published: March 2009

AbstractUsing the simple catalytic reaction A+B°C, catalytic surface dynamics can be modelled either by assuming finite rates of adsorption and desorption (termed the dynamic model) or by assuming adsorption equilibrium between the gas and the surface (the pseudodynamic model). In general, the responses of the two models are quite different, the pseudodynamic model being unable to predict rate overshoot for reactor start‐up. Both models appear able to describe rate enhancement and simple (i.e. single frequency) resonance for forced feed composition cycling. Reasons for preferring the dynamic model over its pseudodynamic counterpart are discussed.
A similarity relationship for the pressure drop in vortex chambers
Authors: Vatistas G. H. , Lam C. , Lin S. 
Published: March 2009

AbstractThe paper focuses on the pressure drop across stationary and rotating chambers. The non‐dimensional pressure drop has been found to depend solely on a single dimensionless parameter which involves only geometric quantities. The finding is supported by past and present experimental evidence. The similarity relationship for the pressure drop is shown to be true for both types of vortex chambers. Based on the derived relationship and the experimental data, an empirical formula capable of predicting the pressure drop over a wide range of design conditions has been obtained using the least squares method.
Reconciliation of mass flow rate measurements in a chemical extraction plant
Authors: Holly W. , Cook R. , Crowe C. M. 
Published: March 2009

AbstractSince measurements of flow rates in a steady state chemical process are subject to errors, the laws of conservation and other constraints are violated. Total mass flow data from a chemical extraction plant are used to determine whether the process operated at steady state and to estimate the variances of the measurements. The data are then reconciled so as to minimize the weighted sum of squares of the adjustments and to test for gross error. Deletion of either of two particular flow rates is shown to remove all of the apparent gross errors in the data.
Mass transfer from discrete gas bubbles in a reciprocating plate column
Authors: Baird M. H. I. , Rohatgi A. 
Published: March 2009

AbstractMeasurements have been made of the uptake of oxygen in water from a series of discrete bubbles released into a 5 cm diameter reciprocating plate column. The rate of increase of dissolved oxygen in the water has provided data on the average mass transfer coefficients under the following conditions; (a) free rise in the absence of plates, (b) bubbles rising through a static plate assembly and (c) bubbles rising through moderately agitated plates (frequency up to 1.28 Hz). It was found that the mass transfer coefficients were higher under condition (b) than (a), and were further increased under condition (c). The results were compared with earlier data on mass transfer to agitated bubble dispersions.
Derivation of performance equations for solid‐solid screens
Authors: Gooding R. W. , Kerekes R. J. 
Published: March 2009

AbstractEquations relating efficiency of separation to reject loss of desirable material have been derived for solid‐solid screens. The derivations were based on the relative passage of particles through individual screen plate apertures and the extent of mixing on the feed side of the screen plate. Two limiting cases of mixing were considered: plug flow and mixed flow along the screen plate. Both barrier and probability screening were included in the analysis. The physical significance of the terms in the equations and the implications of their derivation were described in relation to wood pulp screening.
Non‐newtonian two‐phase circulation in bubble columns
Authors: Clark Nigel N. , Flemmer Rory L. C. , Van Egmond Jan W. 
Published: March 2009

AbstractGas‐liquid and gas‐slurry bubble columns are widely used in the mineral and engineering industries, particularly for aeration (oxidation), synthesis of oil and flotation of mineral fines. Even though gas may be introduced into a bubble column evenly through a distributor plate over the whole column floor, undesirable circulation patterns generally develop in the column. This paper extends a force balance approach (originally used for turbulent systems) to predict circulation in non‐Newtonian gas‐liquid mixtures and demonstrates how the rheological properties will affect a single circulation pattern in a column.
Gas‐liquid mass transfer in three‐phase fluidized beds with viscous pseudoplastic liquids
Authors: Schumpe Adrian , Deckwer Wolf‐Dieter , Nigam Krishna D. P. 
Published: March 2009

AbstractLiquid phase volumetric mass transfer coefficients for oxygen were determined in three‐phase fluidized beds of 8 mm glass spheres fluidized by a cocurrent flow of air and pseudoplastic polysaccharide solutions (carboxymethyl cellulose, xanthan). A semi‐theoretical relation for the effective shear rate was suggested. The mass transfer coefficients could be correlated, together with literature data for particle diameters of 3 mm and 5 mm in other liquids, using the terminal velocity as the particle‐specific property.
Turbulent mixing in coflowing plane jets
Authors: Grandmaison E. W. , Zettler N. L. 
Published: March 2009

AbstractThe scalar mixing field of a single plane jet and an array of three coflowing plane jets has been examined using marker nephelometry. Results are reported for the centreline behaviour of the mean and fluctuation concentration fields of the single jet and the triple jet array with Gi/Go = 1.39, 0.222 and 0.089, where Gi is the centre jet momentum and Go the momentum of both outer jets. Details of the flow scales including the half concentration width and integral scales are also reported for the single plane jet and the triple jet case with Gi/Go = 1.39 and 0.089. The centreline measurements were extended to the region where a tendency to axisymmetric behaviour was observed.
Condensation of vertical plate fins of variable cross section‐limiting solutions
Authors: Sarma P. K. , Chary S. P. , Rao V. Dharma 
Published: March 2009

AbstractThe purpose of the present theoretical analysis is to provide explicit solutions for the problem of condensation of vapours on the lateral surface of a long vertical plate fin of variable cross‐section. The formulation yields solutions to the Limiting cases so that the results can be employed in the design of the condenser section of a flat plate heat pipe in which the fin is considered to be an essential element in transporting heat liberated by the condensing vapours. It is observed that the local and average Nusselt numbers depend on fin parameter, fin profile index, Rayleigh number and degree of subcooling.
Modelling the kinetics of fast catalytic cracking reactions
Authors: Collyer R. , Larocca M. , De Lasa H. 
Published: March 2009

AbstractInstantaneous kinetic constants and gasoline selectivities have been determined for catalytic cracking of n‐hexadecane. The pulse technique was used in order to model the sequential build‐up of coke which occurs on cracking catalyst within a riser transport‐line reactor. The total amount of hydrocarbon injected per unit weight of catalyst was between 0 and 10. The mathematical model used to analyze the data was based on the unsteady state mass balance of the microcatalytic reactor with the assumption of plug flow. Results suggest a fast deactivation process during the run with fresh catalyst, while regenerated catalyst showed a slower deactivation. The catalyst regenerated three times evidenced a low apparent activation energy when temperature was increased from 500°C to 550°C.
Viscosity of cold lake bitumen and its fractions
Authors: Mehrotra Anil K. , Eastick Robert R. , Svrcek William Y. 
Published: March 2009

AbstractNew data are presented for the effect of temperature on the viscosity of bitumen fractions, which were obtained by vacuum distillation of a large Cold Lake bitumen sample. The viscosity of these fractions differs by several orders of magnitude; from 4.3 mPaϵs for Cut 1 to 430 000 mPaϵs for Cut 4 at 30°C. Cut 5 is a glass‐like solid at room temperature with a softening temperature of about 100°C, and has a viscosity of 800 000 mPaϵs at 120°C. The effect of temperature on the viscosity of each bitumen fraction is modelled very well with a two‐parameter correlation that was shown to be valid generally for Alberta bitumens. The results of bitumen viscosity calculations, based on a simple liquid‐mixture viscosity formula, are presented and compared with the bitumen viscosity data.
Natural convection from a radiating fin to thermally stratified medium of air
Authors: Sarma P. K. , Subrahmanyam T. , Rao V. Dharma 
Published: March 2009

AbstractIntegral analysis is used to study laminar natural convection from a vertical radiating fin situated in ambient air thermally stratified according to a power law variation of temperature. The phenomenon is treated as a coupled problem in which all the possible modes of heat transfer are accounted for in the constitutive equations. For stable thermal stratification of the medium, the local Nusselt is found to be a function of the radiation parameter, fin parameter, temperature ratio, stratification parameter, the exponent of the power law ‘m’ and the conventional Gr.Pr product. An approximate design relationship between the various parameters is established by the method of regression.
A multiobjective approach to the structuring of an efficient system for producing petrochemicals from alternative raw materials
Authors: Sokić Milorad , Zdravković Sonja , Trifunović Zoran 
Published: March 2009

AbstractPreviously reported data on the effects of the utilization of coal‐based raw materials within the petrochemical industry indicated a conflict between the objectives of efficient utilization of raw materials and energy in structuring an optimum system. The nature of this conflict was examined more closely by comparing system performances which refer to separate considerations of the conflicting objectives. The multiobjective approach was applied in order to generate compromise system structures and to determine the region in which the preferred compromise solution is to be found.
Particle slip velocities in air jets under atmospheric pressure and soft vacuum conditions
Authors: Bronet Murray S. , Boulos Maher I. 
Published: March 2009

AbstractLaser Doppler anemometry (LDA) is used for the measurement of gas and particle velocities in an air jet under atmospheric pressure and soft vacuum conditions. The slip velocity between the particles and the carrier gas at the exit of a particle injection probe is shown to depend on the geometry of the probe tip. With a standard probe tip, the particle velocity lagged behind the gas velocity at the exit of the probe. The addition of a section with a sudden expansion at the downstream end of the probe, results in the rapid drop of the gas velocity at the exit of the probe without a corresponding drop of the particle velocity. The results show that the proposed probe tip configuration can be effectively used to achieve a positive particle slip condition at the exit of the probe, with the particle velocity equal to or higher than that of the carrier gas.