bluuebunny/crossref_metadata_2025 huggingface dataset:
The critical velocity in pipeline flow of slurries
Authors: Oroskar Anil R. , Turian Raffi M.
Published: June 2004

In slurry transport, the critical velocity is defined as the minimum velocity demarcating flows in which the solids form a bed at the bottom of the pipe (bed load flows) from fully suspended flow. An analysis based on balancing the energy required to suspend the particles with that derived from dissipation of an appropriate fraction of the turbulent eddies is used to develop a correlation for prediction of the critical velocity. Comparison of the results with available experimental critical velocity data, relating to a rather wide variety of slurry systems, confirms that the present correlation does a superior job of prediction than all previously proposed critical velocity correlations.
Nucleation and evolution of slag droplets in coal combustion
Authors: Im Kwan H. , Chung Paul M.
Published: June 2004

Kinetics governing the nucleation and size variation of the slag droplets are first analyzed. Governing conservation equations are then formulated for the droplets and the surrounding gas‐vapor mixture. These equations are solved numerically for the environments representing a typical flow through the channel and diffuser of a coal fired, MHD, power generation system. The average droplet size, total number density and the droplet size distribution are found to be rather strongly influenced by the total slag mass fraction and the supersaturation ratio.
Mass transfer and adsorption in liquid full and trickle beds
Authors: Seirafi Hassan A. , Smith J. M.
Published: June 2004

Experimental breakthrough curves were determined for a liquid full and a trickle bed reactor in which benzene was adsorbed from water on small activated carbon particles at 298°K and 1 atm. The step function of benzene was introduced into the water feed and the response measured in the liquid effluent. Benzene transfer also occurred from the liquid feed to the gaseous feed of pure helium.

Moment analysis of data for liquid full conditions indicated that the first moment of the response curve could be used to obtain the adsorption equilibrium constant K for benzene on activated carbon. Comparison of results obtained by this new method with the K value determined from static equilibrium runs demonstrated the validity of the moment theory.

Analysis of the response curves for trickle bed operation showed that the liquid‐to‐gas mass transfer coefficient (ka)L could be evaluated from either the zero or first moment. Results were obtained in both the trickling flow and pulse flow regimes. Values of (ka)L in the pulse flow regime, which were not heretofore available were sharply higher than those for trickle flow.
Hindered settling of a suspension at low Reynolds number
Authors: Reed C. C. , Anderson John L.
Published: June 2004

The purpose of this paper is to analyze how the settling velocity of a dispersion of spherical particles (that is, drops of arbitrary viscosity) depends on concentration. The procedure used entirely avoids the divergent integrals which previous workers in this field have been forced to deal with and yields explicit formulas for the sedimentation velocity. These formulas, accurate to first order in the particle volume fraction, depend on both the physical characteristics of the particles (size, buoyant density, viscosity ratio) as well as on any long range forces (for example, electrical double layer repulsions or van der Waals attraction) which may exist between particles. Sample calculations are given for globular proteins subject to double layer repulsions and for micron size colloids which experience van der Waals attractions in addition to the electrostatics. In the latter case, it is shown how the Hamaker constant can be extracted from sedimentation data. The analysis is extended to more concentrated suspensions by assuming that the hydrodynamic interactions among particles are pairwise additive; comparison with published data shows this analysis to be reasonably accurate, even for dense suspensions, without any adjustable parameters.
Low shear viscosity of dilute polymer solutions
Authors: Chiou C. S. , Gordon R. J.
Published: June 2004

A modification of a viscometer originally proposed by Zimm and Crothers in 1962 is presented, which may be used to measure ultra low shear viscosity for highly dilute polymer solutions. This may provide useful information on polymer coil dimensions and relaxation time. Use of the low shear viscosity data leads to very large values of relaxation time induced by polymer addition to a concentration of only 2 to 3 wppm. This finding is consistent with the marked viscoelastic effects exhibited by these solutions.
Separation of krypton and xenon by selective permeation
Authors: Stern S. A. , Leone S. M.
Published: June 2004

The objective of this investigation was to study the separation of krypton and xenon from nuclear reactor atmospheres by selective permeation through silicone rubber capillaries. Effective permeability coefficients for pure krypton xenon, nitrogen, and oxygen were determined between 0 and 40°C and at pressure differences across the capillary walls (Δp) of up to 3.45 × 105 N/m2 (50 psi). The silicone rubber capillaries had an O.D. of 635 μm (0.025 in.) and an I.D. of 305 μm (0.012 in.), and were pressurized externally. The effective permeability coefficients decreased with increasing Δp, due to the elastic deformation of the capillaries, in general agreement with a deformation analysis of thick‐walled elastic tubes.

Gas separation studies were made with a Kr‐Xe‐N2‐O2 mixture in a permeator containing a bundle of silicone rubber capillaries. The permeator had an effective permeation area of 0.480 m2 (5.165 ft2) at a packing density of 4132 m2m3 permeator volume (1260 ft2/ft3), and was operated in a countercurrent mode. The separation studies were conducted at −10 and 20°C and at three Δp values. The separation achieved in the permeator at Δp's of 1.38 × 105 N/m2 (20 Ib/in.2) and 2.07 × 105 N/m2 (30 Ib/in.2) was in good agreement with that predicted from a theoretical model of a permeation stage with countercurrent flow. At 3.45 × 105 N/m2 (50 Ib/in.2), the separation approached that predicted from a “perfect mixing” model. This behavior probably was due to local collapses of the capillaries at weak spots in their walls, as was evidenced also by a sharp increase in the axial pressure drop inside the capillaries.
The calculation of density by the BWRS equation of state in process simulation contexts
Authors: Mills Martin B. , Wills M. John , Bhirud Vasant L.
Published: June 2004

The requirements of thermodynamic data predictors in process simulation applications are especially rigorous. The calculation of vapor and liquid density by the Benedict, Webb, Rubin, Starling equation of state has been reformulated to better satisfy these requirements; the necessary mathematical and programming techniques have been developed and are presented here. The resulting algorithm is believed superior for process simulation purposes.
Suboptimal stochastic control of a continuous latex reactor
Authors: Kiparissides Costas , MacGregor John F. , Hamielec Archie E.
Published: June 2004

A suboptimal control algorithm is derived for a continuous latex reactor subject to deterministic and stochastic disturbances to control the pathological behavior of the reactor. An extended Kalman filter based on an instantaneous local linearization technique is used to estimate the reactor states, and a quadratic performance index is used to derive the suboptimal feedback control law. This study successfully demonstrates the application of the multivariable control theory to the control of a simulated continuous latex reactor operating under limit‐cycle conditions. The mathematical model used for the control studies was previously developed and has been shown to describe the performance of an actual reactor system extremely well over its entire range of operation.
Diffusional influences on deactivation rates
Authors: Krishnaswamy S. , Kittrell J. R.
Published: June 2004

The interrelation between internal diffusion and concentration‐independent deactivation is examined using a simple mathematical model. Analytical procedures are developed for evaluating the performance of single catalyst particles in the presence of diffusion and deactivation. By incorporating time‐dependent effectiveness factors in design equations, reactor performance under the combined influence of diffusion and deactivation is predicted. By analogy to the effectiveness factor for non‐deactivating systems, the concept of a deactivation effectiveness factor is introduced.
High gradient magnetic filtration of fine particles from a gas stream
Authors: Gooding C. H. , Felder R. M.
Published: June 2004

Dust particles originally generated by two steelmaking processes were dispersed in an air stream and passed through a pilot‐scale high gradient magnetic filter. In accordance with theoretical predictions, the experimental results showed that collection was improved by increasing the depth or density of the steel wool filter, increasing the applied magnetic field, or decreasing the filtration velocity. Collection efficiency increased with particle size up to about 2 μm, above which the efficiency tapered off, apparently due to reentrainment effects. Collection efficiencies of greater than 99% were obtained, indicating that high gradient magnetic filtration may be a practical method of controlling particulate emission from processes in the iron and steel industry.
Vapor liquid equilibria up to 100 MPa: A new apparatus
Authors: Legret D. , Richon D. , Renon H.
Published: June 2004

A new static cell for vapor‐liquid equilibria up to 100 MPa between 233 and 433 K is presented. A detachable sampling microcell and a special chromatographic injector are used in a new sampling system suitable for gas chromatographic analysis of mixtures with high boiling components. The test system is N2—n‐Heptane at 305.45 K.
Liquid film flowing slowly down a wavy incline
Authors: Wang C‐Y
Published: June 2004

A viscous lamina of given mean thickness flows down a wavy incline. Assuming low Reynolds number and small perturbations due to the wavy striations, the velocity profiles and the free surface profile are determined. It is found that the amplitude and phase shift of the free surface depend, in a complicated manner, on the surface tension and the wave length and orientation of the wavy striations. The motion of a particle on the free surface experiences drift which is also a function of the surface tension, the amplitude, wave length and orientation of the wavy incline.
Regeneration of powdered activated carbon. Part II: Steam‐carbon reaction kinetics
Authors: Chihara Kazuyuki , Matsui Isao , Smith J. M.
Published: June 2004

The kinetics of the reaction between steam and spent activated carbon (from sucrose deposition) was studied at 1003 to 1123 K and 1 atm pressure. At these conditions some virgin carbon, upon which the sucrose was originally adsorbed, was also gasified. Rates of oxidation were essentially the same for spent and virgin activated carbon.

The kinetics data fit a Langmuir‐Hinshelwood equation, originally proposed for gasification of other types of carbon, with an activation energy of 2.3 × 105 J/mol.

Surface area and pore volume measurements indicated that the adsorption capacity of the original carbon could be completely restored by thermal regeneration followed by reaction with steam. However, some activated carbon is lost implying that there would be an optimum extent of steam gasification in a cyclical adsorption‐regeneration process.
The effect of pore structure on fluid‐solid reactions: Application to the SO2‐lime reaction
Authors: Bhatia S. K. , Perlmutter D. D.
Published: June 2004

The effect of varying pore structures on the kinetics of fluid‐solid reactions is investigated through the random pore model developed in prior papers (Bhatia and Perlmutter, 1980, 1981). By considering several idealized pore‐size distributions it is shown that a solid having a uniform pore size is intrinsically less reactive than one possessing a pore‐size distribution. For solids with bimodal pore size distributions optimal structures are shown to exist for which the reactivity is a maximum.

Numerical solutions were obtained to the model equations for various values of the parameters characterizing the pore structure, the diffusion, and the chemical kinetics. The results show that the conversion‐time behavior and the expected ultimate conversion can be very sensitive to variations in surface area and porosity for reactions accompanied by an increase in volume of the solid phase.

These findings are in agreement with experimental literature on the SO2‐lime reaction (Ulerich et al., 1978; Borgwardt and Harvey, 1972; Potter, 1969; Falkenberry and Slack, 1968) and the model is shown to fit the data of Borgwardt (1970), and of Hartman and Coughlin (1974, 1976). It is seen that this reaction is diffusion controlled under the conditions of Hartman and Coughlin, in consonance with their own finding using the grain model, and a prior Pigford and Sliger (1973) interpretation. The temperature behavior of the diffusion coefficient in the product layer suggests the participation of an activated process, possibly a solid state diffusion step.
A random pore model for fluid‐solid reactions: II. Diffusion and transport effects
Authors: Bhatia S. K. , Perlmutter D. D.
Published: June 2004

The prior random pore model for kinetically controlled fluid‐solid reaction (Bhatia and Perlmutter, 1980) is generalized to include transport effects arising from boundary layer, intraparticle, and product layer diffusion. Numerical solutions are presented for a variety of conditions. The results show that the rate and surface area maxima predicted in the kinetic regime are shifted to lower conversions as intraparticle or product layer diffusional resistances increase. In addition, with increasing temperature a decrease in the overall reaction surface is predicted, in agreement with experimental findings (Kawahata and Walker, 1962).

For reactions accompanied by an increase in the volume of the solid phase, it is shown that incomplete conversion may be expected, the ultimate conversion decreasing with an increase in the intrapellet diffusional resistance. Optimal temperatures for such reactions are also identified.
Interpretation of surface flow phenomenon of adsorbed gases by hopping model
Authors: Okazaki Morio , Tamon Hajime , Toei Ryozo
Published: June 2004

The mechanism of surface flow of adsorbing gas molecules through the porous adsorbent is interpreted, and a new hopping model is derived by separately taking into account the hopping behaviors of monolayer and multilayer molecules. The reported experimental results containing the data measured here are correlated well. Finally, some considerations are given to the two experimental constants appearing in the model.
Flow mechanism of adsorbate through porous media in presence of capillary condensation
Authors: Tamon Hajime , Okazaki Morio , Toei Ryozo
Published: June 2004

The flow mechanism of adsorbable gas through the porous adsorbent in the presence of capillary condensation is interpreted, and a new transport model is derived by separately taking into account the hopping behavior of adsorbed molecules in the adsorbed phase and the viscous flow of capillary condensate. Surface flow coefficients including the contribution of capillary flow calculated with this model agree with published experimental data.
SO2 absorption into aqueous solutions
Authors: Chang C. S. , Rochelle G. T.
Published: June 2004

The absorption rate of SO2 from a gas mixture of SO2 and N2 into pure water, HCl, and NaCl solutions has been measured at 25°C in a continuous stirred vessel with an unbroken gas‐liquid interface. The rates of the liquid‐phase mass transfer are accurately modeled by the theory of surface renewal with the instantaneous, reversible hydrolysis of dissolved SO2. The theory and results are applicable to SO2 absorption from waste gases.
Laminar condensation heat and mass transfer to a moving drop
Authors: Chung J. N. , Ayyaswamy P. S.
Published: June 2004

This paper presents numerical solutions to the nonlinear, coupled boundary‐layer equations governing laminar condensation heat and mass transfer in the vicinity of the forward stagnation point of a spherical cold water droplet translating in a saturated mixture of three components. The environment surrounding the droplet is composed of a condensable (steam), a noncondensable and nonabsorbable (air), and a third component which is noncondensable but absorbable (Elemental Iodine, for example). The dispersed and the continuous phases have been treated simultaneously. Results obtained here show excellent agreement with experimental results where available. An important conclusion is that for laminar condensation on a freely falling droplet, for a given thermal driving force and noncondensable gas concentration in the bulk, the dimensionless heat transfer decreases with increasing saturation temperature of the outside medium.
A single, particle‐size model for sulfur retention in fluidized bed coal combustors
Authors: Lee D. C. , Georgakis Christos
Published: June 2004

A reactor model is presented to calculate the sulfur retention and SO2 emission of a fluidized‐bed coal combustor with absorption of SO2 by limestone or dolomite. It is based on the two‐phase theory of fluidization and a two parameter simplified rate expression for the sulfation reaction. Both parameters can be determined by experimental reaction rate measurements. In the overall reactor model, an average size is assumed for all the stone particles in the bed. Sulfur retention is found to be dependent on only three dimensionless parameters. Comparisons with experimental measurements indicated that the model predicts satisfactorily the dependence of sulfur retention on the Ca/S ratio, sulfur content of the coal, excess air, gas residence time, and sorbent type.
Liquid‐Liquid dispersion in turbulent couette flow
Authors: Leonard R. A. , Bernstein G. J. , Pelto R. H. , Ziegler A. A.
Published: June 2004

A dimensionless dispersion number was developed to characterize liquid‐liquid dispersions created in turbulent Couette flow with respect to their subsequent coalescence in a settling zone. For a given solvent pair and continuous phase, the dispersion number is relatively constant over a wide range of operating and dimensional parameters. Because of this, the dispersion number can be used for the design and scale‐up of liquid extraction equipment with discrete stages.
Convective solids settling induced by a buoyant phase
Authors: Fessas Y. P. , Weiland R. H.
Published: June 2004

Quantitative measurements of the effect of a third phase of buoyant solid particles on the settling rates of suspensions of heavy particles are reported. It is found that for a wide range of concentration of both buoyant and heavy particles, the settling rates of both solid phases are greatly increased. If the phases are dilute, the settling velocities of both are retarded. The total settling time of heavy particles can be halved, but only under conditions that the light phase is unaccelerated. This suggests that small gas bubbles would form a more satisfactory buoyant phase. The high concentrations of thickened suspensions which result from the acceleration process are also reported.
Effects of perforated partition plate on mixing characteristics of horizontal stirred vessel
Authors: Ando Koji , Shirahige Minoru , Fukuda Takashi , Endoh Kazuo
Published: June 2004

To reduce backmixing in the flow‐type horizontal stirred vessel, a perforated partition plate was attached and the effects of shape of plate on the mixing characteristics were studied under various operating conditions. Results were analyzed in terms of mixing models to evaluate the extent of preventing backmixing. It enabled us to estimate the extent of back flow at the perforated partition plate from power consumption.
Employment of vapor pressure data in the description of vapor‐liquid equilibrium with direct method
Authors: Morbidelli Massimo , Carrà Sergio
Published: June 2004

A procedure for inserting vapor pressure data in the equations of state is presented. It provides a straightforward scheme for the extension of direct methods to the study of phase equilibria of polar mixtures and of solutions containing nonvolatile electrolytes. Some examples of application are also given.
Design of advanced process controllers
Authors: Palmor Z. J. , Shinnar R.
Published: June 2004

This paper deals with defining the relation between modeling of process units and controller design. In the process industries, it is often difficult to obtain accurate process models. It is shown that advanced algorithms such as dead‐time compensators require more detailed process information for design than do with PI and PID controllers. A method is described to systematically evaluate the relation between process identification and controller design, stability, and performance. It is shown that conventional gain and phase margins do not provide proper safety margins for dead‐time compensators and optimal controllers. Methods for safe design of dead‐time compensators are derived, and the approach could be useful in a wide class of problems.

To illustrate the approach presented, the design of PI controllers by conventional methods is analyzed. The conditions, as well as the exceptions, are specified in which methods such as described by Ziegler and Nichols or Cohen and Coon will give good results. It is shown that for any stable nonlinear system with an input/output function y = G*p(u), a linearized design function G′pd can be constructed and identified that guarantees stability and reasonable performance of the controller (Eqs. 21 and 22 and Figures 4–7) over a wide range of operating conditions. A rigorous framework for identifying the exceptions and understanding the reason why such methods work is presented.
A semi‐empirical adsorption equation for single component gas‐solid equilibria
Authors: Sircar Shivaji , Gupta Ramesh
Published: June 2004

A semi‐empirical adsorption equation is derived and tested against published equilibrium sorption data on various types of systems. The equation is designed to satisfy the constraints imposed by the physics and the thermodynamics of the adsorption systems. It can describe the Type I and the Type III isotherms as well as their combinations. The model does not restrict the nature of the isosteric heat of adsorption to simplified forms such as a constant or a linear function of the surface coverage. This restriction is primarily responsible for limited applications of the published theories. Empirical equations relating the isosteric heat of adsorption and the surface excess variable are proposed.
Influence of turbulence on mass transfer between a liquid and a solid sphere
Authors: Sandoval‐Robles J. G. , Delmas H. , Couderc J. P.
Published: June 2004

Electrochemical measurements of overall mass transfer rates from a single sphere have been performed in a highly turbulent liquid. The increase in mass transfer rate due to turbulence has been shown to be more important at high Reynolds number and high turbulence intensity. Various equations of correlation have been proposed between the overall Sherwood number, the Reynolds number and turbulence intensity, the simplest one beingA correct agreement has been found with previous heat or mass transfer results between a gas and a sphere.
Evaluation of liquid‐solid contacting in trickle‐bed reactors by tracer methods
Authors: Mills P. L , Dudukovic M. P.
Published: June 2004

The use of dynamic (tracer) methods for the evaluation of liquid‐solid contacting and holdup in trickle‐bed reactors is illustrated. It is shown that both the fraction of external catalyst area wetted and the fraction of total catalyst wetted by liquid can be obtained. External contacting efficiency and dynamic liquid saturation are correlated in terms of the appropriate dimensionless groups over the range of variables typical for trickle‐flow operation. The relationship between catalyst contacting efficiency and catalyst utilization is outlined.
A temperature swing process for hydrogen isotope separation
Authors: Hill F. B. , Wong Y. W. , Chan Y. N. I.
Published: June 2004

Experiments on the separation of hydrogen isotopes were conducted using vanadium hydride in a temperature swing process. Process behavior followed trends predicted by an equilibrium theory of process operation, but was modified by a kinetic isotope effect and by finite rates of hydrogen absorption and isotope exchange.
Purification of phenolic wastewater by parametric pumping: Nonmixed dead volume equilibrium model
Authors: Costa C. A. V. , Rodrigues A. E. , Grevillot Georges , Tondeur Daniel
Published: June 2004

A new process for purification of phenolic wastewaters by parametric pumping is presented.

An equilibrium (linear) model for nonmixed dead volumes thermal direct mode parametric pumping is developed and the influence of bottom and top dead volume magnitudes on transient separation is analyzed.

Analytical solutions for batch, continuous and semicontinuous operations are presented.

Experimental data on the system phenol/water‐Duolite ES861 include equilibrium isotherms at 20°C and 60°C and parapump runs for the cases mentioned above.
Photopolymerization in an isothermal and continuous stirred tank reactor: Concentration stability
Authors: Chen H. T. , Kuan C. N. , Lin D. J.
Published: June 2004

An investigation of photopolymerization in an isothermal and continuous stirred tank reactor (CSTR) was made. The existence of multiple steady states induced by gel effects was demonstrated theoretically and experimentally. This multiple steady state problem is presented in relation to reactor stability and control. Also, the relative behavior of the batch and CSTR systems is discussed.
Studies of mold filling and curing in the reaction injection molding process
Authors: Castro J. M. , Macosko C. W.
Published: June 2004

A model is developed for pressure rise, extent of reaction and temperature changes during filling and curing in thin rectangular molds for the reaction injection molding (RIM) process. The predictions of the model are shown to be in good agreement with experimental results obtained for several intrumented molds using polyurethane RIM chemical systems. The relevant dimensionless groups are identified. Criteria for good mold filling are developed.
Prediction of diffusion coefficients for polymer‐solvent systems
Authors: Duda J. L. , Vrentas J. S. , Ju S. T. , Liu H. T.
Published: June 2004

A revised version of a recently proposed free‐volume theory of polymer‐solvent diffusion is introduced and evaluated using experimental diffusivity data collected over wide temperature and concentration ranges. The theory accurately predicts the large temperature and concentration variations typically observed for polymer‐solvent diffusion coefficients.
Effect of micelle formation on chromatographic movement of surfactant mixtures
Authors: Harwell J. H. , Helfferich F. G. , Schechter R. S.
Published: June 2004

Solutions are presented for equations which describe the chromatographic transport of binary surfactant mixtures. The formation of micelles in the bulk fluid is taken into account. The effects of micellization on the behavior of surfactant pulses are illustrated by solutions for specific cases. Schemes are presented for offsetting the tendency of surfactant pulses to undergo chromatographic separation because of preferential adsorption of the surfactants on the solid substrate. These schemes take advantage of the effects of micelle formation. Generalizations for n‐component surfactant systems are outlined.
Influence of vapor entrainment on distillation tray efficiency at high pressures
Authors: Hoek P. J. , Zuiderweg F. J.
Published: June 2004

A recent publication of Fractionation Research Inc. (FRI) (Sakata and Yanagi, 1979) provides experimental evidence that tray efficiency initially rises with increasing pressure, reaches a maximum value, and then decreases again at very high pressures. It is shown in this paper that at these high pressures, significant amounts of vapor can be entrained with the downflowing liquid, e.g., abt. 50 mol per 100 mol liquid at 2,760 kPa. A new model is developed to determine the effect of vapor entrainment on tray efficiency. It is shown that the experimentally observed loss of tray efficiency corresponds with the entrainment rates found at high pressures.
Local drag reduction due to injection of polymer solutions into turbulent flow in a pipe. Part I: Dependence on local polymer concentration
Authors: McComb W. D. , Rabie L. H.
Published: June 2004

Aqueous solutions of drag‐reducing polymers were injected into turbulent water flow in a pipe. The injection point was situated where the flow was well‐developed. Thus, subsequent steamwise variations in pressure drop were due to the injected polymer spreading out across the pipe. The axial development of local drag reduction was monitored by a series of closely‐spaced pressure tappings. The corresponding radial dispersion of the injected polymer, as it travelled downstream, was assessed by sampling the flow at various points.

Local drag reduction, due to either point injection at the centerline or injection through a slot in the wall, was found to increase with distance downstream. This increase was related to the streamline increase of polymer concentration in a narrow annulus near the pipe wall. It was tentatively concluded that the effective annulus was bounded by 15 ≤ y + ≤ 100, in agreement with previous deductions from less direct evidence.
Local composition model for excess Gibbs energy of electrolyte systems. Part I: Single solvent, single completely dissociated electrolyte systems
Authors: Chen Chau‐Chyun , Britt H. I. , Boston J. F. , Evans L. B.
Published: June 2004

An electrolyte local composition model is developed for excess Gibbs energy, which is assumed to be the sum of two contributions, one resulting from long range electrostatic forces between ions and the other from short range forces between all the species. The validity of the model is demonstrated for systems emcompassing the entire range from molecular liquid to fused salt.
Holographic and photographic studies of high‐quality steam‐water critical flow
Authors: Ju Yi‐Hsu , Moulton R. W. , Garlid K. L.
Published: June 2004

High‐quality (95%) steam‐water critical flow through a straight pipe was studied using high‐speed photographic and holographic techniques. The results indicate that most of the water exists as a discontinuous or continuous thin film which flows along the wall with a speed much slower than that of the steam. This results in slip ratios higher than those reported before. Although a separated flow model would seem to describe the actual flow situation more closely than other models, the assumption of thermal equilibrium between phases and the fact that the flow is not separated except close to the exit plane are probably explanations for differences in slip ratios obtained in this study from those predicted.
Correlation of phase‐separation data for coal‐conversion systems
Authors: Watanasiri Suphat , Brulé M. R. , Starling K. E.
Published: June 2004

A multiparameter corresponding‐states correlation is applied to describe fossil‐fluid vapor/liquid‐equilibrium behavior needed to design separation and other process units in coal‐liquefaction plants. Data for both defined and undefined fluids pertinent to coal liquefaction are utilized in correlation development. The procurement of these data requires a thorough evaluation and study of the needs for additional data to improve correlations. These needs are systematically outlined in the context of the level of predication capability that can be achieved using the currently available data base.

A conformal‐solution model is applied to describe the behavior of many defined binary and ternary coal‐solvent systems. The correlation is then extended to undefined systems such as those encountered in the Exxon Donor Solvent process. Correlation results are reported and correlation limits are assessed.
Batch extraction with liquid surfactant membranes: A diffusion controlled model
Authors: Ho W. S. , Hatton T. A. , Lightfoot E. N. , Li N. N.
Published: June 2004

A model of diffusion controlled mass transfer in liquid surfactant membranes is developed for uniform emulsion globules having no internal circulation. The solute is assumed to react instantaneously and irreversibly with the internal reagent at a reaction surface which advances into the globule as the reagent is consumed. A perturbation solution to the resulting non‐linear equations is presented. In general, the zero‐order, or pseudo‐steady state solution alone often gives an adequate representation of the process. Experimental data on the batch extraction of phenol from waste water are in good agreement with the model predictions.
General correlation of the initial collection efficiency of granular filter beds
Authors: Pendse Hemant , Tien Chi
Published: June 2004

A generals correlation for the prediction of the initial collection efficiency of granular filter beds is proposed. The correlation is based on the results obtained from trajectory calculation and the comparison between the numerical results and available experimental data. The correlation includes all the pertinent dimensionless groups and agrees with reported data within experimental accuracy.
Thinning of a liquid film as a small drop or bubble approaches a fluid–fluid interface
Authors: Lin Cheng‐Yuan , Slattery J. C.
Published: June 2004

When a small drop or bubble approaches a fluid–fluid interface, a thin liquid film forms between them, drains, until an instability forms and coalescence occurs. A hydrodynamic theory is developed for the first portion of this coalescence process: the drainage of the thin liquid film while it is still sufficiently thick that the effects of London‐van der Waals forces and electrostatic forces can be ignored. The time rate of change of the film profile is predicted, given only the drop radius and the required physical properties. Comparisons are offered with the limited experimental data available.
Interaction second virial coefficients and binary interaction parameters for the CO2  C2H6 systems between 250 and 300 K
Authors: Holste J. C. , Young J. G. , Eubank P. T. , Hall K. R.
Published: June 2004

We have determined the interaction second virial coefficients (B12) for the CO2  C2H6 system between 250 and 300K using a Burnett‐isochoric apparatus. The technique follows a procedure suggested by Hall and Eubank (1973) and extended by Holste et al. (1980). Combined errors for B12 are within 1.2 cm3/mol. In addition, values for the binary interaction parameter k12 calculated from our B12 values show difinite temperature dependence.
A thermodynamic approach to multicomponent distillation system synthesis
Authors: Naka Yuji , Terashita Masayuki , Takamatsu Tekeichiro
Published: June 2004

This paper shows a synthesis method of multicomponent distillation systems with heat integration based on the available energy concept. With this method, the problem of synthesizing the heat integrated distillation systems in which there are heat source and sink streams supplied from other processes can be solved so as to minimize the process utilities. Moreover, since the system synthesis is executed in the (1 – T0/T) vs. Q diagram, it is possible to visibly represent the physical meanings of the computing process.
Modeling of noncatalytic gas‐solid reactions
Authors: Ramachandran P. A. , Doraiswamy L. K.
Published: June 2004

This paper presents a critical review of the developments in the mathematical modeling of gas‐solid noncatalytic reactions with particular emphasis on recent trends in the subject. A number of models proposed for analyzing this class of reactions have been reviewed with a fairly detailed discussion of the methods of incorporating structural changes which occur in the solid with the progress of reaction. The present status on the modeling of various types of complex gas‐solid reactions is reviewed. Also the paper points out a number of areas in which future research may be needed. The review concludes with a critical discussion on the type of experimental data necessary for model verification and some comments on the choice of model for a given system.
Stripping of carbon dioxide from monoethanolamine solutions in a packed column
Authors: Weiland R. H. , Rawal M. , Rice R. G.
Published: June 2004

A procedure using only fundamental physico‐chemical data is developed for the design and analysis of packed columns used for solvent recovery in gas purification processes involving chemical reaction. The results of 173 experiments on the mass transfer performance of a pilot‐scale regenerator stripping CO2 from loaded monoethanolamine solutions are reported and compared with model predictions. Anomolous responses of the overall mass transfer coefficient to changes in process conditions are observed and explained by the process model which is found to predict correctly both the magnitude of the coefficient and its response.
Optimum dimensions for pipeline mixing at a T‐junction
Authors: Forney L. J. , Lee H. C.
Published: June 2004

Conditions are identified which insure optimum pipeline mixing at a T‐junction. Analytical expressions, that result from detailed measurements of both near and far‐field momentum‐dominated jet trajectories in a crossflow, are renormalized in terms of pipe coordinates. It is demonstrated that a simple scaling law exists for the limiting geometry of either large or small jet‐to‐pipe diameter ratios. The scaling laws are shown to accurately correlate existing data for each limiting geometry.
Scrubbing of gaseous nitrogen oxides in packed towers
Authors: Counce R. M. , Perona J. J.
Published: June 2004

Nitrogen oxide removal efficiencies of up to 97% were obtained in tests using columns packed with Intalox saddles. These studies were conducted at atmospheric pressure with water as the scrub solution and nitrogen oxide feed concentrations of up to 10%. A mathematical model based on mass‐transfer, kinetic, and equilibrium data is presented; calculated removal efficiencies using this model agree very well with the experimental data.
Measurements of the rise velocities of bubbles, slugs and pressure waves in a gas‐solid fluidized bed using pressure fluctuation signals
Authors: Fan L. T. , Ho Tho‐Ching , Walawender W. P.
Published: June 2004

The rise velocities of bubbles, slugs and pressure waves in a fluidized bed have been measured on‐line through the use of pressure transducers coupled with the cross‐correlation technique. Sand and glass beads with different particle sizes were tested. Effects of the gas flow rate and column diameter on the rise velocities of bubbles and slugs were investigated. The results were correlated with two models developed in this work and were compared with the data obtained by other investigators.
Vapor‐liquid equilibrium constants at infinite dilution determined by a gas stripping method: Ethane, propane, n‐butane, n‐pentane in the methane‐n‐decane system
Authors: Legret D. , Desteve J. , Richon D. , Renon H.
Published: June 2004

A new apparatus to measure partition coefficients K at infinite dilution up to 200 105 Pa and 423 K is described. Measurements of the systems: (1) methane‐ethane‐n‐decane and methane‐propane‐n‐decane at 294.25 K; and (2) methane‐n‐butane‐n‐decane at 344.25 K illustrate the reproducibility and good agreement with literature data. In addition, new data were obtained for the system methane‐n‐pentane‐n‐decane at 344.25 K up to 101 105 Pa.
Selective electrorefining with liquid membranes
Authors: Gökalp Mehmet , Hodgson K. T. , Cussler E. L.
Published: June 2004

Liquid membranes containing macrocyclic polyethers can be used to electrorefine metals. This purification depends on the selective reaction of the polyether and the metal cation to produce a charged product. The amount of this product is found to be proportional to the square root of the amount of polyester present. Results for silver and copper purification illustrate the ideas involved.
Close‐clearance helical impellers: A physical model for newtonian liquids at low Reynolds numbers
Authors: Chavan V. V.
Published: June 2004

With simple hydrodynamic concepts, a physical model is developed to describe the flow at the wall close to the impeller blade. The parameters of this model were evaluated from the large amount of data on power consumption and checked with some independent data on velocity profiles. Together with the physical insight provided by the model, it helped to obtain general relationships for power and heat transfer coefficients. Equations for the latter were developed using Lévêque's approximation. Agreement between the predicted results and the literature data of several independent studies was rather good. A method to analyze mixing or blending results is also suggested.
Reduced‐order steady‐state and dynamic models for separation processes. Part I. Development of the model reduction procedure
Authors: Cho Y. S. , Joseph B.
Published: June 2004

One of the major difficulties with mathematical models of staged separation systems is the large dimensionality of the process model. This paper is concerned with simple (reduced‐order) steady‐state and dynamic models for processes such as distillation, absorption and extraction. The model reduction procedure is based on approximating the composition and flow profiles in the column using polynomials rather than as discrete functions of the stages. The number of equations required to describe the system is thus drastically reduced. The method is developed using a simple absorber system. In the second part of this paper, the application of the method to nonlinear multicomponent separation systems is demonstrated.
Pressure drop for cocurrent downflow of gas‐solids suspensions
Authors: Kim J. M. , Seader J. D.
Published: June 2004

Pressure drop for a gas‐solids suspension flowing concurrently downward in a 13‐mm inside‐diameter tube was investigated using 329‐micron spherical glass beads in air. The gas Reynolds number varied from 0 to 30,000 with solids‐loading ratios of up to 20 at a gas Reynolds number of 10,000. The frictional pressure drop for downflow was found to be a weaker function of the solids‐loading ratio than the upflow case using data reported in the literature. Empirical correlation of the two‐phase friction factor, in terms of the gas Reynolds number and a dimensionless parameter, CDEPD/[(1 – Ep)dp], showed that at high solids loadings, particles tend to stabilize the suspension flow. The dimensionless parameter seems to be applicable to a universal pressure drop correlation for solids‐fluid systems, but requires further investigation.
Mechanisms for solids ejection from gas‐fluidized beds
Authors: Levy E. K. , Caram H. S. , Dille J. C. , Edelstein Sergio
Published: June 2004

The bubble eruption process was studied in two‐ and three‐dimensional (2D and 3D) beds using a high‐speed video system for flow visualization. The results show the existence of four different ejection mechanisms; one occurring with singlebubble eruptions in both 2D and 3D beds, two others occurring in 2D and 3D beds with two bubbles coalescing at the bed‐free surface, and the fourth occurring only in 3D beds with bubbles coalescing at the bed surface.
Mechanism of pore formation in reverse osmosis membranes during the casting process
Authors: Neogi P.
Published: June 2004

The process of pore formation during the casting of reverse osmosis membranes is analyzed. The process consists of two steps. The first step is the evaporation step, where the cast polymer solution is allowed to dry for 1 ∼ 100 s. The second step is the gel formation step, where the cast is soaked in water leaving behind the membrane in form of a gel. The evaporation step gives rise to a thin (∼0.1 μm) skin of high density and very small pores which is chiefly responsible for desalination. The gel forms the backing (∼100 to 250 μm) and contains large pores.

It is shown that low evaporation rates accompanied by shrinkage during evaporation gives rise to an instability leading to the formation of the skin region. The evaporation effect is fast, is confined to the skin region, and gives rise to very small pores. The gel formation is shown to be a very slow process which cannot interfere with the skin formation due to the vast differences in their rates of formation. It also gives rise to larger pores. All key features of the above experimental observations are explained.

The kinetics of the process depend on the diffusion coefficients D and Dp of the solvent and the polymer. However, the main factor is the solution chemistry of the polymer‐solvent system which controls both the effectiveness of the skin and the gel formed. For the first time, the relevant thermodynamic parameters which determine the extent and sizes of pore formation have been obtained.
Model of continuous dispersive flow with interactive deadwater and application to gas‐phase flow in rotary calciners
Authors: Spencer B. B. , Whatley M. E. , Watson J. S.
Published: June 2004

A continuous flow model is developed which describes flow through a vessel in which the fluid undergoes axial dispersed plug flow and some of the flid is held back in a deadwater zone. The first three moments of the concentration‐time curve are related to the three parameters of the model, and an equation is presented to predict the outlet concentration from the vessel as a function of time for an impulse input. The model is used to analyze experimental gas‐phase residence‐time distribution (RTD) data collected from a small rotary calciner operated at room temperature. These data are well represented by the model.
Variable volume enzyme reactor with ultrafiltration swing: A theoretical study on CSTR case
Authors: Kim In Ho , Chang Ho Nam
Published: June 2004

A new membrane enzyme reactor system is proposed, and its performance is analytically and numerically examined by operational modes. This membrane‐separated, two‐compartmental reactor is operated in a cyclic manner such that ultrafiltration swing is induced either by a pulsatile flow or by an alternating pressure difference. Substrate and product solutins are permeable to the membrane while enzyme is impermeable. In one reservoir, enzyme solution is stored into which substrate is supplied by diffusion‐coupled ultrafiltration and product is removed by the same mechanism into the substrate compartment, which is similar to CSTR in view of fluid mixing and continuous inlet‐outlet flows, but differs from CSTR in a sense that reaction takes place only in the enzyme compartment.

The governing model equations are derived and their analytical solutions are obtained for fast reaction and high ultrafiltration with first‐order kinetics. In addition, nonlinear Michaelis‐Menten kinetics problem is solved numerically. As a result, we have found that the system can increase the conversion substantially compared with previous diffusion‐moderated enzyme reactors where diffusion very often can limit the extent of conversion.
Heat and power networks in process design. Part II: Design procedure for equipment selection and process matching
Authors: Townsend D. W. , Linnhoff Bodo
Published: June 2004

In Part I, criteria for heat engine and heat pump placement in chemical process networks were derived, based on the “temperature interval” (T.I) analysis of the heat exchanger network problem. Using these criteria, this paper gives a method for identifying the best outline design for any combined system of chemical process, heat engines, and heat pumps. The method eliminates inferior alternatives early, and positively leads on to the most appropriate solution. A graphical procedure based on the T.I. analysis forms the heart of the approach, and the calculations involved are simple enough to be carried out on, say, a programmable calculator. Application to a case study is demonstrated.

Optimization methods based on this procedure are currently under research.