bluuebunny/crossref_metadata_2025_split huggingface dataset:
An approximate mathematical model for three‐phase multistaged separators
Authors: Ferraris G. Buzzi , Morbidelli M. 
Published: June 2004

AbstractAn approximate method is developed for the simulation of three‐phase, multistaged multicomponent separators in which one of the two liquid phases can be regarded as being constituted of almost one component only.Comparisons with the complete three‐phase model shows a large reduction of the required computation time and a satisfactory agreement of the obtained results.
Control system synthesis strategies
Authors: Govind Rakesh , Powers G. J. 
Published: June 2004

AbstractThis paper is concerned with an important aspect of process control design—synthesis of the control structure. Synthesis of control structures has long been practiced by experienced control engineers, who relied on intuition, insight and judgment to pick a feasible solution from the vast number of alternatives that were possible. This paper describes a systematic procedure to generate these alternatives based on the cause‐and‐effect representation of the process. The final product is a set of control schemes from which the final system may be selected or evolved. The work is significant in that it is the first attempt to apply non‐numerical problem‐solving techniques to the problem of synthesizing process control structures. As such, it gives a new way of studying and teaching chemical process control.
Mixing and fluid dispersion of viscous liquids
Authors: Ranz W. E. 
Published: June 2004

AbstractA model based on extension and secondary motions of striations in a deforming flow is used to predict details of the mixing and dispersion of viscous liquids. Generally, extension of intermaterial area and interfacial surface occurs in stagnation regions, and breakup ensues when the striated flow has left such a region or has time to form unmixing regions of smaller scale in the stretching flow. Complex criteria for the types of mixing anticipated are based on differences in viscosity, differences in density, striation scale, rate of stretch, and, for various degrees of immiscibility, interfacial tension.
Cyclic regeneration of activated carbon in fluidized beds
Authors: Chihara K. , Suzuki M. , Smith J. M. 
Published: June 2004

AbstractCyclic thermal regeneration of powdered activated carbon containing adsorbed sucrose was studied in fluidized beds at 1151° K and 101.3 kPa (1 atm). The regeneration process consists of three steps: (1) drying, (2), thermal decomposition, and (3), gasification of residual carbon with steam. The maximum restoration of adsorption capacity (98.5% recovery after each regeneration) was obtained when gasification removed an amount of carbon equal to the residual adsorbed carbon after thermal decomposition. It was verified that the time required to attain optimum regeneration could be determined from available kinetics data for the steam‐carbon reaction. For our sucrose‐activated carbon system this time was about 180 s at 1151°K.
A study of the volumetric and phase behavior of binary systems. Part II. Vapor‐liquid equilibria and azeotropic states of propane‐perfluorocyclobutane mixtures
Authors: Barber J. R. , Kay W. B. , Teja A. S. 
Published: June 2004

AbstractMeasurement of vapor‐liquid equilibria and azeotropic states of propane‐perfluorocyclobutane mixtures are reported in this paper. The propane‐perfluorocyclobutane system exhibits positive azeotropic behavior which persists in the critical region of the system. The prediction of vapor‐liquid equilibria and of the locus of azeotropic points using an extended corresponding states principle is also reported. The predictions require information obtained solely from a study of the critical states of the system.
Mixing of single and two phase systems: Power consumption of impellers
Authors: Gray D. J. , Treybal R. E. , Barnett S. M. 
Published: June 2004

AbstractThe mechanical power consumed in agitating aerated and nonaerated aqueous phases was measured and correlated using the data of previous investigators. The correlation is for a flat bladed turbine operating within the turbulent regime in fully baffled vessels. The accuracy of the predictions and the range of geometrical variations and equipment sizes support the use of the correlation for scaleup opreations.
Kinetics of coal drying‐decomposition
Authors: Karsner G. G. , Perlmutter D. D. 
Published: June 2004

AbstractA series of seven coals of different ranks and from various locations were heated in an inert atmosphere under relatively mild conditions to measure the rates of gas evaporation. Samples crushed to various fractions in the particle size range −6+50 U.S. mesh were studied at temperatures in the range of 150 to 300°C. The results show that: (1) most water is released at 100°C, evidently an evaporation process, (2) CO2 is evolved at 150°C and above, and (3) CO is evolved at 250°C and above. An interpretive model was developed to fit the CO2 production rate and kinetic constants were obtained. Gas evolution rates are independent of particle size for the most porous coals, but vary among coals, depending on both chemical composition and physical structure. A 15% loss in heating value was incurred during drying and subsequent oxidation when the pretreatment temperature was increased from 150 to 225°C.
A non‐Fickian model of packed‐bed reactors
Authors: Chang Hsueh‐Chia 
Published: June 2004

AbstractA model for packed‐bed reactors with dispersion is derived rigorously via the volume averaging approach. Though it is quantitatively more consistent with experimental data, it requires less computational efforts than the prevalent Fickian model. The adverse effects of dispersion on conversion are demonstrated both numerically and analytically using the new model.
Kinetics of high‐temperature carbon gasification reaction
Authors: Desai N. J. , Yang R. T. 
Published: June 2004

AbstractA simple technique is developed and is used to measure simultaneously the overall rate and the depth of the reaction zone in the porous solid. It is shown that by using some simple models, one may calculate the intrinsic rate constant and the pore diffusivity from the overall rate and the penetration depth. Models which allow for a varying pore diffusivity according to a linear porosity profile are presented, and have been shown more satisfactory than the constant diffusivity models of Thiele and of Zeldovich when applied to the high temperature carbon‐carbon dioxide reaction.
Rate of protein absorption and desorption on cellulosic ion exchangers
Authors: Graham Edgar E. , Fook Chen F. 
Published: June 2004

AbstractBoth equilibrium and rate studies were made for the adsorption and desorption of Bovine Serum Albumin (B.S.A.), Fraction V, from dilute solutions using a new cellulose based ion exchange resin. Using the equilibrium data and a simple two‐film theory to describe the rate data it was shown that during the initial perioid of adsorption the rate was controlled by film diffusion, after which it was controlled by intraparticle diffusion. The desorption was largely intraparticle diffusion controlled except for a very short surface desorption step. It is suggested that the model could be used to describe other protein adsorption/ion exchange processes.
Effect of organic acid additives on SO2 absorption into CaO/CaCO3 slurries
Authors: Chang Chung‐Shih , Rochelle G. T. 
Published: June 2004

AbstractThe absorption rate of sulfur dioxide from a gas mixture of SO2 and N2 into aqueous acetic acid and adipic acid solutions at pH 4 to 6 has been measured at 25°C in a continuous stirred vessel with an unbroken gas‐liquid interface. The experimental data have been modeled by approximate surface renewal theory with multiple equilibrium reactions. The model has been used to evaluate the relative effectiveness of eleven organic acid additives at typical limestone scrubber conditions. Adipic, sulfopropionic, sulfosuccinic, and hydroxypropionic acids appear to be the most promising alternatives.
Diffusional influences on deactivation rates: Experimental verification
Authors: Krishnaswamy S. , Kittrell J. R. 
Published: June 2004

AbstractThe internal diffusion‐deactivation model of Krishnaswamy and Kittrell (1981a) is tested and verified by using laboratory deactivation data on the decomposition of hydrogen peroxide by immobilized catalase. Through an analysis of the influence of diffusional phenomena on the deactivation kinetics, estimates of the intrinsic deactivation rate constant have also been provided.
A kinetic model of nitric oxide formation during pulverized coal combustion
Authors: Mitchell J. W. , Tarbell J. M. 
Published: June 2004

AbstractA mathematical model of nitric oxide (NO) formation during pulverized coal combustion was developed from a proposed kinetic mechanism involving 12 overall chemical reactions. Most significantly, the model describes the complex conversion of coal bound nitrogen compounds to NO during combustion. The predictions of the model compare favorably with literature data obtained in well defined laboratory combustors firing gaseous fuels doped with organic nitrogen additives, as well as with data obtained in laboratory coal combustors. The predictions of the model are in qualitative agreement with trends observed in practical coal combustors.
Three‐dimensional, randomized, network model for two‐phase flow through porous media
Authors: Lin Cheng‐Yuan , Slattery John C. 
Published: June 2004

AbstractA structural model for a porous medium in the form of a randomized, three‐dimensional network is developed that can be used to calculate permeability, capillary pressure as measured under static conditions and during steady‐state flows, and relative permeabilities as measured during steady‐state flows.This randomized network model, expressed in terms of seven free parameters, can be employed to correlate for a given system the single‐phase permeability, the drainage and imbibition capillary pressure curves, and the two drainage relative permeability curves. The subsequent portions of the hysteresis loops for capillary pressure and for the relative permeabilities then can be predicted.The limited data available from the literature for unconsolidated packed beds have been successfully correlated: 100 to 200 mesh sand and uniform 181 μm glass spheres. Data for a bed of sintered 200 μm glass beads also has been successfully described.
Transient behavior of aerosol filtration in model filters
Authors: Emi H. , Wang Chiu‐Sen , Tien Chi 
Published: June 2004

AbstractThe transient behavior of aerosol filtration in model filters composed of several layers of wire screens was investigated experimentally. The collection efficiency of the filter expressed in terms of the single fiber efficiency was determined under a variety of conditions. The increase in the collection efficiency and pressure drop during the course of filtration was examined. An empirical correlation relating the increase of the collection efficiency as a function of the amount of deposition was established.
Analysis of multicomponent separation by displacement development
Authors: Rhee Hyun‐Ku , Amundson Neal R. 
Published: June 2004

AbstractThe separation of multicomponent mixture by displacement development is fully analyzed by applying the theory of multicomponent chromatography. With Langmuir isotherms it is possible not only to elucidate all the characteristic features of the process but also to derive analytic expressions for the critical value of the developer concentration and the plateau concentration as well as the width of each pure component band attained at the ultimate stage. A specific example demonstrates that the actual solution at the ultimate stage is identical to that predicted a priori by using these expressions. The bed length required for complete separation is determined by examining the wave interactions involved. This procedure is clearly illustrated.
Dissolution and reprecipitation in porous solids
Authors: Cussler E. L. 
Published: June 2004

AbstractWhen a porous solid dissolves in acid, the dissolved solid can diffuse both into the bulk solution and into the solid's pores. In some cases, these dissolved species can precipitate in the pores, making the solid less permeable to acid. In other cases, the surface dissolution can produce precipitation near the surface and dissolution well below the surface. The results have implications for corrosion, including the demineralization of teeth.
Local drag reduction due to injection of polymer solutions into turbulent flow in a pipe. Part II: Laser‐doppler measurements of turbulent structure
Authors: McComb W. D. , Rabie L. H. 
Published: June 2004

AbstractAqueous solutions of polythyleneoxide (Polyox WSR‐301) were injected into a pipe flow through either a small tube at the center line or an annular slot in the wall. The solution contained polymer at an injection concentration of 1,000 wppm. Injection into water flow with a Reynolds number Re = 3.5 × 104 was at a rate which gave a mean polymer concentration of 5.0 wppm in the water flow. A laser‐Doppler anemometer (LDA) was used to measure the streamwise turbulent velocity at various radial positions and at several stations downstream from the injection point.Results were obtained for mean velocity and intensity profiles; autocorrelations; and one‐dimensional energy spectra. The mean bursting period was determined using the “short‐sampling‐time” autocorrelation method. Changes in all these quantities due to polymer injection were found to depend on the amount of local drag reduction at that particular downstream station but were independent of the local polymer concentration at the measuring point.
Analysis of laminar non‐Newtonian flow and heat transfer in curved tubes
Authors: Hsu Chia‐Fu , Patankar S. V. 
Published: June 2004

AbstractThe governing equations for the laminar fully developed flow and heat transfer in curved tubes are solved numerically for a power‐law fluid. Results for the velocity and temperature fields, the friction factor, and the Nusselt number are presented for different values of the Dean number, the Prandtl number, and the power‐law index. The friction factor results are compared with available experimental data.
Experimental validation of the Adams‐Welty model for heat transfer in large‐particle fluidized beds
Authors: Čatipović N. M. , Fitzgerald T. J. , George A. H. , Welty J. R. 
Published: June 2004

AbstractExperimental results for instantaneous and time‐averaged local heat transfer coefficients, as well as local voidage and pressure are used to validate the Adams‐Welty analytical model of heat transfer to a horizontal cylinder in large‐particle fluidized beds. Results support the main assumptions of the model and show that the range of applicability is wider than originally expected.
Steady‐state transport in diluted catalysts
Authors: Neogi P. 
Published: June 2004

AbstractThe transport in composite media obtained by dispersing a porous active catalyst inside an inert porous medium has been considered here. Since such systems show a wide variety of advantages, it is necessary to obtain the correct transport equations. Very dilute systems are considered (volume fraction of catalysts ≪ 1/3), a condition that any one dispersed catalyst microsphere cannot feel the influence of others arises. An averaged conservation equation at steady state is obtained under the above condition as well as the condition that any one microsphere can be randomly placed in the medium. Similarly, an effective diffusion coefficient has been obtained.The results differ from the ones previously in use. The enhancement in the reaction rate on diluting a catalyst is seen to be much less than the values previously suggested although a qualitative similarity exists.
Dynamic studies of dispersion and channeling in fixed beds
Authors: Oliveros Gabriel , Smith J. M. 
Published: June 2004

AbstractAn experimental and theoretical study was carried out to relate the extent of channeling in a packed column to the response in the effluent gas to a tracer input. When the response curve showed a distinct peak associated with a channel, it was possible to establish the flow rate and void area of the channel from only the response curve. The experimental data provided new information on Peclet numbers in packed columns with nonuniform void fractions (low tube‐to‐particle diameter ratios).
Heat transfer to horizontal tubes in the freedboard region of a gas fluidized bed
Authors: George S. E. , Grace J. R. 
Published: June 2004

AbstractOverall heat transfer coefficients were measured for an instrumented horizontal tube of diameter 25 mm in the feedboard region above fluidized beds of 102 μm, 470 μm and 890 μm sand in a 0.25 m × 0.43 m × 3.0 m tall pilot scale column. The superficial air velocity varied from near minimum fluidization to 1.7 m/s. The instrumented tube was placed at different positions in a 16‐tube bundle. The measured heat transfer coefficients were bounded for tubes near the expanded bed surface by the immersed tube values, and for remote tubes by the values for particle‐free air in crossflow. The results are correlated within ± 12% by a simple equation which incorporates these limits. The results are in good qualitative and quantitative agreement with previous experimental results.
Enthalpy of hydrogen‐containing hydrocarbon liquids
Authors: Kim H. Y. , Sebastian H. M. , Lin H. M. , Chao K. C. 
Published: June 2004

AbstractThe partial enthalpy of dissolved hydrogen in hydrocarbon liquids is derived from the fugacity correlation of Sebastian et al. and the results are presented in general equations. The partial enthalpy of the hydrocarbon solvent is found to be changed only insignificantly by the dissolved hydrogen from that of the pure liquid at the experimental conditions of up to 30 MPa in pressure.
Shear history effects in the spinning of polymers
Authors: Mewis Jan , De Cleyn Guido 
Published: June 2004

AbstractDuring their industrial processing, polymer liquids are usually subjected to complex flow histories. In principle, these can be taken into account in the constitutive equations. In reality, difficulties arise for complex flows. This fact can be illustrated by the spinning process. Here, experiments are presented in which the upstream section of a spinning device has been changed systematically. A constitutive model and a calculation procedure are suggested that permit an analysis of the upstream effects in the spinning flow. The results indicate that this analysis predicts well the spinning dynamics in the present experiments, using shear flow characteristics for the liquids. It is also concluded that the spinning flow can be altered by upstream changes. The changes in structure seem to be the most pronounced ones.
Infeasible path optimization with sequential modular simulators
Authors: Biegler L. T. , Hughes R. R. 
Published: June 2004

AbstractInfeasible path optimization algorithms have been effective with equation‐solving or simultaneous modular process simulators. Using these simulators, successive quadratic programming is applied to large nonlinear programs. However, the algorithms are not directly applicable to commercial simulators of the sequential modular type.Here an infeasible path algorithm is presented which can easily be integrated with most commercial process simulators. The optimization problem remains small (10 or 20 variables) and the user merely replaces the convergence block with an “optimization” block.A simple process example demonstrates the operation, effectiveness, and potential of this algorithm.
Diffusive transport across corrugated plates and tubes
Authors: Wang C.‐Y. 
Published: June 2004

AbstractThe steady diffusion across a constant thickness corrugated barrier is analyzed through the intrinsic coordinate system. Perturbation solutions are found when the thickness is small compared to the minimum radius of curvature. For a given perimeter length, diffusive transfer is decreased, while for given maximum geometric dimensions, diffusive transfer may be increased by corrugations.
Model of solid gas reaction phenomena in the fluidized bed freeboard
Authors: Chen L. H. , WEN C.Y. 
Published: June 2004

AbstractA comprehensive model incorporating elutriation, entrainment and reaction is presented to describe the chemical reaction and hydrodynamics occurring in the freeboard of a fluidized bed. A comparison of experimental data on the amount of particles elutriated and the concentration profiles of SO2 and NOx obtained from the freeboard of fluidized bed coal combustion (FBC) by the Babcock & Wilcox Company with the calculation based on the proposed model to include the effect of interaction among the entrained particles is desirable. More experimental data with chemical reactions in the freeboard are needed to validate the model for applications to fluidized bed catalytic reactors.
Feasible specifications in azeotropic distillation
Authors: Prokopakis G. J. , Seider W. D. 
Published: June 2004

AbstractFeasible operating conditions are obtained for an azeotropic distillation tower using a nonlinear programming algorithm. The boil‐up rate, fractional recovery of product, and bottoms purities of entrainer and by‐product are adjusted to locate an overhead vapor stream that condenses into two liquid phases, but is in equilibrium with a single liquid phase on the top tray. A new objective function is introduced and minimized, subject to inequality constraints, using Powell's algorithm (1977). Results are obtained for dehydration of alcohol with benzene.
A design approach based on phase plane analysis: Countercurrent reactor/heat exchanger with parametric sensitivity
Authors: Akella L. M. , Lee Hong H. 
Published: June 2004

AbstractA design approach based on a phase diagram of inlet temperatures is proposed for the countercurrent reactor/heat exchanger for highly exothermic reactions with inherent parametric sensitivities. The phase diagram shows the region of safe operation on a plane of feed and coolant inlet temperatures, free from runaway conditions. The boundaries surrounding the safe operation region are defined by design parameters. Simple procedures applicable to arbitrary expressions of global rate are developed for the phase diagram. The multi‐pronged design problem of selecting the design parameters and operating conditions for the maximum possible conversion within the constraints due to the parametric sensitivities is condensed into the represented by a phase diagram and an analysis on the phase plane. A design alternative which eliminates the necessity of the preheater for highly exothermic reactions is discussed and the advantages are quantitatively illustrated to assert that this design should be seriously considered as a viable alternative.
Correlation for the third virial coefficient usingTc,Pcand ω as parameters
Authors: Orbey Hasan , Vera J. H. 
Published: June 2004

AbstractAn empirical correlation for the third virial coefficient of nonpolar gases is developed. The correlation requires a knowledge of the critical temperature, critical pressure and acentric factor of the compounds for the prediction of third virial coefficients in the absence of experimental data. The use of the correlation for mixtures of nonpolar gases, including quantum gases, requires one binary parameter for each binary interaction. Predictions are in good agreement with reported experimental data and with the values obtained with existing correlations.
Corrected flowrates estimation by using θ convergence promoter for distillation columns
Authors: Pierucci S. J. , Ranzi E. M. , Biardi G. E. 
Published: June 2004

AbstractThe main task of the θ convergence promoter is to afford a better estimate of liquid and vapor molar fractions in each tray of the column.The assumptions implied by the promoter prove to be reliable for conventional columns, while they may cause numerical instability when dealing with nonconventional configurations. In these cases, corrected molar fractions may be computed only after making a supplementary assumption, which in principle is not unique. So, the paper presents a new methodology which gives rather satisfactory results.