bluuebunny/crossref_metadata_2025_split huggingface dataset:
A collocation approach to distillation column design
Authors: Swartz C. L. E. , Stewart W. E. 
Published: June 2004

AbstractA reduced‐order collocation method is applied to the optimal design of distillation columns. The resulting number of equations is determined by the user and is independent of the numbers of stages in the column sections. The collocation method furthermore permits these stage numbers to be treated as continuous variables, thus extending the discrete solution set. This greatly facilitates the optimization. Several demonstration problems are worked out.
Scaling‐up distillation efficiencies
Authors: Dribika M. M. , Biddulph M. W. 
Published: June 2004

AbstractThis paper describes a study of the possibility of using point efficiencies, measured in a small laboratory column, in the scale‐up of distillation efficiencies. The conditions on a large rectangular tray were closely duplicated in a small glass Oldershaw column with one sieve tray having similar hole size and percent free area. Point efficiencies on the large rectangular sieve tray were deduced from the composition profiles and compared with the point efficiencies measured in the small column. A simple relationship between the two columns was found in terms of the froth heights and liquid holdups. The results demonstrate that the slightly lower point efficiencies measured in the Oldershaw column could be used in conjunction with a mathematical mass transfer model based on the eddy diffusion concept, to relate the point efficiencies to the tray efficiences, resulting in a conservative design provided either that allowance is made for other factors, such as nonuniform flow patterns and stagnant zones, or that these are eliminated. A wide range of composition was covered using the two systems MeOH‐nPrOH and EtOH‐nPrOH operating in the froth region.
Vapor‐liquid equilibria from perturbation gas chromatography. Part II: Application to the polybutadiene/benzene/cyclohexane ternary system
Authors: Ruff W. A. , Glover C. J. , Watson A. T. , Lau W. R. , Holste J. C. 
Published: June 2004

AbstractThis work brings together recent gas chromatography experiments and theory involving multiple sorbing species at finite concentration, and theories for multicomponent polymer solutions by means of the parameter estimation procedure of Part 1. Results quantitatively describe the wide variation in peak retention times that are caused by phase equilibrium and chromatographic interference, the best solution models doing so to within or near experimental error. The chromatographic method is capable of detecting differences and peculiarities in the various polymer solution models in both the accuracy of the calculated retention times and the sensitivities of the calculations to the model parameters. Perturbation chromatography offers some unique capabilities for multicomponent vapor‐liquid equilibrium determinations.
Down‐flow shell‐side forced convective boiling
Authors: Bennett D. L. , Hertzler B. L. , Kalb C. E. 
Published: June 2004

AbstractOne hundred sets of R‐11 two‐phase pressure drop and boiling heat transfer data are reported for cocurrent down‐flow over an in‐line tube bundle. The pressure drop data agree with predicitions using the Diehl correlation. A new heat transfer correlation is reported, accounting for the observed convective and nucleate mechanisms.
Activity coefficients of aroma compounds in model food systems
Authors: Sorrentino F. , Voilley A. , Richon D. 
Published: June 2004

AbstractInfinite dilution activity coefficients of aroma compounds from various chemical series were measured in model food systems (water/carbohydrates, water/polyethylene‐glycols) at concentrations of various solutes. These measurements were made with a specially designed equilibrium cell. Experimental results were used to determine the parameters of group contribution thermodynamic models. The predictive capacities of the equations obtained were shown to be quite precise (8% mean deviation).
Continuous thermodynamics of phase equilibria using a multivariate distribution function and an equation of state
Authors: Willman B. T. , Teja A. S. 
Published: June 2004

AbstractThe dew points of 40 multicomponent fluid mixtures including gas condensates, absorber oils, crude oils, synthetic aromatic heavy oils, and coal liquids were calculated using the method of continuous thermodynamics and the Patel‐Teja cubic equation of state. These multicomponent mixtures were characterized by a log normal distribution function in two variables: the boiling point and specific gravity in this work. Comparisons were made with the case when a single variable distribution function is employed and also with the method of Cotterman et al. In general, the new method leads to excellent predictions of both phase equilibria and liquid densities.
Batch extraction of amines using emulsion liquid membranes: Importance of reaction reversibility
Authors: Baird R. S. , Bunge A. L. , Noble R. D. 
Published: June 2004

AbstractExperimental results for the batch extraction of amines using emulsion liquid membranes with an internal aqueous HCI solution are presented. Four amines and mixtures of one binary pair were studied. Reversibility of the acid‐amine reaction within the internal droplets affected extraction rates. The reversible reaction model presented earlier satisfactorily predicts these experimental results.
Malfunction diagnosis using quantitative models with non‐boolean reasoning in expert systems
Authors: Kramer M. A. 
Published: June 2004

AbstractAn approach to chemical plant fault diagnosis is presented that utilizes patterns of violation and satisfaction of the quantitative constraints governing the process. Process knowledge consists of a list of the operational constraints on the plant together with sufficient conditions for violation of each constraint. Interpretation of the pattern of constraint violations is treated by Boolean and non‐Boolean techniques. It is shown that non‐Boolean reasoning techniques increase the stability and sensitivity of the diagnosis in the presence of noise. The techniques introduced in this paper are easily implemented in rule‐based expert systems using certainty factors.
The kinetic rate of SO2 sorption by CaO
Authors: Simons G. A. , Garman A. R. , Boni A. A. 
Published: June 2004

AbstractThe intrinsic rate constant for the rate of reaction of SO2 with porous CaO in an excess of O2 to form CaSO4 has been determined from SO2 sorption data on a wide range of particle diameters (1 μm‐ 1mm), SO2 partial pressures (60 Pa to 5 kPa), and temperatures (973‐ 1,478 K). An intrinsic SO2 reaction order of unity has been validated through current fixed‐bed experiments in the 60 to 300 Pa SO2 partial pressure range, while fluidized‐bed data were used to validate the reaction order from 500 Pa to 5 kPa SO2 partial pressure. The absolute value of the rate constant and the activation energy was derived from data on small (1 μm) particles, which approach the limit of kinetic control. While analysis of this data base does minimize the role of intraparticle diffusion through the porous sorbent particle, the filling of the small pores by the product deposits and the associated loss of internal surface area is critical to the data reduction. It is believed that the intrinsic rate constant is known to the accuracy to which the reactivity and the BET surface area may be measured.
A reduced hessian strategy for sensitivity analysis of optimal flowsheets
Authors: Ganesh N. , Biegler L. T. 
Published: June 2004

AbstractAn efficient and rigorous strategy is presented for evaluating the first‐order sensitivity of the optimal solution to changes in process parameters or process models. An algorithm that constructs a reduced Hessian in the null space of the equality constraints is used to solve the sensitivity equations; the resulting effort to solve these equations depends only on the space of the decision (independent) variables. Consequently, large computational savings can be realized because the solution procedure eliminates the need for obtaining second partial derivatives with respect to tear (dependent) variables explicitly. The method is applied to several flowsheeting examples in order to determine efficiently the sensitivity of the optimal solution to parametric and physical property model changes.
Finite‐element simulation of stratified multiphase flows
Authors: Mavridis H. , Hrymak A. N. , Vlachopoulos J. 
Published: June 2004

AbstractThe analysis of stratified multiphase flow fields is difficult because the position of the interface is unknown a priori and there is a discontinuity in the normal viscous stress and/or pressure at the interface. A finite‐element technique that uses double nodes along the interface has been implemented. The immiscible liquid displacement in a capillary tube was examined in detail. Fountain flow in the advancing fluid, reverse fountain flow in the receding fluid, and a recirculating flow region in the less viscous fluid were determined. In Newtonian flat film coextrusion the entry region, where the two immiscible fluids form an interface, and the characteristic swelling and bending of the extrudate at the die exit were studied. The computational results compare favorably with available experimental observations.
Multicomponent diffusion in concentrated electrolyte solutions: Effect of solvation
Authors: Pinto N. G. , Graham E. E. 
Published: June 2004

AbstractA method is presented to estimate the diffusivities of electrolytes in concentrated multicomponent systems. The method is based on the Stefan‐Maxwell flux equations. Explicit expressions have been developed for the phenomenological transport coefficients. These expressions incorporate the effects of solvation, viscosity, and ionic interactions. It has been shown that multicomponent diffusion behavior can be related to corresponding single‐electrolyte and tracer diffusion cases. Thus, solvation effects are estimated from single‐electrolyte data, and ion‐ion interaction effects are obtained from tracer diffusion studies. The method has been tested for the ternary system NaCl‐KCl, at concentrations of up to 3.0 M, and for corresponding single‐electrolyte and tracer diffusion cases at concentrations of up to 4.0 M. In general, the method predicts phenomenological coefficient values within 1.5% of the experimental values for univalent systems.
Design of commercial‐scale gas‐liquid contactors
Authors: Otero Keil Z. , Russell T. W. F. 
Published: June 2004

AbstractA systematic design procedure using a liquid circulation unit for gas‐liquid systems containing low‐viscosity liquids is developed. The procedure can be used to predict and optimize the fluid mechanics and mass transfer in gas‐liquid contactors for a specified performance. Batch liquid mass transfer data obtained from a commercial‐scale aeration basin (12.2 m × 12.2 m × 6.7 m; gas flow rate range, 0.0023–0.01 m3/s) are used to verify the model predictions and to test the design procedure.
Separation synthesis of multicomponent feed streams into multicomponent product streams
Authors: Floudas C. A. 
Published: June 2004

AbstractThe synthesis problem of separation sequences that separate several multicomponent feed streams into several desired multicomponent product streams is addressed. A superstructure is proposed for this separation problem that has embedded all the alternative separation configurations of interest. This superstructure, which has as separator units the separation tasks that are defined for each separation breakpoint, involves options for series and/or parallel sequences, as well as stream splitting, mixing, and bypassing. Formulating and solving this superstructure as a nonlinear programming problem that has as unknowns the stream interconnections, results in an optimal separation sequence. This sequence, which may involve fewer separator units than those included in the superstructure, is shown to be a realistic and practical one. The synthesis approach is illustrated with four example problems.
Nonlinear state feedback synthesis by global input/output linearization
Authors: Kravaris Costas , Chung Chang‐Bock 
Published: June 2004

AbstractThis paper studies the design of feedback controllers for trajectory tracking in single‐input/ single‐output nonlinear systems x = f(x) + g(x) u, y = h(x). A nonlinear transformation of the form v = k(x) + λ(x) u that transforms this nonlinear input/output system into a linear system is first constructed. On the basis of this transformation, an approach for designing control laws for trajectory tracking is presented. The control law is robust in the sense that small changes in it do not produce large steady state errors or loss of stability. The theory provides a unified framework for treating control problems arising in nonlinear chemical processes; this is illustrated by a batch reactor control example.
Fluidized‐Bed reactor model verification on a reactor of industrial scale
Authors: Johnsson J. E. , Grace J. R. , Graham J. J. 
Published: June 2004

AbstractPrevious published comparisons between fluidized‐bed reactor models and experimental data have almost exclusively been in laboratory and pilot‐plant scale equipment. This paper compares data obtained in an industrial phthalic anhydride reactor of 2. 13 m dia. using naphthalene as the feedstock with three models, the Kato and Wen bubble‐assemblage model, the Kunii and Levenspiel three‐phase bubbling‐bed model, and Grace's two‐phase bubbling‐bed model. For the conditions of operation (U = 0.43 m/s, d̄p = 53 μm, H = 7.9 m, T = 636 K), all three models give similar predictions and each gives a good overall prediction of the conversion and selectivity if the reaction kinetics are based on the early study of DeMaria et al. (1961). Hydrodynamic parameters needed for the models are calculated from equations available in the literature. Grid and freeboard effects appear to play relatively minor roles in determining the overall conversion and yields for the reactor in question.
Minimum energy requirements of thermally coupled distillation systems
Authors: Fidkowski Zbigniew , Królikowski LechosłW 
Published: June 2004

AbstractEnergy requirements of four different thermally coupled distillation systems were minimized for an assumed ideal ternary solution being separated. Minimum vapor flows and values of decision variables have been found in the form of analytical expressions. This enables making a quick and simple comparison of these systems. The solution method can be used for synthesis of separation systems or for screening calculations.
Pressure swing adsorption: A theoretical study of diffusion‐induced separations
Authors: Shin Heung‐Soo , Knaebel K. S. 
Published: June 2004

AbstractThis report examines gas separation by a pressure swing adsorption (PSA) process that exploits differences in intraparticle rates of diffusion, rather than differences in adsorption isotherms. Film and intraparticle diffusion resistances are taken into account, but only the latter is examined closely. Each step of a four‐step cycle is incorporated, and concentration profiles within the particles and along the column axis are predicted. Several critical PSA operating conditions, including step times, velocities, and pressures are studied in the context of separation of nitrogen from air with zeolite 4A.
A chemical reaction model for physical vapor deposition of compound semiconductor films
Authors: Jackson S. C. , Baron B. N. , Rocheleau R. E. , Russell T. W. F. 
Published: June 2004

AbstractA model for the physical vapor deposition of compound semiconductor films that describes film growth from component molecular beams is presented. Constitutive relationships are used in the model to account for incomplete adsorption from the incident molecular beams, emission of adsorbed components into vacuum, and surface reactions of the elemental species. The model predicts film composition and growth rate as a function of incident fluxes and substrate temperature. It is applicable for important binary and ternary alloy semiconductors including the II‐VI and III‐V compounds over the range of deposition conditions yielding both stoichiometric and two‐phase films. In this paper the model equations and the behavior predicted by the model are described for a number of material systems including (CdHg)Te, (CdZn)S, and CuInSe2.
Fundamentals of a centrifugal fluidized bed
Authors: Chen Ye‐Mon 
Published: June 2004

AbstractA fundamental theory based on the local momentum balances is proposed to explore the fluidizing phenomena of a centrifugal particle bed. Unlike the conventional vertical bed, a centrifugal bed is predicted to be fluidized layer by layer from the inner free surface outward, in a range of aeration rates. The span of this range increases with the depth of the particle bed. The pressure drop is predicted to exhibit a plateau, which agrees very well with the observations of many investigators, but disagrees with the investigations of Takahashi et al. and Fan et al., in which the pressure drop exhibited a maximum. Predictions of the critical fluidizing velocity and the corresponding pressure drop agree well with the data of Fan et al.
CO oxidation on Pt: Model discrimination using experimental bifurcation behavior
Authors: Graham W. R. C. , Lynch D. T. 
Published: June 2004

AbstractAn experimental determination of the steady state behavior for the supported platinum catalyzed oxidation of carbon monoxide in a recycle reactor was performed. Steady state multiplicity was observed. The effects of the size of catalyst charge, feed flow rate, feed composition, and reactor temperature on the location of the boundaries of the steady state multiplicity region were determined. The sensitivity of these bifurcation points to variations in reactor parameters was used to discriminate among five reaction mechanisms. Only an elementary step model incorporating carbon monoxide self‐exclusion from the catalyst surface could quantitatively describe all observed steady state data. An explicit rate function based on this model is presented.
Computing multiple solutions to systems of interlinked separation columns
Authors: Lin Wen‐Jing , Seader J. D. , Wayburn T. L. 
Published: June 2004

AbstractGlobally convergent homotopy continuation methods have been used successfully to find multiple solutions to systems of nonlinear equations used to model multicomponent, multistage separation processes. However, the solutions were achieved by using a multitude of different starting points. This paper describes a procedure for finding all or some solutions of the nonlinear equation system from just one starting point. A reliable algorithm, which utilizes a deflated decomposition technique to overcome the turning‐point problem, an efficient procedure to estimate step sizes, and variable mapping functions to prevent failure when computing physical properties, is developed to follow the homotopy path. The Jacobian matrix is retained as a special structure in all calculation steps. The algorithm has found, from one starting point, all the real roots of the interlinked separation system studied by Chavez et al. (1986). Two additional examples, including one optimization problem and one constrained nonlinear equation system, are presented to illustrate other applications of the algorithm.
Heat and power integration of chemical processes
Authors: Colmenares T. R. , Seider W. D. 
Published: June 2004

AbstractAn efficient nonlinear programming strategy is presented for integration of heat engines and heat pumps with chemical processes. The strategy utilizes the temperature interval method and shows how to use negative heat deficits to obtain lower cost designs. Two important situations are presented in which the resulting designs are less costly when the heat engines and heat pumps are integrated with temperature intervals having negative heat deficits.
Analysis of parallelism in modular flowsheet calculations
Authors: Chimowitz E. H. , Bielinis R. Z. 
Published: June 2004

AbstractAn analysis of parallelism for modular process flowsheet calculations is given. The central idea is to examine various algorithms that allow one to decouple and decentralize flowsheet calculations for computation in a multiprocessor environment. Specific algorithms are evaluated which make use of quasi‐Newton updates to converge the flowsheet equations. From the analysis presented and example problems solved, it is clear that parallel processing can be used to enhance the computational speed of modular flowsheet calculations. In particular, various formulations of the simultaneous modular approach are analyzed to show how parallelism may be taken advantage of in flowsheet solutions.
Modeling of bubble column slurry reactors for multiple reactions
Authors: Bukur D. B. , Zimmerman W. H. 
Published: June 2004

AbstractA model of an isothermal bubble column slurry reactor for an arbitrary reaction network of R independent reactions and S reacting species has been developed. The model accounts for gas velocity variations due to a change in total number of moles during reaction, and for nonuniform catalyst distribution due to gravity settling. It is assumed that the gas phase is in plug flow and the batch liquid phase is unmixed, which is characteristic of pilot plant reactors with high aspect ratios. The minimum number of differential equations required for the complete description of the system is shown to be equal to the total number of independent reactions. A system of two series‐parallel reactions, representative of Fischer‐Tropsch synthesis, was used to study the effect of catalyst dispersion and model parameters on reactor performance. It was found that nonuniform catalyst distribution generally has a negative effect on conversion.
Xylene isomerization using zeolites in a gradientless reactor system
Authors: Ma Y. H. , Savage L. A. 
Published: June 2004

AbstractA gradientless reactor was used to study the xylene isomerization reaction over a series of cation‐exchanged (H+, Li+, Na+, and K+) ultrastable faujasite and on ZSM5 and silicalite to observe the effects of site modification on the reaction. Adsorption, diffusion, and kinetic parameters were determined in the presence of the reaction; the results generally agreed with the available literature data. The gradientless reactor and associated modeling techniques are shown to be effective tools in investigating catalyst behavior. Precise analytical techniques are required to directly measure the diffusion coefficient in the presence of reaction.
Equilibrium‐limited periodic separating reactors
Authors: Vaporciyan Garo G. , Kadlec R. H. 
Published: June 2004

AbstractA new unit operation is presented that utilizes a rapid feed pressure swing cycle in a bed packed with catalyst and adsorbent to effect both reaction and separation. This hybrid device combines features of a cyclic‐steady‐state pressure swing adsorber with those of a flow‐forced catalytic reactor. Feed sequences for the periodic separating reactor (PSR) are those of rapid, single‐bed pressure swing adsorbers (PSA). Only the case of extremely fast reactions is considered here. A perturbed reaction‐sorption equilibrium model is formulated and solved for isothermal operation for different equilibrium constants and reaction stoichiometries. The capacity and separation performance for an equilibrium‐limited PSR (EPSR) can be of the same order of magnitude as PSA alone. For reactions involving a single reactant or single product, the principal component in a particular exit stream depends upon both the reaction stoichiometry and feed fraction of the process cycle. The pressure dependency of the reaction equilibrium expression is the cause of separation reversals as parameters are varied.