bluuebunny/crossref_metadata_2025 huggingface dataset:
Separation of proteins via multicolumn pH parametric pumping
Authors: Chen H. T. , Yang W. T. , Pancharoen Ura , Parisi Robert
Published: June 2004

Fractionation of protein mixtures by multicolumn pH parametric pumping is investigated theoretically and experimentally. The parapumps considered consist of a series of columns packed alternately with cation and anion exchangers. Various methods of operation of the parapumps are discussed. Two separation problems are examined: enrichment and splitting. Experimental data were obtained for two‐column systems and compared with the calculated results based on an equilibrium theory.
The separation of ethylbenzene from p‐ and m‐xylene by extractive distillation using mixtures of polychloro compounds
Authors: Berg Lloyd , Kober P. J.
Published: June 2004

The use of a single compound as the agent in modifying the apparent relative volatility in extractive distillation is well known. In the separation of ethylbenzene from para‐ and meta‐xylenes by extractive distillation, it was found that mixtures containing from two to four components were more effective than any known single compound. Hundreds of combinations of extractive agents were investigated in vapor‐liquid equilibrium stills, and from these, twenty‐seven different combinations of chlorinated organic compounds showed merit. The relative volatility of ethylbenzene to p‐xylene is 1.06 and to m‐xylene 1.08. The promising combinations were investigated in three glass perforated plate extractive distillation columns containing twelve, fifteen and nineteen theoretical plates, respectively. Of the twenty‐seven different extractive agents tested in the columns, sixteen yielded a relative volatility greater than 1.20. The best one, a mixture of pentachlorophenol, benzene hexachloride and 1,2,4‐trichlorobenzene, gave a relative volatility of 1.27. Other combinations approaching this relative volatility are pentachlorophenol, benzene hexachloride and 2,4‐dichlorotoluene giving 1.25 and polychlorobenzene, pentachlorophenol, benzene hexachloride and 1,2,4‐trichlorobenzene giving 1.26, when used in the ratio of two parts of extractive agent to one part of ethylbenzene‐xylene mixture. All the extractive agents boil sufficiently above xylene to make their recovery by distillation easy and complete. Life studies showed no excessive decomposition of any of them while in use.
Rate parameters for adsorption of CO2 in beds of carbon particles
Authors: Andrieu J. , Smith J. M.
Published: June 2004

Adsorption equilibrium constants and intraparticle diffusivities were determined for the adsorption of carbon dioxide on an activated carbon derived from bituminous coal particles. The moment method was used to extract these results from pulse‐response measurements for beds of carbon particles. The activated carbon had a very broad pore‐size distribution: average radius of micropores was 11Å and macropores 3750Å. Bulk molecular and Knudsen diffusion could not explain mass transfer in the micropores. An activated surface migration concept (Chihara et al., 1978) did give reasonable results. The adsorption rate was also significantly retarded by intraparticle diffusion in the macropores.
Substrate‐inhibited kinetics with catalyst deactivation in an isothermal CSTR
Authors: Do Duong D. , Weiland Ralph H.
Published: June 2004

Analytical expressions are developed for the time‐dependent reactant concentration and catalyst activity in an isothermal CSTR with Langmuir‐Hinshelwood kinetics of deactivation and reaction. Several parallel and series posioning mechanisms are considered for a reactor which, without poisoning, would operate at a unique steady state. The use of matched asymptotic expansions and abandonment of the usual initial‐steady‐state assumption give results, valid from startup to final loss of activity, whose accuracy can be improved systematically.
Determination of interaction second virial coefficients; He‐CO2 system
Authors: Holste J. C. , Watson M. Q. , Bellomy M. T. , Eubank P. T. , Hall K. R.
Published: June 2004

We have obtained values for interaction second viral coefficients of the helium‐carbon dioxide system in the range 230 ⩽ T/K ⩽ 300. Our experimental technique is essentially the Burnett mixing method described by Hall and Eubank (1973, 1974). We have modified the analysis to account for higher‐order effects and to detect significant systematic errors. We also report virial coefficients for the pure components: helium in the range 100 ⩽ T/K ⩽ 300 and carbon dioxide at 300 K.
Correlation of solubility of hydrogen in hydrocarbon solvents
Authors: Sebastian H. M. , Lin H. M. , Chao K. C.
Published: June 2004

A correlation is developed for the solubility of hydrogen in hydrocarbon solvents at temperatures from 310 to 700 K and pressures to 30 MPa (300 bar). The fugacity of dissolved hydrogen at zero pressure is correlated as a function of solubility parameter and temperature. The high‐pressure fugacity is obtained upon applying a Poynting factor for which the required partial molal volume of hydrogen is also correlated in terms of solubility parameter and temperature. The Henry constant of hydrogen is included in the correlation. The correlated results are compared with experimental data for 22 systems of binary and ternary solutions and five narrow‐boiling cuts of coal liquids. The overall average absolute deviation for all systems studied is approximately 6%.
Measurement of mass flux in two‐phase flow using combinations of pitot tubes and gamma densitometers
Authors: Hau K‐F F‐L , Banerjee S.
Published: June 2004

New experimental data indicate that mass flux in cocurrent gas‐liquid flows may be determined by the use of Pitot tubes in conjunction with a local mixture density measurement technique. The data were taken over a wide range of flow regimes in a horizontal pipe and included separated patterns such as stratified and annular flows. Local mixture densities were obtained by a computer‐assisted algebraic reconstruction technique that used chordal average densities measured by traversing gamma beam attenuation.

The results extend the applicability of this mass flux measurement technique well beyond the relatively homogeneous, high‐pressure, steam‐water flow situations originally studied by Banerjee and Nguyen (1977).
Efficiency of mixing from data on fast reactions in multi‐jet reactors and stirred tanks
Authors: Ottino J. M.
Published: June 2004

Some fluid mechanical information concerning mixing generation in complex flow fields can be obtained from conversion data of fast chemical reactions. Computation of such information and averages required in the procedure are presented here. Complex turbulent flow fields present deterministic‐like behavior when analyzed in average sense with regard to mixing generation.
A review of process synthesis
Authors: Nishida Naonori , Stephanopoulos George , Westerberg A. W.
Published: June 2004

Process synthesis is the step in design where the chemical engineer selects the component parts and how to interconnect them to create his flowsheet. This paper reviews the rapidly growing process synthesis literature of over 190 articles, almost all of which have been produced in the last decade.

The paper first introduces the nature of the synthesis problem and outlines the variety of approaches which have appeared to solve aspects of it. The problems include developing a representation, a means to evaluate alternatives, and a strategy to search the almost infinitely large space of possible alternatives. As the article demonstrates, effective solutions are very dependent on the nature of the synthesis problem being addressed.

The article covers in detail the following five synthesis topics: chemical reaction paths, separation systems, heat exchanger networks, complete flowsheets, and control systems. Readily apparent are the development of industrially significant insights to aid in the design of heat exchanger networks. Reasonable progress exists in the synthesis of separation systems based on nearly ideal distillation technology and in the development of computer aids by chemists for reaction path synthesis leading to desired complex organic molecules. More work is needed for the remaining areas to become industrially significant.
Drag force measurement of single spherical collectors with deposited particles
Authors: Pendse Hemant , Tien Chi , Turian R. M.
Published: June 2004

The hydrodynamic drag force in a uniform flow field acting on a spherical body with small particles attached to its surface was determined experimentally. The experimental data are used to substantiate the approximate force expressions derived from available theories for several types of collector‐particle geometries. Procedures for applying these results to the prediction of the pressure drop across a filter bed with various degrees of particle deposition are also developed.
Pressure fluctuations in a fluidized bed
Authors: Fan L. T. , Ho Tho‐Ching , Hiraoka S. , Walawender W. P.
Published: June 2004

An on‐line statistical study of the pressure fluctuations in fluidized beds was conducted by using pressure transducers, a correlation and probability analyzer and a Fourier transform analyzer. The causes of the fluctuations were explored, and the effects of the gas velocity, bed height, particle size and distributor design on the major frequency and amplitude of the fluctuations were investigated. The results indicate that the motion of bubbles appears to be the major cause of the pressure fluctuations in the upper portion of a fluidized bed. In the lower portion, the combined effects of the formation of large bubbles in the middle portion of the bed, the formation of small bubbles near the distributor, and the jet flow immediately above the distributor appear to be the major causes of pressure fluctuations.
Bacterial film growth in adsorbent surfaces
Authors: Andrews G. F. , Tien Chi
Published: June 2004

Simultaneous biological and activated‐carbon treatment of organic wastewaters appears promising. The effects of bacterial film growth on adsorbent particles is investigated by laboratory work and mathematical modelling. Regeneration of the adsorbent due to film growth does occur, but faster than predicted. The discrepancy reflects uncertainty about the structure of bacterial films.
Minimum reflux conditions, part I: Theory
Authors: Nandakumar K. , Andres R. P.
Published: June 2004

This paper presents a new formulation of the infinite plate or minimum reflux limit of a multicomponent distillation column. Based on this model, two new calculation methods are developed. The first is a short‐cut method which extends Underwood's classic minimum reflux treatment to variable molar overflow situations. The second is a rigorous method which is similar to a multicomponent flash calculation and represents a significant computational advance over other rigorous methods.
Part II: Numerical solution
Authors: Nandakumar K. , Andres R. P.
Published: June 2004

Two new algorithms for calculating minimum reflux conditions in multicomponent distillation columns are described. Both algorithms are based on the continuum model for an infinite stage column proposed by Nandakumar and Andres. Several example problems demonstrate the accuracy and computational efficiency of the new algorithms.
Steady‐State uniqueness and multiplicity of nonadiabatic gas‐liquid CSTRs, part I: Second‐order reaction model
Authors: Huang D. T.‐J. , Varma Arvind
Published: June 2004

Steady‐state behavior of a non‐adiabatic gas‐liquid CSTR is classified applying a second‐order reaction model without any limitation on the reaction regime. Uniqueness and multiplicity regions are determined in the parameter space of reactivity versus liquid residence time, with the ignition and extinction points explicitly shown. An isola with five steady states is found possible for the adiabatic reactor; however, even a small heat loss reduces the number of steady states to three.
II: Discrimination among rival reaction models
Authors: Huang D. T.‐J. , Varma Arvind
Published: June 2004

The discrimination of the fast second‐order, pseudo‐first‐order and fast pseudo‐first‐order reaction models on the basis of the second‐order reaction model justifies the use of the pseudo‐first‐order model in the prediction of the multiplicity regions. The use of the fast second‐order reaction model leads to a certain pitfall regarding uniqueness and multiplicity. Finally, the use of the fast pseudo‐first‐order reaction model is justifiable not only because of the fair agreement between the multiplicity regions predicted by this model and the second‐order model but also because of the analyticity of the uniqueness and multiplicity regions obtained by this model.
An approximate approach to design and analysis of fixed‐bed catalytic reactors
Authors: Lee Hong H.
Published: June 2004

An approximate approach is proposed for the design and analysis of fixed‐bed catalytic reactors in which the intraphase diffusion is important. This approach makes it possible to transform the design and analysis problem of nonisothermal reactors with inter‐ and intraphase mass and heat transfer resistance into one of simply integrating a single equation with respect to concentration. This transformation is applicable to general from of kinetics. Exceptions are reaction rate forms that can exhibit empirical or approximate negative order behavior. The transformation is based on a generalized effectiveness factor or a reactor point effectiveness factor. While the design and analysis of two‐dimensional reactors requires simultaneous solution of conservation equations for mass and heat which are transformed into the equivalents of homogeneous reactors, the problem of one‐dimensional reactors with axial dispersion involves simple integration of a single mass conservation equation.
Effect of fluid drag on low reynolds number discharge of solids from a circular orifice
Authors: Altenkirch R. A. , Eichhorn Roger
Published: June 2004

A dimensionless solids flowrate for discharge from an orifice in the bottom of a containing vessel is shown to be a function of a parameter that measures the importance of fluid drag to particle inertia. The analysis assumes a linear relation between presure gradient and slip velocity and compares favorably to experiment within its supposed region of applicability for three experimental situations: the self‐induced, air‐impeded discharge of fine particles from a conical hopper; the discharge of particles from a sealed egg‐timer‐like vessel; and the air‐assisted discharge of particles through an orifice.
Diffusivity and solubility of carbondioxide in diluted polymer solutions
Authors: Lohse M. , Alper E. , Quicker G. , Deckwer W.‐D.
Published: June 2004

Diffusion coefficients of CO2 in aqueous Newtonian solutions of polyvinyl alcohol and polyethylene glycol with molecular weights varying from 1500 to 100,000 were obtained from absorption rate measurements in a wetted‐wall column and the CO2 solubilities determined independently. The exponent A of the diffusivity‐viscosity relation is found to be a strong function of the molecular weight of the applied polymer. The data suggest the following correlation:

which indicates that the exponent may vary from 0.04 to 0.4 for the solutions studied.
Slow migration of a gas bubble in a thermal gradient
Authors: Subramanian R. S.
Published: June 2004

The steady migration velocity of a gas bubble placed in a liquid with a linear temperature field in the absence of gravity is obtained for small Marangoni Numbers using a matched asymptotic expansion procedure for solving the governing equations. A result good to 0(N) is obtained, and in the limiting case of zero Marangoni Number, the results of Young, Goldstein and Block are recovered.
Analysis of control‐output interactions in dynamic systems
Authors: Tung L. S. , Edgar T. F.
Published: June 2004

A general theory for examining the dynamic as well as static interactions among inputs and outputs in a multivariable control system has been developed. Both state space and frequency domain approaches are used, and at steady state the interaction equations assume the same form as the relative gain array developed by Bristol. Implications of selecting input‐output pairings with regard to steady state vs. dynamic consideration are discussed. The application of the method of analysis to a distillation column control system is presented.
Diffusion effects in initiator decomposition in highly viscous and macromolecular solutions
Authors: Kulkarni M. G. , Mashelkar R. A.
Published: June 2004

Diffusional limitations in single bond and multibond initiators were experimentally investigated. The concept of “microviscosity” was proposed to account for diffusional resistance in different media. This was then used to obtain a unified correlation of the diffusional phenomena regardless of the nature of viscogen. Parameters related to the kinetic and diffusive processes were evaluated and interpreted giving clear fundamental and pragmatic implications of the findings.
Exclusive tear sets for flowsheets
Authors: Motard Rodolphe L. , Westerberg Arthur W.
Published: June 2004

A new implicit enumeration algorithm locates the minimum weighted tear sets among those which belong to the nonredundant families of Upadhye and Grens (1975). Theoretical developments support the algorithm and give a new insight relating nonredundancy to the tearing of unit loops in a flowsheet. If all loops can be torn exactly one time, the nonredundant family is unique and a member of it is trivial to find. If not possible, two or more nonredundant families exist and the above algorithm discerns among them, picking a tear set which minimizes the maximum number of times any unit loop is torn.
Exact calculation methods for systems of interlinked columns. Part I: Separation of binary heterogeneous azeotropes
Authors: Hsu Hsien , Tierney J. W.
Published: June 2004

A mathematical model and iterative correction algorithm are described for the exact solution of separation systems which contain interlinked columns in which some stages have two liquid phases and others have a vapor and liquid phase. The correction algorithm is based on Newton's method and provides for simultaneous correction of all iteration variables. The derivatives are calculated analytically from the model equations. The separation of a binary mixture which forms a heterogeneous azeotrope is analyzed. Modifications to the correction algorithm which provide for fixed condenser temperature and fixed product flows are described. The separation of butanol and water is used to illustrate the method.
Asymptotic expansions for the description of gas bubble dissolution and growth
Authors: Subramanian R. S. , Weinberg M. C.
Published: June 2004

A new asymptotic expansion is presented to describe the dissolution or growth of an isolated, stationary gas bubble in a liquid. With the exception of long times, bubble radii calculated via this expansion are in excellent agreement with values obtained by numerical methods over a wide range of gas under(super)‐saturations.
Esterification of butanol in a two‐phase liquid‐liquid system. PART I: Quaternary phase equilibria studies
Authors: Al‐Saadi A. N. , Jeffreys G. V.
Published: June 2004

The phase equilibria of the systems are discussed:

n‐butanol‐acetic acid‐water and n‐heptane

Water‐acetic acid‐benzene and carbon tetrachloride

Water‐methanol‐p.cresol and methyl naphthalene have been studied and a correlating procedure has been developed that utilizes binary and ternary experimental data to predict the composition of the quaternary equilibrium mixtures. Allowance is made for the different salting effects and the agreement between the experimental and predicted quaternary data is in all cases very good.
An analytical Carnahan‐Starling‐van der Waals model for solubility of hydrocarbon solids in supercritical fluids
Authors: Johnston K. P. , Eckert C. A.
Published: June 2004

Data have been taken by a new flow technique for the solubility of nonpolar hydrocarbons in nonpolar supercritical fluids. These results for molecularly simple molecules provide a basis for the analytical representation of such systems by relatively simple equations of state.
Measurement of effective diffusivity from effluent concentration of a flow through diffusion cell
Authors: Frost A. C.
Published: June 2004

The overall effective diffusion coefficient for 3.3 mm extrudates of 5A Zeolite and CO2/N2 at 292°K and 142 kN/m2 was measured in a continually purged, well mixed, constant volume diffusion cell. The change of CO2 concentration in the effluent stream resulting from a step change in the influent stream was used with appropriate parameters in the analytical solution to calculate diffusion coefficients for the 0 to 0.1 vol. % and 0.1 to 1.0 vol. % CO2 concentration ranges.
Characterization and analysis of continuous recycle systems: Part II. Cascade
Authors: Mann Uzi , Rubinovitch Michael
Published: June 2004

A general analysis of a cascade of identical recycle units is presented by means of studying the fluid history inside the system. This is an extension of Part I (Mann et al., 1979) in which a single recycle unit was analyzed. The history of a fluid element is expressed in terms of the number of cycles it completes, the time it resides in the system and the total time it resides in a specific section of the system—all are random variables. Concepts from probability theory and stochastic processes are used to derive the number of cycles distribution (NCD), residence time distribution (RTD) and various total regional residence time distributions (TRRTDs) as well as their means and variances. Expressions for the joint distributions of pairs of these random variables are also derived as well as explicit expressions for their covariances and correlation coefficients. Two applications of the results are illustrated: one in analyzing a continuous spouted‐bed coating unit and the second in using the cascade as a flexible, physically based multi‐parameter flow model.
Multistage membrane separation processes for the continuous fractionation of solutes having similar permeabilities
Authors: Noda Isao , Gryte Carl C.
Published: June 2004

A new cascade configuration for the continuous membrane fractionation of solutes having similar permeabilities is proposed. In this scheme, solute selectivity is amplified by combining a concentrator and several mass exchangers (e.g., a reverse osmosis unit and hollow fiber dialyzers) to achieve a desired degree of separation. Separation efficiency of the new cascade is compared with that of a conventional counter‐current cascade.
Modeling of three phase reactors: A case of oxydesulfurization of coal
Authors: Joshi J. B. , Abichandani J. S. , Shah Y. T. , Ruether J. A. , Ritz H. J.
Published: June 2004

Mathematical models have been developed for the design of bubble column slurry reactors, wherein the solids take part in the reaction and follow the shrinking core model. The cases of liquid film control, ash diffusion control, and chemical reaction control have been analyzed. Experiments were performed in a 22.2 mm i.d. continuous cocurrent bubble column slurry reactor for the removal of pyritic sulfur by oxidation from aqueous slurries of Upper Freeport, Lower Freeport, Kentucky No. 9, and Pittsburgh seam coals, in the temperature range of 430‐480°K at 6.8 MPa total pressure. The theoretical predictions are found to be in good agreement with experimental results.
Hydrodeoxygenation of dibenzofuran and related compounds
Authors: Krishnamurthy S. , Panvelker S. , Shah Y. T.
Published: June 2004

The catalytic hydrodeoxygenation (HDO) of dibenzofuran was examined on a presulfided NiMo/γAl2O3 catalyst. Based on the reaction intermediates identified in the present study a reaction network for the removal of oxygen from dibenzofuran has been established. In view of the failure to detect certain key reaction intermediates an approximate network has been proposed for kinetic analysis. Using the approximate network the effects of temperature in the range 616–649K, hydrogen pressure in the range 6.89–13.78 MPa and initial concentration of dibenzofuran in the range 9.78 × 10−5 − 21.39 × 10−5 g mol/g oil were examined upon the individual steps.

The removal of oxygen from dibenzofuran under the above conditions proceeded via direct oxygen extrusion without hydrogenation of the adjacent benzene rings as well through the formation of hydrogenated intermediates, with the catalyst showing selectivity towards the latter mode of oxygen removal. Presulfiding the catalyst as well as addition of CS2, to maintain a partial pressure of H2S during the reaction, enhanced the activity of the catalyst. The effect of initial concentration of dibenzofuran indicated a retarding influence on its HDO, possibly due to the formation of refractory reaction intermediates.

The HDO of two key reaction intermediates in the network for dibenzofuran, namely, o‐phenyl phenol and o‐cyclohexyl phenol, was also examined on a presulfided NiMo/γAl2O3 catalyst to establish the reaction network for dibenzofuran. The primary mode of oxygen removal from both the phenols, in the temperature range of 561–644K and 10.34 MPa hydrogen pressure, was through the formation of highly reactive hydrogenated intermediates. All the primary reactions for o‐phenyl phenol were catalytic in nature, whereas, o‐cyclohexyl phenol was found to crack to phenol and cyclohexane even under purely thermal conditions. The rates of decomposition of the above phenols were fairly rapid and highly temperature sensitive, thereby explaining their absence in the reaction products of dibenzofuran.
Model‐based analysis of data from countercurrent liquid‐liquid extraction processes
Authors: Spencer J. L. , Steiner Ladislav , Hartland Stanley
Published: June 2004

An efficient iterative method for solving the equations which describe the steady state of a staged countercurrent extraction process is described. The equations include the effects of backmixing, and apply to an arbitrary number of solutes, to nonlinear equilibrium relations, and to variable net phase flow rates (and thus to partially miscible solvents). The solution procedure, based on partial linearization of the equations, is related to and extends the method of Ricker et al. (1980).

This solution procedure has been used, in conjunction with nonlinear regression methods, to investigate problems related to the determination of parameters by analyzing steady state data. The simultaneous determination of several parameters, including mass transfer coefficients, backmixing coefficients, and equilibrium constants, is shown to be possible. The accuracy with which the parameters can be estimated depends, however, on many factors, including the number and location of the sampling points, the intensity of the backmixing, and the extent to which equilibrium is approached in the column.
Effect of H2O2 on homogeneous gas phase NO reduction reaction with NH3
Authors: Azuhata S. , Akimoto H. , Hishinuma Y.
Published: June 2004

To study the effect of H2O2 on NO reduction with NH3, the homogeneous gas phase reaction of NH3NOH2O2O2 was investigated in a Pyrex flow reactor over the temperature range from 500°C to 600°C under one atmospheric pressure. H2O2 accelerated the NO reduction by NH3 and caused it to be induced at a temperature of 500°C. In the absence of O2, NOx reduction ratio of more than 90% was obtained for NH3/NO5 and H2O2/NO1 at 550°C. In the presence of O2 or an excess of H2O2, two side reactions, which cause the NOx reduction ratio to decrease, occur.

One of the side reactions is NO oxidation with H2O2. It was found experimentally that NO2 inhibited NO reduction and that H2O2 was an NO oxidizing agent, as well as an NH3 decomposing agent. The other side reaction was the formation of NO and NO2, which resulted from the oxidation of NH3 with O2. Under the conditions of our experiments, the amount of O2 in our reaction system was extremely high compared to the amounts of NO, NH3 and H2O2 in the system. Thus NOx was assumed to be produced by the oxidation of the NO reducing radicals, which were produced by the reaction of NH3 with H2O2.
Solution of stiff ordinary differential equations by decomposition and orthogonal collocation
Authors: Burka M. K.
Published: June 2004

A fast and accurate method was developed for the integration of large sparse systems of stiff initial value ordinary differential equations. The system is ordered, decoupled and, if necessary, torn into subsystems (also called blocks) which are then solved by orthogonal collocation on finite elements. The size of these elements, or steps, is different for each subsystem and is a function of the stiffness of the set of equations constituting the subsystem. The steps are overlapped for maximum computational efficiency.
An approximate mathematical model for three‐phase multistaged separators
Authors: Ferraris G. Buzzi , Morbidelli M.
Published: June 2004

An 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

This 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

A 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

Cyclic 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

Measurement 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

The 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

A 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

A 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

A 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

Both 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

The 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

The 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

A 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

A 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

The 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

The 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

When 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

Aqueous 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

The 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

Experimental 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

The 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

An 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

Overall 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

The 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

During 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.
Input multiplicities in nonlinear, multivariable control systems
Authors: Koppel L. B.
Published: June 2004

Input multiplicities in process control occur when more than one set of manipulated parameters m can produce the desired steady state outputs c. They are directly related to the stability and desirability of any intended loop pairing of m's and c's. A chemical reactor example illustrates the phenomena.
Infeasible path optimization with sequential modular simulators
Authors: Biegler L. T. , Hughes R. R.
Published: June 2004

Infeasible 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.