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  • 1985-1989  (759)
  • 1930-1934
  • 1989  (759)
  • Chemical Engineering  (759)
  • 201
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 539-548 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A continuous mixture is one which is so complex that it is no longer worthwhile to distinguish individual chemical species; instead, an index, such as the simulated boiling point, is chosen and ci, the concentration of the species Ai, is replaced by c(x)dx, the concentration of material with index in the interval (x, x + dx). It has been long known that the total concentration of a suitably distributed mixture, each of whose components disappears by a first-order reaction with constant k(x), will appear to disappear according to a higher order of reaction. The generalization of this to a mixture that requires two indices for its description is worth considering for three reasons: First, there may well be materials that are so complex as to require this. Second, the second index may be considered to distribute reaction time. Third, this approach seems to answer the mathematical question of how to generalize from the continuum of first-order reactions to one of parallel Nth-order reactions.
    Additional Material: 4 Ill.
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  • 202
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 573-578 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Adsorption equilibria have been gravimetrically measured at 10, 20, 30, 50, and 70°C for benzene on pure crystalline silicalite. Isotherms change from type I to type IV with decreasing temperature, indicating heterogeneous behavior. The transition temperature is determined to be 38 ± 1°C by isobaric experiments. Silicalite is energetically homogeneous since there are no cations present. The observed structural heterogeneity is due to the comparable sizes of benzene molecules and the silicalite pore system. Silicalite is modeled as two types of homogeneous pores where a van der Waals model describes local equilibrium. Model parameters are calculated via nonlinear regressions with prescribed pore distribution determined from crystallographic considerations. Data and model predictions are in good agreement with highly significant parameters.
    Additional Material: 7 Ill.
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  • 203
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 603-613 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A block relative gain measure for nonsquare systems has been derived. Evaluated at steady state, this measure serves as a performance-related tool for evaluating control structures prior to controller design. Both the nonsquare dynamic block relative gain and the relative sensitivities have been presented as dynamic interaction measures that depend on the controller tuning and are consequently applicable to design of nonsquare decentralized controllers. Rigorous relationships between the dynamic block relative gain and the performance and stability of a closed-loop system have been established.
    Additional Material: 8 Ill.
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  • 204
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 746-754 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The lattice of an oxide catalyst can act as a reservoir for oxygen, storing and releasing it for oxidation reactions at the catalyst surface under appropriate transient conditions. The implication of this oxygen storage property on the dynamic response characteristics of packed-bed reactors loaded with oxide catalysts has been investigated through an experimental study of 2-butene oxidation over vanadium oxide. Temperature profiles in a wall-cooled packed-bed reactor have been measured at steady state and following step changes in the feed butene concentration and in the feed gas flow rate. Thermal reactor runaway was observed experimentally for large step increases in the feed butene concentration following certain catalyst pretreatments. Gas flow rate step increases and less severe butene step increases resulted in the reactor temperature overshooting its final steady-state profile. These response characteristics are a direct consequence of the oxygen storage property of the vandaium oxide catalyst.
    Additional Material: 13 Ill.
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  • 205
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 529-532 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The analysis of Astarita and Ocone (1988) of the lumping of nonlinear kinetics in continuous mixtures offers a framework for examining the apparent overall behavior of a multicomponent mixture given the underlying intrinsic kinetics. Specific solutions of the governing equations are given for some special cases of underlying intrinsic kinetics. It is shown that the apparent overall order of reaction may be both larger and smaller than the underlying one, depending on the initial concentration distribution and on the distribution of kinetic parameters.
    Additional Material: 1 Ill.
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  • 206
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 592-602 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is introduced for analyzing diameter variations occurring in glass fibers drawn from preforms. The heat transfer is shown to be radiation-dominated, and approximate expressions for radiative exchange are developed. The expressions are used in the one-dimensional governing equations for extensional flows to derive a set of linearized disturbance equation as an eigenvalue problem. The sensitivity to an oscillatory take-up rate is also studied as a boundary-value problem. Calculated amplitudes of final diameter perturbations are found to agree well with experimental values.
    Additional Material: 7 Ill.
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  • 207
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 579-591 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The infinite-horizon, discrete-time optimal averaging level control problem for surge tanks, with minimization of the rate of change of outlet flow as its objective, is formulated and a solution is presented. A finite moving-horizon approximation is introduced and analytical solutions are obtained for two important special cases. These results provide a quantitative measure of the impact of a secondary objective, integral action, on flow filtering. The problem is then generalized to include nonconstant level and outlet flow constraints. A model predictive control formulation is presented which addresses the objectives of the generalized problem. The resulting controller minimizes the maximum rate of change of outlet flow, provides integral action, and handles constraints on the tank level and outlet flow rate. The proposed controller includes a single adjustable parameter that directly effects the trade-off between the incompatible objectives of good flow filtering and rapid settling time. Examples are presented to demonstrate the properties of the model predictive controller. An implementation, involving imbedded feedback, is developed which guarantees internal stability of the model predictive scheme for open-loop unstable processes (such as integrators).
    Additional Material: 9 Ill.
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  • 208
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 614-624 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Galerkin finite-element method is used to study the rotating, thermocapillary fluid flow in the cylindrical float zone configuration for crystal growth. Results are presented for a fluid of Prandtl number 1.0 in a zone of unit aspect ratio under microgravity conditions. In the absence of rotation, the thermocapillary flow is responsible for large radial non-uniformities in the heat transfer, especially at the cold boundary. A sufficiently strong uniform corotation of the end rods leads to a rigid rotation of the fluid in the interior of the zone; in this case, the thermocapillary flows are considerably attenuated and confined to a region near the free surface of the zone. This provides a more uniform thermal environment over the bulk of the crystal-melt boundary, which is a very desirable processing condition. When the end rods are counterrotated, inertially driven meridional flow cells appear in the zone. The interaction of the rotational forced convection with the thermocapillary flow causes the region of the local heat transfer minimum at the cold boundary to gradually shift away from the axis of the zone toward the meniscus.
    Additional Material: 12 Ill.
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  • 209
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 655-657 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 210
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 967-980 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The important connection between particulate deposit properties and deposition mechanism remains poorly understood and only scarcely studied. Accordingly, in this research, we develop a discrete stochastic model to simulate particulate deposition processes resulting from realistic combinations of deposition mechanisms. Particle motion is assumed to be determined by the superposition of a deterministic force that acts toward the collecting surface and a random force, which produces Brownian diffusion. We characterize the resulting deposit microstructure via porosity and pore size/area distribution, surface area; and we examine the evolution of these descriptors with time (number of particles deposited) for different deposition mechanisms. We also examine the effect of particle polydispersity, spatial orientation (for nonspherical particles), and mean-free-path on the resulting deposit structure.
    Additional Material: 13 Ill.
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  • 211
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1029-1031 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 212
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1032-1038 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
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  • 213
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 705-713 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been experimentally observed, for water and nonaqueous solvents alike, that Henry's constant passes through a maximum and then declines as the temperature is raised from the triple point to the critical point. From classical and nonclassical models, we derive exact relations for the value of Henry's constant and its temperature dependence at the solvent's critical point, showing that the decline of this constant is a universal phenomenon. We demonstrate that the limiting temperature dependence of Henry's constant can be predicted from the thermodynamic properties of the pure solvent and the initial slope of the critical line. The validity of our prediction is tested by comparing it with experimental solubility data for several gases in high-temperature water and benzene. Our predictive model appears valid over a temperature range of at least 15% in temperature below the critical point of the solvent.
    Additional Material: 8 Ill.
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  • 214
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 737-745 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An investigation of the continuous chromatographic separation of an equimolar mixture of 1,3,5-trimethylcyclohexane and 1,3,5-trimethylbenzene with a 2.4 m × 1.37 cm ID vertical countercurrent moving bed is reported. The solid adsorbent was 30 mesh Al2O3, and the separation was carried out at 200°C. Steady-state axial concentration profiles of each species were determined by withdrawing vapor samples for analysis by gas chromatography. The binary mixture was continuously fed through a port located at approximately the midpoint of the column. The relative solids and carrier gas flow rates could be adjusted so that the more strongly adsorbed trimethylbenzene was transported downward, and less strongly adsorbed trimethylcyclohexane moved upward. For low feed rates, high-purity product streams of each were obtained at the bottom and top of the separator. For sufficiently high feed rates, trimethylbenzene was transported upward as well as downward, and top product purity deteriorated. This behavior is in qualitative accord with the predictions of a dispersionless, one-dimensional flow, adsorption equilibrium model incorporating a Langmuir isotherm.
    Additional Material: 16 Ill.
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  • 215
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 803-813 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A quasichemical partition function is applied to represent the thermodynamic properties of aqueous solutions of nonelectrolytes, including linear polymers and crosslinked polymers (gels). The partition function extends conventional lattice theory; to take into account strong specific interactions (hydrogen bonds) as encountered in aqueous solutions, each molecule (polymer segment) may possess three energetically different types of contact sites. We distinguish between sites that interact through dispersion forces and sites that can participate in a hydrogen bond; hydrogen-bonding sites are divided into electron-pair donating sites and electron-pair accepting sites. The Helmholtz energy of the mixture is obtained using an oriented quasichemical approximation. The final equation contains three independent adjustable binary parameters; these are the exchange energies for different types of contact paris. To represent quantitatively upper or lower critical solution phenomena, we include the semitheoretical fluctuation correction recently proposed by de Pablo. Comparison with experimental data indicates that the proposed molecular-thermodynamic model may be useful for representing phase equilibria for a variety of aqueous systems including swelling equilibria for hydrophilic gels.
    Additional Material: 5 Ill.
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  • 216
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 831-844 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The novel combination of a pressure swing adsorber (PSA) with a periodic flow-forced packed-bed reactor is explored. The device provides integral component separation and reaction. Feed sequences studied for the periodic separating reactor (PSR) were those of rapid, single-bed pressure swing adsorption (RPSA). The experimental investigation employed CO oxidation over a packed bed of supported platinum catalyst and molecular sieve adsorbent. A reaction rate limited model is formulated and solved for a variety of irreversible and reversible reactions.The presence of irreversible chemical reaction is shown to greatly enhance the separation achievable by RPSA alone. For a wide range of inlet CO/O2 ratios, CO2 production could be increased up to two times over steady-state plug-flow reactor operation, while providing a recycle stream without phase change or extractive procedures. Selectivity and conversion improvements were predicted for multiple reaction systems. Other unusual features of operation, such as separation reversals, were also predicted and observed.
    Additional Material: 13 Ill.
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  • 217
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 159-163 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 218
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 164-167 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 219
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 335-338 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 220
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 221
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 695-699 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 222
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 223
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 725-736 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simulated annealing is a multivariable optimization technique based on the Monte Carlo method used in statistical mechanical studies of condensed systems and follows by drawing an analogy between energy minimization in physical systems and costs minimization in design applications. In this paper, simulated annealing is introduced and reviewed. The utility of the method for optimization of chemical processes is illustrated by applying it to the design of pressure relief header networks and heat exchanger networks.
    Additional Material: 6 Ill.
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  • 224
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    AIChE Journal 35 (1989), S. 764-774 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional membrane permeation of gases employ a non-step process between the feed and the product on two sides of a membrane. By applying the overall driving force change through a two-step process using two membranes in one device, we illustrate theoretically the possibility of achieving a much higher enrichment without any extra energy consumption. Such an internally staged permeation is experimentally carried out in a hollow-fiber permeator with two sets of asymmetric cellulose acetate hollow fibers for the systems of O2—N2 (air) and CO2—N2. The superior enriching performance of the internally staged permeator over the same permeator operated in the conventional mode is demonstrated experimentally. A cocurrent flow pattern is found to be superior to a countercurrent flow pattern for the conditions employed. The simulation model incorporating fiber lumen pressure drop predicts the experimental performance quite well. A further improvement in performance can be achieved by recycling the intermediate pressure shell reject stream to the feed stream. The energy requirement in an internally staged permeator without recycle is less than that of a conventional permeator with permeate recycle.
    Additional Material: 15 Ill.
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  • 225
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 814-820 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modules containing from 120 to 27,000 parallel hollow fibers 100 μm in diameter can separate mixtures by reversed phase chromatography. The mixtures separated include aqueous solutions of ketones using alkanes as the stationary phase, and aqueous solutions of the proteins myglobin and cytochrome-c using an octane solution of reversed micelles as the stationary phase. The dispersion observed in these separations is comparable to that predicted from the Aris-Taylor theories. Modules of these fibers promise a lower pressure drop and a greater reproducibility than columns of spheres of equivalent surface area per volume. Such modules can facilitate scale-up of liquid chromatography.
    Additional Material: 7 Ill.
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  • 226
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 876-876 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 227
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    AIChE Journal 35 (1989), S. 981-987 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the experimental technique and data acquired in the evaluation of a separation process in the crossover region of a model supercritical fluid system consisting of benzoic acid, 1-10 decanediol, and carbon dioxide. The results show that by exploiting the crossover effect it is possible to obtain essentially pure benzoic acid (〉99.5% purity) with a single temperature cycle. A number of other issues are also discussed including the tradeoff between yield and purity and the manner in which the process variables are specified, which involves the interplay of experiment and model calculations.
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  • 228
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    AIChE Journal 35 (1989), S. 1003-1016 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extended transportation array representation is developed for the design of process heat recovery networks incorporating heat engines and heat pumps. The formulation automatically accounts for the relocation of pinches in the integrated system. The optimal heat flow pattern is determined based on simple economic criteria. Simplified models of heat engine and heat pump systems are developed that permit integration options to be identified on the basis of heat flows without requiring specific cycle designs. The solution array identifies design alternatives and provides a decision framework to guide in selecting the final design topology.
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  • 229
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    AIChE Journal 35 (1989), S. 1044-1048 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 9 Ill.
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  • 230
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 231
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    AIChE Journal 35 (1989), S. 1085-1096 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ignition process of condensed-phase combustion by a laser is studied experimentally as well as numerically. Numerical simulations are performed in one, two and three spatial dimensions, and are compared with the experimental observations. The effects of energy-dissipative mechanisms, such as melting and ablation due to laser irradiation and the effects of laser power output fluctuations, are also studied. We find that the ignition process depends mainly on the energy deposited in the system. The time leading up to ignition is longer for higher light fluxes keeping the average laser power constant, since a larger fraction of the energy is reradiated from the heated surface or consumed during the process of material removal.
    Additional Material: 17 Ill.
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  • 232
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    AIChE Journal 35 (1989), S. 1125-1136 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simultaneous measurements of mass transfer rates to quasisteady-state pendant aqueous droplets and rates of surface renewal due to Marangoni effects have been carried out using the water/toluene system with acetone as solute. The surface renewal measurements were made with the photochromic dye tracer technique reported earlier (Thornton and Anderson, 1981; Thornton et al., 1985).Both the mass transfer coefficients and the rates of surface renewal have been shown to be dependent upon the age of the droplet interface and the solute concentration in the continuous phase. Thus, coefficients of a young droplet are high initially, but decrease with time and approach a constant value, dependent upon solute concentration, as the interface ages.This parallel decrease in both interfacial (Marangoni) activity and transfer rates with time has also been observed (Rogers et al., 1987) with inorganic solutes such as uranyl nitrate and has implications for contactor design.
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  • 233
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    AIChE Journal 35 (1989), S. 1157-1169 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The proposed on-line adaptive optimization technique incorporates a priori knowledge in the form of approximate steady-state models. The steady-state geometric characteristics of the model are periodically recalculated using a Hammerstein system and recursive least squares. The algorithm is self-tuning in the sense that it converges to the optimal performance provided that a matching condition is satisfied and that the data are persistently exited. Simulation and experimental studies performed on a continuous fermentation system have been conducted to illustrate the performance of the optimization algorithm and demonstrate the viability of adaptive extremum control.
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  • 234
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    AIChE Journal 35 (1989), S. 1199-1202 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    AIChE Journal 35 (1989), S. 1907-1911 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 236
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    AIChE Journal 35 (1989), S. 2033-2036 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 237
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    AIChE Journal 35 (1989), S. 2048-2052 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 238
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    AIChE Journal 35 (1989), S. 223-229 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A robust and efficient algorithm is developed to calculate dynamic inputs for optimal experimental designs. Different objective functions are presented to allow designs for both model discrimination and the improvement of parameter precision. Time-varying inputs are calculated by reformulating the optimal design problem as an optimal control problem. This approach can provide large improvements in the ability to discriminate among a series of models, and then increase the accuracy of the resulting parameters.
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  • 239
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    AIChE Journal 35 (1989), S. 241-249 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Model predictive control (MPC) schemes such as MOCCA, DMC, MAC, MPHC, and IMC use discrete step (or impulse) response data rather than a parametric model. They predict the future output trajectory of the process {ŷ(k + i), i = 1, …, P}, then the controller calculates the required control action {Δu(k + i), i = 0, 1, …, M - 1} so that the difference between the predicted trajectory and user-specified (setpoint) trajectory is minimized. This paper shows how the step (impulse) response model can be put into state space form thus reducing computation time and permitting the use of state space theorems and techniques with any of the above-mentioned MPC schemes. A series of experimental runs on a simple pilot plant shows that a Kalman filter based on the proposed state space model gives better performance that direct use of the step response data for prediction.
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  • 240
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    AIChE Journal 35 (1989), S. 250-258 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model was developed to describe the rate of reaction between chromium(III) and polyacrylamide (PAAm) that leads to the crosslinking or gelation of the polymer. Cr(III) was added directly to solutions of polyacrylamide which had a degree of hydrolysis of approximately 4%. The unreacted Cr(III) was separated from that which had reacted with the polymer by equilibrium dialysis and measured by atomic absorption.The rate of the reaction was described by an empirical model based on the assumption of invariant polymer group concentration during the reaction. The order of reaction was determined to be 1.32 for Cr(III), 0.8 for the polymer group, and -1.0 for hydrogen ion. Modifications were made to the model to allow for variation during reaction of the concentration of the polyacrylamide reactive group. The modified model accurately described the reaction rate for Cr(III) concentration ranging from 0.19 to 1.2 mM, polyacrylamide concentrations from 6.9 to 69 mM, and pH values from 4.0 to 5.5.
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  • 241
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    AIChE Journal 35 (1989), S. 267-278 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes a reaction-reactor model, utilizing alternative reaction pathways, developed to explain experimental results from the total oxidation of ethylene on a Pt/SiO2 catalyst. Transient temperature-programmed reaction and concentration-programmed reaction experiments were utilized to study the reaction through FTIR spectroscopic and surface temperature measurements combined with bulk measurements of concentration and temperature. Different elementarystep pathways were incorporated into the concentration and energy balances in performing the simulations. One pathway utilized adsorbed CO, formed from adsorbed ethylene, as the route to CO2 formation. This pathway is shown to become important under ethylene-rich conditions. The second pathway utilized the direct reaction between adsorbed ethylene and adsorbed oxygen as the path to CO2 formation. The latter route is shown to become important under oxygen-rich conditions. Finally, an example is utilized to show the advantages of the nonequilibrium elementary-step modeling approach over conventional “equilibrium” models where only one step is taken to be rate-determining.
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  • 242
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    AIChE Journal 35 (1989), S. 314-317 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 243
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    AIChE Journal 35 (1989), S. 300-310 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A predictive equation for the mutual diffusion coefficient is developed for binary solutions which contain a self-associating component. The solution is modeled as a nonideal multicomponent mixture consisting of the solvent molecules and various association complexes. The model provides for a unique mobility for each of the species present and accounts for both physical and chemical contributions to the solution thermodynamics and their effects on the diffusive fluxes. The predictions of the theory were evaluated for n-alcohols in nonpolar solvents using data for six systems at temperatures ranging from 293 to 363 K. In each case, the predictions of this theory are found to be superior to other currently available methods.
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  • 244
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    Additional Material: 5 Ill.
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  • 245
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    AIChE Journal 35 (1989), S. 332-334 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Tab.
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  • 246
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    AIChE Journal 35 (1989), S. 329-331 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    AIChE Journal 35 (1989), S. 514-518 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 248
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    AIChE Journal 35 (1989), S. 649-654 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 249
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    AIChE Journal 35 (1989), S. 347-349 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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    AIChE Journal 35 (1989), S. 673-675 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    AIChE Journal 35 (1989), S. 683-685 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 702-702 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    AIChE Journal 35 (1989), S. 853-855 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 856-860 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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    AIChE Journal 35 (1989), S. 865-868 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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    AIChE Journal 35 (1989), S. 875-875 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 257
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 259
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    AIChE Journal 35 (1989), S. 877-877 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 260
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    AIChE Journal 35 (1989), S. 877-877 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 261
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    AIChE Journal 35 (1989), S. 891-907 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A control system is designed for a copolymerization reactor using a combination of feedforward, ratio, and feedback control to regulate polymer production rate, copolymer composition, molecular weight, and reactor temperature. The solution copolymerization of methyl methacrylate and vinyl acetate in a continuous stirred tank reactor is used as an illustrative example with the kinetic parameters and reactor operating conditions obtained from the literature. The process includes equipment to recycle unreacted monomers and solvent. The recycle stream introduces disturbances to the reactor feed, which perturb the polymer properties. A feedforward control strategy is proposed to counter these disturbances, and its effectiveness is demonstrated using the model. The mathematical model is used to investigate input/output control pairings in order to identify the fundamental nature of the solution copolymerization control problem and to determine the best control system structure. The combined feedforward/feedback strategy is tested on a nonlinear model of the process for set point changes and compensation of unmeasured reactor disturbances. The performance of the control system design was quite good, and such designs have been found successful in plant operations.
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    AIChE Journal 35 (1989), S. 943-950 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been recognized that a diagnostic expert system's ability to learn from past experience will improve its diagnostic efficiency as well as make it acquire new heuristics. In this paper, we propose a failure-driven learning scheme by which the expert system automatically updates its compiled knowledge by acquiring new heuristics or refining existing heuristics. A heuristic is refined if it hypothesizes the wrong causal origin during a diagnosis. Using its deep-level knowledge of the process, the expert system draws inductive inferences from causal models to determine why the hypothesis proposed by the heuristic is inconsistent with the current state of the process. The refinement limits the applicability of the heuristic and prevents it from firing if a similar situation were to subsequently arise.
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    AIChE Journal 35 (1989), S. 666-669 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 264
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    AIChE Journal 35 (1989), S. 679-682 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 265
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 266
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    AIChE Journal 35 (1989), S. 1073-1084 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A laser capillary spectrophotometric technique (LCS), based on the method of Verhoff et al. (1969, 1977), is developed for the rapid and accurate determination of the bivariate drop size-concentration distribution for reactive liquid-liquid dispersions. The method employs a precision bore capillary, through which a sample is drawn from the mixing vessel by a vacuum pump. An appropriate light source is used to distinguish between the slugs of dispersed phase and continuous phase as the sample passes by two detection points in the capillary. The optical device is designed to measure drop size by the difference of light refraction between the two phases and drop concentration by the light absorbance of the organic phase in the drop. The new technique can automatically measure drop-size and drop-concentration distributions of thousands of drops within a few minutes. This technique can provide important information on the state of a reactive dispersion in situ and can provide information on the influence of dispersed-phase mixing effects on mass transfer and/or reactions in liquid-liquid dispersions. Further, the LCS technique provides the capability for on-line monitoring and control of units processing liquid dispersions.
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  • 267
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    AIChE Journal 35 (1989), S. 1115-1124 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The continuous-lumping method is a refinement of continuous thermodynamics which does not depend upon the continuous-mixture hypothesis. The method utilizes a generalized Fourier series expansion of a functional formulation of the equilibrium relations obtained by embedding the classical discrete equilibrium equations into generalized function space. The resulting method provides an effective means of reducing the number of parameters needed to describe a many-component, complex mixture; furthermore, the method provides a straightforward means of converting the equilibrium equations to the new parameterized form. The error associated with the reduction in number of parameters can be easily estimated using the ratio convergence test for mathematical series. The theory of the method is first presented and the method is then used in an example calculation to illustrate the advantages of the method over pseudocomponent lumping and continuous thermodynamics. The method is useful particularly for mixtures described by chromatographic data.
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    AIChE Journal 35 (1989), S. 1170-1176 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments were performed with an array of horizontal tubes, arranged in a regular equilateral triangular pattern, immersed in a fluidized bed operating at 812 K. Data are reported for heat transfer between the bed and a centrally-located tube in the array. Both total and radiative heat transfer rates were measured for superficial velocities spanning the range from packed bed conditions to over twice the minimum fluidization velocity. Results are presented for five differentsize particles. Local heat transfer values, measured around the tube periphery, and integrated averages are reported for all test conditions.Comparisons are also made between the heat transfer behavior of a tube in an array and that for a single tube in a hot fluidized bed under the same overall operating conditions. The results of this comparison suggest that the two mechanisms, gas convection and radiation, are competing effects.
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  • 269
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  • 270
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    AIChE Journal 35 (1989), S. 120-128 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The homogeneous vapor phase cracking of newly formed wood pyrolysis tar was studied at low molar concentrations as a function of temperature (773-1,073 K), at residence times of 0.9-2.2 s. Tar conversions ranged from about 5 to 88%. The tars were generated by low heating rate (0.2 K/s) pyrolysis of ∼2 cm deep beds of sweet gum hardwood, and then rapidly conveyed to an adjacent reactor for controlled thermal treatment. Quantitative yields and kinetics were obtained for tar cracking and resulting products formation. The major tar conversion product was carbon monoxide, which accounted for over two-thirds of the tar lost at high severities. Corresponding ethylene and methane yields were each about 10% of the converted tar. Coke formation was negligible and weight-average tar molecular weight declined with increasing tar conversion. A first-order distributed activation energy model more closely correlated tar conversion kinetics over a wider range of reaction conditions than did a single-reaction model.
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    AIChE Journal 35 (1989), S. 129-138 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study of the flow of viscous liquids contained in an open cavity driven by a moving wall has been undertaken as a first step toward understanding interphase heat and mass transport in polymer processing equipment where rolling pools of liquid are generated. Solutions to the equations of motion for creeping flow in cavities of different aspect ratios were obtained using a finite-differences technique for circumstances when the wall moves in the same direction as the gravitational field.Experimental studies of the flow patterns in cavities of various aspect ratios were found to be in good agreement with the creeping flow predictions for cavity Reynolds numbers Re 〈 50 and aspect ratios a 〈 1. The structure of the flow in this geometry was found to be similar to that in closed cavities of the same shape. The position and strength of the principal vortex were observed to be nearly independent of the existence of a free surface, and the gas-liquid interface was found to significantly stabilize the rotational motion in shallow cavities.
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    AIChE Journal 35 (1989), S. 139-147 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Knp ≫ 1 gas-kinetic approach of Waldmann (1959, 1961) is extended to predict the thermophoretic properties of nonspherical aerosol particles, and massive nonspherical gas molecules. Calculations are presented for sphero-cylindrical particles (molecules) of arbitrary aspect ratio, L/R, predicting that in a local temperature gradient grad T they will thermophoretically drift: (i) more rapidly when their major axis is aligned with -grad T; (ii) at a velocity different from that of a sphere of radius R equal to the cylinder radius; (iii) at an angle with respect to -grad T when their major axis is not parallel to, nor perpendicular to, -grad T; and (iv) without a net torque tending to orient the particle with respect to -grad T. Important corollaries are that nonspherical particles in a temperature gradient should also experience new thermophoretically-induced coagulation mechanisms. We predict that the orientation-averaged thermal diffusion factor αT should increase approximately linearly with particle (molecule) length.
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    AIChE Journal 35 (1989), S. 318-320 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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    AIChE Journal 35 (1989), S. 325-328 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 449-458 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An analytical model has been constructed to predict the birefringence level in an injuection-molded disk with direct application to optical disk substrates. The model incorporates simplified analyses for the flow in a center-gated cavity during the filling stage, the heat transfer during the cooling stage, and the stress relaxation following the cessation of flow at the end of the filling stage of the injection-molding cycle. The stress relaxation process is analyzed with the integral constitutive equation of Wagner and the residual stresses are converted to retardation via the stress-optical law. Predictions of normal retardation profiles are in line with experimental data and the general effects of melt temperature, mold temperature, and injection speed are closely captured by the model. By contrast, the observed transverse retardation is not in accord with the predicted response. This discrepancy is attributed to the fact that the transverse retardation is induced by cooling stresses and thus cannot be explained in terms of a flow stress mechanism employed in the present analysis.
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  • 276
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    AIChE Journal 35 (1989), S. 507-510 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 277
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    AIChE Journal 35 (1989), S. 559-572 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The problems of stability and performance for nonlinear feedback systems are examined. A hybrid approach that combines input-output and state-space theories is proposed. Within this framework the notions of dynamic gain and dynamic incremental gain of a nonlinear operator are reexamined and their inability to accurately reflect the dynamic behavior of a physical system is demonstrated. The concepts of dynamic gain and dynamic incremental gain over sets are introduced and their connection to a physical system's dynamic behavior is established. Theorems are developed that allow the systematic computation of these gains through nonsmooth optimal control theory. Illustrative examples are provided throughout the paper.
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  • 278
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    AIChE Journal 35 (1989), S. 645-648 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 279
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    AIChE Journal 35 (1989), S. 821-830 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed investigation of the dependence of the transient behavior of limestone particles reacting with SO2 in the presence of oxygen on the pore structure properties of the calcined solid is presented. Experimental reactivity and pore structure data were obtained for two highpurity limestones that yield calcines of qualitatively similar distribution of pore size but of different capacity for SO2 removal. Experiments were carried out over a wide range of particle size and temperature so as to investigate the effects of intraparticle mass transport limitations on the process. The results obtained showed strong dependence of the transient behavior of reacting particles of calcined limestone, and consequently of their sorptive capacity for SO2 removal, on their initial pore size distribution and on the resistance for intraparticle mass transport - which is also determined to a certain extent by the pore size distribution. The experimental results were found to be in agreement with the predictions of a mathematical model for gas-solid reactions with solid product involving porous solids of distributed pore size. The findings point to the conclusion that the evaluation of limestones proposed for use as sorbents for controlling SO2 emissions should be based on the size distribution and interconnectedness of the pores of their calcines and not only on their average structural properties (porosity and surface area).
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  • 280
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    AIChE Journal 35 (1989), S. 861-864 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 281
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  • 282
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    Keywords: Chemistry ; Chemical Engineering
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    Additional Material: 2 Ill.
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  • 283
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    AIChE Journal 35 (1989), S. 1224-1226 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 284
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    AIChE Journal 35 (1989), S. 1271-1281 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steady- and unsteady-state theories for interfacial mass transfer are used to model gas absorption with second-order, reversible reaction and the absorption of CO2 into aqueous MDEA (methyldiethanolamine). The latter case represents a system of industrial interest, having both finite rate and equilibrium reactions. Steady-state theories studied are film theory, simplified eddy diffusivity theory, and an approximation to surface renewal theory. Higbie's penetration and Danckwert's surface renewal theories are the unsteady-state theories reviewed. The Nernst-Planck equations for diffusion and reaction in ionic systems are solved numerically using orthogonal collocation on finite elements. Comparisons are made between the absorption enhancement factor obtained for all theories. The applicability of approximate methods of solution for absorption with chemical reaction is also discussed.
    Additional Material: 10 Ill.
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  • 285
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    AIChE Journal 35 (1989), S. 1315-1327 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of fluctuating flow on the electrodeposition of binary alloys is analyzed by numerically solving the transient Navier-Stokes and species continuity equations for a rotating disk electrode system. Timeperiodic modulations of the flow field and the electrode potential are studied and shown to induce periodic deposition rates for a mass-transfer-limited species and an activation-limited species, respectively. Dimensionless groups are formulated to characterize the operating regimes, where composition-modulated alloys electrodeposit from a single electrolyte and where fluctuating flow influences the composition distribution of the deposit. It is shown that changing the phase angle difference between the flow and potential modulation waveforms can modify the composition gradients in the deposited alloy, whereas other features of the alloy, such as the total composition variation, are affected less by fluctuating flow.
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  • 286
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    AIChE Journal 35 (1989), S. 1365-1369 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 287
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    AIChE Journal 35 (1989), S. 1380-1384 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 288
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  • 289
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    AIChE Journal 35 (1989), S. 1395-1398 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 290
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    AIChE Journal 35 (1989), S. 1497-1508 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For particle deposition from log-normal polydispersed aerosol streams by one or more of several mechanisms described by piecewise-power-law mass transfer coefficients, we derive useful relations between actual total mass deposition rates and the ‘reference’ rate one would calculate by imagining that all particles in the mainstream population had the average particle volume v(=φp/Np). Included here are diffusion or inertial mechanisms for laminar- or turbulent-boundary layers, free-molecular or continuum diffusion at high Peclet numbers of dense spherical particles, or fractal agglomerates. The mainstream particle volume distribution is considered to be log-normal with arbitrary ‘spread’ parameter, thereby generalizing earlier results for “coagulation-aged” (self-preserving) distributions. Further generalizations include transitions between important particle transport mechanisms, opening the way to efficient, finite-analytic methods for predicting mass deposition rates for arbitrary, size-dependent particle capture efficiencies.
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  • 291
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    AIChE Journal 35 (1989), S. 635-644 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This work provides a new method for calculating phase equilibria for systems where conventional activity-coefficient models are not suitable. A procedure is presented for superimposing ionic effects on a conventional equation of state for nonelectrolytes. A modification of Born's equation is used to describe charging the ions; ion-ion interactions are described with the Mean Spherical Approximation, coupled with an adjustable salt/solvent parameter that is obtained from osmotic-coefficient data at room temperature. The equation of state is used to predict gas solubilities in aqueous salt solutions at high pressures. While this method produces qualitative agreement with the experimental solubility data, quantitative agreement requires a salt/ gas parameter obtained from Setchenow-constant data. When Setchenow constants are used, agreement with experiment is good except at high salt concentrations, where salting-out is usually underpredicted. Good results are obtained for phase equilibria in a natural-gas/brine system at high pressures.
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  • 292
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    AIChE Journal 35 (1989), S. 625-634 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general mathematical model is presented for the noncatalytic reaction between a porous solid and a gas with solid product formation under conditions controlled by intraparticle diffusion. The model has been formulated in general terms so as to allow the incorporation of specific details pertaining to actual systems. The formulation assumes that the gaseous reactant diffuses through the pore space of the particle followed by diffusion through the product layer. The resulting equations are solved numerically.This model has been used to predict conversion-time curves for the atmospheric oxidation of iron disulfide contained in porous solids. The predicted curves are in excellent agreement with the experimental data. In particular, it produces accurate estimates for the conversion rates of iron disulfide at different temperatures.
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  • 293
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    AIChE Journal 35 (1989), S. 343-346 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 294
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    AIChE Journal 35 (1989), S. 662-665 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Tab.
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  • 295
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    AIChE Journal 35 (1989), S. 365-372 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The approximate equations of Hassler and Brunner and of van Domselaar are often used to deduce the capillary pressure curve of a porous medium from centrifuge data. The use of these equations restricts the centrifuge method to short samples. Also, these equations require differentiation of data. We report here methods to determine the capillary pressure curve by the midpoint and least-squares solution of the fundamental equation, relating the average saturation S1 of liquid in the porous medium to the capillary pressure Pc1 at the end of the sample nearest the axis of rotation. The methods do not require differentiation of data and are not restricted to short samples. We introduce and evaluate an approximation based on an exact result derived by Rajan. This new approximation requires the same inputs as do the Hassler-Brunner and the van Domselaar approximations, but it is accurate over a wider range of sample sizes. In addition, an approximate solution which can be used to estimate capillary pressure curves for long cores is developed.
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    AIChE Journal 35 (1989), S. 373-384 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steady states with different flow rates and temperature profiles may exist in different tubes of a multitube packed-bed reactor due to the coupling among the species, energy and momentum balances, and the change of physical properties with temperature and pressure. Under typical operating conditions if no axial conduction of heat occurs thermoflow multiplicity can be found only for unrealistically high heats of reaction and/or over a very narrow range of exit pressures. However, accounting for the finite but small heat conduction in the reactor tubes leads to multiplicity for typical parameters and a reasonable range of exit pressures. Cooling tends to decrease the region of parameters for which the multiplicity occurs.
    Additional Material: 16 Ill.
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  • 297
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    AIChE Journal 35 (1989), S. 423-428 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A technique based upon transmission FTIR to obtain rate constants for adsorption and desorption over supported metal catalysts has been developed and tested. The technique requires the use of a sinusoidal perturbation function imposed on steady state linearized adsorption-desorption kinetics. The measurement of a phase lag between the sinusoidal inlet gas phase forcing concentration and the response of surface coverage, together with a measurement of the maximum amplitudes of the forcing function and surface response enable the calculation of the relevant adsorption and desorption rate constants.The technique has been successfully applied to the measurement of both adsorption and desorption rate constants for CO adsorbed on a 1% Pt/SiO2 catalyst. The values obtained for these rate constants at 343 K were: Ka = 0.147 s-1 and Kd = 7.28 × 10-3 s-1. A sticking coefficient corresponding to the adsorption of weakly bonded CO on Pt under conditions of high CO surface coverage was obtained.
    Additional Material: 5 Ill.
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  • 298
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    AIChE Journal 35 (1989), S. 429-442 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A multiphase model for the flow of dense, noncolloidal, settling slurries through horizontal pipelines, and an associated Galerkin-finite element numerical scheme to carry out computer simulations based on the model, were developed. The principal elements of the model are: equations for estimation of the velocity distributions for each component; and those for the concentration distributions. In the former, which are derived from the local volume-averaged, time-smoothed conservation of mass and momentum equations, the total stress is comprised of components to account for interparticle and particle-boundary as well as viscous and turbulent interactions. The governing equations for the concentration distributions are derived similarly from the convective diffusion equation, with the eddy diffusivity modified to account for the presence of the solid particles. Numerical simulations and detailed comparisons with experiment for the flow of gypsum, coal, crushed glass, sand and gravel, covering particle sizes from 38.3 μm to 13,000 μm, and pipe diameters from 4 cm to 49.5 cm, were carried out. The agreement between model prediction and experiment is excellent.
    Additional Material: 6 Ill.
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  • 299
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    AIChE Journal 35 (1989), S. 459-465 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During inflammation, leukocytes cross the blood vessel wall and migrate to the inflammatory site in response to gradients of diffusible chemical attractants produced there. This directed migration response to a chemical gradient, termed chemotaxis, can be studied experimentally in the Millipore filter assay. We have applied a mathematical model to analyze cell population migration in the assay in terms of two parameters analogous to molecular transport coefficients. The random motility coefficient, μ, reflects the cell response to uniform concentrations of chemical attractant, while the chemotaxis coefficient, χ, reflects the response to a concentration gradient. We have measured μ and χ by comparing theoretical cell density profiles to those measured in the assay. Both parameters vary as a function of the attractant concentration; μ ranges from 10-10-10-9 cm2/s and χ ranges from 10-100 cm2/s.M for the attractant tested. These values agree with ones predicted from a priori theoretical relationships for μ and χ. Quantitation of the Millipore filter assay provides a framework for the quantitation of analogous cell transport systems such as a composite assay simulating cell migration across the vessel wall.
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    AIChE Journal 35 (1989), S. 686-689 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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