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  • ZIB Catalog
  • Articles: DFG German National Licenses  (3,542)
  • 2020-2022
  • 1985-1989  (3,542)
  • 1880-1889
  • Chemical Engineering  (3,542)
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  • ZIB Catalog
  • Articles: DFG German National Licenses  (3,542)
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Years
Year
  • 201
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 97-103 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Given the intrinsic kinetics, the tortuosity factor of a Ni/MgAl2O4 catalyst was determined under reaction conditions by minimizing the sum of squares of residuals of the experimental and the simulated conversions. The parallel cross-linked pore model with uncorrelated pore size distribution and orientation was used in the calculation of the effective diffusivities. A modified collocation method was used to obtain the partial pressure profiles of the reacting components in the catalyst pellet. The simulation of the experimental reactor during the optimization of the tortuosity factor also yielded the effectiveness factors of the reactions. The results of the simulation of an industrial steam reformer are also discussed.
    Additional Material: 7 Ill.
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  • 202
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    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 104-108 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particle to gas heat transfer studies were carried out for the exothermic benzene hydrogenation and endothermic cyclohexane dehydrogenation reactions on the same catalyst bed. A recirculation type reactor and eggshell type commercial platinum on alumina catalyst were used. When the thermodynamic value for the heat of reaction is used for both reactions in the steady-state energy balance, local JH factors for the exothermic reaction were found to be, in general, higher than those for the endothermic reaction. This was attributed to product molecules leaving the catalyst surface with excess vibrational energy, which implies that the actual heat of reaction would be different than the thermodynamic value used in the JHfactor calculations. The study also indicated significant variations in the local JH factors; these were attributed to variations in the linear velocity in the radial direction.
    Additional Material: 7 Ill.
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  • 203
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 109-119 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bimetallic Mo-Fe and Mo-Co sulfide clusters were anchored on Al2O3 and used for CO hydrogenation. In addition to methane, significant amounts of dimethyl ether were produced. The reaction orders obtained from power rate laws for methanation indicated that the surfaces of the catalytic ensembles were not completely saturated by CO, in contrast to the observations for most conventional CO hydrogenation catalysts. A kinetic analysis and parameter estimation was performed to identify the rate-determining step for methanation. A catalytic cycle was postulated that could account not only for the formation of methane and higher hydrocarbons, but also for dimethyl ether as a primary product.
    Additional Material: 9 Ill.
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  • 204
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 88-96 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intrinsic rate equations were derived for the steam reforming of methane, accompanied by water-gas shift on a Ni/MgAl2O4 catalyst. A large number of detailed reaction mechanisms were considered. Thermodynamic analysis helped in reducing the number of possible mechanisms. Twenty one sets of three rate equations were retained and subjected to model discrimination and parameter estimation. The parameter estimates in the best model are statistically significant and thermodynamically consistent.
    Additional Material: 9 Ill.
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  • 205
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    Hoboken, NJ : Wiley-Blackwell
    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.
    Additional Material: 10 Ill.
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  • 206
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    Hoboken, NJ : Wiley-Blackwell
    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.
    Additional Material: 10 Ill.
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  • 207
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 213-222 
    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 stable Kalman filter predictor (KFP) is developed which generates minimum variance estimates of the future outputs {y(t + i | t), i = 1, … d} of stochastic, single-input/single-output processes with time delay, d. The predicted outputs are used for time delay compensation and in the design of a predictive feedback controller. An innovation model analysis is used to convert the state space formulation to transfer function form and to show the relationship between the KFP, the Smith predictor, and the internal model controller. A modified KFP includes a disturbance model, and eliminates offset due to deterministic disturbances (e.g., steps) and modeling errors. Simulation results show that the modified KFP also predicts the disturbances and gives significantly better performance than the Smith predictor, particularly in the presence of process and measurement noise.
    Additional Material: 17 Ill.
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  • 208
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 230-240 
    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 unsteady, impulsive motion of a compressible bubble expanding out of a constricted capillary is quantified with a macroscopic momentum balance. Numerical solution demonstrates the importance of the Ohnesorge number, the geometry of the constriction, the length of the initial gas bubble, and the surface tension, density, and unconstricted capillary radius, which combine to form a characteristic scaling time. Experimental data for the position of the bubble front as a function of time confirm the theoretical result when the time scale for the bubble jump is longer than that required to achieve fully developed parabolic flow. Theory also predicts the capillary number of the bubble jump which, in conjunction with previous theoretical results, determines the time to snap-off of gas bubbles moving through constricted capillaries. Excellent agreement is found with existing experimental data for Ohnesorge numbers ranging from 5 × 10-3 to 0.3.
    Additional Material: 11 Ill.
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  • 209
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1659-1666 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental results are reported for equilibrium adsorption and diffusivities of CH4, C2H6 and CO2 in type A zeolite containing mixed Na and K cations ranging from 0 to 100% in composition, at two temperatures and 1 atm. Two simple theoretical solutions are given for the diffusivity. One is for diffusion with pore (aperture) blocking using the effective medium approximation, which is readily available from the literature on percolation theory. The other is a kinetic solution derived in this work for cavities containing heterogeneous sites, which is a case where the percolation theory is not applicable. The equilibrium adsorption results show that K+ has a preference for the aperture (or pore-blocking) sites (site type II), and these results are interpreted by the bond percolation theory. The diffusivity results are successfully interpreted by the poreblocking theory in zeolites containing less than 25% K+ and by the kinetic theory for zeolites with higher K+ contents.
    Additional Material: 11 Ill.
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  • 210
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1894-1894 
    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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  • 211
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    Hoboken, NJ : Wiley-Blackwell
    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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  • 212
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1916-1916 
    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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  • 213
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1953-1961 
    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 previously developed method (Sotirchos and Burganos, 1988) for studying isobaric multicomponent diffusion in a class of capillary networks is extended for application to the problem of convection and diffusion of gaseous mixtures in porous media. The method is used to develop flux models for nonisobaric transport in capillary structures, which are then compared with corresponding “three-parameter” dustygas models. Results for discrete and continuous pore size distributions show that the predictions of the developed flux models depend strongly, both qualitatively, and quantitatively, on the procedure used to average the dusty-gas model equations for a single pore over the pore-size distribution.
    Additional Material: 7 Ill.
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  • 214
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 2003-2012 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ceramic particle formation processes have been studied using SiO2 as a model compound. Silica particles have been synthesized in a counterpropagating diffusion flame reactor, in which in-situ measurements of particle size and number density have been made. In addition, the time-temperature history of the particle field has been calculated from a flame simulation. Numerical simulations using moment and sectional methods for particle formation have been applied and compared to the experimental measurements. The simulations for the particle formation assume a kinetically-constrained approach, allowing a simple representation of nucleation, surface growth and coagulation. The results suggest that, if the source rates are known well enough, particle formation of low vapor pressure species can be predicted. Both models do well in predicting the gross features of particle formation (number density and mean particle size), although the moment solution does a poor job of predicting the polydispersity effects during periods of high monomer generation rates.
    Additional Material: 14 Ill.
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  • 215
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    Hoboken, NJ : Wiley-Blackwell
    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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  • 216
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    Hoboken, NJ : Wiley-Blackwell
    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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  • 217
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    Hoboken, NJ : Wiley-Blackwell
    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.
    Additional Material: 9 Ill.
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  • 218
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 353-353 
    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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  • 219
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 406-414 
    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 pipeline mixing of two fluid streams by turbulent jet injection normal to the pipeline has been studied theoretically and experimentally. A simple scaling law for the second moment of the tracer concentration within the pipeline is proposed for the first fifteen pipe diameters down-stream from the injection point. The similarity solution is derived by assuming that the tracer diffuses in a weak compound jet moving parallel to the pipeline axis. The theoretical results are correlated with all of the available experimental measurements. The results indicate that the second moment of the tracer concentration decreases with increasing jet momentum and distance from the injection point such that M = 0.25. (lm/D)-2 (x/D)-4/3.
    Additional Material: 9 Ill.
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  • 220
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    Hoboken, NJ : Wiley-Blackwell
    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
    Additional Material: 5 Ill.
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  • 221
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 702-702 
    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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  • 222
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 793-802 
    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 piston reactor has been developed to examine some aspects of particle formation during the pyrolysis of silane (SiH4). This reactor generates conditions intermediate between a static pyrolysis reactor and a shock tube reactor. It effectively excludes contributions of wall reactions to the pyrolysis experiments. The apparent kinetics for this reactor do not conform to values published in the literature. A model that incorporates silane-particle reactions can account for the deviations. In addition, emission of visible light accompanies the sooting reactions. The source of this emission seems to be the sum of incandescence from the hot particles and continuum radiation from another source.
    Additional Material: 12 Ill.
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  • 223
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 849-852 
    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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  • 224
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 873-874 
    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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  • 225
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    Hoboken, NJ : Wiley-Blackwell
    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
    Type of Medium: Electronic Resource
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  • 226
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    Hoboken, NJ : Wiley-Blackwell
    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
    Type of Medium: Electronic Resource
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  • 227
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    Hoboken, NJ : Wiley-Blackwell
    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
    Type of Medium: Electronic Resource
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  • 228
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    Hoboken, NJ : Wiley-Blackwell
    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.
    Additional Material: 13 Ill.
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  • 229
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    Hoboken, NJ : Wiley-Blackwell
    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.
    Additional Material: 3 Ill.
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  • 230
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    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.
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  • 231
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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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  • 232
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    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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  • 233
    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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  • 234
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    Hoboken, NJ : Wiley-Blackwell
    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
    Type of Medium: Electronic Resource
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  • 235
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 908-922 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Erosion in bubbling fluidized-bed combustors is a serious issue that may affect their reliability and economics. Available evidence suggests that the key to understanding this erosion is detailed knowledge of the coupled and complex phenomena of solids circulation and bubble motion. A thin transparent “two-dimensional” rectangular fluidized bed with an obstacle served as a rough model for a fluidized-bed combustor. This model was studied experimentally and computationally using two hydrodynamic equation sets. The computed hydrodynamic results agree reasonably well with experimental data. Bubble frequencies and sizes compare well with those obtained from analyzing a high-speed motion picture frame-by-frame. Time-averaged porosities computed from both models agree with time-averaged porosity distributions measured with a gamma-ray densitometer. The principal diferences between the data and the computations in this paper are due to asymmetries present in the experiment and to the simplified solids rheology used in the hydrodynamic models.
    Additional Material: 13 Ill.
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  • 236
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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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  • 237
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    AIChE Journal 35 (1989), S. 42-52 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monte Carlo simulation is used to calculate partition coefficients for rigid, axisymmetric, nonspherical molecules in various pore geometries. Novel quantitative results are presented for a variety of molecule and pore shapes, including pores of nonuniform cross-section such as the interstitial space within granular and fibrous materials.Quick estimation methods for obtaining partition coefficients are discussed, and the effects of molecule and pore wall curvature are described in detail. A boundary perturbation analysis is used to derive easy-to-use formulas for a variety of molecule shapes in circular pores.
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  • 238
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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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  • 239
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  • 240
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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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  • 241
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    AIChE Journal 35 (1989), S. 481-489 
    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 semitheoretical group contribution method for predicting pure-compound second virial coefficients is proposed. An expression for the second virial coefficient, expressed as the product of a nonpolar and a polar contribution, is derived using statistical thermodynamic concepts and an approximate form for the radial distribution function. For polar compounds the nonpolar contribution is assumed to be given by the Tsonopoulos correlation with the nonpolar acentric factor defined by Thompson and Braun. The polar contribution is represented by an energetic term expressed in terms of group contributions. Second virial coefficient predictions for strong polar and associating systems are comparable with those obtained with the correlations of Tsonopoulos and Hayden and O'Connell. Cross-second virial coefficients for mixtures obtained using well-defined molecular mixing rules compare well with literature values.
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  • 242
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    AIChE Journal 35 (1989), S. 511-513 
    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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  • 243
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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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  • 244
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    AIChE Journal 35 (1989), S. 549-558 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Configuration of feedback loops between input and output variables of a given plant constitutes a subtask of control system synthesis. In the past, this subtask has been tackled through direct decomposition of either the process or the set of input-output variables. Linear interaction analysis has been used in both approaches to assess and minimize sub-system interactions. Since most chemical processes exhibit nonlinear behavior, it is evident that a measure is needed for assessment of interactions in the presence of system nonlinearities. In this paper we focus on input-output variable set decomposition and introduce the notion of nonlinear block relative gain (NBRG) as a nonlinear interaction measure. Both the statistic and dynamic versions of NBRG are discussed, and a computational procedure is presented for their evaluation. Direct simulations on a CSTR verify the interactions predicted by NBRG for different feedback configurations. Moreover, nonsymmetry of the effect of one loop on another, a fact not captured by the linear BRG, is accurately predicted by NBRG.
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  • 245
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    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.
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  • 246
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    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.
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  • 247
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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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    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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    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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    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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    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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  • 252
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    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.
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    AIChE Journal 35 (1989), S. 775-792 
    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 quantitative model of softening coal pryolysis is developed and tested against observed behavior. The model treats intraparticle transport of gases and metaplast throughout the softening stage of pyrolysis via growth of bubbles uniformly dispersed in the molten coal. The model quantitatively describes the transient softening behavior including the initiation, duration, and magnitude of plasticity and swelling of the particle. The model kinetic parameters are derived from experiments, in which a highly softening Pittsburgh No. 8 bituminous coal was pyrolyzed, and total weight loss, and yields and molecular weight distributions of tars and pyridine extractables of cooled chars were measured. Model predictions of effects of pressure, particle diameter and temperature on tar yields and weight losses, of effects of pressure on swelling ratio, and of effects of heating rate on plasticity are presented. The model provides good fits to the laboratory data and predicts trends in pyrolysis behavior in good qualitative accord with expectations based on published data.
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    AIChE Journal 35 (1989), S. 845-848 
    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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  • 255
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    AIChE Journal 35 (1989), S. 714-724 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using the principles of conservation of mass and momenturn for each phase, a theory is developed for describing quantitatively the sedimentation of colloidal particles in vessels having electrodes that are inclined to the vertical.As a limiting case, a kinematic settling formula was derived that describes the motion of settling fronts of colloidal alumina particles suspended in tetralin as a function of angle of inclination and strength of applied electric field in terms of electrophoretic mobilities. A hydrodynamic computer model shows the flow patterns and settling behavior of such lamella settlers with and without an applied electric field. The predicted motions of the settling fronts and the thicknesses of the clear boundary layers above the upper wall of the inclined vessels globally agreed with the experimental observations.
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  • 256
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    AIChE Journal 35 (1989), S. 755-763 
    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 loading of organic molecules adsorbed on high surface area carbon materials can be influenced by the potential of the surface. This phenomenon can form the basis for carbon regeneration and for separation processes. A theoretical treatment demonstrates that adsorption loading becomes more sensitive to potential change when the double layer capacitance of the interface and the size of the organic species are increased. An experimental method was developed to estimate isotherm parameters. The technique was demonstrated on model adsorbates, pentanol and heptanol. The values of the measured isotherm parameters (B = 3.4-9.1 V-2: Emax = 0.36-0.5 V vs. Hg/Hg2 SO4) are in the range of expected values based on literature values for similar systems. Although only 5% of activated carbon surface area was shown to be electrochemically accessible, it still has ten times the area available for electrosorption as compared to the graphite, thus making it attractive for industrial application.
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  • 257
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  • 258
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  • 259
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    AIChE Journal 35 (1989), S. 1-29 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plasma processing has emerged as an important technology for the deposition and etching of thin solid films in the manufacture of microelectronic devices. In fact, much of the progress achieved to date in device miniaturization would have been much more difficult without the unique characteristics of plasma processes. It is anticipated that future progress will continue to rely heavily on plasma technology. Although plasma chemical reactors are widely used, a lack of fundamental understanding has resulted in heavy reliance on empiricism in process design and control. The complexities inherent in any chemical reactor are compounded in plasma processing by the presence and active participation of the discharge in both gas phase and surface chemical processes. This has resulted in a technology that is sensitive to many design and operating parameters. A large parameter space gives process engineers flexibility in tailoring process conditions to meet objectives. However, without fundamental insight into the key physical and chemical processes, reactor design and control cannot be based on systematic, rational procedures. The purposes of this review are to introduce chemical engineers to plasma processing practice and phenomenology; to outline the progress made to date in fundamental studies of discharge physics and chemistry; to indicate areas in which chemical engineers must expand their traditional training to participate in plasma processing research; and finally to suggest how established chemical engineering methodology can be applied to plasma chemical reactors.
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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. 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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    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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  • 264
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    AIChE Journal 35 (1989), S. 148-158 
    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 computer-generated slim tube randomly packed with spheres of almost uniform size is used to model single-phase flow in a packed tube with a small tube diameter to particle diameter ratio, R. To obtan a detailed description of its morphology, the slim packed tube is first tessellated into tetrahedra in the interior, and pentahedra near the walls of the tube. Then, the pore space is represented by a network of interconnected circular and triangular sinusoidal flow channels. The size and length of each channel, as well as their interconnectivity, are exactly known. In addition, porosity and solid surface area per unit volume of the porous medium are determined as a function of distance away from a wall. These data suggest that the presence of the walls has two counteracting effects on fluid flow. A higher porosity promotes flow along the walls but a higher surface area per unit volume hinders it. To confirm this prediction, experimental permeability data are obtained for tubes with R between 2.5 and 40. For R 〉 25, the permeability is the same as that of a large diameter tube, k∞. Between 8 and 25, the permeability can be larger or less than k∞. The way the tube is packed determines whether the higher porosity or surface area dominates in the wall region, and thus higher or lower permeability. Below R = 8, the confining walls cause a marked increase in overall bed porosity and the permeability is always larger than k∞. Theoretical predictions of the permeability of such very slim tubes are in good agreement with experimental data.
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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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  • 266
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    AIChE Journal 35 (1989), S. 177-186 
    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 long-wave equation for film thickness as a function of position is derived for a general case incorporating viscous, surface tension, and interfacial shear effects. The derivation considers both the parabolic and the power-law velocity profiles. The analysis is aimed at revealing the wave velocity that induces infinitely long (homoclinic) periods as well as substrate thickness and wave peak amplitude. Phase plane analysis shows that at Re ≫ 1, due to time-scale separation, the homoclinic velocity is near that at the Hopf bifurcation. That enables analytical derivation of the wave characteristics.Comparison with experimental results in the range of Re-310-3, 100 with countercurrent gas flow, shows encouraging agreement. At very high Re the wave velocity suggests the onset of turbulence, in agreement with theory. Phase plane analysis predicts also that the wave shape consists of a simple peak with a steep front, with short waves riding on the main wave at low Re.
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    AIChE Journal 35 (1989), S. 196-212 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Numerical solutions for the creeping motion of a spherical particle in a linear axisymmetric straining flow normal to a deformable interface are presented for a range of viscosity ratios, capillary numbers, and Bond numbers. The parameter ranges investigated have applications in areas of flotation (small interface deformation) and material processing (large interface deformation). The accuracy of previous solutions for flotation problems which neglect interface deformation is considered, along with the magnitude and form of interface deformation “defects” which may appear in material processing applications involving fluids containing bubbles or small particles.
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    AIChE Journal 35 (1989), S. 259-266 
    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 dynamic model is derived for simultaneous, homogeneous and heterogeneous, first-order reactions in a slurry reactor. The theory is applied to experimental data for the oxidation (with gaseous oxygen) of aqueous sulfite solutions which is first order in oxygen and zero order in sulfite. The homogeneous reaction is very slow at low pH (2-3) where the sulfur exists as dissolved SO2 or HSO3-, even when cobalt is added as a homogeneous catalyst. At higher pH (7-8.5), considerable homogeneous reaction occurs with and without cobalt ions. Here the predominant species are SO3= and HSO3-. Activated carbon is not a heterogeneous catalyst at pH 7 or 8.5, but is responsible for nearly all the reaction at the low pH values. Analysis of the heterogeneous data indicates that the surface reaction between adsorbed oxygen and SO2 controls the rate rather than adsorption of oxygen.
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    AIChE Journal 35 (1989), S. 279-286 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to describe the translational diffusion of polymers in dilute solution, an elastic dumbbell model is used for which the effects of both hydrodynamic interaction and a nonlinear connector force are treated in a self-consistently averaged form. For this model, the diffusion tensor in the presence of a homogeneous flow field is obtained from (i) the mass flux caused by concentration gradients, (ii) the average polymer velocity caused by external forces, and (iii) the mean-square displacement of a polymer caused by the Brownian forces. From the second and third approaches the same expression for the diffusion tensor is found, whereas a different expression is obtained from the first approach. This means that the Nernst-Einstein equation cannot be generalized to the case of flowing solutions. The model predictions for the diffusion tensors in steady shear flow are discussed in detail.
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    AIChE Journal 35 (1989), S. 287-292 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Multitubular reactors of the heat exchanger type are commonly used to carry out highly exothermic reactions. Two of the main goals, when designing this type of reactor, are to guarantee a safe operation and to minimize the reactor length. Therefore, these concepts are used here as criteria for comparing the performance of the three most common cooling-medium flow arrangements. The analysis of the parametric sensitivity behavior, as well as that of some related measures, indicates that, at least from the steady-state standpoint, the cocurrent arrangement should be considered the most attractive alternative.
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    AIChE Journal 35 (1989), S. 311-313 
    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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  • 272
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    AIChE Journal 35 (1989), S. 293-299 
    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 model proposed by Chen et al. for treating nonideality in concentrated electrolyte solutions has been extended to the correlation of the densities of solutions of single electrolytes (1:1, 2:1, 1:2, and 2:2) in terms of Chen's energy interaction parameters τca,m and τm,ca. At any single temperature, only three adjustable parameters, V20 (the partial molar volume of the solute at infinite dilution), and the pressure derivatives (δτca,m/δp)T and (δτm,ca/δp)T are required for correlating the density as effectively as the conventional treatment employing a power series in (molality)1/2. For some electrolytes, only the latter two parameters are required, as tabulated V20 values also lead to satisfactory correlations. The treatment can be extended to cover the temperature range 0-100°C, using either τca,m and τm,ca values derived from activity or osmotic coefficients, or constant τm,ca and τca,m values, but the irregular variation with temperature of the pressure derivatives precludes their representation by simple analytical functions, and individual values of the pressure derivatives at each temperature are necessary.
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  • 273
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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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  • 274
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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
    Additional Material: 5 Ill.
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  • 275
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    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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  • 276
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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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  • 277
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    AIChE Journal 35 (1989), S. 355-364 
    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 conducted to study the hydrodynamics of a gas-liquid-solid fluidized bed containing low-density particles. The density and size of the particles employed were comparable to those ordinarily encountered in fluidized-bed bioreactors for either wastewater treatment or fermentation. A dual resistivity probe and a conductivity probe were employed to study the axial holdup of gas and liquid phases and the bubble size distribution. The behavior of the axial holdup distribution for solid, gas, and liquid phases is reported. A mechanistic model, based on solids entrainment and deentrainment mechanisms by bubbles, is developed to describe the behavior of the axial solids holdup distribution. The model is shown to satisfactorily account for the experimental data.
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  • 278
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    AIChE Journal 35 (1989), S. 415-422 
    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 non-Newtonian viscosities of polymerically stabilized colloidal suspensions are usually predicted and correlated on the basis of data and scaling principles for Brownian hard spheres. Here, the specific effect of the stabilizer layer is investigated using suspensions of monodisperse PMMA particles with a chemically attached stabilizer layer. The ratio between particle radius and stabilizer layer thickness is changed between 5 and 61. At high values of this ratio the data show Brownian hard sphere behavior. At lower values deviations appear. As a first approximation, the “softness” of the particles can be characterized through the concentration at maximum packing. A more detailed comparison with hard sphere data provides a measure for softness that changes with concentration and shear rate. A theoretical estimate of the concentration effect is in line with the experiments. The critical shear stress (or Peclet number) is not a constant but goes through a maximum when the concentration is increased.
    Additional Material: 7 Ill.
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  • 279
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    AIChE Journal 35 (1989), S. 393-405 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas holdups (∊GR) and liquid-phase volumetric oxygen transfer coefficients (kLaT) were measured for a bubble column (BC) and three different external-circulation-loop airlift (ECL-AL) fermentors of 50 to 60 L working volume, using viscous non-Newtonian aqueous solutions of various carboxymethylcelluloses. Some measurements also were done with a viscous Newtonian system (51.8 wt. % sucrose solution).Discussed in this paper are correlations of ∊GR and kLaT with riser superficial gas velocity (0.02 ≦ UGR ≦ 0.26 m/s), the ratio of the downcomer and riser crosssectional areas (0[BC] ≦ Ad/Ar ≦ 0.444), and the effective viscosity of the liquid phase (0.02 ≦ ηeff ≦ 0.5 Pa · s), over the parameter ranges indicated. It is shown that both ∊GR and KLaT are highly dependent upon UGR and Ad/Ar. The effective viscosity has a significant effect on KLaT, but has only a relatively weak affect on ∊GR. The KLaT correlation developed for non-Newtonian systems was extended to include the results obtained for the viscous Newtonian system studied by incorporating the effects of liquid-phase molecular diffusivity, density, and interfacial tension as determined by Nakanoh and Yoshida (1980).
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  • 280
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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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  • 281
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    AIChE Journal 35 (1989), S. 500-506 
    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 calcium hydroxide [Ca(OH)2] sorbent modified by the addition of calcium lignosulfonate has recently been developed for use in the Environmental Protection Agency's limestone injection multistage burner process. The increased reactivity with sulfur dioxide (SO2) displayed by this modified sorbent has been shown to be caused, in part, by its decreased particle (agglomerate) size compared to conventional Ca(OH)2. Subsequent work has shown that surfactant-modified Ca(OH)2 also undergoes significantly different structural changes during furnace injection. For a given reactor temperature and residence time, the modified sorbent calcines to a greater extent than unmodified sorbent. It also loses surface area more slowly, and retains more of its porosity, suggesting that it sinters more slowly than conventional sorbent. Therfore, in addition to reducing the particle size of Ca(OH)2 in some applications, calcium lignosulfonate also to inhibit one or more of the diffusion mechanisms responsible for the process of sintering.
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  • 282
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    AIChE Journal 35 (1989), S. 519-522 
    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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  • 283
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    AIChE Journal 35 (1989), S. 533-538 
    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 lumping procedure proposed previously is applied to two types of continuous reaction mixtures: one in which the constituents undergo reactions of a Langmuir-Hinshelwood (LH) type, the other in which the constituents undergo reactions of a bimolecular type. It is shown that both mixtures initially can behave qualitatively like lumped first-order reactions. At large times, the behavior of the lumps can be described by power law kinetics, with the bimolecular lump displaying a higher overall reaction order. In particular, if the feed contains a nonzero amount of unconvertible species, the LH lump at large times decays at a second-order rate, whereas the bimolecular lump decays at a third-order rate. To complement the asymptotic results, expressions describing the behavior of the lumps at any time are derived.
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  • 284
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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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  • 285
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    AIChE Journal 35 (1989), S. 676-678 
    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 Tab.
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  • 286
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    AIChE Journal 35 (1989), S. 700-700 
    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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  • 287
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    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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  • 288
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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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  • 289
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    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.
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  • 290
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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.
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  • 291
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    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.
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  • 292
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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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    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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  • 294
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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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  • 295
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 296
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    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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  • 297
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 298
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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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  • 299
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    AIChE Journal 35 (1989), S. 881-890 
    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 on-line procedure is developed that uses estimates of the dominant eigenvalues of a reactor-exchanger system to detect impending unstable operating behavior. In the event reactor stability is threatened, changes are made in the reactor's nominal operating state through a procedure that ensures the attainment of an accessment is made through estimation of closed-loop eigenvalues derived from a physically-based dynamic model. The guiding of the reactor to safe and stable conditions is carried out through a multiloop control system that receives optimal process setpoints found from an interative search. Experiments were made on a laboratory autothermal reactor system to assess the correspondence of the predicted and observed degrees of reactor stability.
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  • 300
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    AIChE Journal 35 (1989), S. 931-942 
    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 dynamic gas disengagement technique is discussed comprehensively in this paper. Also outlined is the procedure for estimating holdup structures and bubble rise velocities in a bubble column, which is extended to include the methodology for estimating the Sauter mean bubble diameter and therefore the specific gas-liquid interfacial area. The error limits for the estimated quantities are established using two extreme cases to describe the disengagement process: constant rate disengagement and interactive disengagement of bubbles. The analysis is done assuming a bimodal bubble size distribution; however, generalized equations for a multimodal bubble size distribution are also presented. Sensitivity of results to the two cases is illustrated using results obtained from experiments conducted with the air-tap water system in two bubble columns (0.05 and 0.23 m in diameter, 3 m tall). Sauter mean bubble diameters and specific interfacial areas estimated using the two approaches provide lower and upper limits for values reported in the literature.
    Additional Material: 8 Ill.
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