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• Chemical Engineering  (626)
• 2010-2014
• 1990-1994  (626)
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• 1970-1974
• 1992  (626)
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• 2010-2014
• 1990-1994  (626)
• 1985-1989
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• 1
Electronic Resource
Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 297-301
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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• 2
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 321-327
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Aqueous solutions of phenol were oxidized in a flow reactor at temperatures between 300 and 420°C (0.89 ≤ Tr ≤ 1.07) and pressures from 188 to 278 atm (0.86 ≤ Pr ≤ 1.27). These conditions included oxidations in both near-critical and supercritical water. Reactor residence times ranged from 1.2 to 111 s. The initial phenol concentrations were between 50 and 330 ppm by mass, and the initial oxygen concentrations ranged from 0 to 1,100% excess. The oxidation experiments covered essentially the entire range of phenol conversions. Analysis of the kinetics data for phenol disappearance using a combination of the integral method and the method of excess revealed that the reaction was first order in phenol and 1/2 order in oxygen, and influenced by pressure. The global reaction order for water was taken to be nonzero, and the global rate constant was assumed to be independent of pressure so that the only effect of pressure was to alter the water concentration and hence the reaction rate. This approach led to a global reaction rate law that was 0.7 order in water and had a rate constant with an activation energy of 12.4 kcal/mol. The implications of these rate laws to the design of a commercial supercritical water oxidation reactor are also explored.
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• 3
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 363-376
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 film-theory model is presented for nonisothermal gas absorption with a second-order exothermic reaction. The model accounts for the volatility of the liquid reactant and heat transfer from the liquid surface to the gas phase. The pertinent equations were solved numerically using B-spline collocation. Results from this solution show that for intermediate values of Hatta number the liquid-reactant volatility is deterimental to the enhancement of gas absorption. As Hatta number approaches zero or infinity, however, the effect of liquid-reactant volatility becomes minor. Heat losses to the gas phase drastically reduce the interfacial temperature rise, which in turn enhances or inhibits the absorption rate depending on the effective activation energy being larger or less than zero, respectively. Approximate expressions for the enhancement factor and the interfacial temperature rise were also developed. Comparisons with the “exact” numerical solution verified the accuracy of these expressions over a reasonable spectrum of parameter values. The model developed was applied to two cases representing real conditions: the chlorination of toluene and the sulfonation of dodecylbenzene. Volatility effects are shown to be important for the former system, while the relatively nonvolatile dodecylbenzene served as a counter example.
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• 4
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 397-404
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 reasonable analytical procedure of the overall reaction rate for the phase transfer catalysis with mass transfer is discussed. Alkaline hydrolysis of n-butyl acetate with a phase transfer catalyst Aliquat 336 (tricaprylmethylammonium chloride, Q+Cl-) was chosen as a model system and carried out in an agitated vessel with a flat interface. Overall reaction rates observed were proportional to the interfacial concentration of the actual reactant Q+OH- (the ion pair consisting of quaternary ammonium cation Q+ and OH-) for the hydrolysis in the organic phase. The interfacial concentration of Q+OH- was a unique function of bulk concentrations of the catalyst and NaOH, and the ionic strength of the aqueous solution. This behavior of the overall reaction rates was explained by the proposed model solution. The reaction rate constant, evaluated by fitting the rate data to the model prediction, was 47 m3/kmol·s at 298 K. It was 70 or more times greater than that of conventional alkaline hydrolysis in the aqueous phase.
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• 5
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992)
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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• 6
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 56-66
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 tortuosities of fibrous media in the heretofore unexplored transition and ordinary regimes are computed using a Monte Carlo scheme based on the Einstein equation for random walkers. The model structure is that of fully penetrable cylinders (FPC) in a unit simulation volume. The mean square displacement technique is combined with the first passage time distribution to accelerate the progress of the walkers at low Knudsen number. The results include the computation of transition regime transport coefficients for the first time. The calculated ordinary tortuosities are approximately equal to the reciprocal of the porosity over a wide range, while the transition tortuosities are shown to deviate from the reciprocal porosity with a simple dependence on Knudsen number. The limits of the transition regime are shown to correspond roughly to Knudsen numbers of 0.50 and 100, respectively. The calculated Knudsen tortuosities are shown to improve on earlier results obtained by the authors using a flux-based technique.
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• 7
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 101-115
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Singularity theory, large activation energy asymptotics, and numerical methods are used to present a comprehensive study of the steady-state multiplicity features of three classical adiabatic autothermal reactor models: tubular reactor with internal heat exchange, tubular reactor with external heat exchange, and the CSTR with external heat exchange. Specifically, we derive the exact uniqueness-multiplicity boundary, determine typical cross-sections of the bifurcation set, and classify the different types of bifurcation diagrams of conversion vs. residence time. Asymptotic (limiting) models are used to determine analytical expressions for the uniqueness boundary and the ignition and extinction points. The analytical results are used to present simple, explicit and accurate expressions defining the boundary of the region of autothermal operation in the physical parameter space.
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• 8
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 193-200
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 new control scheme is presented for feedforward control of unknown disturbances in the model-predictive control (MPC) scheme. In this control scheme, a neural network is connected in parallel with the MPC controller and trained online by minimizing the MPC controller output corresponding to the unmodeled effect. It is applied to distillation column control and nonlinear reactor control to illustrate its effectiveness. The result shows that the neural feedforward controller can cope well with strong interactions, time delays, nonlinearities, and process/model mismatch. The controller also offers such advantages as fault tolerance, generalization capability by interpolation, and learning capability by randdom input patterns.
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• 9
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 502-510
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 new technique for studying and recovering short-lived chemical intermediate species has been developed using a Couette reactor, which is an open one-dimensional reaction-diffusion system. Reaction occurs in the annulus between concentric cylinders with the inner one rotating and the outer one at rest. Fresh reagents are in contact with the ends of the annulus, but there is no net axial flow. The axial transport arising from the hydrodynamic motion is effectively diffusive, but has a diffusion coefficient 3 to 5 orders of magnitude larger than that of molecular diffusion. The oxidant (ClO2-) and reductant (I-) of an autocatalytic reaction are fed at opposite ends of the reactor. The reactants diffuse toward each other and react, forming a steady, sharp chemical front and a stable spatial concentration band of unstable intermediate species (HOCl) in the front region. Unstable intermediate species are thus stabilized at a well-defined spatial position where they can be recovered and studied. The experiments and numerical simulations demonstrate that the faster the reaction rate, the stabler the chemical front and the more effective the recovery of unstable intermediate species.
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• 10
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 555-562
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: To cope with modeling uncertainties and randomness of external disturbances, a new tracking control called the natural control concept is designed. Its implementation is completely independent of the internal dynamics of a controlled system, its desired output and external disturbances. The design algorithm established ensures a prespecified exponential quality of output tracking. The theory presented in this article is applied effectively to the design of natural tracking control for a chemical reaction process described by the fourth-order, linear, state-space mathematical model.
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• 11
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 219-226
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Current AC (alternating current) techniques are used often to characterize the energetics at a semiconducting solid phase/electrolyte interface. For thin layers having a strongly disordered or amorphous structure (such as oxide-passive layers anodically grown on valve metals), interpretative models currently used for crystalline semiconductors may produce misleading data.A new interpretation of the admittance data, based on recent models for amorphous semiconductors (a-Sc) Schottky barriers, is presented for passive films of Nb, W and Ti. The physical bases of the model are presented as well as its advantages and disadvantages. The new theory views the solid/electrolyte interface more satisfactorily and provides information on the solid-state properties and the electronic structure of the electrode useful for interpreting the electron exchange between the solid phase and redox couples in solution.
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• 12
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 227-236
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 reliable information on operating plants it is essential to design measuring points well by selecting directly measured quantities from the set of all measurable quantities.This article deals with a new method for optimizing measurement design. It is based on multiple Gauss-Jordan elimination of the system of linear mathematical model equations and solves the problem of instrumentation design in new plants as well as the problem of optimizing existing measuring systems. Optimization methods for linear objective functions and for objective functions of general type are proposed. The method also offers a complex classification of quantities (observability and redundancy). After the optimization, the problem is presolved and is ready for an optimal processing of measured data. The mathematical model is reduced to the minimum set of equations and quantities relevant to the solution of a given problem. From a numerical standpoint, the solution is efficient.
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• 13
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 244-250
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 reaction between COS and aqueous solutions of primary and secondary amines has been studied by means of the stirred cell technique. Kinetic experiments at temperatures 283 to 333 K were carried out with MEA, DGA, DEA, DIPA, MMEA, AMP, and MOR. All kinetic experiments could be described by a zwitterion reaction mechanism similar to the mechanism proposed by Caplow (1968) for the reaction between CO2 and secondary amines: \documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{l} COS + R_2 NH \leftrightarrow R_2 NH^ + COS^ - \\ R_2 NH^ + COS^ - + B \leftrightarrow R_2 NCOS^ - + BH^ + \\ \end{array}$$\end{document}Analysis of concentrated amine solutions at high COS concentrations by various analytical techniques confirmed the conclusions from the kinetic experiments. For all amines except for MEA, the overall reaction rate was found to be determined entirely by the zwitterion deprotonation rate.
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• 14
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 273-283
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 system studied in this work is a dilute solution of rod-like molecules under simple shear flow and near a hard wall. The time evolution of the probability density function is described by a diffusion equation; particle trajectories that correspond to this equation are generated by stochastic methods. Several algorithms are presented to handle the constraints imposed by the presence of the wall. In good agreement with recent experimental work on xanthan solutions, for high shear rates we observe an increase in the thickness of the depletion layer near the wall. For low to intermediate shear rates, however, we find a transient decrease of the depletion layer thickness that has not been observed experimentally. Based on the results of our simulations, we present a simple procedure to determine a few, well defined characteristic parameters from the experimental density profiles.
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• 15
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 302-307
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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• 16
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 311-314
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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• 17
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 316-316
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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• 18
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992)
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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• 19
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 328-342
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 experimental study of a semibatch reaction crystallization is presented. Dilute hydrochloric acid is fed to a stirred solution of sodium benzoate to crystallize benzoic acid. The weight mean size of the product crystals increases with increasing stirring rate, reaches a maximum, and then decreases again. Larger crystals may be produced if the reactant feed point is positioned close to the outlet stream of the impeller. At equal power input the influence of stirrer type is negligible. Decreasing reactant concentrations or feed rate increases the crystal size significantly. Experimental results are explained qualitatively focusing on nucleation and growth conditions and on feed point mixing. The feed point micromixing brings reactants together to generate supersaturation and allow for nucleation. Continued mixing, however, may partially dilute supersaturation before nucleation takes place or may restrict nuclei growth, thus promoting more efficient Ostwald ripening in the bulk. This may result in high bulk supersaturations which in turn hampers the dilution effects.
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• 20
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 377-384
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Experimental responses from crystallization of copper sulfate pentahydrate, nickel ammonium sulfate, and soy protein in continuous MSMPR crystallizers were used to determine simultaneously crystal growth and nucleation rates and agglomeration kernels. Measured product crystal size distributions at steady state for all these systems were transformed into crystal volume coordinates to use two methods: moments analysis and optimization procedure for parameter characterization. An iterative nonlinear parameter estimation by optimization procedure was used to deduce the kinetic rate parameters in the solution of the agglomeration model in crystal volume coordinates, extended from the analysis by Liao and Hulburt (1976), from the translated data set for the product crystals. The kinetic results obtained for the copper sulfate pentahydrate system were correlated in terms of power law kinetic expressions depicting the effect of significant observable variables.
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• 21
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 385-396
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 oxidation of CO by O2 and N2O over an oxidized 10 wt. % Cu-Cr/Al2O3 catalyst (Cu:Cr=1:1) has been studied by temperature-programmed reactivity measurements (400-550 K) over a wide range of partial reactant pressures, including inhibition by CO2. The CO oxidation rate is zeroth-order in oxygen and has orders between 0-1 in CO and N2O, depending on the gas-phase composition. Mechanistic information from literature combined with the kinetic data resulted in the selection of an Eley-Rideal-type of kinetic model without a priori assumptions on rate-determining processes. The model consists of the oxidation of reduced sites by O2 and/or N2O, followed by a reaction with CO, yielding a surface intermediate that releases CO2 in a consecutive step. CO2 inhibits both by reversible adsorption on oxidized and reduces sites, the latter under formation of the surface reaction intermediate. Apart from the surface oxidation by O2, the reaction rates of all assumed elementary processes are of the same order of magnitude and, therefore, determine the overall rate. The surface oxidation by oxygen is about four orders of magnitude larger, which explains the zeroth-order in oxygen and the observation that oxygen first reacts with CO before N2O is able to oxidize CO. The obtained activation energies of the elementary processes agree with values in the literature for corresponding systems.
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• 22
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 438-444
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 developed predicts a priori potential errors associated with the energy trace recorded by an isoperibol differential power scanning calorimeter in the measurement of heat of adsorption of H2 on Pt and Pd catalysts. The uptake of H2 by the catalyst sample was approximated by a diffusion-limited quasi-steady-state moving boundary model. This approximation is valid only if the parameter [(adsorption capacity of cat. sample)/(inlet conc. of H2)] is extremely large (∼ 24). The effect of flow rate, amount of H2 adsorbed, sink temperature, and the thermal conductivity of the adsorbate mixture was examined. Model predictions indicate that the error in the energy trace recorded by the DSC is appreciable: if a large difference exists between the thermal conductivity of the inert carrier, Ar (K = 0.017 J/m·K·s), and the adsorbate, H2 (k = 0.174 J/m·K·s); if the heat sink temperature is much lower (∼ 90 K) than the measurement temperature. However, these errors can be eliminated by matching the thermal conductivity of the inert carrier and adsorbate, such as He (k = 0.143 J/m·K·s) and H2 (k = 0.174 J/m·K·s). The results agree well with the experimental observations of Vannice et al. (1987) on high-purity Pt and Pd powder and supported Pt catalysts, if the H2 uptake by the catalyst sample in the calorimeter is small (≤2 μmol).
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• 23
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 461-465
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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• 24
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 473-476
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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• 25
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 480-480
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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• 26
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 489-501
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 coupled, unsteady Navier-Stokes, convective diffusion, and thermal energy equations that describe spin coating of colloidal suspensions are solved numerically. The theoretical model, absent of any adjustable parameters, is used to explore the effects of angular velocity, initial solvent weight fraction, solvent properties and spin coating protocol on the evolution of temperature and concentration profiles in the liquid film during spin coating. The predicted coated film thickness is found to be in excellent quantitative agreement with spin coating experiments performed with both hard-sphere and nonhard-sphere suspensions of monodisperse latex particles in water. The coated film thickness, determined by ellipsometry, is shown to depend on the inverse square root of the angular velocity except at high ionic strength when the dependence on angular velocity is weaker. Timescales that characterize spin coating of colloidal suspensions are shown to be quite different from those that characterize spin coating of polymer solutions, and consequently simple models for predicting the coated film thickness of polymer solutions (Bornside et al., 1991; Lawrence, 1989) are shown to be inadequate for colloidal suspensions. Rapid substrate acceleration, high rotation rates, partial saturation of the overlying gas phase, and high initial solids concentration are identified as spin coating protocols that suppress a convective instability that produces radial striations in the coated film.
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• 27
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 521-534
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Disturbance rejection capabilities of different controller structures, for example, diagonal, block diagonal or full multivariable controller, are discussed. A generalized version of Relative Disturbance Gain, Generalized Relative Disturbance Gain (GRDG), is defined to evaluate the disturbance rejection capabilities of all possible controller structures. Furthermore, the relative disturbance gain array (RDGA) is introduced. Basic properties of RDGA are derived. An important one is: GRDG of all possible controller structures can be calculated directly from the array. Therefore, with RDGA, the synthesis of the controller structure can be done in a straightforward manner. Physical implications and quantitative analyses of GRDG are given. These form the basis for the synthesis. Finally, frequency-dependent GRDG is developed which evaluates the performance further based on dynamic information. Several examples are used to illustrate the synthesis of the controller structure. The results show that better disturbance rejection can be achieved by selecting appropriate controller structure.
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• 28
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 544-554
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 carried out in bubble columns for a number of liquids at pressures between 0.1 and 2.0 MPa for two column sizes. Based on the experimental results as well as extensive literature data, the extent of the effect column dimensions have on gas holdup were determined, both at low and high pressures (which is of importance to scale-up). It was also demonstrated that none of the published empirical gas holdup equations incorporate the influence of gas density accurately. Therefore, a new improved gas hold-up equation is developed that incorporates the influence of gas and liquid properties with an average error of approximately 10%. Finally, it is also discussed to what extent theinfluence of pressure on other important design parameters such as the interfacial area, the liquid volumetric mass transfer coefficient, and gas and liquid mixing, can be estimated on the basis of empirical equations.
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• 29
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 573-591
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: A theory is developed to predict the solubility of protein mixtures in solutions containing nonionic polymer. Effective protein-protein interactions due to polymer are taken to be volume-exclusion potentials derived using statistical mechanics. Statistical-mechanical perturbation theory is used to calculate chemical potentials. The effects of protein size, mole fraction and polymer concentration on solubility are explored. The theory is extended to include electrostatic interactions. The excess chemical potential of the proteins due to the charges on all species is calculated using the mean spherical approximation for a mixture of charged hard spheres. The theory predicts: the larger protein is preferentially precipitated over the smaller one; the more concentrated protein is more likely to precipitate; and increasing the charge of a particular protein reduces its ability to precipitate.
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• 30
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 611-614
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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• 31
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 615-618
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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• 32
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 626-628
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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• 33
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992)
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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• 34
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 660-670
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 of water vapor on silica gel, at influent humidities from 6 to 80% at 25 and 50°C, yielded breakthrough curves of unusual shapes. Breakthrough patterns varied from the expected sigmoidal shape at low humidity to a curve resembling the tangent function, but symmetric about the stoichiometric breakthrough time. Unusual shapes were found to be due to subtle combination of Type-IV isotherm behavior and heat effects. A mathematical model was developed to simulate the performance. The results show that complex breakthrough behavior need not be ascribed to complicated causes (such as diffusion in bidisperse pores), which require multiparameter fitting of experimental data. In fact, the effects may be predicted from properties measured in simple independent experiments, though some care is required to account for the effects accurately.
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• 35
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 703-715
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Influence of the tube and particle diameter and shape, as well as their ratio, on the radial heat transport in packed beds has been studied. Heat transport experiments were performed with four different packings in three wall-cooled tubes, which differed in inner diameter only. Experimental values for the effective radial heat conductivity and wall heat-transfer coefficient for the pseudo-homogeneous two-dimensional model and the overall heat-transfer coefficient for the one-dimensional model are presented. Values were obtained for glass spheres, alumina cylinders, and alumina Raschig rings. The effective radial heat conductivity and wall heat-transfer coefficient can both be correlated as a linear function of the gas flow rate. The Bodenstein number for heat at fully developed turbulent flow is influenced strongly by the shape of the packing: 10.9 for glass spheres, 7.6 for alumina cylinders, and 4.2 for alumina Raschig rings. For the same packing, no significant influence is found of the tube diameter on the effective radial heat conductivity or on the wall heat-transfer coefficient. The overall heat-transfer coefficient can be described very well by the so-called “lump equation,” which gives the relations among the overall heat-transfer coefficient, effective radial heat conductivity, and wall heat-transfer coefficient. The “lump factor,” as used in the lump equation, has a best-fit experimental value of 7.4.
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• 36
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 733-741
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Local instantaneous changes in heat-transfer coefficients due to the passage of gas bubbles in liquid and liquid-solid systems are measured. A special heat-transfer probe is developed and located within the bed to trace the instantaneous local heat-transfer rate during the passage of single gas bubbles. A microfoil heat flow sensor is attached to a foil heater, and the sensor-heater probe assembly can accurately measure the heat flux and the surface temperature over a small area. Signals from the sensor are amplified and interfaced with the microcomputer data acquisition system. Simultaneous visualization is performed using a high-speed video camera and a borescope to establish the correspondence between the visual and sensor signals, and hence relate the local instantaneous hydrodynamics to the heat-transfer rate. Local heat-transfer coefficient vs. time traces are analyzed in conjunction with visual signals. The heat-transfer coefficient exhibits a sharp peak in the bubble wake. In both liquid and liquid-solid systems, the observed local maximum in heat-transfer coefficient behind a rising bubble is due to the bubble-wake-induced surface renewal. Enhancement in heat transfer due to the bubble increases with the size because of increased surface renewal caused by larger bubble wake and stronger vortices. The local maximum in heat transfer, however, is more pronounced in liquid than in liquid-solid systems.
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• 37
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 761-770
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 extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous-flow extraction apparatus. Decaffeination rates were determined as a function of CO2 flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with a flame ionization detector. Soaking the raw beans in water prior to decaffeination enhanced the rate of extraction, which increased markedly with water content. Using CO2 saturated with water also increased the rate of extraction. The rate of decaffeination increased with pressure and temperature and was influenced by both intraparticle diffusion in the water-soaked beans and external mass transfer. A mathematical model based on a linear-driving-force approximation of mass transfer and partitioning of caffeine between the water and the supercritical CO2 describes the time-dependent process. The partition coefficient for caffeine distributed between water and supercritical CO2, the only parameter determined from the dynamic extraction rate data, increases with temperature and pressure.
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• 38
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 771-780
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Following hydrogenolysis of n-hexane on an alumina-supported platinum catalyst, the surface of the metal is covered partially with carbonaceous residues or coke. The fraction of surface platinum not covered with coke has been found to be about one half by four independent techniques: titration of preadsorbed oxygen by dihydrogen, chemisorption of carbon monoxide, infrared spectroscopy of chemisorbed carbon monoxide, and hydrogenation rate of ethylene. The first of these techniques suggests itself as the simplest one for further studies of deactivation by coking of platinum catalysts.
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• 39
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 797-797
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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• 40
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1003-1012
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 in-situ catalytic hydrodechlorination of chlorinated hydrocarbons in waste-water-generating HCl and a hydrocarbon-free chlorine is demonstrated as a viable wastewater remediation technique. Catalyst screening studies with a shaker-type hydrogenation reactor have shown that the commercial Pd/C catalyst is highly effective in hydrochlorinating various chlorinated hydrocarbons in synthetic wastewater at room temperature and near atmospheric pressure. 1, 1, 2-trichloroethane hydrodechlorination experiments in an autoclave reactor shows that initial rates are well correlated with first-order dependence of the reactant hydrocarbon adsorbed on carbon. Initial rates are also independent of hydrogen pressure, and adsorption on the carbon support is Langmuir type. Activation energies calculated at different catalyst loadings varied from 29 to 38 MJ/mol.1,1,2-trichloroethane hydrodechlorination activity is much lower for Pd/Al2O3 than Pd/C because the reactant hydrocarbon does not adsorb on alumina. When the carbon support does not readily adsorb the reactant hydrocarbon, the hydrodechlorination rates dropped significantly. These results confirm the role of the carbon support in providing the major path to reaction and thereby significantly increasing reaction rates compared to direct adsorption from solution onto the palladium.
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• 41
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1045-1048
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 first phase equilibrium data are presented for Structure H hydrates. The data represent the initial formation of these hydrates from methane, with adamantane -  a previously determined Structure H former. Temperature and pressure conditions are consistent with hydrocarbon production/transportation/processing facilities. Structure H hydrates are shown to contain molecules indigenous to petroleum. which may not be present in natural gas.
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• 42
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1105-1114
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 azo coupling of 1-naphthol with diazotized sulfanilic acid has been studied in detail focusing on the practical use of this reaction as a micromixing test reaction, as developed by Bourne and coworkers. The reaction is a fast, competitive, consecutive reaction whose final product distribution is affected greatly by mixing. Problems that occur in the isolation of the pure-dye products and quantification of the product distribution are addressed. Previously unreported information is given about the structure and properties of one of the products as well as the existence of an additional unknown product. The reaction was used to characterize the spatial heterogeneity of micromixing in a 14-L stirred-tank fermenter. Results show large differences in the product distribution dependent on the depth and radial position of the feed pipe in the tank.
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• 43
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1129-1134
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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• 44
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1135-1138
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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• 45
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992)
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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• 46
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1206-1212
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Inclining a fluidized bed column by as little as 1.5 degrees greatly affects the bed characteristics. The bed contracts, the particle-liquid mass-transfer and heat-transfer coefficients increase by up to 30%, and the gas-liquid mass-transfer coefficient can either be increased by up to 15% or decreased by up to 20%.
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• 47
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1229-1242
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 and algorithm are presented for the separation of mixtures where the phase distribution on the trays is extremely uncertain, as it occurs when the mixtures have two partially-miscible binary pairs and a minimum-boiling ternary azeotrope. Included are an algorithm for the consistent initialization of index-I differential/algebric equations, a novel algorithm for branch switching when the phase distribution changes at a real bifurcation point, and a reliable algorithm for phase stability analysis. Open-loop responses are presented for the dehydration of secbutanol with disecbutylether in single-stage, 12-tray, and 33-tray separators. These simulation results for the 33-tray tower are in qualitative agreement with experimental measurements for the ARCO SBA-II tower.
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• 48
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1254-1278
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 modular multivariable controller (MMC) represents a multivariable controller design methodology which is based on the solution of multiobjective optimization problems using the strategy of lexicographic goal programming; priority-driven, sequential satisfaction of objectives. This article formally introduces the concept of the MMC, analyzes its static characterstics, and proposes a specific methodology for the design of steady-state MMCs. It is shown that the framework of MMC can explicitly handle all types of control objectives (for example, equality or inequality specifications on controlled outputs), and constraints on manipulations. Its priority-driven, sequential satisfaction of control objectives leads to a modular, hierarchical structure of controllers with specific objectives. The modular character of MMC allows the explicit maintenance, tuning, and reconfiguration of multivariable control systems, while its hierarchical structure explicitly expresses engineering decisions and trade-offs. Its static design incorporates uncertainty in process gains and automatic reconfiguration to account for failure in sensors and/or actuators. The design of an MMC for a heavy oil fractionator is presented to illustrate the controller's character and the proposed methodology for the design of static MMCs.
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• 49
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1299-1301
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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• 50
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1303-1303
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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• 51
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1305-1305
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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• 52
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1309-1328
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: We examine the simplest homogeneous azeotropic distillation sequence of industrial relevance, where an entrainer is added to a binary azeotrope to recover both azeotropic constituents as pure products. Despite its apparent simplicity, such distillation columns can exhibit an unusual behavior not observed in zeotropic distillation: For some mixtures, separation as a function of reflux goes through a maximum. At infinite reflux, no separation is achieved.In some cases, achieving the same specifications with a larger number of trays requires a larger reflux.Sometimes the only feasible separation yields the intermediate component as a pure distillate, while the bottom product contains the light and heavy components.Sometimes the only feasible separation yields the intermediate component as a pure bottom product while the distillate contains the light and heavy components.While these unusual features can be regarded as curiosities, they are essential for proper entrainer selection and design. For a minimum boiling azeotrope, the existing and conflicting entrainer selection rules state that one should use a component that introduces no distillation boundary between the azeotropic constituents (Doherty and Caldarola, 1985), and either a low or high boiling component that introduces no additional azeotrope or a component which introduces new minimum boiling azeotropes (Stichlmair et al., 1989). By taking advantage of the curious aforementioned features, as well as our experience involving more than 400 mixtures, we have been able to analyze the assumptions behind these criteria, show when those assumptions break down, and therefore understand the limitations of the criteria.
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• 53
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1329-1339
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Of special industrial interest is the cross-directional control of coating processes, where the cross direction refers to the direction perpendicular to the substrate movement. The objective of the controller is to maintain a uniform coating under unmeasured process disturbances. Assumptions that are relevant to coating processes found in industry are used to develop a model for control design. This model is used to derive a model predictive controller to maintain flat profiles of coating across the substrate by varying the liquid flows along the cross direction. Actuator constraints, measurement noise, model uncertainty, and the plant condition number are investigated to determine which of these limit the achievable closed-loop performance. From knowledge of how these limitations affect the performance we can make some recommendations on how to modify the plant design to improve the coating uniformity. The theory developed throughout the article is rigorously verified through experiments on a pilot plant. The controller rejects disturbances with two sampling times. The proposed controller can reduce the variance in coating thickness by as much as 80% compared to what is possible by manual control or simple control schemes.
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• 54
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1369-1378
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 knowledge based system is described that is designed to generate on-line advice for operators regarding the proper distribution of hydrogen resources in a refinery. The system uses a coupled architecture incorporating numerical computing in a knowledge based system environment. This arrangement allows for powerful and flexible problem solving. One portion of the coupled system formulates an optimization problem that is subsequently solved by an external routine. This application is particularly concerned with uncertainty that is present in some of the constraints. To deal with this uncertainty, a fuzzy approach to the optimization is taken. A method is presented that solves the fuzzy optimization problem using standard mathematical programming techniques. The results of the fuzzy optimization allow the crisp solution to be expanded into a neighborhood of solutions that is considered acceptable. Although this work examines a specific problem, the concepts presented are general.
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• 55
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1357-1368
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 adsorption isotherms of O2, N2, CH4, CO2, SO2, and NO on five pillared clays (Zr, Al, Cr, Fe, and Ti-PILCs) are measured. The equilibrium selectivity of CH4/N2 on Al-PILC is greater than 5.0, which exceeds all known sorbents by a large margin. In addition, high SO2/CO2 equilibrium selectivities are observed on these pillared clays. The sorption characteristics of these pillared clays (PILCs) exhibit characteristic trends that are better understood with the aid of the potential energy profiles. A new semi-empirical approach is presented for the calculations of the potential energy profiles of PILCs. This approach requires the adsorption isotherms and an isotherm equation that accounts for the structural heterogeneity of the adsorbents. A comparison of the energy profiles obtained using the semi-empirical approach with the corresponding results obtained via the Kirkwood-Muller formalism, where only dispersion forces are taken into account, provides a measure of the importance of the electrostatic forces in the sorption characteristics of these PILCs. Sizable differences are observed for the potential energy profiles, indicating that the electrostatic forces are not negligible, and can significantly enhance the adsorption potential, resulting in large increases in the amounts adsorbed on these PILCs.
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• 56
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1703-1715
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: One of the limitations of today's knowledge-based (KB) systems for diagnostics and supervision is a lack of adequate temporal reasoning mechanisms. Most of these systems are designed primarily to operate with the current values of the process variables and, sometimes, with their derivatives. Such simple capabilities, however, are not always sufficient to identify some complex dynamic phenomena, which in many cases leave their own unique “stamp” on the process behavior, expressed in the form of characteristic temporal shapes of the related variables. To detect and diagnose adequately the events of interest, the KB system should be able to reason about the temporal shapes of the process variables. Although during manual supervision process operators rely heavily on such characteristic shapes as reliable symptoms of underlying phenomena, their exploitation has not been considered seriously by the designers of KB control systems. We propose a generic methodology for qualitative analysis of the temporal shapes of continuous process variables designed to be embedded into a real-time KB environment. It is applicable to bioprocesses, as well as to other complex dynamic systems.
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• 57
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1751-1760
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 experimental validation of on-line estimation of multiple specific growth rates for the bakers' yeast fed-batch process is presented. Pole placement based parameter estimation combined with an asymptotic biomass observer constitute the basic algorithm. The full process model being ill-conditioned for estimation using the available measured state variables, the use of two partial models related to two different states of the process is suggested. An alternating procedure between two sets of estimation algorithms designed from the partial models is proposed. The performance of the alternating procedure is validated both with simulated and experimental data. The accuracy of the estimates of the three specific growth rates involved in this process is verified according to two criteria based on the respiratory quotient and on the evaluation of the ethanol production/consumption rate.
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• 58
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1761-1768
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Binary diffusion coefficients of some organic compounds in carbon dioxide at 313.2 K and 16.0/25.0 MPa were measured by using the Taylor-Aris tracer response technique. We propose a new correlation of Schmidt numbers as a function of solvent molar volumes for predicting binary diffusion coefficients in dence CO2 and self-diffusion coefficients of dense CO2. The correlation was also found to be valid for predicting self-diffusion coefficients of dense CH4 at Fv/A* 〈 40 or v2/(ṽ2)0 〉 1.62.
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• 59
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1801-1815
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 hydrodynamics of gas-solid flow, usually referred to as circulating fluidizedbed flow, was studied in a 7.5-cm clear acrylic riser with 75-μm FCC catalyst particles. Data were obtained for three central sections as a function of gas and solids flow rates. Fluxes were measured by means of an extraction probe. Particle concentrations were measured with an X-ray densitometer. In agreement with previous investigators, these data showed the flow to be in the core-annular regime, with a dilute rising core and a dense descending annular region. However, unlike the previous studies conducted worldwide, the data obtained in this investigation allowed us to determine the viscosity of the suspension. The viscosity was a linear function of the volume fraction of solids. It extrapolates to the high bubbling-bed viscosities.
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• 60
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1493-1498
ISSN: 0001-1541
Keywords: Chemistry ; Chemical Engineering
Source: Wiley InterScience Backfile Collection 1832-2000
Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
Notes: Racemic leucine can be separated into d- and l-isomers by fractional extraction across microporous hollow fibers. In this extraction, an aqueous solution of the racemate is fed to the lumen of the fibers, and an octanol solution of dodecyl-l-hydroxyproline flows countercurrently outside of the fibers. The interface between feed and extractant is stabilized by filling the pores in the hollow-fiber walls with a cross-linked polyvinylalcohol gel which offers negligible resistance to mass transfer. The extraction with dodecyl-l-hydroxyproline deliberately imitates earlier studies, facilitating comparisons of hollow-fiber extraction with other techniques. The results show that the isomer yield per equipment volume of racemic separation is 100 times greater than that in a continuously rotating extractor, and 1,000 times greater than that in a conventional packed tower.
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• 61
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1523-1535
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 rigorous calculation of top and bottom fractions of a multicomponent distillation is very time consuming and involved as it can only be done iteratively, and convergence problems are often encountered, especially in azeotropic systems. This article presents a method for the easy determination of possible top and bottom fractions of a ternary distillation. This method, which works for zeotropic as well as for azeotropic mixtures, is especially useful in the first steps of process synthesis and design since impossible separations can be determined and thus excluded from further analysis so that work can be concentrated on feasible processes. A very important application of the method developed in this article is to the design and analysis of processes for complete separation of binary azeotropic mixtures by use of an entrainer (for example, Azeotropic Distillation and Extractive Distillation). Knowledge of the separation regions in the distillation diagram allows for the development of a generalized process and the formulation of criteria for entrainer selection. The effectiveness of the method is demonstrated on a number of industrial important processes.
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• 62
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1481-1484
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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• 63
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992)
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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• 64
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1916-1922
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 bed expansion characteristics of two-phase inverse fluidization were studied. Twelve different spheres with diameters from 1.31 to 7.24 mm and densities between 75 and 930 kg/m3 were fluidized with water. The experimental lne-lnU curves were parallel to those predicted by the model of Richardson and Zaki and therefore the exponents n were similar. However, Ui, the liquid velocity at ε = 1 differed from that predicted from the standard drag curve for Ret 〉 130. This can be explained by the fact that the drag curve of a freely rising light sphere differs from that of a falling particle. The values of Ui calculated using this modified drag curve were in good agreement with the experimental results. The difference between experimental and calculated from the Ergun equation minimal fluidization velocities is explained by the difference in mechanical inertia of the light and heavy particles.
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• 65
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1979-1989
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 statistical model adsorption isotherm developed by Ruthven and coworkers and used in the prediction and correlation of adsorption in microporous materials especially zeolites is critically examined from the perspective of statistical mechanics. This is done by applying the method to a class of molecular models for which the statistical thermodynamics may be solved analytically without approximation. The models considered are finite length single component and binary one-dimensional systems in which the molecules interact via square well potentials. These are among the simplest realistic yet analytically solvable molecular models of adsorption in porous materials. Our analysis clarifies the theoretical status of the Ruthven approach as well as revealing some of the weaknesses in it.
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• 66
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Hoboken, NJ : Wiley-Blackwell
AIChE Journal 38 (1992), S. 1969-1978
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 study of nonlinear competitive equilibrium is of fundamental importance in understanding the behavior of proteins in preparative ion-exchange chromatographic separations. In this work we present a steric mass-action (SMA) ion-exchange equilibrium formalism, which explicitly accounts for the steric hindrance of salt counterions upon protein binding in multicomponent equilibria. An analytical solution has been derived for the calculation of isotachic effluent profiles of displaced proteins and induced salt gradients under ideal chromatographic conditions. A stability analysis has been employed to establish the order of the feed components in the displacement train. Theoretical predictions are compared to experimental results for the separation of proteins by cation-exchange displacement chromatography. These results demonstrate the efficacy of the SMA formalism in predicting complex behavior present in ion-exchange displacement systems. Furthermore, the analytical solution of ideal isotachic displacement profiles with the SMA formalism enables rapid methods development and optimization of ion-exchange displacement separations.
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