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  • 1990-1994  (915)
  • 1992  (915)
  • Chemical Engineering  (688)
  • Physical Chemistry  (227)
  • 101
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1835-1839 
    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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  • 102
    Electronic Resource
    Electronic Resource
    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
    Type of Medium: Electronic Resource
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  • 103
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1843-1846 
    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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  • 104
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 251-258 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Research has been carried out on the use of NCS (Network Computing System) to distribute the processing of a finite element application to multiple computers at once. Coarse-grained parallelism of specific routines on loosely coupled CPUs has been implemented and tested. In a step-by-step fashion, the method of using NCS to convert finite element software POLY2D is explained for its application in parallel computing resources throughout a network. For the modeling of a simple conductive heat transfer problem, the distributed version of POLY2D on a homogeneous token ring network of nine Apollo workstations is used. Some timings given are compared to those obtained from a standard nondistributed simulation.
    Additional Material: 13 Ill.
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  • 105
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 284-290 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Resistively heated filaments are used to deposit diamond or to act as a substrate in the manufacture of ceramic fibers. This article analyzes the effects of an AC power source, in particular the oscillation in filament temperature and its influence on the kinetic rates, as well as the vibration of the filament, when it is mounted in a state of tensile stress. These effects diminish when the filament gauge is large enough and the analysis can help to decide whether an AC or a DC power source should be used.
    Additional Material: 7 Ill.
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  • 106
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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
    Additional Material: 3 Ill.
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  • 107
    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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  • 108
    Electronic Resource
    Electronic Resource
    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.
    Additional Material: 17 Ill.
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  • 109
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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.
    Additional Material: 8 Ill.
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  • 110
    Electronic Resource
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 425-437 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of mixing on number- and weight-average degree of polymerization in free radical homopolymerization in solution in a semibatch stirred tank-reactor have been modeled by use of the “partially segregated feed” model of Villermaux (1989) and the lumped kinetic treatment of addition polymerization. Mixing conditions are described in terms of the dimensionless time constants θM and θX for convective and diffusive mixing, respectively. Results show that DPn is relatively insensitive, while DPw is highly sensitive to mixing conditions. Comparison with ideal mixing results shows that polydispersity (DPw/DPn) can rise greatly as mixing becomes increasingly nonideal, depending on the value of dimensionless flow rate and dimensionless initiator rate constant. Time constants of the mixing model need to be expressed as dimensional correlations before the proposed polymerization model can be compared to experimental measurements. The model may be adapted to melt polymerization in nonideal CSTR such as LDPE.
    Additional Material: 8 Ill.
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  • 111
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 607-610 
    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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  • 112
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 793-796 
    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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  • 113
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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
    Type of Medium: Electronic Resource
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  • 114
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 511-520 
    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 alkanolamines are commonly used to strip acid gases (CO2 H2S) from hydrocarbon streams. Processes for stripping acid gases from gaseous streams are well understood; however, the application to liquids is not as advanced. Experimental data available are scarce for systems containing aqueous amine solutions and the constituents of liquefied petroleum gases. To this end, new data are presented for the equilibria in the system propane-water-methyldiethanolamine (MDEA). A knowledge of the phase behavior in this system is required to model the equilibria encountered in the more complex systems of industrial importance.This work is a comprehensive study of the phase equilibria in the system propane-3 M MDEA, including vapor-liquid, liquid-liquid, and vapor-liquid-liquid equilibria. Experimental measurements were made for temperatures between 0 and 150°C and pressures up to 20 MPa. The data were correlated using the Stryjek-Vera modification of the Peng-Robinson equation of state. In addition, a composition-dependent mixing rule was required to fit the data adequately.
    Additional Material: 12 Ill.
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  • 115
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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.
    Additional Material: 13 Ill.
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  • 116
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 592-602 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The nonequilibrium tray model proposed by Young and Stewart (1990) is used to correlate published fractionation data from sieve tray columns 0.45 m to 1.2 m in diameter. The model contains a dimensionless coefficient a00 to describe the interphase heat and mass transfer, and a Peclet number Pe to describe the lateral mixing of the liquid on the tray. The coefficient a00 is investigated as a function of tray geometry and hydrodynamic variables, using an error-in-variables extension of a multiresponse parameter estimation algorithm. Data from several sources are well correlated by a simple dimensionless relation for a00, with Pe predicted from the results of Bennett and associates (1983, 1991).
    Additional Material: 7 Ill.
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  • 117
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 629-634 
    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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  • 118
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 651-659 
    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 this paper, a program of analysis is carried out for control of a nonlinear stirred tank reactor. By examining the uniqueness and stability properties of the reactor, the zero dynamics are analyzed. Subsequently, a model reference adaptive controller (MRAC) which explicitly takes into account the nonlinearities of the system is designed; the MRAC successfully compensates for parametric uncertainty. It is shown that even when almost all reactor parameters are unknown, global convergence over the entire phase space is achieved.
    Additional Material: 3 Ill.
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  • 119
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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.
    Additional Material: 9 Ill.
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  • 120
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 716-722 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of particle size distribution (PSD) on the performance of a fluidized bed reactor was investigated in different hydrodynamic regimes: bubbling, slugging, turbulent and fast fluidization, with three particle size distributions, all with the same mean diameter and nearly the same particle density and BET surface area. Regime transitions were examined by measuring pressure fluctuations. Void sizes tended to be smaller and the transition from bubbling or slugging to turbulent fluidization was achieved earlier for the wide distribution powder than for the narrow PSD. At gas velocities ≤ 0.2 m/s, the conversion and reactor efficiency were not affected greatly by the PSD. However, at higher gas velocities, PSD played a significant role. For particles of wide size distribution, the conversion in the turbulent and fast fluidization regimes was usually higher than in the bubbling fluidization regime at the same dimensionless rate constant, kf′. On the other hand, for particles of narrow size distribution, the dependence of conversion on the regime is small, except for the fast fluidization regime.
    Additional Material: 9 Ill.
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  • 121
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 723-732 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pressure relief venting of a runway reaction with gas generation is examined in terms of the overall system response and the associated venting requirement. This article presents an exact formulation as well as an approximate analytical approach. The latter is shown to be particularly useful in vent-sizing applications. Using an aqueous hydrogen peroxide decomposition example, the analytical results are demonstrated to agree well with the exact numerical results over a wide range of overpressure. In addition, the analytical result is shown to reduce to the correct limit for a pure vapor system and offers a useful vent-sizing equation for a pure-gassy system.
    Additional Material: 9 Ill.
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  • 122
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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.
    Additional Material: 11 Ill.
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  • 123
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 811-820 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A framework is developed to describe kinetics and column dynamics of ad(de)sorption from bulk liquid mixtures using surface excess as the variable to quantify the extent of adsorption. It is found that the transient rate of change of surface excess with time from a multicomponent liquid mixture can be expressed in terms of a surface excess linear-driving-force model. A local-equilibrium model can be developed to describe the column dynamics of ad(de)sorption from liquid mixtures. Both self-sharpening and proportionate pattern mass-transfer zones can be formed depending on the shape of the surface-excess isotherm and the selectivity of adsorption. Analysis of column dynamics for liquid mixture adsorption can be carried out analogous to that for adsorption from gas mixtures, when a constant pattern mass-transfer zone is formed. The length of the mass-transfer zone and the composition-time column effluent profile can also be derived analytically for such a case. Experimental kinetics and column dynamics data for ad(de)sorption of ethanol-water mixtures on a large-pore activated carbon are analyzed using these models.
    Additional Material: 7 Ill.
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  • 124
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 857-867 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pressurization and blowdown steps in pressure swing adsorption (PSA) with binary mixtures of inert and adsorbable species are studied. Modeling involves mass balances for the bulk fluid phase and inside particles, that is, intraparticle diffusion/convection models, momentum balance equations, and linear adsorption equilibrium isotherm. The importance of intraparticle convection in PSA is assessed. Mass transfer inside pores is enhanced by intraparticle convection, which leads to a better efficiency of adsorption (pressurization) and desorption (blowdown) processes. Performance is improved by intraparticle convection and lies between diffusion and equilibrium limits, as shown in propagation profiles of the adsorbable species mole fraction in the bed and inside particles.
    Additional Material: 9 Ill.
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  • 125
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 887-900 
    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 mathematical model, based on the dusty-gas model extended with surface diffusion, is presented that describes mass transport owing to molecular diffusion and viscous flow, as well as an instantaneous reversible reaction inside a membrane reactor. The reactants are fed to opposite sides of the membrane, considering masstransfer resistances in the gas phase outside the membrane. The Claus reaction is chosen as a model reaction to study this membrane reactor.The model is used to validate a previously presented simplified model. The simplified model predicts correct molar fluxes when it is very dilute and can therefore be considered a pseudo-binary system. Occurrence of a maximum or a minimum in the pressure profile inside the membrane, in the absence of an overall pressure difference over the membrane, depends not only on the stoichiometry of the reaction but on mobilities of the different species.The Claus reaction is used to verify experimentally the transport model for a nonpermselective membrane reactor with a mean pore diameter of 350 nm. At 493 K and 542 K, molar fluxes experimentally determined are 10 to 20% lower than those predicted by the transport model. Conversions measured at pressures of 220 kPa and 500 kPa demonstrate that surface diffusion occurs as a transport mechanism despite the large pore diameter of the membrane. In the presence of a pressure difference over the membrane, there is a reasonable agreement between experimentally determined molar fluxes and those calculated by the transport model.
    Additional Material: 14 Ill.
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  • 126
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 911-925 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Polycondensation processes include up to three distinct process stages: prepolymerization, polymerization, and finishing. One or more of these stages often have serious reaction rate limitations due to chemical equilibrium and the need to remove a condensate product. The problems arising in each process stage and the methods of designing each stage are unique. This article discusses many of the problems inherent to each process stage and basic design tools useful in designing each process stage. Two process design tools discussed are the mass-transfer potential and pressure-chain length plots. The application of these tools is illustrated through two design examples: nylon-6,6 and poly (ethylene terephthalate) production.
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  • 127
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    AIChE Journal 38 (1992), S. 959-965 
    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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  • 128
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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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  • 129
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    AIChE Journal 38 (1992), S. 308-310 
    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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  • 130
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1923-1945 
    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 concerns the synthesis of discrete-time nonlinear controllers for nonlinear processes that make the closed-loop system linear in an input/output sense. The synthesis of state feedback controllers is studied first, followed by the synthesis of dynamic output feedback controllers. Both problems are solved within the globally linearizing control (GLC) framework. Precise theoretical connections between the derived controllers and model algorithmic control (MAC) are established. The theory is illustrated by a chemical reactor example.
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  • 131
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1946-1956 
    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 article outlines a computational procedure for the prediction of dispersed two-phase, solid-liquid and gas-liquid, turbulent flows in baffled, impeller-stirred vessels common in the chemical industries. A two-flow Eulerian model is employed, based on the main assumption of interpenetrating coexisting continua. Mean momentum and mass conservation equations are solved for each phase and turbulent closure is effected by extending the single phase k-ε turbulence model to two-phase flows. The resulting set of highly coupled equations is solved by a two-phase implicit algorithm, PISO-2P, which allows calculation for a wide range of phase fraction, particle size and phase density rations. Predictions are presented for solid-liquid and gas-liquid (bubbly) flows. Comparisons are made with experimental data for the mean phase velocities and volume fraction, mean slip velocity and turbulence quantities.
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  • 132
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1990-1994 
    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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  • 133
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1995-1995 
    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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  • 134
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    AIChE Journal 38 (1992), S. 1957-1968 
    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 membranes with pores filled with organic chelation acid show promise as the basis for inorganic membrane separator units for metal ion separations from dilute aqueous streams. The performance of such membranes in disk geometry is evaluated experimentally for a model system. The proposed model describes the metal ion flux through the membrane, and a batch or continuous operated separator using these membranes is analyzed. Copper ion fluxes through α-alumina/silica disks impregnated with 2-hydroxy-5-nonylacetophenone oxime were determined from a rotating diffusion cell apparatus for feed solution concentration of copper 0.03 mol/L, feed solution pH 3, strip solution pH of 0.3, and rotation speed of 130 rpm. Flux values range from 5.4 × 10-6 to 2.2 × 10-5 mol/cm2·h and compare well with the reported values for metal ion transport through polymeric supporting membranes (Largman and Sifniades, 1978; Babcock et al., 1981; Teramoto and Tanimoto, 1983; Kojima and Miyauchi, 1981).The proposed steady-state flux model describes the metal flux through chemically active liquid membranes in inorganic supports. The model includes film resistance to mass transfer in both liquid films, complexation and stripping reactions at the liquid-liquid interface in the membrane pores on both surfaces of the membrane, and metal ion/complex diffusion through the membrane. Separately designed experiments were executed using a precise pH-static technique to obtain the physical and chemical parameters of diffusivities, kinetic coefficients and equilibrium coefficients. Calculated fluxes compare well with experimentally determined values from batch experiments (average standard error, 11%).The proposed lumped parameter linear kinetic rate model for the surface reaction rates interprets the kinetic data for the copper chelation reaction. The model is based on a multistep reaction mechanism and has the following form for the extraction reaction for the above mentioned conditions: \documentclass{article}\pagestyle{empty}\begin{document}$$ R^F = 7.3 \times {\rm 10}^{{\rm - 4}} C_{Cu}^{F*} - 7.1 \times {\rm 10}^{{\rm - 6}} C\frac{F^*}{{CuR_2 }} $$\end{document} A similar expression is presented for the strip reaction.An analytical solution for the mathematical model predicts the performance of the chemically active liquid membrane reactor for the batch or continuous operation of the rotating diffusion cell. Calculated results describe expected trends and agree well with the experimental results.
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  • 135
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    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.
    Additional Material: 14 Ill.
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  • 136
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    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
    Additional Material: 3 Ill.
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  • 137
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    AIChE Journal 38 (1992), S. 619-622 
    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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  • 138
    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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  • 139
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    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.
    Additional Material: 14 Ill.
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  • 140
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    AIChE Journal 38 (1992), S. 753-760 
    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 modified van der Waals theory of interfaces (gradient theory) is used with the equations of state of Peng-Robinson and Mohanty-Davis to predict surface tensions of various nonpolar, quadrupolar, slightly polar and polar substances as a function of temperature. The influence parameter of the gradient theory is estimated as 0.785ab2/3 in terms of the attractive and repulsive van der Waals parameters using the Lennard-Jones potential. The predictions made with the Mohanty-Davis equation of state agree better with experimental data than those made with Peng-Robinson, even for nonpolar fluids.
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  • 141
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    AIChE Journal 38 (1992), S. 788-792 
    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: 8 Ill.
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  • 142
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    AIChE Journal 38 (1992), S. 821-834 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various nonlinear wavy regimes of a viscous liquid film flowing down vertical wires and tubes were calculated using the integral method. The linear stability analysis of the trivial smooth solution was compared with the results published previously. In the region of linear instability, the competition among the gravity, viscous and capillary forces formed the steady-state traveling solutions of finite amplitudes. At least two families of waves were shown to be parameterized by the wave number for given values of external parameters (Reynolds number, cylinder radius and physical characteristics of liquid). The basic waves characteristics depended on external parameters and on wave number. The intensity of wavy processes increased with decreasing cylinder radius. The calculations show the catastrophic growth of wave amplitude, when the system flows down a vertical tube of sufficiently small radius and moves into the linear, unstable region.
    Additional Material: 16 Ill.
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  • 143
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    AIChE Journal 38 (1992), S. 879-886 
    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 type of fluidized bed, called a circulating fluidized-bed adsorber (CFBA), was developed for processing a large quantity of water with high efficiency. Its fluid mechanical characteristics are reported, as well as recovery of uranium from natural seawater using a small CFBA. Using hydrous titanium oxide, granulated with polyacrylonitrile (PAN-HTO), as an adsorbent, CFBA ran stably for six days, the period required for the adsorbent to collect a practical amount of uranium. To predict the uranium adsorption performance of a plant-size CFBA, a numerical model simulating the adsorption kinetics was developed. The result of the numerical calculation by the model was in good agreement with the experimental data.
    Additional Material: 9 Ill.
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  • 144
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    AIChE Journal 38 (1992), S. 1199-1205 
    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 studies have been performed to assess the effect of drop charge on turbulent drop coalescence. Although it is well known that surface charge can affect coalescence rates of Brownian particles in a quiescent medium, no studies have been found in the literature which explicitly examine charge effects on larger drops in turbulent media.Results demonstate that drop charge can substantially inhibit coalescence between drops in agitated dispersions. Moreover, this effect can arise solely from latent drop charges, which are attributed to the preferential adsorption of hydroxide ions onto the water-organic phase interface. Ionic strength and pH thus are shown to play a major role in determining coalescence rates between agitated drops.Results also demonstrate that reliance on measurement of average drop sizes for the purpose of determining coalescence rate dependencies is a precarious practice. Strong size-dependent effects such as obtained here have the potential to suggest erroneous conclusions when conclusions are based on measurements of average drop sizes rather than of drop-size distributions.
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  • 145
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    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
    Additional Material: 3 Tab.
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  • 146
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    AIChE Journal 38 (1992), S. 1304-1305 
    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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  • 147
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    AIChE Journal 38 (1992), S. 1340-1348 
    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 is the first of two articles dealing with fluid flow in compressible porous media. In this article a model describing fluid flow and pressure-induced variations in porosity under stationary conditions is developed. In a forthcoming article the dynamic behavior during filtration and wet pressing of compressible porous media are presented.Fluid flow through rigid porous media is generally described by Darcy's law. The corresponding expression for compressible materials is derived in this article. This expression, the steady-state flow (SSF) equation, allows the steady-state flow to be easily calculated, either numerically, or by using the approximative analytical solutions that are also presented here. In the SSF equation optional empirical and/or theoretical permeability and compressibility relationships may be combined. Further, a new compressibility model which also applies for viscoelastic materials is presented. The influence of the compressibility of the material and the influence of precompression is illustrated.
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  • 148
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    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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  • 149
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    AIChE Journal 38 (1992), S. 1864-1870 
    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 gas holdup in different arrays of expanded metal sheets was determined by the conductimetric method.A model had to be developed for analyzing the conductimetric behavior of the cell in the presence of the metallic sheets. The validity of this model has been verified with single phase flow. The application to two-phase flow allowed the obtaining of information on gas accumulation within stacked expanded metal sheets, showing a strong influence of the geometry of the array. Depending on the orientation of the stacked sheets and of the large dimension of the expanded metal, the gas holdup within the packing will be equal or larger than in an empty bubble column.
    Additional Material: 9 Ill.
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  • 150
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    AIChE Journal 38 (1992), S. 1881-1904 
    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 article presents a combined analytical-numerical study for the hydrodynamic interactions of an arbitrary finite cluster of spherical droplets at low Reynolds numbers. The droplets may differ in radius, in viscosity and in migration velocity. The theory developed is the most general solution to the mobility or resistance problem of slow motion of an assemblage of fluid spheres in a three-dimensional unbounded medium. Using a boundary collocation technique, the creeping flow equations are solved in the quasisteady situation, and the interaction effects among the droplets are evaluated for various cases. For the motion of two-droplet systems, our results for the droplet interaction parameters at all orientations and separation distances agree very well with the exact solutions obtained by using spherical bipolar coordinates or the asymptotic solutions obtained by using the connector algebra. The mobility parameters of linear chains of three droplets have been calculated, demonstrating that the existence of the third sphere can significantly affect the mobility of the other two spheres. The mobility results are also presented for the motion of chains containing up to 101 identical and equally spaced spheres, and the end effect exhibited by a chain of spheres can be found. Finally, our “exact” solutions for the hydrodynamic interaction between two fluid or solid spheres are used to find the effect of volume fractions of particles of each type on the mean settling velocities of the particles in a bounded suspension.
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  • 151
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    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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  • 152
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    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.
    Additional Material: 7 Ill.
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  • 153
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    AIChE Journal 38 (1992), S. 1995-1996 
    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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  • 154
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    AIChE Journal 38 (1992), S. 1996-1996 
    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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  • 156
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    AIChE Journal 38 (1992), S. 1999-1999 
    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 38 (1992), S. 2000-2000 
    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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  • 158
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    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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    AIChE Journal 38 (1992), S. 1145-1156 
    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 recent years, differential geometric techniques have been used to transform nonlinear systems into linear systems. Once such equivalent linear systems are obtained, classical linear controllers are designed to achieve desired stability and performance properties. A major critism against these techniques is their lack of guarantee for robustness. In particular, the design of controllers for transformed nonlinear systems under the influence of both disturbances and (parametric) modeling errors is not well-known. This article presents a methodology to design robust stabilizing controllers for such uncertain and perturbed nonlinear systems.For feedback linearizable systems, the method guarantees that the nonlinear system has nominally linear input/output dynamics and is stable for the given class of bounded parametric uncertainty and disturbances. The new concepts and the proposed design procedure are shown for an isothermal reactor with second-order kinetics.
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  • 160
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    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.
    Additional Material: 9 Ill.
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  • 161
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    AIChE Journal 38 (1992), S. 1288-1293 
    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 method is presented for identifying a subset of species (from a set of reacting species) that are within a specified numerical tolerance of equilibrium, as implied by a given experimental composition. The method also determines a linearly independent set of reactions involving these species and the number of stoichoimetric restrictions inherent in the set. This is an aid in reactor modeling, for example, in the computation of concentration profiles, in examining kinetic schemes or reaction mechanisms, and in identifying rate-controlling processes. An example involving the methanol-to-gasoline synthesis is given to illustrate the method.
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    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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  • 163
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    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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  • 164
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    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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  • 165
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    AIChE Journal 38 (1992), S. 1618-1630 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of concentration on the sedimentation rate of uncharged rigid spheres was investigated. Three submicron sizes of silica spheres were prepared according to the method of Stöber (1968). The particles were sterically stabilized by chemisorption of stearyl alcohol at their surface by the method developed by van Helden (1981). The sterically stabilized silica particles dispersed in cyclohexane are known to behave as hard spheres. Monodisperse gravity sedimentation experiments were carried out for the various particle species over a wide concentration range of φ = 0.003 to φ = 0.37, where φ is the particle volume fraction in cyclohexane. The data for dilute suspensions (φ 〈 0.03) were found to be well described by Batchelor's equation: U/U0 = 1-6.55φ, where U is the sedimentation velocity and U0 is the Stokes velocity of a sphere in isolation. The data over the entire concentration range (0〈φ〈0.37) were found to be well described by the equation: U/U0 = (1-φ)6.55.Bidisperse sedimentation experiments were also carried out, and the dilute data were found to be well represented by Batchelor's 1982 theory for polydisperse suspensions. The high concentration data were analyzed in terms of a model that does not distinguish between interactions of like and unlike particles.
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  • 166
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    AIChE Journal 38 (1992), S. 211-218 
    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 desorption of trihalomethanes (THMs) in a cocurrent bubble column has been studied experimentally to validate a previously developed model. The experiments were carried out in a 0.2-m-diameter, 2.4-m-high, plexiglas bubble column, equipped with seven samplers alongside. The phases in contact were tap water and air. Three out of the four THMs normally found in drinking water were spiked in the feed tank to assure their detection in the analyses. After preparing the feed, each run was begun by setting the flow rates of water and air, and waiting until a steady state was attained. Then, samples from each sampler were taken and sent for chemical analysis. A total of 12 runs were performed with varying superficial gas and liquid velocities, and up to four concentration profiles were obtained for each run. The experimental results were then compared to the predictions of the model proposed by Estévez (1991). The agreement between calculated and experimental concentration profiles was quite good, indicating that the model can be used reliably either in the simulation or design of industrial scale equipment.
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  • 167
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    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
    Additional Material: 4 Tab.
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  • 168
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    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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  • 169
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    AIChE Journal 38 (1992), S. 416-424 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dynamic analysis of single-pellet cell for the measurement of diffusion and convection in porous catalysts is revisited. A complete mathematical model for the “diffusion-convection” cell is solved, and the relation between zero-and first-order moments of the cell response and operating parameters is derived. The validity region of the “simplified” boundary condition at the bottom of the pellet is quantified. The effect of the operating parameters on the cell time response to a tracer impulse is analyzed to check the practical range of operation of the system. It also is compared with the chromatographic technique.
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  • 170
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    AIChE Journal 38 (1992), S. 455-460 
    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 Kinetics of the reaction between carbon dioxide and methyldiethanolamine (MDEA) were studied in the presence of various amounts of phosphoric acid at 298 K, 308 K, and 318 K. A stirred cell with a known interfacial area was used at atmospheric pressure to measure the volumetric absorption rate of CO2 flowing through the vessel.The addition of phosphoric acid to an aqueous solution of MDEA resulted in a Bronsted acid-base neutralization reaction. While virtually all of the acid was consumed by the neutralization reaction, a large part of the MEDA remained in its free form. The absorption of carbon dioxide in these solutions was slower than expected, given the amount of free MDEA present. The rate depression in the presence of hydrogen phosphate anions was attributed to the stabilization of the reaction transition state between MDEA, water, and carbon dioxide through charge dispersal.
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  • 171
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    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
    Additional Material: 4 Ill.
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  • 172
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    AIChE Journal 38 (1992), S. 1170-1184 
    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 existing models of the foaming process in reaction injection molding are inadequate for predicting the bubble-size distribution, which influences many properties of interest. This work attempts to develop a model for the bubble-size distribution under conditions of free rise.The population balance equation for bubbles, coupled with the system of energy balance and reaction kinetics equations through the blowing agent evaporation rate expression, is solved to obtain the bubble-size distribution. A simple mass-transfer coefficient approach for expressing growth rate of bubbles is used, although various growth laws can be accommodated without affecting the solution procedure. Determining factors for the bubble size and its distribution are the foaming period and the growth law. With increase in initial blowing agent concentration, the foaming period increases and bigger bubbles are obtained. The bubble-size distribution becomes broader as the foaming period increases.
    Additional Material: 17 Ill.
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  • 173
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    AIChE Journal 38 (1992), S. 1499-1511 
    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 hybrid neural network-first principles modeling scheme is developed and used to model a fedbatch bioreactor. The hybrid model combines a partial first principles model, which incorporates the available prior knowledge about the process being modeled, with a neural network which serves as an estimator of unmeasured process parameters that are difficult to model from first principles. This hybrid model has better properties than standard “black-box” neural network models in that it is able to interpolate and extrapolate much more accurately, is easier to analyze and interpret, and requires significantly fewer training examples. Two alternative state and parameter estimation strategies, extended Kalman filtering and NLP optimization, are also considered. When no a priori known model of the unobserved process parameters is available, the hybrid network model gives better estimates of the parameters, when compared to these methods. By providing a model of these unmeasured parameters, the hybrid network can also make predictions and hence can be used for process optimization. These results apply both when full and partial state measurements are available, but in the latter case a state reconstruction method must be used for the first principles component of the hybrid model.
    Additional Material: 18 Ill.
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  • 174
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    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.
    Additional Material: 17 Ill.
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  • 175
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    AIChE Journal 38 (1992), S. 1577-1592 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient temperature profiles for long rods of lossy dielectric materials with thermally-dependent dielectric properties exposed to uniform plane waves are obtained. Maxwell's equation and the heat equation are simultaneously solved using the finite element method to predict the power absorbed and the resulting temperature rise in samples of square and circular cross-section. Following the method introduced recently, we derive an exact radiation boundary condition which is independent of the rod cross-section. For a cylindrical sample, the boundary condition is imposed on the cylinder itself. For a square rod, the boundary condition is imposed on a cylinder containing the rod. The temperature dependence of dielectric properties and sample dimensions appreciably influence heating patterns. For square samples, the edges focus radiation, causing preferential heating at the edges. This effect is pronounced for larger samples. In addition, the incident wave polarization influences the heating of the rod. For waves where the electric field is polarized along the long axis of the sample (TMz polarization) the power absorbed is higher than when the electric field is perpendicular to the axis (TEz polarization). A case involving runaway heating is also investigated.
    Additional Material: 9 Ill.
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  • 176
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    AIChE Journal 38 (1992), S. 1593-1608 
    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 huge amount of data is collected by computer monitoring systems in the chemical process industry. Such tools as principal component analysis and partial least squares have been shown to be very effective in compressing this large volume of noisy correlated data into a subspace of much lower dimension than the original data set. Because most of what is eliminated is the collinearity of the original variables and the noise, the bulk of the information contained in the original data set is retained. The resulting low dimensional representation of the data set has been shown to be of great utility for process analysis and monitoring, as well as in selecting variables for control. These types of models can also be used directly in control system design. One way of approaching this is to use the loading matrices as compensators on the plant. Some advantages of using this approach as part of the overall control system design include automatic decoupling and efficient loop pairing, as well as natural handling of nonsquare systems and poorly conditioned systems.
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  • 177
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    AIChE Journal 38 (1992), S. 1639-1648 
    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 Fischer-Tropsch synthesis reaction was conducted in a supercritical fluid medium using a fixed-bed reactor. Tailor-made catalyst supports which had sharp pore diameter distributions were prepared by the pH swing method. The relationships between the catalyst pore structure and the catalytic activity or the product distribution were studied. The influence of the catalyst pore size on the mass transfer of reactants and products was also characterized. The catalyst pore size affected not only catalytic activity but also product selectivity. The diffusion of reactants inside the catalyst pellets in the supercritical fluid media was simulated and the effects of catalyst pore size and catalyst particle size on catalytic performances were consistent with simulation results.
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  • 178
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    AIChE Journal 38 (1992), S. 1657-1661 
    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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  • 179
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    AIChE Journal 38 (1992), S. 1667-1670 
    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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  • 180
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    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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  • 181
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    AIChE Journal 38 (1992), S. 1685-1692 
    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 formation of submicron crystals of boron carbide (B4C) by coagulation and sintering by the rapid carbothermal reduction of intimately mixed carbon-boron oxide powders in an aerosol flow reactor at temperatures above the boiling point of boron oxide is investigated. High heating rates (105K/s) force rapid evaporation of boron oxide and suboxides from the precursor powder, resulting in its rupture and formation of boron carbide molecular clusters that grow to macroscopic particles by coagulation. Consequently, the formation and growth of B4C particles are described by simultaneous interparticle collision and coalescence using a two-dimensional particle-size distribution model that traces the evolution of both size and shape characteristics of the particles through their volume and surface area. In addition to the coagulation term, the governing population balance equation includes a coalescence contribution based on B4C sintering law. The predicted evolution of the two-dimensional particle-size distribution leads to a direct characterization of morphology as well as the average size and polydispersity of the powders. Furthermore, model predictions of the volume and surface area of boron carbide particles can be directly compared with experimental data of B4C specific surface area and an effective sintering rate of B4C is deduced.
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  • 182
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    AIChE Journal 38 (1992), S. 1693-1702 
    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 physicochemical model for vapor-liquid equilibrium in multicomponent formaldehyde-containing mixtures (Maurer, 1986; Hasse et al., 1990; Hasse and Maurer, 1991a). is extended to describe enthalpy changes upon vaporization. Predicted enthalpy changes are compared with new experimental results. The measurements were carried out with a thin-film evaporator flow-calorimeter (Liu and Maurer, 1991). More than 80 experimental data points for mixtures of formaldehyde + water and formaldehyde + methanol + (small amounts of water) are reported. The data cover the temperature range from 323 to 363 K (formaldehyde + water) and 312 to 347 K (formaldehyde + methanol) at liquid phase formaldehyde mole fractions up to about 0.3 (formaldehyde + water) and 0.6 (formaldehyde + methanol). Comparisons between predicted and experimental results for the enthalpy change reveal deviations of only a few percent. Further improvements are achieved by fitting some model parameters, which originally were estimated from noncalorimetric data.
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  • 183
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    AIChE Journal 38 (1992), S. 1716-1728 
    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 falling liquid film has become a popular means of transferring heat and mass from a vapor to a binary liquid film; applications include heat pump systems, desalination, and gas-liquid contactors. In the heat pump application, in particular, the length of the liquid film is a crucial factor because of size and weight limitations. Consequently, it is desirable to be able to predict the amount of mass absorbed in a given length of tube. In this work the absorption of water vapor into a Lithium-Bromide Water mixture is considered. It is shown that mass transfer takes place in a thin layer of fluid near the liquid-vapor interface which is indicative of a very high level of liquid-side mass-transfer resistance. Closed form solutions for the velocity field may be used to derive a simple closed form solution for the mass fraction. For very thin films the temperature distribution may be obtained analytically in Laplace transform space; however, due to the complexity of the solution, numerical techniques are employed to obtain quantitative results. For thicker films a closed form solution for the temperature may be obtained as well. The principal objective of this work is to develop a design procedure not requiring a significant amount of numerical work whereby the absorption capacity of a given tube may be predicted as a function of the governing geometrical and physical parameters. The analytical/numerical results are presented for parameters corresponding to those of recent experiments and the agreement between theory and experiment is good.
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  • 184
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    AIChE Journal 38 (1992), S. 1744-1750 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous separation of three carbohydrate mixtures [fructose-dextran (M. W. ≈ 9,400), raffinose-dextran (M. W. ≈ 6,000), and fructose-raffinose] has been carried out using a simulated countercurrent process with silica gel as the sorbent and deionized water as the eluent. Experiments were conducted using the commercial four-section arrangement and a modified three-section flow scheme which does not recycle part of the eluent for reuse. Data for the four-section flow scheme reflect a much higher product concentration in the raffinate and a substantially lower rate of fresh eluent consumption than for the three-section scheme. It is concluded that when both the extract and raffinate products are desired, the four-section scheme should be used for the separation of a mixture with a small separation factor which usually requires a large quantity of eluent to achieve an efficient separation. The behavior of the simulated countercurrent process was simulated theoretically by representing the process in terms of an equivalent true countercurrent system. A good fit to the experimental data was obtained when the process was configured in the four-section mode. However, the same theoretical approach failed to provide a good representation of the behavior of the three-section scheme in one respect: predicted concentrations of the raffinate product were about two times higher than experimental values. The discrepancy may be attributed to the periodic switching of fluid inlet and outlet points in the operation of the three-section simulated countercurrent unit.
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  • 185
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    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.
    Additional Material: 35 Ill.
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  • 186
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    AIChE Journal 38 (1992), S. 1769-1800 
    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 article introduces the “state space” conceptual framework to process synthesis, which is used to provide a novel representation of a distillation network as a composite heat- and mass-exchange network. This representation suggests that distillation network synthesis may best be viewed as an interacting heat- and mass-exchange network synthesis problem. In that regard, familiar tools (such as pinch diagrams) from both heat-exchange network (HEN) and mass-exchange network (MEN) synthesis are shown to be of use in arriving at energy-efficient distillation network designs. Examples of propylene-propane and solvent-water separations are used to illustrate the proposed conceptual framework.
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  • 187
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    AIChE Journal 38 (1992), S. 1840-1842 
    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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  • 188
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    AIChE Journal 38 (1992), S. 1847-1851 
    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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  • 189
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    AIChE Journal 38 (1992), S. 1853-1863 
    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 influence of growth rate dispersion on the product-size distribution of batch cooling crystallization is investigated by computer simulations. The model accounts for primary and magma density-dependent secondary nucleation, and growth rate dispersion of the constant crystal growth type. The model is solved by a combination of the method of characteristics and moment analysis, by which the entire product-size distribution is recovered. The study includes three different growth rate activity distributions, and the influence of the corresponding coefficient of variation is analyzed for unseeded and seeded processes. The results show that the effect of growth rate dispersion on the crystal-size distribution may be significant even at moderate dispersion. At high dispersion, even the actual shape of the growth rate activity distribution may become important.
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  • 190
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 191
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    AIChE Journal 38 (1992), S. 343-362 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is presented for a quantitative prediction of the transfer rates of momentum, heat and mass in turbulent pipe flow. In this so-called extended random surface renewal (ERSR) model, the tube wall is assumed to be covered by a mosaic of fluid elements of random age and laminar flow with unsteady profiles of axial velocity, temperature or concentration.Both the age distribution and the mean age of the fluid elements at the tube wall, predicted by the ERSR model, quantitatively agree with experimental results obtained from velocity signals measured with a laser-Doppler anemometer at 5·103≤Re≤43·103. The time-averaged radial profiles of the axial velocity, the temperature and the concentration in the wall region, and the heat- and mass-transfer coefficients derived with the ERSR model agree with empirical results presented in literature. Furthermore, the ERSR model provides a basis for explaining the Chilton-Colburn analogy.
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  • 192
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    AIChE Journal 38 (1992), S. 405-415 
    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 Vrentas/Duda free-volume diffusion model accurately correlates polymer/solvent diffusion coefficients over wide ranges of concentration and temperature. Currently the model is semipredictive: limited diffusion data are required to estimate model parameters that can then be used to predict diffusion coefficient behavior over sundry conditions. In this work, we present methods for estimating all of the model parameters without any diffusion data and examine the accuracy of the resulting diffusion coefficient predictions. This is the only technique known that predicts polymer/solvent diffusion behavior without any use of any diffusion data.
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  • 193
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    AIChE Journal 38 (1992), S. 445-454 
    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 deposition of yttria-doped zirconia has been experimented systematically in various types of porous ceramic substrates by a modified chemical vapor deposition (CVD) process operating in an opposing reactant geometry using water vapor and corresponding metal chloride vapors as reactants. The effects of substrate pore dimension and structure, bulk-phase reactant concentration, reactant diffusivity in substrate pores and deposition temperature are experimentally studied and explained qualitatively by a theoretical modeling analysis. The experimental and theoretical results suggest a reaction mechanism which depends on water vapor and chloride vapor concentrations. Consequently, the diffusivity, bulk-phase reactant concentration, and substrate pore dimension are important in the CVD process. Effects of deposition temperature on the deposition results and narrow deposition zone compared to the substrate thickness also suggest a Langmuir-Hinshelwood reaction mechanism involved in the CVD process with a very fast CVD reaction rate. Gas permeation data indicate that whether deposition of solid in substrate pores could result in the pore-size reduction depends strongly on the initial pore-size distribution of the substrate.
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    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).
    Additional Material: 6 Ill.
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  • 195
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 471-472 
    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.
    Type of Medium: Electronic Resource
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  • 196
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 939-944 
    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 finite element analysis was carried out to study the mixing patterns of a viscous Newtonian fluid into a stirred tank. A helical ribbon screw impeller (HRS) was used as the mixing device. The numerical simulation involved the full three-dimensional resolution of the equations of change governing the flow in the tank. The circulation time and the torque were determined and compared with experimental data. A good agreement was found, showing the usefulness of the numerical approach for design purposes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 197
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 988-1002 
    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 mathematical model is developed for deep-well oxidation of wastes in supercritical water. The model accounts for the variation of thermodynamic and transport properties with temperature and pressure. It is used to examine the steady-state behavior of the supercritical-water deep-well oxidation reactors. The effects of inlet flow rate, heat losses from the reactor, inlet concentration of organics, oxygen injection depth, reactor length, inlet pressure, and inlet temperature on the exit conversion and the bottom temperature are examined. The simulations show that under practical conditions the capacity of the reactor is dictated by hydrodynamic considerations rather than the oxidation kinetics, and that obtaining temperatures of 10 to 50 K above critical temperature at the bottom of the reactor requires longer tubes and/or high inlet pressures. Heat losses to the earth can be modeled accurately by treating the earth as an infinite reservoir by properly choosing the effective heat-transfer coefficient.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 198
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 969-987 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Settling rates, yield stresses, and shear-stress/shear-rate dependences were determined as functions of solids concentration for suspensions in water of coal particles of narrow size fractions. Particles and suspensions are characterized by coal analyses, determination of heating value, solid heat capacity and thermal conductivity, particle size analyses, and determination of densities and maximum packing concentrations for each particle size range. Analysis of the settling rate data establishes that the usually strong retardation of (hindered) settling due to concentration is compounded by particle shape effects. In addition, observed particle shapes are subsumed within particle shape classes inferred from the settling data. Shear-stress/shear-rate data for concentrated suspensions of the three larger and relatively narrower sized particles over the broad range of shear rates from about 1 to 104S-1 suggest the behavior to be essentially Newtonian, albeit with a marked particle concentration augmentation. Suspensions of the smallest coal particles of broader size distribution were strongly non-Newtonian, possessing a yield stress at low shear, essentially power-low shear-thinning behavior over the intermediate range and approaching high-shear Newtonian limiting behavior above about 103S-1. Relations developed include viscosity-and yield stress-concentration correlations incorporating the maximum packing volume fraction of solids. These are useful generally for suspensions and particularly as the basis for guiding the formulation of coal-water fuels.
    Additional Material: 11 Ill.
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  • 199
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1049-1058 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Generalized drift-flux expressions for horizontal three-phase (gas/water/oil) conduit flows have been derived. A detailed set of phasic volume fraction data were measured for the various flow regimes observed in air/water/oil flows. This article shows that drift-flux techniques can be used to predict the phasic volumetric fractions for horizontal three-phase flows, such as those which may occur in off-shore oil well lines.
    Additional Material: 18 Ill.
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  • 200
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 2000-2001 
    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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