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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 29-38 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model is developed for the drying of solids in fluidized beds, assuming a falling rate period following a constant rate period. Experimental data obtained using batch and continuous single and spiral fluidized beds are satisfactorily matched with the assumed drying kinetics and the residence time distribution of solids appropriate for the type of dryer.
    Additional Material: 13 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1825-1834 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Unsteady axial mixing due to addition of a batch of sodium chloride solution at the top of a water-filled tube (2.63 cm i.d.) has been studied by measuring the developing concentration profile and the advancing front with dye added to the brine. Data have also been obtained with added baffle plates, with the use of a viscous aqueous solution, and in smaller diameter (1.48, 1.91 cm) tubes. Results can be approximately correlated by means of a model based on unsteady one-dimensional turbulent dispersion. Laminar flow affects the behavior of the advancing front at which the salt concentration is lowest.
    Additional Material: 12 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1249-1254 
    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 to describe steady-state nonequilibrium surface diffusion of an adsorbing gas through an energetically homogeneous porous medium by assuming that the adsorption isotherm is linear and that the gas-surface mass transfer can be described by the linear driving force model. Analytical solutions for the model are reported. It is found that the conventional assumption of local thermodynamic equilibrium between the gas and surface phases within the porous medium can seriously underestimate the surface diffusivity when the mass transfer rate is finite. Also, the length of the porous medium becomes a critical variable in that case.Meaningful estimation of surface diffusivity also requires that the gas phase diffusivity through the porous medium be accurately known. The estimated surface diffusivity is model dependent when local thermodynamic equilibrium is not established instantaneously. Modeling surface diffusion can be very complex when the surface is energetically heterogeneous.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    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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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 249-261 
    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 article, we present a model to describe sorption kinetics of gaseous adsorbates onto bidispersed heterogeneous microporous particles. This model describes adsorption and desorption of gaseous adsorbates with allowance for the energy distribution of adsorption site for both equilibrium isotherm and diffusion of the adsorbed species. The adsorbed species of all energy level diffuse in two directions inside the particle. One direction is the direction along the particle coordinate while the other is the direction perpendicular to the particle coordinate (that is, the direction into the grain of the solid). This model is more fundamental than models previously proposed by Do and coworkers. Effects of energy distribution on the adsorption and desorption dynamics are investigated. Extensive experimental analysis of adsorption and desorption dynamics of ethane and propane onto Ajax activated carbon are carried out to validate this theory.
    Additional Material: 10 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1575-1582 
    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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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1019-1026 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Axial dispersion coefficients have been measured in single-phase flow conditions in a 5.08-cm-dia. reciprocating plate extraction column. The measurements were done under steady-state conditions by analyzing temperature profiles (for hot and cold water mixing) and concentration profiles (for mixing of water and salt solutions). The results confirm previous published data of Holmes et al. (1991) in showing that axial dispersion is increased strongly in the unstable situation, where liquid density increases with height. The earlier work is extended to the condition where buoyant energy dissipation is exceeded by mechanical energy dissipation by four orders of magnitude. Even in this case, axial mixing is increased significantly by density gradient-induced instability. Results have been correlated by a simple equation based on a mixing length model.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1870-1884 
    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 numerical study of the bulk hydraircooling of spherical food products is performed using the technique of spraying chilled water to form a thin film over the food products while blowing cold unsaturated air in the countercurrent or cocurrent direction. This precooling process is found to combine the advantages of hydro-and air cooling.Governing equations describing the simultaneous heat and mass transfer occurring in the hydraircooling process for both counterflow and parallel-flow arrangements are solved using finite-difference numerical methods. A parametric study is performed to determine the effect of important processing parameters on the process time. It is generally observed that higher quantities of spray water, air-mass flow rate and product thermal conductivity, as well as lower values of water temperature will result in faster rates of cooling. For the same operating conditions, parallel-flow arrangement leads to higher plant capacities.
    Additional Material: 18 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1332-1340 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Critical impeller speed for the suspension of solid particles, Ncs, has been measured in 0.3, 0.4, 0.57, 1.0, and 1.5 m ID mechanically agitated contactors. Tap water and quartz particles (100, 340, 700, 850, 2,000 μm) were used as liquid and solid phase, respectively. The impeller speed was varied from 3.5 to 13.3 r/s and solid loading from 0 to 50 wt. %. Three types of impellers were employed: disk turbine, pitched turbine downflow, and pitched turbine upflow. The impeller diameter to vessel diameter ratio was varied in the range 0.175 to 0.58 and the impeller blade width to impeller diameter ratio was varied in the range 0.25 to 0.4. The impeller clearance from the tank bottom was varied from 0.5 to 0.167 of tank diameter. The effect of impeller blade thickness was also studied.The pitched-blade impellers were found to be more efficient than a conventional disk turbine, and the pitched turbine downflow type was found to be more efficient than a pitched turbine upflow impeller. An attempt has been made to explain the mechanism of suspension on a rational basis and a correlation has been proposed for the estimation of Ncs that is expected to be useful in design.
    Additional Material: 16 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 918-926 
    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 catalyzed direct reduction of lead sulfide with carbon and lime was investigated at several temperatures and under two different inert gas atmospheres. The catalyzed reduction kinetics were determined both with a nitrogen atmosphere and a helium-rich helium-nitrogen atmosphere. The reduction kinetics under the latter were decidedly superior to those under the former. The differences were interpreted in terms of faster diffusion rates in a helium medium and synergistic effects. The catalyst used was a ternay eutectic mixture (K, Li, Na)2CO3, which amounted to 2.5 wt. % of the PbS:4CaO:4C reaction mixture.
    Additional Material: 14 Ill.
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