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  • 1
    Electronic Resource
    Electronic Resource
    Diffusion in pore networks: Effective medium theory and smooth field approximation (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1678-1689 
    Details
    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 problem of diffusion in pore networks of a certain class is considered, and a procedure for estimating effective diffusivities is formulated. The effective-medium theory is used to obtain an effective conductance for the network, which is then used to determine the effective diffusivity starting from first physical principles and utilizing the observation that a network of pores of uniform conductance satisfies the smooth field approximation. Comparison of the estimated intraparticle diffusivities with those obtained from the exact solution of the transport equation for large networks reveals high accuracy and reliability of the method. Results for a number of pore networks show that the smooth field assumption should not be employed arbitrarily since it always predicts higher effective diffusion coefficients than the exact ones, by more than one order of magnitude in some cases.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690331011
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic behavior of a porous char particle burning in an oxygen-containing environment: Part I: Constant particle radius (1984)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 30 (1984), S. 537-549 
    Details
    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 transient combustion of porous char particles is modelled. The model takes into account the reactions of carbon with CO2 and O2 and the oxidation of CO in the gas phase. It reveals strong effects of the intraparticle thermal gradients and of the pore structure evolution scheme on the burning time and predicts an optimum particle size that gives minimum burning time.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690300403
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamic behavior of a porous char particle burning in an oxygen-containing environment: Part II: Transient analysis of a shrinking particle (1984)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 30 (1984), S. 549-556 
    Details
    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 diffusion and reaction model developed in a previous paper is extended allowing for shrinkage of the char particles. It is shown that possible shrinkage, arising from disintegration of the solid structure at a certain conversion level, modifies severely the extinction behavior of the reacting particles. Specifically, the region of ambient temperature and particle radius in which the predictions of the nonisothermal and of the isothermal versions of the model differ significantly becomes smaller. However, the particle shrinkage does not affect the ignition phenomena observed since a particle usually ignites at low conversion levels where the radius change is still negligible.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690300404
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    A generalized pore model for gas-solid reactions exhibiting pore closure (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 382-393 
    Details
    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 of pore structure evolution has been developed for gas-solid reactions exhibiting pore closure behavior. A cylindrical pore network of constant coordination number is used to represent the porous medium, and both discrete and continuous distributions of pore size are considered. The mathematical model takes into consideration the effects of pore overlapping and nonuniform pore growth, and follows the formation of inaccessible volume in the interior of the reacting particles by use of percolation theory concepts. The model is applied, along with an appropriate diffusion and reaction model, to the investigation of the transient behavior of calcined limestone particles in an environment of sulfur dioxide.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330304
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    Paper (German National Licenses)
    Fulltext
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