Diffusion in catalyst pellets

Wakao, Noriaki; Smith, J. M.

doi:10.1016/0009-2509(62)87015-8

Cited by 882 publications

(389 citation statements)

References 7 publications

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“…In the way Bell and Crank [11] formulated their cells it is most probable that they encountered this restriction for further analysis. The effective diffusion coefficients predicted by the SP and PS models for square arrays can be obtained from table 1 The model of Wakao and Smith [9] underpredicts the diffusivities obtained from the experimental data whilst both RUC models are in good agreement with the experimental data as well as all the other analytical models. The experimental data of Currie [12] and Hoogschagen [13] were obtained from beds of spheres.…”

Section: Fully Staggered Array Of Squaresmentioning

confidence: 86%

Modelling of diffusion in porous structures

Plessis

Woudberg

2009

WIT Transactions on Engineering Sciences

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An existing pore-scale model is used to predict the effective diffusivity of staggered two-dimensional rectangular unconsolidated arrays through the use of a Representative Unit Cell concept. A tri-diagonal matrix algorithm is used to solve the diffusive flux field and to compute the effective diffusion coefficient for concentration gradients of staggered arrays. The numerical results and analytical model are compared critically with theoretical and numerical studies, as well as experimental data reported in literature. The good correlations obtained for the effective diffusivity provide confidence in both the computational and analytical work.

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Section: Fully Staggered Array Of Squaresmentioning

confidence: 86%

Modelling of diffusion in porous structures

Plessis

Woudberg

2009

WIT Transactions on Engineering Sciences

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“…Now, labyrinth factor can be replaced with porosity in random pore model. 16) Hence labyrinth factors were compared with porosities in Fig. 7.…”

Section: Discussionmentioning

confidence: 99%

Method of Estimation of Reduction Rate Constant in Ishida-Wen’s Model for FeO–Al<sub>2</sub>O<sub>3</sub> Briquette

Kamijo

2017

ISIJ International

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A new estimation method of reduction rate constant in Ishida-Wen's model, which be considered forming of reaction layer, for oxide aggregate such as sinter ore is proposed. Briquettes of FeO-Al 2 O 3 mixture were prepared as a model of sinter ore and reduction test and analysis were taken place. Al 2 O 3 cannot be reduced under this experimental condition so that it acts as a neutral material which obstruct reduction of FeO. Therefore, the influence of existence of

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“…The random pore model is used to convert the diffusivity to the effective diffusivity. This model was originally developed for catalytic pellets containing a bi-disperse pore system [21,22]. The resultant expression for the effective diffusivity may be written 2 2…”

Section: Effective Diffusivitymentioning

confidence: 99%

Modeling high-pressure char oxidation using langmuir kinetics with an effectiveness factor

Hong

Hecker

Fletcher

2000

Proceedings of the Combustion Institute

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The global nth order rate equation has been criticized for lack of theoretical basis and has been shown to be inadequate for modeling char oxidation rates as a function of total gas pressure. The simple Langmuir rate equation is believed to have more potential for modeling high pressure char oxidation. The intrinsic Langmuir rate equation is applied to graphite flake oxidation data and agrees well with reaction rates at three temperatures over the entire range of oxygen pressure (1-64 atm). It also explains the change of reaction order with temperature.In this work, the intrinsic Langmuir rate equation is combined with (1) an effectiveness factor to account for pore diffusion effects and (2) a random pore structure model to calculate effective diffusivity.The resulting model is able to predict the reaction rates of large (ca. 8 mm) coal char particles as a function of gas velocity, total pressure, oxygen partial pressure, oxygen mole fraction, initial particle size, and gas temperature. This approach is also able to correlate the particle burnouts of pulverized (70 lm) coal char particles in a drop tube reactor as a function of total pressure, oxygen mole fraction, gas and wall temperatures, and residence time. The ability of the model to correlate data over wide range of temperature and pressure is promising.

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Diffusion in catalyst pellets

Cited by 882 publications

References 7 publications

Modelling of diffusion in porous structures

Modelling of diffusion in porous structures

Method of Estimation of Reduction Rate Constant in Ishida-Wen’s Model for FeO–Al<sub>2</sub>O<sub>3</sub> Briquette

Modeling high-pressure char oxidation using langmuir kinetics with an effectiveness factor

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