A diffuse interface model for fluid—solid reaction

Bowen, J.H.; Cheng, C.K.

doi:10.1016/0009-2509(69)87025-9

Cited by 50 publications

(22 citation statements)

References 2 publications

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“…Such a zone was postulated by Bowen and Cheng (1969) who presented an analysis assuming linear gas concentration and solid conversion profiles. This technique was subsequently used by Shettigar and Hughes (1972) the modelling of combustion of coke deposits in catalyst pellets.…”

Section: Reaction Zonementioning

confidence: 97%

Mathematical Modelling of Gas-Solid Reactions: Effect of Pore Structure

Bhatia¹,

Gupta²

1992

Reviews in Chemical Engineering

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Section: Reaction Zonementioning

confidence: 97%

Mathematical Modelling of Gas-Solid Reactions: Effect of Pore Structure

Bhatia¹,

Gupta²

1992

Reviews in Chemical Engineering

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“…Assuming that the variation of concentration in the reaction zone is linear [13], the following equations are obtained:…”

Section: Mathematical Modelmentioning

confidence: 99%

Generalized diffuse interface model for determination of kinetic parameters in high-temperature internal corrosion reactions (gas/solid system)

Khan

Alhajji

Reda

1998

Int. J. Chem. Kinet.

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Diffuse Interface Model (DIM) is introduced to describe the mechanism of hightemperature corrosion/internal oxidation. The zone has dissolved oxygen and metal atoms diffuse and react resulting in the inward movement of zone. The high-temperature oxidation data for cobalt, iron, and nickel, which are for metal deficit (p-type), have been analyzed using a nonlinear optimization method to obtain the optimal values for different parameters, diffusivity of metal atoms in metal oxide, diffiusivity of gaseous species in the corrosion product, diffusivity of oxidant in the unreacted solid (metal or alloy), the rate constant for the reaction and the fraction of the zone reacted. The expression for diffusivity in the reaction zone has been modified by relating diffusivities of the product layer and the core as function of fraction of zone reacted. The model was applied to the experimental data for the high-temperature oxidation of cobalt, iron, and nickel by pure oxygen at an atmospheric pressure. The model predicts the values of diffusion coefficients, preexponential factors, and activation energies for diffusion process, which are generally compared favorably with those reported in the literature. Linear relationship are derived relating the diffusion coefficient in the core and product layer to the parabolic rate constant which is valid for iron, cobalt, and nickel for hightemperature oxidation (900-1350ЊC) by oxygen at an atmospheric pressure according to the following equations:

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“…A particularly important class of non-structural models is the group of zone models in which a reaction zone is sandwiched between the ash layer and the unreacted core (Bowen and Cheng, 23 Mantri et al, 24 Bowen et al, 25 Dudukovic and Lamba 26 ). The experimental results of Prasannan and Doraiswamy 27 on the oxidation of zinc sulfide clearly reveal all three stages of the reaction.…”

Section: Gas-solid Reaction Modelsmentioning

confidence: 99%

Engineering a New Material for Hot Gas Cleanup

Wheelock¹,

Doraiswamy²,

Constant³

2003

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The overall purpose of this project was to develop a superior, regenerable, calcium-based sorbent for desulfurizing hot coal gas with the sorbent being in the form of small pellets made with a layered structure such that each pellet consists of a highly reactive lime core enclosed within a porous protective shell of strong but relatively inert material. The sorbent can be very useful for hot gas cleanup in advanced power generation systems where problems have been encountered with presently available materials.An economical method of preparing the desired material was demonstrated with a laboratory-scale revolving drum pelletizer. Core-in-shell pellets were produced by first pelletizing powdered limestone or other calcium-bearing material to make the pellet cores, and then the cores were coated with a mixture of powdered alumina and limestone to make the shells.The core-in-shell pellets were subsequently calcined at 1373 K (1100°C) to sinter the shell material and convert CaCO 3 to CaO. The resulting product was shown to be highly reactive and a very good sorbent for H 2 S at temperatures in the range of 1113 to 1193 K (840 to 920°C) which corresponds well with the outlet temperatures of some coal gasifiers. The product was also shown to be both strong and attrition resistant, and that it can be regenerated by a cyclic oxidation and reduction process.A preliminary evaluation of the material showed that while it was capable of withstanding repeated sulfidation and regeneration, the reactivity of the sorbent tended to decline iv with usage due to CaO sintering. Also it was found that the compressive strength of the shell material depends on the relative proportions of alumina and limestone as well as their particle size distributions. Therefore, an extensive study of formulation and preparation conditions was conducted to improve the performance of both the core and shell materials. It was subsequently determined that MgO tends to stabilize the high-temperature reactivity of CaO. Therefore, a sorbent prepared from dolomite withstands the effects of repeated sulfidation and regeneration better than one prepared from limestone. It was also determined that both the compressive strength and attrition resistance of core-in-shell pellets depend on shell thickness and that the compressive strength can be improved by reducing both the particle size and amount of limestone in the shell preparation mixture.A semiempirical model was also found which seems to adequately represent the absorption process. This model can be used for analyzing and predicting sorbent performance, and, therefore, it can provide guidance for any additional development which may be required.

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A diffuse interface model for fluid—solid reaction

Cited by 50 publications

References 2 publications

Mathematical Modelling of Gas-Solid Reactions: Effect of Pore Structure

Mathematical Modelling of Gas-Solid Reactions: Effect of Pore Structure

Generalized diffuse interface model for determination of kinetic parameters in high-temperature internal corrosion reactions (gas/solid system)

Engineering a New Material for Hot Gas Cleanup

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