DETERMINATION OF EFFECTIVE DIFFUSIVITIES AND CONVECTIVE COEFFICIENTS OF PURE GASES IN SINGLE PELLETS

• Type: Article in International Scientific Journal
• Date: 1995

Authors

SUN, WU (Author) Other; Carlos Costa (Author) FEUP; Alírio Rodrigues (Author) FEUP

Journal

Title: Chemical Engineering Journal and the Biochemical Engineering Journal

Vol. 57 No. 2

Pages: 285-294

ISSN: 0923-0467

Publisher: Elsevier B.V.

Indexing

ISI Web of Knowledge - 8 Citations

ISI Web of Science

Scopus - 10 Citations

COMPENDEX

Scientific classification

CORDIS: Physical sciences > Chemistry > Physical chemistry

Other information

Authenticus ID: P-001-GXG

DOI: 10.1016/0923-0467(94)02877-d

Abstract (EN): The determination of the effective diffusivities and convective coefficients of pure component gases in single porous pellets can be done separately using the diffusion-convection cell experimental technique; this simplifies the experimental procedure and the theoretical exploitation of the experimental results and improves the precision of parameter estimation. The validity of the assumption of perfect mixing inside the chambers and negligible film diffusion resistance was confirmed by a blank chamber test and by comparison of the responses obtained using the possible maximum and minimum film diffusion resistances respectively. The effective intrapellet diffusivities are determined by fitting the theoretical response of both chambers to the experimental values for a tracer gas stream. The dead-end pore volume can be evaluated from the results obtained using the steady and the transient responses. The effective convective coefficients were obtained from the top and bottom chamber inlet and outlet flow rates for a pure component stream keeping a given pressure difference across the pellet. For pellets with large average pore diameter, the experimental effective convective coefficients are independent of the average pressure. For pellets with small average pore diameter, the experimental apparent convective coefficients strongly depend on the average pressure. This dependence is expected since for small pores the contribution of non-convective fluxes to the total flux may become important. The intrapellet effective diffusivities and the effective convective coefficients were determined at 40, 70 and 95 degrees C for five single pellets of alumina based catalyst supports using helium as carrier gas and argon, oxygen and nitrogen as tracers.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10