THERMAL AND MASS DIFFUSIVITY FROM DYNAMIC SINGLE PELLET EXPERIMENTS

Date

1991-01-01

Author

DOGU, G
CABBAR, C
Doğu, Timur

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The single-pellet moment techniques previously developed for the evaluation of effective diffusion coefficient and effective thermal conductivity of a porous solid are combined and a procedure is proposed for the simultaneous evaluation of these constants from a single set of pulse response experiments. It is shown that both temperature and concentration response curves can be measured from a single pulse of oxygen injected into hydrogen carrier gas flowing past a catalyst pellet. It is shown that the zeroth moment of the concentration response peaks are sufficient for finding the effective diffusivity while both zeroth and first order moments are required for thermal conductivity. Experiments conducted at 110°C with a boehmite pellet of porosity 0.57 gave a thermal conductivity value of 3.6 x 10-4 cal/cm °K s and an effective diffusivity (for H2O) of 0.054 cm2/s. The adsorption equilibrium constant of H2O was determined as ρpK = 24.5 from the first moment data. If sorption resistance to diffusion through the pellet is included in the diffusion coefficient, an apparent value of 0.0011 cm2/s would be obtained for Deff . This result indicates the importance of separation of diffusion and sorption parameters in the analysis.

Subject Keywords

General Chemistry, General Chemical Engineering

URI

https://hdl.handle.net/11511/62826

Collections

Graduate School of Natural and Applied Sciences, Article