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A variable diffusivity shrinking‐core model and its application to the direct sulfation of limestone
Author(s) -
Krishnan S. V.,
Sotirchos Stratis V.
Publication year - 1993
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450710511
Subject(s) - thermal diffusivity , calcination , mineralogy , chemistry , thermodynamics , materials science , physics , biochemistry , catalysis
A variable diffusivity shrinking‐core model that allows for temporal and spatial variation of the effective diffusivity in the solid product layer was developed in this study. The model was used to analyze a set of experimental data for the direct sulfation of three limestones (that is, their reaction with SO2 under noncalcining conditions), and a parameter estimation procedure was formulated for extracting the effective diffusivity as a distributed parameter from the experimental conversion vs. time curves. Very strong effects of temperature, concentration, and depth in the product layer on the effective diffusivity were revealed by the analysis. On the basis of the obtained results, it was concluded that despite being essentially nonporous, uncalcined limestones can react with SO, under noncalcining conditions at rates comparable to those of calcined samples because they present much lower resistance for diffusion of SO2 through the product layer than the latter.