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Keywords:

  • solid-solid reactions;
  • contact points;
  • Hao-Tanaka model

Abstract

The contact-point framework,1 which replaces the picture of continuous contact between the reactants by contact at a finite number of points, has been proposed as a rational one for treating reactions among particulate solids. However, available models suffer from various drawbacks, the main one being that they do not show the right asymptotic behavior for large number of contact points. A model is presented here, that corrects these deficiencies. The results show that the contact-point model approaches particle-continuum behavior whenever the number of contact points exceeds 500. The model predictions have been compared with some data from our previous work on calcia-alumina system in the temperature range 1,150–1,300°C. The model fits the data well, with the fitted values of diffusivity (of calcia through alumina) being of the order of 10−16 m2/s. © 2010 American Institute of Chemical Engineers AIChE J, 2010