Hydroxylation kinetics in lime clinkers

Abstract

In the manufacture of lime and lime-containing refractories the kinetics of the hydroxylation reaction CaO + H20 --~ Ca(OH)2 -or as it is not quite accurately called, hydration -plays an important role in determining the preservation conditions and subsequent use of the materials. This applies especially to clinkers formulated for making sintered refractories (with a ceramic bond). This article examines the influence of TiO 2 impurity on the hydroxylation of CaO and the evaluation of this process.Kinetie Models of Hydroxylation. The degree of hydroxylation ~ can be assessed from the volume proportion of CaO reacting with water [calculated as Ca(OH)2]: c~ = (V 0 -V)/V o, where V 0 is the volume of CaO particles with an initial radius Ro; V is the volume of particles of unreacted CaO with average size R. If the hydroxylation mechanism is defined as the diffusion of water through a layer of Ca(OH) 2 and the surface of the CaO particles, then the rate of increase in the thickness of the layer of Ca(OH) 2 is inversely proportional to it: