Hydration kinetics of lime

Hydration rate of calcium oxide has been investigated for a suspended single pellet into an atmosphere of air with a controlled humidity using a computer aided thermo-gravimetric technique. It has been found that the hydration reaction takes place on a sharp, well defined interface between the product layer and the unreacted core. A theoretical model for this reaction, that takes into account the sample swelling, was derived and employed to estimate the values for the rate constant and the effective diffusivity of the water vapor in the Ca(OH)₂ layer. These results suggest that gas mass transfer, pore diffusion and chemical reaction were all contributing resistances in the model. The calcination temperature and the water vapor partial pressure are the two most important variables that affect the hydration rate of lime. The higher the calcination temperature, the lower the hydration rate and the higher the water vapor partial pressure, the higher the hydration rate. The hydration temperature was found to play also a very important role in the phenomena involved.