Abstract:

The Ca(OH)2/CaO system is a very promising thermochemical energy storage medium, and its kinetic research provides an important way ofto understanding  the reaction and energy storage/release rates of the whole energy storage system. In this paper, a thermogravimetric analysis iswas  conducted to investigate the thermal decomposition processes of Ca(OH)2 samples in pure N2 atmosphere at different heating rates. The results show that during the thermal decomposition of Ca(OH)2 samples, two weight loss processes occur at 623.15~773.15 K and 873.15~973.15 K, and the weight loss rates are close to 21% and 2%, respectively. The kinetic analysis of the thermal decomposition process through the multiple scanning indicates that the obtained apparent kinetic parameters depend on the reaction conversion rate, the heating rate and the selected model approach. Through the most probable mechanism function analysis, it is also found that the thermal decomposition kinetics model of Ca(OH)2 under experimental conditions accords well with the shrinking cylinder mechanism with surface reaction rate controlling. Besides, there exists a linear relationship between the activation energy E and the natural logarithm of the pre-exponential factor A at different heating rates.

Key words: calcium hydroxide, thermal analysis, multiple scanning method, reaction kinetics, mechanism function