Reaction Performance of Calcium Hydroxide and Expanded Graphite Composites for Chemical Heat Storage Applications

New composite materials were developed for application in chemical heat storage (CHS) systems based on the calcium oxide/water/calcium hydroxide (CaO/H2O/Ca(OH)(2)) reaction. It was found that the mixtures of expanded graphite (EG) and Ca(OH)(2) enhance the reaction performance and moldability, which are important factors for the application in a packed-bed CHS heat exchanger. The reaction kinetics was investigated by thermogravimetric analysis. The maximum mean heat output of a mixture containing 11 wt% EG was 1.76 kW (kg-material)(-1), which is twice as high as that of the pure Ca(OH)(2) (0.85 kW (kg-material)(-1)). A repetitive dehydration-hydration experiment was carried out and it was confirmed that the positive effect of EG was preserved during the investigated 10 cycles. Therefore, based on our results, these composite materials can enhance the thermal performance of the CaO/H2O/Ca(OH)(2) reaction cycle in CHS systems.