Dehydration and Hydration Behavior of Mg–Co Mixed Hydroxide as a Material for Chemical Heat Storage

Abstract

The dehydration and hydration behaviors of Mg–Co mixed hydroxides and the effect of LiCl addition were studied to develop a new material for chemical heat storage. The formation of the mixed hydroxides and LiCl addition were expected to reduce the dehydration temperature of authentic magnesium hydroxide; this temperature corresponds to that of heat-storage operation. That the dehydration temperature of Mg–Co mixed hydroxides was found to be approximately 280°C, which was lower than that of authentic magnesium hydroxide. The mixed hydroxides showed higher hydration reactivities than authentic magnesium oxide at 110°C with 57.8 kPa of water vapor after dehydration at 300°C. The dehydration temperatures of Mg–Co mixed hydroxides were lowered by LiCl addition. LiCl-added Mg–Co mixed hydroxides showed higher hydration reactivities than the usual Mg–Co mixed oxides after dehydration at 250°C. The heat-output performance of LiCl/Mg_0.95Co_0.05(OH)₂ was estimated as 715 kJ kg⁻¹ after dehydration at 250°C. These results indicated that Mg–Co mixed hydroxides can be used to utilize industrial waste heat between 250°C and 300°C.