Dehydration reactivity of Mg(OH)2 containing low amounts of Li-additives for thermochemical energy storage

• Published in: ISIJ International 2022, pp.ISIJINT-2022-082
• Main Authors: Kobayashi, Naoki, Kurosawa, Ryo, Ryu, Junichi
• Format: Article
• Language: English
• Subjects: chemical heat storage; lithium compound addition; magnesium hydroxide
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2022-082

Mg(OH)2 is a chemical heat storage material suitable for the utilization of unused heat at 300–400 °C. It has been reported that the addition of Li compounds to Mg(OH)2 promotes the dehydration of Mg(OH)2. However, the demand for Li compounds has increased in recent years and the price of Li compounds is relatively high. Therefore, the purpose of this study is to enhance the dehydration reactivity of Mg(OH)2 with a small amount of Li. In this study, several alkali metal chlorides and hydroxides such as LiCl and NaOH or KOH were added to Mg(OH)2, and the dehydration reactivity and composition of the corresponding mixtures were investigated. The samples prepared using 5 mol% LiCl and 10 mol% NaOH (LiCl-5NaOH-10) or 2.5 mol% KOH (LiCl-5KOH-2.5) showed excellent dehydration reactivity and were dehydrated below 300 °C with comparatively lower amounts of Li compounds than those reported in previous studies. These results indicate that these samples have great potential as low-cost chemical heat storage materials. However, the stabilities of these samples in air are quite different. Based on X-ray diffraction analysis of the data, the results are associated with the composition of Cl-, OH-, Li+, Na+, and K+.