Thermal conductivity and reactivity of Mg(OH)2 and MgO/expanded graphite composites with high packing density for chemical heat storage

Haruki, Masashi; Saito, Keita; Takai, Keita; Fujita, Masayuki; Onishi, Hajime; Tada, Yukio

doi:10.1016/j.tca.2019.178338

Cited by 18 publications

(8 citation statements)

References 33 publications

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“…16,17 Similar results were also observed with the addition of LiOOCCH 3 , NaNO 3 , 18 Ce(NO 3 ) 3 , 19 LiNO 3 , 20,21 and Ce(NO 3 ) 3 -LiOH. 11 Due to the high thermal conductivity of carbon materials, expanded graphite (EG) composites (EG-Mg(OH) 2 ), 22 Mg(OH) 2 -LiBr-EG, and Mg(OH) 2 -CaCl 2 -EG 23 exhibit higher thermal conductivity and heat-storage performance. Moreover, the dehydration temperature of Mg(OH) 2 can be reduced by 76 C using doped LiNO 3 20 and Ce(NO 3 ) 3 -LiOH.…”

Section: Mg Ohmentioning

confidence: 99%

Thermochemical energy storage drastically enhanced by zirconium oxide and lithium hydroxide for magnesium hydroxide

Ren

Wang

et al. 2021

Energy Storage

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Energy storage provides sustainable energy. Magnesium hydroxide (Mg(OH) 2 ) is a promising material for thermochemical energy storage. Zirconium oxynitrate (ZrO (NO 3 ) 2 ) and lithium hydroxide (LiOH) are investigated to improve the heat-storage efficiency of Mg(OH) 2 . Experimental results indicate that the heat-storage rate can be significantly increased by 306-fold. The dehydration conversion can be increased up to 99% with 122-fold increase in 15.3 min. The onset temperature of Mg(OH) 2 dehydration decreases from 337 to 228 C. The activation energy of Mg(OH) 2 dehydration significantly reduces by 57.7%. The cycle ability of heat storage and heat release also remarkably improves. Moreover, the heat-storage time significantly decreases. The crystal parameters, crystal volume, and platelet size of Mg(OH) 2 notably diminish. The acting mechanism of these additives is proposed using highresolution transmission electron microscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy data. Moreover, the kinetic equations for the dehydration of excellent Mg(OH) 2 composites are disclosed for computing simulation.

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Section: Mg Ohmentioning

confidence: 99%

Thermochemical energy storage drastically enhanced by zirconium oxide and lithium hydroxide for magnesium hydroxide

Ren

Wang

et al. 2021

Energy Storage

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“…TEG composites A self-built thermal-gravimetric (TG) apparatus that is similar to the apparatus reported in our previous work (Haruki et al, 2019) was used to measure the temporal change of the sample weight during hydration. A schematic diagram of the apparatus is shown in Figure 1.…”

Section: Measurements Of Hydration Behaviors Of β-La 2 (So 4 ) 3 /mentioning

confidence: 99%

“…erefore, β-La 2 (SO 4 ) 3 •xH 2 O will be mixed with materials that are known to have high levels of thermal conductivity. Carbon materials such as thermally expanded graphite (TEG) are some of the most widely investigated thermally conductive materials that are known to mix well with heat storage materials (Myagmarjav et al, 2015;Zamengo et al, 2016;Haruki et al, 2019). In our previous work, the thermal conductivities of pelletized La 2 (SO 4 ) 3 •9H 2 O/TEG and β-La 2 (SO 4 ) 3 •xH 2 O/TEG composites were mainly investigated for the e ects of the content of TEG, as well as for the density of the sample (Haruki et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Heat Release Behavior during Hydration Reaction of β-Lanthanum Sulfate/Thermally Expanded Graphite Composite for Use as Chemical Heat Storage Material

Haruki

Fujita

2021

J. Chem. Eng. Japan

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The present work investigates the hydration reaction of a composite made up of β-lanthanum sulfate and thermally expanded graphite for possible use as a chemical heat storage technique for exhaust heat below 250°C. The e ects that water concentration and hydration temperature exert on hydration behavior were mainly studied via the use of a disklike pelletized sample with a β-lanthanum sulfate content of 98 wt%. These e ects were experimentally investigated using a thermal-gravimetric apparatus. The maximum hydration rate increased as the water vapor concentration increased under a hydration temperature of 110°C. Moreover, the maximum heat power density was 2.1 MW/m 3 at a water vapor concentration of 17.5 mol/m 3 . Furthermore, the near-nal values of the hydration numbers that were found at 30 min decreased as the hydration temperature increased to a range of from 110 to 180°C. In the initial stage, however, hydration rates were not dependent on temperature under the present experimental conditions. The temperatures inside the pelletized samples during hydration were also measured. These temperatures drastically increased immediately after the start of hydration regardless of the beginning temperature. For instance, a maximum value of 195°C was obtained at a hydration temperature of 130°C with a water concentration of approximately 17.1 mol/m 3 .

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“…20 Haruki et al measured the effective thermal conductivities of pelletized magnesium hydroxide/expanded graphite (EG) and magnesium oxide/EG composite heat storage materials with high packing densities. 21 Mejia et al encapsulated CaO as a chemical heat storage material to address the low thermal conductivity and cohesiveness of the powder bulk material. This study showed that encapsulated materials were stable under operation in reactors.…”

Section: Introductionmentioning

confidence: 99%

Effect of Lithium Compound Addition on the Dehydration and Hydration of Calcium Hydroxide as a Chemical Heat Storage Material

2020

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Many studies on calcium hydroxide [Ca(OH)2] as a chemical heat storage material have been conducted. Generally, calcium hydroxide undergoes a dehydration reaction (heat storage operation) efficiently at about 400 °C or higher. In this study, we aimed to lower the dehydration reaction temperature and increase the dehydration reaction rate to expand the applicability of calcium hydroxide as a chemical heat storage material. For the purpose of improving the dehydration reactivity, calcium hydroxide with added lithium compounds was prepared, and the dehydration/hydration reactivities were evaluated. From the results, it was confirmed that the addition of the lithium compounds lowered the dehydration reaction temperature of calcium hydroxide and enhanced the reaction rate. The dehydration reaction of Ca(OH)2 with Li compounds proceeded efficiently even at 350 °C, and the reversibility of the dehydration/hydration reaction was confirmed. The reason for the improvement of the calcium hydroxide dehydration reactivity upon the addition of a lithium compound was examined from the viewpoint of its crystal structure. It was presumed that when lithium ions enter the calcium hydroxide crystals, the crystals became fragile and the dehydration reaction was accelerated.

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Thermal conductivity and reactivity of Mg(OH)2 and MgO/expanded graphite composites with high packing density for chemical heat storage

Cited by 18 publications

References 33 publications

Thermochemical energy storage drastically enhanced by zirconium oxide and lithium hydroxide for magnesium hydroxide

Thermochemical energy storage drastically enhanced by zirconium oxide and lithium hydroxide for magnesium hydroxide

Heat Release Behavior during Hydration Reaction of β-Lanthanum Sulfate/Thermally Expanded Graphite Composite for Use as Chemical Heat Storage Material

Effect of Lithium Compound Addition on the Dehydration and Hydration of Calcium Hydroxide as a Chemical Heat Storage Material

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