Chemical heat storage material and method for producing the same

Abstract

This chemical heat storage material contains a hydroxide and / or an oxide of an alkaline earth metal, wherein the total content of boron and fluorine as the content of the alkaline earth metal with respect to the hydroxide is 10-1,200 ppm (exclusive of 1,200). Said chemical heat storage material further contains an alkali metal compound, wherein the amount of the alkali metal compound is preferably 0.1-50 mol% with respect to the hydroxide and / or the oxide of the alkaline earth metal.

Description

Technical Field

[0001] The present invention relates to a chemical heat storage material and a method for manufacturing the same.

Background Art

[0002] In recent years, due to carbon dioxide emission regulations, it has been required to reduce the use of fossil fuels. In addition to energy conservation in each process, it is necessary to promote the utilization of waste heat. As a means of utilizing waste heat, hot water heat storage below 100 °C using water is known. However, hot water heat storage has the following problems: (1) heat dissipation loss makes long-term heat storage impossible, (2) a large amount of water is required because the sensible heat amount is small, and it is difficult to make the heat storage equipment compact, and (3) the output temperature is unsteady according to the usage amount and gradually decreases. Therefore, in order to promote the domestic use of such waste heat, it is necessary to develop a more efficient heat storage technology.

[0003] As a highly efficient heat storage technology, the chemical heat storage method can be mentioned. Since the chemical heat storage method involves chemical changes such as adsorption and hydration of substances, the heat storage amount per unit mass is higher than that of heat storage methods using the latent heat or sensible heat of the material itself (water, molten salt, etc.). As the chemical heat storage method, a water vapor adsorption / desorption method by adsorption / desorption of water vapor in the atmosphere, ammonia absorption into metal salts (ammine complex formation reaction), a reaction by adsorption / desorption of organic substances such as alcohol, etc. have been proposed. Considering the environmental load and the simplicity of the device, the water vapor adsorption / desorption method is the most advantageous. As the chemical heat storage material used in the water vapor adsorption / desorption method, calcium hydroxide and magnesium hydroxide, which are hydroxides of alkaline earth metals, are known.

[0004] However, these calcium hydroxide and magnesium hydroxide do not cause an effective dehydration reaction in the low temperature range of 100 to 400 °C, and thus have a problem that they do not function as a practical heat storage material.

[0005] To solve this problem, Patent Document 1 proposes a chemical heat storage material capable of storing heat at about 100 to 300°C by using a composite hydroxide of magnesium and at least one metal component selected from the group consisting of nickel, cobalt, copper, and aluminum.

[0006] Furthermore, Patent Document 2 proposes a chemical heat storage material obtained by adding a hygroscopic metal salt such as lithium chloride to a hydroxide of magnesium or calcium for the purpose of improving the heat storage amount of the chemical heat storage material described in Patent Document 1.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] According to the technologies disclosed in Patent Documents 1 and 2, although the heat storage operation temperature can be lowered to a certain extent, for example, when attempting to store factory waste heat, since the temperature range of factory waste heat is 200 to 250°C or a lower temperature range, the heat storage operation temperature is not sufficiently low, making it difficult to efficiently utilize factory waste heat, and there is a demand for further lowering the operation temperature. Furthermore, lowering the heat storage operation temperature also means improving the heat storage density and reaction efficiency. Expanding the applicable range for recovering factory exhaust heat and improving the economic efficiency of utilizing renewable energy remain important issues.

[0009] In view of the above situation, the present invention aims to provide a chemical heat storage material that performs heat storage using the dehydration reaction of an alkaline earth metal hydroxide, which exhibits a higher reaction rate and can achieve heat storage at a lower temperature, and a method for manufacturing the same.

Means for Solving the Problems

[0010] In order to solve the above problems, the inventors of the present invention have conducted various studies. As a result, in a chemical heat storage material using a dehydration reaction of a hydroxide of an alkaline earth metal, by setting the contents of boron and fluorine to be 10 ppm or more and less than 1200 ppm as the content with respect to the hydroxide of the alkaline earth metal, it has been found that a chemical heat storage material showing a higher reaction rate and capable of realizing heat storage at a lower temperature can be produced, and thus the present invention has been achieved.

[0011] That is, a first aspect of the present invention relates to a chemical heat storage material containing a hydroxide and / or oxide of an alkaline earth metal, wherein the contents of boron and fluorine are 10 ppm or more and less than 1200 ppm as the content with respect to the hydroxide of the alkaline earth metal. Preferably, the alkaline earth metal is at least one selected from the group consisting of calcium, magnesium, strontium, and barium. The chemical heat storage material may further contain a compound of an alkali metal, and the amount of the compound of the alkali metal may be 0.1 to 50 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. Preferably, the alkali metal is at least one selected from the group consisting of lithium, potassium, and sodium. The chemical heat storage material may further contain a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, and aluminum, and the amount of the metal may be 0.1 to 40 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. The chemical heat storage material may further contain a metal oxyacid salt, and the amount of the metal oxyacid salt may be 0.05 to 30 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. Preferably, the metal oxyacid salt is a metal oxyacid salt of at least one metal selected from the group consisting of alkali metals and alkaline earth metals. More preferably, the metal oxyacid salt of at least one metal selected from the group consisting of alkali metals and alkaline earth metals is a metal oxyacid salt of at least one metal selected from the group consisting of lithium, sodium, potassium, calcium, magnesium, strontium, and barium. Also preferably, the metal oxyacid salt is a metal oxyacid salt of at least one metal selected from the group consisting of aluminum, iron, cobalt, nickel, copper, and zinc.

[0012] The second invention is a method for producing a chemical heat storage material, which includes a step of preparing a chemical heat storage material containing a hydroxide and / or oxide of an alkaline earth metal, wherein the total content of boron and fluorine is 10 ppm or more and less than 1,200 ppm as the content with respect to the hydroxide of the alkaline earth metal, and relates to the method for producing the chemical heat storage material. The method may further include a step of mixing the hydroxide and / or oxide of the alkaline earth metal with a compound of an alkali metal, and the amount of the compound of the alkali metal may be 0.1 to 50 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. The method may further include a step of mixing the hydroxide and / or oxide of the alkaline earth metal with a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, and aluminum, and the amount of the metal may be 0.1 to 40 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. The method may further include a step of mixing the hydroxide and / or oxide of the alkaline earth metal with a metal oxyacid salt, and the amount of the metal oxyacid salt may be 0.05 to 30 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal.

Effects of the Invention

[0013] According to the present invention, there is provided a chemical heat storage material that performs heat storage using the dehydration reaction of an alkaline earth metal hydroxide, which exhibits a higher reaction rate and can achieve heat storage at a lower temperature, and a method for manufacturing the same.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail. The chemical heat storage material of the present invention utilizes the following reversible reactions of an alkaline earth metal hydroxide and oxide. In the following reaction formulas, the case where calcium or magnesium is used as the alkaline earth metal is shown. CaO + H2O ⇔ Ca(OH)2 △H = -109.2 kJ / mol MgO + H2O ⇔ Mg(OH)2 △H = -81.0 kJ / mol

[0015] In each formula, the reaction in the right direction is a hydration exothermic reaction of calcium oxide or magnesium oxide. Conversely, the reaction in the left direction is a dehydration endothermic reaction of calcium hydroxide or magnesium hydroxide. That is, the chemical heat storage material of the present invention can store heat by the progress of the dehydration reaction of calcium hydroxide or magnesium hydroxide, and can supply the stored thermal energy by the progress of the hydration reaction of calcium oxide or magnesium oxide.

[0016] The chemical heat storage material in the present invention may contain either a hydroxide of an alkaline earth metal or an oxide of an alkaline earth metal, or may contain both. Examples of the alkaline earth metal include calcium, magnesium, strontium, and barium. It may contain only one of these, or may contain a combination of two or more. Among these, calcium and / or magnesium is preferable, and magnesium is more preferable. As the hydroxide of the alkaline earth metal and the oxide of the alkaline earth metal, preferably, magnesium hydroxide, calcium hydroxide, a composite hydroxide of magnesium and calcium, magnesium oxide, calcium oxide, and a composite oxide of magnesium and calcium can be mentioned, and these may be used alone or in combination of two or more.

[0017] In the chemical heat storage material in the present invention, the total content of boron and fluorine is 10 ppm or more and 1,200 ppm or less with respect to the content of the hydroxide of the alkaline earth metal. Here, the content with respect to the hydroxide of the alkaline earth metal means that when the chemical heat storage material contains an oxide of the alkaline earth metal, the weight of the oxide is converted to the weight of the hydroxide, and the content with respect to the weight of the converted hydroxide. If the total content of boron and fluorine is less than or more than the above range, it becomes difficult to obtain the effect of showing a higher reaction rate and realizing heat storage at a lower temperature. The lower limit of the total content is preferably 20 ppm or more, more preferably 50 ppm or more, and further preferably 100 ppm or more. The upper limit of the total content is preferably 1,000 ppm or less, and more preferably 700 ppm or less.

[0018] Although it is not necessarily clear how boron and fluorine act on the hydration or dehydration reaction of the chemical heat storage material, it is considered that boron and fluorine are adsorbed or form insoluble salts on the hydroxide and / or oxide of the alkaline earth metal in the vicinity of the surface of the chemical heat storage material. By controlling this, it is presumed that it contributes to the improvement and stabilization of the cycle characteristics of the hydroxide and / or oxide of the alkaline earth metal, that is, the reactivity during the heat dehydration reaction and the hydration reaction by introducing steam.

[0019] The boron and / or fluorine contained in the chemical heat storage material may be contained as impurities in the hydroxide and / or oxide of the alkaline earth metal which is the raw material of the chemical heat storage material, or may be added to the hydroxide and / or oxide of the alkaline earth metal. The form of boron and / or fluorine at the time of addition may be a compound of an alkali metal, a compound of a specific metal, or an acid salt of a metal, which will be described later, or may be an inorganic acid.

[0020] The chemical heat storage material of the present invention may further contain a compound of an alkali metal in addition to the hydroxide and / or oxide of the alkaline earth metal. By further blending the compound of the alkali metal, the reaction rate of the chemical heat storage material can be further increased.

[0021] Examples of the alkali metal constituting the compound of the alkali metal include lithium, potassium, and sodium. It may contain only one of these, or may contain a combination of two or more. Among these, lithium and sodium are preferred, and lithium is more preferred. The compound of the alkali metal is not particularly limited as long as it exhibits the effects of the present invention, but a salt having hygroscopicity and capable of adsorbing moisture in the atmosphere or forming a corresponding hydrate is preferred. Examples of such salts include, for ease of handling, halides such as fluorides, chlorides, and bromides, hydroxides, borates, carbonates, acetates, nitrates, or sulfates. These may be used alone or in combination of two or more.

[0022] More specifically, as the lithium salt, lithium halide and / or lithium hydroxide are preferable, and lithium chloride, lithium bromide, and / or lithium hydroxide are more preferable. As the potassium salt, potassium halide and / or potassium hydroxide are preferable, and potassium chloride, potassium bromide, and / or potassium hydroxide are more preferable. As the sodium salt, sodium halide and / or sodium hydroxide are preferable, and sodium chloride, sodium bromide, and / or sodium hydroxide are more preferable.

[0023] When the amount of the alkali metal compound is such that the amount of the alkali metal compound is 0.1 to 50 mol% when the amount of the hydroxide and / or oxide of the alkaline earth metal is 100 mol%, it is preferable. If the amount of the alkali metal compound is less than the above range, it becomes difficult to achieve an improvement in the reaction rate or a decrease in the heat storage temperature by using the alkali metal compound. Further, if the amount of the alkali metal compound exceeds the above range, the heat storage amount per unit volume or unit mass of the chemical heat storage material may decrease. The amount of the alkali metal compound is preferably 0.5 to 30 mol%, more preferably 1.0 to 20 mol%, and even more preferably 2.0 to 10 mol%. By adjusting the amount of the alkali metal compound, the dehydration endothermic temperature of the chemical heat storage material can be controlled. However, when the alkali metal compound contains boron or fluorine, the alkali metal compound can be used within a range that satisfies the total content of boron and fluorine in the above-described chemical heat storage material.

[0024] The chemical heat storage material of the present invention may further contain a compound of a specific metal in addition to the hydroxide and / or oxide of the alkaline earth metal and the alkali metal compound which is an optional component. By further including the compound of the specific metal, the reaction rate of the chemical heat storage material can be further increased. At this time, the compound of the specific metal is preferably chemically complexed with the hydroxide and / or oxide of the alkaline earth metal.

[0025] The specific metal is selected from the group consisting of nickel, cobalt, copper, and aluminum, and may contain only one of these, or may contain a combination of two or more. Among these, at least one selected from the group consisting of nickel, cobalt, and aluminum is preferable, and nickel and / or cobalt is more preferable.

[0026] The compound of the specific metal is not particularly limited, but it is preferably one that forms a composite with a hydroxide and / or an oxide of an alkaline earth metal, and examples include halides such as fluorides, chlorides, and bromides, hydroxides, oxides, borates, carbonates, acetates, nitrates, or sulfates. These may be used alone or in combination of two or more. More specifically, nickel hydroxide, cobalt hydroxide, a composite hydroxide of nickel and cobalt, nickel oxide, cobalt oxide, and / or a composite oxide of nickel and cobalt are preferable.

[0027] The amount of the compound of the specific metal used is preferably such that when the amount of the hydroxide and / or oxide of the alkaline earth metal is 100 mol%, the amount of the specific metal is 0.1 to 40 mol%. When the amount of the specific metal is less than the above range, it becomes difficult to achieve an improvement in the reaction rate or a decrease in the heat storage temperature by using the compound of the specific metal. Also, when the amount of the specific metal is more than the above range, the heat storage amount per unit volume or unit mass of the chemical heat storage material may decrease. The amount of the specific metal is preferably 3 to 40 mol%, more preferably 5 to 30 mol%, and even more preferably 10 to 25 mol%. By adjusting the amount of the compound of the specific metal used, the dehydration endothermic temperature of the chemical heat storage material can be controlled. However, when the compound of the specific metal contains boron or fluorine, the compound of the specific metal can be used within a range that satisfies the total content of boron and fluorine in the chemical heat storage material described above.

[0028] The chemical heat storage material in the present invention may be simply physically mixed or dispersed with the hydroxide and / or oxide of an alkaline earth metal, and / or optionally with a compound of an alkali metal and / or optionally with a compound of a specific metal, but is not limited thereto. Part or all of each constituent component may be chemically compounded with each other, or part or all of each constituent component may chemically react with each other to form a third component.

[0029] In addition to the hydroxide and / or oxide of the alkaline earth metal, the optional compound of the alkali metal, and the optional compound of the specific metal, the chemical heat storage material of the present invention may further contain a metal acid salt. A metal acid salt refers to a salt formed by the reaction of a metal compound with an acid, and in particular, a salt formed by neutralizing a metal hydroxide with an acid is preferred. Specifically, for example, magnesium nitrate, magnesium acetate, magnesium benzoate, magnesium citrate, calcium nitrate, calcium acetate, calcium benzoate, calcium citrate, lithium nitrate, lithium acetate, lithium benzoate, lithium citrate, etc. may be mentioned, but are not limited thereto.

[0030] Examples of the metal constituting the metal acid salt include alkaline earth metals such as calcium, magnesium, strontium, and barium; alkali metals such as lithium, sodium, and potassium; and aluminum, iron, cobalt, nickel, copper, and zinc. It may contain only one of these, or may contain a combination of two or more. Among these, calcium, lithium, and / or magnesium are preferred, and calcium and / or magnesium are more preferred. The alkaline earth metal constituting the metal acid salt of the pre-metal may be the same as or different from the alkaline earth metal constituting the hydroxide and / or oxide of the alkaline earth metal, but from the viewpoint of improving the reaction rate of the chemical heat storage material, it is preferably the same. However, when the metal acid salt used in the present invention is an alkaline earth metal acid salt, it is preferable not to use carbonate and chloride of the alkaline earth metal as the alkaline earth metal acid salt.

[0031] The acid constituting the metal oxyacid is not particularly limited, and known acids can be appropriately used, and either inorganic acids or organic acids may be used. Further, it may be a water-soluble acid, or an acid poorly soluble or insoluble in water. Further, only one type may be used, or two or more types may be appropriately combined and used.

[0032] Examples of the inorganic acid include hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, boric acid, sulfuric acid, nitric acid, phosphoric acid, phosphonic acid, sulfonic acid, hydrocyanic acid, and the like.

[0033] Examples of the organic acid include organic sulfonic acids, organic phosphonic acids, aliphatic hydroxy acids (including dihydroxy acids and trihydroxy acids), aromatic hydroxy acids (including dihydroxy acids and trihydroxy acids), aliphatic carboxylic acids (including dicarboxylic acids and tricarboxylic acids), aliphatic unsaturated carboxylic acids (including dicarboxylic acids and tricarboxylic acids), aromatic carboxylic acids (including dicarboxylic acids and tricarboxylic acids), aromatic unsaturated carboxylic acids (including dicarboxylic acids and tricarboxylic acids), other oxyacids, other oxocarboxylic acids, amino acids, and acids of these derivatives.

[0034] Examples of the organic sulfonic acid include methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and the like. Examples of the organic phosphonic acid include dimethyl phosphate, phenylphosphonic acid, and the like. Examples of the aliphatic hydroxy acid or aromatic hydroxy acid include lactic acid, malic acid, citric acid, tartaric acid, and the like. Examples of the aliphatic carboxylic acid or aliphatic unsaturated carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, acrylic acid, sorbic acid, pyruvic acid, oxaloacetic acid, squaric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, aconitic acid, and the like. Examples of the aromatic carboxylic acid or aromatic unsaturated carboxylic acid include benzoic acid, phthalic acid, salicylic acid, shikimic acid, gallic acid, pyromellitic acid, and the like. Examples of the amino acid include aspartic acid, glutamic acid, and the like.

[0035] As the amount of the metal oxyacid salt used, when the amount of the hydroxide and / or oxide of the alkaline earth metal is 100 mol%, it is preferably an amount such that the amount of the metal oxyacid salt is 0.05 to 30 mol%. When the amount of the metal oxyacid salt used is less than the above range, it becomes difficult to achieve an improvement in the reaction rate or a lowering of the heat storage temperature by the addition of the oxyacid salt. Further, when the amount of the metal oxyacid salt used is more than the above range, the influence on the hydroxide and / or oxide of the alkaline earth metal as the base material is large, and the heat storage amount per unit volume or unit mass of the chemical heat storage material may decrease. The amount of the metal oxyacid salt used is preferably 0.1 to 20 mol%, more preferably 0.3 to 15 mol%, still more preferably 0.5 to 10 mol%, even more preferably 0.8 to 8 mol%, and particularly preferably 1 to 6%. However, when the metal oxyacid salt contains boron or fluorine, the metal oxyacid salt can be used within a range that satisfies the total content of boron and fluorine in the chemical heat storage material described above.

[0036] The chemical heat storage material of the present invention is a chemical heat storage material that utilizes an endothermic dehydration reaction and a hydration exothermic reaction of a hydroxide of an alkaline earth metal and an oxide of an alkaline earth metal. In that range, the chemical heat storage material of the present invention may contain other components, and may contain chemical heat storage components other than the constituent components described above, or components that do not exhibit a chemical heat storage effect (for example, a binder). However, when these other components contain boron or fluorine, the other components can be used within a range that satisfies the total content of boron and fluorine in the chemical heat storage material described above.

[0037] The shape of the chemical heat storage material of the present invention is not particularly limited, and for example, it may be in the form of powder, granulated material, molded body, etc. When manufacturing a chemical heat storage material having a powder, granulated material, or molded body shape, known methods can be applied. For example, when manufacturing a powder chemical heat storage material, screening, crushing, and pulverizing processes can be applied. Also, when manufacturing a granulated chemical heat storage material, granulation processes such as extrusion granulation, rolling granulation, fluidized bed granulation, and spray drying can be applied. When manufacturing a molded chemical heat storage material, molding processes such as press molding, injection molding, blow molding, vacuum molding, and extrusion molding can be applied. That is, as long as the properties as a chemical heat storage material are not impaired to an extent that can be implemented, it is possible to select an arbitrary shape according to the implementation form of the consumer.

[0038] Next, a method for manufacturing the chemical heat storage material in the present invention will be described. The method for manufacturing the chemical heat storage material in the present invention is not particularly limited, but preferably includes at least a step of preparing a chemical heat storage material containing an alkaline earth metal hydroxide and / or oxide, wherein the total content of boron and fluorine is 10 ppm or more and less than 1,200 ppm as the content relative to the alkaline earth metal hydroxide.

[0039] The alkaline earth metal hydroxide and / or oxide of the raw material used when preparing the chemical heat storage material may be a high-purity product with a purity of 99.9% by weight or more, or may be, for example, a relatively low-purity product with a purity of 95% by weight or more and less than 99.9% by weight. As the raw material, seawater-processed magnesia, calcined magnesia from natural ore, fused magnesia, etc. can be used as industrial magnesium sources.

[0040] When the hydroxide and / or oxide of the alkaline earth metal in the raw material contains more boron and fluorine than the range of the total content, it is preferable to carry out an operation of reducing boron and / or fluorine by an appropriate purification treatment. Further, the chemical heat storage material of the present invention can also be produced by adding a component containing boron and / or fluorine to the hydroxide and / or oxide of the alkaline earth metal in the raw material within a range that satisfies the total content.

[0041] An example of a method for producing a chemical heat storage material containing the compound of the alkali metal, the compound of the specific metal, and / or the metal oxyacid salt will be described. First, the compound of the alkali metal is dissolved in ion-exchanged water to prepare an aqueous solution of the compound of the alkali metal, and the powder of the hydroxide of the alkaline earth metal is added thereto and stirred and mixed. Here, the compound of the specific metal or the metal oxyacid salt may be added together. The obtained slurry is dried, and a chemical heat storage material can be produced as a dry powder. The method of stirring and mixing is not particularly limited as long as the ion-exchanged water as the solvent and the powder of the hydroxide of the alkaline earth metal are sufficiently mixed.

[0042] The order of adding each component may be changed. In this case, for example, first, the compound of the alkali metal, or the compound of the alkali metal and the compound of the specific metal are dissolved in ion-exchanged water, the metal oxyacid salt is added thereto, and then the powder of the hydroxide of the alkaline earth metal is added to prepare a slurry, which is subsequently dried to produce a chemical heat storage material.

[0043] The chemical heat storage material of the present invention can store heat by absorbing heat from a heat source of about 100 to 400 °C, such as unused heat from factory exhaust heat, etc., and dehydrating. The dehydrated chemical heat storage material can be easily maintained in a heat storage state by keeping it in a dry state, and can be carried to a desired place while maintaining the heat storage state. When releasing heat, the heat of hydration reaction (in some cases, the heat of water vapor sorption) can be taken out as thermal energy by contacting with water, preferably water vapor. Further, cold thermal energy can also be generated by causing water vapor sorption on one side in a hermetically sealed space and evaporating water on the other side.

[0044] In addition, the chemical heat storage material of the present invention is also suitable for effectively utilizing the heat of exhaust gas discharged from engines, fuel cells, etc. For example, the heat of exhaust gas can be utilized for shortening the warm-up operation of automobiles, improving the amenity of passengers, improving fuel efficiency, and reducing the harmfulness of exhaust gas by improving the activity of the exhaust gas catalyst. In particular, in an engine, since the load due to operation is not constant and the exhaust output is also unstable, the direct utilization of exhaust heat from the engine is inevitably inefficient and inconvenient. By using the chemical heat storage material of the present invention, the exhaust heat from the engine can be chemically stored once and then heat output according to the heat demand, enabling more ideal utilization of exhaust heat.

Examples

[0045] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0046] (Evaluation method) For the chemical heat storage materials obtained in each example and comparative example, thermal evaluation was performed using a differential thermal - thermogravimetric simultaneous measurement device (DTG - 60, manufactured by Shimadzu Corporation). Specifically, at a heating rate of 10 °C / min., under atmospheric conditions and normal pressure, a sample of the chemical heat storage material added with a compound of an alkali metal was heated to 300 °C, and a sample of the chemical heat storage material without the addition of a compound of an alkali metal was heated to 350 °C. Then, the temperature was kept constant, and the weight loss amount was measured over time. Based on the obtained weight loss value, the reaction rate was calculated as the ratio of the change of magnesium hydroxide in each chemical heat storage material to magnesium oxide.

[0047] To calculate the reaction rate, in order to exclude the influence of volatile components, etc., the weight of the chemical heat storage material at the time when the temperature was raised to 200 °C was set as the starting weight and the reaction rate was set to 0%. Assuming that all magnesium hydroxide had changed to magnesium oxide, the weight loss value was determined as the reaction rate of 100% and the calculation was carried out.

[0048] The performance evaluation of the chemical heat storage material was carried out based on the reaction rate calculated from the weight loss value at the time when 2000 seconds had elapsed after setting the time when the sample temperature reached 200°C as 0 seconds. The higher the reaction rate, the faster the endothermic dehydration reaction proceeds, indicating a larger heat storage capacity and the ability to store heat with lower-temperature heat. Note that the numbers of relative reaction rates in the table indicate relative values when the reaction rate of each comparative example is set as 100 of the reference, rather than absolute values.

[0049] Magnesium hydroxide used in this example and comparative examples was manufactured by the inventors. The purity of magnesium hydroxide was calculated by measuring the content of each impurity with a multi-element simultaneous X-ray fluorescence analyzer (Simultix12, manufactured by Rigaku Corporation), and subtracting the sum of the contents of oxides of Ca, Si, Al, Fe, P, S, which are the main impurities, and the Cl content from 100%. The boron content was measured using an ICP emission spectroscopic analyzer (trade name "PS3520 VDD", manufactured by Hitachi High-Technologies Corporation) after completely dissolving the sample. The fluorine content was measured by the ion electrode method (apparatus name: Ion Meter D-53S, manufactured by Horiba, Ltd.) for the amount of fluorine in the solution prepared by dissolving the sample in hydrochloric acid. The BET specific surface area was measured by the gas adsorption method (BET method) using nitrogen gas with a specific surface area measuring device (Macsorb, manufactured by Mountech Co., Ltd.). The volume average particle diameter was measured using a laser diffraction scattering type particle size distribution measuring device (MT3300, manufactured by Nikkiso Co., Ltd.).

[0050] (Example 1) 5 g of magnesium hydroxide (purity of about 99%, BET specific surface area of 40 m 2 / g, volume average particle diameter of 4.2 μm) was weighed, and further, boric acid (Kanto Chemical Reagent, special grade) with a boron content of 440 ppm with respect to the magnesium hydroxide was weighed, and further, magnesium fluoride (Kanto Chemical Reagent, special grade) with a fluorine content of 10 ppm with respect to the magnesium hydroxide was weighed. The weighed boric acid and magnesium fluoride were completely dissolved in 50 mL of ion-exchanged water to obtain an aqueous solution. To this aqueous solution, the magnesium hydroxide weighed above was added, and the mixture was stirred with a magnetic stirrer at a rotation speed of 200 (rpm) for 300 seconds to prepare a slurry. The slurry was dried at 110 °C for 12 hours or more using a dryer (DRA430DA manufactured by Advantech Co., Ltd.) to remove moisture, thereby producing a chemical heat storage material. For the obtained chemical heat storage material, the heat behavior was confirmed by the above evaluation method, and the reaction rate was calculated.

[0051] (Example 2) A chemical heat storage material was produced in the same manner as in Example 1 except that boric acid was used so that the boron content was 660 ppm, and the reaction rate was calculated in the same manner.

[0052] (Example 3) A chemical heat storage material was produced in the same manner as in Example 1 except that boric acid and magnesium fluoride were used so that the boron content was 440 ppm and the fluorine content was 220 ppm, and the reaction rate was calculated in the same manner.

[0053] (Comparative Example 1) A chemical heat storage material was produced in the same manner as in Example 1 except that boric acid and magnesium fluoride were used so that the boron content was 1030 ppm and the fluorine content was 800 ppm, and the reaction rate was calculated in the same manner.

[0054] (Example 4) 5 g of magnesium hydroxide (the same as in Example 1) was weighed, and further, lithium chloride monohydrate (Kanto Chemical Reagent, special grade, purity 98.0%) in an amount of 10 mol% with respect to the magnesium hydroxide was weighed. Further, boric acid (Kanto Chemical Reagent, special grade) in an amount such that the boron content with respect to the magnesium hydroxide was 400 ppm was weighed. Further, magnesium fluoride (Kanto Chemical Reagent, special grade) in an amount such that the fluorine content with respect to the magnesium hydroxide was 10 ppm was weighed. The weighed lithium chloride monohydrate was completely dissolved in 50 mL of ion-exchanged water to obtain an aqueous solution. To this aqueous solution, magnesium hydroxide, boric acid, and magnesium fluoride weighed as described above were added, and the mixture was stirred with a magnetic stirrer at 200 rpm for 300 seconds to prepare a slurry. The slurry was dried at 110 °C for 12 hours or more using a dryer (DRA430DA manufactured by Advantech Co., Ltd.) to remove moisture, thereby producing a chemical heat storage material. For the obtained chemical heat storage material, the heat behavior was confirmed by the above evaluation method, and the reaction rate was calculated.

[0055] (Example 5) A chemical heat storage material was produced in the same manner as in Example 4 except that boric acid was used so that the boron content was 600 ppm, and the reaction rate was calculated in the same manner.

[0056] (Example 6) A chemical heat storage material was produced in the same manner as in Example 4 except that boric acid and magnesium fluoride were used so that the boron content was 440 ppm and the fluorine content was 200 ppm, and the reaction rate was calculated in the same manner.

[0057] (Example 7) A chemical heat storage material was produced in the same manner as in Example 4 except that boric acid and magnesium fluoride were used so that the boron content was 1030 ppm and the fluorine content was 10 ppm, and the reaction rate was calculated in the same manner.

[0058] (Comparative Example 2) A chemical heat storage material was produced in the same manner as in Example 4 except that boric acid and magnesium fluoride were used so that the boron content was 1060 ppm and the fluorine content was 800 ppm, and the reaction rate was calculated in the same manner.

[0059] The results are shown in Table 1 and Table 2. In Table 1, taking the reaction rate of the chemical heat storage material obtained in Comparative Example 1 as 100 as a reference, the numbers obtained by converting the reaction rates obtained in each Example into relative reaction rates are shown. In Table 2, taking the reaction rate of the chemical heat storage material obtained in Comparative Example 2 as 100 as a reference, the numbers obtained by converting the reaction rates obtained in each Example into relative reaction rates are shown.

[0060]

Table 1

[0061]

Table 2

[0062] From Table 1, it can be confirmed that the chemical heat storage materials of Examples 1 to 3, in which the total content of boron and fluorine is in the range of 10 ppm or more and less than 1,200 ppm, under the same evaluation conditions as Comparative Example 1, the endothermic dehydration reaction proceeds more rapidly compared to Comparative Example 1. From this, it can be seen that the chemical heat storage materials of Examples 1 to 3 have a larger heat storage capacity than the chemical heat storage material of Comparative Example 1, and can store heat even with lower-temperature heat.

[0063] From Table 2, it can be confirmed that the chemical heat storage materials of Examples 4 to 7, in which 10 mol% of lithium chloride is added to magnesium hydroxide and the total content of boron and fluorine is in the range of 10 ppm or more and less than 1,200 ppm, under the same evaluation conditions as Comparative Example 2, the endothermic dehydration reaction proceeds more rapidly compared to Comparative Example 2. From this, it can be seen that the chemical heat storage materials of Examples 4 to 7 have a larger heat storage capacity than the chemical heat storage material of Comparative Example 2, and can store heat even with lower-temperature heat.

Claims

1. A chemical heat storage material containing a hydroxide and / or an oxide of an alkaline earth metal, containing both boron and fluorine, each of boron and fluorine is added in at least one form selected from the group consisting of a compound of an alkali metal, a compound of a specific metal, a metal oxyacid salt, and an inorganic acid, the specific metal is at least one selected from the group consisting of nickel, cobalt, copper, and aluminum, the total content of boron and fluorine is 100 ppm or more and less than 1,200 ppm based on the content of the hydroxide of the alkaline earth metal, the content with respect to the hydroxide of the alkaline earth metal is the content with respect to the weight of the hydroxide after conversion, when the chemical heat storage material contains an oxide of the alkaline earth metal, by converting the weight of the oxide to the weight of the hydroxide. Chemical heat storage material.

2. The chemical heat storage material according to claim 1, wherein the alkaline earth metal is at least one selected from the group consisting of calcium, magnesium, strontium, and barium.

3. further containing a compound of an alkali metal, the amount of the compound of the alkali metal is 0.1 to 50 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. The chemical heat storage material according to claim 1 or 2.

4. The chemical heat storage material according to claim 3, wherein the alkali metal is at least one selected from the group consisting of lithium, potassium, and sodium.

5. further containing a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, and aluminum, the amount of the metal constituting the compound of the metal is 0.1 to 40 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. The chemical heat storage material according to any one of claims 1 to 4.

6. further containing a metal oxyacid salt, the amount of the metal oxyacid salt is 0.05 to 30 mol% with respect to the hydroxide and / or oxide of the alkaline earth metal. The chemical heat storage material according to any one of claims 1 to 5.

7. The chemical heat storage material according to claim 6, wherein the metal oxyacid salt is a metal oxyacid salt of at least one metal selected from the group consisting of an alkali metal and an alkaline earth metal.

8. The chemical heat storage material according to claim 7, wherein the acid salt of at least one metal selected from the group consisting of the alkali metals and alkaline earth metals is an acid salt of at least one metal selected from the group consisting of lithium, sodium, potassium, calcium, magnesium, strontium, and barium.

9. The chemical heat storage material according to claim 6, wherein the acid salt of the metal is an acid salt of at least one metal selected from the group consisting of aluminum, iron, cobalt, nickel, copper, and zinc.

10. A method for manufacturing a chemical heat storage material, comprising a step of preparing a chemical heat storage material containing a hydroxide and / or oxide of an alkaline earth metal, wherein the total content of boron and fluorine is 100 ppm or more and less than 1,200 ppm based on the content of the hydroxide of the alkaline earth metal, the method for manufacturing a chemical heat storage material according to any one of claims 1 to 9.

11. further comprising a step of mixing a hydroxide and / or oxide of an alkaline earth metal with a compound of an alkali metal, wherein the amount of the compound of the alkali metal is 0.1 to 50 mol% based on the hydroxide and / or oxide of the alkaline earth metal, the method according to claim 10.

12. further comprising a step of mixing a hydroxide and / or oxide of an alkaline earth metal with a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, and aluminum, wherein the amount of the metal constituting the compound of the metal is 0.1 to 40 mol% based on the hydroxide and / or oxide of the alkaline earth metal, the method according to claim 10 or 11.

13. further comprising a step of mixing a hydroxide and / or oxide of an alkaline earth metal with an acid salt of a metal, wherein the amount of the acid salt of the metal is 0.05 to 30 mol% based on the hydroxide and / or oxide of the alkaline earth metal, the method according to any one of claims 10 to 12.

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