Chemical heat storage material, and production method of the same

Abstract

To provide a chemical heat storage material capable of realizing heat storage at a low temperature while reducing a used amount of a lithium compound in a chemical heat storage material for storing heat utilizing dehydration reaction of a hydroxide of calcium and / or magnesium.SOLUTION: A chemical heat storage material includes: a hydroxide and / or oxide of calcium and / or magnesium; a hydroxide of sodium and / or potassium; and a chloride of lithium, where the total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol% to the hydroxide and / or oxide of calcium and / or magnesium.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a chemical heat storage material and a manufacturing method thereof. [Background technology]

[0002] In recent years, carbon dioxide emission regulations have required a reduction in the use of fossil fuels, and in addition to energy conservation in each process, it is necessary to promote the use of waste heat. Hot water thermal storage of water at temperatures below 100°C is known as a means of utilizing waste heat. However, there are problems with hot water thermal storage, such as (1) the inability to store heat for long periods of time due to heat dissipation losses, (2) the small amount of sensible heat requires a large amount of water, making it difficult to compact the thermal storage equipment, and (3) the output temperature is non-steady and gradually drops depending on the amount of use. Therefore, in order to promote the use of such waste heat in civilian applications, it is necessary to develop more efficient thermal storage technology.

[0003] Chemical heat storage is an example of a highly efficient heat storage technology. Because chemical heat storage involves chemical changes such as the adsorption and hydration of substances, it can store a higher amount of heat per unit mass than heat storage methods that use the latent heat or sensible heat of the material itself (water, molten salt, etc.). Proposed chemical heat storage methods include the water vapor adsorption / desorption method, which uses the adsorption and desorption of water vapor in the atmosphere, the absorption of ammonia into metal salts (ammine complex formation reaction), and reactions that use the adsorption and desorption of organic substances such as alcohol. Considering the burden on the environment and the simplicity of the equipment, the water vapor adsorption / desorption method is the most advantageous. Calcium hydroxide and magnesium hydroxide are known as chemical heat storage materials used in the water vapor adsorption / desorption method.

[0004] However, calcium hydroxide does not undergo an effective dehydration reaction at low temperatures of 100 to 400°C, and magnesium hydroxide does not undergo an effective dehydration reaction at low temperatures of 100 to 300°C, so there was a problem that they did not function as practical heat storage materials.

[0005] In order to solve this problem, Patent Document 1 proposes a chemical heat storage material capable of storing heat at approximately 100 to 300°C by utilizing 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 in which a hygroscopic metal salt such as lithium chloride is added to a hydroxide of magnesium or calcium in order to improve the heat storage capacity of the chemical heat storage material described in Patent Document 1.

[0007] According to the techniques disclosed in Patent Documents 1 and 2, the heat storage operating temperature can be lowered to some extent, but when trying to store factory waste heat, for example, the temperature range of the factory waste heat is 200 to 250°C or lower, so the heat storage operating temperature is not low enough, making it difficult to efficiently use the factory waste heat, and there is a demand for further lowering the operating temperature. From the standpoint of improving heat storage efficiency and expanding the applicable temperature range of the heat storage system, improving the operating temperature of the chemical heat storage material remains an important issue.

[0008] In response to this problem, Patent Document 3 proposes a chemical heat storage material in which lithium chloride and lithium hydroxide are added to a hydroxide of calcium and / or magnesium. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2007-309561 A [Patent Document 2] JP 2009-186119 A [Patent Document 3] International Publication No. 2019 / 159791 Summary of the Invention [Problem to be solved by the invention]

[0010] In Patent Document 3, lithium hydroxide and lithium chloride, which are lithium compounds, are used to realize heat storage at low temperatures, but because lithium compounds are highly corrosive, using a large amount of lithium compounds may damage the device. In addition, the price of lithium compounds has risen sharply in response to the increase in demand in recent years, and using a large amount of lithium compounds results in high costs. For this reason, a chemical heat storage material that can realize heat storage at low temperatures while reducing the amount of lithium compound used may be required, but such a chemical heat storage material has not been sufficiently studied so far.

[0011] Therefore, the present invention aims to provide a chemical heat storage material that stores heat by utilizing the dehydration reaction of calcium and / or magnesium hydroxide, and that can realize heat storage at low temperatures while reducing the amount of lithium compound used, and a manufacturing method thereof. [Means for solving the problem]

[0012] In order to solve the above problems, the inventors conducted extensive research and discovered that, in a chemical heat storage material containing hydroxide and / or oxide of calcium and / or magnesium, a composition in which hydroxide and / or oxide of calcium and / or magnesium is co-added with hydroxide of sodium and / or potassium and chloride of lithium can be used as a chemical heat storage material while reducing the amount of lithium compound used, and thus the present invention was completed.

[0013] That is, the first invention is a composition comprising a hydroxide and / or oxide of calcium and / or magnesium, a hydroxide of sodium and / or potassium, and a chloride of lithium, The chemical heat storage material relates to the above-mentioned compound, wherein the total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol % relative to the hydroxide and / or oxide of calcium and / or magnesium.

[0014] The second aspect of the present invention is a method for producing a chemical heat storage material, mixing hydroxides and / or oxides of calcium and / or magnesium, hydroxides of sodium and / or potassium, and chloride of lithium; The total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol % based on the hydroxide and / or oxide of calcium and / or magnesium. Effect of the Invention

[0015] According to the present invention, in a chemical heat storage material that stores heat by utilizing a dehydration reaction of calcium and / or magnesium hydroxide, it is possible to provide a chemical heat storage material that can realize heat storage at low temperatures while reducing the amount of lithium compound used, and a manufacturing method thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described in detail. The chemical heat storage material produced in the present invention utilizes a reversible reaction represented by the following reaction formula by hydroxide and oxide of calcium and / or magnesium. CaO+H2O⇔Ca(OH)2△H=-109.2kJ / mol MgO+H2O⇔Mg(OH)2△H=-81.2kJ / mol

[0017] In each formula, the reaction to the right is an exothermic hydration reaction of calcium oxide or magnesium oxide. Conversely, the reaction to the left is an endothermic dehydration 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.

[0018] The chemical heat storage material in the present invention may contain either a hydroxide of calcium and / or magnesium or an oxide of calcium and / or magnesium, or may contain both. In addition, it may contain either one of calcium and magnesium, or may contain both.

[0019] The chemical heat storage material of the present invention contains a hydroxide and / or oxide of calcium and / or magnesium, a hydroxide of sodium and / or potassium, and a chloride of lithium. By blending sodium and / or potassium hydroxide with lithium chloride, it is possible to realize heat storage at low temperatures without using lithium hydroxide or by reducing the amount of lithium hydroxide used. That is, by blending sodium and / or potassium hydroxide with lithium chloride, it is possible to realize heat storage at low temperatures while reducing the amount of lithium compound used. The chemical heat storage material of the present invention may further contain lithium hydroxide.

[0020] The total amount of sodium and / or potassium hydroxide and lithium chloride is 0.1 to 50 mol% when the amount of the calcium and / or magnesium hydroxide and / or oxide is 100 mol%. If the total amount is less than this range, it becomes difficult to achieve a lowering of the heat storage temperature by co-addition of these compounds. In addition, if the total amount is more than the range, the influence on the calcium and / or magnesium hydroxide and / or oxide that is the base material is large, and the amount of heat storage per unit volume or unit mass by the chemical heat storage material may decrease. The total amount is preferably 0.1 to 20 mol%, more preferably 0.3 to 15 mol%, even more preferably 0.5 to 10 mol%, even more preferably 0.8 to 8 mol%, and particularly preferably 1 to 6 mol%.

[0021] Furthermore, regarding the content ratio of sodium and / or potassium hydroxide to lithium chloride, the content of the sodium hydroxide and / or potassium hydroxide / the content of the lithium chloride is preferably in the range of 0.1 to 9 on a molar basis. By having the content ratio of the sodium hydroxide and / or potassium hydroxide to the lithium chloride within this range, it becomes easier to achieve an improvement in the reaction rate or a lowering of the heat storage temperature by the co-addition of the sodium hydroxide and / or potassium hydroxide and the lithium chloride. The content ratio is more preferably in the range of 0.25 to 4, and even more preferably in the range of 0.5 to 2.

[0022] The chemical heat storage material of the present invention may further contain a specific metal compound in addition to the hydroxide and / or oxide of calcium and / or magnesium, the hydroxide of sodium and / or potassium, and lithium chloride. By further including the specific metal compound, the reaction rate of the chemical heat storage material can be further increased. At this time, it is preferable that the specific metal compound is chemically complexed with the hydroxide and / or oxide of calcium and / or magnesium.

[0023] The specific metal is selected from the group consisting of nickel, cobalt, copper, aluminum, iron and zinc, and may contain only one of these metals or may contain two or more of them in combination. Among these, at least one selected from the group consisting of nickel, cobalt and aluminum is preferred, and nickel and / or cobalt are more preferred.

[0024] The specific metal compound is not particularly limited, but is preferably a compound with hydroxide and / or oxide of calcium and / or magnesium, and examples of the compound include halides such as chlorides and bromides, hydroxides, oxides, carbonates, acetates, nitrates, and sulfates. These may be used alone or in combination of two or more. More specifically, nickel hydroxide, cobalt hydroxide, nickel and cobalt composite hydroxide, nickel oxide, cobalt oxide, and / or nickel and cobalt composite oxide are preferred.

[0025] The amount of the specific metal compound used is preferably an amount in which the amount of the specific metal is 0.1 to 40 mol% when the amount of the hydroxide and / or oxide of calcium and / or magnesium is 100 mol%. When the amount of the specific metal is 0.1 mol% or more, it is easier to achieve an improvement in the reaction rate or a lowering of the heat storage temperature by using the specific metal compound. In addition, when the amount of the specific metal is 40 mol% or less, it is easier to increase the amount of heat storage per unit volume or unit mass by the chemical heat storage material. 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 specific metal compound used, the dehydration endothermic temperature of the chemical heat storage material can be controlled.

[0026] The chemical heat storage material in the present invention may be, but is not limited to, a mixture or dispersion of hydroxide and / or oxide of calcium and / or magnesium, hydroxide of sodium and / or potassium, lithium chloride, and, in some cases, a compound of a specific metal, which is merely physically mixed or dispersed. A part or all of each component may be chemically composited with each other, or a part or all of each component may be chemically reacted with each other to produce a third component.

[0027] The chemical heat storage material of the present invention is a chemical heat storage material that utilizes the endothermic dehydration reaction of calcium and / or magnesium hydroxide and the exothermic hydration reaction of calcium and / or magnesium oxide. Within 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 components described above or components that do not exhibit chemical heat storage action (for example, binders).

[0028] The shape of the chemical heat storage material of the present invention is not particularly limited, and any shape can be selected according to the embodiment of the consumer as long as the properties as the chemical heat storage material are not impaired to an extent that the chemical heat storage material can be implemented. Specifically, the chemical heat storage material of the present invention may be in the form of a powder, a granule, a molded body, or the like.

[0029] Next, a method for producing the chemical heat storage material of the present invention will be described. The method for producing the chemical heat storage material in the present invention is not particularly limited, but an example will be described below. First, calcium and / or magnesium hydroxide powder is added to ion-exchanged water and stirred and mixed. Then, sodium and / or potassium hydroxide and lithium chloride, or sodium and / or potassium hydroxide, lithium chloride, and a specific metal compound are added simultaneously or sequentially, and further stirred and mixed. The obtained slurry can be dried to produce a chemical heat storage material as a dry powder. The stirring and mixing method is not particularly limited, as long as the ion-exchanged water as a solvent and the calcium and / or magnesium hydroxide powder are sufficiently mixed.

[0030] The order of adding each component may be changed. In this case, for example, first, sodium and / or potassium hydroxide and lithium chloride, or sodium and / or potassium hydroxide, lithium chloride, and a compound of a specific metal are dissolved in ion-exchanged water, and calcium and / or magnesium hydroxide powder is added thereto to prepare a slurry, and then a metal acid salt is added as necessary, and the slurry is dried to produce a chemical heat storage material.

[0031] When manufacturing a chemical heat storage material having a powder, granule, or molded shape, known methods can be applied. For example, when manufacturing a powdered chemical heat storage material, sieving, crushing, and pulverization processes can be applied. In addition, 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, a molding process by press molding, injection molding, blow molding, vacuum molding, and extrusion molding can be applied.

[0032] The chemical heat storage material of the present invention can store heat by absorbing and dehydrating unused heat from a heat source of about 100 to 300 ° C., for example, factory exhaust heat. The dehydrated chemical heat storage material can easily maintain the heat storage state by keeping it in a dry state, and can be carried to a desired location while maintaining the heat storage state. When dissipating heat, the heat of hydration reaction (in some cases, water vapor sorption heat) can be taken out as thermal energy by contacting it with water, preferably water vapor. In addition, water vapor sorption can be performed on one side of the airtight space, and cold can be generated by evaporating water on the other side.

[0033] 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 to shorten the warm-up operation of an automobile, improve the amenity of passengers, improve fuel efficiency, and reduce the harmfulness of exhaust gas by improving the activity of exhaust gas catalysts. In particular, since the load due to operation of an engine is not constant and the exhaust output is unstable, direct utilization of the exhaust heat from the engine is inevitably inefficient and inconvenient. By utilizing the chemical heat storage material of the present invention, the exhaust heat from the engine is chemically stored once and heat output is provided according to the heat demand, making it possible to utilize the exhaust heat more ideally.

[0034] The present invention is not limited to the above-described embodiment. The present invention is also not limited to the above-described effects. Furthermore, the present invention can be modified in various ways without departing from the gist of the present invention.

[0035] [Disclosure items] Each of the following sections is a disclosure of a preferred embodiment.

[0036] [Item 1] containing hydroxides and / or oxides of calcium and / or magnesium, hydroxides of sodium and / or potassium, and chloride of lithium, The chemical heat storage material, wherein the total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol % relative to the hydroxide and / or oxide of calcium and / or magnesium. [Item 2] 2. The chemical heat storage material according to item 1, wherein a molar ratio of the sodium and / or potassium hydroxide to the lithium chloride is in the range of 0.1 to 9. [Item 3] Further, the composition contains a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, aluminum, iron and zinc, 3. The chemical heat storage material according to item 1 or 2, wherein the amount of the metal is 0.1 to 40 mol % relative to the hydroxide and / or oxide of calcium and / or magnesium. [Item 4] A method for producing a chemical heat storage material, comprising: mixing hydroxides and / or oxides of calcium and / or magnesium, hydroxides of sodium and / or potassium, and chloride of lithium; The total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol % based on the hydroxide and / or oxide of calcium and / or magnesium. [Item 5] 5. The method according to item 4, wherein a molar ratio of the sodium and / or potassium hydroxide to the lithium chloride is in the range of 0.1 to 9. [Item 6] In the mixing step, a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, aluminum, iron, and zinc is further mixed, 6. The method according to item 4 or 5, wherein the amount of the metal is 0.1 to 40 mol % based on the hydroxide and / or oxide of calcium and / or magnesium. EXAMPLES

[0037] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0038] (Evaluation method: Measurement of the dehydration reaction peak temperature) The chemical heat storage materials obtained in each Example and Comparative Example were subjected to thermal evaluation using a thermogravimetric / differential thermal analysis measuring device (Advance Riko, TGD9600). Specifically, the chemical heat storage material as a sample was weighed with an electronic balance, and 20 mg was placed on a platinum cell in the thermobalance. Next, while flowing an inert purge gas (argon) at 100 mL / min to the sample in the reactor, the physically adsorbed water of the sample was dried and removed at 120 ° C. Thereafter, the sample was heated to 600 ° C. at a heating rate of 10 ° C. / min, and a dehydration reaction was performed.

[0039] The dehydration reaction peak temperature (the temperature at which the weight change rate of the sample is at its maximum) (hereinafter simply referred to as the "peak temperature") of the chemical heat storage material was measured by setting the weight of the chemical heat storage material at the time when it was heated to 200°C as the starting weight and a reaction rate of 0% in order to eliminate the effects of volatile components, etc., and defining the weight reduction value when all of the magnesium hydroxide is assumed to have been converted to oxide as a reaction rate of 100%.

[0040] The mole fraction of Mg(OH)2 and the DTG curve were calculated from the thermogravimetric curve obtained from the thermobalance, and the dehydration reaction peak temperature was calculated from the DTG curve to evaluate the heat storage capacity of the sample at low temperatures. The measured values ​​of the dehydration reaction peak temperature are shown in Table 1 below. The lower the dehydration reaction peak temperature, the faster the dehydration reaction proceeds at low temperatures, which indicates that heat can be stored by low-temperature heat.

[0041] Example 1 Magnesium hydroxide (manufactured by Wako Pure Chemical Industries, purity 99.9%) was weighed out 2 g. Then, lithium chloride monohydrate (manufactured by Wako Pure Chemical Industries, purity 99.9%) was weighed out 0.104 g, and further, sodium hydroxide (manufactured by Wako Pure Chemical Industries, purity 99.9%) was weighed out 1.37 g. The sample composition (molar ratio) at this time was magnesium hydroxide: sodium hydroxide: lithium chloride = 100: 10: 5. The lithium chloride and sodium hydroxide weighed above were added to 50 mL of ion-exchanged water to prepare an aqueous solution. Next, magnesium hydroxide was added to this aqueous solution and stirred using a rotary evaporator to prepare a slurry. The slurry was further heated to evaporate the water, and then dried in air at 120 ° C. for 12 hours or more in a dryer (Advantec Toyo DRA330DA) to remove the water, thereby producing a chemical heat storage material. For the obtained chemical heat storage material, the dehydration reaction peak temperature was calculated using the above-mentioned evaluation method.

[0042] Example 2 Potassium hydroxide was used instead of sodium hydroxide, and the reagents were weighed out so that the molar ratio of magnesium hydroxide, potassium hydroxide, and lithium chloride was 100:2.5:5. Sample preparation and evaluation were carried out in the same manner as in Example 1.

[0043] Comparative Example 1 The magnesium hydroxide used in Example 1 was used as a sample to which none of sodium hydroxide, potassium hydroxide, and lithium chloride was added, and evaluation was performed.

[0044] Comparative Example 2 The reagents were weighed out so that the molar ratio of magnesium hydroxide, sodium hydroxide, and lithium chloride was 100:0:5, and sample preparation and evaluation were carried out in the same manner as in Example 1.

[0045] Comparative Example 3 The reagents were weighed out so that the molar ratio of magnesium hydroxide, sodium hydroxide, and lithium chloride was 100:10:0, and sample preparation and evaluation were carried out in the same manner as in Example 1.

[0046] [Table 1]

[0047] From Table 1, the chemical heat storage materials of Examples 1 and 2 produced by co-adding sodium hydroxide or potassium hydroxide with lithium chloride had lower peak temperatures than the chemical heat storage materials of Comparative Example 1 which contained magnesium hydroxide alone. Furthermore, the chemical heat storage materials of Examples 1 and 2 also had lower peak temperatures compared to the chemical heat storage materials of Comparative Examples 2 and 3 to which lithium chloride or sodium hydroxide was added alone. Therefore, it is understood that the present invention can provide a chemical heat storage material that can realize heat storage at low temperatures while reducing the amount of lithium compound used.

Claims

1. containing hydroxides and / or oxides of calcium and / or magnesium, hydroxides of sodium and / or potassium, and chloride of lithium, The total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol % relative to the hydroxide and / or oxide of calcium and / or magnesium.

2. The chemical heat storage material according to claim 1, wherein the molar ratio of sodium and / or potassium hydroxide to lithium chloride is in the range of 0.1 to 9.

3. Further, the composition contains a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, aluminum, iron, and zinc; The amount of the metal is 0.1 to 40 mol% relative to the hydroxide and / or oxide of calcium and / or magnesium, The chemical heat storage material according to claim 1 or 2.

4. A method for producing a chemical heat storage material, comprising: mixing hydroxides and / or oxides of calcium and / or magnesium, hydroxides of sodium and / or potassium, and chloride of lithium; The total amount of the hydroxide of sodium and / or potassium and the chloride of lithium is 0.1 to 50 mol % based on the hydroxide and / or oxide of calcium and / or magnesium.

5. The method according to claim 4, wherein a molar ratio of the sodium and / or potassium hydroxide to the lithium chloride is in the range of 0.1 to 9.

6. In the mixing step, a compound of at least one metal selected from the group consisting of nickel, cobalt, copper, aluminum, iron, and zinc is further mixed; The method according to claim 4 or 5, wherein the amount of said metal is 0.1 to 40 mol % relative to said hydroxide and / or oxide of calcium and / or magnesium.

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