JP5327729B2 - Chemical heat storage material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a chemical heat storage material and a manufacturing method thereof.

  Conventionally, a chemical heat storage material has a large amount of heat storage per volume, does not require heat retention, and has a small heat storage loss, and thus can store heat for a long period of time. Therefore, research and development related to a chemical heat storage system that uses a chemical heat storage material has been promoted (Patent Documents 1 to 3).

The invention described in Patent Document 1 relates to a chemical heat storage material and a method for producing the same, and describes means for adjusting the specific surface area after calcining calcium carbonate and converting it to calcium oxide.
The invention described in Patent Document 2 relates to a heat storage device, and the invention described in Patent Document 3 relates to a chemical heat storage material capsule. These inventions are inventions that deal with the above-mentioned pulverization of the chemical heat storage material. There, there is described the suppression of exfoliation and reduction in reactivity due to pulverization by encapsulating a heat storage material in a porous capsule or porous cylinder having a pore size.

JP-A-1-225686 Japanese Patent Publication No. 6-80395 Japanese Patent Publication No. 8-80394

  However, the chemical heat storage material described in Patent Document 1 repeats a hydration reaction and a dehydration reaction during operation as a chemical heat storage system. At that time, the powdered chemical heat storage material repeatedly expands and contracts by a volume of several tens of percent, and as a result, the powder breaks down and the particles rub against each other, resulting in a pulverized reaction. There is a problem of lowering.

  In the heat storage system, it is also important to perform heat exchange that guides heat to the outside of the system in response to the reaction. However, the heat storage device and the chemical heat storage material capsule described in Patent Documents 2 and 3 generate heat regulation such as increase in heat conduction resistance due to encapsulation of the capsule or cylindrical body and complication of the contact path depending on the distance between particles. To do. Therefore, there exists a problem that sufficient capability cannot be exhibited as a chemical heat storage system.

  This invention is made | formed in view of this conventional problem, Comprising: It aims at providing the chemical heat storage material which is excellent in durability, and can fully exhibit capability as a chemical heat storage system, and its manufacturing method. To do.

The first invention is a cage-like structure having a large number of pores obtained by mixing and firing clay minerals and combustible particles, and is supported on the outer surface and inside the pores of the cage-like structure. has been to have a chemical heat storage material,
The clay mineral is a chemical heat storage material characterized by being at least one selected from sepiolite, palygorskite, and bentonite (Claim 1).
The chemical heat storage material of the present invention can obtain the following effects by supporting the chemical heat storage material on the outer surface and inside the pores of the cage structure.

  First, the cage structure is obtained by mixing and firing clay minerals and combustible particulates. The combustible granular material is burned away by the firing. For this reason, the cage structure is considered to be a cage structure having a large number of pores in which pores are formed in the portion where the combustible granular material is present, as well as the clay mineral.

And since the said cage structure has the cage structure which has many holes, it can carry | support a chemical heat storage material favorably. Due to the properties of the clay mineral, such as fiber, porosity, plasticity, etc., the chemical heat storage material has a structure in which a powdered chemical heat storage material is dispersedly supported in the skeleton of the clay mineral and is structurally stable.
In addition, since the pores serve as a passage through which water vapor necessary for heat storage / radiation of the chemical heat storage material passes, the chemical heat storage system configured using the chemical heat storage material is sufficiently capable as the chemical heat storage system. Can be demonstrated.

  The cage structure is not involved in the dehydration / hydration reaction. Therefore, by supporting a chemical heat storage material on the outer surface of the cage structure and inside the pores, thermal disconnection due to structural change accompanying volume change of dehydration and hydration is suppressed, and performance degradation is reduced even after repeated cycles. Can be minimized. Therefore, the chemical heat storage material excellent in durability can be provided. Moreover, pulverization of the chemical heat storage material associated with the hydration / dehydration reaction can be suppressed.

  Thus, according to the present invention, it is possible to provide a chemical heat storage material that is excellent in durability and capable of sufficiently exhibiting the ability as a chemical heat storage system.

The second invention is a cage structure having a large number of pores obtained by mixing and firing a clay mineral and a combustible granular material, and is supported on the outer surface and inside the pores of the cage structure. A method for producing a chemical heat storage material, comprising:
A cage-like structure manufacturing step of obtaining a cage-like structure by firing a cage-like structure material containing a clay mineral and combustible particulates;
A slurry preparation step of preparing a slurry by mixing the cage structure into a heat storage material suspension in which the chemical heat storage material is dispersed in a dispersion;
It has a drying step of drying the slurry,
It said clay mineral is sepiolite, palygorskite, and the production method of the chemical heat storage material which is characterized in that at least one selected from bentonite (claim 8).

As described above, the method for producing a chemical heat storage material according to the present invention includes the above-described cage-shaped structure manufacturing process, slurry manufacturing process, and drying process, thereby mixing the above clay mineral and combustible particulate matter. It is possible to manufacture a chemical heat storage material having a cage structure having a large number of pores obtained by firing and a chemical heat storage material supported on the outer surface of the cage structure and inside the pores. .
Therefore, according to this invention, the chemical heat storage material which is excellent in durability and can fully exhibit capability as a chemical heat storage system can be manufactured.

As described above, the chemical heat storage material of the first invention includes a cage structure having a large number of pores obtained by mixing and firing a clay mineral and a combustible granular material, and the cage structure. And a chemical heat storage material supported on the outer surface and inside the pores.
The cage structure preferably has a granular shape, and the size is preferably several hundred μm to several mm. The pore size of the cage structure is preferably about 10 μm.
And it is preferable that the said chemical heat storage material has an average particle diameter of 1-5 micrometers.

In the first and second inventions, any combustible particulate material may be used as long as it has good confusion with clay minerals and is burned off by firing. Among these, it is preferable that the said combustible granular material is 1 type (s) or 2 or more types among palm, a piece of wood, carbon black, and ketjen black (Claim 2, 11 ).

The clay mineral is preferably a clay mineral having a layer ribbon structure.
The clay mineral having the above layer ribbon structure has a fibrous form having a large porous surface area and a large specific surface area. Therefore, the chemical heat storage material can be well organized and structured by the properties of the clay mineral such as fiber, porosity, and plasticity.

Among the clay minerals having the layer ribbon structure, sepiolite and / or palygorskite are preferable .
Here, the sepiolite is a clay mineral having a layered ribbon structure. Specifically, the sepiolite is one of clay minerals in which a plurality of single chains resembling pyroxene are combined to form a tetrahedral ribbon. Sepiolite includes, for example, hydrous magnesium silicate that can be represented by the chemical formula Mg ₈ Si ₁₂ O ₃₀ (OH) ₄ (OH ₂ ) ₄ · 8H ₂ O. Sepiolite itself is porous and has a fibrous shape with a large specific surface area. Sepiolite also includes variants of those represented by the above chemical formula.

The clay mineral may be bentonite.
Since the bentonite is a clay mineral with strong adhesive strength, the chemical heat storage material can be well organized and structured by this adhesive strength.

In addition, the chemical heat storage material is preferably a hydration reaction type chemical heat storage material that absorbs heat with a dehydration reaction and dissipates heat with a hydration reaction, and the chemical heat storage material is an oxide with a dehydration reaction. It is preferable that it is a hydration reaction type chemical heat storage material that becomes a hydroxide in accordance with the hydration reaction (claims 3 and 12 ).
The said chemical heat storage material molded object can perform heat dissipation and heat storage favorably by a hydration reaction and dehydration (reverse hydration) reaction, and can improve the performance as a heat storage system. Although the volume of the chemical heat storage material repeatedly expands and contracts with the hydration reaction and dehydration reaction, the chemical heat storage material is well supported by the cage structure, so that the chemical heat storage material is pulverized. Can be sufficiently suppressed.

Moreover, it is preferable that the said chemical heat storage material consists of hydroxides.
In this case, when producing the chemical heat storage material, when preparing the heat storage material suspension in which the chemical heat storage material is dispersed in the dispersion, as the binder for mixing and thickening, as the chemical heat storage material When a carbonic acid compound is used, water that could not be used can be used. Thereby, the moldability at the time of shape | molding the said chemical heat storage material can be improved. Moreover, high-temperature baking at around 1000 ° C. during the decarbonation step, which was necessary when a carbonic acid compound was used as the chemical heat storage material, becomes unnecessary. Thereby, a calcination temperature can be made low and the freedom degree of a use material and a process can be raised.

And it is preferable that the said hydroxide is an inorganic compound.
From the viewpoint of heat storage density, long-term heat storage stability, release rate, and safety, an inorganic system is preferable.
In this case, the material stability with respect to the heat storage / heat radiation reaction (dehydration / hydration reaction) of the chemical heat storage material is increased. Therefore, the said chemical heat storage material molded object can acquire the stable heat storage effect over a long period of time.

The inorganic compound is preferably an alkaline earth metal hydroxide.
In this case, the material stability with respect to the heat storage / heat radiation reaction (dehydration / hydration reaction) of the chemical heat storage material is increased. Therefore, the chemical heat storage material can obtain a stable heat storage effect over a long period of time. In addition, by using a safe material with a small environmental load as the chemical heat storage material, it is easy to ensure safety including manufacturing, use, recycling, and the like.

The alkaline earth metal hydroxide is preferably one or more of calcium hydroxide, magnesium hydroxide, and barium hydroxide.
In this case, it is possible to further improve the material stability of the chemical heat storage material with respect to heat storage / radiation reaction (dehydration / hydration reaction), and stably maintain the heat storage effect of the chemical heat storage material over a long period of time. can do.
A mixture of magnesium hydroxide and calcium hydroxide can also be used.

  In addition to the alkaline earth metal hydroxide, the inorganic compound may be one or more of nickel hydroxide, aluminum hydroxide, cobalt hydroxide, and copper hydroxide.

Moreover, it is preferable that the said chemical heat storage material further mixes a heat conductivity improving material (Claims 4 and 13 ).
Any thermal conductivity improving material can be used as long as it has a higher thermal conductivity than clay minerals and does not burn out during firing. Then, as the thermal conductivity enhancing material, for example, it may be carbon nanotube, fibrous AlN, fibrous SiC, fibrous Al ₂ O _3, and the like. Among them, the thermal conductivity improving material is preferably a carbon nanotube (claims 5 and 14 ).
Mixability of clay mineral and carbon is good and can be dispersed uniformly.

Furthermore, the chemical heat storage material is preferably a chemical heat storage material molded body obtained by molding into a desired shape (claim 6).
And it is preferable to have the said hollow part formed by penetration (Claim 7 ).
In this case, since the said hollow part becomes a flow path into and out of water vapor | steam, the reactivity of a chemical heat storage material can be ensured, and heat storage and heat dissipation can be performed favorably.

Moreover, the manufacturing method of the chemical heat storage material of 2nd invention has a cage-shaped structure preparation process, a slurry preparation process, and a drying process as mentioned above.
In the cage structure manufacturing step, a cage structure material containing clay mineral and combustible particulates is used. The cage structure material is composed of clay minerals, combustible granules and water. A mixture is preferred (Claim 9 ).
The content of the combustible particles in the cage structure material is preferably 10% by weight to 90% by weight.

Further, the cage structure material may contain a thickener.
As said thickener, methylcellulose, carrageenan, polyvinyl alcohol etc. can be used, for example.
Moreover, the said thickener forms a void | hole after baking and may work as a combustible granule.

Moreover, a cage structure is obtained by firing the produced cage structure material.
The firing is preferably performed under conditions of a holding temperature of 500 to 1200 ° C. and a holding time of 0.5 to 10 hours.
When carbon nanotubes are included in the cage structure material as a material for improving thermal conductivity, firing is performed at a lower firing temperature.

And in the said slurry preparation process, the said cage | basket-like structure is mixed with the thermal storage material suspension which disperse | distributed the said chemical thermal storage material in the dispersion liquid.
As the dispersion, water or a solvent may be used as long as the chemical heat storage material can be dispersed. From the viewpoint of environmental measures, it is preferable to use water as the dispersion. Therefore, it is preferable that the heat storage material suspension is a mixture of a chemical heat storage material and water (claim 10 ).

And a slurry is produced by mixing the said cage structure to the said thermal storage material suspension. That is, the chemical heat storage material is disposed on the outer surface and the pores of the cage structure by entanglement of the heat storage material suspension with the cage structure.
Moreover, since the optimum values such as the blending amount and viscosity of the slurry vary depending on the production environment and the like, it is preferable to derive them appropriately through experiments.

In the drying step, the chemical heat storage material is obtained by drying the slurry.
By drying the slurry, the cage structure and the chemical heat storage material are integrated.
And it is preferable to perform the said drying process on the conditions of holding temperature 60-150 degreeC and holding time 0.5-100 hours.

Moreover, it is preferable to have the shaping | molding process after shape | molding the said slurry in a desired shape after the said slurry preparation process to make a molded object (Claim 15 ).
The molding step can be performed by extrusion molding, compression molding, or the like.

Example 1
This example explains a chemical heat storage material according to an embodiment of the present invention.
As shown in FIG. 1, in this example, a cage structure 5 having a large number of pores 50 obtained by mixing and firing a clay mineral 2 and a combustible granular material 3, and the cage structure A chemical heat storage material 1 having a chemical heat storage material 2 carried on the outer surface of 5 and inside the pores was produced.

More specifically, first, as shown in FIGS. 1 (a) and 1 (b), as a raw material of the cage structure material 4, combustible granular material 3, clay mineral 2, and thickener (not shown) are used. Prepared.
As the combustible granular material 3, granular activated carbon was prepared.
As the clay mineral 2, sepiolite (Mg ₈ Si ₁₂ O ₃₀ (OH) ₄ (OH ₂ ) ₄ · 8H ₂ O) was prepared.
Moreover, methylcellulose was prepared as a thickener.

The sepiolite is a clay mineral having a layer ribbon structure.
The sepiolite exhibits a fiber shape having a fiber diameter smaller than the average particle diameter of the chemical heat storage material when suspended in water.
Specifically, the sepiolite preferably has a wire diameter (fiber diameter) of 1 μm or less and a length (fiber length) of 200 μm or less. In this example, Turkish sepiolite having a wire diameter of approximately 0.01 μm and a length of approximately several tens of μm is prepared.
Instead of Turkish sepiolite, for example, Spanish sepiolite having a wire diameter of 0.1 μm and a length of approximately 100 μm can be used.

Moreover, as the chemical heat storage material 6, a hydroxide Ca (OH) ₂ of an alkaline earth metal Ca was prepared. The average particle diameter D of this chemical heat storage material is 7 μm (laser diffraction measurement method, according to SALD-2000A manufactured by Shimadzu Corporation).
The chemical heat storage material 6 reversibly repeats heat storage and heat release by the following reactions.
Ca (OH) ₂ Ｃａ CaO + H ₂ O
Further, when the heat storage amount and the heat generation amount Q are shown together in the above formula, the following is obtained.
Ca (OH) ₂ + Q → CaO + H ₂ O
CaO + H ₂ O → Ca (OH) ₂ + Q

Next, the manufacturing method of the chemical heat storage material 1 is demonstrated.
In the cage-like structure manufacturing step, first, as shown in FIG. 1 (b), a cage-like structure in which 70 g of the flammable granular material, 30 g of the clay mineral, 20 g of the thickener, and 120 g of water are mixed. Body material 4 was produced.
Thereafter, the cage structure material 4 was fired under the conditions of a holding temperature of 650 ° C. and a holding time of 3 hours, and a cage structure 5 shown in FIG.

Next, in the slurry preparation step, first, a heat storage material suspension in which 100 g of Ca (OH) ₂ was dispersed in 200 mL of water was prepared.
Then, as shown in FIG.1 (d), the said cage | basket structure 5 and the chemical heat storage material 6 are compounded by producing the slurry by mixing the said cage | basket structure 10g with the said thermal storage material suspension. Made it.

Then, in the molding step, using the slurry, as shown in FIG. 2, a molded body having a shape (outer diameter: 100 mm × 40 mmφ, diameter of the hollow portion: 10 mmφ) having a hollow portion 11 formed through is molded. did.
And in the drying process, the chemical heat storage material molded body 1 (chemical heat storage material) shown in FIG. )

Next, after the obtained chemical heat storage material molded body 1 is loaded into a chemical heat storage reactor, a dehydration (at 400 ° C.) / Hydration (at 200 ° C.) cycle is repeated, and the reaction rate of Ca (OH) ₂ is determined by a thermogravimetric method. It was evaluated by.
As a result, the reaction rate of Ca (OH) _{2 in} the first cycle was 86%, and the reaction rate in the 10th cycle was 83%. Thus, it was confirmed that the chemical heat storage material molded body 1 of the present example was excellent in cycle characteristics without much deterioration in characteristics even after repeated cycles.

  As described above, according to the present invention, it is understood that a chemical heat storage material that is excellent in durability and can sufficiently exhibit the ability as a chemical heat storage system can be obtained.

In this example, sepiolite was used as the clay mineral, but palygorskite, bentonite, or the like can be used instead of sepiolite.
In this example, calcium hydroxide is used as the chemical heat storage material. However, magnesium hydroxide or a mixture of magnesium hydroxide and calcium hydroxide can be used instead.

(Example 2)
This example is obtained by baking the cage structure of Example 1 above after mixing 30 g of clay mineral, 70 g of combustible granular material, 20 g of thickener, 120 g of water, and 5 g of thermal conductivity improving material. This is an example of changing to a cage structure. Others were performed in the same manner as in Example 1.
The same clay mineral, combustible particulates, and thickener as those used in Example 1 were used.
Moreover, fibrous AlN (fibrous aluminum nitride) was prepared as the thermal conductivity improving material.

For the chemical heat storage material molded body of this example, the reaction rate of Ca (OH) ₂ was evaluated in the same manner as in Example 1 above. As a result, the reaction rate of Ca (OH) _{2 in} the first cycle was 88%, and the reaction rate in the 10th cycle was 85%. Thus, it was confirmed that the chemical heat storage material molded body 1 of the present example was excellent in cycle characteristics without much deterioration in characteristics even after repeated cycles.

  The chemical heat storage material molded body of this example is a composite including a chemical heat storage material, a clay mineral, and fibrous AlN. Therefore, due to the properties of the clay mineral 4 such as fiber, porosity, and plasticity, the composite has a structure in which a powdered chemical heat storage material and fibrous AlN are dispersedly supported in the skeleton of the clay mineral 4, The thermal conductivity of the chemical heat storage material is improved. Therefore, it is considered that better cycle characteristics were obtained.

In this example, fibrous AlN is used as the thermal conductivity improving material. However, carbon nanotubes, fibrous SiC, fibrous Al ₂ O ₃ or the like can be used instead.

(Comparative Example 1)
In this example, for comparison, only the Ca (OH) ₂ used as the chemical heat storage material in Examples 1 and 2 was evaluated for the reaction rate of Ca (OH) ₂ .
After loading Ca (OH) ₂ into the chemical heat storage reactor, the reaction rate of Ca (OH) ₂ was evaluated by the thermogravimetric method in the same manner as in Example 1. As a result, the reaction rate of Ca (OH) _{2 in} the first cycle was 80%, the reaction rate in the 10th cycle was 32%, and when the cycle was repeated, a specific decrease was observed.

Explanatory drawing which shows the manufacture process of the chemical thermal storage material in Example 1. FIG. Explanatory drawing which shows the chemical heat storage material molded object in Example 1. FIG.

Explanation of symbols

1 Chemical heat storage material molding (chemical heat storage material)
2 Clay Minerals 3 Combustible Granules 4 Cage Structure Material 5 Cage Structure 6 Chemical Heat Storage Material

Claims (15)

A cage-like structure having a large number of pores obtained by mixing and firing clay minerals and combustible particles, and a chemical heat storage material supported on the outer surface of the cage-like structure and inside the pores. I have a,
The chemical heat storage material , wherein the clay mineral is at least one selected from sepiolite, palygorskite, and bentonite .   2. The chemical heat storage material according to claim 1, wherein the combustible granular material is one or more of palm, wood chips, carbon black, and ketjen black. 3. The chemical heat storage material according to claim 1 or 2, wherein the chemical heat storage material is a hydration reaction type chemical heat storage material that becomes an oxide with a dehydration reaction and a hydroxide with a hydration reaction. material. The chemical heat storage material according to any one of claims 1 to 3, further comprising a heat conductivity improving material. 5. The chemical heat storage material according to claim 4, wherein the thermal conductivity improving material is a carbon nanotube. The chemical heat storage material according to any one of claims 1 to 5, wherein the chemical heat storage material is a chemical heat storage material molded body formed into a desired shape. 7. The chemical heat storage material according to claim 6, wherein the chemical heat storage material molded body has a hollow portion formed through. A cage-like structure having a large number of pores obtained by mixing and firing clay minerals and combustible particulates, and a chemical heat storage material supported on the outer surface and inside the pores of the cage-like structure A method of manufacturing comprising:
A cage-like structure manufacturing step of obtaining a cage-like structure by firing a cage-like structure material containing a clay mineral and combustible particulates;
A slurry preparation step of preparing a slurry by mixing the cage structure into a heat storage material suspension in which the chemical heat storage material is dispersed in a dispersion;
It has a drying step of drying the slurry,
The method for producing a chemical heat storage material, wherein the clay mineral is at least one selected from sepiolite, palygorskite, and bentonite . 9. The method for producing a chemical heat storage material according to claim 8, wherein the cage structure material is a mixture of a clay mineral, a combustible granular material, and water. The method for producing a chemical heat storage material according to claim 8 or 9, wherein the dispersion is water. The method for producing a chemical heat storage material according to any one of claims 8 to 10, wherein the combustible granular material is one or more of palm, wood chips, carbon black, and ketjen black. . The chemical heat storage material according to any one of claims 8 to 11, wherein the chemical heat storage material is an hydration reaction type chemical heat storage material that becomes an oxide along with a dehydration reaction and becomes a hydroxide along with a hydration reaction. A method for producing a chemical heat storage material. The method for producing a chemical heat storage material according to any one of claims 8 to 12, wherein the cage structure material further contains a thermal conductivity improving material. 14. The method for producing a chemical heat storage material according to claim 13, wherein the thermal conductivity improving material is a carbon nanotube. The method for producing a chemical heat storage material according to any one of claims 8 to 14, further comprising a molding step of forming the slurry into a desired shape after the slurry preparation step.

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