JP5503377B2 - Manufacturing method of chemical heat storage material structure - Google Patents

Description

  The present invention relates to a method for manufacturing a chemical heat storage material structure using a chemical heat storage material that absorbs and dissipates heat.

  A chemical heat storage material, which is a substance that can absorb and release heat by using a chemical reaction, has been widely known, and its use is being studied in various fields.

  For example, a chemical heat storage material molded body is disclosed, which is obtained by firing a molded body that is obtained by primary molding of a powder chemical heat storage material and mixing clay mineral at a predetermined ratio and then secondary molding. (For example, refer to Patent Document 1), it is described that firing within a range of 350 to 500 ° C. and firing at a temperature at which a dehydration reaction of a chemical heat storage material in a hydroxide state does not occur.

JP 2009-132844 A

  However, in the conventional chemical heat storage material molded body fired at a firing temperature of about 350 to 500 ° C., the firing temperature is relatively low, and therefore the process of hydration and dehydration when the heat storage / heat radiation reaction is performed. Therefore, warping and cracking are likely to occur in the molded body, and establishment of a technique capable of improving such brittleness is demanded.

  On the other hand, in order to further increase the structural strength of the molded body, firing at a high temperature of usually 600 ° C. to 700 ° C. or more is required. The amount of heat storage material such as hydroxide that hydrates and dehydrates with the formation of silicate due to the reaction between chemical heat storage material and clay mineral, and the reactivity of the molded product after firing, that is, heat storage and heat dissipation, decreases. There is.

  The present invention has been made in view of the above, and is a chemical heat storage capable of producing a heat storage material structure having excellent heat storage / heat dissipation properties (hydration / dehydration amount) as compared with the prior art while ensuring strength. It aims at providing the manufacturing method of a material structure, and makes it a subject to achieve this objective.

  The present invention has a technically contradictory relationship between the strength of the fired structure and heat storage / heat release reactivity (hydration / dehydration amount), that is, while maintaining strength that does not cause warping or cracking. In order to increase the rate, it is necessary to control the rate of formation of silicate, which is a reaction product of chemical heat storage materials and clay minerals, and this is achieved based on the knowledge that control under firing conditions is possible. It is a thing.

In order to achieve the above object, the method for producing a chemical heat storage material structure of the present invention comprises:
<1> At least a mixing step of mixing a powdery chemical heat storage material and a clay mineral having a layered ribbon structure, and controlling a firing temperature in a temperature range of 600 ° C. or more and less than 800 ° C., and firing time after firing Control so that at least one of hydration amount and dehydration amount (mass basis) at the time of heat storage and heat dissipation reaction is in the range of 60% by mass or more of the total dehydration amount by dehydration reaction of the mixed chemical heat storage material, firing the mixture obtained in the mixing step, provided, a firing step of silicate is made form comprising at least one of said chemical heat storage material and alkaline earth metal comprising the reaction product of the clay mineral It is composed.

  In the present invention, the rate of change in the amount of hydration and / or dehydration (mass) when the rate of formation of silicate, which is a reaction product of a chemical heat storage material and clay mineral, is stored and released after firing is increased. In addition, by controlling the firing temperature and / or firing time during firing, the reactivity (silicate formability) at the interface where the chemical heat storage material and the clay mineral are in contact with each other has the desired strength and heat storage / heat dissipation properties. Can be selected. As a result, the heat storage / heat radiation reactivity can be enhanced while maintaining the strength that can prevent the occurrence of warping, cracking, and the like associated with the hydration / dehydration reaction.

  In the process in which the dehydration reaction of the chemical heat storage material charged in the mixture proceeds during firing, the amount of hydration when firing is performed in a predetermined temperature range of 600 ° C. or more and less than 800 ° C., and the heat storage / heat dissipation reaction is performed after firing, and If the amount of dehydration (mass basis) is such that the dehydration reaction is sufficiently performed and 60% by mass or more of the total amount of dehydration generated from the chemical heat storage material is maintained, the chemical heat storage material and clay The contact interface with the mineral can be reduced moderately, and the strength of the reaction product is maintained, but the reaction is suppressed to the extent that the chemical heat storage material does not decrease too much, improving heat storage and heat dissipation. Can be made.

< 2 > In the method for producing a chemical heat storage material structure according to < 1 >, at least one of a hydration amount and a dehydration amount when the heat storage and heat release reaction is performed after firing from the viewpoint of further improving heat storage and heat release properties. It is a more preferable aspect to control the firing time so that (mass basis) is maintained in the range of 80% by mass or more of the total dehydrated amount.

< 3 > In the method for producing a chemical heat storage material structure according to <1> or < 2>, a dehydration step of further dehydrating the chemical heat storage material in a temperature region of less than 600 ° C. in advance before the firing step. The aspect which has is preferable.

  Before proceeding to the firing step, the chemical heat storage material contained in the mixture undergoes a dehydration reaction in a temperature range below 600 ° C. at which the firing does not start, thereby reducing the particle size of the chemical heat storage material, and removing the clay mineral and clearance. Therefore, the number of interfaces that come into contact with clay minerals is reduced, and the amount of silicate produced by the reaction between the two can be suppressed. Thereby, while maintaining the high intensity | strength which does not produce a curvature, a crack, etc., it is more effective by the improvement of heat storage and heat dissipation reactivity.

< 4 > In the method for producing a chemical heat storage material structure according to < 3 >, in the dehydration step, the ratio of the dehydration amount of the chemical heat storage material to the dry mass of the mixture causes the chemical heat storage material before dehydration to undergo a dehydration reaction. An embodiment in which dehydration is performed within a range of 50% by mass or less of the total amount of dehydration produced in this manner is preferable. More preferably, dehydration is performed within a range of 20% by mass or less of the total dehydration amount.

  By maintaining the ratio of the amount of dehydration due to the dehydration reaction of the chemical heat storage material within 50% by mass of the dry mass of the mixture, and further within 20% by mass, maintaining a high strength that does not cause warping or cracking, The effect of improving heat storage / heat radiation reactivity can also be enhanced.

< 5 > In the method for producing a chemical heat storage material structure according to < 3 >, the dehydration step is preferably performed in such a manner that dehydration is performed within a range where the volume reduction rate of the chemical heat storage material before dehydration is within 20%. More preferably, dehydration is performed in a range where the volume reduction rate of the chemical heat storage material before dehydration is within 10%.
Moreover, in the manufacturing method of the chemical heat storage material structure according to any one of <1> to <5>, the mass ratio of the silicate formed in the firing step to the chemical heat storage material is 1 to 15% by mass. It is preferable to be in the range.

  By suppressing the volume reduction rate to 20% by mass or even 10% by mass or less, the clearance between the clay mineral increases while maintaining the strength, so the interface in contact with the clay mineral decreases and the reaction between the two Can reduce the amount of silicate generated. Thereby, while maintaining the high intensity | strength which does not produce a curvature, a crack, etc., the improvement effect of a thermal storage and a thermal radiation reactivity is high.

< 6 > In the method for producing a chemical heat storage material structure according to any one of <1> to < 5 >, the chemical heat storage material is preferably an alkaline earth metal hydroxide. Furthermore, calcium hydroxide in which the alkaline earth metal is calcium is more preferable.
Since alkaline earth metal hydroxide is used as the chemical heat storage material, the material stability against heat storage and heat release reaction (hydration / dehydration) is high. Therefore, a stable heat storage effect can be obtained over a long period of time.

  According to the present invention, there is provided a method for producing a chemical heat storage material structure capable of producing a heat storage material structure having excellent heat storage and heat dissipation properties (hydration / dehydration amount) as compared with the conventional technology while ensuring strength. Can be provided.

It is the graph which showed the temperature change at the time of performing each process, such as dehydration and baking, sequentially. It is a graph which shows the result of a weight change when each process, such as dehydration and baking, is performed sequentially by thermogravimetry. It is a graph which compares and shows the production amount of the merbinite of Example 1 and Comparative Example 1. 4 is a graph showing the reaction rates of Example 1 and Comparative Example 1 in comparison.

Hereinafter, the manufacturing method of the chemical heat storage material structure of the present invention will be described in detail.
The method for producing a chemical heat storage material structure of the present invention includes a mixing step of mixing at least a powdery chemical heat storage material and a clay mineral having a layered ribbon structure, and the obtained mixture is mixed with the chemical heat storage material and the clay mineral. Silicate containing at least one kind of alkaline earth metal is a ratio that increases the change width of at least one of hydration amount and dehydration amount (mass basis) when subjected to heat storage and heat release reaction after firing. And a firing step of firing by controlling at least one of a firing temperature and a firing time. In the firing step in the present invention, the firing temperature is controlled in a temperature range of 600 ° C. or more and less than 800 ° C., and the firing time is at least one of the hydration amount and the dehydration amount when the heat storage / heat release reaction is performed after firing (mass basis). Is controlled to be in the range of 60% by mass or more of the total dehydration amount by the dehydration reaction of the chemical heat storage material to be mixed, and the reaction mixture of the chemical heat storage material and clay mineral is produced by firing the mixture obtained in the mixing step A silicate containing at least one alkaline earth metal. The method for producing a chemical heat storage material structure of the present invention preferably has a dehydration step prior to the firing step, and may be further provided with other steps as necessary.

In the present invention, the contact temperature between the chemical heat storage material and the clay mineral is reduced by reducing the diameter of the powdered chemical heat storage material by controlling the baking temperature and / or the baking time. By doing so, it is possible to suppress the reactivity (silicate formation) between the two, in other words, the amount of decrease in the chemical heat storage material (for example, Ca (OH) ₂ ) can be suppressed. This maintains the balance between the reaction between the chemical heat storage material and clay mineral in the firing process and the existing amount of the chemical heat storage material after firing, and provides heat storage and heat dissipation reactivity while having the strength to withstand warping and cracking during the reaction. Can be improved.

  It should be noted that the amount of change in the amount of hydration and / or dehydration when heat storage and heat release reactions are increased is that the proportion of chemical heat storage materials present after firing is higher than in the past, and the heat storage reaction or heat release reaction proceeds actively. This means that the amount of water stored during the hydration reaction or the amount of water discharged during the dehydration reaction increases.

-Mixing process-
In the mixing step in the present invention, at least a powdery chemical heat storage material and a clay mineral having a layered ribbon structure are mixed. The mixture obtained by mixing may be further molded and used.

  The mixing is not particularly limited as long as the chemical heat storage material and the clay mineral can be mixed together, and can be appropriately selected depending on the case. Specific examples of mixing methods include (1) a method of preparing a mixed powder by mixing a powdered chemical heat storage material and a powdered clay mineral, and (2) pulverizing both the chemical heat storage material and the clay mineral. (3) The powdered chemical heat storage material and the powdered clay mineral are both dispersed and suspended in the medium, mixed, and then dried by filtration, drying, etc. (4) Mixing a heat storage material suspension in which a chemical heat storage material is dispersed and suspended in a medium and a clay mineral suspension in which a clay mineral is dispersed and suspended in a medium, filtering and drying And the like, and the like, and the like.

  In the case of dispersion suspension, the dispersion can be performed by appropriately selecting a known disperser and stirrer and adjusting the dispersion conditions. The medium used at this time can employ a liquid that can disperse the dispersoid and can be removed by filtration, heating, or the like. For example, water, a solvent, or a mixed solvent thereof can be used.

(Chemical heat storage material)
The mixture (or molded product thereof) in the present invention contains at least one powdery chemical heat storage material. A chemical heat storage material is a substance that can absorb and release heat using a chemical reaction, and is present as a powder in the structure. The chemical heat storage material being powdery means a state of powder containing particles.

Examples of the chemical heat storage material include calcium hydroxide (Ca (OH) ₂ ), magnesium hydroxide (Mg (OH) ₂ ), barium hydroxide (Ba (OH) ₂ ), and hydrates thereof (Ba (OH)). Inorganic hydroxides of alkaline earth metals such as ₂ · H ₂ O), inorganic hydroxides of alkali metals such as lithium hydroxide monohydrate (LiOH · H ₂ O), aluminum oxide trihydrate ( Examples thereof include inorganic oxide hydrates such as Al ₂ O ₃ .3H ₂ O) and layered double hydroxides such as MgAl (OH) ₂ OH.
Among them, a hydration reactive heat storage material that absorbs heat with a dehydration reaction and dissipates heat with a hydration reaction is preferable, and calcium hydroxide (Ca (OH) ₂ ) is particularly preferable.
Moreover, the marketed product may be used for a chemical heat storage material, and Ibuki lime NEO-1 (Ca (OH) ₂ ) etc. by Omi Mining Co., Ltd. can be used as an example of a commercial product.

The average particle size of the powdery chemical heat storage material is preferably 50 μm or less in terms of the average primary particle size. When the average primary particle diameter of the chemical heat storage material present in the mixture is 50 μm or less, a reaction with the clay mineral is likely to occur and a reaction product is easily obtained, so that a stronger porous structure is obtained. Among these, the average primary particle diameter is more preferably 30 μm or less, and further preferably 10 μm or less. Further, the lower limit of the average primary particle size is desirably 0.1 μm.
The average primary particle size is a value measured by a laser diffraction / scattering method using a laser diffraction / scattering particle size distribution analyzer SALD-2000A (manufactured by Shimadzu Corporation).

Here, heat storage and heat dissipation will be described using calcium hydroxide (Ca (OH) ₂ ) as an example.
Ca (OH) ₂ , which is a chemical heat storage material, stores heat (absorbs heat) as it dehydrates, and dissipates heat (generates heat) as it hydrates (restores to calcium hydroxide). That is, Ca (OH) ₂ can reversibly repeat heat storage and heat dissipation by the reactions shown below.
Ca (OH) ₂ Ｃａ CaO + H ₂ O
In addition, when the heat storage amount and the heat generation amount Q are also shown, this is as follows.
Ca (OH) ₂ + Q → CaO + H ₂ O
CaO + H ₂ O → Ca (OH) ₂ + Q

  Between the powders of the powdery chemical heat storage material, the clay mineral described later is interposed, and the clay mineral has a porous skeletal structure, in which the powder of the chemical heat storage material is dispersed and held Is formed. In the structure, the powder of the chemical heat storage material is held in a dispersed state and is excellent in water vapor diffusibility due to the porosity, so that the above reaction is likely to occur in many powders.

  As content in the mixture (or its molded object) of a chemical heat storage material, 20-85 volume% is preferable with respect to the mixture (or its molded object) whole volume in a volume ratio, and 60-80 volume% is more preferable. . Moreover, in mass ratio, 60-90 mass% is preferable with respect to a mixture (or its molded object) total mass, and 70-90 mass% is more preferable. When the content of the chemical heat storage material is 20% by volume or more or 60% by mass or more, the heat absorption and heat generation amount can be kept high, and when it is 85% by volume or less or 90% by mass or less, the structure having higher structural strength. Things are obtained.

(Clay mineral)
The mixture (or a molded product thereof) in the present invention contains at least one clay mineral having a layered ribbon structure. Clay minerals with a layered ribbon structure are clay minerals (layered silicate minerals) in which a plurality of single chains resembling pyroxene are combined to form a tetrahedral ribbon, giving viscosity to chemical heat storage materials and having a porous structure And the structural strength of the structure can be kept high. Moreover, the diffusibility of water vapor | steam can also be provided.

Examples of the clay mineral include sepiolite [hydrated magnesium silicate represented by Mg ₈ Si ₁₂ O ₃₀ (OH) _4. (OH ₂ ) ₄ .8H ₂ O], attapulgite [palygorskite; = (Mg · AL) ₂ Hydrous magnesium silicate having a palygorskite structure represented by Si ₄ O ₁₀ (OH) · 4H ₂ O, wire diameter of 5 μm or less, kaolinite [kaolin; = Al ₂ (Si ₂ O ₅ ) (OH) ₄ Aluminum silicate, wire diameter of 1 μm or less], and the like, and one or more of these can be used in combination.
As the clay mineral, a commercially available product may be used. As an example of a commercially available product, Turkish sepiolite manufactured by Omi Mining Co., Ltd. can be used.

A clay mineral having a layered ribbon structure has an advantage of less sintering (aggregation) compared to the following bentonite which does not belong to this. In particular, sepiolite is sintered at a temperature close to the dehydration temperature of the chemical heat storage material, and there is an advantage that the specific surface area is less reduced by sintering at that temperature.
The clay mineral may be appropriately selected according to the application and the like in consideration of such advantages.

In the present invention, bentonite which does not belong to the clay mineral having the layer ribbon structure may be included in addition to the clay mineral having the layer ribbon structure. A clay mineral and bentonite may be mixed. Bentonite is a clay mineral having a stronger adhesive force than a clay mineral having a layered ribbon structure, and can obtain a strong porous structure alone (in a state where it is not mixed with the clay mineral). Further, for example, it contributes to improving the bonding strength to the metal wall, and a porous structure in which pores are formed between the powders of the chemical heat storage material can be obtained even with a composition using bentonite.
In this invention, the structure which mixes the clay mineral which mixed the clay mineral and bentonite of a layer ribbon structure with a powdery chemical heat storage material may be sufficient. In this case, the ratio of bentonite is preferably 2 to 20% by mass with respect to the clay mineral having a layer ribbon structure.

  The content of the clay mineral in the mixture (or molded product thereof) is preferably 10 to 40% by mass, more preferably 25 to 35% by mass, based on the total mass of the mixture (or molded product thereof). . When the content of the clay mineral is 10 mass or more, higher structural strength is easily obtained, and when it is 40 mass% or less, a higher endothermic heat generation amount is easily obtained.

(Other ingredients)
At the time of mixing, other components such as an organic binder and additives such as ethanol may be mixed together with the chemical heat storage material or the clay mineral. The organic binder is mixed for various purposes such as imparting moldability (binding component) when forming the heat storage material structure, crystal control, and porosity.

  Examples of the organic binder include cellulose resins such as polyvinyl alcohol (PVA) and carboxymethyl cellulose; urethane resins such as aqueous urethane; resin components such as starch and funori; diethylene glycol (DEG), ethanol, D-sorbitol, tri Solvent components such as ethanolamine and diethylamine can be preferably used.

  Further, the mixture (or a molded body thereof) may not be a reaction product directly generated from the chemical heat storage material to be used and the clay mineral, that is, may further include, for example, a silicate having a different metal composition. Good.

  When the mixture is subjected to a molding treatment, the molding method is not particularly limited, and a conventionally known molding method may be selected according to the purpose or the like. As an example of the forming method, press forming using a press plate or the like, a method of forming using a mold such as a mold, or the like can be applied.

-Baking process-
In the firing step of the present invention, the mixture (or a molded product thereof) obtained in the mixing step is a reaction product of a chemical heat storage material and a clay mineral, and a silicate containing at least one alkaline earth metal is fired. Baking is performed by controlling at least one of the baking temperature and the baking time so that at least one of the hydration amount and the dehydration amount (mass basis) when the heat storage and heat release reaction is performed is increased. Specifically, the firing temperature is controlled in a temperature range of 600 ° C. or more and less than 800 ° C., and at least one of the hydration amount and the dehydration amount (mass basis) when the firing time is subjected to heat storage / heat dissipation reaction after firing is the above-mentioned The silicate is formed by controlling the chemical heat storage material to be mixed so as to be in a range of 60% by mass or more of the total dehydration amount by the dehydration reaction, and firing the mixture obtained in the mixing step.

For example, when calcium hydroxide is used as a chemical heat storage material and sepiolite is used as a clay mineral, CaO and sepiolite produced by the dehydration reaction of calcium hydroxide (Ca (OH) ₂ → CaO + H ₂ O) are 1: 1. It reacts at a degree (mass ratio) to produce melvinite (3CaO · MgO · 2SiO ₂ ) as a silicate. At this time, the predetermined firing temperature is maintained so that the rate of melvinite generation in the firing process is such that the amount of change in the amount of hydration and / or dehydration when subjected to heat storage and heat dissipation after firing is increased. Time (baking time) or baking temperature is controlled.
As a ratio at which the change width of the amount of hydration / dehydration becomes large, it is preferable that the mass ratio of the silicate (for example, merbinite) in the fired structure to the chemical heat storage material is in the range of 1 to 15% by mass. When the mass ratio is 1% by mass or more, the structure strength is maintained to such an extent that warpage or cracking does not occur during the heat storage / radiation reaction, and when the mass ratio is 15% by mass or less, Excellent dehydration reaction.

  The firing temperature is preferably 600 ° C. or higher in terms of structure strength, and is preferably controlled in a temperature range of 600 ° C. or higher and lower than 800 ° C. This temperature range refers to the temperature range of the atmosphere in which firing is performed, and is adjusted by measuring the ambient temperature and adjusting the ambient temperature.

  By firing at a high temperature range of 600 ° C. or higher, it is possible to increase the strength of the structure, and at the same time, the heat storage / heat dissipation reactivity tends to decrease, but in the present invention, the firing time and / or firing temperature is controlled. By doing so, the effect of improving the reactivity in such a temperature region, that is, the effect of improving the heat storage / heat radiation reaction efficiency, which tends to be reduced by firing, is great. Therefore, heat storage and heat dissipation are also high while having strength that does not cause warping or cracking. Further, when the firing temperature is less than 800 ° C., the coarsening of crystal grains due to sintering is suppressed, and the productivity of the reaction product can be maintained, so that the effect of improving the structure strength can be further expected.

Among the above, the firing temperature is preferably in the temperature range of 700 ° C. or higher and lower than 800 ° C. When the calcination temperature is 700 ° C or higher, the reaction between the decomposition product derived from the chemical heat storage material (for example, CaO generated by the dehydration reaction of Ca (OH) ₂ → CaO + H ₂ O in the case of calcium hydroxide) and clay minerals It is easy to proceed and further improvement in the structural strength of the structure can be expected.

The firing time can be appropriately selected according to various conditions such as firing temperature, scale, type of chemical heat storage material and clay mineral, and mixing ratio. As the firing time, in the above temperature range, the amount of hydration and / or dehydration (mass basis) when the heat storage and heat release reaction is performed after firing is the total dehydration when the dehydration reaction of the chemical heat storage material is completely performed. The aspect controlled in the range of 60 mass% or more with respect to quantity is preferable. By stopping the firing when the amount of hydration / dehydration reaches 60% by mass of the total dehydration amount, the strength to withstand warping and cracking is maintained, but the amount of chemical heat storage material is suppressed to an extent that it does not decrease too much.・ The heat dissipation can be improved.
In particular, for the same reason as described above, the firing time is preferably controlled in the temperature range so that the amount of hydration / dehydration of the chemical heat storage material is 80% by mass or more of the total amount of dehydration.

  This amount of dehydration occurs during firing based on basic data such as the amount of dehydrated clay minerals and the amount of dehydrated mass (mass) of chemical heat storage materials that are dehydrated under each heating condition (temperature, time). It is possible to calculate from the weight change.

(Silicate)
The chemical heat storage material structure in the present invention preferably contains one or more silicates produced by reaction from the chemical heat storage material and the clay mineral after firing. In addition to adding clay minerals to the chemical heat storage material, silicate can be present by firing at a high temperature of 600 ° C. or higher, more preferably 700 ° C. or higher. Due to the presence of silicate, the structural strength of the structure is improved.

  The silicate in the present invention is preferably a composite silicate compound containing one or more of the alkaline earth metals present in the chemical heat storage material and the clay mineral, for example, in the form of an oxide.

Examples of the silicate include calcium magnesium silicate (melvinite; = 3CaO · MgO · 2SiO ₂ ), calcium aluminum silicate, lithium calcium silicate, lithium magnesium silicate, calcium silicate (CaSiO ₃ ), magnesium metasilicate (MgSiO ₃ ), and orthosilicate. Examples thereof include magnesium (Mg ₂ SiO ₄ ) and magnesium trisilicate (Mg ₂ Si ₃ O ₈ ).

When melvinite (3CaO · MgO · 2SiO ₂ ) is included as a silicate, for example, calcium hydroxide is used as a chemical heat storage material, sepiolite is used as a clay mineral, and these are mixed (preferably in a temperature range of 600 ° C. or higher and lower than 800 ° C. ) It can be produced by firing and coexist with calcium hydroxide and sepiolite by controlling the firing temperature and / or firing time as described above. A structure that is produced when fired in a mixed state and can exist uniformly between the heat storage material and the clay mineral, so that a large number of pores are formed and structured in a network (eg, porous) Further, it is possible to give elastic deformation that can absorb volume change and to increase the structural strength that can withstand the endothermic reaction.

As content in the structure after baking of a silicate, the range of 5-30 mass% is preferable with respect to Ca (OH) ₂ . When the content of the silicate is 5 mass or more, it exhibits elastic deformation behavior, and a structural strength that can alleviate the influence of volume change accompanying heat absorption and heat generation during heat storage and heat release reaction is obtained, and it is 30 mass% or less. It is advantageous in terms of heat storage and heat release reactivity.

-Dehydration process-
The method for producing a chemical heat storage material structure of the present invention preferably includes a dehydration step in which the chemical heat storage material is subjected to a dehydration reaction in a temperature range of less than 600 ° C. in advance before the firing step of performing the firing. By performing dehydration in advance in a temperature range where firing is not performed, the diameter of the chemical heat storage material can be reduced, clearance from the clay mineral can be achieved, and the contact interface with the clay mineral can be reduced. Thereby, the amount of silicate generated by the reaction between the two can be suppressed.
If it does in this way, while maintaining the high intensity | strength which does not produce a curvature, a crack, etc., the improvement of thermal storage and a thermal radiation reactivity can be aimed at.

Dehydration can be performed by heating the ambient temperature.
The dehydration temperature in the dehydration step is set to a temperature range of less than 600 ° C. When the temperature is lower than 600 ° C., it indicates that the temperature is not the temperature for sintering, and the chemical heat storage material can be dehydrated prior to sintering. In this case, since the dehydration temperature of Ca (OH) ₂ is 350 ° C. to 500 ° C., for example, Ca (OH) ₂ is suitable when including the dehydration step.

Dehydration is a range in which the ratio of the amount of dehydration of the chemical heat storage material to the dry mass of the mixture obtained in the mixing step is within 50% by mass of the total amount of dehydration generated by the dehydration reaction of the chemical heat storage material before dehydration. Preferably. By stopping the ratio of the amount of dehydration to the amount of mixed substances in the dehydration step within 50% by mass of the total amount of dehydration, the silicate formation can be suppressed to some extent. As a result, it is possible to maintain the excellent heat storage and heat dissipation properties while maintaining the strength to withstand warpage and cracking while maintaining the amount of the chemical heat storage material not reduced excessively during firing.
Among these, for the same reason as described above, an embodiment in which dehydration is performed while keeping the amount within 20% by mass of the total dehydration amount is more preferable.
The lower limit is preferably 1% by mass in terms of heat storage and heat dissipation. More preferably, it is the range of 1 mass% or more and 20 mass% or less of the total dehydration amount.

  As with the above, this dehydration amount is based on the basic data such as the known dehydration amount of clay minerals and the dehydration amount (mass) of the chemical heat storage material that is dehydrated under each heating condition (temperature, time). In addition, it is possible to calculate from the weight change occurring during firing.

  Moreover, it is preferable to perform dehydration in a range in which the volume reduction rate of the chemical heat storage material before dehydration is within 20%. The volume of the chemical heat storage material is reduced by dehydration, but if the reduction rate is kept within 20%, the reactivity with the clay mineral will be maintained, but the contact interface with the clay mineral will be reduced. The amount of silicate produced by this reaction is moderately suppressed. This maintains the strength of the structure that can avoid warping, cracking, and the like during heat absorption and heat generation, but it is also possible to improve heat storage and heat dissipation reactivity more suitably.

  Among these, for the same reason as described above, it is more preferable to dehydrate the chemical heat storage material while keeping the volume reduction rate within a range of 10% or less. More preferably, the volume reduction rate is in the range of 1% to 10%.

  The volume reduction rate of the chemical heat storage material is a value obtained by dividing the reduced mass after dehydration by the total mass before dehydration (reduced mass after dehydration / total mass before dehydration).

  In the present invention, in particular, alkaline earth metal hydroxide (especially calcium hydroxide) is used as the chemical heat storage material, sepiolite is used as the clay mineral, and the dehydration treatment is performed in the temperature range of 350 ° C. to 500 ° C. in advance. After applying so as to satisfy the range in which the ratio of the amount is within 20% by mass of the total dehydrated amount or the range in which the following volume reduction rate is 1% or more and 10% or less, firing is performed at a temperature range of 700 ° C. or more and less than 800 ° C. The mode of treatment is particularly preferred.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1
Using a micro thermogravimetric measuring device TGA-50 (manufactured by Shimadzu Corporation) using a thermogravimetric method, treatment such as dehydration and firing is performed as shown in FIG. A structure was produced. In addition, FIG. 1 is a graph obtained by the measuring apparatus TGA-50.

-1. Mixing
Calcium hydroxide (Ca (OH) ₂ ) white powder (JIS R9001 grade: special name) is prepared as a chemical heat storage material, and Mira clay (registered trademark) P series manufactured by Omi Mining Co., Ltd. sepiolite _{P-300 (MgSi 12 O 30} (OH) 4 (OH 2) 4 · 8H 2 O; fibrous) was prepared. These were mixed so that the sepiolite concentration was 10% by mass with respect to the total mass after mixing to obtain a mixed powder.

-2. Removal of adsorbed water
Next, the obtained mixed powder was placed in an air atmosphere chamber, and as shown in (a) in FIG. 1, the adsorbed water was removed by heating at 300 ° C. for 10 minutes. At this time, the mass at point p in FIG. 2 is the dry mass of the mixed powder after the removal treatment, and this dry mass [mg] was measured.
In addition, in FIG. 2, the mass of the mixed powder before starting a heating is normalized as 0 (zero), and the mass change [mg] after that is shown.

-3. Dehydration
Next, as shown in FIG. 1 (b), a time zone for heat treatment at 500 ° C. for 15 minutes is provided for the mixed powder after removal treatment, and the Ca (OH) ₂ in the mixed powder is dehydrated. gave.
Dehydration reaction: Ca (OH) ₂ → CaO + H ₂ O

At this time, a remarkable mass change was observed as shown in FIG. This mass change was caused by the dehydration reaction of Ca (OH) ₂ , and the mass after dehydration decreased to point r. The mass change amount q (mg; the change amount from the point p to the point r) was measured, and the mass change rate [%] at the time of dehydration was calculated by the following formula (1). Ca (OH) in the mixed powder It was 20% or less of the total dehydrated amount [mg] produced from the total amount of ₂ dehydrated.
Mass change ratio = Mass change q [mg] / {Mass of mixed powder before dehydration after removing adsorbed water [mg]} × 100 (1)

Moreover, when the volume reduction rate [%] of the Ca (OH) ₂ powder at this time was determined from the following formula (2), it was 15%.
Volume reduction rate = volume of Ca (OH) ₂ after dehydration / volume of Ca (OH) ₂ before dehydration × 100 (2)

-4. Firing-
Next, this mixed powder was heated at a heating rate of 50 ° C./min, held at 750 ° C. for 1 minute, and fired in an air atmosphere as shown in FIG. At this time, the temperature lowering rate was 30 ° C./min. By this firing, the mass decreased to point s as shown in FIG. 2, and dehydration was completed at this point.

The mass change amount (mg; change amount from the point r to the point s) at this time was measured, and the mass change rate [%] at the time of firing was estimated by the following formula (3). As a result, a value of 60% or more was shown.
Mass change ratio = mass change amount t [mg] / {total dehydration amount [mg]} × 100 (3) generated by dehydration from the total amount of Ca (OH) ₂ in the mixed powder

The firing is performed in an air atmosphere to completely burn the organic matter in the clay mineral (generation of H ₂ O and CO ₂ , and in the presence of Ca (OH) ₂ , further generated CaCO ₃ is converted to H _2. Decomposed to O and CO ₂ ). As a result, reaction inhibition between the chemical heat storage material and the clay mineral due to the carbonation of Ca was prevented.
As described above, the chemical heat storage material structure of the present invention was obtained.

-5. Evaluation-
Subsequently, the obtained chemical heat storage material structure was maintained at 200 ° C. to cause a hydration reaction. At this time, the mass increased from the point s as shown in FIG. Then, after the atmospheric temperature was heated and held (dehydrated) at 500 ° C. for 15 minutes, the operation of lowering the temperature again and holding (hydrated) at 200 ° C. was repeated two times (time zone (d) in FIG. 1). ).

  As a result, as shown in FIG. 2, after hydration after firing and the mass increased, the mass decreased again to near the point s by dehydration. At this time, the hydration / dehydration reaction by the chemical heat storage material structure proceeds with a mass change t as shown in FIG. 2, and compared with the heat storage material structure of Comparative Example 1 described later, It was possible to dramatically improve heat dissipation.

Furthermore, the production | generation amount and reaction rate of the melvinite (silicate) in the chemical thermal storage material structure of this invention are shown in FIGS. 3-4 compared with the thermal storage material structure of the comparative example 1 mentioned later.
As shown in FIG. 3, in the chemical heat storage material structure of the present invention, the production amount of melvinite is suppressed as compared to the comparative heat storage material structure, and by producing so as to suppress the production of melvinite, As shown in FIG. 4, the reaction rate could be dramatically improved. At this time, the production | generation ratio of the melvinite with respect to ₂ quantity of Ca (OH) contained in a structure was 5 mass%.
Moreover, the chemical heat storage material structure has high strength because it contains melvinite, and no warpage or cracking was observed due to endothermic heat generation.

In the above embodiment, the mixed powder is not formed, but a step of forming, for example, after the dehydration step before firing may be provided. Specifically, for example, the following may be performed.
To the obtained mixed powder, a 2% aqueous solution of polyvinyl alcohol as a binder is added in an amount of 50% of the mixed powder, granulated so that the average particle size is 1 mm or less, and dried. Of these, a desired amount (for example, about 15%) is weighed and molded by uniaxial pressing at room temperature (25 ° C.) to produce a molded body having a desired size. In this case, what is necessary is just to bake with respect to the obtained molded object.

(Comparative Example 1)
In Example 1, instead of dehydration at 500 ° C. for 15 minutes and firing at 750 ° C. for 1 minute, firing is performed at 750 ° C. for 60 minutes as shown by the broken line in FIG. 1 (reaction between the chemical heat storage material and the clay mineral is performed). A comparative heat storage material structure was obtained in the same manner as in Example 1 except that it was not suppressed; see FIG.
Thereafter, following the firing as in Example 1, the obtained chemical heat storage material structure was maintained at 200 ° C. to cause a hydration reaction. At this time, the mass increased from around the point s as shown in FIG. Then, after the atmosphere temperature was heated and held (dehydrated) at 500 ° C. for 15 minutes, the operation of lowering the temperature again and holding (hydrated) at 200 ° C. was repeated two times (time zone (e) in FIG. 1). ).

As a result, as shown in FIG. 2, after hydration after firing and the mass increased, the mass decreased again to near the point s by dehydration. At this time, the hydration / dehydration reaction by the chemical heat storage material structure is accompanied by a mass change t ′ as shown in FIG. Compared with the chemical heat storage material structure (mass change t), the heat storage and heat dissipation were inferior.
Moreover, as FIG. 4 showed, compared with the chemical heat storage material structure of Example 1, it was inferior to the reaction rate (heat storage / heat dissipation reactivity). At this time, the production | generation ratio of the merbinite with respect to ₂ quantity of Ca (OH) contained in a structure was 30 mass%.

Claims (10)

A mixing step of mixing a powdery chemical heat storage material and a clay mineral having a layer ribbon structure;
Chemical heat storage in which the firing temperature is controlled in a temperature range of 600 ° C. or more and less than 800 ° C., and at least one of the hydration amount and the dehydration amount (mass basis) when the firing time is subjected to heat storage / heat dissipation reaction after firing is mixed. Controlling so that the total dehydration amount by the dehydration reaction of the material is in the range of 60% by mass or more, firing the mixture obtained in the mixing step, the reaction product of the chemical heat storage material and the clay mineral, a firing step of silicate containing at least one alkaline earth metal are made form,
A method for producing a chemical heat storage material structure comprising: The baking time, according to claim 1 controlled so that at least one of the hydrated weight and the amount of dehydration when allowed to heat storage, exothermic reaction after firing is in the range of more than 80 wt% of the total amount of dehydration Manufacturing method for chemical heat storage material. The method for producing a chemical heat storage material structure according to claim 1 or 2, further comprising a dehydration step in which the chemical heat storage material is subjected to a dehydration reaction in a temperature range lower than 600 ° C in advance before the firing step. In the dehydration step, dehydration is performed in a range where the ratio of the dehydration amount of the chemical heat storage material to the dry mass of the mixture is within 50% by mass of the total dehydration amount generated by the dehydration reaction of the chemical heat storage material before dehydration. Item 4. A method for producing a chemical heat storage material structure according to Item 3 . The method for producing a chemical heat storage material structure according to claim 4 , wherein the dehydration is performed within a range of 20% by mass or less of the total dehydration amount. The method for producing a chemical heat storage material structure according to claim 3 , wherein the dehydration step performs the dehydration within a range where the volume reduction rate of the chemical heat storage material before the dehydration is within 20%. The method for producing a chemical heat storage material structure according to claim 6 , wherein the dehydration is performed in a range where the volume reduction rate of the chemical heat storage material before dehydration is within 10%. In the said baking process, the mass ratio with respect to the said chemical heat storage material of the said silicate is the range of 1-15 mass%, The manufacturing method of the chemical heat storage material structure of any one of Claims 1-7.   The said chemical heat storage material is a hydroxide of alkaline-earth metal, The manufacturing method of the chemical heat storage material structure of any one of Claims 1-8.   The method for producing a chemical heat storage material structure according to claim 9, wherein the alkaline earth metal is calcium.