Ceramic heat storage unit, method for producing ceramic heat storage unit, and method for estimating composition of ceramic heat storage unit

Abstract

[Problem] To provide an inexpensive, easy-to-produce ceramic heat storage unit that has high thermal efficiency even in a thermally non-equilibrium state such as a regenerative heat storage burner system and is highly maintainable because contaminants do not tend to adhere thereto and the unit is difficult to break due to excellent wear resistance, and a method for producing the ceramic heat storage unit. [Solution] The ceramic heat storage unit 10 comprises mainly alumina and is equipped with a shell 11 having an average absorbance of more than 0.3 at 1.7-2.7 μm, which is the central wavelength of radiant heat of 800-1400°C. Also, the shell 11, in addition to alumina, includes oxides including Cr, Fe, Mn, and Co in an amount of 1 wt% or more in terms of compounds. In addition, the shell 11 is a shell having a spheroidal shape, the outer surface of which includes a sphere, and having a hollow portion inside. Furthermore, in the shell 11, the core temperature of the hollow portion 12 during heat storage is higher than the inner surface temperature of the shell 11.

Description

Ceramic heat storage body, manufacturing method for ceramic heat storage body, and method for estimating the composition of ceramic heat storage body

[0001] The present invention relates to a ceramic thermal storage medium, a method for manufacturing a ceramic thermal storage medium, and a method for estimating the composition of a ceramic thermal storage medium.

[0002] Recently, various measures to achieve energy conservation have been required. For example, regenerative regenerative burners used in industrial furnaces, etc., are burners equipped with a heat exchanger in the intake and exhaust path. They alternate between combustion and exhaust at relatively short intervals, storing the heat of the combustion gas in a regenerative heat storage material on the exhaust side of the burner. On the combustion side of the burner, the combustion air is preheated using the heat stored in the regenerative heat storage material, thereby achieving high thermal efficiency and contributing to energy conservation. Conventionally, solid spheres such as alumina have been used as the regenerative heat storage material filled in the heat exchanger installed in regenerative regenerative burners, etc., but the thermal efficiency of the heat exchanger depends on the performance of the regenerative heat storage material, so the development of a regenerative heat storage material with higher thermal efficiency has been desired.

[0003] In this context, the heat storage medium described in Patent Document 1 comprises an outer shell and a hollow portion formed inside the outer shell, and the outer shell has protrusions that protrude outward from the outer shell and have openings for allowing fluid to circulate between the outside of the outer shell and the hollow portion, thereby increasing the surface area available for heat exchange compared to a solid sphere and achieving high heat storage efficiency.

[0004] Japanese Patent Application Laid-Open No. 2020-70949

[0005] As mentioned above, the development of a heat storage material with higher thermal efficiency is desirable for high-temperature gas heat storage and heat exchange applications, such as regenerative burner systems (hereinafter referred to as regeneration systems). Here, thermal efficiency refers to the amount of heat that can be recovered when heat input and output are repeated under thermally non-equilibrium conditions. That is, when heat storage materials of substantially identical external dimensions are exposed to high temperatures for a limited time and then released, the thermal efficiency can be defined as (thermal efficiency) = (heat storage amount) - (residual heat amount). Commonly used white alumina solid sphere heat storage materials have a decreasing thermal diffusivity with increasing temperature. Therefore, even when repeatedly heated and released under thermally non-equilibrium conditions, only the surface temperature rises, and the interior of the alumina solid sphere is not effectively utilized as a heat storage material. Furthermore, while the thermal diffusivity of many ceramics decreases with increasing temperature, white alumina, in particular, is at a disadvantage because it cannot be expected to transfer heat via radiation. Furthermore, in many regeneration systems, heat storage bodies are exposed to dust and various pollutants contained in exhaust gases in the heat exchanger. If dust, pollutants, etc., accumulate on the large number of heat storage bodies packed in the heat exchanger, the gaps between the individual heat storage bodies, i.e., the air and waste gas passages, become blocked, making heat exchange impossible. Therefore, after a certain period of use, heat exchangers filled with heat storage bodies are maintained by removing the large number of filled heat storage bodies and rubbing them against each other to clean the deposits on the heat storage body surfaces. It is easy to imagine that this maintenance requires a great deal of effort and time. Therefore, to improve maintainability, heat storage bodies whose surfaces are less susceptible to the adhesion of contaminants are desired. Furthermore, when heat storage bodies are rubbed against each other during cleaning, the heat storage bodies themselves are worn down due to abrasion, so heat storage bodies with excellent abrasion resistance are required. The heat storage body described in Patent Document 1 allows fluid to flow through the hollow space formed inside, allowing not only the surface but also the inner surface to be used as a heat transfer area, which is advantageous for short-term heat exchange. On the other hand, the overall heat capacity decreases, which is a disadvantage. Furthermore, the heat storage material described in Patent Document 1 has a complex shape with protrusions, which makes it less maintainable and more prone to breakage than a spherical shape. Furthermore, in recent years, heat storage materials made of non-oxide ceramics such as silicon carbide, which have excellent thermal conductivity, have also been put to practical use.However, compared to oxide ceramics such as alumina, they are generally more expensive, and there are still issues such as oxidation progressing and deterioration of properties when used for long periods in high-temperature atmospheres, so there are many unknowns regarding their application to ceramic heat storage materials.

[0006] Therefore, the object of the present invention is to provide a ceramic heat storage body that has high thermal efficiency even in thermally non-equilibrium states such as regeneration systems, is difficult for contaminants to adhere to, has high strength and excellent wear resistance, and is therefore easy to maintain, inexpensive, and easy to manufacture, as well as a method for manufacturing such a ceramic heat storage body, and a method for estimating the composition of a ceramic heat storage body that can contribute to such manufacturing method.

[0007] To achieve the above object, the invention described in claim 1 is characterized in that the ceramic heat storage medium is primarily composed of alumina and has an average absorbance of greater than 0.3 at 1.7 to 2.7 μm, the central wavelength of radiant heat at 800 to 1400°C. The invention described in claim 2 is characterized in that the ceramic heat storage medium contains at least 1 wt% of a compound other than alumina in terms of compound. The invention described in claim 3 is characterized in that the compound contains at least one of Cr, Fe, Mn, Co, Ti, Ca, Zr, Hf, and Ta. The invention described in claim 4 is characterized in that the compound is a carbide, oxide, nitride, or a mixture thereof. The invention described in claim 5 is characterized in that the shell has a spheroidal outer surface including a sphere and a hollow portion inside. The invention described in claim 6 is characterized in that, when the average outer diameter of the shell is D and the average diameter of the hollow portion is d, d is smaller than (D - 8) mm. The invention described in claim 7 is characterized in that the outer surface is a spheroidal shape including a sphere and the solid body has an average outer diameter of 13 mm or less. The invention described in claim 8 is characterized in that, in the above-mentioned configuration, the temperature at the center of the hollow portion is higher than the temperature at the inner surface of the shell during heat storage. The invention described in claim 9 is characterized in that the compound is Co ３ O ４ , Fe ３ O ４ and MnO２ Including Co ３ O ４ The content is 2% by weight or more and 6% by weight or less, and Fe ３ O ４ The content is 2% by weight or more and 6% by weight or less, and MnO ２The invention described in claim 10 is a method for manufacturing a ceramic thermal storage medium, comprising the steps of: injecting a slurry containing ceramic powder and a dispersion medium into a molding die having a shell shape without an opening; forming a molded body having a shell and a hollow portion formed inside the shell by allowing the molding die to absorb the dispersion medium; releasing the molded body from the molding die; and drying the released molded body and firing it to obtain a ceramic thermal storage medium. The invention described in claim 11 is characterized in that, in the above configuration, the dimensional variation with respect to the average outer diameter of the shell is within ±1 mm. The invention described in claim 12 is a method for manufacturing a ceramic heat storage body having the above-mentioned configuration for manufacturing a ceramic heat storage body having alumina as its main component and further containing one or more compounds other than alumina, and includes: a sample data input reception step in which a computer receives input regarding the correspondence between the composition and emissivity relating to at least one of the amount of alumina and the type and amount of the compound obtained for each sample by manufacturing a plurality of samples in which the amount of alumina and the type and amount of the compound differ from each other and measuring the emissivity of each sample; an objective function acquisition step in which a computer obtains a relative emissivity parameter as an objective function with composition as a variable from the plurality of correspondence relationships between the composition and emissivity of the input sample using mathematical programming; and a composition estimation step in which a computer estimates an estimated value of a composition whose relative emissivity parameter exceeds that of any sample, and the injection step and subsequent steps are carried out using the estimated composition value.The invention described in claim 13 is a method for estimating the composition of a ceramic thermal storage medium, which estimates the amount of alumina and the type and amount of compounds in a ceramic thermal storage medium containing alumina as a main component and one or more compounds other than alumina. The method includes: a sample data input receiving step in which a computer receives input of the correspondence between the composition and emissivity obtained for each sample by manufacturing multiple samples with different compositions and measuring the emissivity of each sample; an objective function acquisition step in which the computer acquires a relative emissivity parameter as an objective function with composition as a variable from the multiple correspondence between the composition and emissivity of the input sample using mathematical programming; and a composition estimation step in which the computer estimates the composition whose relative emissivity parameter exceeds that of any sample. The invention described in claim 14 is characterized in that, in the above configuration, the mathematical programming is multiple regression analysis. Note that, in this application, "main component" refers to a component contained in a weight ratio exceeding 80% of the total weight. The term "main component" may refer to a component that accounts for 85% or more by weight of the total weight. The term "main component" may also refer to a component that accounts for 90% or more by weight of the total weight. The term "main component" may also refer to a component that accounts for 95% or more by weight of the total weight. In this application, "no openings" means that openings are not intentionally provided in the shell by drilling or other techniques. In other words, this does not include micropores resulting from the dense structure of fired ceramics. Expressions such as "closed shell" also refer to a state in which the hollow portion is not intentionally connected to the outside of the shell. In reality, the hollow portion may be connected to the outside of the shell by micropores that are invisible to the naked eye.

[0008] The main effects of the present invention are that it has high thermal efficiency even in thermally non-equilibrium conditions such as regeneration systems, is resistant to adhesion of contaminants, has excellent wear resistance and is therefore less susceptible to breakage, making it easy to maintain, is inexpensive and easy to manufacture, and provides a method for manufacturing such a ceramic heat storage medium, as well as a method for estimating the composition of a ceramic heat storage medium that can contribute to such manufacturing method.

[0009] 1 is a cross-sectional view of a ceramic thermal storage medium of the present invention; FIG. 2 is an explanatory diagram showing an example of a mold for manufacturing a ceramic thermal storage medium of the present invention; (a) and (b) are explanatory diagrams showing a manufacturing process of a ceramic thermal storage medium of the present invention; (b) is a flowchart showing a manufacturing process of a ceramic thermal storage medium of the present invention; (c) is a table showing physical quantities of Example 1 and Comparative Example 1; (d) is a graph showing the temperature rise behavior of Example 1 and Comparative Example 1, where (a) shows Example 1 and (b) shows Comparative Example 1; (e) is a graph showing the change in the central temperature and the shell inner surface temperature of Example 1; (f) is a graph showing the heat storage amount behavior of Example 1 and Comparative Example 1; (g) is a graph showing the heat storage efficiency behavior of Example 1 and Comparative Example 1; (h) is a table showing the breakdown and average absorbance of compounds added to Example 2 and Comparative Example 2; (i) is a graph showing the relationship between the shell thickness and the amount of recovered heat and the amount of stored heat in Example 3 and Comparative Example 3, where (a) is the calculation result using a model in which the average absorbance is 0.3, and (b) is the calculation result using a model in which the average absorbance is 0.9; and (i) is a block diagram of a computer capable of implementing the composition estimation method and manufacturing method of a ceramic thermal storage medium of the present invention. 13. A flowchart of an embodiment of a method for estimating the composition of a ceramic thermal storage medium according to the present invention. A table showing the compositions (weight % of each component) of samples (Examples 5-A to 5-K) according to 11 types of compositions that can be used in the example of FIG. 13. A graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Examples 5-A to 5-D. A graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Examples 5-E to 5-H. A graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Examples 5-I to 5-J and Comparative Example 5. A graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Example 5-K and Examples 5-1 to 5-3. Ｋ , yＫ , z Ｋ , v Ｋ , w Ｋ ) and emissivity group (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ 14 ), specific values ​​of composition parameters (x, y, z, v, w) and specific values ​​of relative radiation parameters (X, Y, Z, V, W) for Examples 5-1 to 5-3 whose compositions were estimated by the example of FIG. 13 , and a table showing an example of a multiple regression analysis result for the example of FIG.

[0010] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a cross-sectional view of a ceramic heat storage medium of the present invention. A plurality of ceramic heat storage mediums 10 are filled in a heat storage tank of a regenerative heat storage burner or the like, and are used for storing and exchanging heat with high-temperature gas. As shown in FIG. 1, the ceramic heat storage medium 10 comprises a closed spherical shell 11 made primarily of alumina, and a spherical hollow portion 12 formed inside the shell 11. The shell 11 does not have any openings connecting the hollow portion 12 to the outside of the shell 11, except for minute pores resulting from the dense structure of the ceramic.

[0011] A method for manufacturing the ceramic thermal storage medium 10 will be described below. FIG. 2 is an explanatory diagram showing an example of a mold for manufacturing the ceramic thermal storage medium of the present invention. FIGS. 3(a) and 3(b) are explanatory diagrams showing the manufacturing process of the ceramic thermal storage medium of the present invention. FIG. 4 is a flowchart showing the manufacturing process of the ceramic thermal storage medium of the present invention. The ceramic thermal storage medium 10 can be manufactured by slip casting (cast molding). As shown in FIG. 2, the plaster mold 20 serving as the molding mold comprises an upper half mold 21 having a hemispherical cavity 24a that corresponds to the outer surface shape of the upper side of the shell 11, a lower half mold 22 having a hemispherical cavity 24b that corresponds to the outer surface shape of the lower side of the shell 11, and a lid 23. The plaster mold 20 is made of plaster, which is a permeable material that allows the passage of a predetermined fluid. When the upper half mold 21 and the lower half mold 22 are combined, the cavity 24a and the cavity 24b come together to form a spherical cavity 24 that corresponds to the outer surface shape of the shell 11 of the ceramic thermal storage medium 10. The upper half mold 21 also has an injection hole 25 formed therein for injecting a slurry containing the ceramic that constitutes the shell 11 of the ceramic thermal storage medium 10 into the cavity 24 of the plaster mold 20. The injection hole 25 is drilled above the upper end of the cavity 24a and extends in the vertical direction. The lid 23 is used to close the injection hole 25 from the outside.

[0012] To form the ceramic heat storage body 10, first, a ceramic powder containing alumina that constitutes the shell 11 is mixed with a dispersion medium to obtain a slurry. The obtained slurry is injected into the cavity 24 of the plaster mold 20 through the injection hole 25 (injection step S1), and the injection hole 25 is closed with a lid 23 as shown in FIG. 3( a). The plaster mold 20 allows the dispersion medium to pass through. When the plaster mold 20 is left stationary with the slurry injected for a predetermined time, the dispersion medium in the slurry is absorbed into the plaster mold 20, as shown by the arrows in FIG. 3( b). As the dispersion medium is absorbed into the plaster mold 20, the ceramic powder dispersed in the dispersion medium moves and deposits with a substantially uniform thickness on the outer surface of the cavity 24 (the inner surface of the plaster mold 20). This results in a molded shell 11 having a hollow portion 12 inside (molding step S2). The molded body is released from the plaster mold 20 (demolding step S3), and then dried and fired (drying step S4) to produce the ceramic thermal storage body 10. In this way, the ceramic thermal storage body 10 having a closed shell 11 with a hollow portion 12 therein can be easily produced by simply injecting a slurry containing a ceramic powder and a dispersion medium into the plaster mold 20 and leaving it to stand. Furthermore, by using the plaster mold 20 to produce the ceramic thermal storage body 10, the dimensional variation of the produced ceramic thermal storage body 10 is within ±1 mm. Therefore, it is possible to produce a ceramic thermal storage body 10 with a stable shape. The obtained ceramic thermal storage body 10 may have small holes on its outer surface that represent the injection traces from the injection step S1. In this case, the diameter of the holes representing the injection traces is preferably smaller than the average diameter of the hollow portion 12.

[0013] [Example 1 and Comparative Example 1] Hereinafter, Example 1 produced by the above-mentioned production method and Comparative Example 1 not belonging to the present invention will be described. Note that the present invention is not limited to these Examples.

[0014] The ceramic heat storage body 10 of Example 1 was manufactured by the following method. The ceramic heat storage body 10 of Example 1 was manufactured by adding Cr as an additive to AES-12 (manufactured by Sumitomo Chemical Co., Ltd.) containing alumina as ceramic powder. ２ O ３ , Fe ３ O ４, Mn ２ O ３ A mixture of AES-12 and CoO was used. In Example 1, AES-12 was mixed at 92 wt % and additives at 8 wt % (each compound was mixed at 2 wt %). The dispersion medium used to obtain the slurry consisted of Cerna D-305 (manufactured by Chukyo Yushi Co., Ltd.) as a dispersant at the same weight percentage as the ceramic powder, and distilled water at half the weight percentage of the ceramic powder. Note that equivalent performance can be obtained using ceramic powder other than AES-12, such as SA-34 (manufactured by Nippon Light Metal Co., Ltd.). First, the ceramic powder was mixed with Cerna D-305 at the same weight percentage as the ceramic powder and distilled water at half the weight percentage of the ceramic powder, and the mixture was degassed to obtain a slurry. At this time, the solid concentration of the slurry was approximately 32% by volume. The obtained slurry was poured into the cavity 24 of the plaster mold 20. The slurry was poured into the plaster mold 20, and the plaster mold 20 was left standing with the pouring hole 25 closed with the lid 23. After a predetermined time had passed, the mold was turned upside down and left standing for another predetermined time. The dispersion medium was sufficiently absorbed into the plaster mold 20, and AES-12 was applied to the outer surface of the cavity 24, obtaining a molded body. The molded body was released from the plaster mold 20 and then dried for a predetermined time. After drying, the molded body was fired at 1600°C to obtain the ceramic thermal storage medium 10 of Example 1. The obtained ceramic thermal storage medium 10 had a black shell 11 and a hollow portion 12.

[0015] Comparative Example 1 is a conventional ceramic heat storage medium made of alumina, which is manufactured by a known method and has a white solid spherical shape.

[0016] First, the physical quantities of Example 1 and Comparative Example 1 are compared. Fig. 5 is a table showing the physical quantities of Example 1 and Comparative Example 1. Example 1 has a weight of 19.40 g, an outer diameter of 23.66 mm, an average thickness of the shell 11 of 3.80 mm, and a density of 2.80 g / cm ３ Comparative Example 1 had a weight of 12.90 g, an outer diameter of 19.21 mm, and a density of 3.47 g / cm ３As described above, the density of Example 1 is about 4 / 5 of the density of Comparative Example 1. That is, Example 1 is lighter than the conventional product (Comparative Example 1) by providing a hollow portion 12 inside the shell 11. Therefore, when a plurality of ceramic heat storage bodies 10 are filled in a heat storage tank of a regenerative heat storage burner or the like, Example 1 prevents damage to the ceramic heat storage bodies 10 located at the bottom of the heat storage tank due to the weight of the ceramic heat storage bodies 10 located at the top of the heat storage tank.

[0017] Next, an FTIR instrument (Perkin Elmer, System 2000) was used to measure the FTIR spectrum in the range of 370 to 7800 cm －１ (effective range 400-6000cm －１ ), the reflectance of Example 1 and Comparative Example 1 at room temperature was measured, and the average absorbance at 1.7 to 2.7 μm, which is the central wavelength of radiant heat in the typical temperature range of 800 to 1400 ° C used for heat storage bodies, was calculated. As a result of the measurement, the average absorbance at wavelengths of 1.7 to 2.7 μm for Example 1 was 0.80. The average absorbance of Comparative Example 1 was 0.24 (see Example 2-1 and Comparative Example 2-1 in FIG. 10). Therefore, Example 1, which was produced by adding an additive to alumina, has a very high average absorbance at 1.7 to 2.7 μm, which is the central wavelength of radiant heat in the typical temperature range of 800 to 1400 ° C used for heat storage bodies.

[0018] Next, the thermal behavior of Example 1 and Comparative Example 1 will be compared. FIG. 6 is a graph showing the temperature rise behavior of Example 1 and Comparative Example 1, with (a) showing Example 1 and (b) showing Comparative Example 1. FIG. 7 is a graph showing the change in the center temperature and the temperature of the inner shell surface of Example 1. FIG. 8 is a graph showing the heat storage amount behavior of Example 1 and Comparative Example 1. FIG. 9 is a graph showing the heat storage efficiency behavior of Example 1 and Comparative Example 1. For the thermal behavior, Example 1 and Comparative Example 1 were heated with a gas burner, and the temperature of each part was measured using a thermocouple. The temperature of the gas burner was adjusted to an average of 1,300°C at a position 30 mm away from the outer surface of Example 1 and Comparative Example 1.

[0019] First, Example 1 and the comparative example were heated with a gas burner, and the temperature change of the outer surface over time was measured. As shown in FIG. 6(a), the outer surface temperature of Example 1 reached approximately 750°C after 30 seconds of heating. As shown in FIG. 6(b), the outer surface temperature of Comparative Example 1 reached approximately 580°C after 30 seconds of heating. Thus, Example 1 exhibited a temperature value more than 100°C higher than Comparative Example 1. This is thought to be due to the fact that the average absorbance of Comparative Example 1 was 0.24, while the average absorbance of Example 1 was very high at 0.80, which is believed to be due to the efficient absorption of radiant energy emitted from the gas burner flame. In other words, Example 1, which was manufactured by adding an additive to alumina, has higher thermal efficiency.

[0020] Next, Example 1 was heated with a gas burner, and the changes in the central temperature of the hollow portion 12 and the temperature of the inner surface of the shell 11 over time during heating were measured. Three measurements were performed. As a result, as shown in FIG. 7 , in all the measurements, Example 1 exhibited a behavior in which the central temperature of the hollow portion 12 remained higher than the inner surface temperature of the shell 11. This is thought to be due to the fact that Example 1 was manufactured by mixing additives into ceramic powder, resulting in a surface with high average absorbance not only on the outer surface but also on the inner surface of the shell 11. Therefore, in Example 1, when heated (during heat storage), the central temperature of the hollow portion 12 became higher than the inner surface temperature of the shell 11, and it is thought that the temperature of the hollow portion 12 was transferred to the shell 11, thereby increasing the outer surface temperature of the shell 11. In other words, Example 1, which was manufactured by adding additives to alumina, exhibited higher thermal efficiency because the central temperature of the hollow portion 12 was higher than the inner surface temperature of the shell 11.

[0021] Next, Example 1 and Comparative Example 1 were heated with a gas burner, and the change in heat storage capacity over time was measured. The outer surface temperature was used to calculate the heat storage capacity. As a result, as shown in FIG. 8 , the heat storage capacity of Example 1 was 7.78 kJ after a heating time of 30 seconds. The heat storage capacity of Comparative Example 1 was 4.11 kJ after a heating time of 30 seconds. Therefore, Example 1 can store heat more efficiently than Comparative Example 1. This is thought to be because Example 1 has a hollow portion 12 inside the shell 11, which eliminates the central area of ​​Comparative Example 1, which could not be used for heat storage after a heating time of about 30 seconds due to heat transfer efficiency, thereby increasing the effective heat storage volume. In other words, Example 1 has high thermal efficiency. In particular, Example 1, which was manufactured by adding an additive to alumina, has a high average absorbance and therefore has higher thermal efficiency.

[0022] Next, the heat storage efficiency over time was calculated from the change in the heat storage amount in Example 1 and Comparative Example 1. As a result, as shown in FIG. 9 , the heat storage efficiency of Example 1 was 0.85 after a heating time of 30 seconds. The heat storage efficiency of Comparative Example 1 was 0.45 after a heating time of 30 seconds. Therefore, Example 1 has a higher heat storage efficiency than Comparative Example 1. In particular, Example 1, which was manufactured by adding an additive to alumina, has a higher heat storage efficiency because it can also absorb radiant energy emitted from the flame of the gas burner and use it for heat storage. In other words, Example 1 has a high thermal efficiency. In particular, Example 1, which was manufactured by adding an additive to alumina, has a high average absorbance and therefore a higher thermal efficiency.

[0023] The first embodiment, configured as described above, is primarily composed of alumina and has an average absorbance of greater than 0.3 at 1.7 to 2.7 μm, the central wavelength of radiant heat at 800 to 1400°C. Furthermore, in addition to alumina, the first embodiment also contains 1 wt. % or more of oxides containing Cr, Fe, Mn, and Co, calculated as compounds. Furthermore, the first embodiment has a shell with a spheroidal outer surface including a sphere and a hollow interior. Furthermore, during heat storage, the central temperature of the hollow interior 12 is higher than the inner temperature of the shell 11. Therefore, the first embodiment has a high average absorbance, resulting in high thermal efficiency even in thermally non-equilibrium conditions such as regeneration systems. Furthermore, the first embodiment is highly maintainable due to its resistance to breakage. Furthermore, while offering high performance, it can be easily manufactured at low cost by simply adding readily available oxides.

[0024] Moreover, Example 1 is manufactured by a manufacturing method including an injection step S1 of injecting a slurry containing ceramic powder, a dispersant, and water into a plaster mold 20 having the shape of a shell 11 without an opening, a molding step S2 of making the plaster mold 20 absorb the dispersant and water to obtain a molded body including the shell 11 and a hollow portion 12 formed inside the shell 11, a demolding step S3 of releasing the molded body from the plaster mold 20, and a drying step S4 of drying or firing the released molded body. Thus, a ceramic heat storage body 10 including a closed shell 11 having a hollow portion 12 inside can be easily manufactured.

[0025] [Example 2 and Comparative Example 2] Next, Example 2 (Examples 2-1 to 2-12) produced by the above-mentioned production method and containing additives containing various compounds, and Comparative Example 2 (Comparative Examples 2-1 to 2-4) not belonging to the present invention will be described below. Note that the present invention is not limited to these examples. Figure 10 is a table showing the breakdown of compounds in Example 2 and Comparative Example 2 and the average absorbance.

[0026] Comparative Example 2-1 is a conventional ceramic heat storage medium made of alumina, which is manufactured by a known method and has a white solid spherical shape.

[0027] In Comparative Example 2-2, AES-12 was used as the ceramic powder and Fe was used as the additive. ２O ３ It was prepared in the same manner as in Example 2-1, except that the compound (0.1% by weight) was added.

[0028] Comparative Example 2-3 uses AES-12 as the ceramic powder and Fe as the additive. ２ O ３ (0.2% by weight), Fe ３ O ４ (0.2% by weight), TiO ２ It was prepared in the same manner as in Example 2-1, except that a mixture of SiO2 (0.2 wt%) and CoO (0.2 wt%) was used.

[0029] Comparative Example 2-4 uses AES-12 as the ceramic powder and Fe as the additive. ２ O ３ (0.6% by weight), Fe ３ O ４ (0.1 wt%) and Cr ２ O ３ It was prepared in the same manner as in Example 2-1, except that a mixture of (0.2 wt %) was added.

[0030] Example 2-1 is manufactured in the same manner as Example 1.

[0031] In Example 2-2, AES-12 was used as the ceramic powder and Fe was used as the additive. ３ O ４ It was prepared in the same manner as in Example 2-1, except that a mixture of SiO2 (2 wt%) and CaO (6 wt%) was added.

[0032] In Example 2-3, AES-12 was used as the ceramic powder and Cr was used as the additive. ２ O ３ (4 wt%) and Mn ２ O ３ It was prepared in the same manner as in Example 2-1, except that a mixture of (3% by weight) was added.

[0033] In Example 2-4, the ceramic powder was AES-12, and CoO (4 wt%) and Cr were added as additives. ２ O ３ It was prepared in the same manner as in Example 2-1, except that a mixture of (8% by weight) was added.

[0034] In Example 2-5, AES-12 was used as the ceramic powder and Fe was used as the additive. ２ O ３ It was prepared in the same manner as in Example 2-1, except that the compound (2% by weight) was added.

[0035] In Example 2-6, the ceramic powder was AES-12, and CoO (4 wt%) and Mn were added as additives. ２ O ３ It was prepared in the same manner as in Example 2-1, except that a mixture of (4% by weight) was added.

[0036] In Example 2-7, AES-12 was used as the ceramic powder, and Fe was used as the additive. ２ O ３ It was prepared in the same manner as in Example 2-1, except that a mixture of TiN (3 wt%) and TiN (3 wt%) was used.

[0037] Example 2-8 was produced in the same manner as Example 2-1, except that AES-12 with TiC (3 wt %) added as an additive was used as the ceramic powder.

[0038] Example 2-9 was produced in the same manner as Example 2-1, except that AES-12 with ZrC (3 wt %) added as an additive was used as the ceramic powder.

[0039] Example 2-10 was produced in the same manner as Example 2-1, except that AES-12 with HfC (3 wt %) added as an additive was used as the ceramic powder.

[0040] Example 2-11 was produced in the same manner as Example 2-1, except that AES-12 with TaC (3 wt %) added as an additive was used as the ceramic powder.

[0041] Example 2-12 was produced in the same manner as Example 2-1, except that AES-12 containing HfC (1 wt %) as an additive was used as the ceramic powder.

[0042] For Examples 2-1 to 2-12 and Comparative Examples 2-1 to 2-4, an FTIR device (Perkin Elmer, System 2000) was used in the measurement range of 370 to 7800 cm －１ (effective range 400-6000cm －１ ), the reflectance of Example 1 and Comparative Examples 1-1 to 1-2 at room temperature was measured, and the average absorbance at 1.7 to 2.7 μm, which is the central wavelength of radiant heat at 800 to 1400 ° C., which is a typical temperature range for use of the heat storage body, was calculated.

[0043] As a result of the measurement, as shown in Fig. 10, the average absorbance of Comparative Example 2-1 was 0.24, the average absorbance of Comparative Example 2-2 was 0.25, the average absorbance of Comparative Example 2-3 was 0.26, and the average absorbance of Comparative Example 2-4 was 0.27.

[0044] On the other hand, the average absorbance at wavelengths of 1.7 to 2.7 μm for Example 2-1 was 0.80. The average absorbance for Example 2-2 was 0.75. The average absorbance for Example 2-3 was 0.67. The average absorbance for Example 2-4 was 0.66. The average absorbance for Example 2-5 was 0.56. The average absorbance for Example 2-6 was 0.54. The average absorbance for Example 2-7 was 0.54. The average absorbance for Example 2-8 was 0.52. The average absorbance for Example 2-9 was 0.45. The average absorbance for Example 2-10 was 0.48. The average absorbance for Example 2-11 was 0.46. The average absorbance for Example 2-12 was 0.40.

[0045] Therefore, Examples 2-1 to 2-12, which were manufactured by adding 1% by weight or more of additive to alumina, have an average absorbance of greater than 0.3 at 1.7 to 2.7 μm, which is the central wavelength of radiant heat in the typical temperature range of 800 to 1400 ° C. for heat storage.

[0046] Example 2, configured as described above, is primarily composed of alumina and has an average absorbance of greater than 0.3 at 1.7 to 2.7 μm, the central wavelength of radiant heat at 800 to 1400°C. Furthermore, Example 2 contains, in addition to alumina, at least one of Cr, Fe, Mn, Co, Ti, Ca, Zr, Hf, and Ta, and contains 1 wt. % or more of a compound that is either a carbide, an oxide, or a nitride, or a mixture thereof, in compound equivalent. Furthermore, Example 2 has a spheroidal shape with an outer surface that includes a sphere and a shell with a hollow interior. Therefore, Example 2 has a high average absorbance at 1.7 to 2.7 μm, the central wavelength of radiant heat at 800 to 1400°C, and therefore has high thermal efficiency even in thermally non-equilibrium conditions such as regeneration systems. It has also been revealed that ceramic heat storage bodies using compounds containing carbides and nitrides as additives have high thermal efficiency.

[0047] Moreover, Example 2 (and Comparative Examples 2-2 to 2-4) are manufactured by a manufacturing method including an injection step S1 in which a slurry containing ceramic powder, a dispersant, and water is injected into a plaster mold 20 having the shape of a shell 11 without an opening; a molding step S2 in which the dispersant and water are absorbed into the plaster mold 20 to obtain a molded body including the shell 11 and a hollow portion 12 formed inside the shell 11; a demolding step S3 in which the molded body is released from the plaster mold 20; and a drying step S4 in which the released molded body is dried or fired. Therefore, a ceramic heat storage body 10 including a closed shell 11 having a hollow portion 12 inside can be easily manufactured. Note that Comparative Examples 2-2 to 2-4 belong to the present invention in terms of the manufacturing method.

[0048] [Example 3 and Comparative Example 3] Next, the following describes the calculation results of the relationship between shell thickness and heat storage amount and heat recovery amount using a simulation model simulating the ceramic heat storage body 10 manufactured by the above manufacturing method, and describes Example 3 (Examples 3-1 to 3-5) and Comparative Example 3 (Comparative Examples 3-1 to 3-5) that does not belong to the present invention. Note that the present invention is not limited to these examples. Figure 11 is a graph showing the relationship between shell thickness and heat recovery amount and heat storage amount in Example 3 and Comparative Example 3, where (a) is the calculation result for a model in which the average absorbance is 0.3, and (b) is the calculation result for a model in which the average absorbance is 0.9.

[0049] Comparative Example 3 is a simulation model simulating a conventional ceramic heat storage medium made of alumina, and Comparative Example 3-1 was a hollow sphere with an average absorbance of 0.9, an outer diameter of 21 mm, and a shell thickness of 2 mm.

[0050] In Comparative Example 3-2, the shell thickness was set to 4 mm.

[0051] In Comparative Example 3-3, the shell thickness was set to 6 mm.

[0052] In Comparative Example 3-4, the shell thickness was set to 8 mm.

[0053] In Comparative Example 3-5, the shell thickness was set to 10.5 mm, i.e., Comparative Example 3-5 imitated a solid sphere.

[0054] Example 3 is a simulation model simulating a ceramic heat storage body 10 manufactured in the same manner as in Examples 1 and 2, and in Example 3-1, it was a hollow sphere with an average absorbance of 0.9, an outer diameter of 21 mm, and a shell thickness of 2 mm.

[0055] In Example 3-2, the shell thickness was set to 4 mm.

[0056] In Example 3-3, the shell thickness was set to 6 mm.

[0057] In Example 3-4, the shell thickness was set to 8 mm.

[0058] In Example 3-5, the shell thickness was set to 10.5 mm, i.e., Example 3-5 resembled a black solid sphere.

[0059] Assuming the operating conditions of the regeneration system, a convective heat transfer coefficient was given to the outer surface of the heat storage sphere (1096 Nm3 / h during heat storage, 963 Nm3 / h during heat dissipation), and the sphere was exposed to ambient temperature conditions of 1200°C during heat storage and 20°C during heat dissipation for 30 seconds each. The temperature distribution within one heat storage sphere in the filling tank was determined by heat transfer simulation, and the amount of heat stored and the amount of heat recovered were calculated from the determined temperature distribution.

[0060] As a result of the calculation, as shown in FIG. 11(a), in Comparative Example 3-1, the heat storage amount was 7.83 (kJ) and the heat recovery amount was 6.99 (kJ). In Comparative Example 3-2, the heat storage amount was 10.70 (kJ) and the heat recovery amount was 7.67 (kJ). In Comparative Example 3-3, the heat storage amount was 11.64 (kJ) and the heat recovery amount was 7.37 (kJ). In Comparative Example 3-4, the heat storage amount was 11.91 (kJ) and the heat recovery amount was 7.18 (kJ). In Comparative Example 3-5, the heat storage amount was 11.95 (kJ) and the heat recovery amount was 7.13 (kJ).

[0061] On the other hand, as shown in FIG. 11(b), in Example 3-1, the heat storage amount was 8.25 (kJ) and the heat recovery amount was 7.45 (kJ). In Example 3-2, the heat storage amount was 11.94 (kJ) and the heat recovery amount was 8.75 (kJ). In Example 3-3, the heat storage amount was 13.19 (kJ) and the heat recovery amount was 8.55 (kJ). In Example 3-4, the heat storage amount was 13.55 (kJ) and the heat recovery amount was 8.34 (kJ). In Example 3-5, the heat storage amount was 13.61 (kJ) and the heat recovery amount was 8.29 (kJ). Therefore, when compared to Comparative Example 3, Example 3 can be said to have superior thermal efficiency because it can have a higher heat storage amount and heat recovery amount with the same shell thickness.

[0062] Example 3, configured as described above, is primarily composed of alumina and has an average absorbance of greater than 0.3 at 1.7 to 2.7 μm, which is the central wavelength of radiant heat at 800 to 1400°C. Furthermore, Example 3 contains, in addition to alumina, at least one of Cr, Fe, Mn, Co, Ti, Ca, Zr, Hf, and Ta, and contains 1 wt% or more of a compound that is a carbide, oxide, or nitride, or a mixture thereof, calculated as a compound. Furthermore, Example 3 is a shell with a spheroidal outer surface that includes a sphere and a hollow interior. Therefore, Example 3 has high average absorbance, resulting in high thermal efficiency even in thermally non-equilibrium conditions such as regeneration systems.

[0063] In addition, in Examples 3-2 to 3-5, when the average outer diameter of the shell is D and the average diameter of the hollow portion is d, d is smaller than (D-8) mm. Therefore, Examples 3-2 to 3-5 can maintain a high level of heat storage amount and a high ratio of heat recovery amount to heat storage amount, and therefore have very high thermal efficiency.

[0064] [Example of Study] In addition, in an example of study using a simulation model simulating a hollow spherical ceramic heat storage body with an average absorbance of 0.9 and an outer diameter of 13 mm, it was found that the highest thermal efficiency was achieved when the shell thickness was 6.5 mm, i.e., when the body was solid spherical.

[0065] In the example constructed as described above, where D is the average outer diameter of the shell and d is the average diameter of the hollow portion, D is 13 mm or less and d is 1 mm or less (including 0 mm, i.e., a solid sphere). Therefore, the example has very high thermal efficiency even in a thermally non-equilibrium state such as a regeneration system.

[0066] [Example 4 and Comparative Example 4] Next, a maintenance test using the ceramic thermal storage body 10 manufactured by the above manufacturing method will be described below, and Example 4 and Comparative Example 4, which do not belong to the present invention, will be described. Note that the present invention is not limited to these examples.

[0067] Comparative Example 4 is a conventional ceramic heat storage medium made of alumina, manufactured by a known method, and has a white solid spherical shape. Example 4 is a ceramic heat storage medium 10 manufactured in the same manner as Examples 1 and 2-1.

[0068] In the maintenance performance evaluation test, a mixed gas containing fine iron oxide and carbon was blown into approximately 300 small-sized thermal storage tanks equipped with Comparative Example 4 or Example 4 at 100 L / min, and after a predetermined time had passed, the dirt adhering to the outer surface of Comparative Example 4 or Example 4 was observed. After that, the surface was cleaned to confirm the cleanability.

[0069] As a result, it was found that Example 4 had significantly less adhesion of dirt to its surface than Comparative Example 4. Furthermore, after the test, Comparative Example 4 had many irregularities and pores on its surface as a result of the abrasion, which trapped the dirt that had adhered thereto, making it difficult to clean. On the other hand, after the test, Example 4 maintained a smooth spherical shape with few irregularities and pores, making it easy to remove the dirt that had adhered. Therefore, it can be said that Example 4 is easy to maintain because it is difficult for contaminants to adhere to it, has excellent abrasion resistance, and is less likely to break.

[0070] The above describes the present invention based on illustrative examples, and the technical scope is not limited thereto. For example, the shell shape may be a closed spheroid with a hollow portion, such as a rugby ball. Furthermore, the shell thickness can be appropriately adjusted so that the heat storage performance, including the heat storage capacity, heat storage efficiency, and heat dissipation efficiency, is the desired value, as long as the relationship between the average outer diameter D of the shell and the average diameter d of the hollow portion is within a range where d is less than (D-8) mm (including 0 mm in some cases). Furthermore, the ceramic powder and dispersion medium are not limited to those listed in the above examples; any material can be selected as long as it is capable of achieving breakage resistance and high thermal efficiency. Furthermore, the additive is a compound containing at least one of Cr, Fe, Mn, Co, Ti, Ca, Zr, Hf, and Ta, and is added in an amount of 1 wt. % or more as an oxide, carbide, nitride, or a mixture thereof. The selection, mixture, and amount of the compound can be arbitrarily set to achieve the desired performance. The mold may be divided into left and right parts, or may be divided into three or more parts. The material of the mold is not limited as long as it can absorb the dispersion medium. The number, arrangement, extension direction, etc. of the injection holes of the mold are not limited to those described above. In the method for manufacturing a ceramic thermal storage medium, the drying step may not involve firing, or firing may be performed immediately after demolding. In addition, although slip casting is preferably used to manufacture a ceramic thermal storage medium, techniques such as extrusion molding, rolling molding, and press molding may also be used.

[0071] [Example 5 and Comparative Example 5] Furthermore, in the ceramic heat storage body 10 belonging to the present invention, a method for estimating a better composition, that is, a better amount of alumina as a main component, and the type and amount of compounds (additives) other than alumina (composition estimation method), and a method for manufacturing the ceramic heat storage body 10 using this method will be explained using the examples of Example 5 (Examples 5-1 to 5-3, 5-A to 5-K) and Comparative Example 5. Note that the present invention is not limited to these examples.

[0072] The composition estimation method can be executed by a computer 101 as shown in FIG. 12 . The computer 101 includes an input unit 102, an output unit 103, a storage unit 104, a communication unit 106, and a control unit 108. Note that some of these units may be omitted. The input unit 102 is a unit for inputting information, such as at least one of a pointing device, a microphone, and a keyboard. The output unit 103 is a unit for outputting information, such as at least one of a display, a speaker, and a printer. Note that a single device may serve as both the input unit 102 and the output unit 103, such as a touch panel. Alternatively, a single device may serve as multiple other units. The storage unit 104 is a unit for storing information, such as at least one of a memory, a hard disk drive (HDD), a solid-state drive (SSD), and an optical disk drive. A composition estimation program P is stored in the storage unit 104. The composition estimation program P includes multiple steps for estimating a better composition of the ceramic thermal storage body 10. The communication means 106 is a means for communicating information. The communication means 106 is capable of communicating, for example, with at least one of a local area network (LAN), the Internet, a telephone network, and a dedicated line. The communication means 106 is capable of communicating at least wirelessly and via a wired connection. The control means 108 is a means for controlling various means, and is, for example, a central processing unit (CPU). The control means 108 is capable of executing various programs. The programs may include a mathematical statistics program.

[0073] As shown in Fig. 13, in the composition estimation method that can be implemented by the control means 108 that executes the composition estimation program P, first, the control means 108 requests input of the correspondence between the quantitative ratios (examples of specific values ​​of the compositions) of the compositions of multiple samples and the actually measured emissivity at a predetermined wavelength (sample data input reception step S11). At least a part of the composition of each sample differs from the composition of the other samples. For example, the user may input multiple samples A, B, etc., in which alumina is in the order of x, y, z ... Ａ , xＢ ...wt%, Co ３ O ４ Gay Ａ , y Ｂ ...weight%, Fe ３ O ４ Ga z Ａ , z Ｂ ...weight%, Cr ２ O ３ Ga V Ａ , v Ｂ ...wt%, MnO ２ But w Ａ , w Ｂ ... weight %, the emissivity at a wavelength of 1.65 μm is Ａ , X Ｂ ... and the emissivity at a wavelength of 1.8 μm is Y Ａ , Y Ｂ ... and the emissivity at 2.1 μm is Z Ａ , Z Ｂ ... and the emissivity at 2.6 μm is V Ａ , V Ｂ ... and the emissivity at 3.1 μm is W Ａ , W Ｂ ... and measure each of them, and the ratio of the amounts (x Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) corresponding to the emissivity group (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) and the ratio (x Ｂ , y Ｂ , z Ｂ , v Ｂ , w Ｂ ) corresponding to the emissivity group (X Ｂ , Y Ｂ , Z Ｂ , V Ｂ , W Ｂ ) and ... are obtained. Then, the user inputs a plurality of combinations of specific quantity ratios and groups of actually measured emissivities to the computer 101 using the input means 102.

[0074] Next, the control means 108 obtains a function (objective function) relating to emissivity with the quantity ratio as a variable from the relationship between the quantity ratio and the emissivity for each sample by mathematical programming (objective function acquisition step S12). The objective function indicates a value corresponding to the emissivity, and strictly speaking, it may differ from the actual emissivity and may exceed 1. Therefore, hereinafter, it is regarded as the degree of contribution of the composition parameter (variable) to the emissivity, and is called a relative emissivity parameter. For example, the control means 108 obtains a specific value of the composition (x Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) and the specific value of emissivity (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) and (x Ｂ , y Ｂ , z Ｂ , v Ｂ , w Ｂ ) and (X Ｂ , Y Ｂ , Z Ｂ , V Ｂ , W Ｂ ) and the sum of the distances to the set of... The coefficients a of the following equations representing the objective function related to the relative radiation parameters (X, Y, Z, V, W) with the composition parameters (x, y, z, v, w) as variables are １ ~e ５ and each intercept a ６ ~e ６ (Least squares method) X = a １ x + a ２ y+a ３ z+a ４ v + a ５ w+a ６ ...Formula (1-1) Y=b １ x + b ２ y+b ３ z+b ４ v+b ５ w+b ６ ...Formula (1-2) Z=c １ x + c ２y+c ３ z+c ４ v+c ５ w+c ６ ...Formula (1-3) V=d １ x + d ２ y+d ３ z+d ４ v+d ５ w+d ６ ...Formula (1-4) W=e １ x + e ２ y+e ３ z+e ４ v+e ５ w+e ６ The method for obtaining the objective function from the set of specific values ​​for each sample may be any mathematical programming method, such as linear programming or dynamic programming. The mathematical programming method may be performed by a mathematical statistics program.

[0075] Next, the control means 108 calculates, from the obtained objective function, i.e., the relative radiation parameters (X, Y, Z, V, W), an estimated value (x １ , y １ , z １ , v １ , w １ ) is estimated (composition estimation step S13). This estimation can complete the composition estimation. Note that multiple sets of estimated values ​​may be estimated.

[0076] Then, the estimated value of a better composition of the ceramic heat storage body 10 found by such composition estimation (x １ , y １ , z １ , v １ , w １ ) The ceramic heat storage body 10 is manufactured according to the above.

[0077] A more detailed example of the composition estimation method and the method for manufacturing the ceramic regenerator 10 will be described below.

[0078] FIG. 14 is a table showing the specific values ​​(weight % of each component) of the compositions of samples (Examples 5-A to 5-K) of 11 different compositions in the sample data input acceptance step S11. The number of samples may be 10 or less, or 12 or more, but from the viewpoint of improving the accuracy of the mathematical programming, it is preferably 5 or more, and more preferably 10 or more. For example, the specific value (x %) of the composition (weight %) of Example 5-A is Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) = (93.88, 2.04, 2.04, 2.04, 0). Ａ = 0 is MnO in Example 5-A ２ The weight ratio (g) of each component in Example 5-A is 0.01g, and the weight ratio (g) of each component in Example 5-A is 0.01g. ２ O ３ ): Co ３ O ４ : Fe ３ O ４ : Cr ２ O ３ = 92:2:2:2. The specific values ​​of the composition (wt%) of Example 5-E (x Ｅ , y Ｅ , z Ｅ , v Ｅ , w Ｅ ) = (95.84, 0, 2.08, 0, 2.08). The weight ratio (g) of each component in Example 5-E was alumina:Fe ３ O ４ : MnO ２ = 92:2:2. Furthermore, the specific values ​​of the composition (wt%) of Example 5-K (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) = (92,2,2,2,2). The weight ratio (g) of each component in Example 5-K was alumina:Co ３ O ４ : Fe ３ O ４ : Cr ２ O ３ : MnO ２= 92:2:2:2:2. Examples 5-A to 5-K are all produced in the same manner as Example 1. For comparison, Comparative Example 5, which is similar to Comparative Example 1, is also produced. The specific values ​​of the composition of Comparative Example 5 are (100, 0, 0, 0, 0) since no additives are used.

[0079] FIG. 15 is a graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Examples 5-A to 5-D. FIG. 16 is a graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Examples 5-E to 5-H. FIG. 17 is a graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Examples 5-I to 5-J and Comparative Example 5. FIG. 18 is a graph showing the emissivity (unitless; vertical axis) measured for each wavelength (μm; horizontal axis) in Example 5-K and Examples 5-1 to 5-3. From these measurements, a group of emissivities (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) ~ (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ) is obtained (step S11). Here, the emissivity is measured as a distribution in the wavelength range of 1.65 to 3.3 μm. However, it may be measured only at the necessary wavelengths (1.65, 1.8, 2.1, 2.6, 3.1 μm) or at a partial wavelength range including the necessary wavelengths. Each of the necessary wavelengths is a wavelength of interest, and hereinafter, they are referred to as wavelengths of interest, and a combination of these wavelengths is referred to as a wavelength group of interest. In Figures 15 to 18, vertical dotted lines indicate each wavelength of interest. The wavelengths of interest are selected to represent the radiation characteristics of the ceramic thermal storage body 10, and preferably, multiple wavelengths are selected so as to have similar spacing between each other in the infrared range or a partial range thereof.

[0080] The resulting emissivity group (X Ａ , Y Ａ , ZＡ , V Ａ , W Ａ ) ~ (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ) is the specific value of the composition (x Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) ~ (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ), are input to the computer 101 by the input means 102 and stored in the storage means 104. The composition and emissivity group of Comparative Example 5 may also be input together. Then, the control means 108 calculates relative radiation parameters (X, Y, Z, V, W) as an objective function using the composition parameters (x, y, z, v, w) as variables by multiple regression analysis (step S12), and stores the relative radiation parameters (X, Y, Z, V, W) in the storage means 104. Here, the relative radiation parameters (X, Y, Z, V, W) are as follows: The formula for the relative radiation parameters (X, Y, Z, V, W) is also shown in FIG. 19. X=-0.012x+0.064y+0.012z+0.007v+0.127w+1.575...Equation (2-1) Y=-0.007x+0.053y+0.092z+0.003v+0.079w+0.976...Equation (2-2) Z=-0.003x+0.054y+0.098z+0.055v+0.017w+0.609...Formula (2-3) V=-0.004x+0.114y+0.038z+0.023v+0.045w+0.712...Formula (2-4) W=-0.032x+0.059y+0.069z-0.041v+0.054w+3.362...Formula (2-5)

[0081] The control means 108 estimates the composition parameters (x, y, z, v, w) that are expected to have larger relative radiation parameters (X, Y, Z, V, W) than any of the samples and thus improve the emissivity (step S13). Here, the estimated values ​​of the composition parameters (x, y, z, v, w) that are expected to improve the emissivity are estimated for Example 5-K (reference sample), which has the highest emissivity at each wavelength of interest among the samples. Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) = (92, 2, 2, 2, 2), and by substituting this into equations (2-1) to (2-5), the specific values ​​of the relative radiation parameters of Example 5-K are obtained as (X, Y, Z, V, W) = (0.891, 0.786, 0.781, 0.784, 0.700). The control means 108 calculates the coefficients a １ ~e ５ and each intercept a ６ ~e ６ and the specific values ​​of the composition of Example 5-K (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) according to the situation, estimates of composition parameters (x, y, z, v, w) having specific values ​​of relative radiation parameters (X, Y, Z, V, W) greater than the specific values ​​of the relative radiation parameters of Example 5-K (0.891, 0.786, 0.781, 0.784, 0.700) are calculated. Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ) may be calculated, which may be used to calculate estimates of the compositional parameters (x, y, z, v, w) having specific values ​​(X, Y, Z, V, W) of the relative radiative parameters greater than .

[0082] For example, the control means 108 obtains estimated values ​​of the composition parameters (x, y, z, v, w) by appropriately combining the following estimation items: １ ~e １Based on the fact that each is negative, the estimate of x is Ｋ However, since alumina is the main component and the ceramic has excellent properties such as ease of manufacture, ease of handling, and low cost, and also has sufficient strength, ease of maintenance, and wear resistance, x is preferably greater than 80, more preferably 85 or more, and even more preferably 90 or more. The control means 108 estimates the coefficient e of v in the formula (2-5) as ４ Based on the fact that is negative, we estimate v as v Ｋ The control means 108 estimates the coefficient a of y in the equations (2-1) to (2-5) to be smaller than the above (estimation item 2). ２ ~e ２ The distribution of the size of w is the coefficient a ５ ~e ５ Based on the tendency for the distribution of the magnitude of Ｋ The increase in the estimated value of y Ｋ The control means 108 estimates the coefficient a of z in the equations (2-1) to (2-5) so as to emphasize the increase in ３ ~e ３ The distribution of the size of w is the coefficient a ５ ~e ５ Based on the tendency for the distribution of the magnitude of Ｋ The increase in the estimated value of z is Ｋ (Estimation item 4). By substituting the assumed values ​​of various composition parameters (x, y, z, v, w) into equations (2-1) to (2-5), assumed values ​​of relative radiation parameters (X, Y, Z, V, W) for the assumed values ​​are obtained, and the assumed values ​​of the relative radiation parameters (X, Y, Z, V, W) are compared with the relative radiation parameters (X, Y, Z, V, W) in Example 5-K or the actually measured emissivity group (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ), the assumed values ​​of the composition parameters (x, y, z, v, w) may be treated as estimates of the composition parameters (x, y, z, v, w) that are expected to improve emissivity.

[0083] In this way, as shown in FIG. 19, the control means 108 calculates the estimated values ​​(x, y, z, v, w) of the composition parameters (x, y, z, v, w) that are expected to improve the emissivity of the following three types: １ , y １ , z １ , v １ , w １ ) ~ (x ３ , y ３ , z ３ , v ３ , w ３ ) are estimated as Examples 5-1 to 5-3 in order. The specific values ​​of the relative radiation parameters of Examples 5-1 to 5-3 are all greater than the specific values ​​of the relative radiation parameters of Example 5-K (0.891, 0.786, 0.781, 0.784, 0.700). The number of types of estimated values ​​of the composition parameters may be two or less, or may be four or more. Example 5-1: (x １ , y １ , z １ , v １ , w １ ) = (90, 2, 6, 0, 2) Example 5-2: (x ２ , y ２ , z ２ , v ２ , w ２ ) = (90, 6, 2, 0, 2) Example 5-3: (x ３ , y ３ , z ３ , v ３ , w ３ ) = (90, 4, 4, 0, 2)

[0084] The estimated values ​​of the relative radiation parameters in Examples 5-1 to 5-3 exceed the specific values ​​of the relative radiation parameters in Example 5-K. Therefore, there is a sufficiently high probability that the emissivity at each wavelength of interest in Examples 5-1 to 5-3 exceeds the emissivity at each wavelength of interest in Example 5-K. Therefore, the estimated values ​​of the composition parameters (x １ , y１ , z １ , v １ , w １ ) ~ (x ３ , y ３ , z ３ , v ３ , w ３ If a ceramic heat storage body 10 is manufactured using a composition that conforms to at least one of the above (manufacturing method using a composition estimation method), there is a sufficiently high probability that a ceramic heat storage body 10 with superior thermal emissivity than Example 5-K will be obtained.

[0085] In order to actually confirm the thermal emissivity of Examples 5-1 to 5-3, the estimated values ​​of the composition parameters (x １ , y １ , z １ , v １ , w １ ) ~ (x ３ , y ３ , z ３ , v ３ , w ３ ) were actually manufactured in the same manner as in Example 1, and the results of measuring the emissivity for each wavelength are shown in Figure 18, as described above. According to Figure 18, the emissivity distribution curves of Examples 5-1 to 5-3 are located above (on the higher side of the Y axis) the emissivity distribution curve of Example 5-K. Furthermore, the emissivities of Examples 5-1 to 5-3 are greater than that of Example 5-K at all wavelengths of interest. This confirms that the radiation performance of Examples 5-1 to 5-3 exceeds that of Example 5-K. Note that confirmation of the emissivity of a ceramic heat storage body 10 manufactured with a composition according to specific values ​​of the estimated composition parameters may be omitted. Furthermore, the conditions for estimating a better composition may be varied in various ways, such as by ensuring that the relative radiation parameters at specific values ​​of the composition parameters exceed the relative radiation parameters or emissivity of the reference sample at the majority of wavelengths of interest.

[0086] In this way, by inputting pairs of specific values ​​of composition parameters and specific values ​​of emissivity for multiple samples, calculating relative radiation parameters using the composition parameters as variables through multiple regression analysis, and obtaining estimated values ​​of composition parameters that improve the obtained relative radiation parameters, a better composition of the ceramic thermal storage body 10 can be found. It should be noted that even compositions other than those illustrated above can similarly be used to find a better composition of the ceramic thermal storage body 10. For example, at least one of the four additives may be omitted while at least one additive remains. Furthermore, compounds other than the four mentioned above may be substituted or added.

[0087] In Examples 5-1 to 5-3, the main component is alumina, the average absorbance is greater than 0.3 at 1.7 to 2.7 μm, which is the central wavelength of radiant heat at 800 to 1400° C., and the compound other than alumina is contained in an amount of 1 wt % or more in terms of compound, and the compound is Co ３ O ４ , Fe ３ O ４ and MnO ２ Contains Co ３ O ４ The content is 2% by weight or more and 6% by weight or less (2%, 6%, and 4% by weight in Examples 5-1 to 5-3, respectively), and Fe ３ O ４ The content is 2% by weight or more and 6% by weight or less (6, 2, 4% by weight, respectively), and MnO ２ Therefore, the ceramic heat storage body 10 has better radiation characteristics.

[0088] In addition, Example 5 is a method for manufacturing a ceramic heat storage body having steps S1 to S4 for manufacturing a ceramic heat storage body 10 containing alumina as a main component and further containing one or more compounds other than alumina. The manufacturing method involves manufacturing a plurality of samples (Examples 5-A to 5-K) that differ from each other in at least one of the amount of alumina and the type and amount of the compound, and measuring the emissivity of each sample, and determining the composition (x) related to at least one of the amount of alumina and the type and amount of the compound obtained for each sample. Ａ , yＡ , z Ａ , v Ａ , w Ａ ) ~ (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) and emissivity group (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) ~ (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ A sample data input receiving step S11 is a step of receiving an input of a correspondence relationship between the composition (x) of the input sample and the composition (x) of the input sample in the computer 101. Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) ~ (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) and emissivity group (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) ~ (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ), and the relative radiation parameters (X, Y, Z, V, W) as an objective function with the composition (x, y, z, v, w) as a variable are acquired by mathematical programming (multiple regression analysis) in the computer 101. The relative radiation parameters (X, Y, Z, V, W) are calculated based on the relative radiation parameters (X, Y, Z, V, W) of Example 5-K or the emissivity group (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ) and the estimated composition (x １ , y １ , z １ , v １ , w１ ) ~ (x ３ , y ３ , z ３ , v ３ , w ３ and a composition estimation step S13 in which the estimated composition (x １ , y １ , z １ , v １ , w １ ) ~ (x ３ , y ３ , z ３ , v ３ , w ３ ) and the steps from the injection step S1 onwards are carried out. Therefore, a manufacturing method is provided that can rationally manufacture a ceramic regenerator 10 having better radiation characteristics by estimating the composition.

[0089] In addition, Example 5 is a method for estimating the composition of a ceramic heat storage body 10, which estimates the amount of alumina and the composition related to the type and amount of the compound in a ceramic heat storage body 10 that contains alumina as a main component and one or more compounds other than alumina. The composition estimation method involves manufacturing a plurality of samples (Examples 5-A to 5-K) that are different from each other in at least one of the amount of alumina and the type and amount of the compound, and measuring the emissivity of each sample, and estimating the composition (x Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) ~ (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) and emissivity group (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) ~ (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W ＫA sample data input receiving step S11 is a step of receiving an input of a correspondence relationship between the composition (x) of the input sample and the composition (x) of the input sample in the computer 101. Ａ , y Ａ , z Ａ , v Ａ , w Ａ ) ~ (x Ｋ , y Ｋ , z Ｋ , v Ｋ , w Ｋ ) and emissivity group (X Ａ , Y Ａ , Z Ａ , V Ａ , W Ａ ) ~ (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ), and the relative radiation parameters (X, Y, Z, V, W) as an objective function with the composition (x, y, z, v, w) as a variable are acquired by mathematical programming (multiple regression analysis) in the computer 101. The relative radiation parameters (X, Y, Z, V, W) are calculated based on the relative radiation parameters (X, Y, Z, V, W) of Example 5-K or the emissivity group (X Ｋ , Y Ｋ , Z Ｋ , V Ｋ , W Ｋ ) and the estimated composition (x １ , y １ , z １ , v １ , w １ ) ~ (x ３ , y ３ , z ３ , v ３ , w ３ and a composition estimation step S13 in which the composition of the ceramic thermal storage body 10 having better radiation characteristics can be reasonably estimated, thereby providing a composition estimation method that can contribute to the production of a ceramic thermal storage body 10 having better radiation characteristics.

[0090] In addition to the above-described modifications, the fifth embodiment also includes modifications of the first to fourth embodiments as appropriate.

[0091] 10: ceramic heat storage body, 11: shell, 12: hollow portion, 20: plaster mold (molding mold).

Claims

1. A ceramic heat storage medium whose main component is alumina and whose average absorbance at the central wavelength of 1.7 to 2.7 μm, which is the wavelength of radiant heat at 800 to 1400°C, is greater than 0.

3.

2. A ceramic heat storage medium according to claim 1, characterized in that it contains 1% by weight or more of a compound other than alumina in terms of compound.

3. The ceramic heat storage medium according to claim 2, wherein the compound contains at least one of Cr, Fe, Mn, Co, Ti, Ca, Zr, Hf, and Ta.

4. The ceramic heat storage medium according to claim 2, wherein the compound is any one of a carbide, an oxide, a nitride, or a mixture thereof.

5. A ceramic heat storage medium according to any one of claims 1 to 4, characterized in that the outer surface is a spheroidal shape including a sphere, and the shell has a hollow portion inside.

6. A ceramic heat storage medium according to claim 5, characterized in that, when the average outer diameter of the shell is D and the average diameter of the hollow portion is d, d is smaller than (D-8) mm.

7. A ceramic heat storage medium according to any one of claims 1 to 4, characterized in that it is a solid body whose outer surface is in the shape of a spheroid including a sphere and whose average outer diameter is 13 mm or less.

8. The ceramic heat storage medium according to claim 5, wherein the temperature at the center of the hollow portion is higher than the temperature at the inner surface of the shell during heat storage.

9. The compound is Co ３ O ４ , Fe ３ O ４ and MnO ２ The Co ３ O ４ The iron content is 2% by weight or more and 6% by weight or less, ３ O ４ The content of MnO is 2% by weight or more and 6% by weight or less, ２ 4. The ceramic heat storage medium according to claim 3, wherein the ceramic heat storage medium contains 2% by weight of the above.

10. A method for manufacturing a ceramic heat storage body, comprising: an injection step of injecting a slurry containing ceramic powder and a dispersion medium into a molding die having the outer surface shape of a shell without an opening; a molding step of making the molding die absorb the dispersion medium to obtain a molded body having the shell and a hollow portion formed inside the shell; a demolding step of releasing the molded body from the molding die; and a drying step of drying and firing the released molded body to form a ceramic heat storage body.

11. The method for manufacturing a ceramic heat storage medium according to claim 10, wherein the dimensional variation of the shell relative to the average outer diameter is within ±1 mm.

12. A method for manufacturing a ceramic heat storage body according to claim 10 or 11, for manufacturing a ceramic heat storage body containing alumina as a main component and further containing one or more compounds other than alumina, comprising: a sample data input receiving step in which a computer receives input of the correspondence between the emissivity and the composition relating to at least one of the amount of alumina and the type and amount of the compound, which is obtained for each sample by manufacturing a plurality of samples that differ from each other in at least one of the amount of alumina and the type and amount of the compound, and measuring the emissivity of each; an objective function acquisition step in which the computer acquires, by mathematical programming, a relative radiation parameter as an objective function with the composition as a variable, from the plurality of correspondences between the composition and emissivity of the input sample; and a composition estimation step in which the computer estimates the value of the composition whose relative radiation parameter exceeds that of any of the samples, 13. A method for estimating the composition of a ceramic heat storage body, which contains alumina as a main component and further contains one or more compounds other than alumina, and which estimates a composition related to the amount of said alumina and the type and amount of said compound, comprising: a sample data input receiving step in which a computer receives input of the correspondence relationship between the composition and the emissivity obtained for each of the samples by manufacturing a plurality of samples having different compositions and measuring the emissivity of each; an objective function acquisition step in which the computer acquires a relative emissivity parameter as an objective function with the composition as a variable from the plurality of correspondence relationships between the composition and the emissivity of the input samples by mathematical programming; and a composition estimation step in which the computer estimates the value of the composition for which the relative emissivity parameter exceeds that of any of the samples.

14. The method for estimating the composition of a ceramic thermal storage medium according to claim 13, wherein the mathematical programming is a multiple regression analysis.