High-temperature heat storage element, high-temperature heat storage component and high-temperature heat storage devices each having at least one such high-temperature heat storage element, and industrial furnace having a high-temperature heat storage device

Abstract

The invention relates to a high-temperature heat storage element for storing and recovering heat, preferably for a high-temperature heat storage device, preferably a high-temperature heat storage device for storing and recovering heat from power generation or from furnace exhaust gases of industrial furnaces, preferably in the form of a single or separate or insulated composite moulded body, in particular in the form of an individual or separate or insulated composite brick. The invention further relates to a high-temperature heat storage component having at least one such high-temperature heat storage element and to a high-temperature heat storage device having at least one such high-temperature heat storage element, or having at least one such high-temperature heat storage component, and to an industrial furnace having such a high-temperature heat storage device.

Description

[0001] High-temperature heat storage element and high-temperature heat storage component as well as high-temperature heat storage each with at least one such high-temperature heat storage element and industrial furnace with a high-temperature heat storage

[0002] The present invention relates to a high-temperature heat storage element for storing and recovering heat, preferably for a high-temperature heat storage device, preferably a high-temperature heat storage device for storing and recovering heat from power generation or from furnace exhaust gases from industrial furnaces, preferably in the form of a single, separate, or insulated composite molded body, in particular in the form of a single, separate, or insulated composite brick. Furthermore, the invention relates to a high-temperature heat storage component having at least one such high-temperature heat storage element and a high-temperature heat storage device having at least one such high-temperature heat storage element or having at least one such high-temperature heat storage component, as well as to an industrial furnace having such a high-temperature heat storage device.

[0003] High-temperature storage systems, or high-temperature heat storage systems, are a subgroup of heat storage systems. They are typically referred to as HTS (High Temperature Storage) or HTES (High Temperature Energy Storage). Temperatures above 400°C are referred to as high-temperature heat storage systems.

[0004] Heat storage systems are generally divided into two types: latent heat storage and sensible heat storage. Latent heat storage systems contain phase-change materials (PCMs). Latent heat storage systems are also called latent heat storage systems or phase-change storage systems or PCMs. In latent heat storage systems, a large portion of the supplied thermal energy is stored in the form of transformation enthalpy (latent heat), for example, for a phase change from solid to liquid. The stored energy is hidden (latent) because, as long as the phase transition is not fully completed, the temperature of the material does not rise further despite the addition of heat.

[0005] Sensitive heat storage systems work on the principle of temperature changes in a storage material.

[0006] High-temperature heat storage systems have a wide range of uses, e.g. for storing thermal energy from industrial processes.

[0007] High-temperature heat storage systems are also used in sector coupling. Excess electricity, particularly solar or wind power, is converted into heat and stored in the high-temperature heat storage system. This virtually loss-free storage, at temperatures typically between 650 and 750 °C, allows for reconversion to electricity via a steam turbine when there is sufficient demand.

[0008] WO 2018 / 170533 A1 discloses a high-temperature heat storage and recovery system comprising a layer for generating heat from electrical energy, a layer for storing thermal energy, and a layer for recovering thermal energy. The layer for storing thermal energy comprises one or more upwardly open, conical containers containing a heat storage material, for example, a phase-change material. The upwardly open, conically widening shape and rounded corners allow the heat storage material to expand and reduce the stresses acting on the container.

[0009] To protect the material of the conical containers and prevent leakage of the

[0010] To prevent phase-change material from evaporating, it is known in the field to wrap the phase-change material with graphite paper. This is very complex.

[0011] WO 2023 / 077194 A1 discloses a high-temperature heat storage element in the form of a shaped body comprising a refractory material, a heat storage material, and an outer protective layer. The refractory material can be cement-bonded SiC, nitride-bonded SiC, silicon oxynitride-bonded SiC, clay-bonded SiC, SiAlO2-bonded SiC, or β-SiC-bonded SiC. The outer protective layer is a glassy protective layer made of an alkaline material. The heat storage material can be a phase-change material and is in granular form.

[0012] The high-temperature heat storage element is manufactured by mixing the individual components—in particular, the refractory material, the heat storage material, and a protective layer material—with liquid to form a slurry, pouring the slurry into a mold, allowing the slurry to harden to form the molded body, and heating the molded body. The protective layer is then formed by heating the refractory material and causing it to oxidize and react with the protective layer material.

[0013] The protective layer is intended to prevent the heat storage material from leaking out of the high-temperature heat storage element. For this reason, the high-temperature heat storage element does not need to be placed in a container. However, within the scope of the invention, it was discovered that the protective layer cannot always reliably prevent the heat storage material from leaking out.

[0014] The term "refractory" in the context of the invention should not be limited to the definition according to ISO 836 or DIN 51060, which define a cone softening point of > 1500° C. Refractory products within the meaning of the invention have a compression softening point To, 5 according to DIN EN ISO 1893: 2008-09 of To, 5 600 °C, preferably To, 5 800 °C. Accordingly, refractory or refractory granular materials or grains within the meaning of the invention are those materials or grains that are suitable for a refractory product with the above-mentioned pressure softening point To, 5.

[0015] Refractory products are used, among other things, to protect aggregate structures in aggregates where temperatures between 600 and 2000 °C, in particular between 800 and 1500 °C, prevail.

[0016] Coarse ceramic products are known to be products made from grains with grain sizes up to 6 mm, in special cases even up to 25 mm (see “Gerald Routschka / Hartmut Wuthnow, Practical Handbook “Refractory Materials”, 6th edition, Vulkan-Verlag (hereinafter referred to simply as “Practical Handbook”), Chapter 2).

[0017] Coarse ceramics are distinguished from fine ceramics by the grain size of their structural components. If the structural components are at least partially larger than 1 mm, the product is coarse ceramics; if the structural components are exclusively < 1 mm, the product is fine ceramics.

[0018] The term "granulation" or "granular material" within the meaning of the invention encompasses a pourable solid consisting of many small, solid grains. If the grains have a grain size of < 200 μm, the grain is a flour or powder. If the grains are produced by mechanical comminution, e.g., crushing and / or grinding, they are crushed granules or broken grains. However, a grain can also comprise granules or pellets produced by granulation or pelletizing without mechanical comminution. Furthermore, the broken grains can also have a coating of another refractory material.

[0019] The particle size distribution is generally determined by sieving. Unless otherwise stated, the particle sizes specified in this specification are also determined according to DIN 66165-2:2016-08.

[0020] Furthermore, unless otherwise stated, the aggregates / grains used in this invention are crushed, preferably uncoated, grains.

[0021] For the purposes of the invention, grain fractions or grain classes also have grain sizes between the two specified test grain sizes. The term "grain fraction" or "grain class" thus means that no grains remain on the upper sieve and none pass through the lower sieve. Thus, there is no oversize or undersize grain.

[0022] In contrast, the term “grain group” implies that some grains remain on the upper sieve (oversize grain) and some fall through the lower sieve (undersize grain).

[0023] Furthermore, the grain fractions or grain groups used in this field contain grains of different sizes. They therefore exhibit a grain distribution or grain size distribution. They are not single-grain fractions or groups.

[0024] Furthermore, a distinction is known between non-basic (Practical Handbook, 4.1) and basic refractory products (Practical Handbook, 4.2). According to DIN EN ISO 10081:2005-05, a distinction is made between non-basic and basic refractory products based primarily on their chemical reactivity. The non-basic product group includes materials of the SiO2-AhO3 series and other materials that cannot be further classified according to their chemical reactivity, such as SiC and carbon products. A key characteristic of most basic products is that the sum of the oxides MgO and CaO predominates. Chromite, picrochromite, spinel, and forsterite bricks are also considered basic products, even though they are virtually neutral.

[0025] In the case of heavy clay products, a distinction is also made between shaped and unshaped products.

[0026] Shaped coarse ceramic products are unfired, tempered, or ceramically fired products, preferably manufactured in a ceramic factory, particularly bricks or slabs. They have a defined geometry and are ready for installation. Shaping is achieved, for example, by pressing, stamping, ramming, or slip casting. The shaped products, especially the bricks, are then laid with mortar or mortar-free ("crunching"), for example, to form a lining. The production process for shaped coarse ceramic products is typically divided into the following steps (Practical Handbook, page 14 / Section 2.1):

[0027] - Processing

[0028] - Mix

[0029] - Shaping

[0030] - Drying

[0031] - (if necessary) thermal treatment up to 800 °C and / or firing

[0032] - Follow-up treatment (if necessary)

[0033] Unshaped products (Practical Handbook, page 142 / Section 5) are products that are brought into their final shape, usually by the user, from an unshaped fresh mass or from lumps, e.g., by pouring, vibrating, poking, tamping, or spraying. Unshaped products are usually placed behind formwork in larger fields at the place of use and, after hardening, form part of the lining. Examples of unshaped products include shotcrete, tamping, casting, vibrating, or grouting compounds. Refractory mortars (fire mortars) are also considered unshaped products. Silicon carbide materials or SiC refractory materials are described in the Practical Handbook, Chapter 4.1.5. The methods commonly used in ceramic processing are suitable for the production of refractory products from silicon carbide (SiC).However, due to the lack of sinterability of coarse silicon carbide grains, almost all SiC refractory materials are made with dissimilar bonds. A distinction is made between oxide or silicate bonds, nitrogen-containing bond systems, native SiC bonds, and special types (see especially the Practical Handbook, Table 4.10 A).

[0034] Silicon carbide materials with a silicate binder matrix are manufactured using clay as a binder, among other materials. During firing, the clay reacts to form a binder phase consisting of mullite and SiO2.

[0035] Silicon carbide materials with a nitrogen-containing binder system (=nitride-bonded SiC or nitride-bonded silicon carbide) comprise SiC grains or silicon carbide grains bonded together by a nitride-containing binder matrix. The binder matrix contains Si2N2 (silicon oxynitride), Si5N4 (silicon nitride), and / or SiAlO2 (silicon aluminum oxynitride) as binder phases.

[0036] According to DIN EN 1402-1:2004-01 and DIN EN ISO 1927-1:2012-11, refractory mortars are divided into heat-setting mortars, which set ceramically or chemically at elevated temperatures, and air-setting mortars, which set chemically or hydraulically at room temperature. Refractory mortars always contain at least one refractory grain, whereby the maximum grain size of the refractory grains contained in mortars is preferably < 1 mm (Practical Handbook, Chapter 5.9).

[0037] The object of the present invention is to provide a high-temperature heat storage element that is simple and cost-effective to manufacture and install, has a long service life, and ensures high heat storage capacity. A further object is to provide a high-temperature heat storage component and a high-temperature heat storage device, each comprising at least one such high-temperature heat storage element.

[0038] Another task is to provide an industrial furnace with such a high-temperature heat storage system.

[0039] In addition, a prefabricated high-temperature heat storage element component is to be provided for the production of the high-temperature heat storage element.

[0040] These objects are achieved by a high-temperature heat storage element having the features of claim 1, a prefabricated high-temperature heat storage element component having the features of claim 35, a high-temperature heat storage component having the features of claim 36, a high-temperature heat storage device having the features of claim 38, and an industrial furnace having the features of claim 39. Advantageous developments of the invention are characterized in the respective subsequent subclaims.

[0041] The invention is explained in more detail below using a drawing as an example. The drawings show:

[0042] Figure 1: Schematically a longitudinal section through an inventive

[0043] High-temperature heat storage element

[0044] Figure 2: Schematic longitudinal section through an inventive

[0045] High-temperature heat storage component with several high-temperature heat storage elements

[0046] Figure 3: Schematic of a longitudinal section through a high-temperature heat storage component according to the invention with several high-temperature heat storage elements according to a further embodiment. The high-temperature heat storage element 1 according to the invention (Figs. 1-3) serves to store and recover heat. It has an inner heat storage core 2 and a dimensionally stable outer shell 3 surrounding the heat storage core 2 on all sides. Between the heat storage core 2 and the outer shell 3 there is an expansion joint 4, which is filled with a fire-resistant expansion joint material 5.

[0047] The high-temperature heat storage element 1 is preferably a single, separate, or insulated composite molded body, preferably a single, separate, or insulated composite block. The high-temperature heat storage element 1 is preferably cuboid-shaped and preferably has a longitudinal direction 1a, a width direction 1b perpendicular thereto, and a height direction 1c perpendicular to the longitudinal direction 1a and the width direction 1b.

[0048] The preferably cuboid-shaped heat storage core 2 consists of at least one, preferably cuboid-shaped, core shaped body 16, preferably a stone.

[0049] The heat storage core 2 has a core outer surface 2a. The core outer surface 2a preferably has two opposing core side surfaces (not shown), two core end surfaces 6a perpendicular thereto, a core bottom surface 6b, and a core top surface 6c. The core bottom surface 6b and the core top surface 6c are opposite each other in the vertical direction 1c.

[0050] The at least one core molded body 16 has a molded body outer surface 16a. The molded body outer surface 16a preferably has two opposing molded body side surfaces (not shown), two molded body end surfaces 17a perpendicular thereto, a molded body bottom 17b, and a molded body top 17c. The molded body bottom 17b and the molded body top 17c are opposite each other in the vertical direction 1c.

[0051] If the heat storage core 2 consists of a single core mold 16, which is preferred, the mold outer surface 16a forms the core outer surface 2a. Accordingly, the mold side surfaces form the core side surfaces, the mold end surfaces 17a form the core end surfaces 6a, the mold bottom 17b forms the core bottom 6b, and the mold top 17c forms the core top 6c.

[0052] However, the heat storage core 2 can also consist of several core moldings 16 attached to one another (Fig. 2), particularly in the case of a larger high-temperature heat storage element 1. The core moldings 16 are attached directly to one another in such a way that they form the preferably cuboid-shaped heat storage core 2. The individual core moldings 16 are, in particular, not connected to one another. In this case, the core outer surface 2a is formed by parts of the molding outer surfaces 16a of the individual core moldings 16.

[0053] The heat storage core 2 primarily determines the heat storage capacity of the high-temperature heat storage element 1. The heat storage core 2 must therefore absorb and release heat efficiently. Furthermore, the heat storage core 2 should exhibit uniform thermal expansion.

[0054] The at least one core mold 16 therefore comprises at least one refractory grain made of a refractory material and at least one grain made of a phase-change material. Furthermore, the core mold 16 comprises a binder matrix made of at least one hardened binder, which bonds the grains together. The grains are thus homogeneously distributed in the core mold 16, in particular in the binder matrix.

[0055] The fact that the core molding 16 contains at least one refractory grain means that it can also contain a mixture of different refractory grains.

[0056] Within the scope of this application, this generally applies to the phrase "at least one." If at least one component can be included, this means, within the scope of this application, that a mixture of various of these components can also be included. The at least one refractory grain of the core molding 16 preferably consists of a material with a thermal conductivity at 20°C according to DIN EN 993-15:2005-07 of 20 to 500 W / mK, preferably of 100 to 400 W / mK.

[0057] In addition, the at least one refractory grain of the core molding 16 preferably has a softening point according to DIN EN 993-12:1997-06 of 1000 to 2500 °C, preferably of 1400 to 2300 °C.

[0058] Preferably, the core mold body 16 has a refractory grain made of non-oxide ceramic, preferably silicon carbide (SiC), and / or a refractory grain made of graphite, in particular flake graphite.

[0059] The SiC grain or refractory SiC grain can consist of a single or multiple silicon carbide raw materials (=silicon carbide raw material(s)). For example, the silicon carbide raw materials differ in their SiC content. This also applies analogously to the other refractory grains.

[0060] The advantage of the refractory SiC grain is that it exhibits high thermal conductivity and is thermochemically stable. In particular, it is inert toward the phase-change material.

[0061] The advantage of the refractory, particularly powder-like, graphite grain is that it also has high thermal conductivity and is thermochemically stable. Furthermore, it ensures a dense structure and a smooth molded body outer surface 16a. With a rough molded body outer surface 16a, coarse grains of the phase change material are visible and palpable on the molded body outer surface 16a. This promotes the leakage of the phase change material at high temperatures. With a smooth molded body outer surface 16a, the coarse grains are better embedded and their exposed surface is reduced. This significantly reduces the leakage of liquid phase change material at temperatures above the melting temperature of the phase change material. Furthermore, the at least one grain of refractory material, in particular the SiC grain, preferably has a grain size of <2.0 mm, preferably <1.5 mm, particularly preferably <1.0 mm.

[0062] And the graphite grain preferably has a grain size of < 200 pm, preferably < 150 pm.

[0063] Particularly advantageously, the core mold body 16 has a SiC grain and a graphite grain. However, it can also have exclusively a SiC grain or exclusively a graphite grain.

[0064] Preferably, the core molding 16 has a coarse grain portion with a grain size > 1.0 mm, a fine grain portion with a grain size of > 200 pm to < 1.0 mm and a fine grain portion with a grain size < 200 pm.

[0065] Preferably, the core molding 16 has a SiC content of 5 to 65 mass % (mass %), preferably 10 to 30 mass % and particularly preferably 15 to 20 mass % as determined in accordance with DIN EN ISO 21068-2:2008-12.

[0066] Preferably, the core molding 16 also has a carbon content of 2 to 65 mass%, preferably 10 to 25 mass%, particularly preferably 12 to 17 mass%, determined according to DIN EN ISO 21068-2:2008-12.

[0067] The at least one phase change material is preferably a metallic material, preferably a metal alloy.

[0068] The phase change material also preferably has a melting point of > 250 °C, preferably > 1000 °C, particularly preferably > 1050 °C, determined by means of dynamic differential calorimetry (DSC) according to DIN 51007:2019-04.

[0069] Preferably, the at least one phase-change material is a silicon-based, eutectic metallic material, particularly preferably an aluminum-silicon-nickel alloy. Furthermore, the at least one grain of phase-change material preferably has a grain size of 0.06 mm to 12 mm, preferably 1 mm to 6 mm. The grain of phase-change material preferably always also has a coarse grain portion.

[0070] Preferably, the core molding 16 has a proportion of phase change material of 30 to 97 mass%, preferably 50 to 70 mass%, determined according to DIN EN 13925-2:2003-07 by means of Rietveld and without an internal standard.

[0071] The binder matrix of the core molding 16 contains at least one set, permanent and / or temporary binder.

[0072] A permanent binder is a binder that hardens below the temperature required for ceramic firing, but does not evaporate under thermal stress, particularly in an O2 atmosphere, but rather transforms and forms a binding matrix with a ceramic or other bond. Permanent binders therefore ensure the cohesion of an unfired shaped body at room temperature and when used under thermal stress, particularly in an O2 atmosphere. In contrast, a temporary binder burns out and evaporates under thermal stress. Permanent binders harden at a temperature below the temperature required for ceramic firing, e.g. at room temperature, e.g. hydraulically or chemically (inorganic or organic-inorganic) or organically. Under thermal stress, they form a direct ceramic bond, e.g. through sintering.Phosphate bonds and cement bonds, for example, are transformed under thermal stress but remain intact. Synthetic resins are generally heat-curing at approximately 160-200 °C. Pyrolysis occurs at approximately 600 °C, and the synthetic resin bond is converted into a carbon bond.

[0073] Preferably, the at least one binder is a coking binder, preferably synthetic resin, tar, or pitch, particularly preferably synthetic resin. Coking binders form a coke framework after coking in a manner known per se. The coke framework ensures a certain strength of the heat storage core 2 even after the heat is applied to the heat storage core 2 and the resulting coking of the binder. Furthermore, carbon has a high thermal conductivity.

[0074] Another advantage of the coking binder, especially the synthetic resin, is that it ensures good pressing properties of the molding compound during the production of the heat storage core 2, since only a small amount of liquid is required. As a result, the pressed heat storage core 2 has low porosity and thus good thermal conductivity.

[0075] The coking binders, especially the synthetic resin, also ensure good green strength and rapid strength development.

[0076] However, it can also be an inorganic binder, preferably water glass or a sol-gel binder or a phosphate binder or alumina cement or Portland cement.

[0077] Furthermore, the core molding 16 preferably has a heat storage capacity of 200 to 2500 kJ / kg, preferably 800 to 1800 kJ / kg, determined by means of dynamic differential calorimetry (DSC) according to DIN 51007:2019-04.

[0078] In addition, the core molding 16 preferably has a cold compressive strength according to DIN EN 993-6:2019-3 of 5 to 250 MPa, preferably 20 to 50 MPa, determined on a test cylinder with a diameter of 36 mm and a height of 36 mm.

[0079] In addition, the core molding 16 preferably has a porosity according to DIN EN 993-1:2019-03 of 0.5 to 15 vol.%, preferably 5 to 8 vol.%, particularly preferably 6 to 7 vol.%.

[0080] Furthermore, the core molding 16 preferably has a dry bulk density according to DIN EN 993-1:2019-03 of 1.5 to 5 g / cm 3 , preferably 2.5 to 3.5 g / cm 3 , particularly preferably 3.1 to 3.3 g / cm 3,. Preferably, the core molding 16 also has a thermal conductivity at 200°C of 10 to 100 W / mK, preferably 15 to 30 W / mK, and / or at 600°C of 5 to 100 W / mK, preferably 15 to 30 W / mK, and / or at 1000°C of 5 to 100 W / mK, preferably 15 to 30 W / mK, determined according to DIN EN ISO 1893:2008-09.

[0081] Preferably, the core mold 16 is also an unfired and optionally tempered, preferably pressed, mold. This is advantageous because the phase-change material is not exposed to high temperatures before use of the high-temperature heat storage element 1, which could lead to deformation of the core mold 16. For this reason, the proportion of phase-change material in the core mold 16 can also be high. This also ensures that the phase-change material is only exposed to high temperatures once it is arranged within the outer shell 3 and thus protected from the atmosphere. This prevents oxidation of the phase-change material.

[0082] The core molding 16 is produced in a conventional manner from a refractory mix. The mix contains, in a conventional manner, a dry material mixture and, optionally, liquid mix components. The dry material mixture comprises at least one refractory grain and at least one grain of phase-change material. Furthermore, the mix comprises at least one binder in liquid or solid form, i.e., as part of the dry material mixture.

[0083] The amount of coarse grain in the dry matter mixture is preferably 40 to 90 mass% and / or the amount of fine grain is preferably 5 to 50 mass% and / or the amount of flour grain is preferably 5 to 40 mass%.

[0084] In addition, the dry material mixture preferably has a proportion of phase change material of 30 to 99 wt. %, preferably 50 to 70 wt. %. For the production of the pressed core molding 16, in particular the core brick, a fresh batch mass or plastic mass, in particular molding mass, is produced from the batch components and optionally water. The fresh batch mass or molding mass thus comprises at least one binder, at least one refractory grain, and at least one grain of phase change material. If required, water is also used to produce the molding mass. If the molding mass contains a liquid binder and / or other liquid components, the addition of water is not necessary but possible. However, only water can also be added.

[0085] For optimal mixing of the individual components, mix for 3 to 10 minutes.

[0086] The molding compound is poured into molds and pressed to form a green molded body. The molding pressures are within the usual range, e.g., 50 to 200 MPa, preferably 100 to 180 MPa.

[0087] Preferably, the core molding 16 is dried and / or tempered after pressing. Tempering generally eliminates the need for prior drying.

[0088] Drying is preferably carried out at a temperature between 80 and 130 °C, in particular between 100 and 120 °C. Drying is preferably carried out to a residual moisture content of between 0 and 2 wt.%, in particular between 0 and 1 wt.%, determined according to DIN 51078:2002-12.

[0089] The tempering is preferably carried out at a temperature between 150 and 300 °C, in particular between 200 and 250 °C and / or for a duration of 3 to 72 h, preferably 5 to 24 h.

[0090] The dried, pressed, unfired, and optionally tempered core body 16, in particular the core brick, is then used to produce the high-temperature heat storage element 1 according to the invention. Another advantage of the heat storage core 2 made from the at least one unfired and optionally only tempered core body 16 is that it can be produced easily and with little energy consumption. Production by pressing ensures high density and thus high thermal conductivity. Furthermore, large quantities can be produced in a short time.

[0091] However, it is also within the scope of the invention to ceramically fire the core molding 16. For firing, the preferably dried, pressed core molding 16 is ceramically fired in a ceramic kiln, e.g., a tunnel kiln, preferably between 1200 and 1800°C, in particular between 1400 and 1700°C. Reducing firing is preferred.

[0092] As already explained above, it is particularly advantageous if the core mold body 16 is not ceramically fired.

[0093] The core molding 16 can also be formed by other conventional means, preferably by casting, in particular slip casting, into a mold or by a strand or extrusion process of a plastic mixture, or by manual or mechanical tamping or ramming. During casting, in particular slip casting, the mixture produced from the batch components is correspondingly flowable.

[0094] However, forming by pressing is preferred for the reasons mentioned above.

[0095] The outer shell 3 of the high-temperature heat storage element 1 according to the invention serves to protect the heat storage core 2 from the surrounding atmosphere. It must exhibit high resistance to oxidic and reducing gases and high resistance to temperature changes. In addition, the outer shell 3 imparts the high-temperature heat storage element 1 its mechanical stability, particularly during use. To ensure efficient energy input and output from the high-temperature heat storage device or other location of use, the outer shell 3 must also exhibit high thermal conductivity. The outer shell 3 is preferably formed at least in two parts from at least two outer shell components 3a;b and preferably has a crucible 7 for receiving the heat storage core 2 and a lid 8 closing the crucible 7.

[0096] The crucible 7 is a vessel or container open on one side, particularly at the top. It has a crucible wall 9 with two crucible side walls (not shown), two crucible end walls 10a perpendicular thereto, and a crucible bottom wall 10b. Furthermore, the crucible wall 9 has an outer crucible wall surface 9a, an inner crucible wall surface 9b, and a crucible wall edge surface 9c.

[0097] The crucible side walls and / or the crucible end walls 10a and / or the crucible bottom wall 10b also preferably each have a wall thickness of 3 to 60 mm, preferably 8 to 15 mm.

[0098] The lid 8 is preferably plate-shaped and has a lid bottom 8a, a lid top 8b and four lid edge surfaces 8c adjoining one another in pairs.

[0099] Preferably, the lid 8 also has a central centering projection 11 on the lid underside 8a. The centering projection 11 transitions via a chamfer 12 into a circumferential lid support surface 13.

[0100] The lid 8 also preferably has a thickness (= maximum distance between the lid bottom 8a and the lid top 8b) of 3 to 60 mm, preferably 8 to 15 mm.

[0101] The lid 8 and the crucible 7 are each made of a refractory, preferably coarse-ceramic, material. Consequently, the lid 8 and the crucible 7 each have at least one refractory grain. Preferably, the lid 8 and the crucible 7 are made of the same material. Furthermore, each is a shaped body or a shaped refractory product.

[0102] In addition, the at least one refractory grain of the lid 8 and / or crucible 7 preferably has a softening point according to DIN EN 993-12:1997-06 of 1000 to 2500 °C, preferably of 1400 to 2300 °C.

[0103] Preferably, the material of the lid 8 and / or the crucible 7 has a SiC grain.

[0104] The lid and the crucible preferably comprise SiC in an amount of 50 to 98 wt.%, particularly preferably 75 to 90 wt.%, most preferably 80 to 85 wt.%, determined according to DIN EN ISO 21068-2:2008-12.

[0105] One of the advantages of SiC is that it forms a protective SiO2 layer in an oxidizing atmosphere.

[0106] The crucible 7 and the lid 8 also preferably do not contain any phase change material.

[0107] Preferably, the lid 8 and the crucible 7 are also made of ceramically fired material. The shaping takes place, as stated above for the heat storage core 2, preferably by pressing from a refractory filler. The shaped bodies are then dried and then ceramically fired. Of course, the shaping can also be carried out in other ways, as stated above, preferably by casting.

[0108] If the lid 8 and the crucible 7 are ceramically fired, this has the advantage that no drying shrinkage or firing shrinkage occurs during the initial heating of the high-temperature heat storage element 1 according to the invention during use, which would lead to an irreversible change in length. Furthermore, the firing process achieves good physical properties, in particular high strength and low porosity.

[0109] In particular, the lid 8 and the crucible 7 consist of a silicon carbide material, preferably a silicon carbide material with a ceramic, preferably silicate, bond or with a nitride bond. However, another binder, such as a cement, a phosphate binder, or a coking binder, can also be used to manufacture the lid 8 and the crucible 7.

[0110] Depending on the application and the atmosphere prevailing during this application, the lid 8 and the crucible 7 can also be made of another refractory material to protect the heat storage core 2, preferably of silicon nitride or a material of the SiO2-AhO3 series, in particular a mullite-containing material, or of MA spinel or a cordierite-containing material.

[0111] Materials of the AhO3-SiO2 series are materials whose additives consist primarily of additives made of Al2O3 (alumina), SiO2, and aluminosilicates. These can be, in particular, silica materials, corundum materials, or materials made of aluminosilicates. These are preferably chamotte materials (< 45 mass% Al2O3) or alumina-rich materials (> 45 mass% Al2O3).

[0112] Preferably, the lid 8 and the crucible 7 also have a bulk density according to DIN EN 993-1:2019-3 of 1.5 to 3.0 g / cm 3 , preferably 2.0 to 2.5 g / cm 3 , particularly preferably 2.1 to 2.2 g / cm 3 , on.

[0113] In addition, the lid 8 and the crucible 7 preferably have a porosity according to DIN EN 993-1:2019-3 of 5 to 40 vol.%, preferably 15 to 30 vol.%, particularly preferably 20 to 25 vol.%.

[0114] In addition, the lid 8 and the crucible 7 preferably have a cold compressive strength according to DIN EN 993-5:2019-3 of 30 to 150 MPa, preferably 50 to 100 MPa, determined on a test cylinder with a diameter of 36 mm and a height of 8 mm.

[0115] In addition, the lid 8 and the crucible 7 preferably have a thermal shock resistance (TSR) of > 30 cycles, preferably > 70 cycles, determined according to DIN 51068:2008-11 during water quenching. In addition, the lid 8 and / or the crucible 7 preferably have a thermal expansion at 1000 °C according to DIN EN ISO 1893-2008-9 of 0 to 2%, preferably 0 to 1%.

[0116] Preferably, the lid 8 and / or the crucible 7 also have a thermal conductivity at 800°C of 10 to 20 W / mK, preferably 15 to 17 W / mK, and / or at 1000°C of 8 to 18 W / mK, preferably 13 to 15 W / mK, and / or at 1200°C of 6 to 16 W / mK, preferably 11 to 13 W / mK, determined according to DIN EN ISO 1893:2008-09.

[0117] As already explained, the expansion joint 4 filled with expansion joint material 5 is present between the heat storage core 2 and the outer shell 3. The expansion joint 4 and the expansion joint material 5 surround the heat storage core 2 on all sides.

[0118] The expansion joint 4 and the expansion joint material 5 serve to compensate for the different thermal expansions of the heat storage core 2 and the outer shell 3 during use. This prevents stresses and / or cracks caused by differences in expansion between the heat storage core 2 and the outer shell 3. This is because the expansion joint material 5 shrinks and thus provides space for the expansion of the heat storage core 2. The expansion joint material 5 does not increase in volume during use. The thermal conductivity of the expansion joint material 5 should be as high as possible. It is important that the expansion joint material 5 completely fills the expansion joint 4 and that no air (insulation) is present.

[0119] On the one hand, the expansion joint 4 should be as thin or narrow as possible in order not to impair the thermal conductivity of the high-temperature heat storage element 1, and on the other hand, it must be sufficiently wide to ensure sufficient space for expansion compensation.

[0120] The expansion joint 4 preferably has a joint width of 0.1 to 5%, preferably 0.5 to 2.0%, of the dimension of the heat storage core 2 in the respective direction 1a;b;c. In the longitudinal direction 1a, the expansion joint 4 thus has a joint width corresponding to 0.1 to 5%, preferably 0.5 to 2.0%, of the extension of the heat storage core 2 in the longitudinal direction 1a. This applies analogously to the other two directions 1b;c.

[0121] The expansion joint material 5 also preferably serves to connect, in particular bond, the heat storage core 2 and the outer shell 3 to form a stable high-temperature heat storage element 1, in particular also during use.

[0122] The expansion joint material 5 must also be sufficiently soft or elastic to compensate for the different expansions of the heat storage core 2 and the outer shell 3.

[0123] Preferably, the expansion joint material 5 is a set or hardened refractory mortar.

[0124] In this case, the expansion joint material 5 has a binder matrix which comprises at least one chemically or hydraulically hardened binder.

[0125] In addition, the expansion joint material 5 has at least one refractory grain embedded in the binder matrix.

[0126] The at least one refractory grain preferably consists of silicon carbide (SiC) or corundum (Al2O3) or an aluminosilicate or quartz (SiO2) or carbon (C), preferably graphite.

[0127] The at least one refractory grain of the expansion joint material 5 also preferably consists of a material with a thermal conductivity at 20°C according to DIN EN 993-15:2005-07 of 5 to 500 W / mK, preferably of 30 to 400 W / mK.

[0128] In addition, the at least one refractory grain of the expansion joint material 5 preferably has a softening point according to DIN EN 993-12:1997-06 of 1000 to 2500 °C, preferably of 1400 to 2300 °C. Furthermore, the at least one grain of refractory material, in particular the SiC grain, preferably has a grain size of <1.5 mm, preferably <1.0 mm.

[0129] The expansion joint material 5 preferably has a SiC content of 40 to 95 mass%, preferably 70 to 90 mass%, particularly preferably 83 to 86 mass%.

[0130] According to a further embodiment, the expansion joint material is a loose fill of at least one refractory grain. The loose fill also provides expansion compensation.

[0131] To produce the high-temperature heat storage element 1 according to the invention, the fresh, not yet hardened expansion joint material 5 is first poured into the crucible 7. Subsequently, the heat storage core 2 in the form of at least one core molding 16 is inserted into the crucible 7 such that the core outer surface 2a is spaced from the crucible wall inner surface 9b. This forms the expansion joint 4 between the core outer surface 2a and the crucible wall inner surface 9b. The core upper surface 6c is positioned somewhat lower than the crucible wall edge surface 9c. The heat storage core 2 is thus submerged in the crucible 7.

[0132] The expansion joint 4 is then further filled with the expansion joint material 5, and the core top 6c is coated with the expansion joint material 5, and the surface is scraped off. The lid 8 is then placed on the crucible 7. The centering projection 11 of the lid 8 is inserted into the crucible 7 with a form-fitting fit, and the lid support surface 13 is placed on the crucible wall edge surface 9c. If necessary, some expansion joint material 5 is pressed between the lid support surface 13 and the crucible wall edge surface 9c.

[0133] The high-temperature heat storage element 1 is then allowed to dry, preferably at a temperature of 80 to 130°C, preferably 100 to 120°C, for 3 to 24 hours, preferably 5 to 15 hours, during which the expansion joint material 5 hardens. Crucible 7, lid 8, and heat storage core 2 are then firmly connected to one another via the hardened expansion joint material 5.

[0134] If the expansion joint material 5 is loose fill, curing is not necessary.

[0135] Preferably, the manufactured high-temperature heat storage element 1 also has a length of 60 to 1500 mm, preferably 200 to 500 mm, a width of 60 to 1000 mm, preferably 100 to 400 mm and a height of 60 to 1000 mm, preferably 75 to 250 mm.

[0136] The advantage of the high-temperature heat storage element 1 according to the invention is that it can be used at high application temperatures. Furthermore, due to the high proportion of phase-change material, it exhibits high thermal conductivity. The high-temperature heat storage element 1 according to the invention is also resistant to thermal shock and changing atmospheres. It can be produced on an industrial scale and, thanks to its modular design, can be used flexibly.

[0137] In particular, in use, several high-temperature heat storage elements 1 are preferably combined to form a high-temperature heat storage component 11 (Fig. 2; 3). The high-temperature heat storage elements 1 are then arranged side by side and one above the other and preferably form a high-temperature heat storage wall or high-temperature heat storage wall 12. In particular, the high-temperature heat storage elements 1 are arranged side by side and one above the other in the manner of bricks.

[0138] According to one embodiment of the invention (Fig. 3), the high-temperature heat storage elements 1 do not have a separate lid 8, but the outer shell 3 of the respective lower high-temperature heat storage element 1 is formed by the crucible 7 of the lower high-temperature heat storage element 1 and the respective crucible bottom wall 10b of the high-temperature heat storage element(s) 1 arranged above it. This has the advantage that the heat conduction from one heat storage core 2 to the other is improved, since there is less other material in between. Nevertheless, the heat storage cores 2 are all surrounded on all sides by an outer shell 3 and thus protected from the atmosphere. Consequently, other arrangements and designs of the outer shell 3 are also possible within the scope of the invention, as long as the heat storage cores 2 are all surrounded on all sides by an outer shell 3.

[0139] It is also within the scope of the invention, for example, that the outer shell 3 is formed from more than two outer shell components 3a;b. Furthermore, the outer shell 3 can also be formed, for example, as two half-shells that are joined together to form the closed outer shell 3. The outer shell 3 is thus formed from at least two outer shell components 3a;b.

[0140] Furthermore, as described, it is particularly advantageous if the high-temperature heat storage element 1 is designed as a high-temperature heat storage brick consisting of the crucible 7, the heat storage core 2, the expansion joint material 5, and the lid 8. This is because the high-temperature heat storage element 1 can then be prefabricated and transported as such to the respective site of use. However, it is of course also possible to assemble the individual components of the high-temperature heat storage element 1 only at the site of use or to transport a prefabricated high-temperature heat storage element component, in particular a brick, consisting of the crucible 7, the heat storage core 2, and the expansion joint material 5, in particular the refractory mortar, without the lid 8, to the site of use.

[0141] The high-temperature heat storage device according to the invention serves in a manner known per se for storing and recovering energy from various processes, e.g., from electricity generation, in particular from wind power or solar energy. In this case, the high-temperature heat storage device has electrical heating means for heating the high-temperature heat storage elements 1. Heat recovery then occurs through wind heating and, if necessary, electricity generation. The high-temperature heat storage elements 1 can also be heated by hot exhaust gas streams, in particular by furnace exhaust gases from industrial furnaces, in particular furnaces in the iron industry, the non-ferrous metal industry, or kilns in the non-metal industry, preferably cement kilns, lime shaft or rotary lime kilns, magnesite or dolomite kilns, or furnaces in waste incineration plants.

[0142] Example:

[0143] 1. Production of the core mold for the heat storage core

[0144] Table 1 : Batch composition (dry batch components or dry material mixture) for the production of the core molding

[0145] The dry mix components were mixed with 3.5 wt.% phenol-formaldehyde resin, based on the dry mix components, to form a molding compound. The molding compound was then compacted using uniaxial pressing at a pressure of 140 MPa and pressed into a green core body (brick) with the following dimensions: 230 x 114 x 76 mm 3 .

[0146] The pressed core mold was then annealed at 250 °C for 24 h. 2. Production of the crucible and lid

[0147] Table 2: Batch composition (dry batch components or dry material mixture) for the production of the crucible and the lid

[0148] The theoretical chemical composition of the batch including binder is 85 wt% SiC, 8.2 wt% AI2O3, 6.5 wt% SiO2, 0.3 wt% Fe2O3.

[0149] The dry backfill components were mixed with a liquid binder in the form of sulfite waste liquor to form a fresh backfill mix or press mix. The liquid binder content was 1.0 mass% based on the dry mix. The liquid binder served, among other things, to increase the green strength.

[0150] The molding compound was compacted into a green molded body by uniaxial dry pressing. The molding pressure was 120 MPa.

[0151] The green molded bodies were then dried at 110 °C for 12 h to a residual moisture content of < 0.5% and the dried molded bodies were fired at 1430 °C for 8 h in an electrically heated muffle furnace.

[0152] 3. Production of the high-temperature heat storage element

[0153] The refractory mortar REFRABOND S-85 R from Refratechnik Steel GmbH was used as expansion joint mortar with the following properties: Table 3: Properties of the expansion joint mortar used

[0154] The fresh mortar mix was poured into the crucible, and then the core mold was inserted into the crucible in such a way that the outer surface of the mold was spaced from the inner surface of the crucible wall and the core mold was sunk into the crucible. This created an expansion joint between the outer surface of the mold and the inner surface of the crucible wall.

[0155] The expansion joint was then further filled with expansion joint mortar, and the top surface of the molded body was coated with expansion joint mortar and the surface was skimmed. The lid was then placed on the crucible. The centering projection of the lid was inserted into the crucible with a form-fit fit, and the lid support surface was placed on the edge surface 9c of the crucible wall. The manufactured high-temperature heat storage element was then dried at 110°C for 12 hours.

[0156] The external dimensions of the manufactured high-temperature heat storage element were: 254 x 137 x 99 mm.

[0157] Finally, it is pointed out that all mentioned, particularly claimed, features of the high-temperature heat storage element and the high-temperature heat storage device are particularly advantageous in themselves and in any combination and are the subject of the present invention.

[0158] In addition, the upper and lower limits specified for each individual range can all be combined with one another according to the invention.

Claims

1. A high-temperature heat storage element (1) for storing and recovering heat, preferably for a high-temperature heat storage, more preferably for a high-temperature heat storage for storing and recovering heat from power generation or from furnace exhaust gases of industrial furnaces, comprising an inner heat storage core (2) and a refractory outer shell (3) surrounding the heat storage core (2) on all sides, wherein an expansion joint (4) filled with a refractory expansion joint material (5) is provided between the heat storage core (2) and the outer shell (3), wherein the heat storage core (2) consists of at least one molded core body (16), wherein the molded core body (16) comprises at least one refractory granular material, at least one granular material made of a phase-change material, and a binder matrix comprising at least one hardened binder, which connects the granular materials to each other.

2. High-temperature heat storage element (1) according to claim 1, characterized in thatthe at least one molded core body (16) is unfired and preferably tempered.

3. High-temperature heat storage element (1) according to claim 1 or 2, characterized in thatthe outer shell (3) consists of ceramically fired refractory material.

4. High-temperature heat storage element (1) according to one of the preceding claims,characterized in thatthe high-temperature heat storage element (1) is designed as a composite brick and is preferably cuboid in shape.

5. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe binder matrix of the at least one molded core body (16) comprises at least one hardened, coking binder, preferably hardened synthetic resin and / or tar and / or pitch.

6. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a phase-change material content of 30 to 97 ma.-%, preferably 50 to 70 ma.-%, determined in accordance with DIN EN 13925-2:2003-07 using the Rietveld method and without an internal standard.

7. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one refractory granular material of the at least one molded core body (16) consists of a material having a thermal conductivity at 20 °C, according to DIN EN 993-15:2005-07, of 20 to 500 W / mK, preferably 100 to 400 W / mK.

8. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one refractory granular material of the at least one molded core body (16) comprises a softening point, in accordance with DIN EN 993-12:1997-06, of 1000 to 2500 °C, preferably 1400 to 2300 °C.

9. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a refractory granular material made of non-oxide ceramics, preferably SiC, and / or a refractory granular material made of graphite.

10. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises an SiC content of 5 to 65 ma.-%, preferably 10 to 30 ma.-%, and more preferably 15 to 20 ma.-%, determined in accordance with DIN EN ISO 21068-2:2008-12.

11. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a carbon content of 2 to 65 ma.-%, preferably 10 to 25 ma.-%, most preferably 12 to 17 mass-%, determined in accordance with DIN EN ISO 21068-2:2008-12.

12. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a heat storage capacity of 200 to 2500 kJ / kg, preferably 800 to 1800 kJ / kg, determined by differential scanning calorimetry (DSC) in accordance with DIN 51007:201904.

13. High-temperature heat storage element (1) according to one of the preceding claims,characterized in thatthe at least one molded core body (16) comprises a cold compressive strength according to DIN EN 993-6:2019-3 of 5 to 250 MPa, preferably 20 to 50 MPa, determined on a test cylinder with a diameter of 36 mm and a height of 36 mm.

14. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a porosity according to DIN EN 993-1:2019-3 of 0.5 to 15 vol.%, preferably 5 to 8 vol.%, and more preferably 6 to 7 vol.%.

15. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a dry raw density according to DIN EN 993-1:2019-03 of 1.5 to 5 g / cm3, preferably 2.5 to 3.5 g / cm3, and more preferably 3.1 to 3.3 g / cm3.

16. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) comprises a thermal conductivity of 10 to 100 W / mK, preferably 15 to 30 W / mK, at 200°C and / or of 5 to 100 W / mK, preferably 15 to 30 W / mK, at 600°C and / or of 5 to 100 W / mK, preferably 15 to 30 W / mK, at 1000°C, as determined in accordance with DIN EN ISO 1893:2008-09.

17. High-temperature heat storage element (1) according to one of the preceding claims,characterized in thatthe at least one granular material of phase-change material consists of a metallic material, preferably a metal alloy, and more preferably an alumi-num-silicon-nickel alloy.

18. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe phase-change material comprises a melting point of > 250 °C, preferably > 1000 °C, and more preferably > 1050 °C, as determined by differential scanning calorimetry (DSC) in accordance with DIN 51007:201904.

19. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe at least one molded core body (16) is a pressed molded body.

20. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe outer shell (3) is formed in at least two parts from at least two outer shell components (3a;b).

21. High-temperature heat storage element (1) according to claim 20, characterized in thatthe outer shell (3) comprises a refractory, preferably fired, crucible (7) and, preferably, a refractory, preferably fired, lid (8) that closes off the crucible (7), wherein the crucible (7) and the lid (8) are preferably firmly connected to one another and the heat storage core (2) is arranged within the crucible (7).

22. High-temperature heat storage element (1) according to claim 21, characterized in thatthe crucible (7) comprises a crucible wall (9) with two crucible side walls, two crucible end walls (10a) perpendicular thereto, and a crucible bottom wall (10b).

23. High-temperature heat storage element (1) according to claim 21 or 22, characterized in thatthe lid (8) is plate-shaped and preferably comprises a lid bottom surface (8a), a lid top surface (8b), and four lid edge surfaces (8c) that are adjacent to one another in pairs.

24. High-temperature heat storage element (1) according to one of claims 20 through 23, characterized in thatthe outer shell components (3a;b;7;8) consist of a silicon carbide material, preferably a silicon carbide material with a ceramic, preferably silicate, bond or a nitride bond, or of silicon nitride or a material of the SiO2-Al2O3 series, in particular a mullite-containing material, or of MA spinel or a cordierite-containing material.

25. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe outer shell (3) does not contain a phase-change material.

26. High-temperature heat storage element (1) according to one of claims 20 through 25, characterized in thatthe outer shell components (3a;b;7;8) comprise an SiC content of 50 to 98 ma.-%, more preferably 75 to 90 ma.-%, and most preferably 80 to 85 ma.-%, determined in accordance with DIN EN ISO 21068-2:2008-12.

27. High-temperature heat storage element (1) according to one of claims 20 through 26, characterized in thatthe outer shell components (3a;b;7;8) comprise a raw density according to DIN EN 993-1:2019-3 of 1.5 to 3.0 g / cm3, preferably 2.0 to 2.5 g / cm3, and more preferably 2.1 to 2.2 g / cm3.

28. High-temperature heat storage element (1) according to one of claims 20 through 27, characterized in thatthe outer shell components (3a;b;7;8) comprise a porosity according to DIN EN 993-1:2019-3 of 5 to 40 vol.-%, preferably 15 to 30 vol.-%, more preferably 20 to 25 vol.-%.

29. High-temperature heat storage element (1) according to one of claims 20 through 28, characterized in thatthe outer shell components (3a;b;7;8) comprise a cold compressive strength according to DIN EN 993-5:2019-3 of 30 to 150 MPa, preferably 50 to 100 MPa, determined on a test cylinder with a diameter of 36 mm and a height of 8 mm.

30. High-temperature heat storage element (1) according to one of claims 20 through 29, characterized in thatthe outer shell components (3a;b;7;8) comprise a thermal expansion at 1000 °C, in accordance with DIN EN ISO 1893-2008-9, of 0 to 2 %, preferably 0 to 1 %.

31. High-temperature heat storage element (1) according to one of claims 20 through 30, characterized in thatthe outer shell components (3a;b;7;8) comprise a thermal shock resistance of > 30 cycles, preferably > 70 cycles, determined in accordance with DIN 51068:2008-11 using water quenching.

32. High-temperature heat storage element (1) according to one of claims 20 through 31,characterized in thatthe outer shell components (3a;b;7;8) comprise a thermal conductivity of 10 to 20 W / mK, preferably 15 to 17 W / mK, at 800°C and / or of 8 to 18 W / mK, preferably 13 to 15 W / mK, at 1000°C and / or of 6 to 16 W / mK, preferably 11 to 13 W / mK, at 1200°C determined in accordance with DIN EN ISO 1893:2008-09.

33. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe high-temperature heat storage element (1) is cuboid in shape and comprises a longitudinal direction (1a), a width direction (1b) perpendicular thereto, and a height direction (1c) perpendicular to both the longitudinal direction (1a) and the width direction (1b), wherein the expansion joint (4) comprises a joint width of 0.1 to 5 %, preferably 0.5 to 2.0 %, of the dimension of the heat storage core 2 in the respective direction (1a;b;c).

34. High-temperature heat storage element (1) according to one of the preceding claims, characterized in thatthe expansion joint material (5) comprises at least one granular material made of refractory material, wherein the expansion joint material (5) preferably is a set, hardened refractory mortar or a loose fill.

35. A prefabricated high-temperature heat storage element component for forming a high-temperature heat storage element (1) according to one of claims 21 through 34, characterized in thatthe high-temperature heat storage element component comprises the heat storage core (2) and the crucible (7), and, between the heat storage core (2) and the crucible (7), the expansion joint material (5), wherein the heat storage core (2) and the crucible (7) are firmly connected to one another via the expansion joint material (5), and the crucible (7) is open at the top and uncovered.

36. High-temperature heat storage component (11), preferably high-temperature heat storage wall (12), for storing and recovering heat, preferably for a high-temperature heat storage, particularly for a high-temperature heat storage for storing and recovering heat from power generation or from furnace exhaust gases of industrial furnaces, comprising a plurality of high-temperature heat storage elements (1) arranged side-by-side and / or one above the other, characterized in thatthe high-temperature heat storage elements (1) are configured according to one of claims 1 through 34.

37. High-temperature heat storage component according to claim 36, characterized in thatat least partially, for high-temperature heat storage elements (1) arranged one above the other, the outer shell (3) of the lower high-temperature heat storage element (1) is formed by the crucible (7) of the lower high-temperature heat storage element (1) and the crucible bottom wall (10b) of the crucible (7) of the high-temperature heat storage element (1) arranged above it.

38. High-temperature heat storage for storing and recovering heat, characterized in thatthe high-temperature heat storage comprises at least one high-temperature heat storage element (1) according to one of claims 1 to 34 or a high-temperature heat storage component (11) according to 36 or 37.

39. Industrial furnace, preferably furnace used in the iron industry, the nonferrous metal industry, firing furnace of the non-metallic industry, or furnace of a waste incineration plant, characterized in thatthe industrial furnace comprises a high-temperature heat storage according to claim 38 for storing and recovering heat from the furnace exhaust gases of the industrial furnace.

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