A thermal storage module containing inorganic fillers and methods of use and purposes thereof

Abstract

The application provides a heat storage module containing inorganic fillers and a use method and purpose thereof, the heat storage module comprises a module body, the inside of the module body has a heat storage channel, the inside of the heat storage channel is filled with molten salt and inorganic fillers, and the sum of the volume of the molten salt after melting and the volume of the inorganic fillers is 50%-95% of the volume of the heat storage channel. The application effectively reduces the pressure fluctuation in the closed channel loaded with molten salt by filling the inorganic fillers, and the small amount of moisture entering the inside of the channel due to the "breathing" effect is also effectively absorbed, thereby greatly improving the stability of the molten salt and the heat storage module. Meanwhile, the inorganic fillers can also avoid the problems of phase separation and supercooling of the molten salt, significantly increase the heat cycle number of the module, greatly reduce the heat conduction resistance of the molten salt, and finally greatly increase the heat storage and heat release speed of the module, which is very suitable for preparing a functional module with fast heat storage and heat release.

Description

Technical Field

[0001] This invention belongs to the field of thermal storage material technology, and relates to a thermal storage module containing inorganic fillers, its usage method and application. Background Technology

[0002] As global climate change caused by carbon dioxide emissions becomes increasingly recognized by the public, there is an urgent market demand for carbon dioxide emission reduction and energy-efficient integrated utilization technologies. Among these, achieving efficient coupling between energy users and industrial waste heat (heat source) through thermal energy storage is one of the effective ways to significantly reduce energy consumption. Studies have found that when the energy user's demand is for heat energy, the cost of the thermal energy storage-heat supply process is only 10% to 30% of the cost of the electricity storage-electricity heating-heat supply process, making it extremely economical.

[0003] Molten salt is the most commonly used medium in thermal storage processes. It has a series of advantages, such as low vapor pressure, high calorific value, and low risk of explosion and ignition. However, molten salt also has a series of disadvantages, such as easy supercooling, easy phase separation, and strong corrosiveness. At the same time, in order to ensure that the thermal storage material has a huge heat exchange capacity, molten salt must be used for heat storage and heat supply around its phase change temperature. The sudden increase in viscosity caused by its phase change is detrimental to the heat transfer process. Especially when the volume of molten salt is large, it is difficult to heat it quickly or extract heat from it quickly.

[0004] Honeycomb ceramics are a porous support commonly used in catalytic processes. Their large specific surface area, abundant pores, and adjustable pore size and structure make them ideal as encapsulation materials for loading molten salts. Molten salt loaded inside the honeycomb ceramic can be heated or cooled by a heat transfer medium or cold transfer medium in the adjacent pores, thus achieving heat storage and release. Since heat transfer only needs to cross the pore walls of the honeycomb ceramic, its thermal resistance is low and completely controllable. Therefore, encapsulating molten salt in honeycomb ceramics is a promising method for preparing thermal storage materials. CN202581867U discloses a technical solution combining thermal storage molten salt and honeycomb ceramics, while CN114656937A discloses a method for preparing honeycomb ceramics using ilmenite slag, glass powder, and molten salt as raw materials, and then encapsulating molten salt to obtain a phase change thermal storage material.

[0005] However, to prevent the molten salt sealed inside the channels from bursting the honeycomb ceramic due to thermal expansion during heat storage, the filling degree of the molten salt is often not 100%, but rather has a certain amount of empty space, or in other words, a portion of gas must be sealed inside the channels. This portion of gas will also expand during high-temperature heat storage and contract during heat release, resulting in pressure fluctuations inside the channels. This causes a slight "breathing" effect between the sealed channels and the external gas, allowing external moisture to gradually enter the channels, which has a detrimental effect on the lifespan of the molten salt and its heat storage and release performance. Therefore, a new technical solution is needed to reduce pressure fluctuations inside the channels and reduce the impact of moisture entering the channels due to the "breathing" effect on the lifespan of the molten salt. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a thermal storage module containing inorganic filler, and its usage method and application. The thermal storage module includes a module body, the interior of which has thermal storage channels. The interior of the thermal storage channels is filled with molten salt and inorganic filler. The sum of the volume of the molten salt after melting and the volume of the inorganic filler is 50% to 95% of the volume of the thermal storage channels. By filling with inorganic filler, this invention effectively reduces pressure fluctuations within the closed channels loaded with molten salt, and effectively absorbs any small amount of moisture that enters the channels due to the "breathing" effect, thereby greatly improving the stability of the molten salt and the thermal storage module. At the same time, the inorganic filler can also avoid the problems of molten salt phase separation and undercooling, significantly increasing the number of thermal cycles of the module and greatly reducing the thermal conductivity resistance of the molten salt. Ultimately, this greatly increases the thermal storage and release rate of the module, making it very suitable for preparing functional modules for rapid thermal storage and release.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a thermal storage module containing inorganic filler. The thermal storage module includes a module body, the interior of which has thermal storage channels. The interior of the thermal storage channels is filled with molten salt and inorganic filler. The sum of the volume of the molten salt after melting and the volume of the inorganic filler is 50% to 95% of the volume of the thermal storage channels.

[0009] This invention effectively reduces pressure fluctuations within the closed channels of the molten salt by filling them with inorganic fillers. Small amounts of moisture that enter the channels due to the "breathing" effect are also effectively absorbed, thus significantly improving the stability of the molten salt and the heat storage module. Simultaneously, the inorganic fillers prevent phase separation and undercooling issues in the molten salt, significantly increasing the module's thermal cycle count and greatly reducing the thermal conductivity resistance of the molten salt. Ultimately, this greatly increases the heat storage and release rate of the module, making it highly suitable for fabricating functional modules with rapid heat storage and release capabilities.

[0010] The sum of the volume of the molten salt after melting and the volume of the inorganic filler in this invention is 50% to 95% of the volume of the heat storage channel, for example, 50%, 53%, 56%, 59%, 62%, 65%, 68%, 71%, 74%, 77%, 80%, 83%, 86%, 89%, 92%, or 95%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0012] As a preferred technical solution of the present invention, the amount of inorganic filler added is 1% to 30% of the total mass of the molten salt and inorganic filler, such as 1%, 3%, 6%, 9%, 12%, 15%, 18%, 21%, 24%, 27% or 30%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0013] Preferably, the inorganic filler comprises sepiolite fiber and / or boron nitride fiber.

[0014] The introduction of boron nitride fibers and / or sepiolite fibers creates numerous heterogeneous contact sites between the molten salt and these inorganic fillers. This successfully induces the formation of crystal nuclei during the rapid cooling of the molten salt, resulting in uniform cooling and crystallization, thus solving the problem of molten salt being prone to overcooling. The addition of boron nitride fibers significantly increases the thermal conductivity inside the molten salt, making the heat storage and release rate of the thermal storage module faster. The fibrous sepiolite has a significant thickening effect, and coupled with the blocking effect of boron nitride fibers, it is difficult for crystals generated due to phase separation inside the molten salt to settle and accumulate, effectively preventing phase separation in the molten salt.

[0015] Preferably, the sepiolite fibers are pre-treated with heat at 300-600°C, such as 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, or 600°C, but are not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] Preferably, the diameter of the boron nitride fiber is 3–10 μm, such as 3 μm, 3 μm, 3 μm, 3 μm, 3 μm, 3 μm, 3 μm, 3 μm, or 3 μm, etc., with an apparent density of 1.3–2 g / mL, such as 1.3 g / mL, 1.4 g / mL, 1.5 g / mL, 1.6 g / mL, 1.7 g / mL, 1.8 g / mL, 1.9 g / mL, or 2 g / mL, etc., with a true density of 2.29 g / mL, and an initial oxidation temperature of 830–880℃, such as 830℃, 835℃, 840℃, 845℃, 850℃, 855℃, 860℃, 865℃, 870℃, 875℃, or 880℃, etc., but not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0017] The apparent density refers to the bulk density of the fiber material in a loose state after it is stacked, while the true density refers to the density of the material itself in an absolutely dense state.

[0018] As a preferred embodiment of the present invention, the module body includes honeycomb ceramic.

[0019] This invention does not limit the shape and size of the outer contour of the honeycomb ceramic. Those skilled in the art can process it according to actual needs. For example, the outer contour can be various shapes such as square, circle, hexagon, and triangle.

[0020] As a preferred technical solution of the present invention, the material of the honeycomb ceramic includes any one or a combination of at least two of mullite, cordierite, silicon carbide or alumina. Typical but non-limiting examples of the combination include the combination of mullite and cordierite, the combination of mullite and silicon carbide, the combination of mullite and alumina, the combination of cordierite and silicon carbide, the combination of cordierite and alumina, or the combination of silicon carbide and alumina.

[0021] As a preferred technical solution of the present invention, the cross-sectional shape of the channel includes any one or at least two combinations of square, hexagon, circle or triangle. Typical but non-limiting examples of the combination include the combination of square and hexagon, square and circle, square and triangle, hexagon and circle, hexagon and triangle or circle and triangle.

[0022] Preferably, the diameter of the circumcircle of the cross-sectional shape of the channel is 5 to 80 mm, such as 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm or 80 mm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] As a preferred technical solution of the present invention, the module body also has heat transfer channels, which penetrate the module body and form openings on the surface of the module body for the flow of refrigerant or heat transfer medium.

[0024] Preferably, any two adjacent heat storage channels are separated by heat transfer channels.

[0025] As a preferred embodiment of the present invention, the heat storage channel penetrates the module body and forms an opening on the surface of the module body, and a sealing ceramic is provided at at least one end of the opening of the heat storage channel.

[0026] Preferably, the sealing ceramic is made of the same material as the honeycomb ceramic.

[0027] Preferably, sealing ceramics are provided at both ends of the heat storage channel openings to completely seal the molten salt and the inorganic filler inside the module body.

[0028] It should be noted that the sealing ceramic is used to prevent molten salt from leaking or overflowing from the channel. Therefore, for example, if the channel of the heat storage module is placed perpendicular to the placement surface, the end of the channel that contacts the placement surface (facing downwards) needs to be fitted with the sealing ceramic, while the other end facing upwards can be left open without the sealing ceramic. This reduces manufacturing difficulty and costs. Also, since the open placement does not require consideration of pressure fluctuations, as long as the molten salt does not overflow from the top of the open during circulation, the channel damage caused by pressure fluctuations is reduced directly from the source, without the need for inorganic fillers to balance pressure fluctuations.

[0029] At this point, during the heat storage and release process, hot fluid (heat transfer medium) or cold fluid (coolant) is vertically blown into the heat transfer channels of the module body, and the lower part of the module is supported by wire mesh, which still allows for successful heat storage and release. Furthermore, due to the presence of inorganic filler, it can also absorb moisture within a certain period of use. However, its absorption capacity is insufficient for prolonged open-air use, leading to contact between the molten salt and a large amount of external gas, resulting in the molten salt absorbing water or impurities from the gas, causing it to deteriorate. Therefore, this invention preferably completely seals the molten salt and the inorganic filler inside the module body.

[0030] As a preferred technical solution of the present invention, the molten salt includes a mixture formed by any one or at least two combinations of halide molten salt, nitrate molten salt, carbonate molten salt or fluoroborate molten salt. Typical but non-limiting examples of such combinations include combinations of halide molten salt and nitrate molten salt, combinations of halide molten salt and carbonate molten salt, combinations of halide molten salt and fluoroborate molten salt, combinations of nitrate molten salt and carbonate molten salt, combinations of nitrate molten salt and fluoroborate molten salt, and combinations of carbonate molten salt and fluoroborate molten salt.

[0031] The molten salt is a liquid after heat storage (melting) and a solid after heat release.

[0032] In a second aspect, the present invention provides a method for using the thermal storage module described in the first aspect, the method comprising:

[0033] During the cycle of use, change the orientation and / or tilt angle of the thermal storage module to avoid molten salt phase separation.

[0034] The orientation change of the thermal storage module described in this invention refers to placing the module upright, upside down, or with its side facing down. Changing the orientation and / or tilt angle allows any small amount of phase-separated salt particles that have formed within the thermal storage channels during long-term use and repeated heating and cooling cycles to redistribute due to gravity when the module's placement is changed. Simultaneously, it allows the inorganic fiber material deposited downwards in the thermal storage channels due to gravity to redistribute, which facilitates the redissolution of molten salt and slows down phase separation, while also promoting the uniform re-dispersion of inorganic fibers. For single-sided sealed honeycomb ceramics, the fundamental principle for changing the module's orientation is to prevent molten salt from flowing out.

[0035] Thirdly, the present invention provides an application of the heat storage module described in the first aspect, the application including absorbing and reusing waste heat from industrial waste gas for reheating or absorbing and reusing waste heat from industrial heat sources for reheating.

[0036] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0037] (1) This invention fills inorganic fillers, especially sepiolite fibers, and utilizes their porous, lightweight and water-absorbing characteristics to make the numerous micropores buffer the increase in gas pressure in the closed channels during high-temperature heat storage. At the same time, it can absorb the small amount of water that enters the channels from the outside during the "breathing" process of the closed channels during the hot and cold cycles, thereby greatly improving the stability and service life of the molten salt.

[0038] (2) By filling inorganic fillers, the present invention generates many heterogeneous contact sites between the molten salt and these inorganic fillers, thereby successfully inducing the generation of crystal nuclei during the rapid cooling process of the molten salt, so as to cause uniform cooling and crystallization of the molten salt, thus solving the problem of molten salt being easily overcooled.

[0039] (3) The introduction of boron nitride fiber in this invention significantly improves the thermal conductivity inside the molten salt, making the heat storage and release speed of the module faster.

[0040] (4) The present invention introduces fibrous sepiolite, which has a significant thickening effect. Combined with the blocking effect of boron nitride fibers, it makes it difficult for the crystals generated by phase separation inside the molten salt to settle and accumulate, thus effectively preventing the phase separation phenomenon of molten salt. Attached Figure Description

[0041] Figure 1 and Figure 2 These are schematic diagrams of partial cross-sections of the thermal storage module obtained in Example 1 after thermal storage and after thermal release.

[0042] Figure 3 This is a three-dimensional schematic diagram of the thermal storage module obtained in Example 1;

[0043] Figure 4 yes Figure 3 A cross-sectional view along the AA direction;

[0044] Figure 5 This is a schematic diagram of the thermal storage module obtained in Example 1 when it is placed vertically in the direction of the arrow;

[0045] Figure 6 yes Figure 5 A cross-sectional view along the AA direction;

[0046] Figure 7 This is a schematic diagram of the thermal storage module obtained in Example 1 with its side facing down;

[0047] Figure 8 and Figure 9 These are schematic diagrams of partial cross-sections of the heat storage module obtained in Example 2 after heat storage and after heat release.

[0048] Figure 10 This is a three-dimensional schematic diagram of the thermal storage module obtained in Example 2;

[0049] Figure 11 yes Figure 10 A cross-sectional view along the AA direction;

[0050] Figure 12 This is a scanning electron microscope image of the sepiolite fibers used in Example 2;

[0051] Figure 13 This is a three-dimensional schematic diagram of the heat storage module obtained in Example 3;

[0052] Figure 14 yes Figure 13 A cross-sectional view along the AA direction;

[0053] In the diagram: 1-Module body, 2-Inorganic filler, 3-Heat transfer channel, 4-Heat storage channel, 5-Molten salt that is liquid after heat storage, 6-Molten salt that is solid after heat release, 7-Indicator arrow facing upwards, 8-Molten salt filling scale line, 9-Sealing ceramic. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] Example 1

[0056] This embodiment provides a thermal storage module containing inorganic fillers, such as... Figure 1-7As shown, the heat storage module includes a module body 1, the module body 1 has a heat storage channel 4 inside, the heat storage channel 4 is filled with molten salt and inorganic filler 2, and the molten salt and inorganic filler 2 are completely sealed inside the module body 1; the molten salt is liquid molten salt 5 after heat storage, and solid molten salt 6 after heat release.

[0057] The module body 1 is a cordierite honeycomb ceramic with a square outer contour. The honeycomb ceramic is 1m long, the cross-section of the channel is square, the side length of the square is 10mm, the thickness of the wall between two adjacent channels is 2mm, and the number of channels is 10 (horizontal) × 10 (vertical) = 100.

[0058] The module body 1 also has a heat transfer channel 3, which penetrates the module body 1 and forms an opening on the surface of the module body 1 for the flow of refrigerant or heat medium; the heat storage channel 4 penetrates the module body 1 and forms an opening on the surface of the module body 1, and sealing ceramics 9 are provided at both ends of the opening of the heat storage channel 4, which completely seal the molten salt and the inorganic filler 2 inside the module body 1; the heat storage channel 4 and the heat transfer channel 3 are arranged in a staggered manner, that is, any two adjacent heat storage channels 4 are separated by the heat transfer channel 3;

[0059] The molten salt is a ternary molten salt of KNO3-NaNO3-NaCl (mass percentages of 70.3%, 19.7%, and 10%, respectively), with a melting temperature of 228°C, a complete melting temperature of 240°C, and a molten salt density of 1.9 g / mL at this temperature.

[0060] The inorganic filler 2 is boron nitride fiber with a diameter of 10 μm, a true density of 2.29 g / mL, and an initial oxidation temperature of 850℃;

[0061] Based on the density of the molten salt after complete melting being 1.9 g / mL and the true density of the boron nitride fiber being 2.29 g / mL, the volume filling ratio of the molten salt in each heat storage channel 4 is 59%. The sum of the volume of the completely melted molten salt and the volume of the boron nitride fiber is 80% of the volume of the heat storage channel 4. The mass of the inorganic filler 2 accounts for 30% of the total mass of the molten salt and the inorganic filler, that is, a total of 5605 g of molten salt and 2400 g of boron nitride fiber are filled.

[0062] Figure 5 This is a perspective view showing the obtained thermal storage module placed vertically along the indicator arrow. The exterior of the module body 1 is marked with an upward-pointing indicator arrow 7 and molten salt filling scale lines 8. Figure 6 yes Figure 5 Cross-sectional view along the AA direction. Figure 7When the obtained thermal storage module is tilted (side down), the bottom diagram is visible, and the thermal storage channel 4 at the bottom is completely sealed by the ceramic 9.

[0063] Example 2

[0064] This embodiment provides a thermal storage module containing inorganic fillers, such as... Figure 8-11 As shown, the heat storage module includes a module body 1, the module body 1 has a heat storage channel 4 inside, the heat storage channel 4 is filled with molten salt and inorganic filler 2, and the molten salt and inorganic filler 2 are completely sealed inside the module body 1; the molten salt is liquid molten salt 5 after heat storage, and solid molten salt 6 after heat release.

[0065] The module body 1 is a silicon carbide honeycomb ceramic with a circular outer contour. The diameter of the outer circle is 20cm, the length of the honeycomb ceramic is 1m, the cross-sectional shape of the channel is a regular hexagon, the diameter of its circumscribed circle is 8mm, the thickness of the hole wall between two adjacent channels is 1mm, and the number of channels is 560.

[0066] The module body 1 also has a heat transfer channel 3, which penetrates the module body 1 and forms an opening on the surface of the module body 1 for the flow of refrigerant or heat medium; the heat storage channel 4 penetrates the module body 1 and forms an opening on the surface of the module body 1, and sealing ceramics 9 are provided at both ends of the opening of the heat storage channel 4, which completely seal the molten salt and the inorganic filler 2 inside the module body 1; the heat storage channel 4 and the heat transfer channel 3 are arranged in a staggered manner, that is, any two adjacent heat storage channels 4 are separated by the heat transfer channel 3;

[0067] The molten salt is KNO3-NaNO3 (40% and 60% by mass, respectively), with a melting temperature of 240°C and a complete melting temperature of 260°C;

[0068] The inorganic filler 2 is sepiolite fiber, which has undergone heat treatment at 600℃; for example... Figure 12 The image shown is a scanning electron microscope image of the sepiolite fiber, with a scale bar of 20 μm. It can be seen from the image that the length of the sepiolite fiber is between 8 and 30 μm and the fiber diameter is between 1 and 2 μm.

[0069] Based on the density of the molten salt after complete melting being 1.84 g / mL and the true density of the sepiolite fiber being 2.1 g / mL, the volume filling ratio of the molten salt in each heat storage channel 4 is 50%. The sum of the volume of the completely melted molten salt and the volume of the sepiolite fiber is 50.44% of the volume of the heat storage channel 4. The mass of the inorganic filler 2 accounts for 1% of the total mass of the molten salt and the inorganic filler, that is, a total of 10700 g of molten salt and 107 g of sepiolite fiber are filled.

[0070] Example 3

[0071] This embodiment provides a thermal storage module containing inorganic fillers, such as... Figure 13 and 14 As shown, the heat storage module includes a module body 1, the module body 1 has a heat storage channel 4 inside, the heat storage channel 4 is filled with molten salt and inorganic filler 2, and the molten salt and inorganic filler 2 are completely sealed inside the module body 1; the molten salt is liquid molten salt 5 after heat storage, and solid molten salt 6 after heat release.

[0072] The module body 1 is a mullite honeycomb ceramic with a circular outer contour. The honeycomb ceramic is 1m long, and the cross-sectional shape of the channel is square with a side length of 5mm. The thickness of the wall between two adjacent channels is 0.5mm, and the number of channels is 20 (horizontal) × 20 (vertical) = 400.

[0073] The module body 1 also has a heat transfer channel 3, which penetrates the module body 1 and forms an opening on the surface of the module body 1 for the flow of refrigerant or heat medium; the heat storage channel 4 penetrates the module body 1 and forms an opening on the surface of the module body 1, and sealing ceramics 9 are provided at both ends of the opening of the heat storage channel 4, which completely seal the molten salt and the inorganic filler 2 inside the module body 1; the heat storage channel 4 and the heat transfer channel 3 are arranged in a staggered manner, that is, any two adjacent heat storage channels 4 are separated by the heat transfer channel 3;

[0074] The molten salt is a ternary molten salt of KNO3-NaNO3-Ca(NO3)2 (mass percentages of 43%, 15%, and 42%, respectively), with a melting temperature of 140°C and a complete melting temperature of 160°C.

[0075] The inorganic filler 2 is boron nitride fiber with a diameter of 3 μm, a true density of 2.29 g / mL, and an initial oxidation temperature of 830℃;

[0076] The density of the molten salt after complete melting is 1.91 g / mL. The volume filling ratio of the molten salt in each heat storage channel 4 is 51.6%. The sum of the volume of the completely melted molten salt and the volume of the boron nitride fiber is 62% of the volume of the heat storage channel 4. The mass of the inorganic filler 2 accounts for 20% of the total mass of the molten salt and the inorganic filler, that is, a total of 4925 g of molten salt and 1230 g of boron nitride fiber are filled.

[0077] Figure 1-14 This is for illustrative purposes only. The number of channels, channel structure, external shape of the honeycomb ceramic, and volume ratio of molten salt and inorganic fillers in the channels shown in the figure are all based on the description in the corresponding embodiment.

[0078] Example 4

[0079] This embodiment provides a thermal storage module containing inorganic filler. The thermal storage module includes a module body, the interior of which has thermal storage channels. The interior of the thermal storage channels is filled with molten salt and inorganic filler, and the molten salt and inorganic filler are completely sealed inside the module body.

[0080] The module body is made of alumina honeycomb ceramic. The length of the honeycomb ceramic is 1m. The cross-sectional shape of the channel is square with a side length of 12mm. The thickness of the wall between two adjacent channels is 1mm. The number of channels is 10 (horizontal) × 10 (vertical) = 100.

[0081] The module body also has heat transfer channels that penetrate the module body and form openings on the surface of the module body for the flow of refrigerant or heat transfer medium; the heat storage channels penetrate the module body and form openings on the surface of the module body, and sealing ceramics are provided at both ends of the openings of the heat storage channels, which completely seal the molten salt and the inorganic filler inside the module body; the heat storage channels and the heat transfer channels are arranged in a staggered manner, that is, any two adjacent heat storage channels are separated by the heat transfer channels;

[0082] The molten salt is LiNO3-NaNO3 (49% and 51% by mass, respectively), with a melting temperature of 194°C and a complete melting temperature of 200°C.

[0083] The inorganic filler is sepiolite fiber and boron nitride fiber; the boron nitride fiber has a diameter of 5 μm and an initial oxidation temperature of 880℃; the sepiolite fiber is heat-treated at 500℃.

[0084] Based on the density of the molten salt after complete melting being 1.85 g / mL, the true density of the sepiolite fiber is 2.1 g / mL, the true density of the boron nitride fiber is 2.29 g / mL, the volume filling ratio of the molten salt in each heat storage channel is 80%, the sum of the volume of the completely melted molten salt, the volume of the sepiolite fiber, and the volume of the boron nitride fiber is 90% of the volume of the heat storage channel, and the mass of the inorganic filler accounts for 12.87% of the total mass of the molten salt and the inorganic filler, that is, a total of 10700 g of molten salt, 756 g of sepiolite fiber, and 824 g of boron nitride fiber are filled.

[0085] Example 5

[0086] This embodiment provides a thermal storage module containing inorganic filler. The thermal storage module includes a module body, the interior of which has thermal storage channels. The interior of the thermal storage channels is filled with molten salt and inorganic filler, and the molten salt and inorganic filler are completely sealed inside the module body.

[0087] The module body is cordierite honeycomb ceramic, the length of the honeycomb ceramic is 1m, the cross-sectional shape of the channel is square, the side length of the square is 10mm, the thickness of the wall between two adjacent channels is 2mm, and the number of channels is 10 (horizontal) × 10 (vertical) = 100.

[0088] The module body also has heat transfer channels that penetrate the module body and form openings on the surface of the module body for the flow of refrigerant or heat transfer medium; the heat storage channels penetrate the module body and form openings on the surface of the module body, and sealing ceramics are provided at both ends of the openings of the heat storage channels, which completely seal the molten salt and the inorganic filler inside the module body; the heat storage channels and the heat transfer channels are arranged in a staggered manner, that is, any two adjacent heat storage channels are separated by the heat transfer channels;

[0089] The molten salt is LiNO3-Na2CO3-K2CO3 (mass percentages of 33%, 32%, and 35%, respectively), with a melting temperature of 397°C and a complete melting temperature of 408°C;

[0090] The inorganic filler is sepiolite fiber, which is heat-treated at 300°C.

[0091] Based on the density of the molten salt after complete melting being 1.98 g / mL, the true density of the sepiolite fiber is 2.1 g / mL. The volume filling ratio of the molten salt in each heat storage channel is 80%. The sum of the volume of the completely melted molten salt and the volume of the sepiolite fiber is 95% of the volume of the heat storage channel. The mass of the inorganic filler accounts for 16.6% of the total mass of the molten salt and the inorganic filler, that is, a total of 7520 g of molten salt and 1495 g of sepiolite fiber are filled.

[0092] Example 6

[0093] This embodiment provides a thermal storage module containing inorganic filler. The thermal storage module includes a module body, the interior of which has thermal storage channels. The interior of the thermal storage channels is filled with molten salt and inorganic filler, and the molten salt and inorganic filler are completely sealed inside the module body.

[0094] The module body is a silicon carbide honeycomb ceramic with a square outer contour. The side length of the square outer contour is 30cm, the length of the honeycomb ceramic is 1m, the cross-sectional shape of the channel is a regular hexagon, the diameter of its circumscribed circle is 15mm, the thickness of the hole wall between two adjacent channels is 1.5mm, and the number of channels is 472.

[0095] The module body also has heat transfer channels that penetrate the module body and form openings on the surface of the module body for the flow of refrigerant or heat transfer medium; the heat storage channels penetrate the module body and form openings on the surface of the module body, and sealing ceramics are provided at both ends of the openings of the heat storage channels, which completely seal the molten salt and the inorganic filler inside the module body; the heat storage channels and the heat transfer channels are arranged in a staggered manner, that is, any two adjacent heat storage channels are separated by the heat transfer channels;

[0096] The molten salt is KNO3-NaNO3 (40% and 60% by mass, respectively), with a melting temperature of 240°C and a complete melting temperature of 260°C;

[0097] The inorganic filler is sepiolite fiber and boron nitride fiber; the boron nitride fiber has a diameter of 10 μm, a true density of 2.29 g / mL, and an initial oxidation temperature of 880℃; the sepiolite fiber is heat-treated at 450℃.

[0098] Based on the density of the molten salt after complete melting being 1.84 g / mL, the true density of the sepiolite fiber is 2.1 g / mL. The volume filling ratio of the molten salt in each heat storage channel is 52%. The sum of the volume of the completely melted molten salt and the volume of the sepiolite fiber is 60% of the volume of the heat storage channel. The total mass of the inorganic filler accounts for 15.5% of the total mass of the molten salt. That is, a total of 33015 g of molten salt, 2163 g of sepiolite fiber, and 3893 g of boron nitride fiber are filled.

[0099] Example 7

[0100] This embodiment provides a thermal storage module containing inorganic filler. The thermal storage module includes a module body, the interior of which has thermal storage channels. The interior of the thermal storage channels is filled with molten salt and inorganic filler, and the molten salt and inorganic filler are completely sealed inside the module body.

[0101] The module body is cordierite honeycomb ceramic, the length of the honeycomb ceramic is 1m, the cross-sectional shape of the channel is square, the side length of the square is 10mm, the thickness of the wall between two adjacent channels is 2mm, and the number of channels is 10 (horizontal) × 10 (vertical) = 100.

[0102] The module body also has heat transfer channels that penetrate the module body and form openings on the surface of the module body for the flow of refrigerant or heat transfer medium; the heat storage channels penetrate the module body and form openings on the surface of the module body, and sealing ceramics are provided at both ends of the openings of the heat storage channels, which completely seal the molten salt and the inorganic filler inside the module body; the heat storage channels and the heat transfer channels are arranged in a staggered manner, that is, any two adjacent heat storage channels are separated by the heat transfer channels;

[0103] The molten salt is NaF-NaBF4 (mass percentages of 3% and 97% respectively), with a melting temperature of 385°C and a complete melting temperature of 395°C;

[0104] The inorganic filler is sepiolite fiber and boron nitride fiber; the boron nitride fiber has a diameter of 4-10 μm, a true density of 2.29 g / mL, and an initial oxidation temperature of 870℃; the sepiolite fiber is heat-treated at 550℃.

[0105] Based on the density of the molten salt after complete melting being 1.75 g / mL, the true density of the sepiolite fiber is 2.1 g / mL. The volume filling ratio of the molten salt in each heat storage channel is 52%. The sum of the volume of the completely melted molten salt, the volume of the sepiolite fiber, and the volume of the boron nitride fiber is 65% of the volume of the heat storage channel. The mass of the inorganic filler accounts for 17.1% of the total mass of the molten salt and the inorganic filler, that is, a total of 4550 g of molten salt, 325 g of sepiolite fiber, and 1134 g of boron nitride fiber are filled.

[0106] Example 8

[0107] This embodiment provides a thermal storage module containing inorganic filler. The thermal storage module is exactly the same as that in Embodiment 1, except that the inorganic filler is replaced by silicon carbide fiber with the same shape and size instead of boron nitride fiber.

[0108] Example 9

[0109] This embodiment provides a thermal storage module containing inorganic filler. Except for replacing the inorganic filler with sepiolite fiber in embodiment 2 with carbon fiber of the same shape and size, the thermal storage module is exactly the same as that in embodiment 1.

[0110] Comparative Examples 1-7

[0111] The thermal storage modules in Examples 1-7 were respectively made so that the corresponding inorganic fillers were not filled into the thermal storage channels, and only molten salt was retained, resulting in thermal storage modules without inorganic fillers, which served as a control with the corresponding examples.

[0112] The heat storage and release performance of the thermal storage modules obtained in the embodiments and comparative examples were tested, and the results are recorded in Table 1.

[0113] Table 1

[0114] project Thermal storage temperature range (°C) Heat release temperature range (°C) Phase change heat capacity (kJ) Maximum supercooling temperature (°C) Example 1 280～400 100～200 710 4～11 Example 2 280～500 150～220 1398 10～15 Example 3 160～400 60～100 782 5～10 Example 4 250～400 100～200 1618 6～13 Example 5 400～600 200～340 1149 12～19 Example 6 280～500 150～220 4600 7～14 Example 7 400～600 200～340 682 8～16 Example 8 280～400 100～200 710 7～15 Example 9 280～500 150～220 1398 5～15

[0115] The highest subcooling temperatures of the thermal storage modules obtained in Comparative Examples 1-7 were 30–55℃ (Comparative Example 1), 30–40℃ (Comparative Example 2), 39–50℃ (Comparative Example 3), 28–49℃ (Comparative Example 4), 30–45℃ (Comparative Example 5), 38–55℃ (Comparative Example 6), and 30–45℃ (Comparative Example 7), respectively. It is evident that the addition of inorganic fillers in these examples effectively reduced the highest subcooling temperature, and the resulting thermal storage modules containing inorganic fillers exhibited good thermal storage and release performance.

[0116] The molten salt phase separation phenomenon of the thermal storage modules obtained in Examples 1-7 was also effectively mitigated. The thermal storage module obtained in Example 1 did not experience phase separation after 5000 cycles of hot and cold cycling; the thermal storage module obtained in Example 2 did not experience phase separation after 5500 cycles of hot and cold cycling; in Example 3, due to the blocking effect of a large amount of boron nitride fibers, phase separation did not occur after 8700 cycles of hot and cold cycling; the thermal storage module obtained in Example 4 did not experience phase separation after 9000 cycles of hot and cold cycling; in Example 5, a large amount of sepiolite fibers significantly reduced the pressure fluctuation in the pores, and the obtained thermal storage module did not rupture after 8000 cycles of hot and cold cycling; in Examples 6 and 7, both sepiolite fibers and boron nitride fibers were added simultaneously, and the two worked together to ensure that the obtained thermal storage modules did not rupture after 10000 cycles of hot and cold cycling.

[0117] Compared to Examples 8 and 9, Example 1 shows an increase in the maximum supercooling temperature of the module in Example 8 due to the significantly lower thermal conductivity of SiC fibers (≈300 W / mK) compared to BN (730 W / mK). However, since SiC fibers also possess a certain ability to delay phase separation, the module's service life did not decrease significantly. Example 9, due to the introduction of carbon fibers with good thermal conductivity, showed a decrease in the maximum supercooling temperature. However, because the molten salt used was nitrate molten salt, a small amount of external gas entered the heat storage channels during the alternating heating and cooling process, leading to partial decomposition of the molten salt. Simultaneously, the weak reducing properties of carbon fibers caused the nitrate to be reduced and generate gas, causing the module to crack after 1500 cycles of heating and cooling.

[0118] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0119] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0120] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0121] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A thermal storage module containing inorganic filler, characterized in that, The device includes a module body, the interior of which has heat storage channels filled with molten salt and inorganic fillers. The sum of the volume of the molten salt after melting and the volume of the inorganic fillers is 50% to 95% of the volume of the heat storage channels. The amount of inorganic fillers added is 1% to 30% of the total mass of the molten salt and inorganic fillers. The inorganic fillers include sepiolite fibers and / or boron nitride fibers. The sepiolite fibers are pre-treated with heat at 300 to 600°C. The boron nitride fibers have a diameter of 3 to 10 μm, an apparent density of 1.3 to 2 g / mL, and an initial oxidation temperature of 830 to 880°C.

2. The thermal storage module according to claim 1, characterized in that, The module body includes honeycomb ceramic.

3. The thermal storage module according to claim 2, characterized in that, The material of the honeycomb ceramic includes any one or a combination of at least two of mullite, cordierite, silicon carbide, or alumina.

4. The thermal storage module according to claim 1, characterized in that, The cross-sectional shape of the heat storage channel includes any one or a combination of at least two of the following: square, hexagonal, circular, or triangular.

5. The thermal storage module according to claim 1, characterized in that, The diameter of the circumscribed circle of the cross-sectional shape of the heat storage channel is 5~80mm.

6. The thermal storage module according to claim 1, characterized in that, The module body also has heat transfer channels that penetrate the module body and form openings on the surface of the module body for the flow of refrigerant or heat transfer medium.

7. The thermal storage module according to claim 6, characterized in that, Any two adjacent heat storage channels are separated by the heat transfer channels.

8. The thermal storage module according to claim 1, characterized in that, The heat storage channel penetrates the module body and forms an opening on the surface of the module body, and a sealing ceramic is provided at at least one end of the opening of the heat storage channel.

9. The thermal storage module according to claim 8, characterized in that, The sealing ceramic is made of the same material as the honeycomb ceramic.

10. The thermal storage module according to claim 8, characterized in that, Sealing ceramics are installed at both ends of the heat storage channel to completely seal the molten salt and the inorganic filler inside the module body.

11. The thermal storage module according to claim 1, characterized in that, The molten salt includes a mixture formed by any one or a combination of at least two of the following: halide molten salt, nitrate molten salt, carbonate molten salt, or fluoroborate molten salt.

12. A method of using a thermal storage module according to any one of claims 1-11, characterized in that, The method includes: During the cycle of use, change the orientation and / or tilt angle of the thermal storage module to avoid molten salt phase separation.

13. The use of a thermal storage module according to any one of claims 1-11, characterized in that, The applications include absorbing and reusing waste heat from industrial waste gas for reheating or absorbing and reusing waste heat from industrial heat sources for reheating.

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