Heat-conducting insulating material, tubular heating device and application of tubular heating device

Abstract

The invention provides a heat-conducting insulating material, a tubular heating device and application of the tubular heating device. The compaction density of the heat-conducting insulating material is 1.70-2.70 g / cm < 3 >; the heat-conducting insulating material comprises beryllium oxide ceramic powder, and the particle size range of the beryllium oxide ceramic powder is 40-325 meshes. The tubular heating device can be operated at a high working temperature and has a long service life so as to heat a low-heat-conduction medium in a high-temperature molten salt reactor and high-temperature molten salt energy storage. Specifically, the working temperature of the tubular heating device can reach 850-1000 DEG C, and the tubular heating device can stably work for 50 thousand hours; the heating effect of the tubular heating device cannot be reduced due to moisture absorption of a medium during high-temperature operation.

Description

Technical Field

[0001] The invention relates to a heat-conducting insulating material, a tubular heating device and applications thereof. Background Art

[0002] Tubular heaters are also called tubular heating elements. They generally use alloy heating wires as the heating element and a metal tube as the outer shell. There are lead rods (wires) at one or both ends of the metal tube, and the metal tube is filled with dense insulating medium.

[0003] Existing tubular heaters generally use magnesium oxide powder as an insulating filling material. When used to heat low thermal conductivity media (such as still air), the maximum operating temperature is only 850°C, and a few can be used at 950°C for a short time. If the tubular heater is heated at a higher temperature or for a longer period of time, the heating element (alloy heating wire) is easily damaged by overheating due to the thermal conductivity of magnesium oxide powder. In addition, magnesium oxide is hygroscopic, or the magnesium hydroxide impurities contained in magnesium oxide decompose to generate water at high temperatures. This moisture will cause the insulation performance of the tubular heater to deteriorate, thereby causing damage to the heater.

[0004] Patent application CN108476560A discloses a heater assembly. The insulating filling medium of the heater assembly adopts materials with desired dielectric strength, thermal conductivity (between 60-180 W / m·K) and life, including magnesium oxide (MgO), zirconium oxide (ZrO2) or aluminum nitride (AlN). In order to solve the problem that the operating temperature of heaters in the semiconductor processing industry is lower than 830°C, the patent aims to increase the operating temperature of the tubular heater to above 850°C, or even above 1000°C; however, the actual upper limit of the operating temperature of the heater assembly is not recorded in the patent application, nor is the service life of the heater tested. In addition, the use of materials such as zirconium oxide (ZrO2) or aluminum nitride (AlN) does not solve the problem of performance degradation caused by moisture absorption of the insulating thermal conductive medium of the tubular heater during processing, manufacturing and use. Regarding the above problems, patent application CN113086954A discloses that aluminum nitride is very easy to deliquesce, and the higher the temperature, the faster the hydrolysis; in addition, patent application CN116178054A records that how to avoid the hydrolysis of aluminum nitride is the core key technology in the field of aluminum nitride ceramic materials; it can be seen that since aluminum nitride will hydrolyze, it will affect the thermal conductivity of the filling medium; patent application CN218950030U provides a moisture-proof storage device to address the problem of hygroscopicity of zirconium oxide; it can be seen that zirconium oxide is also hygroscopic and will also affect the thermal conductivity of the filling medium.

[0005] From the above, it can be seen that during the manufacturing and high-temperature operation of existing tubular heaters, the filling material absorbs moisture, resulting in a decrease in insulation and thermal conductivity, which limits the operating temperature and service life of the tubular heater. Therefore, there is no precedent for the long-term application of tubular heaters at high temperatures of 850-1000℃.

[0006] Therefore, it is urgent to provide a heat-conducting insulating material that can be used for a tubular heating device, so that it can heat a low heat-conducting medium (such as still air), and can enable the tubular heating device to operate at a higher working temperature and have a longer service life. Summary of the invention

[0007] In order to solve the defects of the above-mentioned prior art that the working temperature of the tubular heating device does not meet the standard and the life is short, the present invention provides a thermally conductive insulating material, a tubular heating device and its application. The thermally conductive insulating material of the present invention can enable the tubular heating device to operate at a higher working temperature and have a longer life; specifically, the working temperature of the tubular heating device can reach 850-1000℃ and work stably for more than 50,000 hours; the tubular heating device will not reduce the heating effect due to moisture absorption of the medium during high-temperature operation.

[0008] The particle size, specific surface area, density and other properties of beryllium oxide powder are quite different from those of conventional thermal conductive insulating materials in this field (such as magnesium oxide (MgO), zirconium oxide (ZrO2) or aluminum nitride (AlN) powders). Specifically, the properties of magnesium oxide, zirconium oxide and aluminum nitride are as follows: According to JB / T 8508-1996 "Electrical Grade Magnesium Oxide", the particle size of magnesium oxide powder is 40-325 mesh (about 45-425 μm), and the tap density is ≥2.3 g / cm 3 (Loose density 1.5-1.9 g / cm 3 According to SJ 20637-97 "Specifications for Aluminum Nitride Powder for Electronic Ceramics", the particle size of aluminum nitride powder is divided into three grades: ≤8 μm, ≤6 μm, and ≤5 μm. The specific surface area is also divided into three grades: >1.0 m 2 / g, >2.0 m 2 / g, >3.0 m 2 / g, bulk density ≤0.90g / cm 3 According to YS∕T 1270-2018 "Yttria Stabilized Zirconia Powder", the particle size of zirconium oxide powder is 15-125 μm, and the bulk density is ≥1.5 g / cm 3 Compared with the above thermally conductive insulating materials, according to SJ 20867-2003 Specifications for Beryllium Oxide Powder Materials for Electronic Ceramics, the bulk density of beryllium oxide powder is only 0.3-0.4 g / cm 3 , and the filling density is generally 1.2-1.5 times the bulk density; at this filling density, beryllium oxide powder exhibits poor thermal conductivity.

[0009] Since the thermal conductivity of beryllium oxide powder is not ideal and the thermal conductivity of beryllium oxide ceramic powder is rarely reported, it is not common to use it as a thermal conductive material for tubular heaters. In addition, the process of making beryllium oxide powder into beryllium oxide ceramics and crushing it is quite complicated, and existing thermally conductive insulating materials such as magnesium oxide can meet the technical requirements of most application scenarios. Only in some special application scenarios, such as those involved in this patent, with high temperatures exceeding 850°C, the heating object is a low thermal conductivity medium such as air, and long-term use is required. Under harsh conditions, the limitations of the existing technology will become apparent. Therefore, there have been no reports on the study of the thermal conductivity of beryllium oxide ceramic powder and its application in tubular heaters.

[0010] This application achieves the above technical effects through the following technical solutions:

[0011] The present invention provides a thermally conductive insulating material, wherein the compacted density of the thermally conductive insulating material is 1.7-2.7 g / cm 3 ; The thermally conductive insulating material includes beryllium oxide ceramic powder with a particle size of 40-325 mesh.

[0012] In the present invention, the beryllium oxide ceramic powder is a beryllium oxide ceramic material obtained by sintering beryllium oxide powder at high temperature to achieve ceramicization and then crushing it. The material has a dense and stable structure and exhibits excellent high-temperature insulation and thermal conductivity. Due to its stable crystal structure and low porosity, the material is not easy to absorb moisture during the manufacture and high-temperature operation of the tubular heater, thereby ensuring that its insulation and thermal conductivity will not be significantly reduced. In addition, its high thermal conductivity can quickly conduct heat, effectively reduce the temperature difference between the heating wire and the metal sleeve, thereby preventing the wire from overheating, and significantly improving the reliability and service life of the tubular heater. The crushing process can be carried out according to the embodiment of CN111517809A.

[0013] In some embodiments, the compacted density of the thermally conductive insulating material is 1.83-2.70 g / cm 3 , preferably 1.95-2.70 g / cm 3 , more preferably 2.12-2.70 g / cm 3 , and more preferably 2.35-2.46 g / cm 3 At this compaction density, the contact area between the thermally conductive insulating material and the heating wire increases, and heat can be more effectively transferred from the heating wire to the thermally conductive insulating material, and then transferred to the metal sleeve and the heated object through the thermally conductive insulating material. This not only improves the heat conduction efficiency, but also ensures uniform heat distribution. At the same time, the appropriate compaction density avoids the risk of damage to the tubular heating device due to excessive local thermal stress.

[0014] In the present invention, the test method for the D50 particle size of the beryllium oxide ceramic powder includes conventional sieving methods in the art, such as "Sieving Method for Determination of Particle Size in Inorganic Chemical Industry" GB / T 21524-2008; the D50 particle size of the beryllium oxide ceramic powder is measured by the sieve hole size; the D50 particle size refers to the median particle size.

[0015] In the present invention, a particle size of 40-100 mesh can be regarded as a coarse powder, a particle size of 100-200 mesh can be regarded as a medium powder, and a particle size of 200-325 mesh can be regarded as a fine powder.

[0016] In some embodiments, the D50 particle size of the beryllium oxide ceramic powder is 60-200 mesh, preferably 60-140 mesh, and more preferably 70-110 mesh, such as 74 mesh, 80 mesh or 110 mesh.

[0017] In the present invention, controlling the D50 particle size of the beryllium oxide ceramic powder to be 60-200 mesh is crucial to ensure quality. When the D50 particle size is too large, that is, there are too many coarse particles, the beryllium oxide ceramic powder will be easily crushed during the mixing and transportation process, resulting in irregularly shaped small particles and fine powder, which in turn affects the fluidity of the powder; and the fine particles and coarse particles formed are prone to segregation during the powder pouring process, making it difficult to evenly distribute them in the mold cavity, and stratification defects are likely to occur. When the D50 particle size is too small, that is, there are too many fine powders, the air permeability of the beryllium oxide ceramic powder will deteriorate, not only the fluidity is poor during the powder pouring process, but also it is difficult to vent during compaction, and pores are likely to occur.

[0018] In some embodiments, the mass content of the beryllium oxide ceramic powder with a particle size of 40-325 mesh in the thermally conductive insulating material is 90 wt %-99.99 wt %.

[0019] In some embodiments, the mass content of the beryllium oxide ceramic powder with a particle size of 40-80 mesh in the thermally conductive insulating material is 40 wt %-60 wt %, preferably 40 wt %-58 wt %.

[0020] In some embodiments, the mass content of the beryllium oxide ceramic powder with a particle size of 80-200 mesh in the thermally conductive insulating material is 25 wt%-45 wt%, preferably 35 wt%-40 wt%.

[0021] In some embodiments, the mass content of the beryllium oxide ceramic powder with a particle size of 200-325 mesh in the thermally conductive insulating material is 5 wt %-15 wt %.

[0022] In some embodiments, the mass content of beryllium oxide ceramic powder with a particle size less than 40 mesh in the thermally conductive insulating material is less than or equal to 0.1 wt %; wherein, "particle size less than 40 mesh" here means less than 40 in value, and those skilled in the art should understand that the particle size of the beryllium oxide ceramic powder is larger within this range.

[0023] In some embodiments, the mass content of beryllium oxide ceramic powder with a particle size greater than 325 mesh in the thermally conductive insulating material is less than or equal to 10 wt %; wherein, "particle size greater than 325 mesh" here means greater than 325 in value, and those skilled in the art should understand that the particle size of beryllium oxide ceramic powder is smaller within this range.

[0024] In a specific embodiment, the mass content of the beryllium oxide ceramic powder with a particle size of 40-60 mesh in the thermally conductive insulating material is 20 wt%-30 wt%, for example, 20 wt%, 25 wt% or 30 wt%.

[0025] In a specific embodiment, the mass content of the beryllium oxide ceramic powder with a particle size of 60-80 mesh in the thermally conductive insulating material is 20 wt%-30 wt%, preferably 20 wt%-28 wt%, for example 20 wt%, 25 wt% or 28 wt%.

[0026] In a specific embodiment, the mass content of the beryllium oxide ceramic powder with a particle size of 80-140 mesh in the thermally conductive insulating material is 15 wt%-25 wt%, preferably 20 wt%-25 wt%, for example 20 wt% or 25 wt%.

[0027] In a specific embodiment, the mass content of the beryllium oxide ceramic powder with a particle size of 140-200 mesh in the thermally conductive insulating material is 10 wt%-20 wt%, preferably 10 wt%-18 wt%, for example 10 wt%, 15 wt% or 18 wt%.

[0028] In a specific embodiment, the mass content of the beryllium oxide ceramic powder with a particle size of 200-325 mesh in the thermally conductive insulating material is 5 wt%, 8 wt% or 15 wt%.

[0029] In a specific embodiment, the mass content of the beryllium oxide ceramic powder having a particle size greater than 325 mesh in the thermally conductive insulating material is less than or equal to 7 wt %, for example, 2 wt % or 7 wt %.

[0030] In one embodiment, the thermally conductive insulating material includes 25wt% beryllium oxide ceramic powder with a particle size of 40-60 mesh, 25wt% beryllium oxide ceramic powder with a particle size of 60-80 mesh, 25wt% beryllium oxide ceramic powder with a particle size of 80-140 mesh, 15wt% beryllium oxide ceramic powder with a particle size of 140-200 mesh, and 8wt% beryllium oxide ceramic powder with a particle size of 200-325 mesh.

[0031] The thermally conductive insulating material may contain less than or equal to 0.1 wt % of beryllium oxide ceramic powder having a particle size less than 40 meshes and less than or equal to 2 wt % of beryllium oxide ceramic powder having a particle size greater than 325 meshes.

[0032] In one embodiment, the thermally conductive insulating material includes 30wt% beryllium oxide ceramic powder with a particle size of 40-60 mesh, 28wt% beryllium oxide ceramic powder with a particle size of 60-80 mesh, 25wt% beryllium oxide ceramic powder with a particle size of 80-140 mesh, 10wt% beryllium oxide ceramic powder with a particle size of 140-200 mesh, and 5wt% beryllium oxide ceramic powder with a particle size of 200-325 mesh.

[0033] The thermally conductive insulating material may contain less than or equal to 0.1 wt % of beryllium oxide ceramic powder having a particle size less than 40 meshes and less than or equal to 2 wt % of beryllium oxide ceramic powder having a particle size greater than 325 meshes.

[0034] In one embodiment, the thermally conductive insulating material includes 20wt% beryllium oxide ceramic powder with a particle size of 40-60 mesh, 20wt% beryllium oxide ceramic powder with a particle size of 60-80 mesh, 20wt% beryllium oxide ceramic powder with a particle size of 80-140 mesh, 18wt% beryllium oxide ceramic powder with a particle size of 140-200 mesh, and 15wt% beryllium oxide ceramic powder with a particle size of 200-325 mesh.

[0035] The thermally conductive insulating material may contain less than or equal to 0.1 wt % of beryllium oxide ceramic powder having a particle size less than 40 meshes and less than or equal to 7 wt % of beryllium oxide ceramic powder having a particle size greater than 325 meshes.

[0036] In one embodiment, the manufacturer of the beryllium oxide ceramic powder is Shanghai Feixing Special Ceramics Factory.

[0037] The present invention provides a tubular heating device, which comprises a tubular heating device and the thermally conductive insulating material as described above, wherein the thermally conductive insulating material is filled in the tubular heating device.

[0038] In the present invention, preferably, the tubular heating device comprises a metal sleeve, a heating wire and the thermally conductive insulating material as described above; the metal sleeve is a hollow tubular structure and is sealed at both ends, the heating wire and the thermally conductive insulating material are both arranged inside the metal sleeve, and the thermally conductive insulating material is used to fill the gap formed by the heating wire inside the metal sleeve.

[0039] In the present invention, when the compaction density of the thermally conductive insulating material is too low, there may be large air gaps between the heating wire and the thermally conductive insulating material, and between the thermally conductive insulating material. Air is a poor conductor of heat, and these gaps will hinder the transfer of heat, causing heat accumulation at the resistance wire position, thus affecting the life of the resistance wire.

[0040] In the present invention, when the compaction density of the thermally conductive insulating material is too high, the close contact between the thermally conductive insulating material and the heating wire may cause an increase in local thermal stress, thereby increasing the risk of damage to the tubular heating device.

[0041] In the present invention, the thermally conductive insulating material not only plays the role of fixing the heating wire, but also has the functions of insulation and thermal conductivity.

[0042] In the present invention, the heating wire material may be referred to as an electric heating wire, which generally converts electrical energy into thermal energy.

[0043] In some embodiments, the tubular heating device further includes a lead wire, which passes through one end of the metal sleeve and is connected to the heating wire.

[0044] In some embodiments, the tubular heating device further comprises a ceramic rod, wherein the ceramic rod is disposed inside the metal sleeve, and the heating wire is wound around the ceramic rod.

[0045] In a specific embodiment, the length of the ceramic rod is smaller than the length of the metal sleeve; at the end away from the heating wire, the ceramic rod abuts against the end of the metal sleeve; at the end connected to the heating wire, an insulating sealing material is provided between the ceramic rod and the end of the metal sleeve.

[0046] Among them, the tubular heating device can be divided into a "heating working area" and a "non-heating working area"; the heating working area is the area where the ceramic rod is arranged in the metal casing, and the length of the heating working area is 2 m; the non-heating working area is the area where the ceramic rod is not arranged in the metal casing, corresponding to the above-mentioned cavity.

[0047] In some embodiments, the tubular heating device has a rated voltage of 380 V, a power frequency of 50 Hz, a rated power of 12 kW, an insulation withstand voltage of 2000 V, a cold insulation resistance of ≥50 MΩ, and a cold leakage current of ≤0.5 mA.

[0048] Among them, cold insulation resistance refers to the insulation resistance value measured at room temperature; cold leakage current refers to the small current leaking through the insulating material of the electrical equipment when it is not powered.

[0049] The present invention also provides an application of the thermally conductive insulating material as described above, or the tubular heating device as described above in a molten salt reactor or molten salt energy storage.

[0050] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0051] The reagents and raw materials used in the present invention are commercially available.

[0052] The positive and progressive effects of the present invention are:

[0053] The present invention uses beryllium oxide ceramic powder that is not easy to absorb moisture as a thermally conductive insulating material, which has long-term stability; and by controlling the filling density of the thermally conductive insulating material, the thermal conductivity is improved; at the same time, thermal stress does not affect the life of the resistance wire. Heat can be more effectively transferred to the heater housing and the heated object through the thermally conductive insulating material, which not only improves the heat conduction efficiency, but also ensures the uniform distribution of heat to ensure the stability and reliability of the tubular heating device, thereby improving the maximum operating temperature and service life of the tubular heater. Specifically, the operating temperature of the tubular heating device can reach 850-1000°C and work stably for 50,000 hours; and during high-temperature operation, the thermally conductive insulating material will not cause performance degradation due to moisture absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram of the structure of the tubular heater according to Example 1 of the present application.

[0055] Description of reference numerals:

[0056] Metal casing 1

[0057] Sealed End 101

[0058] Heating wire 2

[0059] Thermally conductive insulating material 3

[0060] Ceramic rod 4

[0061] Lead 5

[0062] Fever work area 6

[0063] Non-heating working area7. DETAILED DESCRIPTION

[0064] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0065] Table 1 shows the thermally conductive insulating materials and their physical properties used in the examples and comparative examples of the present application.

[0066] Table 1

[0067]

[0068] The above table records the D50 particle size and bulk density of high-temperature magnesium oxide powder, beryllium oxide ceramic powder A, beryllium oxide ceramic powder B, and beryllium oxide ceramic powder C. The D50 particle size of the above materials is (74-110) mesh; among them, coarser powder (40 mesh and coarser ~ 80 mesh) accounts for about 50 wt%, medium powder (80 ~ 200 mesh) accounts for about 35 wt%, and finer powder (200 ~ 325 mesh and finer) accounts for about 15 wt%. wt% is the mass content of beryllium oxide ceramic powder in different particle size ranges to all beryllium oxide ceramic powders. Specifically, the D50 particle size of beryllium oxide ceramic powder A is 80 mesh, the D50 particle size of beryllium oxide ceramic powder B is 74 mesh, and the D50 particle size of beryllium oxide ceramic powder C is 110 mesh.

[0069] Among them, the manufacturer of beryllium oxide ceramic powders A, B, and C is the YWS-1, YWS-2, and YWS-3 models of beryllium oxide ceramic powders produced by Shanghai Feixing Special Ceramics Factory.

[0070] Example 1

[0071] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0072] The tubular heating device comprises a metal sleeve 1, a heating wire 2, a heat-conducting insulating material 3, and a ceramic rod 4.

[0073] The thermally conductive insulating material is made of the beryllium oxide ceramic powder A as described above, and its bulk density is 1.93 g / cm 3 , compacted density is 1.95 g / cm 3, which is 1% higher than the bulk density. Among them, the compaction density of the thermally conductive insulating material is tested by the water drainage method; specifically, an automatic powder filling machine (according to the industry standard, T / CEEIA 246-2016 Lead-acid battery plate coating equipment Part 2: Closed powder filling machine) is used to add beryllium oxide ceramic powder A to the tubular heating device, and the uniformity of the powder filling is ensured. After filling the powder, the tube is shrunk using an isostatic press, and the applied pressure does not exceed 500 MPa, and the pressure is maintained for 5 minutes. After completing the powder addition and tube shrinking, another section is cut off and the compaction density of the powder is tested by the water drainage method (JB / T 8508-1996 Electrical grade magnesium oxide Section 7.21 "Compaction density test method A water drainage method").

[0074] The metal sleeve 1 is a hollow tubular structure with sealed ends on both sides, and serves as a shell; the heating wire 2 is an alloy resistance wire, which is arranged inside the metal sleeve, and one end of the heating wire 2 is connected to the cold end, and the cold end is connected to a lead 5; the metal sleeve 1 and the heating wire 2 are densely filled with a heat-conducting insulating material 3, which is used to fix the heating element and plays the role of insulation and heat conduction; the heating element is formed by the heating wire 2 being wound around the ceramic rod 4 in a spiral spring type. The ceramic rod 4 (φ5 mm) plays the role of fixing the resistance wire position during the powder filling period.

[0075] In this embodiment, the metal sleeve is made of 600 type nickel alloy (inconel600 nickel-based alloy), with an outer diameter of 12 mm and a wall thickness of 1.5 mm; it surrounds a heating working area 6 and a non-heating working area 7, wherein the length of the heating working area is 2 m; the heating wire is a nickel-chromium alloy resistance wire, grade Cr20Ni80, a spiral spring structure, and a wire diameter of 1.5 mm (GB / T 1234-2012 High resistance electric heating alloy).

[0076] The rated voltage of the tubular heater is 380 V, the power frequency is 50 Hz, the rated power is 12 kW, the insulation withstand voltage is 2000V, the cold insulation resistance is ≥50 MΩ, and the cold leakage current is ≤0.5 mA.

[0077] Example 2

[0078] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0079] The thermally conductive insulating material is made of the beryllium oxide ceramic powder A as described above, and its bulk density is 1.93 g / cm 3 , compacted density is 2.12 g / cm 3 , the compacted density is 10% higher than the loose density.

[0080] Other conditions are the same as in Example 1.

[0081] Example 3

[0082] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0083] The thermally conductive insulating material is made of the beryllium oxide ceramic powder A as described above, and its bulk density is 1.93 g / cm 3 , compacted density is 2.41 g / cm 3 , the compacted density is 25% higher than the loose density.

[0084] Other conditions are the same as those in Example 1.

[0085] Example 4

[0086] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0087] The thermally conductive insulating material is made of the beryllium oxide ceramic powder A as described above, and its bulk density is 1.93 g / cm 3 , compacted density is 2.70 g / cm 3 , the compacted density is 40% higher than the loose density.

[0088] Other conditions are the same as those in Example 1.

[0089] Example 5

[0090] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0091] The thermally conductive insulating material is made of the beryllium oxide ceramic powder A as described above, and its bulk density is 1.93 g / cm 3 , compacted density is 1.83 g / cm 3 , the compacted density is 5% lower than the loose density.

[0092] Other conditions are the same as those in Example 1.

[0093] Example 6

[0094] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0095] The thermally conductive insulating material is made of the beryllium oxide ceramic powder B as described above, and its bulk density is 1.97 g / cm 3 , compacted density is 2.46 g / cm 3 , the compacted density is 25% higher than the loose density.

[0096] Other conditions are the same as those in Example 1.

[0097] Example 7

[0098] This embodiment also discloses a heat-conducting insulating material and a tubular heating device.

[0099] The thermally conductive insulating material is made of the beryllium oxide ceramic powder C as described above, and its bulk density is 1.88 g / cm 3 , compacted density is 2.35 g / cm 3 , the compacted density is 25% higher than the loose density.

[0100] Other conditions are the same as those in Example 1.

[0101] Comparative Example 1

[0102] This comparative example also discloses a heat-conducting insulating material and a tubular heating device.

[0103] The thermally conductive insulating material is made of the beryllium oxide ceramic powder A as described above, and its bulk density is 1.93 g / cm 3 , compacted density is 2.89 g / cm 3 , the compacted density is 50% higher than the loose density.

[0104] Other conditions are the same as those in Example 1.

[0105] Comparative Example 2

[0106] This comparative example also discloses a heat-conducting insulating material and a tubular heating device.

[0107] The thermally conductive insulating material is made of the high-temperature magnesium oxide powder as described above, and its bulk density is 2.31 g / cm 3 , compacted density is 2.89 g / cm 3 , the compacted density is 25% higher than the loose density.

[0108] Other conditions are the same as those in Example 1.

[0109] Effect Example 1

[0110] This effect embodiment verifies the working temperature and service life of the tubular heating device of the embodiment and the comparative example; the test conditions are as follows: the tested tubular heater is placed in a general indoor environment, without wind, at a temperature of 25 ± 5 ℃ and a relative humidity of 40 ± 20 %.

[0111] This effect embodiment tests the following performances of the tubular heating devices of the embodiment and the comparative example:

[0112] 1. Test temperature

[0113] Gradually adjust the working voltage of the tube heater and measure the surface temperature of the metal shell with an infrared thermometer. When the test temperature is reached, stop adjusting the voltage and keep it stable.

[0114] 2. Service life

[0115] The time taken for continuous testing to failure.

[0116] According to JB / T 12719-2016 "Accelerated Life Test Method for Daily Tubular Electric Heating Elements", tubular heaters are considered damaged if any of the following conditions occur:

[0117] (1) During the test, phenomena affecting safety, such as melting, flame spraying, and release of harmful gases, occur;

[0118] (2) The sample is damaged after the test.

[0119] (3) The hot leakage current value of the tubular heater is higher than 5 mA, or the hot insulation resistance is lower than 1 MΩ.

[0120] The test results obtained by the above test method are shown in Table 2. Table 2 shows the service life of the tubular heating devices of Examples 1-8 and Comparative Examples 1-2 at different test temperatures.

[0121] Table 2

[0122]

[0123] In the "Compacted Density" column in the table above, "±" represents the rate of increase or decrease in the compacted density of the material relative to the bulk density; for example, "+1%" means that the compacted density is increased by 1% relative to the bulk density; "-5%" means that the compacted density is decreased by 5% relative to the bulk density.

[0124] As shown in the table above, the test temperature of the tubular heating device of the present application can reach 850-1000°C, and its service life under this high temperature condition can be more than 50000h; for example, the compacted density of the thermal conductive material in Examples 1 and 5 is 1.95g / cm 3 and 1.83 g / cm 3 , the service life of the tubular heating device can still reach 57323h and 51497h; particularly preferably, the tubular heating device filled with the thermally conductive insulating material of Examples 2, 3, 6, and 7 can have a service life of more than 68000h at 850°C; and the service life of the tubular heating device of Example 3 at a test temperature of 1000°C can also reach 58432h.

[0125] Compared with the solution of the present application, the compaction density of the heat-conducting insulating material in the tubular heating device of Comparative Example 1 is too large, resulting in greater thermal stress, so that the service life of the device is relatively low, only 8079 hours.

[0126] For Comparative Example 2, the existing magnesium oxide powder is used as the thermally conductive insulating material in the tubular heating device. Its service life at 850°C is only 8842 hours, and it starts to smoke when the temperature rises to 956°C, and cannot work at 1000°C.

Claims

1. A thermally conductive insulating material, characterized in that: The compacted density of the thermally conductive insulating material is 1.70-2.70 g / cm 3 ; The thermally conductive insulating material comprises beryllium oxide ceramic powder with a particle size of 40-325 meshes.

2. The thermally conductive insulating material according to claim 1, characterized in that: The compacted density of the thermally conductive insulating material is 1.83-2.70 g / cm 3 , preferably 1.95-2.70 g / cm 3 , preferably 2.12-2.70 g / cm 3 , and more preferably 2.35-2.46 g / cm 3 .

3. The thermally conductive insulating material according to claim 1, characterized in that: The D50 particle size of the beryllium oxide ceramic powder is 60-200 meshes, preferably 60-140 meshes, and more preferably 70-110 meshes.

4. The thermally conductive insulating material according to claim 1, characterized in that: The mass content of the beryllium oxide ceramic powder with a particle size of 40-325 meshes in the thermal conductive insulating material is 90 wt%-99.99 wt%.

5. The thermally conductive insulating material according to claim 1, characterized in that: The thermally conductive insulating material meets one or more of the following conditions: ① The mass content of beryllium oxide ceramic powder with a particle size of 40-80 mesh in the thermal conductive insulating material is 40 wt%-60 wt%, preferably 40 wt%-58 wt%; ② The mass content of the beryllium oxide ceramic powder with a particle size of 80-200 mesh in the thermal conductive insulating material is 25 wt%-45 wt%, preferably 35 wt%-40 wt%; ③ The mass content of the beryllium oxide ceramic powder with a particle size of 200-325 mesh in the thermal conductive insulating material is 5 wt%-15wt%.

6. The thermally conductive insulating material according to claim 5, characterized in that: The thermally conductive insulating material meets one or more of the following conditions: ① The mass content of beryllium oxide ceramic powder with a particle size of 40-60 mesh in the thermal conductive insulating material is 20 wt%-30wt%; ② The mass content of beryllium oxide ceramic powder with a particle size of 60-80 mesh in the thermal conductive insulating material is 20 wt%-30wt%; ③ The mass content of beryllium oxide ceramic powder with a particle size of 80-140 mesh in the thermal conductive insulating material is 15 wt%-25wt%; ④ The mass content of beryllium oxide ceramic powder with a particle size of 140-200 mesh in the thermal conductive insulating material is 10 wt%-20wt%; ⑤ The mass content of the beryllium oxide ceramic powder with a particle size of 200-325 mesh in the thermally conductive insulating material is 5 wt%, 8 wt% or 15 wt%.

7. The thermally conductive insulating material according to claim 6, characterized in that: The thermally conductive insulating material meets one or more of the following conditions: ① The mass content of beryllium oxide ceramic powder with a particle size of 60-80 mesh in the thermal conductive insulating material is 20 wt%-28wt%; ② The mass content of beryllium oxide ceramic powder with a particle size of 80-140 mesh in the thermal conductive insulating material is 20 wt%-25wt%; ③ The mass content of the beryllium oxide ceramic powder with a particle size of 140-200 mesh in the thermal conductive insulating material is 10 wt%-18wt%.

8. The thermally conductive insulating material according to claim 6, characterized in that: The thermally conductive insulating material comprises 25wt% beryllium oxide ceramic powder with a particle size of 40-60 meshes, 25wt% beryllium oxide ceramic powder with a particle size of 60-80 meshes, 25wt% beryllium oxide ceramic powder with a particle size of 80-140 meshes, 15wt% beryllium oxide ceramic powder with a particle size of 140-200 meshes, and 8wt% beryllium oxide ceramic powder with a particle size of 200-325 meshes; Alternatively, the thermally conductive insulating material comprises 30wt% beryllium oxide ceramic powder with a particle size of 40-60 meshes, 28wt% beryllium oxide ceramic powder with a particle size of 60-80 meshes, 25wt% beryllium oxide ceramic powder with a particle size of 80-140 meshes, 10wt% beryllium oxide ceramic powder with a particle size of 140-200 meshes, and 5wt% beryllium oxide ceramic powder with a particle size of 200-325 meshes; Alternatively, the thermally conductive insulating material includes 20wt% beryllium oxide ceramic powder with a particle size of 40-60 meshes, 20wt% beryllium oxide ceramic powder with a particle size of 60-80 meshes, 20wt% beryllium oxide ceramic powder with a particle size of 80-140 meshes, 18wt% beryllium oxide ceramic powder with a particle size of 140-200 meshes, and 15wt% beryllium oxide ceramic powder with a particle size of 200-325 meshes.

9. A tubular heating device, characterized in that: The invention comprises a tubular heating device and the heat-conducting insulating material according to any one of claims 1 to 8, wherein the heat-conducting insulating material is filled in the tubular heating device.

10. Use of the thermally conductive insulating material according to any one of claims 1 to 8, or the tubular heating device according to claim 9 in a molten salt reactor or molten salt energy storage.

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