Process for preparing spherical electrically insulating magnesium oxide powder

Abstract

The application discloses a preparation method of spherical electrically-insulating magnesium oxide powder, which comprises the following steps: S1, crushing blocky magnesium oxide into magnesium oxide granules; S2, obtaining magnesium oxide granules by crushing the magnesium oxide granules through high-pressure airflow, and then classifying and removing the magnesium oxide granules through a classifier and a fan; S3, obtaining spherical magnesium oxide with a size of 0.03-0.425 mm by screening, magnetic separation and drying the magnesium oxide granules; S4, mixing the spherical magnesium oxide with high-temperature-resistant insulating fillers, stirring, and then mixing the spherical electrically-insulating magnesium oxide powder with organic silicon insulating materials, and screening to obtain the spherical electrically-insulating magnesium oxide powder. The high-pressure airflow crushing method is adopted, the magnesium oxide spheroidization step is simplified, the efficiency and spheroidization effect are improved, the classifier and the fan are used for dust removal, the particle size is uniform, and the purity is improved, and the prepared electrically-insulating magnesium oxide powder is improved in flowability, tap density and electrical insulation.

Description

Technical Field

[0001] This invention relates to the fields of materials science and electrical engineering, and in particular to a method for preparing spherical electrically insulating magnesium oxide powder. Background Technology

[0002] In the electrical industry, the selection of electrical insulation materials is crucial for ensuring the safe operation of equipment and improving overall performance. Magnesium oxide powder, as a high-performance insulating material, is widely used in the manufacture of electric heating elements, mineral-insulated cables, mineral-insulated heating cables, and special high-voltage electric heating elements due to its excellent electrical insulation properties and outstanding thermal conductivity. This type of material not only provides the necessary electrical isolation to prevent current leakage but also effectively transfers heat, ensuring the efficient and stable operation of the heating elements.

[0003] In the production process of electrically insulating magnesium oxide powder, the selection and processing of raw materials is one of the key steps. The quality of particle shape has a direct and significant impact on the performance of electrically insulating magnesium oxide powder. Irregularly shaped particles may lead to a decrease in filling density, affecting the uniformity and compactness of the insulation layer, thereby reducing electrical insulation performance. In addition, sharp edges and defects may increase friction and stress concentration between particles, making the insulation layer more prone to cracking and damage during long-term use, thus shortening the service life of heating elements.

[0004] To address the aforementioned issues and improve the performance of electrically insulating magnesium oxide powder, researchers began exploring the use of spherical magnesium oxide as a core raw material. Spherical particles possess higher packing density, more uniform particle size distribution, and better flowability, making them an ideal choice for preparing high-performance electrically insulating magnesium oxide powder.

[0005] However, conventional methods for preparing spherical magnesium oxide, such as crushing cubic magnesium oxide with a conventional jaw crusher and supplementing it with other shaping or grinding methods, often fail to produce spherical particles with regular shapes and smooth edges. Furthermore, the final product often still contains a large amount of dust, and the particle shape is irregular, which does not meet the stringent requirements for raw materials in high-performance electrical insulation materials. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention proposes a method for preparing spherical electrically insulating magnesium oxide powder, which can efficiently prepare spherical magnesium oxide with regular shape and smooth edges, and apply it to the production of electrically insulating magnesium oxide powder to improve the insulation performance and thermal conductivity of heating elements.

[0007] A method for preparing spherical electrically insulating magnesium oxide powder includes the following steps:

[0008] S1: Prepare magnesium oxide granules by crushing prismatic magnesium oxide granules into magnesium oxide granules.

[0009] S2: Prepare magnesium oxide granules. The magnesium oxide granules are pulverized by high-pressure airflow to obtain a material with a D75 content of 300-400μm. The material is then classified by a classifier and extracted by a high-speed blower to obtain magnesium oxide granules.

[0010] S3: To prepare spherical magnesium oxide, the magnesium oxide granules are sieved, magnetically separated, and dried to obtain spherical magnesium oxide with a size of 0.03 to 0.425 mm.

[0011] S4: Prepare spherical electrically insulating magnesium oxide powder. Mix the spherical magnesium oxide with high-temperature resistant insulating filler to obtain spherical electrically insulating magnesium oxide powder. Mix the spherical electrically insulating magnesium oxide powder with organosilicon insulating material and sieve to obtain spherical electrically insulating magnesium oxide powder.

[0012] Furthermore, the content of fine powder particles with a particle size of less than 20 μm in the magnesium oxide granules is less than 0.05%.

[0013] Furthermore, the particle size of the magnesium oxide granules is less than 3 mm.

[0014] Furthermore, the prismatic magnesium oxide is at least one of large-crystal fused magnesium oxide, fused magnesia, and high-purity magnesia.

[0015] Furthermore, the prismatic magnesium oxide has a particle size of 1–10 mm, a Leeb hardness of 5–7, and a magnesium content of 96–99.5%.

[0016] Furthermore, the mass ratio of the spherical magnesium oxide to the high-temperature resistant insulating filler is 100:0.5-3.

[0017] Furthermore, the high-temperature resistant insulating filler is made by calcining filler raw materials at high temperature. The composition of the filler raw materials is as follows: the mass ratio of aluminum magnesium spinel, zirconium oxide, silicon oxide and ferric oxide is 3-5:1-2:2-4:0.5-2.

[0018] Furthermore, the high-temperature calcination temperature is 600–800°C, and the duration is 40–90 minutes.

[0019] Furthermore, the mass ratio of the spherical electrical insulating magnesium oxide powder to the organosilicon insulating material is 50:0.001 to 0.04.

[0020] Furthermore, the composition of the organosilicon insulating material is as follows: the mass ratio of methyl silicone oil to silicone resin is 4 to 9:3.

[0021] In summary, the present invention has the following beneficial effects:

[0022] First, this invention uses high-pressure airflow to break up square-crystal magnesium oxide. The strong impact, collision, and frictional shearing caused by the high-speed airflow effectively achieves the breaking process. Simultaneously, this process naturally removes sharp edges, directly forming spherical magnesium oxide, thus improving production efficiency and spherical effect compared to existing spheroidizing methods.

[0023] Secondly, this invention employs a classifier and a blower to remove dust from the crushed magnesium oxide granules. The material is conveyed by airflow to the impeller classification zone, where coarse and fine particles are separated under centrifugal force and suction. Coarse particles are returned for further crushing, while fine particles enter a cyclone collector. This process ensures uniform particle size, while a bag filter removes dust, improving product purity.

[0024] Third, this technology utilizes airflow for crushing, grading, and dust removal throughout the entire process, eliminating the need for chemical reagents or complex physical treatments, thus offering environmental advantages. The highly efficient grading and dust removal equipment effectively controls dust emissions and purifies gas emissions, reducing environmental pollution. Furthermore, the optimized process reduces energy consumption, improves energy efficiency, and achieves green and energy-saving production.

[0025] Fourth, compared to electrically insulating magnesium oxide powder prepared by conventional methods, the product prepared by this invention exhibits the following significant advantages: its particle surface is smoother, and the powder flowability is significantly improved, with an increase of up to 10%. Furthermore, the product has a denser filling, with a tap density increase of over 5%; and its electrical insulation performance is improved by over 30%. Due to the significant improvement in the above-mentioned key performance indicators, this invention fully optimizes the various electrical performance indicators of the end products—electric heating elements and electric heating tubes—thereby comprehensively improving the overall quality of the end products. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart illustrating the operational steps of the method for preparing spherical electrical insulating magnesium oxide powder according to the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] A method for preparing spherical electrically insulating magnesium oxide powder, such as... Figure 1 As shown, it includes the following steps:

[0030] S1: Prepare magnesium oxide granules by crushing prismatic magnesium oxide granules into magnesium oxide granules.

[0031] S2: Prepare magnesium oxide granules. The magnesium oxide granules are pulverized by high-pressure airflow to obtain a material with a D75 content of 300-400μm. The material is then classified by a classifier and extracted by a high-speed blower to obtain magnesium oxide granules.

[0032] S3: To prepare spherical magnesium oxide, the magnesium oxide granules are sieved, magnetically separated, and dried to obtain spherical magnesium oxide with a size of 0.03 to 0.425 mm.

[0033] S4: Prepare spherical electrically insulating magnesium oxide powder. Mix the spherical magnesium oxide with high-temperature resistant insulating filler to obtain spherical electrically insulating magnesium oxide powder. Mix the spherical electrically insulating magnesium oxide powder with organosilicon insulating material and sieve to obtain spherical electrically insulating magnesium oxide powder.

[0034] This method employs high-pressure airflow to crush square-crystal magnesium oxide. During the crushing process, the high-speed airflow generates intense impacts, collisions, and frictional shearing between particles and between particles and the container wall, thereby refining the square-crystal magnesium oxide and removing the sharp edges and irregular shapes resulting from the crushing process, achieving sphericalization of the magnesium oxide material. Compared with the coarse crushing and hammering spheroidization steps in existing technologies, this method significantly improves production efficiency and enhances the spheroidization effect.

[0035] During the dust removal process, the pulverized granules are conveyed to the impeller classification zone by an upward airflow. Under the action of centrifugal force from the classification wheel and the suction force of the fan, coarse and fine particles are separated. Coarse particles return to the pulverizing chamber for further pulverization due to their own gravity, while qualified fine particles enter the cyclone collector with the airflow. Fine dust is collected by a bag filter, and the purified gas is discharged by an induced draft fan. This process not only ensures the uniformity of the product's particle size but also effectively removes impurities and improves the product's purity. This precise particle size classification and dust removal technology makes the final spherical magnesium oxide product more suitable for application requirements.

[0036] Furthermore, the crushing method in step S1 is jaw crushing.

[0037] This solution optimizes the crushing method for prismatic magnesium oxide, which is characterized by its high hardness. Due to its high hardness, conventional crushing equipment struggles to effectively break down prismatic magnesium oxide, often resulting in uneven fragments and excessive dust generation. The jaw crusher, however, utilizes jaw plates made of high-strength alloy materials, effectively handling high-hardness prismatic magnesium oxide blocks. Its large crushing ratio allows for rapid crushing to the required particle size. Furthermore, the absence of dead zones in the crushing chamber results in high feeding capacity and output, thereby improving production efficiency.

[0038] Furthermore, the content of fine powder particles with a particle size of less than 20 μm in the magnesium oxide granules is less than 0.05%.

[0039] This scheme further limits the content of dust (fine powder particles with a particle size of less than 20μm) in magnesium oxide granules, ensuring the purity and uniformity of magnesium oxide granules.

[0040] Furthermore, the particle size of the magnesium oxide granules is less than 3 mm.

[0041] This solution optimizes the particle size of magnesium oxide granules to ensure a suitable feed particle size during high-pressure airflow milling, thereby avoiding problems such as low crushing efficiency, excessive crushing time, and excessive equipment load. Simultaneously, this solution effectively ensures that the crushed material meets the requirement of a D75 content between 300 and 400 micrometers.

[0042] Furthermore, the prismatic magnesium oxide is at least one of large-crystal fused magnesium oxide, fused magnesia, and high-purity magnesia.

[0043] Furthermore, the prismatic magnesium oxide has a particle size of 1–10 mm, a Leeb hardness of 5–7, and a magnesium content of 96–99.5%.

[0044] This solution optimizes the use of prismatic magnesia raw materials and their physicochemical properties. The individual or combined use of large-crystal fused magnesia, fused magnesia sand, and high-purity magnesia sand significantly improves the purity and uniformity of particle size distribution in spherical magnesia products, enhancing chemical and thermal stability, mechanical strength, and corrosion resistance. High-purity raw materials reduce impurities, while spherical magnesia improves insulation performance; uniform particle size and moderate hardness promote the formation of spherical magnesia particles, optimizing flowability and distribution.

[0045] Furthermore, the mass ratio of the spherical magnesium oxide to the high-temperature resistant insulating filler is 100:0.5-3.

[0046] Furthermore, the high-temperature resistant insulating filler is made by calcining filler raw materials at high temperature. The composition of the filler raw materials is as follows: the mass ratio of aluminum magnesium spinel, zirconium oxide, silicon oxide and ferric oxide is 3-5:1-2:2-4:0.5-2.

[0047] Furthermore, the high-temperature calcination temperature is 600–800°C, and the duration is 40–90 minutes.

[0048] This scheme optimizes the selection, proportioning, and high-temperature calcination conditions of high-temperature insulating materials, significantly improving the material's high-temperature resistance and insulation performance. The introduction of aluminum-magnesium spinel enhances the material's thermal stability and chemical inertness, while the rational proportions of zirconium oxide, silicon oxide, and ferric oxide further optimize the microstructure and properties of the filler. High-temperature calcination not only removes impurities from the material but also promotes the crystal phase transformation of the filler, thereby improving its high-temperature resistance and insulation performance.

[0049] Meanwhile, the mass ratio of spherical magnesium oxide to high-temperature resistant insulating filler was optimized. Compared with electrically insulating magnesium oxide powder prepared by conventional methods, the spherical electrically insulating magnesium oxide powder product prepared by the present invention has an electrical insulation performance that is improved by more than 20%.

[0050] Furthermore, the mass ratio of the spherical electrical insulating magnesium oxide powder to the organosilicon insulating material is 50:0.001 to 0.04.

[0051] Furthermore, the composition of the organosilicon insulating material is as follows: the mass ratio of methyl silicone oil to silicone resin is 4 to 9:3.

[0052] The optimized organosilicon insulating material and formulation significantly improve the processing performance and mechanical strength of spherical electrically insulating magnesium oxide powder. Methyl silicone oil, with its excellent lubricity and dispersibility, reduces material viscosity and improves processing efficiency. The introduction of silicone resin enhances the material's toughness and mechanical strength, enabling it to withstand greater external forces without easily breaking. This optimized formulation not only improves the processing performance and mechanical strength of spherical electrically insulating magnesium oxide powder but also ensures the formation of a denser and more uniform insulating layer during the filling process, thereby improving the overall electrical insulation performance and reliability of the material.

[0053] Meanwhile, the mass ratio of spherical electrical insulating magnesium oxide powder to organosilicon insulating material was optimized. Compared with the electrical insulating magnesium oxide powder prepared by conventional methods, the spherical electrical insulating magnesium oxide powder product prepared by the present invention has a smoother particle surface, a 10% increase in powder flowability, and a denser filling, with a 5% increase in tap density.

[0054] Example 1

[0055] Preparation of spherical electrically insulating magnesium oxide powder:

[0056] S1: Preparation of magnesium oxide granules:

[0057] Large crystalline fused magnesium oxide with a Leeb hardness of 5-7, a magnesium content of 96-99.5%, and a particle size of 1-10 mm is crushed into magnesium oxide granules with a particle size of less than 3 mm using a jaw crusher.

[0058] S2: Preparation of magnesium oxide granules:

[0059] The magnesium oxide granules are fed into a high-pressure air jet mill at a feed rate of 5-10 kg / min to crush and remove sharp edges and spheroidize, resulting in a material with a D75 content of 300-400 μm. The material is then classified by a classifier and extracted by a high-speed fan. The dust in the material is removed by utilizing the centrifugal force of the classifier wheel and the high-speed extraction principle of the fan. The dust consists of fine powder particles with a particle size of less than 20 μm and a content of less than 0.05%. The resulting magnesium oxide granules are free of visible dust when lifted.

[0060] S3: Preparation of spherical magnesium oxide A:

[0061] The magnesium oxide granules are screened, magnetically separated, and dried to obtain 0.03-0.425 mm spherical magnesium oxide A.

[0062] S4: Preparation of spherical electrically insulating magnesium oxide powder:

[0063] Aluminum magnesium spinel, zirconium oxide, silicon oxide, and ferric oxide were mixed at a mass ratio of 4:1:4:1 and then calcined at 700℃ for 60 minutes. After sieving, a high-temperature resistant insulating filler was obtained. Spherical magnesium oxide A was mixed with the high-temperature resistant insulating filler at a mass ratio of 100:2 and stirred for 20 minutes to obtain spherical electrical insulating magnesium oxide powder.

[0064] Organosilicon insulating material is prepared by mixing methyl silicone oil and silicone resin at a mass ratio of 2:1. The spherical electrical insulating magnesium oxide powder is mixed with the organosilicon insulating material at a mass ratio of 50:0.02 and sieved to obtain spherical electrical insulating magnesium oxide powder.

[0065] Example 2

[0066] Preparation of spherical electrically insulating magnesium oxide powder:

[0067] S1: Preparation of magnesium oxide granules:

[0068] Fused magnesia with a Leeb hardness of 5-7, a magnesium content of 96-99.5%, and a particle size of 1-10 mm is crushed into magnesium oxide granules with a particle size of less than 3 mm using a jaw crusher.

[0069] S2: Preparation of magnesium oxide granules:

[0070] The magnesium oxide granules are fed into a high-pressure air jet mill at a feed rate of 5-10 kg / min to crush and remove sharp edges and spheroidize, resulting in a material with a D75 content of 300-400 μm. The material is then classified by a classifier and extracted by a high-speed fan. The dust in the material is removed by utilizing the centrifugal force of the classifier wheel and the high-speed extraction principle of the fan. The dust consists of fine powder particles with a particle size of less than 20 μm and a content of less than 0.05%. The resulting magnesium oxide granules are free of visible dust when lifted.

[0071] S3: Preparation of spherical magnesium oxide B:

[0072] The magnesium oxide granules are screened, magnetically separated, and dried to obtain 0.03-0.425 mm spherical magnesium oxide B.

[0073] S4: Preparation of spherical electrically insulating magnesium oxide powder:

[0074] Aluminum magnesium spinel, zirconium oxide, silicon oxide, and ferric oxide were mixed at a mass ratio of 3:2:3:2 and then calcined at 600℃ for 40 minutes. After sieving, a high-temperature resistant insulating filler was obtained. Spherical magnesium oxide B was mixed with the high-temperature resistant insulating filler at a mass ratio of 100:0.5 and stirred for 10 minutes to obtain spherical electrical insulating magnesium oxide powder.

[0075] Organosilicon insulating material is prepared by mixing methyl silicone oil and silicone resin at a mass ratio of 3:1. The spherical electrical insulating magnesium oxide powder is mixed with the organosilicon insulating material at a mass ratio of 50:0.001 and sieved to obtain spherical electrical insulating magnesium oxide powder.

[0076] Example 3

[0077] Preparation of spherical electrically insulating magnesium oxide powder:

[0078] S1: Preparation of magnesium oxide granules:

[0079] High-purity magnesia with a Leeb hardness of 5-7, a magnesium content of 96-99.5%, and a particle size of 1-10 mm is crushed into magnesium oxide granules with a particle size of less than 3 mm using a jaw crusher.

[0080] S2: Preparation of magnesium oxide granules:

[0081] The magnesium oxide granules are fed into a high-pressure air jet mill at a feed rate of 5-10 kg / min to crush and remove sharp edges and spheroidize, resulting in a material with a D75 content of 300-400 μm. The material is then classified by a classifier and extracted by a high-speed fan. The dust in the material is removed by utilizing the centrifugal force of the classifier wheel and the high-speed extraction principle of the fan. The dust consists of fine powder particles with a particle size of less than 20 μm and a content of less than 0.05%. The resulting magnesium oxide granules are free of visible dust when lifted.

[0082] S3: Preparation of spherical magnesium oxide C:

[0083] The magnesium oxide granules are screened, magnetically separated, and dried to obtain spherical magnesium oxide C with a diameter of 0.03-0.425 mm.

[0084] S4: Preparation of spherical electrically insulating magnesium oxide powder:

[0085] Aluminum-magnesium spinel, zirconium oxide, silicon oxide, and ferric oxide were mixed at a mass ratio of 5:2:2.5:0.5 and then calcined at 800℃ for 90 minutes. After sieving, a high-temperature resistant insulating filler was obtained. Spherical magnesium oxide C was mixed with the high-temperature resistant insulating filler at a mass ratio of 100:3 and stirred for 30 minutes to obtain spherical electrical insulating magnesium oxide powder.

[0086] Organosilicon insulating material is prepared by mixing methyl silicone oil and silicone resin at a mass ratio of 4:3. The spherical electrical insulating magnesium oxide powder is then mixed with the organosilicon insulating material at a mass ratio of 50:0.04 and sieved to obtain spherical electrical insulating magnesium oxide powder.

[0087] Comparative Example 1

[0088] Spherical electrically insulating magnesium oxide powder was prepared using spherical magnesium oxide prepared by conventional methods as raw material.

[0089] S1: Preparation of magnesium oxide granules:

[0090] Large crystalline fused magnesium oxide with a Leeb hardness of 5-7, a magnesium content of 96-99.5%, and a particle size of 1-10 mm is crushed into magnesium oxide granules with a particle size of less than 3 mm using a jaw crusher.

[0091] S2: Preparation of spherical magnesium oxide D:

[0092] The magnesium oxide granules were ground, hammered, sieved, magnetically separated, and dried to obtain 0.425mm spherical magnesium oxide D.

[0093] S4: Preparation of spherical electrically insulating magnesium oxide powder:

[0094] Aluminum magnesium spinel, zirconium oxide, silicon oxide, and ferric oxide were mixed at a mass ratio of 4:1:4:1 and then calcined at 700℃ for 60 minutes. After sieving, a high-temperature resistant insulating filler was obtained. Spherical magnesium oxide D was mixed with the high-temperature resistant insulating filler at a mass ratio of 100:2 and stirred for 20 minutes to obtain spherical electrical insulating magnesium oxide powder.

[0095] Organosilicon insulating material is prepared by mixing methyl silicone oil and silicone resin at a mass ratio of 2:1. The spherical electrical insulating magnesium oxide powder is mixed with the organosilicon insulating material at a mass ratio of 50:0.02 and sieved to obtain spherical electrical insulating magnesium oxide powder.

[0096] Comparative Example 2

[0097] Unlike Example 1, the spherical magnesium oxide used in step S4 is a mixture of spherical magnesium oxide A prepared in Example 1 and spherical magnesium oxide D prepared in Comparative Example 1, with a mass ratio of 3:7.

[0098] Comparative Example 3

[0099] Unlike Example 1, the spherical magnesium oxide used in step S4 is a mixture of spherical magnesium oxide A prepared in Example 1 and spherical magnesium oxide D prepared in Comparative Example 1, with a mass ratio of 6:4.

[0100] The main implementation conditions for each embodiment and comparative example are shown in Table 1:

[0101] Table 1. Summary of test conditions for each embodiment and comparative example.

[0102]

[0103] Experimental Results and Analysis

[0104] This invention details the technical solutions proposed in Examples 1 to 3, and provides comparative examples to verify the performance of the spherical electrical insulating magnesium oxide powder prepared in the examples and comparative examples, as shown in Table 2:

[0105] Table 2 Comparison of the performance of spherical electrical insulating magnesium oxide powder prepared in each embodiment and comparative example.

[0106] sample <![CDATA[3 # Flow rate (s / 100g) <![CDATA[Tap density (g / cm 3 )]]> Hot withstand voltage (kV) Hot insulation resistance (MΩ) Example 1 155 2.51 2.6 10.0 Example 2 156 2.49 2.5 10.0 Example 3 155 2.50 2.6 9.0 Comparative Example 1 170 2.38 2.0 1.5 Comparative Example 2 165 2.42 2.2 2.5 Comparative Example 3 162 2.45 2.4 4.0

[0107] During the implementation of the examples and comparative examples, the morphological characteristics of the spherical magnesium oxides prepared in Examples 1 to 3 and Comparative Example 1 were examined. From a visual perspective, there is a significant difference between these samples: the spherical magnesium oxides prepared in Examples 1 to 3 have smooth and rounded surfaces, and no visible dust or particles are observed when the samples are lifted with a tool; in contrast, the spherical magnesium oxides prepared in Comparative Example 1 exhibit obvious dust and ash dispersion under the same operation.

[0108] Furthermore, in the preparation of electrically insulating grade spherical magnesium oxide in Comparative Examples 2 and 3, a mixture of spherical magnesium oxide A prepared in Example 1 and spherical magnesium oxide D prepared in Comparative Example 1 was used as the raw material for spherical magnesium oxide. After thorough mixing, as the proportion of spherical magnesium oxide A in the mixture increased, the amount of dust generated when the mixture was stirred up was significantly reduced. Specifically, the dust dispersion phenomenon in Comparative Example 2 was reduced, with only a small amount of dust suspended; while in Comparative Example 3, the dust dispersion was reduced to a barely visible level.

[0109] In terms of liquidity testing, the experiment adopted a 3... # The flow rate of 100g of electrically insulating magnesium oxide powder was measured using a Ford cup. The test was conducted from the moment the sample was poured into the Ford cup until the entire sample had passed through the orifice. According to the test data in Table 2: for the same weight of sample, the electrically insulating magnesium oxide powder prepared using the conventional method in Comparative Example 1 flowed entirely out of the Ford cup within 170s. In contrast, the time taken for the electrically insulating magnesium oxide powder prepared in Examples 1 to 3 was shortened to approximately 155–156s, demonstrating improved flowability. Furthermore, comparing the data from the examples and the comparative examples reveals that as the amount of spherical magnesium oxide A incorporated into the magnesium oxide raw material increases, the flowability of the prepared electrically insulating magnesium oxide powder shows a continuously increasing trend.

[0110] Regarding tap density, based on the data analysis in Table 2, the average tap density of the electrically insulating magnesium oxide powder prepared in Examples 1 to 3 reached 2.50 g / cm³. 3 It is noteworthy that, with all other experimental conditions kept constant, in the tests of Comparative Examples 1, 2, 3, and Example 1, the proportion of spherical magnesium oxide raw material A in the spherical magnesium oxide raw material gradually increased from 0% to 100%. With this increase in proportion, the tap density data showed a clear increasing trend, from 2.38 g / cm³. 3 Gradually increased to approximately 2.50 g / cm³ 3 This is because the spherical magnesium oxide product prepared using Example 1 of the present invention has improved performance compared to conventional methods. The electrically insulating magnesium oxide powder prepared using it as a raw material has a denser filling, thereby increasing the tap density.

[0111] Regarding the crucial electrical insulation performance of the electrically insulating magnesium oxide powder, the experiment investigated its hot-state withstand voltage and hot-state insulation performance at a high temperature of 700℃. According to the data in Table 2, as the proportion of spherical magnesium oxide A in the spherical magnesium oxide raw material continuously increased, the electrical insulation performance of the electrically insulating magnesium oxide powder also showed a significant improvement trend. Specifically, under the test condition of 0.5 mA·2s, the hot-state withstand voltage of the sample increased from 2.0 kV to 2.5–2.6 kV; simultaneously, the hot-state insulation resistance of the sample also jumped significantly from 1.5 MΩ to 10 MΩ. Compared with Comparative Example 1, the electrically insulating magnesium oxide powder prepared in Example 1 achieved significant improvements in both hot-state withstand voltage and hot-state insulation performance, which is attributed to the improved performance of the spherical magnesium oxide prepared in Example 1 compared to conventional methods.

[0112] In summary, the spherical electrically insulating magnesium oxide powder obtained by this invention, compared with ordinary electrically insulating magnesium oxide powder, has a smoother particle surface, improved powder flowability by 10%, denser filling, and a tap density increase of over 5%; and improved electrical insulation performance by over 30%. Due to these improvements in performance indicators, the various electrical performance indicators of the electric heating elements and heating tubes in the end products are significantly improved, thereby improving the overall quality of the end products and playing a vital role in enhancing the reliability and safety of electrical equipment.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing spherical electrically insulating magnesium oxide powder, characterized in that, Includes the following steps: S1: Prepare magnesium oxide granules by crushing prismatic magnesium oxide granules into magnesium oxide granules. S2: Preparation of magnesium oxide granules: The magnesium oxide granules are pulverized by high-pressure airflow to obtain a material with a D75 content of 300~400 μm. The material is then classified by a classifier and extracted by a high-speed blower to obtain magnesium oxide granules. The content of fine powder particles with a particle size of less than 20 μm in the magnesium oxide granules is less than 0.05%. S3: To prepare spherical magnesium oxide, the magnesium oxide granules are sieved, magnetically separated, and dried to obtain spherical magnesium oxide with a size of 0.03~0.425mm; S4: Prepare spherical electrically insulating magnesium oxide powder. Mix the spherical magnesium oxide with high-temperature resistant insulating filler to obtain spherical electrically insulating magnesium oxide powder. The mass ratio of the spherical magnesium oxide to the high-temperature resistant insulating filler is 100:0.5~3. The high-temperature resistant insulating filler is made by calcining filler raw materials at high temperature. The composition of the filler raw materials is as follows: aluminum magnesium spinel, zirconium oxide, silicon oxide, and ferric oxide. Mix the spherical electrically insulating magnesium oxide powder with organosilicon insulating material and sieve to obtain spherical electrically insulating magnesium oxide powder.

2. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The particle size of the magnesium oxide granules is less than 3 mm.

3. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The prismatic magnesium oxide is at least one of large-crystal fused magnesium oxide, fused magnesia, and high-purity magnesia.

4. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The prismatic magnesium oxide has a particle size of 1-10 mm, a Leeb hardness of 5-7, and a magnesium content of 96-99.5%.

5. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The mass ratio of aluminum magnesium spinel, zirconium oxide, silicon oxide, and ferric oxide in the filler raw material is 3~5:1~2:2~4:0.5~2.

6. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The high-temperature calcination temperature is 600~800℃, and the duration is 40~90 min.

7. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The mass ratio of the spherical electrical insulating magnesium oxide powder to the organosilicon insulating material is 50:0.001~0.

04.

8. The method for preparing spherical electrically insulating magnesium oxide powder according to claim 1, characterized in that, The composition of the organosilicon insulating material is as follows: the mass ratio of methyl silicone oil to silicone resin is 4~9:3.

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