A mineral magnesium oxide insulated fireproof cable and its preparation method

Abstract

This invention relates to the field of cable technology, specifically to a mineral magnesium oxide insulated fire-resistant cable and its preparation method, comprising the following components: modified magnesium oxide, modified LDHs, and borate glass powder. During the high-temperature activation stage of cable preparation, the borate glass powder softens and flows in situ, filling the pores and microcracks between MgO particles. After cooling, it forms a dense glassy sealing layer with excellent electrical insulation properties, preventing H2S from penetrating into the insulation layer. When a small amount of H2S penetrates, the layered structure of the modified LDHs physically adsorbs the residual H2S. Simultaneously, zinc oxide in the modified magnesium oxide captures H2S to form zinc sulfide, which is then complexed with chitosan to form a mobile state. The sodium carboxymethyl cellulose (SMC) in the modified LDHs also contributes to this process. ‑ Chitosan-NH3 with modified magnesium oxide + Electrostatic adsorption is formed, and zinc sulfide is received and transferred. Manganese dioxide catalyzes the oxidation of zinc sulfide to zinc sulfate.

Description

Technical Field

[0001] This invention belongs to the field of cable technology, specifically a mineral magnesium oxide insulated fireproof cable and its preparation method. Background Technology

[0002] In industrial sectors such as petroleum refining, chemical production, and natural gas processing, pipeline-transported media (such as crude oil, heavy oil, chemical raw materials, and sulfur-containing natural gas) often contain sulfides such as hydrogen sulfide (H2S), mercaptans (RSH), and disulfides (RSSR). These media are prone to solidification at room temperature and must be electrically heated to ensure their fluidity. Mineral-insulated (MI) heating cables, due to their entirely inorganic structure, high-temperature resistance, and excellent fire resistance, have become an ideal choice for this field.

[0003] However, when traditional MI cables are operated for a long time in a sulfur-containing environment, if there is a slight leak in the pipeline medium or under high temperature conditions, sulfur vapors such as hydrogen sulfide can penetrate into the cable through the micropores or welds of the oxygen-free copper pipe. Magnesium oxide and hydrogen sulfide will react chemically to form MgS, which will cause the insulation resistance to drop sharply. In severe cases, it may cause leakage accidents, posing a major safety hazard in explosion-proof areas. Summary of the Invention

[0004] (1) Technical problems to be solved The purpose of this invention is to provide a mineral magnesium oxide insulated fireproof cable and its preparation method, so as to solve the problem that the insulation resistance of magnesium oxide cables decreases due to the reaction of magnesium oxide with hydrogen sulfide in a sulfur-containing environment.

[0005] (2) Technical solution To achieve the above objectives, on the one hand, the present invention provides a mineral magnesium oxide insulated fireproof cable, which comprises, from the inside out, a nickel-chromium alloy heating core, an insulating powder layer, and an oxygen-free copper tube; The insulating layer powder comprises the following components by weight fraction: 40-45 parts modified magnesium oxide, 35-40 parts modified LDHs, and 55-60 parts borate glass powder; The modified magnesium oxide is zinc oxide-modified magnesium oxide grafted with chitosan; The modified LDHs were modified with sodium carboxymethyl cellulose-MnO2; The borate glass powder includes SiO2, B2O3, Bi2O3, Na2O, CaO, and Al2O3, and has a glass transition temperature of 290~320℃.

[0006] Furthermore, the preparation method of the modified magnesium oxide includes the following steps: S11. Disperse magnesium oxide powder ultrasonically in deionized water to obtain magnesium oxide slurry; dissolve Zn(CH3COO)2·2H2O in deionized water with stirring, slowly add it dropwise to magnesium oxide slurry, adjust the pH with ammonia water, stir the reaction, filter the resulting reaction solution to collect the solid, wash with deionized water, dry in an oven, and calcine in a tube furnace to obtain ZnO@MgO composite powder; S12. Chitosan was dissolved in acetic acid solution by stirring, ZnO@MgO composite powder was added, ultrasonically dispersed, glutaraldehyde solution was added, pH was adjusted, and the reaction was heated. The resulting reaction solution was filtered to collect the solid, washed with deionized water and anhydrous ethanol, vacuum dried, ground and sieved to obtain modified magnesium oxide.

[0007] Furthermore, the preparation method of the modified LDHs includes the following steps: S21. Dissolve Mg(NO3)2·6H2O and Al(NO3)3·9H2O in deionized water to obtain a salt solution; dissolve NaOH and Na2CO3 in deionized water to obtain an alkaline solution; while stirring, slowly add the salt solution and alkaline solution dropwise to deionized water simultaneously, stir and age, let stand to precipitate, collect the solid by vacuum filtration, wash with deionized water, transfer to a high-pressure reactor, hydrothermally crystallize, cool and remove, wash and filter, vacuum dry to obtain LDHs powder; S22. Dissolve KMnO4 in deionized water to obtain potassium permanganate solution; ultrasonically disperse LDHs powder in deionized water, slowly add potassium permanganate solution, transfer to high pressure reactor, hydrothermal reaction, cool and remove, centrifuge, wash with deionized water, vacuum dry to obtain LDHs-MnO2; S23. Dissolve sodium carboxymethyl cellulose in deionized water to obtain a sodium carboxymethyl cellulose solution; disperse LDHs-MnO2 in deionized water, slowly add the sodium carboxymethyl cellulose solution, sonicate, stir to react, and spray dry to obtain modified LDHs.

[0008] Furthermore, the method for preparing the borate glass powder includes: mixing SiO2, B2O3, Bi2O3, Na2CO3, CaCO3 and Al2O3, ball milling, placing the mixed powder in a corundum crucible, heating and melting it in a high-temperature furnace, pouring the resulting molten glass liquid into cold water for rapid cooling, drying the resulting glass block, ball milling, and sieving to obtain borate glass powder.

[0009] Furthermore, the raw materials for preparing the borate glass powder include the following components by weight fraction: 20-25 parts SiO2, 35-40 parts B2O3, 25-30 parts Bi2O3, 4-6 parts Na2CO3, 5-7 parts CaCO3, and 1-2 parts Al2O3.

[0010] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing a mineral magnesium oxide insulated fireproof cable, applicable to the aforementioned mineral magnesium oxide insulated fireproof cable, comprising the following steps: S1. Mix modified magnesium oxide, modified LDHs and borate glass powder, add anhydrous ethanol and sodium hexametaphosphate, ball mill and mix, dry and sieve to obtain insulating layer powder; S2. Place the nickel-chromium alloy heating core in the center of the oxygen-free copper tube, slowly pour in the insulating powder, vacuum vibrate and compact it, and use multi-pass drawing and diameter reduction molding. S3. The drawn cable is placed in a tube furnace for high-temperature activation treatment, cooled to room temperature, and sealed at both ends by argon arc welding to obtain the cable.

[0011] Furthermore, the multi-pass drawing process involves a total of 8 passes, resulting in a final product with an outer diameter of Φ6.5mm and an insulation layer thickness of 1.8mm. The drawing process generates axial compressive stress, causing the powder compaction density to reach 2.5~3.0g / cm³. 3 .

[0012] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. During the high-temperature activation stage of cable preparation, borate glass powder softens and flows in situ, filling the pores and microcracks between MgO particles. After cooling, it forms a dense glassy sealing layer. This glass layer has extremely high chemical stability, does not react with H2S, has excellent electrical insulation properties, and prevents H2S from penetrating into the insulation layer.

[0013] 2. The borate glass sealing layer serves as the primary protection. When a small amount of H2S permeates, the modified LDHs act as a buffer layer. Their layered structure physically adsorbs residual H2S. Simultaneously, the zinc oxide in the modified magnesium oxide captures H2S to form zinc sulfide. Chitosan complexes the zinc sulfide to form a mobile state. The -COO group of the modified LDHs' sodium carboxymethyl cellulose... - Chitosan-NH3 with modified magnesium oxide + Electrostatic adsorption is formed, and ZnS is received and transferred. Manganese dioxide catalyzes the oxidation of zinc sulfide into zinc sulfate, which has good electrical insulation properties, is stable under high heat, and is non-corrosive to MgO. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the manufacturing process of the cable of the present invention; Figure 2 This is a physical image of the modified magnesium oxide of this invention. Detailed Implementation

[0015] 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, and 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.

[0016] Example 1: This example discloses a mineral magnesium oxide insulated fireproof cable, which includes, from the inside out, a nickel-chromium alloy heating core, an insulating powder layer, and an oxygen-free copper tube; The insulating layer powder comprises the following components by weight fraction: 42 parts modified magnesium oxide, 38 parts modified LDHs, and 57 parts borate glass powder; The modified magnesium oxide is zinc oxide-modified magnesium oxide grafted with chitosan; The modified LDHs were modified with sodium carboxymethyl cellulose-MnO2; The borate glass powder includes SiO2, B2O3, Bi2O3, Na2O, CaO, and Al2O3, and has a glass transition temperature of 290~320℃.

[0017] The method for preparing the modified magnesium oxide includes the following steps: S11. 100g of magnesium oxide powder was ultrasonically dispersed in 500mL of deionized water to obtain magnesium oxide slurry; 24.2g of Zn(CH3COO)2·2H2O was dissolved in 200mL of deionized water and slowly added dropwise to the magnesium oxide slurry. The pH was adjusted to 8-8.5 with ammonia water, and the reaction was stirred at 60℃ for 4h. The resulting reaction solution was filtered to collect the solid, washed with deionized water, dried in an oven at 80℃ for 12h, and calcined in a tube furnace under a nitrogen protective atmosphere at a rate of 5℃ / min to 400℃ and held for 2h to obtain ZnO@MgO composite powder. S12. Dissolve 8.5g of chitosan in 500mL of 2% acetic acid solution, add 100g of ZnO@MgO composite powder, ultrasonically disperse for 30min, add 8mL of glutaraldehyde solution, adjust pH to 5.5, heat to 50℃ and react for 6h, filter the reaction solution to collect the solid, wash with deionized water and anhydrous ethanol, vacuum dry at 80℃ for 24h, grind through a 200-mesh sieve to obtain modified magnesium oxide.

[0018] It should be noted that, as Figure 2 The image shown is a physical diagram of the modified magnesium oxide of the present invention. It is prepared by blending it with modified LDHs and borate glass powder to obtain insulating layer powder.

[0019] The preparation method of the modified LDHs includes the following steps: S21. Dissolve 30.8g Mg(NO3)2·6H2O and 11.3g Al(NO3)3·9H2O in 300mL deionized water to obtain a salt solution; dissolve 24g NaOH and 15.9g Na2CO3 in 300mL deionized water to obtain an alkaline solution; under stirring, slowly add the salt solution and alkaline solution dropwise to 100mL deionized water simultaneously, stir and age for 2h, let stand to precipitate, filter and collect the solid, wash with deionized water, transfer to a high-pressure reactor, hydrothermally crystallize at 100℃ for 12h, cool and remove, wash and filter, vacuum dry at 60℃ for 24h to obtain LDHs powder; S22. Dissolve 3.16g KMnO4 in 100mL deionized water to obtain potassium permanganate solution; ultrasonically disperse 10g LDHs powder in 200mL deionized water, slowly add potassium permanganate solution, transfer to high pressure reactor, hydrothermally react at 120℃ for 6h, cool, remove, centrifuge, wash with deionized water, vacuum dry at 60℃ for 24h to obtain LDHs-MnO2; S23. Dissolve 1.2g of sodium carboxymethyl cellulose in 100mL of deionized water to obtain a sodium carboxymethyl cellulose solution; disperse 10g of LDHs-MnO2 in 200mL of deionized water, slowly add the sodium carboxymethyl cellulose solution, sonicate for 30min, stir and react at room temperature for 6h, and spray dry at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain modified LDHs.

[0020] The method for preparing the borate glass powder includes: mixing SiO2, B2O3, Bi2O3, Na2CO3, CaCO3 and Al2O3, ball milling, placing the mixed powder in a corundum crucible, heating it to 1100~1250℃ in a high-temperature furnace at 10℃ / min, holding it at that temperature for 2~3 hours to fully melt it, stirring 2~3 times during the process to ensure uniformity, pouring the resulting molten glass liquid into cold water for rapid cooling, drying the resulting glass block, ball milling, and sieving to obtain borate glass powder.

[0021] The raw materials for preparing the borate glass powder include the following components by weight fraction: 25 parts SiO2, 40 parts B2O3, 30 parts Bi2O3, 6 parts Na2CO3, 7 parts CaCO3, and 2 parts Al2O3.

[0022] The method for preparing a mineral magnesium oxide insulated fireproof cable includes the following steps: S1. Modified magnesium oxide, modified LDHs and borate glass powder are mixed, anhydrous ethanol and sodium hexametaphosphate are added, and the mixture is ball-milled for 4 hours. After drying and sieving, insulating layer powder is obtained. S2. Place the nickel-chromium alloy heating core in the center of the oxygen-free copper tube, slowly pour in the insulating powder, vacuum vibrate and compact it, and use multi-pass drawing and diameter reduction molding. S3. Place the drawn cable in a tube furnace, introduce high-purity nitrogen (flow rate 200 mL / min), heat to 300℃ at 5℃ / min, hold for 2 hours, cool to room temperature, and seal both ends with argon arc welding to obtain the cable.

[0023] The multi-pass drawing process consists of 8 passes, resulting in a final product with an outer diameter of Φ6.5mm and an insulation layer thickness of 1.8mm. The drawing process generates axial compressive stress, causing the powder to achieve a compaction density of 2.5~3.0g / cm³. 3 .

[0024] It should be noted that, as Figure 1 The diagram shows the preparation process of the cable of the present invention. High-temperature activation is a key step of the present invention. The drawn cable is placed in a tube furnace, high-purity nitrogen is introduced, and the temperature is raised to 300°C at 5°C / min. The temperature is held for 2 hours for high-temperature activation. During this process, the borate glass phase reaches the softening temperature and flows to fill the pores and microcracks between magnesium oxide particles, forming a dense glassy sealing layer that prevents hydrogen sulfide from penetrating.

[0025] Example 2: This example is based on Example 1, but differs from Example 1 in that it discloses a mineral magnesium oxide insulated fireproof cable, comprising the following components by weight fraction: 40 parts modified magnesium oxide, 35 parts modified LDHs, and 55 parts borate glass powder.

[0026] The other components and preparation methods are the same as in Example 1.

[0027] Example 3: This example is based on Example 1, but differs from Example 1 in that it discloses a mineral magnesium oxide insulated fireproof cable, comprising the following components by weight fraction: 45 parts modified magnesium oxide, 40 parts modified LDHs, and 60 parts borate glass powder.

[0028] Example 4: This example is based on Example 1, but differs from Example 1 in that the raw materials for preparing the borate glass powder in this example include the following components by weight fraction: 20 parts SiO2, 35 parts B2O3, 25 parts Bi2O3, 4 parts Na2CO3, 5 parts CaCO3, and 1 part Al2O3.

[0029] The other components and preparation methods are the same as in Example 1.

[0030] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that the modified magnesium oxide in this comparative example is not modified with zinc oxide.

[0031] The method for preparing the modified magnesium oxide includes the following steps: S11. Dissolve 8.5g of chitosan in 500mL of 2% acetic acid solution, add 100g of magnesium oxide powder, sonicate for 30min, add 8mL of glutaraldehyde solution, adjust pH to 5.5, heat to 50℃ and react for 6h, filter the reaction solution to collect the solid, wash with deionized water and anhydrous ethanol, vacuum dry at 80℃ for 24h, grind through a 200-mesh sieve to obtain modified magnesium oxide.

[0032] The other components and preparation methods are the same as in Example 1.

[0033] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that the modified magnesium oxide described in this comparative example is not grafted with chitosan. The method for preparing the modified magnesium oxide includes the following steps: S11. 100g of magnesium oxide powder was ultrasonically dispersed in 500mL of deionized water to obtain magnesium oxide slurry; 24.2g of Zn(CH3COO)2·2H2O was dissolved in 200mL of deionized water and slowly added dropwise to the magnesium oxide slurry. The pH was adjusted to 8~8.5 with ammonia water. The mixture was stirred at 60℃ for 4h. The resulting reaction solution was filtered to collect the solid, washed with deionized water, dried in an oven at 80℃ for 12h, and calcined in a tube furnace under a nitrogen protective atmosphere at a rate of 5℃ / min to 400℃ and held for 2h to obtain modified magnesium oxide.

[0034] The other components and preparation methods are the same as in Example 1.

[0035] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that the modified LDHs described in this comparative example are not modified with sodium carboxymethyl cellulose.

[0036] The preparation method of the modified LDHs includes the following steps: S21. Dissolve 30.8g Mg(NO3)2·6H2O and 11.3g Al(NO3)3·9H2O in 300mL deionized water to obtain a salt solution; dissolve 24g NaOH and 15.9g Na2CO3 in 300mL deionized water to obtain an alkaline solution; under stirring, slowly add the salt solution and alkaline solution dropwise to 100mL deionized water simultaneously, stir and age for 2h, let stand to precipitate, filter and collect the solid, wash with deionized water, transfer to a high-pressure reactor, hydrothermally crystallize at 100℃ for 12h, cool and remove, wash and filter, vacuum dry at 60℃ for 24h to obtain LDHs powder; S22. Dissolve 3.16g KMnO4 in 100mL deionized water to obtain potassium permanganate solution; ultrasonically disperse 10g LDHs powder in 200mL deionized water, slowly add potassium permanganate solution, transfer to high pressure reactor, hydrothermally react at 120℃ for 6h, cool and remove, centrifuge, wash with deionized water, vacuum dry at 60℃ for 24h to obtain modified LDHs.

[0037] The other components and preparation methods are the same as in Example 1.

[0038] Comparative Example 4: This comparative example is based on Example 1, but differs from Example 1 in that the modified LDHs described in this comparative example do not contain potassium permanganate.

[0039] The preparation method of the modified LDHs includes the following steps: S21. Dissolve 30.8g Mg(NO3)2·6H2O and 11.3g Al(NO3)3·9H2O in 300mL deionized water to obtain a salt solution; dissolve 24g NaOH and 15.9g Na2CO3 in 300mL deionized water to obtain an alkaline solution; under stirring, slowly add the salt solution and alkaline solution dropwise to 100mL deionized water simultaneously, stir and age for 2h, let stand to precipitate, filter and collect the solid, wash with deionized water, transfer to a high-pressure reactor, hydrothermally crystallize at 100℃ for 12h, cool and remove, wash and filter, vacuum dry at 60℃ for 24h to obtain LDHs powder; S22. Dissolve 1.2g of sodium carboxymethyl cellulose in 100mL of deionized water to obtain a sodium carboxymethyl cellulose solution; disperse 10g of LDH powder in 200mL of deionized water, slowly add the sodium carboxymethyl cellulose solution, sonicate for 30min, stir and react at room temperature for 6h, and spray dry at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain modified LDHs.

[0040] The other components and preparation methods are the same as in Example 1.

[0041] Comparative Example 5: This comparative example is based on Example 1, but unlike Example 1, no modified LDHs are added.

[0042] The other components and preparation methods are the same as in Example 1.

[0043] Comparative Example 6: This comparative example is based on Example 1, but unlike Example 1, no borate glass powder is added.

[0044] The other components and preparation methods are the same as in Example 1.

[0045] Comparative Example 7: The insulating powder described in this comparative example includes pure magnesium oxide powder of the same mass as the insulating powder of Example 1.

[0046] The other components and preparation methods are the same as in Example 1.

[0047] Experimental verification: Experiment 1: Place the cable sample (50cm in length) in a sealed reactor, inject H2S gas at a concentration of 5000ppm, and place it at normal pressure and 200℃. Detect the insulation resistance at 0h and 500h, calculate the insulation resistance retention rate, set up 3 parallel tests, and take the average value.

[0048] Table 1. Test results of resistance to hydrogen sulfide corrosion:

[0049] Table 1 shows the test results of resistance to hydrogen sulfide corrosion. The data in the table can be seen that the modified magnesium oxide, modified LDHs and borate glass powder in the cable prepared by this invention work synergistically to effectively inhibit the penetration of hydrogen sulfide and block the reaction between hydrogen sulfide and magnesium oxide, thus preventing the insulation performance from deteriorating.

[0050] Experiment 2: (1) Test the insulation resistance of the cable in accordance with GB / T 3048.5-2007.

[0051] (2) Test the breakdown voltage of the cable in accordance with GB / T 3048.8-2007.

[0052] (3) Test the dielectric strength of the cable according to IEC 60243-1.

[0053] (4) Test the fire resistance of the cable according to BS 6387:2013. After burning at 950℃ for 90 minutes, observe the circuit integrity and test the insulation resistance after cooling.

[0054] (5) Test the tensile strength of the cable in accordance with GB / T 13033.2-2007.

[0055] Table 2. Basic performance tests of cables:

[0056] Table 2 shows the basic performance test results of the cable. As can be seen from the data in the table, the basic performance of the cable prepared by the present invention is similar to that of the pure magnesium oxide cable, and Example 3 is the best solution.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A mineral magnesium oxide insulated fireproof cable, characterized in that, From the inside out, it includes a nickel-chromium alloy heating core, insulating powder, and oxygen-free copper tube; The insulating layer powder comprises the following components by weight fraction: 40-45 parts modified magnesium oxide, 35-40 parts modified LDHs, and 55-60 parts borate glass powder; The modified magnesium oxide is zinc oxide-modified magnesium oxide grafted with chitosan; The modified LDHs were modified with sodium carboxymethyl cellulose-MnO2; The borate glass powder includes SiO2, B2O3, Bi2O3, Na2O, CaO, and Al2O3, and has a glass transition temperature of 290~320℃.

2. The mineral magnesium oxide insulated fireproof cable according to claim 1, characterized in that, The method for preparing the modified magnesium oxide includes the following steps: S11. Disperse magnesium oxide powder ultrasonically in deionized water to obtain magnesium oxide slurry; dissolve Zn(CH3COO)2·2H2O in deionized water with stirring, slowly add it dropwise to magnesium oxide slurry, adjust the pH with ammonia water, stir the reaction, filter the resulting reaction solution to collect the solid, wash with deionized water, dry in an oven, and calcine in a tube furnace to obtain ZnO@MgO composite powder; S12. Chitosan was dissolved in acetic acid solution by stirring, ZnO@MgO composite powder was added, ultrasonically dispersed, glutaraldehyde solution was added, pH was adjusted, and the reaction was heated. The resulting reaction solution was filtered to collect the solid, washed with deionized water and anhydrous ethanol, vacuum dried, ground and sieved to obtain modified magnesium oxide.

3. The mineral magnesium oxide insulated fireproof cable according to claim 1, characterized in that, The preparation method of the modified LDHs includes the following steps: S21. Dissolve Mg(NO3)2·6H2O and Al(NO3)3·9H2O in deionized water to obtain a salt solution; dissolve NaOH and Na2CO3 in deionized water to obtain an alkaline solution; while stirring, slowly add the salt solution and alkaline solution dropwise to deionized water simultaneously, stir and age, let stand to precipitate, collect the solid by vacuum filtration, wash with deionized water, transfer to a high-pressure reactor, hydrothermally crystallize, cool and remove, wash and filter, vacuum dry to obtain LDHs powder; S22. Dissolve KMnO4 in deionized water to obtain potassium permanganate solution; ultrasonically disperse LDHs powder in deionized water, slowly add potassium permanganate solution, transfer to high pressure reactor, hydrothermal reaction, cool and remove, centrifuge, wash with deionized water, vacuum dry to obtain LDHs-MnO2; S23. Dissolve sodium carboxymethyl cellulose in deionized water to obtain a sodium carboxymethyl cellulose solution; disperse LDHs-MnO2 in deionized water, slowly add the sodium carboxymethyl cellulose solution, sonicate, stir to react, and spray dry to obtain modified LDHs.

4. The mineral magnesium oxide insulated fireproof cable according to claim 1, characterized in that, The method for preparing the borate glass powder includes: mixing SiO2, B2O3, Bi2O3, Na2CO3, CaCO3 and Al2O3, ball milling, placing the mixed powder in a corundum crucible, heating and melting it in a high-temperature furnace, pouring the resulting molten glass liquid into cold water for rapid cooling, drying the resulting glass block, ball milling, and sieving to obtain borate glass powder.

5. A mineral magnesium oxide insulated fireproof cable according to claim 4, characterized in that, The raw materials for preparing the borate glass powder include the following components by weight fraction: 20-25 parts SiO2, 35-40 parts B2O3, 25-30 parts Bi2O3, 4-6 parts Na2CO3, 5-7 parts CaCO3, and 1-2 parts Al2O3.

6. A method for preparing a mineral magnesium oxide insulated fire-resistant cable, applied to the preparation of a mineral magnesium oxide insulated fire-resistant cable as described in any one of claims 1 to 5, characterized in that, The method includes the following steps: S1. Mix modified magnesium oxide, modified LDHs and borate glass powder, add anhydrous ethanol and sodium hexametaphosphate, ball mill and mix, dry and sieve to obtain insulating layer powder; S2. Place the nickel-chromium alloy heating core in the center of the oxygen-free copper tube, slowly pour in the insulating powder, vacuum vibrate and compact it, and use multi-pass drawing and diameter reduction molding. S3. Place the drawn cable in a tube furnace, heat it to 300℃ at 5℃ / min, hold it at that temperature for 2 hours for high-temperature activation treatment, cool it to room temperature, and seal both ends with argon arc welding to obtain the cable.

7. The method for preparing a mineral magnesium oxide insulated fireproof cable according to claim 6, characterized in that, The multi-pass drawing process consists of 8 passes, resulting in a final product with an outer diameter of Φ6.5mm and an insulation layer thickness of 1.8mm. The drawing process generates axial compressive stress, causing the powder to achieve a compaction density of 2.5~3.0g / cm³. 3 .

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