Regeneration process of waste magnesia carbon brick based on hydration technology

Abstract

The present application relates to the technical field of waste magnesite-carbon brick, and particularly relates to a waste magnesite-carbon brick regeneration process based on hydration technology, which comprises the following steps: crushing waste magnesite-carbon brick, carrying out hydration treatment, drying and screening to obtain recycled aggregate, mixing the recycled aggregate with fused magnesite, modified flaky graphite, metal aluminum powder and thermosetting phenolic resin, shaping and solidifying to obtain recycled magnesite-carbon brick. The present application solves the problem that the strong hydrophobicity and dense layered structure of large flaky graphite form a closed effect on water penetration and gas escape, so that CH4 gas generated by hydration of Al4C3 after secondary waste cannot be effectively released, thereby causing explosion.

Description

Technical Field

[0001] This invention belongs to the field of waste magnesia-carbon brick technology, specifically a waste magnesia-carbon brick regeneration process based on hydration technology. Background Technology

[0002] Magnesia-carbon bricks are widely used as working linings for smelting containers such as converters and ladles due to their excellent resistance to slag erosion and thermal shock stability. Existing magnesia-carbon brick materials typically employ large-flake graphite, utilizing its high thermal conductivity, low coefficient of thermal expansion, and non-wetting properties against molten slag to improve the material's thermal shock resistance and slag erosion resistance. The large aspect ratio and flake structure of large-flake graphite help form a network skeleton within the material, thereby enhancing toughness, thermal shock resistance, and oxidation resistance. Furthermore, to improve high-temperature oxidation resistance, aluminum powder is often added to magnesia-carbon bricks. At high temperatures, aluminum reacts with carbon to form aluminum carbide (Al4C3) whiskers, which can enhance the material's strength and toughness. However, Al4C3 is chemically unstable and readily undergoes a hydration reaction in humid environments: generating Al(OH)3 and releasing CH4 gas, causing volume expansion. This reaction is the root cause of cracking and pulverization of waste magnesia-carbon bricks during storage, severely limiting their feasibility for recycling.

[0003] To address the stability issues caused by Al4C3 hydration, existing treatment technologies often employ hydration methods. The principle is to pre-hydrate the Al4C3 in waste bricks under controlled conditions, converting it into stable Al(OH)3, thereby eliminating the risk of expansion and cracking during subsequent regeneration. Existing research optimizes the treatment process by adjusting hydration temperature and time or introducing surfactants. However, in practical applications, the effectiveness of these methods is often limited by the microstructural characteristics of the waste magnesia-carbon bricks. Research has found that Al4C3 in waste bricks does not exist in isolation, but is tightly encapsulated by highly hydrophobic, densely layered large flake graphite. This structure constitutes a physical barrier to water penetration. During hydration, water can only slowly penetrate through microscopic defects between graphite layers, causing the Al4C3 hydration reaction to occur within a relatively closed micro-region. The generated CH4 gas is difficult to escape smoothly due to the obstruction of the graphite layers, leading to a continuous accumulation of gas pressure within the micro-region. When the internal stress exceeds the critical strength threshold of the particle itself, it will cause the particle to suddenly burst and break from the inside, generating a large amount of fine powder, which will reduce the yield of recycled aggregate. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a waste magnesia-carbon brick recycling process based on hydration technology, in order to solve the problem that the strong hydrophobicity and dense layered structure of large flake graphite create a sealing effect on water penetration and gas escape, which prevents the effective release of CH4 gas generated by Al4C3 hydration after secondary waste disposal, thus causing explosions.

[0006] (2) Technical solution

[0007] The waste magnesia-carbon brick recycling process based on hydration technology includes the following steps:

[0008] M1. Pre-treatment of waste magnesia-carbon bricks: Use a jaw crusher to crush the waste magnesia-carbon bricks into 10-30mm blocks to obtain the crushed material;

[0009] M2. Hydration treatment: The crushed material is soaked in constant temperature water at 85-90℃ until no bubbles are generated, and the hydrated material is obtained.

[0010] M3. Drying and Screening: The hydrated material is dried to a moisture content of <0.1%; after being processed by a roller mill, it is screened by a vibrating screen to obtain recycled magnesia-carbon brick aggregate;

[0011] M4. Ingredients and mixing: Add recycled magnesia-carbon brick aggregate and fused magnesia particles, dry mix; add 65% thermosetting phenolic resin, mix; add modified flake graphite and aluminum powder, mix; add the remaining 35% thermosetting phenolic resin, mix until uniform, and obtain the mixed material.

[0012] M5. Molding and Curing: The mixed materials are shaped and cured at 200-250℃ to obtain recycled magnesia-carbon bricks;

[0013] Modified flake graphite is obtained by mixing modified silica, modified alumina, and graphite treated with mixed acid oxidation, followed by phenolic resin-assisted composite and step-curing modification; the modified silica is obtained by copolymerization modification with methacryloyloxyethyltrimethylammonium chloride and trifluoroethyl methacrylate; the modified alumina is obtained by copolymerization with TPGDA and KH570.

[0014] Further, step M4 includes the following raw materials in parts by weight: 60-70 parts of recycled magnesia-carbon brick aggregate, 15-25 parts of fused magnesia granules, 8-12 parts of modified flake graphite, 2-3 parts of metallic aluminum powder, and 3-5 parts of thermosetting phenolic resin.

[0015] Furthermore, the method for preparing the modified silica includes the following steps:

[0016] M11. Add nano-silica dried at 105℃ to a 1% sodium hydroxide solution and disperse by ultrasonication; after reaction, filter and collect solid A; wash with deionized water to pH 6.0-7.0; then wash with anhydrous ethanol; dry the washed solid A to obtain pretreated silica;

[0017] M12. Add pretreated silica to anhydrous ethanol and disperse by ultrasonication to obtain a silica suspension; weigh 80% methacryloyloxyethyltrimethylammonium chloride aqueous solution and trifluoroethyl methacrylate and mix them evenly to obtain a monomer mixture;

[0018] M13. Add the monomer mixture to the silica suspension and stir; add the initiator AIBN, purge with nitrogen to remove oxygen, heat to 65°C and stir to react; filter after reaction and collect solid B; wash with anhydrous ethanol and deionized water in sequence; dry the washed solid B to obtain modified silica.

[0019] Furthermore, the mass ratio of the pure monomer methacryloyloxyethyltrimethylammonium chloride to trifluoroethyl methacrylate is 2:1; the initiator AIBN accounts for 1% of the sum of the pure mass of methacryloyloxyethyltrimethylammonium chloride and the mass of trifluoroethyl methacrylate.

[0020] Furthermore, the preparation method of the modified aluminum oxide includes the following steps:

[0021] M21. Add nano-alumina dried at 105℃ to anhydrous ethanol and disperse by ultrasonication to obtain a dispersion; dissolve KH570 in a mixed solution containing anhydrous ethanol and deionized water, adjust the pH to 4-5 with glacial acetic acid, and hydrolyze by stirring at room temperature to obtain KH570 hydrolysate.

[0022] M22. Add KH570 hydrolysate dropwise to the dispersion, and add TPGDA and AIBN at the same time. Stir until homogeneous. Purge with nitrogen to remove air, heat to 75°C and stir to react, to obtain a suspension.

[0023] M23. After the reaction is complete, cool the suspension and filter it to collect the precipitate. Wash the precipitate with anhydrous ethanol to remove unreacted monomers and homopolymers. Dry the washed precipitate to obtain modified aluminum oxide.

[0024] Furthermore, in step M22, the mass ratio of TPGDA to KH570 is 2:1.

[0025] Furthermore, the preparation method of the modified flake graphite includes the following steps:

[0026] M31. Slowly add flake graphite to a mixed acid oxidation solution at 0-5℃, control the temperature ≤10℃ and stir to allow the graphite to undergo initial oxidation; then raise the temperature to 40-50℃, keep the temperature constant and stir to allow the oxidation reaction to proceed fully, and obtain a reaction slurry;

[0027] M32. Cool to room temperature, pour the reaction slurry into deionized water at 0-5℃ while stirring, to obtain a diluted mixture; let the diluted mixture stand, pour off the supernatant and filter; wash with deionized water until the pH of the filtrate is 6.0-7.0; finally wash with anhydrous ethanol; collect the filter cake, dry it and grind and sieve it to obtain graphite oxide;

[0028] M33. Modified silica and modified aluminum oxide are added to anhydrous ethanol and ultrasonically dispersed to form suspension A; graphite oxide is added to anhydrous ethanol and ultrasonically dispersed to form suspension B; suspension A is poured into suspension B to obtain mixed suspension A;

[0029] M34. Dissolve thermosetting phenolic resin in anhydrous ethanol and add it to mixed suspension A to obtain mixed suspension B; introduce nitrogen gas to remove oxygen from the reaction system; place mixed suspension B at 75°C to react, so that the phenolic resin is fully wetted and adsorbed on the surface of solid particles; after the reaction is completed, raise the temperature to 90°C and stir to distill off the ethanol until the material becomes a viscous paste, then stop heating.

[0030] M35. Transfer the viscous paste to a polytetrafluoroethylene petri dish and spread it evenly; place it in a forced-air drying oven for step curing, and allow it to cool naturally to room temperature to obtain a cured block; grind the cured block and sieve it to obtain modified flake graphite.

[0031] Further, in step M31, the mixed acid oxidation solution is prepared by mixing concentrated sulfuric acid and nitric acid in a volume ratio of 3:1; the amount of the mixed acid oxidation solution used is 8-12 mL per gram of flake graphite.

[0032] Furthermore, the stepped curing process is divided into three steps: low-temperature curing: curing at 80℃ for 2 hours; medium-temperature curing: curing at 120℃ for 2 hours; and high-temperature curing: curing at 180-200℃ for 6 hours.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] 1. Modified silica with an asymmetric bifunctional surface structure was prepared by surface-coating and copolymerizing methacryloyloxyethyltrimethylammonium chloride (a hydrophilic quaternary ammonium salt monomer) and trifluoroethyl methacrylate (a low surface energy fluoroalkyl monomer) onto the surface of nano-silica. The hydrophilic segments of the quaternary ammonium salt preferentially anchor to the oxygen-containing functional group sites at the graphite edge through electrostatic adsorption, constructing hydrophilic capillary channels in the edge micro-regions. The low surface energy fluoroalkyl segments face the free side, ensuring the overall compatibility of the modified material with the graphite surface. The spatial distribution of both components plays a distinct role, precisely opening preferential pathways for water penetration and gas escape without compromising the overall hydrophobic properties of graphite.

[0035] 2. KH570 is anchored to the surface of nano-alumina via surface condensation reaction, introducing polymerizable double bonds. Subsequently, it copolymerizes with TPGDA under AIBN initiation, constructing a flexible organic coating layer containing residual acrylate active groups on the alumina surface. Modified alumina and modified silica are anchored to oxygen-containing functional group sites at the edges of flake graphite, forming an edge nanocomposite structure. Its hydrophilic microregions and interfacial flexibility provide a preferential pathway for gas escape along the graphite edges. The flexible layer formed by TPGDA crosslinking can buffer the volume expansion stress induced by Al(OH)3 formation, inhibiting microcrack propagation. The residual acrylate active groups introduced by KH570 may participate in the curing and crosslinking reaction of phenolic resin, helping to enhance the interfacial bonding strength between the modified material and the resin matrix, thereby improving the mechanical properties of the composite system.

[0036] 3. Two modified materials are combined with mixed acid graphite oxide and cured in stages with phenolic resin to form a three-dimensional composite structure of "graphite oxide substrate - nanoparticle edge anchoring - resin coating and locking", permanently locking the preferred gas escape path to the graphite edge region. This structure can play a toughening role during the service stage of new bricks; more importantly, when new bricks are discarded and recycled, the nano-modified layer pre-placed at the graphite edge plays a role through two independent mechanisms: first, the modified silica and modified alumina components react with magnesium oxide in the aggregate during the high-temperature service stage to generate forsterite and spinel, respectively, strengthening the interfacial bonding at the graphite edge; second, after the organic coating layer is carbonized and pyrolyzed, microporous channels are left in situ at the graphite edge, which can guide water penetration and CH4 gas escape during secondary regeneration hydration, mitigating the risk of cracking. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the preparation process of waste magnesium-carbon brick regeneration based on hydration technology in Embodiment 1 of the present invention. Detailed Implementation

[0038] 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.

[0039] Example 1: This example discloses a waste magnesia-carbon brick recycling process based on hydration technology, including the following steps:

[0040] M1. Pre-treatment of waste magnesia-carbon bricks: Use a jaw crusher to crush the waste magnesia-carbon bricks into 10-30mm blocks to obtain the crushed material;

[0041] M2. Hydration treatment: The crushed material is soaked in constant temperature water at 85-90℃ for 24 hours until no bubbles are generated, and the hydrated material is obtained.

[0042] M3. Drying and screening: The hydrated material is dried at 150-200℃ until the moisture content is <0.1%; after being processed by a roller mill for 7 minutes, it is screened by a vibrating screen to collect particles of 1-5mm size to obtain recycled magnesia-carbon brick aggregate.

[0043] M4. Ingredients and mixing: Add recycled magnesia-carbon brick aggregate and fused magnesia particles, dry mix for 2 minutes; add 65% thermosetting phenolic resin, mix for 3 minutes; add modified flake graphite and aluminum powder, mix for 3 minutes; add the remaining 35% thermosetting phenolic resin, mix until uniform, and obtain the mixed material.

[0044] M5. Molding and curing: The mixed materials are molded on a friction brick press under a pressure of 20MPa and held for 1 minute to obtain the molded brick blank; the molded brick blank is cured at 200-250℃ for 12-24h to obtain recycled magnesia-carbon brick;

[0045] Modified flake graphite is obtained by mixing modified silica, modified alumina, and graphite treated with mixed acid oxidation, followed by phenolic resin-assisted composite and step-curing modification; the modified silica is obtained by copolymerization modification with methacryloyloxyethyltrimethylammonium chloride and trifluoroethyl methacrylate; the modified alumina is obtained by copolymerization with TPGDA and KH570.

[0046] It should be noted that in step M4, a process of adding phenolic resin in two batches is adopted: the first batch of 65% of the resin is preferentially dry-mixed with recycled aggregate and fused magnesia, which aims to make the resin uniformly coat the surface of the aggregate, reduce the interfacial energy of the mixed system, create favorable conditions for the subsequent introduction of modified flake graphite, and avoid the agglomeration of lightweight graphite powder; the second batch of 35% of the resin is added after graphite and aluminum powder are added and mixed, which aims to further fill the gaps between particles, optimize the distribution of the binder, and thus improve the density of the molded green body and the mechanical properties of the cured material.

[0047] Step M4 ingredients include the following raw materials in parts by weight: 65 parts recycled magnesia-carbon brick aggregate, 20 parts fused magnesia granules, 10 parts modified flake graphite, 2.5 parts aluminum powder, and 4 parts thermosetting phenolic resin.

[0048] The method for preparing the modified silica includes the following steps:

[0049] M11. Add 5g of nano-silica dried at 105℃ for 2h to 100mL of 1% sodium hydroxide solution and ultrasonically disperse for 30min; heat to 60℃ and stir for 2h; cool and filter to collect solid A; wash with 50mL of deionized water to pH 6.0-7.0; then wash with 50mL of anhydrous ethanol, repeating twice; dry the washed solid A at 80℃ for 12h to obtain pretreated silica.

[0050] M12. Add the pretreated silica to 100 mL of anhydrous ethanol and sonicate for 30 min to obtain a silica suspension; weigh 1.9 g of 80% methacryloyloxyethyl trimethylammonium chloride aqueous solution and 0.75 g of trifluoroethyl methacrylate and mix them evenly to obtain a monomer mixture.

[0051] M13. Add the monomer mixture to the silica suspension and stir for 10 min; add 0.023 g of initiator AIBN and purge with nitrogen for 30 min to remove oxygen; heat to 65 °C and stir for 6 h; cool and filter to collect solid B; wash with 50 mL of anhydrous ethanol, repeat 3 times; wash with 50 mL of deionized water, repeat 2 times; dry the washed solid B at 50 °C for 12 h to obtain modified silica.

[0052] The mass ratio of the pure monomer methacryloyloxyethyltrimethylammonium chloride to trifluoroethyl methacrylate is 2:1; the initiator AIBN accounts for 1% of the sum of the pure mass of methacryloyloxyethyltrimethylammonium chloride and the mass of trifluoroethyl methacrylate.

[0053] The method for preparing the modified aluminum oxide includes the following steps:

[0054] M21. Add 5g of nano-alumina dried at 105℃ for 2h to 100mL of anhydrous ethanol and sonicate for 30min to obtain a dispersion; dissolve 0.5g of KH570 in a mixed solution containing 20mL of anhydrous ethanol and 2mL of deionized water, adjust the pH to 4-5 with glacial acetic acid, and stir at room temperature for 30min to obtain KH570 hydrolysate;

[0055] M22. Add KH570 hydrolysate dropwise to the dispersion, along with 1.0 g of TPGDA and 0.015 g of AIBN, and stir until homogeneous; purge with nitrogen for 30 min to remove air, heat to 75 °C and stir for 5 h to obtain a suspension; during this process, KH570 first anchors to the surface of aluminum oxide, and then copolymerizes with TPGDA to form a cross-linked coating layer;

[0056] M23. After the reaction is complete, cool the suspension and filter it to collect the precipitate. Wash the precipitate three times with 50 mL of anhydrous ethanol to remove unreacted monomers and homopolymers. Dry the washed precipitate at 50 °C for 12 h to obtain modified aluminum oxide.

[0057] In step M22, the mass ratio of TPGDA to KH570 is 2:1.

[0058] The method for preparing the modified flake graphite includes the following steps:

[0059] M31. At 0-5℃ and with stirring, slowly add 10g of flake graphite to 100mL of mixed acid oxidation solution at 0-5℃, control the temperature ≤10℃ and stir for 2h to allow the graphite to undergo initial oxidation; then raise the temperature to 40-50℃ and stir at a constant temperature for 4h to allow the oxidation reaction to proceed fully and obtain the reaction slurry.

[0060] M32. Cool to room temperature, pour the reaction slurry into 500 mL of 0-5℃ deionized water while stirring to obtain a diluted mixture; let the diluted mixture stand, discard the supernatant and filter; wash repeatedly with 200-300 mL of deionized water until the pH of the filtrate is 6.0-7.0; finally wash once with 20-30 mL of anhydrous ethanol; collect the filter cake and dry it at 80℃ for 12 h; grind and pass through a 200-mesh sieve to obtain graphite oxide;

[0061] M33. Weigh 2.0g of modified silica and 2.0g of modified aluminum oxide respectively; add them to 100mL of anhydrous ethanol and sonicate for 30min to form suspension A; add 2.0g of graphite oxide to 100mL of anhydrous ethanol and sonicate for 30min to form suspension B; slowly pour suspension A into suspension B and stir for 10min to obtain mixed suspension A;

[0062] M34. Dissolve 1.0 g of thermosetting phenolic resin in 20 mL of anhydrous ethanol, and slowly add it to mixed suspension A to obtain mixed suspension B; purge with nitrogen for 30 min to remove oxygen from the reaction system; place mixed suspension B in a 75℃ constant temperature water bath and stir for 2 h to fully wet the phenolic resin and adsorb it onto the surface of the solid particles; after the reaction is complete, raise the temperature to 90℃, stir and evaporate the ethanol until the material becomes a viscous paste, and stop heating;

[0063] M35. Transfer the viscous paste to a polytetrafluoroethylene petri dish and spread it evenly; place it in a forced-air drying oven for step curing, and allow it to cool naturally to room temperature to obtain a cured block; coarsely crush the cured block with a mortar and pestle, and pass it through a 200-mesh standard sieve to obtain modified flake graphite.

[0064] In step M31, the mixed acid oxidation solution is prepared by mixing concentrated sulfuric acid and nitric acid in a volume ratio of 3:1; the amount of the mixed acid oxidation solution used is 8-12 mL per gram of flake graphite.

[0065] The stepped curing process consists of three steps: low-temperature curing (curing at 80℃ for 2 hours), medium-temperature curing (curing at 120℃ for 2 hours), and high-temperature curing (curing at 180-200℃ for 6 hours).

[0066] It should be noted that, as Figure 1 This is a flowchart illustrating the preparation process of waste magnesium-carbon brick regeneration based on hydration technology in Embodiment 1 of the present invention.

[0067] Example 2: This example is based on Example 1, but differs from Example 1 in that the recycled magnesia-carbon brick in this example includes the following raw materials in parts by weight: 60 parts of recycled magnesia-carbon brick aggregate, 15 parts of fused magnesia granules, 8 parts of modified flake graphite, 2 parts of metallic aluminum powder, and 3 parts of thermosetting phenolic resin.

[0068] The remaining preparation methods are the same as in Example 1.

[0069] Example 3: This example is based on Example 1, but differs from Example 1 in that the recycled magnesia-carbon brick in this example includes the following raw materials in parts by weight: 70 parts of recycled magnesia-carbon brick aggregate, 25 parts of fused magnesia granules, 12 parts of modified flake graphite, 3 parts of metallic aluminum powder, and 5 parts of thermosetting phenolic resin.

[0070] The remaining preparation methods are the same as in Example 1.

[0071] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that unmodified silica is used instead of modified silica.

[0072] The remaining components and preparation methods are the same as in Example 1.

[0073] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that unmodified aluminum oxide is used instead of modified aluminum oxide.

[0074] The remaining components and preparation methods are the same as in Example 1.

[0075] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that unmodified silica and unmodified aluminum oxide are used to replace both modified silica and modified aluminum oxide.

[0076] The remaining components and preparation methods are the same as in Example 1.

[0077] Comparative Example 4: This comparative example is based on Example 1, but differs from Example 1 in that the modified flake graphite in this comparative example does not contain modified silicon dioxide.

[0078] The remaining components and preparation methods are the same as in Example 1.

[0079] Comparative Example 5: This comparative example is based on Example 1, but differs from Example 1 in that the modified flake graphite in this comparative example does not contain modified aluminum oxide.

[0080] The remaining components and preparation methods are the same as in Example 1.

[0081] Comparative Example 6: This comparative example is based on Example 1, but differs from Example 1 in that the modified flake graphite in this comparative example does not contain phenolic resin.

[0082] The remaining components and preparation methods are the same as in Example 1.

[0083] Comparative Example 7: This comparative example is based on Example 1, but differs from Example 1 in that the modified flake graphite described in this comparative example is not subjected to gradient curing.

[0084] In this comparative example, the preparation method of modified flake graphite was adjusted based on Example 1 as follows: In step M35, the step-curing process was changed to a conventional drying process: after transferring the viscous paste to a petri dish, it was dried at 80°C for 12 hours. The remaining components and preparation methods were the same as in Example 1.

[0085] Comparative Example 8: This comparative example is based on Example 1, but differs from Example 1 in that unmodified flake graphite is used instead of modified flake graphite.

[0086] The remaining components and preparation methods are the same as in Example 1.

[0087] Comparative Example 9: This comparative example is based on Example 1, but differs from Example 1 in that the modified silica in this comparative example is not modified with methacryloyloxyethyltrimethylammonium chloride.

[0088] In this comparative example, the preparation method of modified silica was adjusted based on Example 1 as follows: In step M13, the amount of initiator AIBN added was adjusted to 1% of the mass of trifluoroethyl methacrylate, i.e., 0.0075 g. The remaining components and preparation methods were the same as in Example 1.

[0089] Comparative Example 10: This comparative example is based on Example 1, but differs from Example 1 in that the modified silica described in this comparative example is not modified with trifluoroethyl methacrylate.

[0090] In this comparative example, the preparation method of modified silica was adjusted based on Example 1 as follows: In step M13, the amount of initiator AIBN added was adjusted to 1% of the pure mass of methacryloyloxyethyltrimethylammonium chloride, i.e., 0.0152 g. The remaining components and preparation methods were the same as in Example 1.

[0091] Comparative Example 11: This comparative example is based on Example 1, but differs from Example 1 in that the modified aluminum oxide described in this comparative example is not modified with TPGDA.

[0092] The remaining components and preparation methods are the same as in Example 1.

[0093] Comparative Example 12: This comparative example is based on Example 1, but differs from Example 1 in that the modified aluminum oxide described in this comparative example is not modified with KH570.

[0094] In this comparative example, the preparation method of modified alumina was adjusted from that in Example 1 as follows: the preparation process of KH570 hydrolysate was omitted. All other components and preparation methods remained the same as in Example 1.

[0095] Experimental verification:

[0096] Verification 1: Physical Properties of Recycled Magnesia-Carbon Bricks

[0097] Operating steps: room temperature compressive strength (refer to GB / T 5072-2023): take the cured brick samples of Examples 1-3 and Comparative Examples 1-12, cut them into 50mm×50mm×50mm cubic test blocks, and take 5 parallel samples for each group.

[0098] (1) Apply pressure at a loading rate of 1.0 MPa / s on a universal testing machine, record the failure load, and calculate the average value.

[0099] (2) Apparent porosity (refer to GB / T 2997-2015): Weigh the dried sample (m1). After vacuum impregnation with water, weigh the suspended weight (m2) and saturated weight (m3). Calculation formula: .

[0100] (3) Antioxidant test: For each of Examples 1-3 and Comparative Examples 1-12, a 50mm×50mm×50mm sample block was taken and placed in a high-temperature furnace. Under air atmosphere, the temperature was increased to 1000℃ at 5℃ / min and held for 3h. After cooling, it was cut along the center and the thickness of the decarburized layer was measured (the average value of 5 points was taken).

[0101] Verification 2: Stability of secondary hydration

[0102] Operating Procedures: The recycled magnesia-carbon bricks prepared in Examples 1-3 and Comparative Examples 1-12 were placed in a high-temperature furnace and heat-treated at 1400℃ under nitrogen protection for 2 hours to simulate their service process in high-temperature environments such as steel ladles, ensuring sufficient carbonization of the organic components. The high-temperature treated brick samples were then crushed again into 10-30mm blocks, 5kg per batch. A traditional single-step hydration process (immersion in 80℃ constant-temperature water for 24 hours) was uniformly adopted to simulate the processing conditions for future secondary recycling.

[0103] Determination of mass loss rate: weighing before hydration (m 前 After hydration, collect all materials, dry them at 150℃, and weigh them (m). 后 Calculate the loss rate; a higher loss rate indicates more fine powder generated during the explosion, and a lower secondary regeneration value. Calculation formula: .

[0104] Observation of cracking phenomenon: Record whether there are cracking sounds and particle breakage during the hydration process.

[0105] Table 1. Results of physical properties of recycled magnesia-carbon bricks:

[0106]

[0107] Table 2. Results of secondary hydration stability:

[0108]

[0109] As shown in Table 1, the room temperature compressive strength, apparent porosity, and anti-oxidation decarburization layer thickness of Examples 1-3 are all superior to those of the comparative examples, verifying the improvement effect of the present invention on the overall service performance of recycled bricks. As shown in Table 2, the secondary hydration mass loss rate of Examples 1-3 is lower than that of the comparative examples, verifying that the present invention fundamentally solves the problem of recycling recycled magnesia-carbon bricks after they are discarded again.

[0110] 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 waste magnesia-carbon brick recycling process based on hydration technology, characterized in that, Includes the following steps: M1. Pre-treatment of waste magnesia-carbon bricks: Use a jaw crusher to crush the waste magnesia-carbon bricks into 10-30mm blocks to obtain the crushed material; M2. Hydration treatment: The crushed material is soaked in constant temperature water at 85-90℃ until no bubbles are generated, and the hydrated material is obtained. M3. Drying and Screening: The hydrated material is dried to a moisture content of <0.1%; after being processed by a roller mill, it is screened by a vibrating screen to obtain recycled magnesia-carbon brick aggregate; M4. Batching and mixing: The recycled magnesia-carbon brick aggregate, fused magnesia, modified flake graphite, metallic aluminum powder and thermosetting phenolic resin are mixed evenly to obtain the mixed material. M5. Molding and Curing: The mixed materials are shaped and cured at 200-250℃ to obtain recycled magnesia-carbon bricks; Modified flake graphite is obtained by mixing modified silica, modified alumina, and graphite treated with mixed acid oxidation, followed by phenolic resin-assisted composite and step-curing modification. The modified silica was obtained by copolymerization modification with methacryloyloxyethyltrimethylammonium chloride and trifluoroethyl methacrylate; Modified alumina was obtained by copolymerization of TPGDA and KH570.

2. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 1, characterized in that, Step M4 includes the following raw materials in parts by weight: 60-70 parts recycled magnesia-carbon brick aggregate, 15-25 parts fused magnesia granules, 8-12 parts modified flake graphite, 2-3 parts metallic aluminum powder, and 3-5 parts thermosetting phenolic resin.

3. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 1, characterized in that, The method for preparing the modified silica includes the following steps: M11. Add nano-silica dried at 105℃ to a 1% sodium hydroxide solution and disperse by ultrasonication; after reaction, filter and collect solid A; wash with deionized water to pH 6.0-7.0; then wash with anhydrous ethanol; dry the washed solid A to obtain pretreated silica; M12. Add the pretreated silica to anhydrous ethanol and disperse it by ultrasonication to obtain a silica suspension; weigh an 80% (w / w) aqueous solution of methacryloyloxyethyltrimethylammonium chloride and trifluoroethyl methacrylate and mix them evenly to obtain a monomer mixture; M13. Add the monomer mixture to the silica suspension and stir; add the initiator AIBN, purge with nitrogen, heat to 65°C and stir to react; filter after reaction and collect solid B; wash with anhydrous ethanol and deionized water in sequence; dry the washed solid B to obtain modified silica.

4. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 3, characterized in that, The mass ratio of the pure monomer methacryloyloxyethyltrimethylammonium chloride to trifluoroethyl methacrylate is 2:1; the initiator AIBN accounts for 1% of the sum of the pure mass of methacryloyloxyethyltrimethylammonium chloride and the mass of trifluoroethyl methacrylate.

5. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 1, characterized in that, The method for preparing the modified aluminum oxide includes the following steps: M21. Add nano-alumina dried at 105℃ to anhydrous ethanol and disperse by ultrasonication to obtain a dispersion; dissolve KH570 in a mixed solution containing anhydrous ethanol and deionized water, adjust the pH to 4-5 with glacial acetic acid, and hydrolyze by stirring at room temperature to obtain KH570 hydrolysate. M22. Add KH570 hydrolysate dropwise to the dispersion, and add TPGDA and AIBN at the same time. Stir until homogeneous. Purge with nitrogen and heat to 75°C. Stir to react and obtain a suspension. M23. After the reaction is complete, cool the suspension, filter it, and collect the precipitate; wash it with anhydrous ethanol; dry the washed precipitate to obtain modified aluminum oxide.

6. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 5, characterized in that, In step M22, the mass ratio of TPGDA to KH570 is 2:

1.

7. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 1, characterized in that, The method for preparing the modified flake graphite includes the following steps: M31. Slowly add flake graphite to a mixed acid oxidation solution at 0-5℃, control the temperature ≤10℃ and stir; then raise the temperature to 40-50℃, keep the temperature constant and stir to obtain a reaction slurry; M32. Cool to room temperature, pour the reaction slurry into deionized water at 0-5℃ while stirring, to obtain a diluted mixture; let the diluted mixture stand, pour off the supernatant and filter; wash with deionized water until the pH of the filtrate is 6.0-7.0; finally wash with anhydrous ethanol; collect the filter cake, dry it and grind and sieve it to obtain graphite oxide; M33. Modified silica and modified aluminum oxide are added to anhydrous ethanol and ultrasonically dispersed to form suspension A; graphite oxide is added to anhydrous ethanol and ultrasonically dispersed to form suspension B; suspension A is poured into suspension B to obtain mixed suspension A; M34. Dissolve thermosetting phenolic resin in anhydrous ethanol and add it to mixed suspension A to obtain mixed suspension B; introduce nitrogen gas; place mixed suspension B at 75°C for reaction; after the reaction is completed, raise the temperature to 90°C and stir until the material becomes a viscous paste, then stop heating; M35. Transfer the viscous paste to a polytetrafluoroethylene petri dish and spread it evenly; place it in a forced-air drying oven for step curing, and allow it to cool naturally to room temperature to obtain a cured block; grind the cured block and sieve it to obtain modified flake graphite.

8. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 7, characterized in that, In step M31, the mixed acid oxidation solution is prepared by mixing concentrated sulfuric acid and nitric acid in a volume ratio of 3:1; the amount of the mixed acid oxidation solution used is 8-12 mL per gram of flake graphite.

9. The waste magnesia-carbon brick regeneration process based on hydration technology according to claim 7, characterized in that, The stepped curing process consists of three steps: low-temperature curing (curing at 80℃ for 2 hours), medium-temperature curing (curing at 120℃ for 2 hours), and high-temperature curing (curing at 180-200℃ for 6 hours).

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