Low-carbon magnesium carbon brick and preparation method thereof

Abstract

The application discloses a low-carbon magnesia carbon brick and a preparation method thereof, and relates to the technical field of weather-resistant magnesia carbon bricks. The low-carbon magnesia carbon brick comprises the following components in parts by mass: fused magnesia particles 80-90 parts, fused magnesia fine powder 15-25 parts, flake graphite 5-10 parts, nano carbon powder 1-5 parts, phenolic resin 10-20 parts, curing agent 0.2-1.5 parts, antioxidant 0.5-3 parts, and modifier 0-8 parts. The core lies in a triple synergistic protection mechanism of the antioxidant, which comprises the electron delocalization of a conjugated pi bond system to stabilize free radicals, the physical isolation of a tert-butyl group, and the formation of a high-temperature barrier layer of a silane group. This effectively delays the oxidation loss of graphite, strengthens the resistance to slag penetration, and improves the service performance of the material under extreme storage conditions.

Description

Technical Field

[0001] This invention relates to the field of weather-resistant magnesia-carbon brick technology, specifically to a low-carbon magnesia-carbon brick and its preparation method. Background Technology

[0002] As a key refractory material, the weather resistance of magnesia-carbon bricks directly affects industrial production efficiency and safety. Traditional magnesia-carbon bricks face numerous weather resistance challenges under long-term storage conditions. On the one hand, long-term storage makes the bricks susceptible to oxidation reactions with oxygen, especially the oxidation of graphite, leading to a loose brick structure and reduced strength. This oxidation reaction not only consumes brick materials but may also generate volatile gases, further exacerbating peeling and damage. On the other hand, after environmental erosion, magnesia-carbon bricks must withstand the erosion of oxide-containing slag in complex smelting environments. This causes the magnesia components in the brick to gradually dissolve, damaging the structural integrity of the brick and significantly reducing its refractory performance.

[0003] While existing technologies have attempted to slow graphite oxidation by adding antioxidants, issues such as the amount of antioxidant added and the compatibility of the antioxidant material with other components of the brick still cannot completely solve the problems of environmental oxidation and erosion. Furthermore, under the combined effects of ultraviolet radiation and oxygen-containing free radical corrosion, the internal stress distribution of the brick becomes uneven during long-term storage, easily leading to microcracks. These cracks become channels for corrosive substances to penetrate, accelerating the damage to the brick. Therefore, developing a low-carbon magnesia-carbon brick with stronger weather resistance is of great significance for improving production efficiency, reducing maintenance costs, and ensuring production safety in high-temperature industries such as steel smelting. This brick needs to achieve comprehensive breakthroughs in oxidation resistance, erosion resistance, and structural stability to meet the high-performance requirements of modern industry for refractory materials. Summary of the Invention

[0004] The present invention aims to provide a low-carbon magnesia-carbon brick that significantly improves its long-term storage resistance to oxidation and erosion, thereby solving the problem of existing high-carbon bricks being prone to oxidation and peeling in the environment.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a low-carbon magnesia-carbon brick, characterized in that it comprises the following components in parts by weight: 80-90 parts of fused magnesia particles, 15-25 parts of fused magnesia fine powder, 5-10 parts of flake graphite, 1-5 parts of nano carbon powder, 10-20 parts of phenolic resin, 0.2-1.5 parts of curing agent, 0.5-3 parts of antioxidant, and 1-8 parts of modifier;

[0006] The antioxidant is a compound represented by Formula 1:

[0007] Formula 1;

[0008] In Formula 1, Z1 is selected from any one of the following: -CH2-, -C(CH3)2-, -C(=O)-, O, and S.

[0009] Furthermore, the particle size of the fused magnesia particles is 5mm-0.1mm.

[0010] Furthermore, the particle size of the fused magnesia fine powder is less than 0.1 mm.

[0011] Furthermore, the fixed carbon content of the flake graphite is ≥97wt%, and the particle size is less than 0.15mm.

[0012] Furthermore, the nano-carbon powder is selected from nano-carbon black or nano-graphene, and has a specific surface area ≥100m². 2 / g.

[0013] Furthermore, the phenolic resin is selected from: methyl phenolic resin.

[0014] Furthermore, the curing agent is hexamethylenetetramine.

[0015] Furthermore, the modifier is Al2O3.

[0016] Furthermore, the antioxidant is any one of the compounds shown in the following structures:

[0017] ;

[0018] ;

[0019] .

[0020] A method for preparing low-carbon magnesia-carbon bricks includes the following steps:

[0021] (1) Premixing: After heating 1 / 2 part by weight of the phenolic resin to 100-140°C, add the total part by weight of the flake graphite, nano carbon powder and antioxidant, and stir and mix for 5-15 minutes to obtain the premix.

[0022] (2) Hot mixing: The fused magnesia particles and the modifier are added to the premix and mixed at 80-120℃ for 5-10 minutes to obtain the hot mix;

[0023] (3) Cold mixing: Reduce the temperature of the hot mix to below 60°C, add the fused magnesium sand powder, the remaining composite phenolic resin and curing agent, mix for 10-30 minutes until uniform, and obtain the cold mix.

[0024] (4) Molding: The cold mixed material is loaded into the mold and pressed into shape under a pressure of 100-300MPa. The shaped brick blank is heat-treated at 150-250℃ for 12-24 hours to cure. The surface of the cured brick blank is polished to obtain a low-carbon magnesium-carbon brick.

[0025] Furthermore, in step (4), after curing, the temperature is reduced to 23-25°C by air cooling, and the material is trapped at 25-35°C for 1-4 hours.

[0026] Furthermore, steps (1) and (4) are performed under a nitrogen atmosphere.

[0027] The antioxidant described in this invention achieves high-temperature protection through a triple synergistic mechanism: the core polyphenol nucleus contains a conjugated π-bond system, whose active hydrogen preferentially reduces oxygen free radicals to generate phenoxy free radicals, while the conjugated structure delocalizes the free radical electrons, stabilizing the free radicals and interrupting chain oxidation at high temperatures; the tert-butyl group in the molecule has high bond energy and hydrophobicity, delaying oxidation and inhibiting water vapor side reactions; the silane group, with its high bond energy, forms a stable network barrier at high temperatures, enhancing resistance to slag penetration. Ultimately, through the synergistic effect of electron delocalization stabilization of the conjugated nucleus, physical isolation by the tert-butyl group, and the protective layer of the silane group, the graphite component in the magnesia-carbon brick is dynamically protected, significantly reducing oxidation loss and slag erosion under environmental conditions, achieving a breakthrough in weather resistance. The antioxidant described in this invention mainly provides long-term weather resistance, enabling magnesia-carbon bricks to maintain good performance even after prolonged exposure to natural environments.

[0028] This invention addresses the problems of easy oxidation (graphite oxidation leading to structural loosening) and slag erosion (magnesia dissolution damaging the structure) of traditional magnesia-carbon bricks at high temperatures, achieving breakthroughs through optimized component ratios and synergistic effects. Specifically: fused magnesia particles and fine powder form a dense gradient framework, reducing slag penetration channels; flake graphite and nano-carbon powder synergistically construct a composite carbon network, the latter adsorbing free radicals with its high specific surface area, thus assisting in protecting the graphite matrix; phenolic resin cross-links and cures under the action of a curing agent, forming a resin-carbon layer encapsulating carbon components and magnesia, reducing the oxidation exposure surface; the modifier Al2O3 generates a high-melting-point compound at high temperatures, filling micropores and inhibiting slag penetration. The core lies in the triple synergistic protection mechanism of antioxidants, which protects the layer and enhances erosion resistance. The preparation process (premixing antioxidants and carbon components under a nitrogen atmosphere, temperature-controlled curing, and material trapping) ensures uniform component dispersion and structural integrity.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. Significantly Improved Structural Integrity and Weather Resistance: This invention significantly reduces the problems of loose brick structure and spalling caused by oxidation reactions and slag erosion at high temperatures through a gradient skeleton design of fused magnesia particles and fine powder, the construction of a composite carbon network of flake graphite and nano-carbon powder, and a protective layer formed by phenolic resin curing. This enhances the overall stability and damage resistance of the material, enabling the brick to remain dense and strong in complex high-temperature environments.

[0031] 2. Comprehensive Enhancement of High-Temperature Antioxidant and Anti-Corrosion Capabilities: The core lies in the triple synergistic protection mechanism of antioxidants, including the electronic delocalization stabilization of free radicals by the conjugated π-bond system, the physical isolation effect of tert-butyl groups, and the formation of a high-temperature barrier layer by silane groups. This effectively delays graphite oxidation and enhances resistance to slag penetration, thereby improving the material's service performance under extreme storage conditions.

[0032] 3. Long-term durability is effectively maintained: The present invention exhibits excellent stability in aging exposure tests, with improved retention of room temperature compressive strength and good bulk density. Attached Figure Description

[0033] Figure 1 This is the NMR spectrum of antioxidant 1 described in this invention. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely 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.

[0035] Preparation Example 1

[0036] Synthesis of Antioxidant 1:

[0037] .

[0038] Under a nitrogen atmosphere, 150 ml of DMSO, 16.22 g of potassium phosphate trihydrate, 0.37 g of pyridine-2-carboxylic acid, 0.3 g of CuI, 10.00 g of raw material 1, and 10.68 g of raw material 2 were added sequentially to the reaction system. The reaction was carried out at 85 °C for 16 h under a nitrogen atmosphere. After cooling, the reaction mixture was extracted with ammonia solution and methyl tert-butyl ether. The organic phase was washed five times with water and then twice with saturated NaCl solution. The combined organic phases were dried with anhydrous magnesium sulfate, evaporated to dryness, and subjected to column chromatography (silica gel column chromatography, with a mixed solution of n-heptane and ethyl acetate as the eluent). Evaporation was performed to dryness, yielding 12.46 g of intermediate 1.

[0039] Under nitrogen protection, 12.46 g of intermediate 1 and 10.00 g of raw material 3 were dissolved in 150 ml of toluene solution. 4.72 g of sodium tert-butoxide, 0.67 g of tris(dibenzylacetone)dipalladium, and 2.48 g of tri-tert-butylphosphine were added sequentially. The mixture was stirred until homogeneous, heated to 120 °C, and refluxed for 10 h. After the reaction was complete, the temperature was slightly lowered, and the mixture was filtered using silica gel. The filtrate was cooled to room temperature, washed three times with water, and the organic phase was retained. The aqueous phase was then extracted with ethyl acetate. The combined organic phases were dried over anhydrous magnesium sulfate, evaporated to dryness, and subjected to column chromatography (silica gel column chromatography, using a mixed solution of n-heptane and ethyl acetate as the eluent). The solution was evaporated to dryness to obtain 15.72 g of antioxidant 1.

[0040] Product structure identification:

[0041] Mass spectrometry of intermediate 1 (M / Z MS+H) + :508;

[0042] Mass spectrometry of antioxidant 1 (M / Z MS+H) + 767;

[0043] Antioxidant 1 1 H NMR (Chloroform-d, Figure 1 ): δ 8.72 (s, 1H), 7.33 (t, 2H), 7.15 (m, 1H), 7.03 (m, 1H), 6.96 (m, 1H), 6.87 (d, 1H), 6.82-6.76 (m, 2H), 6.50 (m, 1H), 4.27-4.03 (m, 8H), 3.78-3.60 (m, 3H), 2.26-2.12 (m, 3H), 1.50-1.46 (m, 9H), 1.46-1.41 (m, 9H), 1.28-1.18 (m, 9H), 0.76-0.64 (m, 9H).

[0044] Preparation Examples 2-5

[0045] In Preparation Examples 2-5, antioxidants 2-5 were prepared sequentially, following the preparation method of Preparation Example 1, except that raw material 2 was replaced, and the rest remained the same as in Preparation Example 1. See Table 1 for details.

[0046] Table 1.

[0047]

[0048] Example 1

[0049] Preparation of a low-carbon magnesia-carbon brick:

[0050] 1. Raw material components:

[0051] Fused magnesia granules: 85 parts (particle size range: 1-3mm, purchased from: Haicheng Zhonghao Magnesium Industry Co., Ltd.);

[0052] Fused magnesia fine powder: 20 parts (particle size: <0.1mm, purchased from: Qinghai Western Magnesium Industry Co., Ltd.);

[0053] Flake graphite: 7 parts (fixed carbon content ≥97wt%, particle size: 0.1mm, purchased from Qingdao Jinhui Graphite Co., Ltd.);

[0054] Nano-carbon powder: 3 parts (using nano-graphene, specific surface area ≥150m²) 2 / g, purchased from: Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0055] Phenolic resin: 15 parts (selected as methyl phenolic resin (phenolic resin 2402), purchased from Jiangsu Senbo New Materials Co., Ltd.);

[0056] Curing agent: 1 part (hexamethylenetetramine, purchased from Shandong Xuchen Chemical Technology Co., Ltd.);

[0057] Antioxidant: 2 parts (use antioxidant 1);

[0058] Modifier: 4 parts (Al2O3, purchased from Zibo Honghao Crystal Materials Co., Ltd.).

[0059] 2. Preparation method:

[0060] (1) Premixing: Under a nitrogen atmosphere, take 7.5 parts of phenolic resin, heat to 120°C, add all the flake graphite (7 parts), nano carbon powder (3 parts) and antioxidant (2 parts), stir and mix for 10 minutes until uniformly dispersed to obtain the premix;

[0061] (2) Hot mixing: Transfer the premix to a mixing device, add fused magnesia particles (85 parts) and modifier (4 parts), mix at 100°C for 8 minutes to obtain hot mix;

[0062] (3) Cold mixing: Cool the hot mixture to 50°C, add fused magnesia fine powder (20 parts), the remaining phenolic resin (7.5 parts) and curing agent (1 part), mix for 20 minutes until uniform, and obtain cold mixture;

[0063] (4) Molding: The process is carried out under a nitrogen atmosphere. The cold mixture is loaded into the mold and pressed under a pressure of 200MPa. The molded brick blank is placed at 200℃ for 18 hours for curing. After curing, the temperature of the brick blank is reduced to 24℃ by air cooling and then the material is trapped at 30℃ for 2 hours. The surface of the brick blank is polished until it is smooth and without protrusions to obtain a low-carbon magnesium-carbon brick.

[0064] Examples 2-5

[0065] The preparation of a low-carbon magnesium-carbon brick is carried out by referring to the preparation method of Example 1, except that the antioxidant is replaced sequentially with antioxidant 2-antioxidant 5 prepared in Preparation Examples 2-5, and the rest is the same as in Example 1.

[0066] Comparative Example 1

[0067] The preparation of a low-carbon magnesia-carbon brick is carried out according to the preparation method of Example 1, except that the antioxidant is replaced with antioxidant MBZ (CAS: 3030-80-6), and the rest is the same as in Example 1.

[0068] Comparative Example 2

[0069] The preparation of a low-carbon magnesium-carbon brick is carried out according to the preparation method of Example 1, except that the antioxidant is replaced with antioxidant 1425 (CAS: 65140-91-2), and the rest is the same as in Example 1.

[0070] Comparative Example 3

[0071] The preparation of a low-carbon magnesium-carbon brick is the same as in Example 1, except that the antioxidant is not added.

[0072] Comparative Example 4

[0073] The preparation of a low-carbon magnesia-carbon brick is the same as in Example 1, except that no modifier is added.

[0074] Comparative Example 5

[0075] The preparation of a low-carbon magnesium-carbon brick is the same as in Example 1, except that nano-carbon powder is not added.

[0076] Performance testing:

[0077] 1. The room temperature compressive strength was determined according to the test method in GB / T5072-2023 "Test Method for Compressive Strength of Refractory Materials at Room Temperature". The data are shown in Table 2.

[0078] 2. The high-temperature flexural strength at 1250℃ for 0.5h was determined according to the test method in GB / T3002-2017 "Test Method for High-Temperature Flexural Strength of Refractory Materials". The data are shown in Table 2.

[0079] 3. The low-carbon magnesia-carbon bricks prepared in the examples and comparative examples were heat-treated at 1400℃ for 2 hours and then cooled naturally. The bulk density was then determined according to the method in GB / T2997-2015 "Test Methods for Bulk Density, Apparent Porosity and True Porosity of Dense Shaped Refractory Products". The data are shown in Table 2.

[0080] 4. The low-carbon magnesium-carbon brick samples prepared in the examples and comparative examples were placed in a xenon lamp aging test chamber and exposed for 4800 hours. The retention rate of room temperature compressive strength was tested, and the data are shown in Table 2.

[0081] Exposure conditions: Radiation intensity: 0.35 W / m 2 (At 340nm wavelength); Temperature cycling: 80℃ (light stage) to 20℃ (dark stage), 8 hours of light + 4 hours of condensation (simulated rain) per cycle; Relative humidity: 50%±5% (light stage), 95%±5% (condensation stage).

[0082] Table 2.

[0083]

[0084] The low-carbon magnesia-carbon bricks of the present invention (Examples 1-5) significantly outperform the control samples (Comparative Examples 1-5) in several key performance indicators. Specifically, the examples exhibit superior stability and improvement in room temperature compressive strength, high temperature flexural strength, bulk density, and room temperature compressive strength retention rate, indicating stronger structural integrity and weather resistance. In contrast, the comparative examples show a decreasing trend in strength, density, and retention rate, especially in the absence of specific antioxidants or key components (such as modifiers or nano-carbon powder), where performance degradation is more pronounced, highlighting the effectiveness of the component synergistic mechanism of the present invention. These trends consistently confirm the advantages of the present invention in long-term oxidation and erosion resistance, while maintaining the long-term durability of the material.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-carbon magnesia-carbon brick, characterized in that, The product contains the following components in parts by weight: 80-90 parts of fused magnesia granules, 15-25 parts of fused magnesia fine powder, 5-10 parts of flake graphite, 1-5 parts of nano carbon powder, 10-20 parts of phenolic resin, 0.2-1.5 parts of curing agent, 0.5-3 parts of antioxidant, and 1-8 parts of modifier. The antioxidant is a compound represented by Formula 1: In Formula 1, Z1 is selected from any one of: -CH2-, -C(CH3)2-, -C(=O)-, O, and S; The modifier is Al2O3.

2. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The particle size of the fused magnesia is 5mm-0.1mm; The particle size of the fused magnesia fine powder is less than 0.1 mm.

3. The low-carbon magnesia-carbon brick according to claim 1, characterized in that, The flake graphite has a fixed carbon content of ≥97wt% and a particle size of less than 0.15mm.

4. A low-carbon magnesia-carbon brick according to claim 1, characterized in that, The nano-carbon powder is selected from nano-carbon black or nano-graphene, and has a specific surface area ≥100m². 2 / g.

5. A low-carbon magnesia-carbon brick according to claim 1, characterized in that, The phenolic resin is selected from: methyl phenolic resin.

6. A low-carbon magnesia-carbon brick according to claim 1, characterized in that, The curing agent is hexamethylenetetramine.

7. A method for preparing a low-carbon magnesia-carbon brick according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Premixing: After heating 1 / 2 part by weight of the phenolic resin to 100-140°C, add the total part by weight of the flake graphite, nano carbon powder and antioxidant, and stir and mix for 5-15 minutes to obtain the premix. (2) Hot mixing: The fused magnesia particles and the modifier are added to the premix and mixed at 80-120℃ for 5-10 minutes to obtain the hot mix; (3) Cold mixing: Reduce the temperature of the hot mix to below 60°C, add the fused magnesium sand powder, the remaining composite phenolic resin and curing agent, mix for 10-30 minutes until uniform, and obtain the cold mix. (4) Molding: The cold mixed material is loaded into the mold and pressed into shape under a pressure of 100-300MPa. The shaped brick blank is heat-treated at 150-250℃ for 12-24 hours to cure. The surface of the cured brick blank is polished to obtain a low-carbon magnesium-carbon brick.

8. The method for preparing a low-carbon magnesia-carbon brick according to claim 7, characterized in that, In step (4), after curing, the temperature is reduced to 23-25℃ by air cooling, and the material is trapped at 25-35℃ for 1-4 hours.

9. The method for preparing a low-carbon magnesia-carbon brick according to claim 7, characterized in that, Steps (1) and (4) are performed under a nitrogen atmosphere.

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