Method for preparing refractory material for hot metal pretreatment vessel using low rank solid waste

Abstract

This invention belongs to the field of refractory materials technology and discloses a method for preparing refractory materials for molten iron pretreatment containers using low-rank solid waste. The method uses waste silicon carbide carbon bricks as the main raw material, crushing them into 8-0mm recycled material, subjecting it to nitriding treatment, and sieving it into recycled aggregates and fine powders of different particle sizes. The recycled material, pyrophyllite, zirconium corundum, silicon carbide, graphite, zirconium mullite fine powder, metallic silicon powder, aluminum powder, composite rare earth oxides, and reinforcing agents are added in stages with a binder, mixed, machine-pressed, and dried to produce silicon carbide carbon recycled brick products. This invention prepares recycled material through nitriding treatment, performs grading, and selects a reasonable particle size distribution to achieve a close-packed gradation of the billet. Utilizing an activated sintering mechanism, adding high-melting-point zirconium materials and composite additives, and selecting appropriate process parameters, silicon carbide carbon recycled bricks with high hot strength, excellent thermal shock stability, and resistance to permeation erosion are prepared, achieving resource recycling.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and in particular to a method for preparing refractory materials for molten iron pretreatment containers using low-rank solid waste. Background Technology

[0002] Hot metal pretreatment plays a crucial role in improving product quality, optimizing production processes, and reducing production costs during the iron and steel smelting process. The performance and service life of the refractory materials used in the hot metal pretreatment working lining are of paramount importance. Currently, hot metal pretreatment working linings are generally constructed using aluminum-silicon carbide-carbon bricks. These bricks are mainly composed of bauxite aggregates and powders, supplemented with external materials such as silicon carbide, graphite, and metal additives. With the gradual depletion of high-alumina bauxite resources in my country, the market price of bauxite raw materials has been increasing year by year, and quality fluctuations have been frequent, affecting the cost of refractory materials and the quality of finished products.

[0003] On the other hand, the large-scale accumulation of waste refractory materials using bauxite as raw material results in low-level solid waste, leading to the waste of non-renewable resources. Obtaining raw materials from waste refractory products and using them as a high-quality secondary resource to partially or completely replace high-alumina bauxite in refractory product production can not only save mineral resources and energy and reduce environmental pollution, but also save on refractory material and steelmaking costs, which is of great significance for the recycling of refractory raw material resources. Waste aluminum-silicon carbide-carbon brick recycled materials, with bauxite as the main raw material, have become a substitute for bauxite aggregate in aluminum-silicon carbide-carbon bricks. Furthermore, because they still contain graphite, silicon carbide, and other raw materials required for aluminum-silicon carbide-carbon bricks, they possess even greater advantages for recycling. Waste aluminum-silicon carbide-carbon bricks, if selected, classified, and processed using special techniques, can yield valuable refractory materials. However, the current recycling rate of waste aluminum-silicon carbide-carbon bricks is very low. Excessive addition of recycled materials is detrimental to the high-temperature flexural strength and slag erosion resistance of the recycled bricks. When added in a mixed form, such as in Al2O3-SiC-C lining bricks for mixed iron trains, the amount of waste aluminum-silicon carbide-carbon brick recycled materials should not exceed 30%. How to increase the amount of waste aluminum-silicon carbide-carbon brick recycled materials while ensuring performance and lifespan, and thus improve the recycling rate of waste refractory materials, is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a method for using waste aluminum-silicon carbide-carbon bricks, which have been degraded to low-level solid waste, as recycled raw materials. After nitriding, their performance is improved. They serve as a partial substitute for aggregates such as bauxite, silicon carbide, and graphite in the traditional preparation of aluminum-silicon carbide-carbon bricks. Two different zirconium compounds, reinforcing agents, and additives are added to prepare working lining bricks for molten iron pretreatment containers, thereby improving the performance and service life of molten iron pretreatment containers.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing refractory materials for molten iron pretreatment containers using low-rank solid waste, comprising the following steps:

[0006] Step 1: Recycle waste aluminum silicon carbide carbon bricks and remove the residual steel, residual iron, residue and permeated altered layer adhering to their surface by hammering and mechanical cutting.

[0007] Step 2: Put the aluminum silicon carbide carbon brick waste into a jaw crusher for crushing and processing into 8-0mm recycled material particles. During the crushing process, the crushed recycled material particles are magnetically separated to remove iron.

[0008] Step 3: Place the recycled material particles into a nitriding furnace and nitrid them at 1150-1350℃ for 5-10 hours. After nitriding, the recycled material is then rolled and shaped by a roller mill and screened to obtain recycled aggregates of 8-5mm, 5-3mm, 3-1mm, and 1-0.088mm and recycled fine powder of less than 0.088mm.

[0009] Step 4: According to the weighed proportions, put the recycled aggregate, pyrophyllite, zirconium corundum, and silicon carbide into the mixing mill and mix for 5-8 minutes. Add 75-80% of the total amount of binder and mix for 5-8 minutes. Then add graphite and mix for 5-8 minutes. Finally, add the recycled fine powder, zirconium mullite fine powder, metallic silicon powder, aluminum powder, composite rare earth oxides, and reinforcing agent and mix for 35-40 minutes. Then add 20-25% of the total amount of binder and mix for 15-20 minutes. Discharge the material.

[0010] Step 5: Press the mixed clay material into standard bricks of 230×114×65mm on an 800t brick press. After the standard bricks are naturally dried for 12 hours, they are dried in a tunnel kiln at 200-300℃ for 12-24 hours to produce aluminum silicon carbide carbon recycled brick products.

[0011] The weight proportions of the raw materials added in step four are as follows: 55-75 parts recycled aggregate, 3-8 parts zirconium corundum, 3-5 parts zirconium mullite fine powder, 5-8 parts graphite, 8-10 parts silicon carbide, 5-8 parts pyrophyllite, 5-10 parts recycled fine powder, 2-4 parts metallic silicon powder, 1-2 parts aluminum powder, 0.5-2 parts reinforcing agent, 1-2 parts composite rare earth oxide, and a binder that accounts for 2-5% of the total weight of the raw materials.

[0012] Of the total weight of recycled material, 20-30% consists of recycled aggregate with a particle size of 8-5mm, 20-40% consists of recycled aggregate with a particle size of 5-3mm, 10-15% consists of recycled aggregate with a particle size of 3-1mm, and 5-10% consists of recycled aggregate with a particle size of 1-0.088mm. The amount of recycled fine powder added accounts for 10-35% of the total weight of recycled material. The recycled material contains 57-66wt% Al2O3, 8-11wt% SiO2, and 8-13wt% C.

[0013] The particle size of zirconium corundum is 1-0.088 mm; the particle size of zirconium mullite fine powder is ≤0.088 mm.

[0014] The graphite contains ≥94wt% C and has a particle size ≤0.088mm.

[0015] The silicon carbide contains ≥96wt% SiC and has a particle size ≤0.088mm.

[0016] The particle size of both the silicon powder and aluminum powder is 0-180 mesh.

[0017] Among them, the composite rare earth oxide is composed of yttrium oxide and lanthanum oxide in a mass ratio of 1:1.5.

[0018] Among them, silicon powder and aluminum powder are composite antioxidants, and silicon powder and aluminum powder are mixed in a mass ratio of 2:1.

[0019] The reinforcing agent is at least one of aluminum diboride powder, zirconium diboride, or titanium diboride.

[0020] The binder is thermosetting phenolic resin and aluminum dihydrogen phosphate powder, with a mass ratio of 1:1.5.

[0021] The properties of the recycled material after nitriding treatment are as follows: apparent porosity of 7.6-8.5%, bulk density of 2.95-3.1 g / cm³, and water absorption rate of 2.7-3.1%.

[0022] After nitriding, the free Si in the recycled material can be effectively nitrided into α-Si3N4 phase and a small amount of β-Si3N4 phase, which effectively improves the bulk density and strength of the raw material. The recycled material contains silicon nitride and aluminum nitride, providing a source of inexpensive silicon nitride and aluminum nitride. During high-temperature use, silicon nitride, aluminum nitride and alumina are synthesized in situ into silon corundum mullite multiphase material. In the multiphase material, the main crystalline phases corundum and mullite particles constitute the framework structure of the material. The in-situ generated silon combines mullite and zirconium corundum together to form a dense structure. AlN can dissolve in Al2O3 at high temperatures to form a composite ceramic phase with a SiC / Si3N4 and silane interwoven network crystal structure. AlN is not corroded by molten metal, making the aluminum silicon carbide carbon brick matrix more resistant to high-temperature erosion and improving its hot strength. Compared with traditional aluminum silicon carbide carbon bricks, recycled aluminum silicon carbide carbon bricks are more resistant to high-temperature erosion, reduce the coefficient of expansion of the brick body at the operating temperature, maintain volume stability, and have higher slag resistance, high-temperature performance and seismic performance.

[0023] Pyrophyllite is a natural, layered, hydrous aluminosilicate mineral with a refractoriness greater than 1700℃. At 1100℃–1300℃, pyrophyllite gradually decomposes, forming high-temperature stable mullite and cristobalite phases. By fully utilizing the basic properties of pyrophyllite and silicon carbide, the products begin to sinter and densify at medium to low temperatures, without volume shrinkage, and do not crack under rapid temperature changes. They can withstand the impact of steel slag and metals, have strong creep resistance, and exhibit excellent resistance to slag penetration and erosion.

[0024] Introducing two different zirconium materials, zirconium corundum and zirconium mullite, into recycled bricks to replace tabular corundum allows ZrO2 to gradually transform from monoclinic to tetragonal and cubic phases as the temperature rises, dispersing throughout the material. During sintering, the dispersed ZrO2 undergoes a phase transformation, forming a number of microcracks within the matrix material. These microcracks nucleate and propagate under the action of tensile stress at their tips, consuming and dispersing the energy at the tips of the main cracks and hindering the propagation of dangerous cracks. Utilizing the phase transformation toughening mechanism of ZrO2, the material's flexibility, anti-stripping performance, and thermal shock resistance are improved through the phase transformation of ZrO2. Furthermore, the formation of a solid solution activates the crystal lattice, creating vacancies that promote sintering, further enhancing the chemical erosion resistance and thermal shock resistance of mullite, and reducing its coefficient of thermal expansion. This improves the high-temperature mechanical properties of the composite material, resulting in excellent resistance to slag and iron erosion and thermal shock resistance.

[0025] Simultaneous addition of metallic silicon powder and aluminum powder as composite antioxidants in the Al2O3-SiC-C system allows them to play different roles at different temperature stages. When aluminum powder and metallic silicon powder are added at a mass ratio of 1:2, the strength and oxidation resistance of the refractory material are significantly improved. Metallic Al is beneficial to the medium and low temperature performance of the material, while metallic Si mainly plays a role in the medium and high temperature stages, especially affecting the strength of the sample after high-temperature treatment. In addition to the respective antioxidant properties of Al powder and Si powder, it is also possible that Al and Si form a eutectic, which lowers the melting temperature of Al and Si, thus changing the reaction of the metal powder to exert its antioxidant properties from a solid-solid reaction to a solid-liquid reaction, making the reaction easier to occur and thus enhancing the oxidation resistance of the refractory material.

[0026] In addition, the addition of micro-powders such as metallic silicon powder and aluminum powder as microporous additives allows aluminum and silicon to oxidize in situ during high-temperature use, generating oxides that fill some of the pores and thus reducing the apparent porosity of the composite material. The oxides generated by oxidation are highly reactive and readily react with substances in the matrix. Metallic aluminum powder has a low melting point and can form a liquid phase dispersed in the green body at a lower firing temperature, which not only facilitates material sintering but also helps solve the problem of uneven performance.

[0027] The micro-powder added in this invention can penetrate into the gaps between raw material particles, achieving full sintering of the material green body at a lower temperature by relying on the activity of the micro-powder, forming a novel activated sintering. Some ultra-fine powder particles penetrate into the composite ceramic phase with the SiC and Si3N4 interwoven network crystal structure generated in subsequent processes. They not only adhere to the surface of the ceramic crystal structure, forming a strong skeleton and significantly improving the strength of the final product, but also penetrate into the voids of the ceramic crystal sintering layer, playing a secondary protective role, preventing penetration, and thus improving the material's corrosion resistance. By integrating particle compaction, micropores, and dense high-strength technology, the density and strength of the material are further improved, and the porosity is reduced, producing microporous, dense, and high-strength recycled alumina silicon carbide carbon refractory bricks.

[0028] During high-temperature applications, the rare earth oxide yttrium oxide can act as a sintering aid, helping to refine grains and promote densification during sintering. Doping alumina with lanthanum oxide can improve thermal stability and suppress high-temperature phase transformations. The addition of rare earth oxides can significantly reduce reaction activation energy, promote grain refinement, improve mechanical properties, and enhance thermal shock resistance. Forming a solid solution with the matrix not only effectively lowers the sintering temperature but also promotes grain development and improves mechanical properties.

[0029] Aluminum diboride, zirconium diboride, or titanium diboride are added as reinforcing phases to the composite matrix. In the boride lattice, boron atoms form structural units in the form of single bonds, double bonds, networks, and spatial skeletons. As the relative boron content in the boride increases, the structural units become more complex; the more complex the structure, the stronger its oxidation resistance. Its high elastic modulus and oxidation resistance can improve the overall performance of the material, preparing high-performance reinforced composite materials that significantly enhance the strength, hardness, and high-temperature mechanical properties of recycled composite materials.

[0030] Damage to carbon-containing furnace lining materials includes chemical erosion by the melt and structural thermal stress failure. The relationship between chemical erosion by the melt and its penetration into the lining material, the material's microstructure, porosity, and pore size is significant. This invention employs refractory material densification technology. Through particle size distribution technology in the batching and forming stage, i.e., the close packing of continuously sized particles of the refractory material, the porosity of the refractory brick blank is reduced. When the addition of coarse recycled aggregate particles (8-5mm, 5-3mm) is 40-70%, fine particles (3-1mm, 1-0.088mm) is 20-25%, and fine recycled powder is 10-35%, the bulk density of the recycled material is high, the porosity is low, and the particle size distribution is reasonable. Furthermore, the design and control of internal solid-phase reactions and sintering during high-temperature service promotes material densification, thereby reducing pore volume and pore size.

[0031] This invention utilizes a mixer and a roller mill to process recycled granules twice, effectively removing "false granules." The roller mill's extrusion process reduces the bulk density of the granules with increasing compaction time. The mixing process has been optimized, significantly improving the quality of the final product. Furthermore, this invention introduces reinforcing agents, composite rare earth oxides, composite antioxidants, and binders into the formula, greatly increasing the amount of recycled material added and resulting in recycled silicon carbide aluminum bricks with higher hot strength, stronger slag resistance, better thermal shock stability, and superior resistance to water penetration.

[0032] The beneficial effects of this invention are as follows: The refractory material for the working lining of the molten iron pretreatment container produced by this invention uses waste Al2O3-SiC-C bricks as the main raw material. A nitriding process is used to obtain recycled material. Crushing and screening are employed to classify the recycled raw material and select a reasonable particle size distribution to achieve a close-packed gradation of the billet. Utilizing an activated sintering mechanism, high-melting-point zirconium materials and composite additives are added, and the amount added is controlled. By selecting appropriate process routes and parameters, a recycled aluminum silicon carbide carbon brick with high hot strength, excellent thermal shock stability, and resistance to penetration erosion is prepared. Compared with traditional processes, the cost can be reduced by about 30%, achieving resource recycling and significantly saving high-quality refractory raw materials. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following examples are intended to illustrate the present invention and not to further limit the present invention. 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.

[0034] In the embodiments, the particle size of zirconium corundum is 1-0.088 mm; the particle size of zirconium mullite fine powder is ≤0.088 mm; the C content in graphite is ≥94 wt%, and the particle size is ≤0.088 mm; the SiC content in silicon carbide is ≥96 wt%, and the particle size is ≤0.088 mm; the particle size of both metallic silicon powder and aluminum powder is 0-180 mesh; the composite rare earth oxide is a composite of yttrium oxide and lanthanum oxide in a mass ratio of 1:1.5; metallic silicon powder and aluminum powder are composite antioxidants, and are mixed in a mass ratio of 2:1; the binder is thermosetting phenolic resin and aluminum dihydrogen phosphate powder, and the mass ratio of thermosetting phenolic resin and aluminum dihydrogen phosphate powder is 1:1.5.

[0035] Example 1

[0036] A method for preparing refractory materials for molten iron pretreatment containers using low-rank solid waste includes the following steps:

[0037] Step 1: Recycle waste aluminum silicon carbide carbon bricks and remove the residual steel, residual iron, residue and permeated altered layer adhering to their surface by hammering and mechanical cutting.

[0038] Step 2: Put the aluminum silicon carbide carbon brick waste into a jaw crusher for crushing and processing into 8-0mm recycled material particles. During the crushing process, the crushed recycled material particles are magnetically separated to remove iron.

[0039] Step 3: Place the recycled material particles into a nitriding furnace and nitrid them at 1150℃ for 10 hours. After nitriding, the recycled material is then rolled and shaped by a roller mill and screened to obtain recycled aggregates of 8-5mm, 5-3mm, 3-1mm, and 1-0.088mm and recycled fine powder of less than 0.088mm.

[0040] Step 4: According to the weighed original material weight, put 55 parts of recycled aggregate, 5 parts of pyrophyllite, 3 parts of zirconium corundum, and 8 parts of silicon carbide into the mixer and mix for 5 minutes. Add 75% of the total amount of binder and mix for 6 minutes. Then add 5 parts of graphite and mix for 8 minutes. Finally, add 5 parts of recycled fine powder, 3 parts of zirconium mullite fine powder, 2 parts of metallic silicon powder, 1 part of aluminum powder, 1 part of composite rare earth oxide, and 0.5 parts of aluminum diboride powder and mix for 35 minutes. Then add 25% of the total amount of binder and mix for 15 minutes. Discharge the material. The total amount of binder added is 3.5% of the total weight of the original material.

[0041] Step 5: Press the mixed clay material into standard bricks of 230×114×65mm on an 800t friction brick press. After the standard bricks are naturally dried for 12 hours, they are dried in a tunnel kiln at 200℃ for 24 hours to produce aluminum silicon carbide carbon recycled brick products.

[0042] Of these, recycled aggregate with a particle size of 8-5mm accounts for 30% of the total weight of recycled aggregate, recycled aggregate with a particle size of 5-3mm accounts for 40% of the total weight of recycled aggregate, recycled aggregate with a particle size of 3-1mm accounts for 10% of the total weight of recycled aggregate, and recycled aggregate with a particle size of 1-0.088mm accounts for 10% of the total weight of recycled aggregate; the amount of recycled fine powder added accounts for 10% of the total weight of recycled aggregate.

[0043] The recycled material contains 62.42 wt% Al2O3, 9.19 wt% SiO2, and 11.4 wt% C.

[0044] The properties of the recycled material after nitriding treatment are: apparent porosity of 8.01%, bulk density of 3.02 g / cm³, and water absorption rate of 2.85%.

[0045] Example 2

[0046] A method for preparing refractory materials for molten iron pretreatment containers using low-rank solid waste includes the following steps:

[0047] Step 1: Recycle waste aluminum silicon carbide carbon bricks and remove the residual steel, residual iron, residue and permeated altered layer adhering to their surface by hammering and mechanical cutting.

[0048] Step 2: Put the aluminum silicon carbide carbon brick waste into a jaw crusher for crushing and processing into 8-0mm recycled material particles. During the crushing process, the crushed recycled material particles are magnetically separated to remove iron.

[0049] Step 3: Place the recycled material particles into a nitriding furnace and nitrid at 1250℃ for 8 hours. After nitriding, the recycled material is then rolled and shaped by a roller mill and screened to obtain recycled aggregates of 8-5mm, 5-3mm, 3-1mm, and 1-0.088mm and recycled fine powder of less than 0.088mm.

[0050] Step 4: According to the weighed proportions, add 65 parts of recycled aggregate, 6 parts of pyrophyllite, 5 parts of zirconium corundum, and 9 parts of silicon carbide into the mixing mill and mix for 8 minutes. Add 75% of the total amount of binder and mix for 5 minutes. Then add 6 parts of graphite and mix for 7 minutes. Finally, add 8 parts of recycled fine powder, 4 parts of zirconium mullite fine powder, 3 parts of metallic silicon powder, 1.5 parts of aluminum powder, 1.5 parts of composite rare earth oxide, and 1 part of zirconium diboride powder and mix for 37 minutes. Then add 25% of the total amount of binder and mix for 20 minutes. Discharge the material. The total amount of binder added is 4% of the total weight of the original materials.

[0051] Step 5: Press the mixed clay material into standard bricks of 230×114×65mm on an 800t friction brick press. After the standard bricks are naturally dried for 12 hours, they are dried in a tunnel kiln at 260℃ for 16 hours to produce aluminum silicon carbide carbon recycled brick products.

[0052] Of these, recycled aggregate with a particle size of 8-5mm accounts for 25% of the total weight of recycled aggregate, recycled aggregate with a particle size of 5-3mm accounts for 30% of the total weight of recycled aggregate, recycled aggregate with a particle size of 3-1mm accounts for 15% of the total weight of recycled aggregate, and recycled aggregate with a particle size of 1-0.088mm accounts for 5% of the total weight of recycled aggregate; the amount of recycled fine powder added accounts for 25% of the total weight of recycled aggregate.

[0053] The recycled material contains 61.91 wt% Al2O3, 9.47 wt% SiO2, and 8.06 wt% C.

[0054] The parameters of the recycled material particles after nitriding treatment are: apparent porosity of 8.39%, bulk density of 3.01 g / cm³, and water absorption rate of 2.99%.

[0055] Example 3

[0056] A method for preparing refractory materials for molten iron pretreatment containers using low-rank solid waste includes the following steps:

[0057] Step 1: Recycle waste aluminum silicon carbide carbon bricks and remove the residual steel, residual iron, residue and permeated altered layer adhering to their surface by hammering and mechanical cutting.

[0058] Step 2: Put the aluminum silicon carbide carbon brick waste into a jaw crusher for crushing and processing into 8-0mm recycled material particles. During the crushing process, the crushed recycled material particles are magnetically separated to remove iron.

[0059] Step 3: Place the recycled material particles into a nitriding furnace and nitrid at 1350℃ for 5 hours. After nitriding, the recycled material is then rolled and shaped by a roller mill and screened to obtain recycled aggregates of 8-5mm, 5-3mm, 3-1mm, and 1-0.088mm and recycled fine powder of less than 0.088mm.

[0060] Step 4: According to the weighed proportions, add 75 parts of recycled aggregate, 8 parts of pyrophyllite, 8 parts of zirconium corundum, and 10 parts of silicon carbide into the mixing mill and mix for 7 minutes. Add 80% of the total amount of binder and mix for 8 minutes. Then add 8 parts of graphite and mix for 5 minutes. Finally, add 10 parts of recycled fine powder, 5 parts of zirconium mullite fine powder, 4 parts of metallic silicon powder, 2 parts of aluminum powder, 2 parts of composite rare earth oxide, and 2 parts of titanium diboride and mix for 40 minutes. Then add 20% of the total amount of binder and mix for 18 minutes. Discharge the material. The total amount of binder added is 5% of the total weight of the original materials.

[0061] Step 5: Press the mixed clay material into standard bricks of 230×114×65mm on an 800t friction brick press. After the standard bricks are naturally dried for 12 hours, they are dried in a tunnel kiln at 300℃ for 12 hours to produce aluminum silicon carbide carbon recycled brick products.

[0062] Of these, recycled aggregate with a particle size of 8-5mm accounts for 20% of the total weight of recycled aggregate, recycled aggregate with a particle size of 5-3mm accounts for 25% of the total weight of recycled aggregate, recycled aggregate with a particle size of 3-1mm accounts for 12% of the total weight of recycled aggregate, and recycled aggregate with a particle size of 1-0.088mm accounts for 8% of the total weight of recycled aggregate; the amount of recycled fine powder added accounts for 35% of the total weight of recycled aggregate.

[0063] The recycled material contains 65 wt% Al2O3, 8.51 wt% SiO2, and 8.16 wt% C.

[0064] The parameters of the recycled material particles after nitriding treatment are: apparent porosity of 8.38%, bulk density of 3.01 g / cm³, and water absorption rate of 2.78%.

[0065] In the production of aluminum silicon carbide carbon recycled bricks according to this invention, when using a roller mill to crush the recycled material, as the crushing time increases, it is possible to obtain recyclable raw materials with low porosity. The crushing time is preferably 10-20 minutes. The apparent porosity of the 8-0 mm aggregate is as high as 10.6%. After crushing and grading, the apparent porosity of the 5-3 mm particles is 8.29%, and the apparent porosity of the 3-1 mm particles is 8.18%. The bulk density is 2.92 g / cm³. 3 Increased to 3.01 g / cm³ 3 .

[0066] Compared with virgin bricks, recycled bricks have higher bulk density and room temperature compressive strength, lower apparent porosity, and better high-temperature flexural strength, oxidation resistance, and slag resistance. The performance indicators of the samples from Examples 1-3 after testing according to relevant standards are shown in the table below:

[0067]

[0068] This invention uses nitrided recycled materials, and grades the recycled raw materials through crushing and screening to select a reasonable particle size distribution so that the billet achieves a close-packed size distribution. High-melting-point zirconium materials, composite additives and other raw materials are added, which greatly improves the compressive strength, thermal shock resistance and slag erosion resistance of the finished bricks. Its performance is superior to that of the original bricks. It can be used as working lining bricks in molten iron pretreatment containers, which can improve its service life, reduce costs and improve the recycling rate of low-level solid waste.

Claims

1. A method for producing a refractory material for a molten iron pretreatment vessel using low-rank solid waste, characterized by, The method comprises the following steps: Step one, recycling waste aluminum silicon carbide carbon brick, using iron hammer chisel and mechanical cutting method to remove the residual steel, residual iron, residual slag and permeated metamorphic layer adhered to the surface thereof; Step two, putting the aluminum silicon carbide carbon brick waste into a jaw crusher for crushing treatment, crushing into 0-8mm regenerated material particles, and performing magnetic separation on the crushed regenerated material particles during the crushing process; Step three, putting the regenerated material particles into a nitriding furnace, and performing nitriding treatment at 1150-1350℃ for 5-10 hours, then performing roller rolling and shaping on the regenerated material after the nitriding treatment, and performing screening treatment to obtain 5-8mm, 3-5mm, 1-3mm and 0.088-1mm regenerated material aggregates and 0.088mm or below regenerated material fine powder; The regenerated material aggregates with a particle size of 5-8mm account for 20-30% of the total weight of the regenerated material, the regenerated material aggregates with a particle size of 3-5mm account for 20-40% of the total weight of the regenerated material, the regenerated material aggregates with a particle size of 1-3mm account for 10-15% of the total weight of the regenerated material, the regenerated material aggregates with a particle size of 0.088-1mm account for 5-10% of the total weight of the regenerated material, and the added amount of the regenerated material fine powder accounts for 10-35% of the total weight of the regenerated material; the Al2O3 content in the regenerated material is 57-66wt%, the SiO2 content is 8-11wt%, and the C content is 8-13wt%; Step four, putting 55-75 parts of the regenerated material aggregates, 5-8 parts of the leaf talc, 3-8 parts of the zircon corundum, 8-10 parts of the silicon carbide into a mixing roller, mixing for 5-8min, adding 75-80% of the total amount of the binding agent, mixing for 5-8min, then adding 5-8 parts of the graphite, mixing for 5-8min, finally adding 5-10 parts of the regenerated material fine powder, 3-5 parts of the zircon mullite fine powder, 2-4 parts of the metal silicon powder, 1-2 parts of the aluminum powder, 1-2 parts of the composite rare earth oxide and 0.5-2 parts of the reinforcing agent, mixing for 35-40min, then adding 20-25% of the total amount of the binding agent, mixing for 15-20min, and discharging; the total amount of the added binding agent is 2-5% of the total weight of the original material; the composite rare earth oxide is a composite of yttrium oxide and lanthanum oxide at a mass ratio of 1:1.5; the reinforcing agent is at least one of aluminum diboride powder, zirconium diboride or titanium diboride; Step five, putting the mixed mud material into a 800t brick press to press into 230x114x65mm standard bricks, naturally drying the standard bricks for 12h, and then baking in a tunnel kiln at 200-300℃ for 12-24h to obtain aluminum silicon carbide carbon regenerated brick products.

2. The method for preparing a refractory material for a pretreatment vessel of molten iron using low-rank solid waste according to claim 1, characterized by: The particle size of the zircon corundum is 0.088-1mm; the particle size of the zircon mullite fine powder is ≤0.088mm.

3. The method for preparing a refractory material for a pretreatment vessel of molten iron using low-rank solid waste according to claim 1, characterized by: The C content in the graphite is ≥94wt%, and the particle size is ≤0.088mm; the SiC content in the silicon carbide is ≥96wt%, and the particle size is ≤0.088mm.

4. The method for preparing a refractory material for a pretreatment vessel of molten iron using low-rank solid waste according to claim 1, characterized by: The metal silicon powder and the aluminum powder are composite antioxidants, and the mass ratio of the metal silicon powder to the aluminum powder is 2:1; the particle size of the metal silicon powder and the aluminum powder is 180 mesh.

5. The method of claim 1, wherein the method is characterized by: The binder is thermosetting phenolic resin and aluminum dihydrogen phosphate powder, and the mass ratio of the thermosetting phenolic resin and the aluminum dihydrogen phosphate powder is 1:1.

5.

6. The method of claim 1, wherein the method of preparing a refractory material for a pretreatment vessel of molten iron using low-rank solid waste is characterized by: After the nitriding treatment, the indexes of the regenerated material are as follows: the apparent porosity is 7.6-8.5%, the bulk density is 2.95-3.1 g / cm3, and the water absorption is 2.7-3.1%. ​

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