阅读说明：本技术 一种含有稀土氧化物的碳化硅复合耐火制品 (Silicon carbide composite refractory product containing rare earth oxide ) 是由 李红霞 孙红刚 夏淼 司瑶晨 赵世贤 杜一昊 尚心莲 亢一娜 于 2020-06-22 设计创作，主要内容包括：本发明属于耐火材料技术领域,提出一种含有稀土氧化物的碳化硅复合耐火制品。提出的一种含有稀土氧化物的碳化硅复合耐火制品包括骨料、基质；骨料为碳化硅颗粒,基质为镁铝尖晶石细粉或六铝酸钙细粉中的一种和稀土氧化物细粉,稀土氧化物细粉的含量占原料总质量的1%～5%,镁铝尖晶石细粉或六铝酸钙细粉的含量占原料总质量的20%～45%；碳化硅颗粒的含量占原料总质量的50%～75%；骨料、基质与树脂结合剂均匀混合后,压制成生坯,生坯经干燥后高温烧成处理得到以钇铝石榴石或镁基六铝酸为稀土结合相,碳化硅和镁铝尖晶石或六铝酸钙为主要晶相的碳化硅复合耐火制品。本发明具有抗碱性熔渣侵蚀性和抗熔渣渗透性优异的特点。(The invention belongs to the technical field of refractory materials, and provides a silicon carbide composite refractory product containing rare earth oxide. The silicon carbide composite refractory product containing the rare earth oxide comprises aggregate and a matrix; the aggregate is silicon carbide particles, the matrix is one of magnesia-alumina spinel fine powder or calcium hexaluminate fine powder and rare earth oxide fine powder, the content of the rare earth oxide fine powder accounts for 1-5% of the total mass of the raw materials, and the content of the magnesia-alumina spinel fine powder or the calcium hexaluminate fine powder accounts for 20-45% of the total mass of the raw materials; the content of the silicon carbide particles accounts for 50-75% of the total mass of the raw materials; the aggregate, the matrix and the resin binder are uniformly mixed and then pressed into a green body, the green body is dried and then is sintered at high temperature to obtain the silicon carbide composite refractory product which takes yttrium aluminum garnet or magnesium-based hexaluminate as a rare earth bonding phase and takes silicon carbide and magnesium aluminate spinel or calcium hexaluminate as main crystal phases. The invention has the characteristics of excellent alkaline slag corrosion resistance and slag permeability resistance.)

1. A silicon carbide composite refractory product containing rare earth oxide is characterized in that: the raw materials of the silicon carbide composite refractory product containing the rare earth oxide comprise aggregate and matrix; the aggregate is silicon carbide particles, and the matrix is mainly one of magnesia-alumina spinel fine powder or calcium hexaluminate fine powder; the matrix also contains rare earth oxide fine powder, the content of the rare earth oxide fine powder accounts for 1% -5% of the total mass of the raw materials, and the rare earth oxide fine powder is one of yttrium oxide fine powder or lanthanum oxide fine powder; the content of the magnesia-alumina spinel fine powder or the calcium hexaluminate fine powder accounts for 20 to 45 percent of the total mass of the raw materials; the content of the silicon carbide particles accounts for 50-75% of the total mass of the raw materials; the aggregate, the matrix and the resin binder are uniformly mixed and then pressed into green bodies with certain sizes and shapes, the green bodies are dried and then subjected to high-temperature firing treatment at 1300-1650 ℃, and in the high-temperature firing treatment process, yttrium oxide fine powder is subjected to high-temperature reaction to obtain a raw material with the molecular formula of Y₃Al₅O₁₂The yttrium aluminum garnet and the lanthanum oxide fine powder react at high temperature to generate a compound with the molecular formula of LaMgAl₁₁O₁₉Magnesium-based lanthanum hexaaluminate; the yttrium aluminum garnet or magnesium-based lanthanum hexaaluminate is used as a rare earth bonding phase of the silicon carbide composite refractory product and forms the silicon carbide composite refractory product together with silicon carbide and magnesium aluminum spinel or calcium hexaaluminate which are used as main crystal phases; the silicon carbide composite refractory product containing the rare earth oxide has the apparent porosity of 10-18%, the normal-temperature flexural strength of 15-40 MPa and the high-temperature flexural strength of 10-30 MPa at 1400 ℃.

2. The rare earth oxide-containing silicon carbide composite refractory article of claim 1, wherein: the fine powder of yttrium oxide, w (Y)₂O₃) Not less than 99% and the granularity is not more than 60 μm.

3. The rare earth oxide-containing silicon carbide composite refractory article of claim 1, wherein: the lanthanum oxide fine powder has the purity of w (La)₂O₃) Not less than 99% and the granularity is not more than 60 μm.

4. The rare earth oxide-containing silicon carbide composite refractory article of claim 1, wherein: the silicon carbide particles are an electric melting raw material with the particle size of more than 0.1mm and less than or equal to 5mm and the purity w (SiC) of more than or equal to 97 percent.

5. The rare earth oxide-containing silicon carbide composite refractory article of claim 1, wherein: the magnesia-alumina spinel fine powder is w (Al)₂O₃And + MgO) is not less than 99.0 percent, the content of spinel phase is not less than 95 percent by X-ray diffraction analysis, and the granularity is 10-90 mu m.

6. The rare earth oxide-containing silicon carbide composite refractory article of claim 1, wherein: the calcium hexaluminate fine powder is w (Al)₂O3+ CaO) is not less than 99.0 percent, the content of calcium hexaluminate phase is not less than 90 percent by X-ray diffraction analysis, and the granularity is 10-90 mu m.

Technical Field

The invention belongs to the technical field of refractory materials, and mainly relates to a silicon carbide composite refractory product containing rare earth oxide.

Background

The energy pattern of rich coal, poor oil and less gas in China determines that the development direction of energy in China must be focused on deep processing of coal; the low-rank coal (including brown coal, long flame coal, weakly caking coal and non-caking coal) at the present stage accounts for more than 50% of the coal reserves in China and the current coal yield, so the clean and efficient utilization of the low-rank coal must be promoted based on double considerations of economy and environmental protection; at present, a coal water slurry gasification furnace becomes mainstream equipment for coal gasification, but the severe working environment (high temperature (1300-1500 ℃), high pressure (2.0-8.7 MPa) and strong reducing atmosphere (main components of CO and H2)) and the erosion of coal slag (CaO, FeOx, Al2O3, MgO, TiO2, K2O, Na2O and the like) and the physical scouring of high-temperature gas put higher requirements on the erosion resistance, high-temperature mechanical strength and stability of lining refractory materials; the most widely used lining material in the coal water slurry gas furnace at the present stage is pure oxide brick (high chrome brick) of Cr2O3-Al2O3-ZrO2 system with Cr2O3 more than 75 wt%; but the chromium resource is limited, the mining cost is high, the environmental pollution is large, and particularly, the chromium resource can react with certain substances in the coal slag to generate Cr6+ ions in the service process, so that potential environmental protection hazards exist.

Research shows that the composite refractory material prepared by selecting oxides and non-oxides has high-temperature performance which is not possessed by a pure oxide material or a pure non-oxide material, can be used as a potential environment-friendly refractory material for coal gasification, and promotes the progress of realizing chromium-free of the refractory material of the coal water slurry gasification furnace; the application documents CN201711187000.7\ CN201711187027.6 disclose a silicon carbide-calcium hexaluminate composite refractory material and a silicon carbide-magnesium aluminate spinel composite refractory material respectively, wherein both silicon carbide and a bonding agent are uniformly mixed and then added with magnesium aluminate spinel \ calcium hexaluminate to be mixed, pressed and sintered, but because the self-sintering property of silicon carbide is poor, certain sintering can be achieved at a very high temperature above 2200 ℃, and the calcium and the magnesium aluminate spinel have high melting points (1830 ℃, 2135 ℃), so that the sintering temperatures of the silicon carbide and the calcium hexaluminate must reach above 1800 ℃.

To prevent oxidation of the silicon carbide, such composites are typically sintered under a protective atmosphere; earlier exploration finds that the silicon carbide-calcium hexaluminate or silicon carbide-magnesia-alumina spinel composite material still needs higher temperature even being sintered in a reducing atmosphere, when the sintering condition is 1600 ℃ carbon burying, the normal temperature flexural strength of the silicon carbide-calcium hexaluminate or silicon carbide-magnesia-alumina spinel composite material is less than 10 MPa, the high temperature flexural strength is more less than 5MPa, and the lower mechanical strength is extremely unfavorable for the material to resist the high-speed erosion of molten slag in the use process; the main reason why the mechanical strength of such composite materials is analyzed is because the way in which silicon carbide and oxide bond is different. Silicon carbide is combined by covalent bonds, and calcium hexaluminate/magnesia-alumina spinel are oxides combined by ionic bonds, which means that the calcium hexaluminate/magnesia-alumina spinel and the oxides are not wetted with each other and are difficult to form effective chemical combination.

Through the discussion above, in order to promote the chromium-free of the refractory material for the coal water slurry gasification furnace, how to improve the strength of the silicon carbide composite material and optimize the slag resistance of the composite material, and also consider the high-temperature slag corrosion resistance and the melt erosion resistance of the composite material, is a technical problem.

Disclosure of Invention

The invention aims to provide a silicon carbide composite refractory product containing rare earth oxide, which can improve the strength of a silicon carbide composite material, optimize the slag resistance of the composite material and give consideration to the high-temperature slag corrosion resistance and the melt erosion resistance of the composite material.

The invention adopts the following technical scheme for achieving the purpose:

the raw materials of the silicon carbide composite refractory product containing the rare earth oxide comprise aggregate and matrix; the aggregate is silicon carbide particles, and the matrix is mainly one of magnesia-alumina spinel fine powder or calcium hexaluminate fine powder; the matrix also contains rare earth oxide fine powder, the content of the rare earth oxide fine powder accounts for 1% -5% of the total mass of the raw materials, and the rare earth oxide fine powder is one of yttrium oxide fine powder or lanthanum oxide fine powder; the content of the magnesia-alumina spinel fine powder or the calcium hexaluminate fine powder accounts for 20 to 45 percent of the total mass of the raw materials; the silicon carbide particles account for 50-75% of the total mass of the raw materials; the aggregate, the matrix and the resin binder are uniformly mixed and then pressed into green bodies with certain sizes and shapes, the green bodies are dried and then subjected to high-temperature firing treatment at 1300-1650 ℃, and in the high-temperature firing treatment process, yttrium oxide fine powder is subjected to high-temperature reaction to obtain a raw material with the molecular formula of Y₃Al₅O₁₂The yttrium aluminum garnet and the lanthanum oxide fine powder react at high temperature to generate a compound with the molecular formula of LaMgAl₁₁O₁₉Magnesium-based lanthanum hexaaluminate; the yttrium aluminum garnet or magnesium-based lanthanum hexaaluminate is used as a rare earth bonding phase of the silicon carbide composite refractory product and forms the silicon carbide composite refractory product together with silicon carbide and magnesium aluminum spinel or calcium hexaaluminate which are used as main crystal phases; the apparent porosity of the silicon carbide composite refractory product is 10-18%, the normal-temperature flexural strength is 15-40 MPa, and the high-temperature flexural strength at 1400 ℃ is 10-30 MPa.

The fine powder of yttrium oxide, w (Y)₂O₃) More than or equal to 99 percent and the particle size is less than or equal to 60 mu m; requirement w (Y)₂O₃) Not less than 99% because of impurities (Fe) if the purity is not high₂O₃、Na₂O、K₂O, etc.) to generate a low-melting-point phase, which influences the overall anti-cinder erosion performance and high-temperature mechanical property of the material; the yttrium oxide is required to have smaller granularity because the rare earth bonding phase needs to be generated and uniformly distributed, so the yttrium oxide is required to be uniformly mixed with magnesia-alumina spinel or calcium hexaaluminate and then distributed among silicon carbide particles; the yttrium oxide is introduced into the body through the addition of MgO-Al₂O₃-Y₂O₃Presence of Y in the system₃Al₅O₁₂-MgAl₂O₄Eutectic phase, rare earth bound phase Y₃Al₅O₁₂Known as yttrium aluminum garnet, containing 8Y atoms per unit cell₃Al₅O₁₂A molecule; a1³⁺Ions have two different occupation sites which respectively occupy the central point of the tetrahedron/octahedron, and O2-ions also have two occupation sites which are the vertex angles of the tetrahedron/octahedron; the tetrahedron is connected with the vertex angle of the octahedron to form a certain number of gaps of the dodecahedron; y3+ ions are distributed at the center of the dodecahedrons; just because of the specific structure and composition of YAG, the YAG has excellent high-temperature strength and stability; particularly, the yttrium aluminum garnet has the expansion coefficient similar to that of magnesium aluminum spinel, is an oxide with the lowest high-temperature creep rate, and can remarkably promote the sintering of the magnesium aluminum spinel and calcium hexaluminate, so that the yttrium aluminum garnet can be used as an excellent rare earth binding phase.

The lanthanum oxide fine powder has the purity of w (La)₂O₃) Not less than 99% and the granularity is not more than 60 μm. Requirement w (La)₂O₃) Not less than 99 percent, otherwise, the content of impurities (Fe) can be reduced₂O₃、Na₂O、K₂O, etc.) to cause the generation of low-melting-point phase under high-temperature state, thereby greatly influencing the high-temperature mechanical strength, stability and slag resistance of the material; the reason why the particle size of lanthanum oxide is required to be less than or equal to 60 μm is that rare earth oxide must be distributed as uniformly as possible between aggregate and magnesia-alumina spinel or calcium hexaaluminate in order to improve the high-temperature strength of the material; the lanthanum oxide is introduced to generate rare earth bonding phase magnesium-based lanthanum hexaaluminate (LaMgAl) at high temperature₁₁O₁₉) The material has a specific structure, and four aluminum spinel layers are embedded on the layer surface of the material, so that the structure can obviously reduce oxygen ion diffusion, and the oxidation resistance of a material bottom layer and a substrate is improved; in addition, the magnesium-based lanthanum hexaaluminate has low heat conductivity coefficient and high thermal stability in a high-temperature environment; particularly, the special layered structure can ensure that the composite material keeps higher volume stability in sintering; in particular the plate-like crystal structure thereof, can also be determined by the materialThe mechanical strength of the composite material is improved by pulling out crystal grains, hindering crack propagation and prolonging the path of crack propagation; therefore, magnesium-based lanthanum hexaaluminate is considered to be an excellent high-temperature reinforcing phase.

The silicon carbide particles are an electric melting raw material with the particle size of more than 0.1mm and less than or equal to 5mm and the purity w (SiC) of more than or equal to 97 percent; the reason that the silicon carbide is selected for preparation by an electric melting method is that the silicon carbide material prepared by the method has good crystal integrity and higher density and erosion resistance; the purity w (SiC) is required to be more than or equal to 97 percent, so that the generation of low-melting solid solution due to the existence of impurities such as silicon dioxide and the like is avoided, and the overall performance of the material is not damaged; the granularity of SiC particles with the same granularity of 0.1-5 mm is required to be selected to meet the forming requirement and the requirements of density and bonding performance.

The magnesia-alumina spinel fine powder is w (Al)₂O₃+ MgO) is more than or equal to 99.0 percent, the content of spinel phase is more than or equal to 95 percent by X-ray diffraction analysis, and the granularity is 10-90 mu m; the magnesium aluminate spinel is Al₂O₃-the most stable compound under the binary system MgO; the magnesium aluminate spinel can be divided into magnesium-rich spinel and aluminum-rich spinel according to the relative content of aluminum oxide and magnesium oxide in the magnesium aluminate spinel; based on the service environment of the composite material and the special requirements of excellent slag resistance, Al₂O₃The total mass fraction of + MgO must be greater than 99.0%; the aim of requiring the spinel to have the granularity range of 10-90 mu m is to realize the full mixing of the spinel and the rare earth oxide fine powder, thereby ensuring the uniform distribution of a rare earth binding phase and the silicon carbide aggregate, and further realizing the optimization of the binding strength and the slag resistance of the spinel. If the particle size of the magnesia-alumina spinel is unreasonable, the defects of poor sintering performance of the prepared product, low compactness of the product, reduced slag resistance and the like can be caused.

The calcium hexaluminate fine powder is w (Al)₂O3+ CaO) is not less than 99.0 percent, the content of calcium hexaluminate phase is not less than 90 percent by X-ray diffraction analysis, and the granularity is 10-90 mu m; calcium hexaluminate (CaAl)₁₂O₁₉) Is CaO-Al₂O₃Highest Al in binary system₂O₃Content of calcium aluminate phaseExcellent erosion resistance; based on the service environment of the composite material and the special requirements of excellent slag resistance, Al₂O₃The total mass fraction of + CaO must be greater than 99.0%; the purpose of requiring the particle size range of the calcium hexaluminate to be 10-90 mu m is to realize the full contact and mixing of the calcium hexaluminate and the rare earth oxide, so that the uniform distribution of a rare earth binding phase and the silicon carbide aggregate are ensured, and the optimization of the binding strength and the slag resistance of the calcium hexaluminate is further realized. If the particle size of the calcium hexaluminate is unreasonable, the defects of poor sintering performance, low product density, reduced slag resistance and the like of the prepared product can be caused.

The silicon carbide refractory material product containing the rare earth oxide is mainly applied to a coal gasification high-temperature service environment with a reducing atmosphere at 1300-1500 ℃, and under the condition, coal slag seriously erodes the refractory material and seriously physically erodes the refractory material at high temperature; the silicon carbide composite refractory product of the rare earth yttrium aluminum garnet or magnesium-based lanthanum hexaaluminate combined phase formed by the introduced rare earth oxide fine powder has the characteristics of high chemical purity, low glass phase content, excellent normal/high temperature mechanical strength, high temperature slag corrosion resistance, high temperature abrasion resistance and the like, and can obviously improve the performance of the composite refractory product; in the presence of MgO-Al₂O₃-Y₂O₃Presence of Y in the system₃Al₅O₁₂-MgAl₂O₄Eutectic phase, Y₃Al₅O₁₂The magnesium aluminate spinel has a specific dodecahedron structure, so that the magnesium aluminate spinel has excellent physical, chemical and mechanical properties, has the lowest high-temperature creep rate in all oxides, particularly has a thermal expansion coefficient close to that of magnesium aluminate spinel, and can remarkably promote the sintering densification of the magnesium aluminate spinel; the yttrium aluminum garnet introduced in the silicon carbide sintering process can obviously reduce the sintering temperature and refine the microstructure of the yttrium aluminum garnet; because the magnesium-based lanthanum hexaaluminate is of a mixed structure of body-centered cubic and close-packed hexagonal, four aluminum spinel layers are formed on the lanthanum aluminate layer, so that crystal grains are in a plate-shaped structure and are randomly arranged, and the specific structure is favorable for balancing the quantity of micro pores in the material, so that the material has lower heat conductivity; meanwhile, the diffusion of oxygen atoms can be inhibited to a greater extent, so that the oxidation process of the bottom layer and the matrix is slowed down; specially for treating diabetesThe rare earth lanthanum oxide fine powder introduced into the silicon carbide composite material can increase the fracture toughness by utilizing the pulling-out of lanthanum hexaaluminate crystal grains, the obstruction of crack propagation or the extension of crack propagation paths and the transgranular fracture of flaky crystal grains, thereby improving the bonding strength and the mechanical property of the composite material; therefore, the introduction of the rare earth yttrium oxide fine powder can obviously improve the bonding strength of the silicon carbide composite refractory material product; the silicon carbide composite refractory product of the rare earth yttrium aluminum garnet or magnesium-based lanthanum hexaaluminate combined phase formed by the introduced rare earth oxide fine powder has the characteristics of high chemical purity, low glass phase content, excellent normal/high temperature mechanical strength, high temperature slag corrosion resistance, high temperature abrasion resistance and the like, and can obviously improve the performance of the composite refractory product; compared with the prior art, the product provided by the invention obviously improves the wettability between silicon carbide and oxide, improves the bonding strength of the silicon carbide composite refractory product, does not contain chromium oxide, is low in price, is green and environment-friendly, has the characteristics of excellent alkaline slag corrosion resistance and slag permeability resistance and the like, and is an environment-friendly refractory material with excellent alkaline slag corrosion resistance in a high-temperature and reducing atmosphere.

Detailed Description

The invention is illustrated by the examples given, but is not to be construed as being in any way limited thereto.