The main components of chromium corundum are Al2O3 and Cr2O3, which form a continuous solid solution. According to the Al2O3-Cr2O3 binary phase diagram, adding Cr2O3 to the Al2O3 single-phase material does not reduce the refractoriness of the material, but the refractoriness increases with the content of Cr2O3 The increase of the increase.
Adding Cr2O3 to the corundum material, as the temperature rises, Al2O3 and Cr2O3 gradually form a solid solution, so that the corundum particles and the matrix are tightly combined, and further form an annular solid solution zone on the surface of the corundum particles, making the material particles and particles at high temperatures Among them, the particles and fine powders are tightly combined, and the combined phase is aluminum-chromium solid solution phase, which has a high melting point and maintains the bonding strength even at high temperatures. Therefore, chromium corundum refractories have strong mechanical properties at room temperature and high temperature Mechanical properties.
Cr2O3 is a high-quality component of refractory materials, which can form high melting point compounds with various oxides. For example, Cr2O3 and Al2O3 can form a continuous solid solution, the melting point of this solid solution is above 2050℃; Cr2O3 and MgO/FeO form high melting point magnesia-chromium spinel/chromium iron spinel; Cr2O3 and Cu2O can form a melting point above 1600℃ The melting temperature of the eutectic formed by Cr2O3 and SiO2 reaches 1720℃; etc.
In addition, Cr2O3 can increase the viscosity of the slag, and the increase of the viscosity of the slag can slow down the infiltration rate of the slag into the refractory. In summary, Cr2O3 can improve the slag erosion resistance and spalling performance of refractories.
Application of chromium corundum
Because of its unique excellent properties, chromium corundum has been widely used in high-temperature fields with harsh environments, including non-ferrous metallurgy furnaces, glass furnaces, carbon black reactors, garbage incinerators, etc. At the beginning of the development of chromium corundum, it was more widely used, and it was also involved in the fields of cement and steel metallurgy. However, due to the strengthening of people’s awareness of environmental protection, the demand for chromium-free industry in high-temperature industries is getting higher and higher, and alternative products have been developed in many fields. However, chromium corundum still exists in some parts where the service environment is relatively harsh.
Because of its unique properties, chromium-containing refractories have been used well in non-ferrous metallurgical industry kilns. Although many scholars are now studying the non-chromium-free refractory materials in the field of non-ferrous metallurgy, so far, chromium-containing refractories have been used in the field of non-ferrous metallurgy. As a smelting furnace lining is still the mainstream. For example: Ausmelt refractories for copper smelting furnaces not only have to withstand the erosion of the melt (SiO2/FeO series slag, copper liquid, copper matte) and gas phase erosion, but also overcome the temperature caused by the regular replacement of the spray gun Fluctuations and harsh service environment. At this stage, apart from chromium-containing refractories, there is no better material to replace. In addition, zinc volatilization kilns, copper converters, coal gasification furnaces and carbon black reactors are also facing the same situation.
The corrosion resistance of aluminum-chromium refractories to molten glass is better than that of conventional corundum or aluminum-silicon refractories. Therefore, aluminum-chromium-based refractories are often used as lining materials in critical areas such as small furnaces in the regenerator, target walls, and molten pools that are severely corroded.
Aluminum chromium refractories are also commonly used in carbon black reactors, including: combustion section, throat section, reaction section, etc. Aluminum chromium refractories are used in the ultra-high temperature (1900℃) area of the carbon black reactor, the chemical attack area of reducing gases (C, CO, H2) and ash, and the area of frequent temperature fluctuations. Therefore, it is required that the aluminum-chromium refractories used in carbon black reactors should have the following characteristics: 1) high refractoriness, higher load softening temperature and lower high temperature creep rate; 2) stability under strong reducing atmosphere; 3 ) Strong resistance to molten ash erosion; 4) Higher high temperature strength and erosion resistance; 5) Good thermal shock resistance.
Among the refractories used for the lining of garbage melting incinerators (ash melting furnaces), refractories containing chromium oxide generally exhibit good corrosion resistance; when the combustion temperature is higher than 1250°C, chromium corundum products are used. The garbage melting incinerator generally has an oxidizing atmosphere, so C-SiC bricks and SiC bricks with poor oxidation resistance cannot be used, and Al2O3-Cr2O3 materials and MgO-Cr2O3 materials are preferred. Under normal circumstances, Al2O3-Cr2O3 material increases with the increase of alkalinity, the erosion rate increases, so it is mainly used in melting furnaces with relatively low alkalinity.
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