ã€China Aluminum Industry Network】1. Misunderstandings in the use of aluminum silicate fiber materials:
The identification of the temperature parameters is very confusing: the use of temperature, higher temperature, temperature limit, classification temperature, long-term working temperature and other different signs. In fact, the use temperature of aluminum silicate fiber material is not only related to the chemical composition of the material, but also closely related to the use of atmosphere, fuel and environmental conditions. For example: if the same material maintains its basic performance in the standard atmosphere of the experimental resistance furnace, the higher temperature is 1260°C, then in the medium and strong reducing atmosphere, the higher operating temperature will decrease by 100-180°C, in the heavy oil environment. Because of sulfur, phosphorus and other elements of aluminum silicate fiber erosion temperature will be lower. The temperature of use should be determined by the designer, user, and technician of the fiber manufacturer, based on the use of fuel, the environment, and the heating system to determine the operating temperature and the selected materials.
2. Misunderstandings in the chemical composition of aluminum silicate fiber materials:
In the application of aluminum silicate fiber material for many years, it is often found that the actual temperature does not exceed the use temperature range of the material, but the fiber material has serious shrinkage and powdering. After testing the chemical composition, Al2O3 meets product requirements, while SiO2 is low, and Fe2O3, CaO, MgO, Na2O, K2O and other impurities are seriously exceeded. Such impurities are low-melting oxides, and excessive amounts of low-melting oxides will reduce the eutectic point of the aluminum silicate fiber material. If the content of impurities other than Al2O3 and SiO2 reaches 3.5% or more, the ratio is controlled within 1%, and the practical use temperature of the aluminum silicate fiber material will be reduced by nearly 100C. Therefore, when we use aluminum silicate fiber materials, we must not only test the composition of Al2O3, but also strictly control the content of other impurities.
3, the misunderstanding of the bulk density of aluminum silicate fiber materials:
The fiber itself consists of Al2O3 and SiO2. Its heat capacity is basically the same as that of firebrick products, but fiber products such as felts and blankets, due to the use of fiber interweaving methods, form an empty, loose unit structure that reduces the bulk of the product and changes the thermal conductivity. performance. The thermal conductivity of fiber products with a bulk density of 150-250kg/m3 is about 20% of the thermal conductivity of a heavy brick of 2070Kg/m3; it is about 37-40% of the thermal conductivity of light bricks of 1300Kg/m3. The bulk density of the fiber products is in the range of 150-250 kg/m3. As the bulk density increases, the thermal conductivity gradually decreases, and the heat loss thereof gradually decreases. However, as the bulk density increases, the structural performance of the air loosening unit also decreases. When the capacity is larger than 400 kg/m3, the thermal conductivity increases, and the heat storage loss also increases, and the overall energy saving performance decreases. So one-sided pursuit of too low or too high weight is not desirable.
4, the impact of aluminum silicate fiber material slag content:
The content of slag ball in the product is an important factor affecting the bulk density. The slag ball has a bulk density of 2800-3200 kg/m3, and the content of the slag ball in the fiber product is too much, which will reduce the comprehensive energy-saving performance and at the same time damage the interests of users. In foreign countries, the content of slag balls with a particle size of 0.25 mm is controlled at ≤ 5%. However, due to limitations in fiber manufacturing technology, the content of slag balls is controlled to ≤ 15%. That is, nearly 1/8 of the fiber products are slag balls, which are more than foreign. The content is twice as high. Our company adopts a new de-slagging process to ensure that the content of slag balls is controlled at ≤10% and reaches the industry-leading level. Therefore, in determining the bulk density of aluminum silicate fiber products, we must fully consider the content of the slag ball.
At present, the bottleneck and disadvantage of large scale development and manufacturing of isotropic Graphite in China still exist: the design and manufacture of large, special cold and other static presses have not kept up with it. (2) other facilities not perfect, such as the large and super large (1200 mm) Φ graphite impregnated, roasting, graphitization, purification processing, special machine tools machining must be perfect.
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