Mullite is mainly composed of aluminum oxide and silicon oxide. It is a general term for aluminosilicate minerals. It is a mineral formed by aluminosilicate under high temperature conditions. Mullite is also formed when aluminosilicate is artificially heated. In recent years, my country has continuously increased the clean utilization of coal resources. The fly ash produced by power plants also contains mullite phase, among which the mullite content in the fly ash of the pulverized coal furnace of Junggar Power Plant is about 40%. The chemical composition of mullite is 3Al2O3·2SiO2-2Al2O3·SiO2. From the perspective of the phase diagram, mullite is the only stable crystalline aluminosilicate in the binary phase diagram system. Its crystal structure is composed of silicon oxygen tetrahedron and aluminum oxygen tetrahedron arranged disorderly along the C axis to form a double chain, and the double chain is connected by aluminum oxygen octahedron. In its structure, the aluminum oxygen octahedron plays a skeleton support role in the whole structure. The two ordering modes of non-commensurate amplitude modulation give it stable energy, so mullite has very good chemical stability. At the same time, it has good properties such as high refractoriness, strong electrical insulation, resistance to chemical corrosion, good seismic resistance, high load softening temperature, and creep resistance. It is now widely used in many industrial fields such as metallurgy, chemical industry, petroleum, electric power, and national defense.
The refractory temperature of mullite refractory materials is relatively high. Generally speaking, the refractoriness of mullite refractory materials can reach above 1790℃. For example, the refractoriness of mullite bricks is usually above 1790℃, and the load softening starting temperature is between 1600 and 1700℃. Mullite castables are used in industrial kiln linings and are most suitable for use at a temperature of 1400℃. Mullite polylight insulation bricks are divided into JM-23, JM-26, JM-28, JM-30 and other models according to the use temperature, and the use temperature is between 1300℃ and 1550℃. The outer flame temperature of ordinary flames is generally around 500℃, and the temperature of ironmaking is generally around 1300-1500℃. In theory, mullite refractory bricks can withstand the test of molten iron for a certain period of time. According to the testing standards, the refractory temperature of mullite refractory bricks should be around 1200℃ - 1700℃. The refractory temperatures of different types and qualities of mullite refractory materials may vary, depending on factors such as their composition, manufacturing process and use environment.
Mullite brick is a high-alumina refractory material with mullite as the main crystal phase. Its refractory temperature is relatively high, usually above 1790℃. The load softening starting temperature is between 1600 and 1700℃, and the compressive strength at room temperature is between 80 and 100MPa. The refractory performance of mullite brick mainly depends on the content of alumina and the uniformity of the distribution of mullite phase and glass. For example, in some high-temperature industrial furnaces, such as hot blast furnaces and ceramic kilns, mullite bricks can withstand the test of high temperature environments and maintain good structural stability and refractory performance. The refractory temperatures of mullite bricks with different production processes and formulas may vary, but generally speaking, they all have excellent high temperature resistance.
Mullite castables are used in industrial furnace linings, and the most suitable temperature is generally around 1400℃. At medium and high temperatures, aluminum and silicon react to form mullite to act as a bond, and then secondary mullitization is used to improve and increase the flexibility of the castable. Mullite castables also have good thermal shock resistance and can withstand thermal stress at high temperatures. They also have high slag resistance and can resist erosion and infiltration of high-temperature slag. It has good fluidity and plasticity, is easy to construct and form, can shorten the construction cycle during the construction process, and improve production efficiency. While having high thermal stability, it also has good thermal insulation properties, which can improve the thermal efficiency of the furnace lining and reduce fuel energy consumption.
Mullite polylight insulation bricks are divided into JM-23, JM-26, JM-28, JM-30 and other models according to the use temperature. The use temperature of this type of product is usually between 1300℃ and 1550℃. Mullite polylight insulation bricks have the characteristics of low hot melt, low impurity content, high refractoriness, high hot compressive strength, low thermal conductivity, and significant energy saving effect. It is made of high-quality high-alumina bauxite clinker as the main raw material through a special process. It can directly contact the flame and plays an important role as a heat insulation material in industrial furnaces in the petroleum, chemical, ceramic and other industries.
The temperature of ordinary flames varies depending on the combustion materials. Generally, the outer flame, which is the highest temperature of the flame, is about 500°C. The temperature of ironmaking is relatively high. The iron in the blast furnace can be melted between 1100°C and 1200°C. The ironmaking plant needs a temperature of 2200-2350°C to smelt the iron. The highest temperature in the blast furnace is in the coke combustion area in front of the tuyere. This temperature can be expressed by the theoretical combustion temperature in front of the tuyere. The theoretical combustion temperature in front of the tuyere of China's blast furnace is controlled between 2250-2350°C.
The theoretical refractory temperature of mullite refractory bricks is around 1200℃-1700℃. For example, the temperature of ironmaking is generally around 1300-1500℃, and mullite refractory bricks can theoretically withstand the test of molten iron for a certain period of time, which fully demonstrates the excellent refractory performance of mullite refractory bricks. The high temperature performance of mullite refractory bricks is also closely related to its testing standards. The national standard GB/T 35845-2018 "Mullite Insulating Refractory Bricks" has clear provisions for its various testing indicators.
From the above content, it can be seen that mullite materials play an important role in the refractory field. Different types of mullite products can exert excellent refractory properties in different temperature ranges, providing reliable guarantee for the stable operation of various industrial furnaces.
Gongyi Yuying Refractory Co., Ltd. always strictly follows national standards and focuses on the production of high-temperature refractory materials. Our products always adhere to the concept of letting you use with confidence, purchase with ease, and repurchase with peace of mind. We are committed to ensuring that you can purchase refractory bricks with stable and reliable quality. The company serves the lime, cement, metallurgy, casting, electricity, kiln engineering and other industries all year round, providing refractory supply and technical consulting services to our customers, and is committed to becoming a long-term strategic partner. I hope this article can provide you with valuable reference when you purchase refractory bricks, and I sincerely wish your high-temperature industrial production is smooth!
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