- Time:Mar 01, 2023
The ambient temperature in the transition zone of the cement rotary kiln is relatively high. After entering the kiln, the material is fully heated, but it cannot reach the firing state. Affected by the firing zone, the transition zone is in a thermally unstable state.
Due to the large temperature fluctuations in the transition zone, the amount of liquid phase inside the clinker is small and the viscosity of the liquid phase is not enough, resulting in long-term disappearance of the kiln skin and poor adhesion, so that the lining bricks are exposed to high-temperature environments for a long time and directly withstand the impact of high-temperature clinker and wear, and the penetration and chemical erosion of high-temperature exposed lining bricks by the melt in cement clinker, silicate low-melt, K2O, SO2, KCl and other components in kiln gas, and the effect of temperature gradient and erosion layer concentration gradient Under normal conditions, the metamorphic layer of the lining brick will be densified, and the structural layer will easily crack and fall off. The reciprocating cycle will seriously affect the life of the lining brick, which is the weak link of the new dry process cement kiln.
At the same time, because the temperature field in the transition zone is easily affected by the change of the coal injection pipe and fuel, and the refractory material is prone to thermal fatigue when the temperature field changes repeatedly, the general material cannot withstand the rapid cooling and heat caused by the change of the temperature field. , resulting in damage to the lining brick of the transition zone.
Therefore, the refractory material in the transition zone of cement rotary kiln should not only have high strength and resist mechanical stress, strong thermal shock resistance to prevent thermal fatigue damage, but also have good high temperature performance and corrosion resistance.
Magnesia-alumina spinel bricks have excellent corrosion resistance because the main components of cement clinker and cement clinker are alkaline materials. Due to the addition of magnesia-alumina spinel, thermal shock stability can be obtained, so it has been recommended by foreign companies. Applied to the transition zone of cement rotary kiln. Due to the late start of refractory materials in my country, the development of related technologies is relatively slow. It was not until the 21st century that they were gradually imitated by refractory materials companies in my country. However, due to the raw materials, production process, production equipment and production technology of ordinary spinel bricks Restricted by factors, the service life of the transition zone of cement rotary kiln is generally 3-4 months, and the longest time is no more than 6 months. Therefore, the market of magnesia-alumina spinel bricks for cement rotary kiln has always been monopolized by imported products.
In 2006, the magnesia-aluminum spinel brick produced by ZHENJIN REFRACTORIES solved this problem. The service life of this product in the second gear belt area of the transition zone of the new dry process cement kiln can reach more than one year, and it can be fired with The kiln lining maintains synchronous operation, which reduces the number of kiln shutdown maintenance and creates considerable economic benefits for users.
The ZHENJIN brand magnesia-aluminum spinel bricks have been safely operated for 366 days in the 6500t/d kiln of Huaxin Cement Wuxue Company, and 456 days in the 6500t/d kiln of Huaxin Cement Yangxin Company. Huaxin Cement’s 14 large kiln transition zones above 5,000t/d all use “ZHENJIN Brand” magnesia-alumina spinel bricks, and the operation period is more than 12 months, maintaining synchronous operation with the kiln lining of the firing zone.
With the promotion of the green development concept of energy saving and consumption reduction, the defect of high thermal conductivity of magnesia-aluminum spinel bricks (350°C, 4.0W/m K) is becoming more and more obvious. At the same time, with the practical application of my country's refractory industry, my country's cement industry has gradually adopted silica bricks with relatively low thermal conductivity (350°C, 2.5W/m·K) instead of magnesia-aluminum spinel bricks, and achieved better results.
GUIMO abrasion resistant brick is a kind of refractory material with Chinese characteristics developed by our country. It is mainly used at the end of the kiln. After practice, most of the transition zones of cement rotary kilns with a capacity of 4000t/d and below are currently built with silica bricks. More than 5000t/d of the transition zone of the rotary kiln is responsible for the working conditions. Although it is partially adopted, it has not been fully promoted.
The transition zone is divided into an upper transition zone and a lower transition zone. Generally, 1650 silica bricks (scale red bricks) can be used in the upper transition zone. Due to the high temperature in the lower transition zone, only magnesia-aluminum spinel bricks or 1680 silica bricks (silica red bricks) can be used. The temperature is relatively high, and the service life of refractory materials for the transition zone is generally about 12 months.
Compared with magnesia alumina spinel bricks, silica molybdenum bricks have the advantages of low thermal conductivity, good thermal shock stability and high cost performance; compared with silica molybdenum bricks, magnesia alumina spinel bricks have the advantages of strong corrosion resistance, and The disadvantage of high thermal conductivity, in the system processing waste cement rotary kiln, magnesia-alumina spinel bricks have better anti-alkali sulfur erosion effect, so considering the safety factor, most large-scale rotary kilns still use magnesia-alumina spinel bricks for masonry build. On the whole, GUIMO abrasion resistant bricks tend to replace magnesia-aluminum spinel in domestic cement rotary kiln applications due to their cost-effective advantages.
