In iron making enterprises, ball type hot blast stove is blast furnace heating equipment. The core of the technical problem of the ball hot blast stove is the ball bed. The refractory ball bed is formed by natural accumulation of equal diameter fire-resistant balls. It is generally divided into upper and lower sections according to different ball diameters and materials. There are three types of fire-resistant balls used as heat medium materials in the high temperature zone of the upper section of the ball bed:
- High aluminum fire resistant ball
Refractories with Al2O3 mass fraction greater than 45% and mainly composed of alumina or aluminosilicate are called high alumina refractories. Generally, the fire resistance of high aluminum fireball shall not be lower than 1750-1790 ℃, and the initial temperature of load softening shall not be lower than 1400-1530 ℃. When the Al2O3 content of the product is higher, its thermal stability will be significantly reduced.
The high alumina refractory balls used in the production are used in the high-temperature zone of the upper section of the ball bed. Their fire resistance and load softening temperature can meet the requirements, but their thermal stability and slag resistance are insufficient. Therefore, surface cracks and slagging bonding often occur, resulting in poor permeability of the bed and shortened ball cleaning cycle.
- Silicon fireball
Silicon fireball is a kind of acid refractory, with the mass fraction of SiO2 greater than 93%. Other components are mainly Al2O3, Fe2O3, Cao, MgO and some alkali metal oxides. The fire resistance of silicon fireball is generally 1710-1750 ℃, and the load softening temperature is high, up to 1640-1650 ℃.
In production, the silicon fire-resistant ball is used in the high-temperature area of the upper section of the ball bed. Under the conditions of high temperature and large gradient temperature change, the ball surface cracks seriously, the ability to resist alkaline gas dust erosion is poor, the slag bonding phenomenon is serious, and it is difficult to clean the ball.
- Magnesium aluminum fire resistant ball
The fire resistance of magnesium aluminum fireball generally exceeds 2000 ℃, the load softening temperature is generally not higher than 1550 ℃, and it has strong resistance to alkaline slag erosion.
The production process of magnesium aluminum refractory ball is more precise and strict than that of ordinary magnesia brick, and its service performance is better than that of ordinary magnesia refractory products; Good thermal stability, the number of heat exchange in water at 850 ℃ can reach more than 20 times; The slag resistance is good, especially the ability to resist Fe2O3 corrosion. Magnesium aluminum fire resistant ball is applicable to the upper section of the ball bed with high working temperature and frequent fluctuations.
There are three kinds of fire resistant balls. Magnesium aluminum fire resistant balls are conducive to heat storage and heat transfer of hot blast stove, and solve the problem of ball sticking. Under the action of long-term high-temperature load, the structure is stable without embrittlement and softening. At present, in the high-temperature area of the upper section of the ball bed, magnesium aluminum fire resistant balls gradually replace the other two, and are used by more and more enterprises.