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How to Choose Refractory Lining for Blast Furnace Hot Blast Stove
The top of the hot blast stove is the high temperature zone in the hot blast stove. The refractory material at the top of the stove, especially the brick layer directly in contact with hot air and hot flue gas, must have good thermal shock resistance and creep resistance. Generally, silica bricks or low creep high alumina bricks are used, and the thermal insulation layer is clay thermal insulation bricks. When selecting thermal insulation materials, special attention should be paid to the working hot surface temperature not higher than its allowable use temperature.
The large wall of the hot blast stove is the surrounding wall of the hot blast stove body, and its lining includes refractory bricks for the working layer, lightweight bricks for the heat insulation layer and fillers. The upper part of the large wall bears a higher temperature, and the middle and lower part bears a lower wind temperature. The upper working layer of the large wall generally uses low creep high alumina bricks or silica bricks, and the middle and lower parts of the large wall generally use high alumina bricks and clay bricks. Insulation layer, generally use different grades of insulation bricks, refractory ceramic fibers or fillers according to different parts.
Hot Blast Stove Partition
The partition wall of the hot blast stove is a refractory wall that separates the combustion chamber and the regenerator. The partition wall and the furnace roof cannot be completely built up to conflict with each other, and a certain expansion joint (200~250mm) should be left. In order to distribute the air flow evenly, the partition wall should be 400~700mm higher than the checker bricks of the regenerator. In the lower part of the partition wall, the temperature difference between the two sides is very large, and the difference in thermal expansion is also very large, which causes the partition wall masonry to continuously bend and crack. The upper part of the partition wall is generally made of low-creep high-alumina bricks or silica bricks, and the middle and lower parts are generally made of high-alumina bricks and clay bricks.
Burner
The burner is a device used to mix gas and air and send it into the combustion chamber for combustion. In terms of materials, there are metal (mechanical) burners and ceramic burners. At present, ceramic burners are mostly used.
During the air supply period, the upper surface temperature of the ceramic burner is slightly lower than the air temperature; during the combustion period, it is slightly higher than the temperature before the air and gas enter the burner. Therefore, the temperature difference at the upper part of the burner is large in one cycle, especially at the moment of furnace change. , The temperature of the upper part of the burner rises (or drops) very quickly. In order to ensure the airtightness, integrity and service life of the burner masonry, it is required that the refractory material has a small linear expansion coefficient and good creep resistance. Before the 1980s, almost all ceramic burners in my country used high alumina phosphoric acid refractory castable or alumina refractory castable preforms. After more than 20 years of production practice, this material is suitable for medium and small blast furnace hot blast stoves and air temperature of 1100°C. Ceramic burners on the left and right are applicable. When using high alumina phosphate refractory castable, it should be baked to about 600°C before masonry to prevent cracking of the preform during installation and use. After entering the 90s, due to the large-scale hot blast stove and the requirements of high air temperature, high alumina cordierite refractory materials are now mostly used, a few ceramic burners use mullite cordierite materials, and the lower part of the ceramic burners, except for a few use sillimanite materials In addition, almost all use high alumina or clay refractory materials.
Checker Bricks and Refractory Balls
The main requirement of checker bricks in the high temperature area of the regenerator is to have good high temperature volume stability, corrosion resistance and creep resistance. Silica bricks have these characteristics and are cheap. Therefore, high wind temperature at home and abroad It is widely used on wind furnaces. According to the specific domestic situation, when the design temperature of the top of the hot blast stove is not less than 1400°C, and under the premise of good blast furnace fuel combustion and high operating level, the preferred refractory material for the high temperature zone of the hot blast stove should be silica brick. The residual quartz must be controlled at no more than 2%. Hot blast stoves using silica bricks need to pay attention to carefully determining the lower limit of the use of silica bricks, and install a reliable temperature detection device here to ensure that the minimum use temperature of silica bricks is not less than 800 during production operations (including shutdown of the furnace) °C. When the design temperature of the hot blast stove top is not higher than 1400°C, the use of low-creep, high-density high-alumina refractories is more suitable for my country's reality and can make full use of my country's rich bauxite resources.
Combination Brick for Each Hole of Hot Blast Stove
The hot blast stove has many orifices and the working conditions are very bad, so the masonry life of the orifice is often a weak link in its overall structure. In order to improve its life, people try to improve its integrity, stability and high-temperature characteristics of the refractory materials used in all aspects. Combination brick technology is a comprehensive technology integrating these measures. The combined brick technology is widely used abroad, and it has also been quickly promoted and widely used in my country since Baosteel introduced the technology.
