1. The performance of refractory materials in key parts of blast furnace has an important influence on the life of blast furnace
Blast furnace lining refractory material to withstand the effect of high temperature thermal shock, charge, gas erosion and wear, alkali metal erosion, the furnace is also under the hot metal and slag erosion, wash. Si N₄ Bonding SiC bricks and SiAlON bonding SiC bricks are widely used due to their superior alkali resistance and good thermal shock resistance, abrasion resistance, high temperature volume stability, etc. In China, Si₃N₄ was ₄ in combination with SiC bricks for the lower body, waist, and bosh. While in the United States and European countries, SiAlON ₃ bricks were ₄ ₄ in combination with SiC bricks for good application.
With the continuous development of blast furnace equipment technology, after the use of copper cooling wall, the limiting link of blast furnace life gradually shifts from the lower part of the furnace body, the waist, the belly and other high heat load areas to the furnace cylinder, and the furnace cylinder part gradually becomes the weak link in the performance of the blast furnace. The furnace cylinder usually adopts the composite technology of ceramic cup and carbon brick. In order to prolong the life of the furnace cylinder, it is the key to improve the performance of refractory materials and rational allocation. The bottom of the blast furnace hearth has been eroded by molten iron and slag for a long time, and it can not be repaired because of the long-term storage of high temperature molten iron, so higher requirements are put forward for the performance of ceramic cups and carbon bricks at the bottom of the blast furnace.
In addition, the blast furnace tuyere refractory in addition to being washed by strong airflow, but also by the strong influence of thermal shock and alkaline atmosphere erosion, often need to be repaired, and even need to be replaced, but also affect the forward flow of the blast furnace. The working condition of the iron orifice area is poor, and the iron orifice combination brick is used to match the material of the furnace cylinder, including carbon, semi-graphite carbon-silicon carbide, mullite, silicon carbide and so on. With the development of blast furnace ironmaking, refractories used in blast furnace are constantly developed and applied, and many new refractories technologies have emerged, which are worthy of attention and discussion.
2, the basic structure of the blast furnace and smelting process
The blast furnace body is divided into five parts from top to bottom: throat, body, waist, belly and cylinder. The temperature of each part is: the bottom of the furnace is generally 1450 ~ 1500℃, the hearth part, especially the tuyere area, is 1700 ~ 2000℃, the belly and waist area is 1400 ~ 1600℃, and the body part of the furnace is 600 ~ 800℃.
In blast furnace production, iron ore, coke and slag flux (limestone) are loaded from the top of the furnace, and the preheated air is blown into the tuyere located at the lower part of the blast furnace along the furnace. At high temperatures, coke (some blast furnaces also blow auxiliary fuels such as pulverized coal, heavy oil, and natural gas) burns with oxygen in the air to generate carbon monoxide and hydrogen, and the iron ore is reduced to iron during the rising process in the furnace.
FIG. 2 Schematic diagram of blast furnace ironmaking
3, blast furnace refractory materials and damage mechanism