Blast furnaces are large high-temperature metallurgical furnaces that use coke to reduce iron ore to produce molten iron. The temperature, pressure, nature of physical and chemical changes, and the severity of working conditions experienced by the furnace lining at different heights within the blast furnace vary, leading to different mechanisms and conditions of lining damage, and thus different refractory materials are selected.

Throat

The throat is the passageway of the blast furnace and is highly susceptible to damage due to the impact and friction of descending solid charge. It is generally constructed with high-hardness, high-density high-alumina bricks and protected by wear-resistant cast steel plates.

Shaft

The shaft is the middle part between the throat and the bosh, divided into upper, middle, and lower zones. The upper and middle parts of the lining are mainly subjected to wear and erosion from descending charge and ascending dusty gas, with relatively mild damage. These areas are typically built with blast furnace-specific fireclay bricks with low free Fe?O? content, dense fireclay bricks, or high-alumina bricks, or constructed from fireclay refractory castables. The lower part of the shaft has higher temperatures and significant slag formation, with direct contact between the slag and the lining surface, leading to faster lining damage. High-quality dense fireclay bricks or high-alumina bricks with good refractoriness, slag resistance, high-temperature structural strength, and wear resistance are generally used for construction. The lower part of the shaft in large blast furnaces is mainly constructed with high-alumina bricks, corundum bricks, carbon bricks, or silicon carbide bricks.

Bosh

The bosh is the widest part of the blast furnace, where slag chemical corrosion, erosion by alkali metal vapors, and the frictional scouring of descending charge and high-temperature coke on the lining surface are very severe, making it one of the most vulnerable parts of the blast furnace. Medium and small blast furnaces can use high-quality dense fireclay bricks, high-alumina bricks, or corundum bricks; large modern blast furnaces generally use high-alumina bricks, corundum bricks, or silicon carbide bricks, and some also use carbon bricks.

Belly

The belly, located below the bosh and shaped like an inverted cone, is almost entirely damaged shortly after the blast furnace is started. Therefore, the belly is constructed with high-alumina bricks (Al?O? < 70%) or corundum bricks. Modern large blast furnaces commonly use carbon bricks and semi-graphitic bricks made of graphite-petroleum coke or graphite-anthracite.

Hearth

The hearth is mainly subjected to chemical corrosion, scouring, and alkali erosion from molten slag and iron. The hearth bottom is mainly damaged by the infiltration of molten iron into the brick joints, causing the refractory material to float and break. It is generally constructed with carbon bricks that have high refractoriness, high-temperature strength, good slag resistance, strong thermal conductivity, high bulk density, and good volume stability.