Refractory materials used in blast furnace
Steelmaking blast furnaces use refractory materials for lining and maintaining the furnace. Refractory materials are substances that are resistant to heat or wear, and are selected according to the type of application and furnace temperature. Refractory materials used in blast furnaces must be able to withstand severe thermal and mechanical shock, high temperatures, and harsh chemical conditions. Furthermore, stability, good thermal conductivity and density, low thermal expansion, and in some cases, resistance to radiation are all critical properties.
Common refractories and their properties
Fireclay brick: Fireclay brick is composed of kaolinite and quartz processed with fireclay at 1100-1450°C. It has very good thermal stability and is suitable for use in all parts of the furnace. It is also resistant to sulfurous gas corrosion, and can effectively restrain the thermal expansion of flame-resistant bricks.
High alumina brick: High alumina bricks are made with the addition of alumina (30-55%) to the fireclay. It is highly slag-resistant and can effectively protect the furnace against high temperature erosion and acidic attack. It also has good thermal shock resistance and low thermal conductivity.
Non-metallic materials : These include graphite materials and refractory fibers. Graphite materials, made from phenolic or furan resin bonded graphite, are mainly used in blast furnace walls or roofs due to their excellent thermal shock resistance and strength. Refractory fibers use special types of spun glass, such as ceramic fibers and glass wool, which are highly absorbent and provide excellent thermal insulation.
Silica Brick: This type of brick is made from processed silica sand containing high concentrations of silica. It has good thermal conductivity, high temperature tolerance and good slag resistance, and is mainly used in the hearth, walls, and roof of the furnace.
Magnesite Brick: Magnesite brick is an acid refractory material made up of magnesium oxide, calcium oxide, and other trace elements. It has good heat resistance, strong slag resistance, and good corrosion resistance. It is mainly used in hearth, side wall, and roof.
Insulating brick: Insulating brick is made of clay, shale, or other mixtures. It is used as a secondary insulation system that is inserted between two layers of refractory brick. Its main purpose is to reduce thermal conductivity and limit the affected area caused by thermal spalling or breakdown.
Conclusion
Steelmaking blast furnaces use a variety of refractory materials, each chosen based on their performance characteristics. Fireclay brick, high alumina brick, non-metallic materials, silica brick, magnesite brick, and insulating brick are all common refractory materials used in blast furnaces. These materials help to reduce heat loss and maintain the integrity of the furnace. When choosing refractory materials, it is important to select the right material based on furnace temperature, application type, and other operational conditions.
