Blast furnace is a large high temperature metallurgical furnace for smelting molten iron from coke reduced iron ore. The furnace lining of different heights of the temperature, pressure, physical and chemical nature of the change, the severity of working conditions are different, so the lining damage mechanism, damage condition is also different, the selection of refractory is also natural different.
Title：What refractory bricks should be used in each part of a blast furnace
The throat of the furnace is easy to be damaged by the impact and friction of the falling solid charge. Generally, high hardness and high density aluminum bricks are used for masonry, and wear resistant cast steel plate is used for protection.
Around the middle of the furnace as the throat to the furnace waist, points up, middle and down three zones, the upper and middle lining mainly by falling burden and increase wear and erosion of the dust-containing air flow, damage to a lesser degree, generally contain low free Fe2O3 of blast furnace use special clay brick, or density of clay brick, or high alumina brick masonry, also can use clayey monolithic refractories.
The lower part of the furnace body temperature is higher, there is a large amount of slag formation, slag and furnace lining surface direct contact, furnace lining damage quickly, generally choose good fire resistance, slag resistance, high temperature structure strength and good wear resistance of high quality dense clay brick or high aluminum brick masonry. The lower part of large blast furnace body is mainly constructed with high aluminum brick, corundum brick, carbon brick or silicon carbide brick.
The furnace waist is the widest part of the blast furnace. The chemical erosion of slag, alkali metal vapor erosion and friction erosion of the lining surface of the decreased burden and high temperature coke are very serious, which makes it one of the most vulnerable parts of the blast furnace. Medium and small blast furnaces can use high quality dense clay bricks, high aluminum bricks, corundum bricks; Large modern blast furnaces generally use high aluminum brick, corundum brick or silicon carbide brick, but also use carbon brick masonry.
The belly of the furnace is located under the waist of the furnace, which is inverted conical. The general blast furnace is almost completely destroyed soon after opening. Therefore, high aluminum bricks (Al2O3>70%) and corundum bricks are used in the belly of the furnace. Carbon brick and graphite – petroleum coke, graphite – anthracite brick are widely used in modern large blast furnaces.
The hearth is mainly subjected to chemical erosion, scour and alkali erosion of molten slag and molten iron. The bottom of the furnace is mainly molten iron into the brick seam, so that the refractory floating and damage. Generally, carbon bricks with high refractories, high temperature strength, good slag resistance, high thermal conductivity, high volume density and volume stability are used for masonry.