Refractories For Furnace Throat And Roof

The furnace throat mainly plays the role of protecting the furnace lining and reasonable distribution. When the furnace throat is working normally, the temperature is 400-500°C. This area is mainly affected by the direct impact and friction of the furnace charge, but the erosion of the gas flow is relatively light. Therefore, the furnace throat is generally made of water-cooled or non-water-cooled steel bricks (steel castings), and the gap between the water-cooled steel bricks and the furnace shell is filled with castables. The furnace roof is the gas enclosure and generally adopts metal anchors and wear-resistant refractory spray coating.

The furnace shaft is an important part of the blast furnace, which plays the role of heating, reducing, and slagging the charge. It bears the scour of gas flow and the impact of materials from beginning to end. However, the temperature in the upper and middle parts of the furnace body is relatively low (400-800°C), and there is no slag formation or slag erosion hazard. This part is mainly subjected to the impact of the furnace charge, the wear of the furnace dust rising, the thermal shock (up to 50°C/min), or the intrusion of alkali, zinc, etc., and the deposition of carbon. Therefore, high-quality clay bricks and high-alumina bricks with low porosity are mainly used in this part. Especially in the case of increased variety and quality of refractory products, the life of blast furnace lining is greatly extended.
However, with the harsh operating conditions of large and medium-sized blast furnaces and the establishment of a system to greatly extend the life of blast furnaces, refractory materials that are excellent in spalling resistance and wear resistance are required for this part. Therefore, phosphate-bonded clay bricks are also used in the upper part of the furnace body, and sillimanite refractory bricks and high-alumina refractory bricks with excellent spalling resistance are also used in the upper and middle parts.

The temperature in the lower part of the furnace body is higher, and this part is the area with more heat exchange, where a large amount of low-melting material is formed, and there is friction when the red-hot charge descends, dust scours when the gas rises, and alkali metal vapor erodes. Therefore, this part is extremely vulnerable to corrosion. In severe cases, the cooler is completely corroded, and it is only maintained by the steel shell. Therefore, it is required to use high-quality clay bricks, high alumina bricks, corundum bricks, aluminum carbon bricks, or silicon carbide bricks with good slag resistance, alkali resistance, high-temperature strength, and wear resistance. The lining also uses graphite bricks.