What type of refractory bricks are used for the shaft and hearth of a blast furnace?

01. Overview
The shaft of a blast furnace is divided into three sections: upper, middle, and lower. In small-scale furnaces, the upper and middle sections experience relatively low temperatures and are not subject to slag erosion. Consequently, these areas primarily utilize phosphate-impregnated clay bricks or high-alumina bricks; conversely, the shafts of large-scale furnaces more frequently employ composite high-alumina bricks enhanced with sillimanite or andalusite.

02. Dense Clay Bricks in Blast Furnace Shafts
Dense clay bricks are also utilized in blast furnace shafts. As furnace temperatures and operating conditions in medium-to-large furnaces have become increasingly severe, the upper sections of the shaft have increasingly adopted phosphate-impregnated clay bricks, while the upper-middle sections have turned to low-creep high-alumina bricks. For small-scale furnaces, high-alumina bricks with an alumina content exceeding 75% remain a viable option.

03. The Lower Section of the Furnace Shell Is Most Prone to Damage
The most vulnerable part of a blast furnace shell is its lower section. This is because this zone is an area of ​​intense heat exchange; furthermore, the lower furnace body is subjected to friction from the descending furnace charge and erosion from dust abrasion. Additionally, it suffers from severe corrosion caused by alkali metals. Materials typically employed in this region include clay bricks, high-alumina bricks, corundum bricks, or silicon carbide bricks. In steelworks abroad, materials such as high-alumina bricks, clay-bonded silicon carbide bricks, and silicon carbide-graphite bricks are utilized, with some facilities also opting for electro-fused high-alumina bricks or synthetic mullite bricks. In China, however, the use of corundum bricks or silicon carbide composite bricks is more prevalent.

04. Ceramic-Bonded Silicon Carbide Bricks for the Lower Furnace Shaft
Ceramic-bonded silicon carbide bricks are sometimes utilized in the lower section of the blast furnace shaft. Based on operational performance, silicon carbide bricks generally outperform phosphate-impregnated clay bricks, though their cost is relatively higher. While phosphate-impregnated clay bricks are inexpensive, the impregnation process is cumbersome; consequently, many manufacturers are reluctant to produce this product, opting instead to supply low-porosity clay bricks that meet the same specifications as their phosphate-impregnated counterparts. Currently, various materials are employed for blast furnace hearths, including alumina-carbon bricks, microporous alumina-carbon bricks, semi-graphite carbon bricks, self-baked carbon bricks, and carbon ramming mixes. However, based on field performance, silicon carbide bricks have gained widespread application in the lower blast furnace shaft. This is because silicon carbide bricks exhibit minimal erosion; furthermore, utilizing them as a lining in the lower shaft helps enhance thermal efficiency and extend the furnace's service life.

05. Conclusion
Silicon carbide bricks are also utilized in the lower section of the blast furnace shaft. The primary reason for this choice is that silicon carbide bricks do not react with the blast furnace slag; furthermore, they exhibit excellent thermal shock stability and abrasion resistance, while simultaneously preventing the formation of accretions. Consequently, silicon carbide bricks can be regarded as an ideal refractory lining material for the lower section of the blast furnace.

Supply high quality refractory bricks use for Blast Furnace with best price 

Contact : 

Whatsapp: 008615527482889

Email: sales@skrefractory.com