Blast Furnace Hearth Design Evolution

It can be strongly argued that the BF Hearth is the most critical part within the whole integrated steel plant when considering overall potential profit/loss. A major incident with the hearth impacts all downstream activity resulting in serious loss. In some cases, such an episode can endanger overall viability of the whole site. When long, stable BF operation is achieved optimum operating conditions can be maintained throughout the process, efficiency and profitability can be maximised. Problems above tuyere level can often be resolved with minimal disturbance, but not hearth problems. With Savoie/Saint-Gobain BF design and supply experience, they recognised the importance of the hearth, commenced a major R&D program (still ongoing) and pioneered the first "Ceramic Cup" technology in 1984. Major improvements were made in carbon quality around the same time resulting in finer pored structures (minimizing metal penetration) and additions of ceramics (to improve erosion resistance). The importance of freezing a protection layer on the carbon hot-face was recognized leading to further carbon quality changes (higher conductivity but with better erosion resistance than graphite) and a reassessment of optimum wall thickness. This paper will summarize BF Hearth design evolution, explain why the Ceramic Cup was conceived and how the design has evolved over the last 25 years. The tendency towards using the Ceramic Cup will be highlighted together with results and isotherms from references. How the Ceramic Cup can benefit the BF operator in terms of operation and efficiency will be explained and quantified.