2000 Volume 86 Issue 5 Pages 301-308
Chiba No. 6 blast furnace was blown out after the world record of service life, twenty years and nine months. During the blowing out operation, tracer was injected from the No. 23 tuyere. Further, metal, coke and slag in the lower part of the furnace were gathered and analysed to investigate the metal flow at the hearth bottom, and the protection mechanism of the hearth brick. As a result, a stable solidified layer of hot metal formed during most of the operation period has played a key role to prevent the hearth brick wear. The formation of the solidified layer is explained by the stagnant metal flow which is caused by the "low permeability zone".