Deadman and hearth phenomena in the blast furnace

The deadman and hearth phenomena play key roles in hot metal quality. The condition of the deadman has a strong influence on hot metal temperature and composition. When hot metal can flow freely towards the tap hole and the deadman is a porous coke bed, then conditions are good for desulphurization and carbonization of hot metal. The deadman has also a significant effect on lining wear and campaign length by controlling hot metal flow in the hearth. Particular observations of hearth behaviour have been made during the last six years. Data of blast furnace operation have been studied and compared with hearth condition, hot metal and slag properties. Several methods to control the dead man have been experienced in Koverhar. The best method so far is to use coarse coke with low reactivity and to control burden distribution with movable armour. Response times to hearth control actions are painfully long – four weeks or even more. A set of indications about deadman condition have been collected. Hearth bottom temperatures are used to monitor the location of 1150°C isotherm. Rod tests have been used to sound the dead man hardness and to measure the length of the raceways. Interesting dependence between deadman condition, reduction of iron, hot metal sulphur and carbon and hot metal temperature has been found. This knowledge has been practised resulting in remarkable improvement of hot metal quality and hearth condition.