LAUSR

The operation of the lower part, the hearth, plays a crucial role for the blast furnace (BF) as it is the region where the liquid products, hot metal (also called pig iron) and slag, accumulate before they are drained through the tapholes.1) The state of the hearth is also important as long furnace campaigns extending up to 20 years are aimed at with limited possibilities to repair the lining before the final blow-out.2) The hearth drainage process is complicated by the presence of a coke bed, the deadman, through which the liquids have to flow during their passage, and by the fact that the two liquid phases are drained through the same taphole. However, periods of one-phase flow may occur initially, followed by two-phase flow in the later parts of the tap. Since the tapholes cannot be kept open for longer periods as this would lead to excessive wear of the taphole lining, the furnace has to be tapped intermittently. In larger furnaces with several tapholes, the tapping operation can be practically continuous, but a cycling motion of the liquid levels in the hearth cannot be fully avoided because of variation in the tapping speed of the liquids. In summary, the blast furnace tapping process is complicated and appropriate control of the draining process requires fundamental understanding of the underlying phenomena.3,4) The outflows are driven by the in-furnace gauge pressure that balances the pressure drops induced by liquid flows through the deadman and taphole. As iron and slag drain Off-line Model of Blast Furnace Liquid Levels