Blast furnace hearth drainage: Physical mechanisms

Abstract

The major physical mechanisms governing blast furnace hearth drainage are identified. It is shown that iron and slag flow simultaneously from the hearth during the drainage process and that the flow of iron has a marked effect on the drainage of the slag phase. Previous assumptions which consider the iron and slag to flow separately and the iron level to remain horizontal and fixed at the level of the taphole during the flow of the slag phase are shown to be invalid. The iron phase is shown to be drained to levels considerably below that of the taphole and this is demonstrated to have an important effect on operating liquid level in the furnace. A two-dimensional model which accounts for the simultaneous drainage of iron and slag from a packed bed is described. The model predictions are compared with two-liquid laboratory drainage experiments and applied to actual blast furnace conditions. The model shows that large errors may be introduced in estimates of slag residual volume when the results from single-liquid drainage experiments are applied to actual blast furnace conditions.