In order to clarify the causes of the excess accumulation of molten materials in the blast furnace hearth which results in blast furnace troubles, such as hanging and slipping, the behaviour of flowing out and accumulation of slag in the furnace hearth is investigated.
The results of model studies of slag flow in the furnace hearth during tapping were analyzed as the scaleup problem based on the theories of fluid dynamics. The dimensionless flow-out coefficient FL in eq.(32) has been found to be closely related to the slag residual ratio, i.e. the ratio of residual amount of slag at the end of tapping to that accumulated at the begining (Fig. 8).
Further investigation using this relation shows that eight independent variables, i.e. viscosity, tapping amount, tapping rate and depth of slag, hearth diameter, effective hearth area, number of tapping and permeability of packed coke, determine the behaviour of flowing out and accumulation of slag in the furnace hearth. The results of investigations are as follows;
1) The residual amount of slag and the depth of slag layer increase with the increase in slag tapping rate and of slag viscosity.
2) The increase of the number of tapping operation is beneficial in maintaining the smooth furnace operation, if the tapping rate and/or slag viscosity increase.