Evaluation of refractory lining of the blast furnace hearth and bottom in five years of its operation on the basis of the isotherms shapes

Based on archival temperature measurement data regarding a blast furnace (capacity of 3200 m(3)) hearth and bottom refractory lining, empirical isotherms T = 300 degrees C, for various periods of the first five years of the furnace campaign were determined. This resulted in an attempt to assess the hearth and bottom refractory lining in the third month and subsequently, in the next years of the blast furnace operation. The empirical isotherms, determined after the first three months, were compared to the isotherms determined using the method of mathematical modelling. These empirical isotherms were compared to each other, respectively in one-year intervals. The most distinctive changes of the hearth and bottom refractory lining were observed during the first three months of the furnace campaign. In the further period of five years, the changes were insignificant. During the early stage of furnace operation, observed deterioration of the refractory lining was associated with partial damage of the bottom ceramic layer and "elephant's foot"-shaped defects of the refractory lining in the lower, thickened parts of the hearth walls. Early, "elephant's foot"-shaped wear of the refractory lining is related to the mechanism of its wash-out by liquid products of the process during tapping, which results from certain maladjustment of the hearth and bottom inner geometry in modern furnaces to the hydrodynamic conditions of metal and slag flow.