EXTENSION OF BLAST-FURNACE CAMPAIGNS - FACTORS WHICH AFFECT THE LIFE OF THE FURNACE HEARTH

General trend towards operation of large-capacity blast furnaces, without stand-by furnaces. Extension of the furnace campaign achieved hitherto and reduction of hearth wear. Analysis of the main factors which affect the life of the hearth: hot-metal flow, chemical attack by hot metal and slag, infiltration as well as thermomechanical stresses in the carbon brick. Possibilities of reducing wear through plant engineering and material specific technical measures: modification of the blast-furnace hearth, selection of the refractory lining. Process engineering measures for the reduction of refractory wear: control of the composition of hot metal and slag as well as of the quality of the burden and fuels, modification of the tapping technique, minimization of the frequency and duration of blast-furnace shutdown as well as prevention of water ingress through defective tuyere and cooling elements. Preventive measures designed to avoid excessive wear: monitoring of hearth temperatures by thermoelements and pressing-in of plastic refractories through the steel jacket as well as sealing of tuyeres and modification of the tuyere cross section.