General trend towards operation of large-capacity blast furnaces, with
out stand-by furnaces. Extension of the furnace campaign achieved hith
erto 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 t
he carbon brick. Possibilities of reducing wear through plant engineer
ing and material specific technical measures: modification of the blas
t-furnace hearth, selection of the refractory lining. Process engineer
ing measures for the reduction of refractory wear: control of the comp
osition 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. Preve
ntive 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 modificati
on of the tuyere cross section.