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As the growth of crude steel production is saturated at home and integration of iron production to large-capacity blast furnaces is encouraged to secure primary iron sources, particular attention is attracted to the stability in high productivity operation. Today the abnormal blast-furnace operating condition exerts unprecedented enormous effects on the downstream processes. The preventive and problemhandling technologies has been discussed. In particular, it has been pointed out that “the blast furnace is operated while it is being subject to a large number of operation and external factors including material conditions, blast conditions, furnace body conditions, and others. It cannot be impossible to think that all these factors act on the blast furnace operation free of any variations. As a result, it is a matter of course that the blast furnace gives rise to some kind of abnormal phenomena, and what is important is to quickly detect the sign of abnormality.” Particularly in this Report, the increased size of the blast furnace and high productivity operation are pointed out as the causes of increased troubles of recent years, which particularly attract our attention. From the viewpoint of the increased size of the blast furnace and high productivity operation, still more stringent control must be practiced on slag and metal. The blast-furnace tap hole closing refractory (hereinafter called the mud material) is important for tapping operation of the blast furnace, and the mud material filling distance in the in-furnace depth direction (hereinafter called the tap hole depth) is one of the important operation control items to control the hearth-side wall thickness. The characteristics which the mud material is requested to possess have been changed from simple closing of a tap hole to stable operation, improvement of working environment, reduction of consumption rate by reduction of the number of casts per day, and protection of hearth-side wall refractory and extended life of the furnace body by extension of the tap hole depth. Consequently, in addition to securing of gas and liquid permeability of deadman coke by coke center charging, it is important to maintain the tap hole depth in order to prevent the circulating flow of slag and metal from the free space forming behavior. However, fluctuation factors of the tap hole depth have not exactly been elucidated. Therefore, in this study, the raceway depth is measured from the reflection intensity of microwave that is struck from the tuyere and effects of raceway depth and various factors on the tap hole depth is reported with a hope to contribute to further improvement of the blast furnace operating technique.

Stabilization of Tapping Hole Length by Controlling Blast Furnace Raceway Depth