Aspects from Powder Behavior to Ensure Burden Bed Permeability for Low Carbon Operation of Blast Furnace

Abstract

Low reducing agent rate (RAR) operation of blast furnace is a key technology to reduce carbon dioxide emission from the steel industry. To realize stable and highly effective operation of blast furnace under low RAR condition, permeability in the furnace has to be kept in sufficient level. Keeping bed permeability is an essential issue in blast furnace operation especially from the viewpoint of prospective change in circumstance of raw material resources. This paper focuses on powder behavior that deteriorates bed permeability in blast furnace. It is known that excessive accumulation of powder in the burden bed causes serious operation troubles like slip, hanging and so on, therefore the powder accumulation should be suppressed as little as possible. To suppress powder accumulation it is necessary to understand the powder behavior in packed bed, thus this paper summarizes three mechanisms of powder formation, flow and accumulation in blast furnace. Regarding powder generation, numerous research works on ore degradation with progress of reduction, un-burnt char formation in raceway zone and coke degradation have been made and revealed their characteristics in detail. As for powder flow and accumulation, their macroscopic characteristics have been elucidated. It is expected that the profiles of temperature, gas concentration and material flows in the blast furnace under low RAR operation is drastically different from the ones under current operating conditions. Thus further discussions taking into account such differences in conditions and microscopic viewpoints are required for comprehensive understanding of powder behavior under low RAR blast furnace operation.