ROLE OF SFCA IN PROMOTING HIGH-TEMPERATURE REDUCTION PROPERTIES OF IRON-ORE SINTERS

A comparative study was made of a hematite ore, both untreated and after being subjected to the temperatures encountered during thermal sintering, and a sinter produced from a feed consisting of 100% ore to study the influence of sinter bonding phases, such as SFCA, on reduction behaviour. Under low-temperature reduction conditions (550-degrees-C, 30 vol% CO in N2) the order of increasing reducibility followed that of increasing porosity and surface area. At 900-degrees-C, under similar conditions, the sinter exhibited higher reducibility than the ores even though the total porosity and chemical reducibility of the individual phases were lower. The observed reduction behaviour can be explained in terms of the higher total porosity of the natural ore at low temperatures and the higher level of fine pores in the sinter at high temperatures due to the presence of SFCA, which acts to support the fine pores (ca 0.1-mu-m) created by the reduction process. This leads to the conclusion that the main role of SFCA in sinter during high-temperature reduction is to maintain a high level of fine porosity. Some implications of this work for granule design and sintering practice are discussed.