The integrated blast furnace and oxygen steelmaking (BF-OSM) route is still a dominant process for worldwide steel production, currently producing more than 60 % of the world's total output of crude steel. The counter-current principle on which the blast furnace operates makes it reliant heavily on the quality of its burden to maintain a sufficient level of gas permeability in its upper shaft and of liquid and gas permeability in its lower part. Iron ore sinter, constituting a major proportion of blast furnace burden in most countries, particularly in the Asia-Pacific region, is therefore expected to have a significant impact on blast furnace performance.The chemical composition of iron ore fines, together with the thermal conditions that sinter blends are subjected to, plays an important role in forming the primary melt during the sintering process and consequently determines the sinter structure and quality. Considerable emphasis has therefore been placed on the chemical composition and consistency of iron ore fines, particularly in terms of alumina content. However, due to the limited reserves and increasing depletion of high-grade iron ore resources, the alumina content of iron ores is expected to increase gradually. While the increase in such constituents is relatively slow over a long period, it has still caused problems for blast furnace operators.This paper attempts to clarify the role of different types of alumina present in iron ore fines and their effects on melt formation, sinter structure and sinter quality, as well as the sintering process itself. Mechanisms responsible for the deterioration of the low temperature reduction degradation characteristics (RDI) of sinter due to the increasing alumina content are also reviewed. In addition, potential measures to counter the adverse impacts of alumina on sintering performance of hematite iron ore fines are also discussed.KEY WORDS: High alumina iron ores; kaolinite; gibbsite; melt formation; sinter structure; sintering performance, sinter quality.ISIJ International, Vol. 47 (2007), No. 3, pp. 349-358 Review 349 © 2007 ISIJ alumino-silicates like kaolinite (Al 2 O 3 · 2SiO 2 · 2H 2 O), while the A type ores contain gibbsite (Al(OH) 3 ). 9) Extensive work has been conducted on the effects of alumina on sinter structure, quality and productivity. 1,2,[4][5][6][9][10][11][12][13][14] While the results are not conclusive and sometimes contradict each other, it is generally believed that too much alumina impairs the sinter quality, particularly the low temperature reduction degradation characteristics. However, much of the previous work showing the strong adverse effects of alumina on sinter quality and the sintering process has been focused mainly on Indian ores, 1,[4][5][6]9) which often belong to A type iron ores. Only limited work has been conducted on the majority of iron ores that contain alumina in the form of kaolinite. 2,10,12) From high temperature X-ray diffraction studies on Fe 2 O 3 -SiO 2 -CaO-Al 2 O 3 ores, it has been found that kaolinite ty...

No abstract

In a world of diminishing resources, current research efforts are often directed to extending the life of existing resources and developing technology to treat resources deemed uneconomic. To this end, biotechnology has been explored as a potential low cost, environmentally benign alternative to many of the current mineral processing techniques. Microorganisms and their metabolites have been successfully applied in the leaching of metals from medium and low grade sulphide minerals for many years. Recent fundamental studies have shown that selected bacteria may also assist in the beneficiation of these minerals through bioflotation and bioflocculation. The current published research demonstrates that several bacteria and their excreted proteins and polysaccharides have a significant effect on the surface chemical properties of some minerals. As such, the bacterial cells and their metabolites can be utilised as flotation collectors and modifiers enabling selective separation. To date, these studies have primarily focused on the sulphide minerals; however, there is considerable scope to expand this research for the beneficiation of oxide minerals such as those contained in iron ores. This paper provides a comprehensive review of current research on the use of microorganisms for mineral beneficiation and the potential use of genetically modified bacteria and, further, discusses the applicability of bioflotation and bioflocculation for the beneficiation of Australian iron ores.

No abstract