Factors influencing carbon dissolution from carbonaceous materials into Fe-C-S melts during direct iron smelting

摘要

In direct iron smelting technologies, such as HIsmelt~circleR, one of the advantages over the conventional blast furnace route of ironmaking is the utilisation of carbonaceous materials, such as coals, without any significant processing. Coals, introduced directly into the metal phase, will result in carbon dissolution into the metal and subsequently reduction of iron oxide by the high carbon metal. These technologies will have an edge over their competition, if the process is flexible enough to use a variety of raw materials. Therefore, the utilisation of different types of coals is of significant commercial interest and could have an impact on the flexibility of the process. although the dissolution of pure graphite into molten iron has been studied extensively, an understanding of the factors which influence carbon dissolution from coals, particularly material related properties, is far from complete. Coals are complex carbonaceous materials with high ash content and a relatively poorly ordered atomic arrangement, and the influence of structure on carbon dissolution in Fe-C-S melts is not well understood. In this study, the dissolution of coal and chars into molten iron at 1550 deg C has been studied and compared with our previous studies on synthetic graphite and natural graphite with the aim to establish an understanding of the influence of structure of carbonaceous materials on their dissolution into Fe-C-S melts. The influence of sulfur on carbon dissolution from synthetic graphite, coal and natural graphite was also compared. It was found that the rate of carbon dissolution shows a dependence on the structure of carbonaceous materials for poorly ordered materials, which can be quantified in terms of crystallite size (Lc). The retarding effects of sulfur on carbon dissolution also depends on the structure of carbonaceous materials.