Effect of additive size on the softening and melting behavior of slag

The Paris climate change agreement made a commitment to keep global warming below 2 °C. The Korean government confirmed that it would seek a 37% reduction in CO₂ emissions by 2030 from the Business As Usual level. CO₂ emissions from Korean iron and steel industries account for approximately 15.4% of that reduction. Therefore, breakthrough technologies are urgently required to reduce the CO₂ emitted from iron and steel making processes. À high efficiency iron making process is needed, because present methods consume huge amounts of energy. One of the key technologies for high efficiency iron making is more effective slag making. Understanding the effects of basic oxide additives such as lime and dolomite on the slag melting is required. In this study, the effects of additives (CaO and MgO) on the melting behavior the CaO-SiO₂-Al₂O₃(-MgO) slag were investigated using a high temperature in-situ observation technique. For the CaO-SiO₂-Al₂O₃ system, when the particle size of CaO was increased, slag melting was delayed. When 10 wt% of 1-2 mm diameter CaO or MgO was added, it was observed that the MgO addition delayed melting of the CaO-SiO₂-Al₂O₃-MgO system. Accordingly to facilitate slag melting, finer additives are recommended. In addition, it was determined that lime was more useful for making molten slag than dolomite.