8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

HIsarna is an emerging and promising alternative ironmaking process. Smelting cyclone is used to melt and pre-reduce fine and un-agglomerated iron ore particles in HIsarna reactor. Fine ore and flux are injected in the smelting cyclone together with oxygen. The injected ore is intensely mixed with rising hot reducing gases, undergoes partial reduction and melting. The melt hits the water-cooled sidewalls of the cyclone section and flows down along with the wall and into the liquid bath in the smelting reduction vessel (SRV) where the final reduction takes place. The ore in the cyclone section is pre-reduced to a degree of about 20% through thermal decomposition and reduction by the SRV gas. The temperature of the melt is approximately 1450 ˚C. Variation of ore particles’ state is difficult to observe inside the cyclone. Therefore, theoretical estimation is extremely important under these conditions. Phase transformation is an essential information for reaction analysis. In addition, density of particles is necessary to estimate the residence time of particles in the cyclone. They were investigated in this study. Phase transformation of iron particles were experimentally studied in simulating cyclone conditions and compared with thermodynamic calculation results. During the reaction process, mineralogy of iron ore particles transforms from hematite to sub-oxides sequentially. The density of particles can be predicted in the reduction based on the phase composition. Therefore, previous density models were evaluated with reported experimental data of slag. As a result, a suitable density model has been developed to calculate the density of slag mainly with FeO-Fe2O3 contained. Density of the reduced ore particles was estimated based on this model. The results show that reduction of the ore could lead to about 10 % shrinkage of the particles. On the contrary, melting contributes around 10 % swelling of the ore particles. It would result corresponding variation of reaction time in flight.