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

Iron and steelmaking industry is in demand to utilize ultra-fine iron ores due to changes in its availability and quality worldwide. Sintering plants are adapting to introduce higher ultra-fines percentage on their mixtures, raising concerns over the cold agglomeration step, critical to maintaining process stability and performance. Sintering bed permeability, granules mechanical properties and size distribution are keen factors that must be taken into consideration to produce high-quality sinter. The purpose of the present paper was to investigate the influence of ultra-fines addition on the cold agglomeration process and its impacts on the formed granules. Mixtures were composed of sinter feed, lime and different ratios of two different ultra-fine iron ores: natural pellet feed (−0.15mm) and grinded pellet feed (−0.045mm). Initially, maximum moisture capacity for all tested mixtures was determined by a capillary ascension test. Thereafter the mixtures were submitted to granulation experiments on a laboratory scale granulation route. The granules produced were assessed through its size distribution by the Safe Analysis on Frozen Elements (SAFE) method, by its Granulation Index (GI), Degradation Index (DI) by shatter test and bed permeability by Japanese Permeability Unit (JPU). In order to understand the impact of ultra-fines on granulation, microstructure analysis of the granules was performed by optical microscopy. The results showed that the addition of ultra-fines increased the maximum moisture capacity of the mixture. It was also possible to observe the impact of ultra-fines on the granulation index, degradation index and bed permeability of tested samples. Optical microscopy showed different ultra-fines arranges throughout the granules structure, which points out to different granulation behaviors. The addition of iron ore ultra-fines on the tested mixtures affects the granulation process, which can indicate limitations to its use in industrial setups.