The Characteristics of Iron Ore Slimes and Their Influence on The Flotation Process

The flotation has been successfully applied to process the iron ore for the particle size (Ps) from 10 µm up to 150 µm. The presence of the slimes (Ps < 10 µm) is harmful on the reverse flotation of quartz, so they are usually prior removed by hydrocyclones. The main effects of the presence of slimes on the flotation are related to the increase on reagents consumption, the froth stability, and decrease on the selectivity. The lower floatability of coarse quartz particles (+74 µm) combined with the presence of slimes, even in small quantities, drastically affect the flotation response. This paper shows a study of characterization of a typical iron ore slime, aiming to create a better understanding of its role on the concentration by flotation. The main characteristics of typical slimes from the Iron Ore Quadrangle in Brazil are the presence of almost 70% of hematite, 25% of quartz, and 5% of kaolinite, as the main silicates gangue minerals. Furthermore, the particle size distribution revealed that 80% of the hematite and the kaolinite are below 20 µm. The affinity between the ultrafine kaolinite of the slimes with the corn starch is harmful to the reverse flotation of quartz, as the starch has an important depressing action over the hematite. The presence of 20% of hematite −20 µm decreased the recovery to the froth of quartz + 74 µm from 97% to 62%, where the slimes coating seems to be the main responsible.

Development of hematite ore pellet utilizing mill scale and iron ore slime combination as additive

Iron ore slime is generated from mines during processing and washing of iron ore, and it is not considered for pelletizing due to its excessive fineness and high gangue content, despite its good green bonding property. Mill scale is generated from steel rolling mills and reheating furnaces; it has almost nil gangue content, but is not individually considered for pelletizing due to its poor green bonding property. If both of these two wastes are blended in combined form with hematite ore, the high gangue of slime would be balanced by the gangue free mill scale. While mill scale provides exothermic heat of oxidation of FeO and Fe3O4 in it and enhance the diffusion bonding, slime provides good green bonding property to the pellet. Therefore, in this study a good quality pellet was developed by the combined mixing of these two wastes in hematite ore without much increase in gangue content. Up to 15% of mill scale and 15% of slime could be used successfully. The developed pellets provide improved cold compressive strength (366 kg/ pellet), reducibility index (82%), and reduction degradation index (8.5%). Induration temperature could be reduced by 75 ?C, which indicates a considerable energy saving in induration furnace.