Abstract:
The thinning of iron ore mix to be sintered as a result of the increased use of ultra fine concentrates has emerged as a significant challenge for sinter plants. In this scenario, the role of quicklime, the binder in the cold agglomeration step, becomes even more relevant. This study experimented with various lime-based binder options on a laboratory scale using iron ore mixtures with a high concentrate content for two granulation routes. One used the Eirich intensive mixer in the homogenization and agglomeration stage and tested three sizes of quicklime at 35 kg/t of the mix: 0 to 3 mm, 0 to 1 mm and micropulverized. The tests which used micropulverized quicklime showed superior cold permeability as it is already observed in the field. The other granulation route used an Eirich intensive mixer and pelletizing disc, simulating the HPS process. In this route, several binders were tested. Micropulverized quicklime and hydrated lime yielded the most favorable outcomes, with hydrated lime exhibiting a more superior permeability curve. However, hydrated lime has not been widely adopted in the industry due to its higher cost of production, transportation and storage. Still on the HPS route, an experiment was conducted by increasing the micropulverized quicklime dosage from 41.4 kg/t to 62.3 kg/t up to full limestone replacement, which proved to be successful in combating the thinning of iron ore, thus presenting a feasible alternative. The super thinning of quicklime did not indicate significant gains in relation to the micropulverized product already used in the industry. Activated hydrated lime and high-concentration suspended calcium hydroxide did not obtain satisfactory results. The investigation indicates that using micropulverized quicklime and increasing its dosage is a viable option for countering the thinning of iron ore without changes in the granulation equipment’s.
