Study of bentonite clays influence on quality indicators of pellets

Abstract

Quality of iron ore pellets depends on many factors, including the type and properties of binding materials, in particular, bentonite clays. Laboratory studies of bentonite clays, differing by mineralogical composition and exchange ion complex. To assess the metallurgical characteristics of the pellets obtained with various kinds of binders, the moisture of the pellets, the compressive strength of the wet and dry pellets, the number of the wet pellets discards without destroying, and the “shock” temperature were determined. The carried out tests have shown that the impact strength and compression resistance of wet pellets at a slightly increased specific consumption of bentonite of cherkasy alkaline-earth bentonite does not concede to the correspondent properties of pellets with application of alkaline saryugyshsky bentonite as the binder. It was shown that clays of the IV layer, which are a natural mixture of alkaline-earth bentonite of the II layer and palygorskite III layer of the Cherkassky deposit, are favorable, to ensure good quality of the raw pellets. Tests of composite mixtures of clays IV with II and II with III layers showed that the quality of raw pellets with cherkassky bentonite is slightly worse comparing with sarygyuhsky one, however, the absolute values of their indicators satisfy the industry requirements. Tests of pelletizing of charges with different wetness, with the addition of 0.5% alkaline bentonite and a mixture of clays of the IV and II layers of the cherkassky deposit were carried out. It was shown, that with wetness increasing, pellets with both types of binder additives show the increase of the dynamic strength, porosity and temperature of the “shock” with a minimum difference in the absolute values of indicators with different binders. For confirmation of the possibility of using alkaline-earth bentonite of the Cherkassky deposit (II–III–IV layers) in the production of pellets, it is necessary to accomplish comparative industrial tests at a pelletizing plant (for example, at SevGOK), which uses a concentrate and industrial water of increased hardness.