The material composition and characteristics of bentonite clays for use as a binder in the production of iron ore pellets

The bentonite clays used in the production of iron ore pellets at metallurgical plants of Russia and Ukraine are analyzed. According to the composition of the exchange complexes, clay is divided into alkaline, where more than half of the components of the exchange complex are sodium and potassium cations (Na++K+, mEq per 100 g of clay) and alkaline-earth (calcium, magnesium, calcium-magnesium and magnesium-calcium), where more than half of the exchangeable cations belong to calcium and magnesium (Ca+++Mg++, mEq per 100 g of clay). The reserves of alkaline-earth bentonite clays of the Cherkassk deposit are the largest in the CIS. The mineralogical and chemical compositions, as well as the size and composition of the exchange complex of these bentonite clays, are analyzed. Clays are fundamentally suitable for the production of pellets under certain conditions and are located near the surface of the earth in three (II, III and IV) layers of the productive stratum. The II layer contains mainly Ca++ ions and substantially less Mg++ in the exchange complex; the III layer consists of the palygorskite mineral, which contains mainly Mg++ ions in the exchange complex, substantially less than Ca++ and more than in the II layer of Na+ ions; the IV layer is a natural mixture of II and III layers in a ratio of an average of about 1:1. Palygorskite and montmorillonite in the IV layer of the Cherkassk deposit create a high-quality dispersion both in the sense of colloidal and structural-mechanical properties of the suspension, which is also a favorable factor in the interaction of particles of the strengthening additive with particles of the concentrate. The analysis of strength indicators of pellets using bentonites with alkaline and alkaline-earth exchange complex is presented. It was shown that despite the low swelling of alkaline-earth bentonites, the quality of pellets with these bentonites, in some cases, is insignificant, and in certain conditions is not inferior to the quality of pellets with alkaline bentonites at the same flow rate