Effect of Surface Properties of Iron Ores on their Granulation Behavior

The granulation property of iron ores was generally influenced by their wettability, surface roughness and shape of the iron ore. In this study, the surface roughness and shape of iron ores were characterized by the ratio of BET specific surface area (S-BET) to specific surface area (S-LS) calculated using size distribution obtained by a laser diffraction method. Wettability of ores was characterized by measuring the contact angle (theta) between iron ore and water. Bed permeability was used as an evaluation index of granulation effect. A variety of materials were subjected to a granulation test under an actual production condition. Special attention was paid to four ores with different surface properties and wettabilities. Nine groups of mixtures were obtained by linear programming taking the basicity as the objective function. Granulation results showed that the optimum bed permeability of nine mixtures have a good linear relation with mass fraction of four ores studied. Slopes (k) of fitting lines were used to characterize the granulation properties of ores, binary linear regression equation was derived with the k used as dependent variable, and S-BET/S-LS used as independent variables: k=16.443-0.277x theta+0.058x(S-BET/S-LS), Granulation performance of iron ore gets better with decreasing the contact angle and increasing the ratio of S-BET to S-LS.