Effect of high Blaine iron ore fines in hematite ore pelletization for blast furnace

Abstract

Blaine fineness is one of the most important parameters in pelletising. While the lower Blaine fineness does not provide sufficient strength to the both green pellet and indurated pellet, excessively high Blaine fineness causes problem in pellet making. Optimum Blaine fineness of iron ore in the range of 1700–2250 cm2/g is usually used for good quality pellet making. However, when a material of high Blaine fineness is produced after beneficiation and there is no option to control the fineness, the pellet making from high Blaine fineness ore becomes obligatory. In this work, the effect of high Blaine fineness (2700–3250 cm2/g) on the pellets properties has been studied and the optimum parameters to make it usable for blast furnace have been examined. 0.3 wt% bentonite and maximum 7 wt% initial moisture in the green mix with 45–50° disc angles have been found to be suitable for green pellet making with 2700 and 2986 cm2/g Blaine fineness. These pellets show very good CCS (260–290 kg/pellet), reducibility index (71–75%), reduction degradation index (12–13%) and swelling index(12–16%) at the optimum induration temperature of 1280°C for 10 min. However, very high Blaine fineness (say 3250 cm2/g) requires relatively lower initial moisture (5%), higher disc angle and lower induration temperature (1250°C).