In this study effect of lime, dolomite and bentonite on reducibility of pure hematite was investigated. With respect to continues change in chemical composition of iron ore in Iran and then changes in additives used in iron making, it is necessary to investigate effects of additives during sintering and reduction process. For this purpose 1, 3 and 6 wt% of lime, dolomite and bentonite was used in carbothermic reduction of hematite. First additives and hematite was mixed and sintered at 1200 °C for 1.5 hour. Then samples crushed and mixed with certain amount of graphite then compacted.Thermal gravimetries of samples show that reduction start at about 800 °C and complete at 1200 °C and according to this isotherm reduction was carrying out at three temperatures 850,925 and 1000 °C. Reduction degree was calculated and effect of different amount of additives at different temperature was compared. Phase analysis and microstructure investigation was performed by x-ray diffraction (XRD) and scanning electron microscope (SEM) respectively. Results show that addition of bentonite reduces reduction degree while dolomite has no effect on reduction degree. Lime also reduces reduction degree but less than bentonite. By increasing temperature reduction degree increased and maximum reduction degree at 850 and 925 °C raised to 40 % and at 1000 °C reduction was completed (reduction degree was 100 %).X-ray diffraction of samples after sintering corresponded hematite peaks and has no extra peaks. Scanning electron microscopy investigation show reduced iron and approves results. Key Word : reducibility ; direct reduction ; hematite ; additive
