M. H. Hemmati, J. Vahdati Khaki, A. Zabett,
Volume 12, Issue 3 (9-2015)
Abstract
The volatile matter of non-coking coal was used for the reduction of hematite in argon atmosphere at nonisothermal condition. A thermal gravimeter furnace enable to use an 80 mm-height crucible was designed for the
experiments to measure the weight changes of about 10 grams samples. A two-layered array of coal and alumina and
four-layered array of iron oxide, alumina, coal and alumina was used for the devolatilization and reduction
experiments, respectively. The net effect of volatile reduction of Fe
2O3was determined and it was observe that 45%
reduction has been achieved. Three distinct regions were recognized on the reduction curve. The reduction of hematite
to magnetite could be completely distinguished from the two other regions on the reduction curve. At 600-950°C, the
reduction was accelerated. 63% of volatile matter resulted in 25% of total reduction before 600°C while the remaining
volatile matter contributed to 75% of the total reduction. From the reduction rate diagram, the stepwise reduction of
the iron oxides could be concluded. The partial overlap of the reduction steps were identified through the XRD studies.
The starting temperature of magnetite and wüstite reduction were determined at about 585°C and at 810°C,
respectively.
M. Monzavi, Sh. Raygan,
Volume 17, Issue 3 (9-2020)
Abstract
Low-grade iron ores contain many impurities and are difficult to upgrade to make appropriate concentrates for the blast furnace (BF) or direct reduction (DR) technologies. In this study, the beneficiation of an Oolitic-iron ore (containing 45.46wt% Fe2O3) with magnetization roasting by non-coking coal (containing 62.1wt% fixed carbon) under a stream of argon gas was investigated. Then, a 2500 Gaussian magnet was used for dry magnetic separation method. The effects of roasting time, ore particle size and reaction temperature on the amount of separated part and grade of the product were examined. It was found out that the hematite inside of ore could almost be completely converted into magnetite by stoichiometric ratio of coal to ore at the roasting temperature of 625 °C for 25 min. Under the optimum condition, a high amount of magnetic part of the product (72.22 wt%) with a grade of 92.7% was separated. The most important point in this process was prevention of reduced ore from re-oxidation reaction by controlling roasting atmosphere, time and temperature. In addition, different analytical methods such as X-ray fluorescence (XRF), X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG) and scanning electron microscopy (SEM) were applied to investigate and expound the results.
