St. Petersburg Mining University (St. Petersburg, Russia).

Khalifa A. A., Postgraduate Student
Bazhin V. Yu., Head of Chair, Doctor of Engineering Sciences, Professor, bazhin_vyu@pers.spmi.ru
Ustinova Ya. V., Associate Professor, Candidate of Engineering Sciences, Kuskova_YaV@pers.spmi.ru

Central Metallurgical Research and Development Institute (Cairo, Egypt):
Shalabi M. E. H., Head of Laboratory, Candidate of Engineering Sciences

The use of red mud as an alternative raw material for the production of iron and steel has been studied for several decades. The proposed methods for its disposal are not widely used in the industry. The fine particle sizes and the large amount of impurities negatively affect the properties of red mud pellets and its direct reduction. The proposed method for the direct reduction of slime using coal with the addition of bentonite as a binder allows obtaining high-strength pellets with reduced iron. The effect of temperature, pellet and coal particle sizes at their different ratios on the reduction rates has been studied. The transformation of the iron phases has been analyzed by the X-ray diffraction (XRD) analysis method. The results indicate that the increased compressive strength of the red mud and coal composite pellets is explained by the higher bentonite content. The optimal conditions for pelletizing red mud with coal include the 2 % bentonite and 15 % moisture content. The reduction rate increases rapidly with higher temperatures and is more intense in the range of 1050 to 1100 °C. The pellet reduction processes with the particle size of red mud and coke fines in the range of 45 to 75 μm are much faster than in any other case. At 1100 °C, pellets with the carbon to oxygen molar ratio of 1 : 1 demonstrate a good reducing ability, with metallic iron becoming the dominant phase in the reduced samples. The reduction degree in the product reached 80.02 %, which is confirmed by the results of the X-ray structural analysis. The proposed technology, therefore, ensures the required conditions for obtaining high-strength pellets with a significant content of reduced iron, which creates good prospects for their further use as a charge material in blast-furnace smelting.

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