Analysis of self-reducing composites with different iron ore-carbon ratio

Abstract

The use of self-reducing agglomerates with ferrous burden is considered a sustainable alternative for blast furnace reducing fuel consumption and increasing productivity of the equipment. In this work, self-reducing mixtures composed by different ratios of iron ore and carbon sources were evaluated concerning their reduction performance and the phases quantification. Non-coking coal (NCC) and petroleum coke (PC) were used as iron ore reducing agents and in different C:O molar ratio. Firstly, the reactivity to CO2 of each reductant was evaluated and then, thermogravimetric tests were carried out with the self-reducing mixtures in a non-isothermal regime and argon atmosphere up to 1300 °C. The phase contents were identified by X-ray diffractometry (XRD) and quantified via image analysis under an optical microscope. The thermogravimetric tests evidenced that the C:O molar ratio equal to 0.75, which is equivalent to 20% in mass of NCC and 15% in mass of PC in the mixture, achieved the highest reacted fraction. At lower reducing agent ratios, the greater content of metallic iron was obtained when PC was used in the mixture, indicating its better performance in comparison to the NCC. For both reducing agent, at 25% in mass of NCC or PC, a greater amount of carbonaceous particles was observed in the mixtures. It was evidenced that iron ore reduction happens through the formation of two main phases, fayalite and wustite. In addition, it was observed that the metallic iron presented a more porous morphology when NCC was used.