Carburization Behavior of Siderite Pellets in CO–CO₂–H₂ Mixtures

Abstract

Siderite is a complex and refractory iron ore, which is hard to be utilized in iron and steel industry nowadays. For the effective utilization of siderite, a study of the carburization behavior of siderite pellet is carried out to improve the preparation of iron carbide from siderite. Siderite pellets are carburized in CO-CO 2 -H 2 mixtures, and its carburization behaviors are demonstrated by measuring carbon content, phase change, and microstructure under X-ray diffraction (XRD), scanning electron microscope (SEM), and optical microscopy. The results show that high temperature favors to the reduction of siderite pellets, but it hinders the carburization of siderite pellet. The optimum carburization temperature is at the range of 600-650 C. At the early stage of carburization, the main reactions are the reduction of iron oxide, while the main reactions are the carburization of metallic iron at the late stage. At the middle stage, reduction and carburization reactions coexist. Carburization of roasted product of siderite pellet ranking from easiest to hardest is as follows: Fe>FeO>Fe 2 O 3 >Fe 3 O 4 . The study of carburization behavior of siderite pellet demonstrates that preparation of iron carbide from siderite is a feasible way.

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“…The iron content, recovery rate, and combined carbon content of the magnetic concentrate significantly increase with increase in the carburization temperature. Both the recovery rate and combined carbon content of the magnetic concentrate decrease beyond carburization temperatures of >650 C. It has been previously demonstrated by thermodynamic calculations [27] that higher temperature imposes a stronger adverse effect on carburization reactions. However, in the range of 550-650 C, higher temperature leads to the higher carburization rate, which enhances the carburization degree.…”

“…Owing to the high temperature, the carburization index decreases (Figure 12b); however, temperatures of >650 C can promote pellet reduction. [27] From Figure 13, we note that the diffraction peak intensity of Fe 3 C weakens. Furthermore, high temperatures enhance the growth of iron carbide particles (Figure 14).…”

“…It has been reported that alkali metal ions such as those of Na 2 SO 4 can significantly improve iron oxide reduction. [25,26] The high reduction rate can promote the carburization of siderite pellets, [27] which, in turn, affords an increase in the carburization efficiency (η) (Figure 3b 6), which improves the carburization process. These results show that the addition of Na 2 SO 4 promotes the carburization of the pellets.…”