Mechanism of high temperature reduction on iron carbide preparation with low-grade siderite

The carburization roasting followed by magnetic separation is a feasible method to utilize low-grade siderite ore. In order to enhance the carburization efficiency and separation efficiency, high temperature reduction was carried out, and its mechanism was demonstrated by measuring carburization index, phase change, and microstructure under a carbon-sulfur infrared analyzer, an X-ray diffractometer, and a metallurgical microscope. The results show that both the carburization efficiency of siderite pellet and the separation efficiency of iron carbide from gangue are very low. However, high temperature reduction is a useful way to enhance the carburization efficiency, as it can accelerate the reduction reaction rate and carburization reaction rate. Furthermore, high temperature reduction can improve the growth of iron carbide particle, promote the carburization efficiency, and strengthen the sodium modification reactions, thereby greatly accelerating the separation efficiency of iron carbide and gangue. When the siderite pellets were reduced at 1050 °C for 90 min and carburized at 650 °C for 120 min, the carburization index of carburized pellets reached 36.06. After magnetic separation treatment, an electric furnace burden assaying 83.12 wt.% Fe and 6.96 wt.% C was prepared, and the corresponding iron recovery rate was 95.43%. The high temperature reduction is promisingly adopted to promote the utilization of low-grade siderite ores using carburization-magnetic separation technology.