Magnetic Properties and Washability of Roasted Suspended Siderite Ores

Abstract

Steel is one of the most important industrial materials, which mainly comes from the smelting of iron ore. In view of the huge steel consumption every year, the exploitation of vast reserves of siderite ores is significant for improving the self-sufficiency rate of iron ore resources and ensuring the strategic security of the iron and steel industries. This paper investigated the influence of temperature, time, and other parameters on the magnetic properties of roasted siderite ores using the method of suspended roasting and analyzed the washability of roasted ores under weak-magnetic-field conditions using the magnetic separation tube experiment. The findings of the study explained the iron phase transformation process, i.e., FeCO3 was transformed into Fe3O4 by suspension magnetization roasting. Furthermore, the saturation magnetization of the roasted ore increased in due time at a constant temperature range of 550–750 °C and a roasting time of less than 5 s. It also increased with increasing temperature and constant time. The roasted ore achieved the best magnetic characteristics after roasting at 750 °C for 5 s. After low-intensity magnetic separation, the iron grade of the concentrate changed to 55.12%, with a recovery rate of 90.34%. The study results provide a reference for the development and application of siderite suspension magnetization roasting technology.

Pilot Study on a New Conveyor Bed Magnetization Roasting Process for Efficient Iron Extraction from Low-Grade Siderite

“…The iron mineral transformation pattern, reaction kinetics, and magnetic separation of siderite by magnetization roasting have been systematically investigated in previous studies [2][3][4][5]. These results confirmed that siderite could be efficiently magnetized by calcination at 600-800 • C for 3-10 s in a reducing atmosphere, and magnetite could be effectively collected by the multiprocess weak magnetic separation method [7,[11][12][13]. Existing studies have confirmed the feasibility and advantages of suspended-state magnetization roasting technology (e.g., fast reaction, good magnetization effect, mature process equipment, etc.).…”

“…When the roasting temperature was >750 • C, an increase in the roasting temperature caused the magnetite diffraction peak in intensity to decrease slightly. When the roasting temperature was 800 • C, FeO was detected in the roasted ore, indicating that the overreduction was responsible for decreased magnetite content [11]. As shown in Figure 5, FeCO3 and white mica underwent noticeable decomposition reactions after magnetization roasting, whereas quartz showed no obvious changes.…”

“…When the roasting temperature was >750 °C, an increase in the roasting temperature caused the magnetite diffraction peak in intensity to decrease slightly. When the roasting temperature was 800 °C, FeO was detected in the roasted ore, indicating that the overreduction was responsible for decreased magnetite content [11].…”

“…Therefore, a reasonable approach is to use dry cooling to avoid these problems [17]. For powdered materials, a suitable medium for efficient dry cooling is gas; however, the introduction of air cooling that leads to magnetite oxidation is an issue [2,4,7,11,13]. Recently, much research has been carried out on dry cooling technology; their results have confirmed that if the dry cooling rate is fast enough, the magnetite can directly cross the oxidation reaction stage, and their oxidation can be prevented [18].…”

“…This finding provided the foundation for the development of the dry cooling process, which led to the introduction of multi-stage suspension cooling units that recirculate most of the very low oxygen content exhaust gas into the cooling unit, thereby reducing oxidation. Although the conveyor bed magnetization roasting-dry cooling process system is theoretically and fundamentally feasible, its intrinsic laws and practical application in large-scale production have to be studied and demonstrated in-depth [7,11,13].…”