High-Efficiency Iron Extraction from Low-Grade Siderite via a Conveyor Bed Magnetization Roasting–Magnetic Separation Process: Kinetics Research and Applications

Abstract

Upgrading and utilizing low-grade iron ore is of great practical importance to improve the strategic security of the iron ore resource supply. In this study, a thermal analysis–infrared (IR) analysis–in-situ IR method was used to investigate the reaction mechanism and kinetics of Daxigou siderite. Experiments were conducted using a conveyor bed magnetization roasting process (CBMRP) to investigate the magnetization of siderite. Multi-stage magnetic separation processes were adopted to extract magnetite. The results show that simultaneously the iron carbonate in siderite decomposes, and magnetite is formed between 364 °C and 590 °C under both inert and reducing atmospheres. The activation energy of the magnetization roasting reaction is 106.1 kJ/mol, consistent with a random nucleation and growth reaction mechanism. Magnetization roasting at 750–780 °C for approximately 3.5 s in the CBMRP results in a magnetic conversion rate of >0.99% of the iron minerals in the siderite. A beneficiation process of one roughing, one sweeping, and three cleaning processes was adopted. A dissociation particle size of −400 mesh accounting for 94.78%, a concentrate iron grade of 62.8 wt.%, and a recovery of 68.83% can be obtained. Overall, a theoretical and experimental basis is presented for the comprehensive utilization of low-grade siderite.

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.).…”

“…Extensive technical research and development confirmed that the Daxigou iron ore has a considerable development value; however, successful large-scale industrial production has not yet been achieved [5,6]. A process system was developed for the magnetization roasting of siderite based on suspended-state calcination technology, and a 10,000-ton pilot plant was built for this purpose [7]. As this technology is crucial to the comprehensive utilization of siderite, conducting research on pilot-scale process technology is necessary to apply it industrially [8][9][10].…”

“…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].…”