Recently, the main iron ore futures contract has performed strongly in the market, with the intraday increase expanding to 4%. This fluctuation has not only attracted widespread attention, but has also forced people to be aware of the urgency of solving the problem of domestic iron ore resource security. China needs to enhance the supply of iron ore resources, and the utilization of low-grade and complex symbiotic mineral resources is an unavoidable task.
The global confirmed reserves of high-phosphorus iron ore exceed 20 billion tons, mainly distributed in countries such as Algeria, China, Kazakhstan, and Nigeria. Due to the abundant ooids, complex composition, fine-grained phosphorus mineral dissemination, low grade and high phosphorus content in this iron ore, it has been recognized by the global mining industry as a difficult-to-beneficiate ore. In China, high-phosphorus iron ore is known as “Ningxiang-type iron ore”, which is widely distributed in Hubei, Hunan, Jiangxi, Guizhou, Yunnan, Sichuan, Chongqing, and Gansu. For nearly a century, high-phosphorus iron ore has remained undeveloped globally.
Currently, the main dephosphorization methods are as follows:
1.Beneficiation dephosphorization: This method requires fine grinding of the ore until the phosphorus minerals and iron minerals are completelyseparated, and then magnetic roasting and magnetic separation, followed by reverse flotation or leaching dephosphorization. The main problems with this method are the high grinding cost due to the fine dissemination of phosphorus minerals in the iron ore, difficulties in product sedimentation and concentration, and low iron recovery rate due to the similar floatability of phosphorus and iron minerals.
2.Chemical dephosphorization: This method uses acid leaching to remove phosphorus. The advantage is that the phosphorus minerals do not need to be completely separated, but the disadvantages are high acid consumption, high cost, and dissolution of iron minerals, leading to iron losses. Although this process does not require fine grinding of the ore to separatethe minerals, the dephosphorization rate is high, but some iron will be dissolved, reducing the iron recovery rate. The MgO and CaO content in the iron concentrate will also decrease, reducing the basicity of the concentrate and affecting its self-fluxing properties, increasing the smelting cost. The large amount of acid used in the leaching process also causes significant environmental pollution.
3.Microbial dephosphorization: This method mainly uses metabolic acid production to lower the pH, thereby dissolving the phosphorus minerals. The metabolic acid also chelates with ions like Ca2+, Mg2+, and Al3+, promoting phosphorus dissolution. Although this process has the advantage of low environmental pollution, the bacteria required for the leaching process need to be collected, separated, cultured, and adapted, which is time-consuming and has a high production cost, making it relatively difficult to apply in practice.
4.Metallurgical dephosphorization: In 2009, a research team led by Professor Guo Zhancheng from the University of Science and Technology Beijing first proposed a gas-based reduction plus melting-separation for dephosphorization process, which has received widespread attention in the industry. This dephosphorization process breaks away from the traditional beneficiation dephosphorization approach and does not have a separate beneficiation step. The process can be summarized as: using hydrogen-based reduction to convert the original ore into DRI, and then conducting melting-separation for dephosphorization to produce qualified molten iron, followed by the conventional steelmaking and rolling processes. This integrated development approach not only significantly reduces the dephosphorization cost, but also greatly increases the added value of the final product, making the development of high-phosphorus iron ore economically feasible. This technology has been applied in the Gara Djebilet iron ore development project in southwestern Algeria, where laboratory-scale experiments with hundreds of kilograms and the first round of pilot-scale tests with tons of ore have achieved positive results. This technology has been applied for international patents.
The comprehensive development of high-phosphorus iron ore will help supplement China’s and the global iron ore resources. It is necessary to further increase the development of new processes for high-phosphorus iron ore and the research on new dephosphorization methods, to develop effective, economical, and practical new methods and new technologies. The in-depth research on innovative dephosphorization metallurgical processes will bring a turning point for the development of high-phosphorus iron ore.
