5. Conclusions

reduction-magnetic separation technology for the development of complex refractory iron ore provides a new way to become one of the hot topics in the field of mineral processing in recent years. Raw materials of oolitic hematite, hematite with carbonate, iron tailings, red mud, Zincbearing iron ore were tested by this technic. After the magnetic separation, the deep reduced iron powder with 85–95% Fe and more than 90% recovery rate can be obtained [36]. Deep reduction temperature is generally higher than 1000�C, iron ore reduction process is Fe2O3 ! Fe3O4 ! FeO ! Fe. The process of reduction can be divided into three stages: initial, middle and late stage. The reaction kinetics models of each stage are Avrami-Erofeev equation, chemical reaction model and three-dimensional diffusion model, respectively. The size of the iron particles in the reduced material can be detected using optical microscopic image analysis techniques. It is noteworthy that the reduction temperature and the reduction time have a

High-phosphorus oolitic hematite is an important iron ore resource in China. Due to the extremely fine grain size (less than 10 μm) and high-phosphorus content of hematite, it is difficult to effectively classify the hematite by conventional beneficiation process. However, the deep reduction-magnetic separation process can be applied to high-phosphorus oolitic hematite iron enrichment. The study found that during the deep reduction process, the phosphate minerals in the ore will be reduced to elemental phosphorus, and a considerable part of the elemental phosphorus enters the metallic iron phase, causing high content of phosphorus in the reduced iron powder [37]. In response to this problem, relevant scholars put forward two solutions: deep reduction of dephosphorization and deep reduction of phosphorus-rich [12]. For the raw ore with phosphorus content less than 0.8%, by adding dephosphorization agent (Na2CO3, Ca (OH)2, Na2SO4, etc.) the vast majority of phosphorus remains in the slag phase. This way would get the low-phosphorus deep reduced iron powder (phosphorus content ≤ 0.05%) that can be directly used in steel-making [13]. For raw ore containing more than 0.8% phosphorus, by controlling the migration of phosphorus, more than 80% of the phosphorus enters the metallic iron phase. It would get high-phosphorus deep reduced iron powder (phosphorus content ≥ 1.5%), and then use smelting dephosphorization technology to deal with high-phosphorus iron powder, and qualified molten steel at the same time get high-phosphorus steel slag, the highphosphorus steel slag can be used directly as phosphate fertilizer or acid soil improver. Presently,

Other mineral processing and ore metallurgy technology would include the tailings reseparation technology and room temperature collector technology. [12] Due to the low grade of iron ore resources in China, an average of 1 ton of iron concentrates needs to be discharged to 2.5 tons of tailings. With the continuous increase of production capacity of mining enterprises, the discharge of iron tailings has rapidly increased and has become the largest industrial solid waste. Tailings discharge not only occupy a large amount of land, sometimes due to poor management, but also cause tailings dam break, resulting in casualties, environmental pollution, destruction of villages and towns and other serious consequences. The iron tailings usually contain a certain amount of metallic iron with a fine grain size, so the energy consumption of grinding is lower than that of raw ore. Anshan Iron and Steel Mining Company, Qidashan iron plant and Gongchangling beneficiation plant conducted flotation tailings re-separation pilot study. The

significant effect on the size distribution of iron particles [21].

18 Iron Ores and Iron Oxide Materials

this technic is not yet widely used because of lacking equipment.

4.5. Others

This chapter addresses the topic of iron ore types, structure of import, market analysis, financial aspects, overseas investments, etc. It also covers development of innovative beneficiation processes in China. Probably due to large national land area and multi-period orogeny, from the view of metallogeny, lots of iron deposits developed in China, and the proven total reserves of iron ores are relatively abundant, but mainly low-grade ores. For years, China's iron ore reserves are far from being able to meet the requirement of rapid development of steel industry. China is the world's largest importer of iron ore, which imports accounted for onethird of the world's total in recent decades; however, the buyer has not the final say. The strategic importance of iron ore resources in national economy not only depends on the social value and economic value created by the iron ore exploitation, but also depends on whether the requirements of the steel industry and steel downstream industry, and safety ensuring, economy and sustainability of steel and steel downstream industry. In order to improve the self-sufficiency rate of iron ore and get rid of the shackles of foreign mining giants, a great deal of research work has been carried out by relevant researchers around the efficient utilization of iron ore resources. In the process of fine iron ore beneficiation, ore crushing, roasting-magnetic separation, deep reduction, tailings re-election, low temperature collector research and development has made achievements.
