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This is an article in the field of mining engineering. The effects of reducing agent and dephosphorization agent on the direct reduction of high phosphorus oolitic hematite were reviewed. The research status of the influence of reducing agents on the reduction of high-phosphorus oolitic hematite was summarized from two aspects of coal and other reducing agents, and the research progress of dephosphorizers was summarized from two ways of using single and combined dephosphorizers. The problems existing in the direct reduction-magnetic separation process of high-phosphorus oolitic hematite were pointed out. According to the existing problems, suggestions for the future research direction of direct reduction-magnetic separation of high-phosphorus oolitic hematite were put forward.

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The exploitation of refractory iron ores has become increasingly important around the world because of the rapid depletion of easy-to-process iron ores. Ironsand is extensively distributed in the coastal areas of Indonesia, China, and New Zealand, and can provide an alternative to conventional iron ores. Although the composition of ironsand is partially dependent on its location and position, it approximates that of titanomagnetite (Fe3-xTixO4) containing ~ 60% total Fe (TFe). However, the conventional smelting route for smelting beach titanomagnetite concentrate with carbon uses a blast furnace to produce pig iron and titanium slag, which has many disadvantages. First, the smelting process requires lots of coke and a high temperature. Second, sinter blend allows for the addition of only a small amount of beach titanomagnetite concentrate to ensure the desired sintering characteristics. Therefore, in order to efficiently utilize beach titanomagnetite, the processes of direct reduction followed by magnetic separation are generally applied to recover iron. In addition, additives such as CaO, CaCO3, and NaCO3 are often used in the reduction roasting process. These additives may improve the reduction characteristics or facilitate the growth of iron particles to some extent. In order to study the effect of the additive CaO on the direct reduction and magnetic separation of beach titanomagnetite concentrate which contains 58.58% of TFe and 12.04% of TiO2, the mechanisms were investigated by gas composition of CO and CO2, gasification rate of total reaction, CO partial pressure, metallization rate, mineral composition and so on. The results indicate that adding CaO can improve the gasification rate of reductant and facilitate the reduction of titanomagnetite, which improves the generation of CO2 gas and decreases the CO partial pressure. Besides, CaO can participate in solid-solid reaction, reduce FeO content in Ti-containing mineral and facilitate the migration and enrichment of Ti and Fe components, which promote the growth of metallic iron particles. Thus, adding CaO is good for the separation and recovery of Fe and Ti by grinding and magnetic separation.

Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application. [ABSTRACT FROM AUTHOR]