Introduction to the research on the physicochemical and utilization technology of Japanese iron slag

　　Physical and Chemical Study of Iron and Steel Slag

　　The following introduces the research on slag with dephosphorization reaction as the center.

　　To reduce the amount of slag generated, it is necessary to improve refining capacity and efficiency, and increase the utilization efficiency of lime. This requires slag design and process design that reduces the amount of slag generated while ensuring refining capacity.

　　In the dephosphorization reaction, phosphorus enters the molten slag in the form of phosphate ions. As an indicator of the slag's ability to absorb phosphorus, the phosphate capacity (CPO3-4) is proposed. According to the operating conditions, CPO3-4 can be used to evaluate the dephosphorization reaction.

　　In practical operation, refining with non-uniform liquid phase solid CaO and its solid compounds coexisting with liquid-phase slag as a flux requires improving the utilization efficiency of the solid phase in the slag. The co existing solid liquid phase fluxing agent is named "multi phase fluxing agent", and the effective utilization of the solid phase coexisting with the molten slag in the refining reaction has been studied.

　　In practical operation, refining slag is refined through the coexistence of solid-liquid slag. At the processing temperature of molten iron, 2CaO · SiO2-3CaO · P2O5 forms a solid solution. Consider utilizing this by introducing phosphorus as an oxide into the solid solution, effectively utilizing the solid-phase CaO.

　　Waseda University's Ito Takahisa predicted the effect of multiphase slag dephosphorization: when the phosphorus concentration in the molten steel is reduced from 0.1% to 0.01%, the phosphorus in the molten steel completely enters the calcium phosphate compound phase, which can significantly reduce the unit consumption of CaO.

　　The reaction mechanism of CaO slag interface was studied by immersing solid CaO in slag, further elucidating the thermodynamic properties of solid solutions containing phosphorylates.

　　Research on the Utilization Technology of Iron and Steel Slag

　　Iron slag is a byproduct of modern ironmaking processes using iron ore and coal as raw materials. Therefore, it is necessary to develop technologies that utilize iron slag as a resource and endow it with new functions.

　　So far, iron steel slag has been widely used as a cement raw material, concrete aggregate, roadbed material, marine harbor civil engineering material, fertilizer, soil improvement material, etc. In addition, research on the use of steel slag as a recycled material in coastal rural areas affected by the Great East Japan Earthquake has achieved results. Recently, various studies have been conducted on the recycling and utilization of phosphorus as a resource.

　　In terms of the development of technology for the utilization of iron and steel slag, the Japanese produced iron and steel research project "Development of Technology for the Utilization of Steel Slag as a Marine Environmental Remediation Material in the Marine Field" has conducted research on the utilization of steel slag in marine areas. Due to the lack of organic acids and iron ions, desertification is occurring in this marine area. The reaction between rivers and humic acid flowing from terrestrial forests generates iron chelates, which absorb iron ions from marine plants. The presence of iron ions plays an important role. Therefore, as a stable supply material for iron ions, the utilization of steel slag as a marine environmental remediation material in harbor and marine areas was studied using slag, organic acids, and dredged soil.

　　Researchers have investigated the effect of leaching conditions on the leaching behavior of various elements from steelmaking slag into seawater, clarifying the influence of organic acids on the leaching behavior of steelmaking slag elements in seawater, the influence of dredged soil, the influence of slag carbonation, and the continuous leaching behavior of steelmaking slag.