The phosphates of rare earth (RE) metals are highly stable in natural environment, and RE oxides have higher optical basicity than CaO and BaO. Therefore, the thermodynamic conditions for dephosphorisation using RE oxide-containing slags are expected to be favourable. Factors influencing the efficiency and Mn loss during the dephosphorisation of ferromanganese using RE oxide-containing slags were studied. An increase in the dephosphorisation temperature up to 1673 K (1400°C) is beneficial to the process and decreases Mn loss, and the maximum degree of dephosphorisation for slags containing 6 wt% RE oxides are 47.44 and 50.85%, corresponding to the minimum values of Mn loss are 1.64 and 1.35% at 1673 K (1400°C); further temperature increases would deteriorate the dephosphorisation efficiency and lead to an obvious increase in Mn loss. An increase in the quantity of pre-melted slags, and of their RE oxide content, improves the dephosphorisation efficiency but inevitably leads to a more pronounced Mn loss. It was also found that an increase in Si contents above 0.25 wt% in the ferromanganese alloys not only deteriorates the dephosphorisation efficiency but also increases the Mn loss; and the dephosphorisation efficiency decreases to almost zero when the silicon content increases up to 0.62 wt%.

In this paper, factors influencing the phosphorus distribution ratio between RE oxides containing slags and ferromanganese were studied. The results demonstrated that phosphorus distribution ratio values between RE oxides containing slags and ferromanganese are higher than those between CaO-based slags and ferromanganese. An increase in the temperature leads to a decrease in the phosphorus distribution ratio, and the downward trend is more pronounced when the temperature increases above 1673 K (1400°C). An increase of RE oxide content in the pre-melted slags, and of the oxygen partial pressure of the experimental system, improves the phosphorus distribution ratio. It was also found that when the Si content is below 0.25 wt-%, there is almost no change in the phosphorus distribution ratio; however, the phosphorus distribution ratio decreases as the Si contents increases further.

The traditional blast furnace ironmaking process is the most widely used ironmaking process globally, yet it is associated with significant drawbacks, including high energy consumption and carbon emissions. To achieve low-carbon ironmaking, researchers have developed hydrogen ironmaking, which is capable of achieving lower CO₂ emissions. Nevertheless, the distribution behavior of impurities has been less studied in the existing research on hydrogen ironmaking. Therefore, in this study, the factors affecting the slag properties and distribution of impurity elements during hydrogen ironmaking were investigated using FactSage, and smelting experiments were carried out. The results show that temperature has the greatest influence on the distribution behavior of the impurities, and excessively elevated temperatures result in the ingress of a significant quantity of impurities into the reduced iron. Reduced iron with a purity of 98.52% was obtained under the conditions of 10%, 10%, 2%, and 2% ratios of CaO, SiO₂, MgO, and Al₂O₃, respectively, a hydrogen flow rate of 12 mL/min, and a temperature of 1400 °C; Lg L Mg, Lg L Al, Lg L Si, and Lg L Ca were 2.72, 2.41, 3.36, and 2.45, respectively (“L” stands for slag-to-metal ratio). The slag was mainly dominated by the silicate, and the iron was mainly lost in the form of mechanical inclusions in the slag. This study will enrich the basic theory of hydrogen ironmaking and is of great significance for the realization of carbon neutralization.