Multi-source ferrous metallurgical dust and sludge are significant components of iron-containing solid waste in the iron and steel industry. It is crucial for the sustainable operation of steel enterprises to recycle iron from ferrous metallurgical dust and sludge (FMDS) for use in steel smelting. However, besides Fe, FMDS also contains valuable elements such as Zn, Pb, K, and Na, among others. While these valuable elements hold high recovery value, they impede the direct reuse of FMDS by iron and steel enterprises. This paper introduces the compositional characteristics of multi-source ferrous metallurgical dust and sludge, analyzes the main recycling technologies associated with FMDS at the present stage of development, and discusses the characteristics of different technologies. In view of this, a new idea of the “cooperative treatment of multi-source ferrous metallurgical dust and sludge—full quantitative recovery of valuable elements” is put forward. This new idea integrates a variety of treatment processes to directly recycle FMDS within the steel plant, enhancing the adequacy of dust and sludge recovery and reducing the risk of environmental pollution. This paper provides a reference for achieving the full quantification and utilization of high-value-added FMDS in steel plants.

The forming of rings was a key problem of magnesian flux pellets in rotary kiln, which seriously limited production efficiency. Pellet powder and flux were the raw materials of the ring. Based on this, the bonding strength, melting behavior and microstructure of pellet powder and its mixed powder with flux were investigated. The influence of basicity (R = CaO/SiO₂) on ring behavior of pellet powder was analyzed, and ring formation mechanism of magnesian flux pellets was clarified. The results showed that acid pellet powder was not easy to form rings due to lower bonding strength of briquettes. Due to changes in bonding process after mixing of flux, magnesian flux pellet powder produced ferrite and silicate liquid phase with lower melting point, which promoted diffusion and recrystallization of hematite and enhanced compressive strength of briquettes, then finally caused rings to form. Moreover, it is required to control roasting temperature below 1200 °C, which is a necessary condition for magnesian flux pellet powder to form an initial ring which was easy to be destroyed.

Crystallization of molten blast furnace slag directly affects the fibre forming rate and stability of fibre. The single hot thermocouple technique was used to investigate the crystallization behaviour of modified blast furnace slag. The results revealed that, with increasing acidity coefficient of modified blast furnace slag during the isothermal process, the initial crystallization temperature of modified blast furnace slag gradually decreased, which were at 1390°C, 1330°C and 1180°C, respectively, and TTT curves changed from double C-type curve to single C-type curve. Through a continuous cooling process, the critical cooling rate decreased from 6°C s⁻¹ to 0.5°C s⁻¹ when the acidity coefficient of modified blast furnace slag increased from 1.05 to 1.40. Based on these findings, we conclude that, the crystal growth rate is controlled by diffusion driving force and undercooling driving force.

The crystallization and viscosity of modified blast furnace slag are key factors in fiber forming conditions. In this paper, the crystallization behavior of modified blast furnace slag under continuous cooling conditions was studied by differential scanning calorimetry, and its crystallization kinetics with different acidity coefficients were established. On this basis, the evolution law of the crystallization phase and the influence of crystallization on the viscosity of modified blast furnace slag with different acidity coefficients were analyzed. The results indicated that the crystallization phases of slag with acidity coefficients of 1.05 and 1.20 were, respectively, Melilite and Anorthite. During the cooling process at the acidity coefficient of 1.05, the critical rates of precipitation of Melilite and Anorthite were 50 °C/s and 20 °C/s, respectively, while they were 20 °C/s and 15 °C/s, respectively, at the acidity coefficient of 1.20. With the increase of the acidity coefficient, the crystal growth mode of slag changed from two-dimensional and three-dimensional mixed crystallization to surface nucleation and one-dimensional crystallization. The crystallization activation energy of slag with acidity coefficients of 1.05 and 1.20 were 698.14 kJ/mol and 1292.50 kJ/mol, respectively. In addition, the change trend of viscosity was related to crystal size and content.

The trivalent chromium (Cr) leached from stainless steel slag can be oxidized into hexavalent Cr with strong toxicity in the natural storage process, thus causing severe pollution to the surrounding soil, water, and atmosphere. Currently, the toxicity hazards caused by high Cr concentrations in plants, animals, and humans have attracted widespread attention from across the world. In this study, an overview is presented regarding the occurrence mode, leaching mechanism, and influencing factors for the presence of Cr in the soil of stainless steel slag under natural landfilling conditions. Meanwhile, a summary is made for the research progress in Cr absorption, transport, and accumulation in the soil–plant system. Besides, allowing for the toxicity and detrimental effect of Cr( vi ) in the soil as well as the application of biological and chemical methods for the remediation of Cr( vi )-contaminated soil, a review is conducted on the approach to recycling Cr from stainless steel slag and the application of chemical remediation and biological methods to remedy Cr-containing soil. Finally, a discussion is conducted about the transfer and transformation behavior of Cr in soil–plant system, the practical application of soil remediation technology and the prospect of research in this field.