Steel metallurgical dust, characterized by a substantial output, minute particle size, and intricate composition, poses a considerable risk of environmental contamination while simultaneously embodying an exceptionally high potential for recycling. To achieve its resource utilization, chemical analysis, particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy, and water leaching methods were employed to investigate the chemical compositions, particle size distributions, phase compositions, and microscopic morphologies of blast furnace bag dust, sintering dust, converter fine dust, and electric arc furnace dust from steel plants. The results indicate that the four types of dust have extremely fine particle sizes, with the main distribution range of particle size being less than 100 μm. The main constituent element is Fe (19–56%), and it also contains Zn (1.4–33.5%), Pb, K, C, and other valuable elements. Alkali metals in blast furnace bag dust and sintering machine head dust existed mainly in the form of chloride. The zinc phases in sintering machine head dust and converter fine dust were ZnFe₂O₄, and the zinc phases in blast furnace bag dust were ZnCl₂ and ZnFe₂O₄. Zinc in electric furnace dust was composed of ZnO and ZnFe₂O₄, accounting for 70.31% and 23.12%, respectively. There are significant differences in the types and contents of valuable elements among various dusts, making it difficult to achieve full-scale recovery through a single process. In view of this, a process of “in-plant recycling of harmless dusts—collaborative treatment of harmful dusts” has been proposed. Based on the characteristics of metallurgical dusts, multiple processes are used for collaborative treatment (using hydrometallurgical and pyrometallurgical methods), which can not only directly recover iron resources from dusts within the plant, but also avoid the waste of valuable elements such as Zn, Pb, K, Na, etc. It is hoped that the above work can provide a reference for steel enterprises to achieve full-scale and high value-added treatment of metallurgical dusts.

Hydrodesulfurization (HDS) is a critical technology for producing clean petroleum products. With the steady growth in annual crude oil processing volumes, the consumption of HDS catalysts has been continuously increasing. The massive release of spent catalysts imposes significant pressure on both the environmental compliance and sustainable operation of companies. Spent HDS catalysts contain relatively high concentrations of valuable metals such as Mo, Ni, V, and Co. These materials are toxic and harmful heavy metal pollutants, yet they also constitute an important secondary resource of strategic metals with extremely high recycling value. Based on a systematic comparison of relevant recovery technologies, this paper reviews the current status of valuable metal recovery from spent HDS catalysts. It summarizes typical process routes for the full-component recovery of valuable metals and discusses future research directions, with the aim of providing a theoretical reference for the high-value resource utilization of spent HDS catalysts.

Blast furnace slag (BFS) is a by-product generated during iron-making process. The recovery of BFS for slag fibre production can efficiently utilise its latent heat. The crystallisation of BFS during cooling process would reduce fibre strength and induce fibre fracture. In this study, fly ash was employed to modified BFS. The effect of fly ash addition content on the crystallisation behaviour of BFS during cooling process was investigated using single hot thermocouple technique (SHTT). Time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) curves were constructed based on SHTT analysis. The obtained results indicated that the increase in fly ash content from 5 wt-% to 25 wt-% enhanced slag viscosity, decreased crystallisation onset temperature from 1300 °C to below 1000 °C, and reduced critical cooling rate from 180 °C/min to below 5 °C/min. The activation energies for the crystallisation of melilite and anorthite phase were 369 kJ/mol and 489 kJ/mol, respectively, in the modified BFS with fly ash content of 5 wt-%. Increasing fly ash content to 10 wt-% enhanced activation energy for anorthite phase crystallisation to 585 kJ/mol. Adding fly ash inhibits the crystallisation of BFS and makes the amorphisation of BFS is easier to control, which is beneficial to slag fibre production. The 15 wt-% fly ash modified BFS with the highest temperature window of 131 °C, crystallisation onset temperature of 1100 °C, and a critical cooling rate of 30 °C/min is most suitable for slag fibre production.

In this study, the high carbon content of blast furnace dust was utilised to replace coal in the removal of Zn from electric arc furnace dust. Additionally, converter dust was added to adjust the composition of the mixed dust to achieve synergistic disposal of multisource metallurgical dusts. The influence of roasting temperature, duration, and raw material ratio on the treatment efficiency of this co-processing approach was investigated through carbothermic reduction experiments. By comparing the metallization rate, dezincification rate, and residual carbon content of the products, the preferred experimental conditions were determined as using mixed Zn-containing dust having a C/O molar ratio of 1.0 and Zn content lower than 16.5%, roasted at 1150°C for 30 min. Under these conditions, the achieved metallization rate reached 94.99% and dezincification rate reached 99.54%. This multisource metallurgical dust synergistic treatment method can reduce coal consumption by about 0.2 t for every 1 t of mixed dust treated. Kinetic analysis of the reaction process showed that the average activation energy for the co-reduction of the metallurgical dusts was 66.41 kJ/mol. The reaction was found to be relatively easy. The initial stage of the reaction was controlled by interfacial chemistry, and the final stage transitioned to diffusion control.