Slag treatment process, current situation and utilization value
Source:cronus
Posted:2025-12-19 16:52:57
Steel slag discharge accounts for 10% to 15% of crude steel output, and currently about 70% is in a state of stockpiling and landfill. Resource utilization can not only recover valuable metals but also reduce the environmental burden. The core lies in the efficient and environmentally friendly utilization of tailings and the rapid and economic decomposition of free calcium oxide (f-CaO) and free magnesium oxide (f-MgO). Steel slag treatment is divided into two stages: the primary treatment converts the molten state into a solid state, and the secondary treatment covers the sorting, processing and magnetic separation of solid steel slag and slag steel, etc. This article elaborates from four dimensions: the industry development environment, primary and secondary treatment processes, and the utilization value of tailings.
I. Development Environment of the Steel Slag Treatment Industry
The global requirements for pollutant emissions from steel slag treatment are becoming increasingly strict, and traditional highly polluting processes need to be transformed and upgraded. Converter steelmaking is the mainstream process. Electric furnace steelmaking is developing towards converter steelmaking, with the iron-water ratio reaching 70%. The "low-slag smelting" process in the converter steelmaking field can recycle steel slag and significantly reduce the content of free calcium oxide (5.7% in conventional smelting vs. 2.1% in low-slag smelting), which has a highly promoting effect on resource utilization.
Ii. Primary Treatment process for steel slag
The mainstream primary treatment processes are divided into hot-braising decomposition method (including hot-braising method, hot-pouring method, shallow plate method) and mechanical crushing method (water quenching method, air quenching method, drum method, etc.). The former achieves crushing and granulation by the volume expansion of alkaline oxides reacting with water at high temperatures, while the latter breaks molten steel slag by mechanical external force impact. The application data of large and medium-sized steel mills around the world shows that the hot-braising method (45.73%) and the improved hot-pouring method (39.53%) are the main processes. Although the application proportion of the drum method is only 7.75%, it is widely used in internationally renowned steel mills due to its advantages of high efficiency and environmental protection.
Iii. Current Situation of Secondary Treatment Process for Steel Slag
The secondary treatment process includes water washing of concentrate iron powder, pellet purification of concentrate iron powder, and recovery of slag steel, etc. It has been upgraded from the early simple crushing and screening to a multi-stage crushing, screening and magnetic separation combined mode. The core goal is to fully recover the metal components and efficiently utilize the tail material. However, the increase in processes will lead to an exponential growth in costs. Fine crushing and grinding equipment have been widely applied. Mechanical processing can refine the particle size of steel slag and reduce equipment investment costs.
Iv. Analysis of the Utilization Value of Steel Slag Tailings
(1) Application directions of tailings
Steel slag tailings have diverse applications: anti-slip pavement materials, metallurgical fluxes, etc. are high value-added fields, but the market consumption is limited. The asphalt surface layer/base layer has a relatively high added value and a moderate consumption. As an asphalt aggregate with average added value but huge demand, it is the core development direction.
(II) Current Application Status of Tailings
Global research on the application of tailings is extensive, with the mainstream direction being the production of steel slag powder and steel slag composite powder. The application of tailings is restricted by standards such as the content of free calcium oxide. Currently, some enterprises have achieved large-scale production, and the products are applied in fields such as asphalt pavement, road base, and concrete preparation. The dosage of steel slag powder in concrete can reach 15% to 30%. It is also applied in artificial reefs, the preparation of high-grade cement, etc.
