Steam Efficiently Enhancing CO₂ Direct Mineralization Steel Slag Towards Actual Production: Phase Evolution,...

Area of Science:

• Materials Science and Engineering
• Environmental Science and Technology
• Chemical Engineering

Background:

• Steel slag is a major industrial solid waste in China, with low utilization rates due to the presence of unreacted free calcium oxide (f-CaO).
• Existing carbonation methods like indirect wet mineralization are difficult to scale, while direct dry carbonation is energy-intensive and slow.

Purpose of the Study:

• To develop an efficient and industrially viable method for steel slag carbonation and utilization.
• To investigate the synergistic effect of steam and CO2 on direct steel slag mineralization.
• To assess the potential for waste heat recovery and flue gas utilization in the process.

Main Methods:

• Direct mineralization of steel slag using a combination of steam and carbon dioxide (CO2).
• Utilizing waste heat from hot steel slag for the reaction temperature, eliminating external heat sources.
• Investigating the impact of steam injection (15%) and varying CO2 concentrations on mineralization efficiency and carbon fixation.

Main Results:

• Achieved a CaCO3 content of 12.02 g/100 g, corresponding to 52.8 kg CO2 utilization per ton of slag, a 16.7% improvement.
• Reduced f-CaO content to 0.61%, with 91.73% of f-CaO mineralized and a 20.24% increase in mineralization efficiency.
• Demonstrated effective carbon fixation even at 20% CO2 concentration, achieving 69.90% of the efficiency at 100% CO2.

Conclusions:

• Steam-assisted CO2 mineralization is a highly effective method for stabilizing steel slag and enhancing its utilization.
• The process leverages waste heat and can utilize low-concentration CO2, making it suitable for large-scale industrial application.
• This approach offers a sustainable solution for industrial solid waste management, reducing CO2 emissions and promoting circular economy principles.