硅热法热态镁渣干法固碳的可行性研究

Silicothermic reduction process is the main production process of magnesium in China. During every production of 1 t magnesium, nearly 5 t CO₂ will be directly emitted from the calcination process, and nearly 6 t powdered magnesium will be generated from the reduction process. However, there still lacks a large-scale and cost-effective technology to reduce carbon emissions and treat magnesium slag in an environmental way. Here this work proposed that, by taking advantage of the high-temperature environment in silicothermic system, the basic magnesium slag can react with acidic CO₂, bringing multiple effects such as utilization of releasing reaction heat, capturing CO₂, and reducing the pH value of slag leachate. The results show that this work first conducts thermodynamic calculations to confirm the feasibility of the proposed approach. Then, by designing and constructing an experimental apparatus, it is found that, introducing flowing CO₂ into the hot magnesium slag can indeed achieve the desired effects of carbon capture and pH reduction, as well as releasing significant amounts of heat during the reaction process. For example, at a reaction temperature of 850 ℃, the carbonization degree can reach 14%, and the pH value of magnesium slag can be reduced from 11.76 to 10.57, and nearly 40% of the slag not being powdered.