Utilization of steel slag as a highly efficient absorbent for SO₂ removal at coal-fired power stations

In this study, steel slag, a waste generated from steelmaking processes, was used as an absorbent for the removal of SO₂ in coal-fired flue gas. The results showed that SO₂ could be removed completely in the bubbling-bed reactor by the steel slag slurry under certain operating conditions. Effort was then made to study the kinetics of SO₂ absorption in steel slag slurry. It is found that the gas-liquid absorption model fits well with the experimental data and can be used to predict the SO₂ absorption process. Results also demonstrated that the maximum SO₂ uptake capacity of steel slag reaches 0.68 g, which is about 36 wt% higher than that of the traditional limestone-gypsum desulfurization process under similar conditions, while the SO₂ breakthrough time reaches the maximum of 951 min under a flow rate of 420 mL/min, an initial SO₂ concentration of 700 ppm, and a solid-liquid ratio of 1.5 g/100 mL. Moreover, it was found that SO₄²⁻, was the main anions detected in the liquid phase after desulphurization and the pH of the solution decreased from 12.9 to 3.2. This study proved that steel slag is of the potential to replace limestone in the wet flue gas desulfurization process, which contributes to the mitigation of global CO₂ emissions and solves environmental problems associated with the disposal of steel slag.