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

Abstract

• Steel slag was tried in wet flue gas desulfurization using a bubbling-bed reactor. • Kinetics of SO 2 absorption in steel slag slurry was studied. • The maximum SO 2 absorption capacity of the steel slag is 0.68g/g. • The Mn 4+ , Fe 3+ and Mg 2+ in steel slag promote the oxidation of SO 2 into SO 4 2− . • Mechanism of SO 2 absorption in steel slag slurry was also revealed. In this study, steel slag, a waste generated from steelmaking processes, was used as an absorbent for the removal of SO 2 in coal-fired flue gas. The results showed that SO 2 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 SO 2 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 SO 2 absorption process. Results also demonstrated that the maximum SO 2 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 SO 2 breakthrough time reaches the maximum of 951 min under a flow rate of 420 mL/min, an initial SO 2 concentration of 700 ppm, and a solid-liquid ratio of 1.5 g/100 mL. Moreover, it was found that SO 4 2− , 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 CO 2 emissions and solves environmental problems associated with the disposal of steel slag.