Difference of flue gas desulfurization performance and desulfurization mechanism of steel slag obtained under various cooling methods

Abstract

Steel slag has excellent desulfurization capacity due to its high content of alkaline. However, the current researches mainly focus on the desulfurization rate, and there is no report on the desulfurization capacity of steel slag and influence of steel slag cooling methods on desulfurization. In this paper, the difference of flue gas desulfurization performance of steel slag under three cooling methods (chilling, natural-cooling and low-cooling) were discussed through the variation patterns of pH, desulfurization rate and sulfur capacity in the desulfurization process. The order of desulfurization efficiency of steel slag with different cooling methods was chilling > natural-cooling > low-cooling. Subsequently, the desulfurization mechanism was investigated by comparing the elemental distribution and phase composition of raw materials and desulfurization products, as well as the cation analysis of the desulfurization solution. The alkaline elements Ca, Mg, Mn, and Fe in the chilled steel slag were located in the glass phase, and of them dissociated during the process of flue gas desulfurization, which was the fundamental reason for the efficient flue gas desulfurization capacity. Finally, the flue gas desulfurization performance of chilled steel slag and widely used CaO and CaCO3 were compared, and the flue gas desulfurization capacity of sharply chilled steel slag was slightly higher than that of CaCO3. Therefore, the steel slag obtained by chilling method can replace limestone, which is more friendly to the environment.