Study on Characteristics of Steel Slag for CO₂ Capture

Steel slag is a kind of alkaline mixture and considered to be a potential CO 2 adsorbent. In this work, the CO 2 -trapping characteristics of two types of steel slag, basic oxygen furnace (BOF) steel slag and electric arc furnace (EAF) steel slag, were experimentally investigated. Generally, the higher the temperature, the larger the Ca use of slag. However, the Ca use at 550 °C would be lower than that at 500 °C for a certain CO 2 concentration. The CO 2 concentration also has an effect on the Ca use. At higher temperatures, a larger Ca use appears at a lower CO 2 concentration (<10%) or higher CO 2 concentration (>75%). As the CO 2 concentration decreases, the reaction rate of carbonization increases, regardless of the kind of slag used. With regard to the type of steel slag, EAF steel slag is better than BOF steel slag in reactivity and Ca use. All of the results indicate that the carbonation reaction of steel slag is controlled by not only the reaction kinetics but also the diffusion of the reactive gas CO 2 . Steel slag has a capacity to capture and permanently sequester CO 2 . However, what is more important is that it can be used in different flue gases, where the CO 2 concentration is typically lower (<20%) or fairly higher (>75%). This provides the steel slag a wide application market.