Study on seawater scrubbing for SO2 removal from ship’s power plant exhaust gas

The mechanism of SO2 absorption in seawater is investigated, and the experiment was carried out accordingly. Emphasis is on applications of seawater scrubbing of ship's power plant exhaust gas containing SO2. The formulated model is used to predict the influence of various parameters on both pH of tailwater and seawater desulfurization capability, e.g., the partial pressure of SO2, the partial pressure of CO2, tailwater temperature, pH and alkalinity of seawater. Experiment results indicated that the seawater desulfurization capacity increases with both increasing partial pressure of SO2, pH and alkalinity and decreasing partial pressure of CO2 and temperature. The study shows the desulfurization capacity of seawater with 3.5% salinity is approximately twice that of freshwater. Different scenarios in which the required absorbent supply rate for a given SO2 removal efficiency are studied. It is observed a 97% removal efficiency, corresponding to meeting the SOx limits in the SOx emission control areas (SECA) while operating on a heavy fuel oil containing sulfur 3.5 wt. %, requires a minimum water supply rate of 0.0407–0.0683 m3 /kWh, depending mainly on the water composition in terms of alkalinity and salinity. Such data are important in assessing the operation cost of the water scrubbing system.