Use of Seawater Scrubbing for SO 2 Removal from Marine Engine Exhaust Gas

The mechanism of SO 2 absorption in seawater is treated. Emphasis is on applications of scrubbing of marine engine exhaust gas containing SO 2 . The formulated model is used to predict the influence of various parameters on SO 2 absorption efficiency, e.g., seawater temperature, partial pressure of SO 2, seawater salinity, and seawater alkalinity. It is found that the absorption capacity of standard seawater is approximately twice that of brackish water with close to zero salinity. The absorption capacity decreases with both decreasing salinity and alkalinity. Different scenarios in which the required water supply rate for a given SO 2 cleaning efficiency is calculated. It is found that a 66% cleaning efficiency, corresponding to meeting the limits of SO x emission control areas (SECA) when operating on a fuel containing 4.5% w/w sulfur, requires a minimun water supply rate of 40–63 kg/(kW h) depending on the seawater composition in terms of salinity and alkalinity. Such data are essential in judging the operating cost of seawater scrubbing compared to alternative methods.