Simulation of SO2 removal process from marine exhaust gas by hybrid exhaust gas cleaning systems (EGCS) using seawater and magnesium-based absorbent

Abstract

Exhaust gas from navigation is an important source of air pollution, especially in coastal and port cities. The installation of a hybrid exhaust gas cleaning system (EGCS) is a popular method to reduce the SO2 emission because of their flexibility and efficiency. However, limited by the experience of operators, the operation of EGCS can hardly meet the requirement of economy and safety demands. In this paper, a detailed model of hybrid EGCS is developed to study the effect of important factors on SO2 absorption process and crystallization process. A comparison between seawater and magnesium-based absorbent on the SO2 absorption process in the droplet and the scrubber is carried out. Compared with seawater, magnesium-based absorbents are more adaptable to temperature and the SO2 concentration. What’s more, in order to prevent the EGCS from scaling and ensure the safe operation of EGCS, the safe operating ranges of magnesium-based absorbent under different temperature and oxidation rate are studied. Finally, an operation strategy of the EGCS for different absorbents is proposed. The operator can adjust the liquid-gas ratio of the current operating mode or switch to other modes according to the temperature and pH of seawater and emission standard. These results would be helpful for the design and the operation of the EGCS.