Experiment and Prediction Studies of Marine Exhaust Gas SO2 and Particle Removal Based on NaOH Solution with a U-Type Scrubber

Marine diesel engines produce exhaust gas including a lot of SO,, and particulate matter (PM), and laws have been promulgated to regulate ship exhaust emissions. This paper proposes a U-type exhaust gas cleaning (EGC) system that is capable of removing SO2 and particulate matter (PM) simultaneously. The purpose of this study was to find the relationships between removing efficiency and parameters of EGC system, then get the optimal structural and operational parameters. The experimental results show that the SO2 absorption rate in the scrubber was mainly influenced by liquid gas ratio, pH value, and temperature in the range of experimental operating conditions. With the system stable running, when the liquid gas ratio and temperature were determined, the pH value must be in a fixed range of 6.5-7.5. The further research was also carried on for the EGC system applicable to ships. On the basis of SO2 removal efficiency, the prediction and experimental validation of particulate matter (PM) were studied. When comparing the results of prediction and experiment, the data show good agreement. PM removal efficiency was related to liquid gas ratio, droplet size, and height of chamber. The height of spray chamber was the key structure factor, and the droplet size was the operational parameter affecting PM removing efficiency. The increasing of liquid gas ratio both could lead to an increase in the SO2 and PM removal efficiencies. Thus, according to this study, the usage of EGC system can removed SO2 and PM at same time, and it can satisfy future ships emissions regulations. The theoretical analysis and experimental results of scrubber can be extended to apply in marine exhaust gas after-treatment technologies.