A Novel Method for Simultaneous Removal of NO and SO2 from Marine Exhaust Gas via In-Site Combination of Ozone Oxidation and Wet Scrubbing Absorption

Zhitao Han,Xinxiang Pan,Tianyu Zou,Junming Wang,Jingming Dong,Yangbo Deng

doi:10.3390/jmse8110943

Abstract

The stringent international regulations on marine emission abatement have exerted a huge push on the development of marine desulfurization and denitrification technologies. However, for the traditional vessels driven by large two-stroke diesel engines, simultaneous removal of NOx and SO2 is still a big challenge at present. Here, a one-stage ozone oxidation combined with in-situ wet scrubbing for simultaneous removal of NO and SO2 is proposed. A series of experiments were performed based on a bench-scale reaction system. The results showed that in-situ wet scrubbing could effectively decrease flue gas temperature, and then suppress the thermal decomposition of ozone, which was beneficial for improve oxidant utilization. Meanwhile, the in-situ combination of ozone injection and wet scrubbing was in favor of improving the selectivity oxidation of NO over SO2 by ozone, which was possibly due to the high aqueous solubility of SO2 in water. Aiming to reduce the electric power consumption by an ozone generating system, O3/NO molar ratio was kept as low as possible. A complete removal of SO2 and a high NOx removal efficiency could be achieved through the introduction of other oxidative additives in scrubbing solution. This integrated system designed for marine application was of great significance.

Highlights

Stringent regulations on marine gaseous pollutant emissions have come into force in recent years [1]
Zhang et al conducted in a pilot-scale photochemical spraying tower to investigate the simultaneous removal of SO2 and NO from flue gas using H2O2/urea activated by vacuum ultraviolet (VUV) light, and the results showed that SO2 could attain complete removal, and NO removal efficiency was enhanced greatly through increasing the VUV irradiation intensity and H2O2 concentration [11]
The results showed that in-situ wet scrubbing could efficiently suppress thermal decomposition of ozone and improve NO oxidation selectivity over SO2

Summary

Introduction

Stringent regulations on marine gaseous pollutant emissions have come into force in recent years [1]. International Maritime Organization (IMO) set a goal to reduce at least 50% of greenhouse gas emission by global marine industry for 2050 compared with that for 2008. More interests are focused on non-fossil fuels, such as Liquified Natural Gas (LNG), NH3, H2, methanol, and biogas, as alternative fuels for marine propulsion plants. Once these alternative fuels are applied extensively in marine industry, they would greatly reduce the emissions of greenhouse gas together with other atmospheric pollutants. Newly built ships are required to reduce NOx emission concentration greatly when sailing in international emission control areas (ECAs). An exhaust gas treatment system that could control SOx and NOx simultaneously would be a good choice for shipowners as a short-term solution

Methods

Results

Conclusion