## 1 Introduction  
Ocean-going ships undertake more than 90% of the global cargo transportation tasks; however, the pollutants in their exhaust emissions (such as NO\({}_{x}\) and SO\({}_{x}\)) also cause serious air pollution and endanger human health [1, 2]. NO\({}_{x}\) and SO\({}_{x}\) are important components in the formation of photochemical smog in the atmosphere, the destruction of the atmospheric ozone layer, and acid rain. In order to control exhaust emissions from ships, the International Maritime Organization (IMO) revised Annex VI of MARPOL 73/78 convention to limit NO\({}_{x}\) and SO\({}_{x}\) emissions, as shown in Figure 1[3]. Due to increasingly stringent regulations, it is imperative to develop highly efficient desulfurization and denitration technologies for ships. Selective catalyst reduction (SCR) is the main method used to remove NO\({}_{x}\), the denitration efficiency of which can reach more than 90%; however, SO\({}_{2}\) in ship exhausts will cause sulfur poisoning of the SCR catalyst and reduce the catalyst's efficiency [4, 5]. The effective way to avoid sulfur poisoning is to place the SCR system behind the wet desulfurization unit, although the SCR system will face the problem of low exhaust temperature. Due to the high efficiency and technical maturity of the wet scrubbing gas desulfurization (WFGD) system, it has been widely applied for ship desulfurization [3, 6]. Wet-type desulfurization and denitration technologies are easy to integrate with WFGD, reducing the investment cost and floor space of the whole system; therefore, on the basis of ship WFGD, wet-type desulfurization and denitration technologies will be important development directions for ship exhaust gas treatment technology in the future [7]. The denitration efficiency of the WFGD system is insufficient [8]. This is because more than 95% of NO\({}_{x}\) in the exhaust exists in the form of NO, which is difficult to dissolve in water. The oxidation of NO to NO\({}_{2}\) is an effective way to improve the denitration efficiency of the wet scrubbing system. At present, the methods used for NO oxidation mainly include the use of oxidants (such as KMnO\({}_{4}\)[9], CIO\({}_{2}\)[10], O\({}_{3}\)[11; 12; 13; 14], H\({}_{2}\)O\({}_{2}\)[15; 16], NaClO\({}_{2}\)[17; 18]), seawater electrolysis technology [19], and non-thermal plasma (NTP) technology [20]. Among them, NTP technology has the advantages of low investment and operation costs, and has become a research hotspot in terms of flue gas treatment [21; 22]. [PERSON] et al. built a DBD reactor combined with a seawater scrubbing system for a diesel engine, achieving removal efficiencies for NO\({}_{x}\) and SO\({}_{2}\) of 70% and 90%, respectively [23]. [PERSON] et al. investigated the effects of different scrubbing solutions (Na\({}_{2}\)SO\({}_{3}\), FeSO\({}_{4}\), Na\({}_{2}\)SO\({}_{4}\)) on the denitration efficiency using NTP oxidation combined with wet scrubbing [24]. [PERSON] et al. established a one-dimensional model for a plasma chemical reaction process involving desulfurization and denitration via corona discharge [25]. [PERSON] et al. built an electron beam (EB) combined with a seawater scrubbing system, and the effects of the EB dose and NO and SO\({}_{2}\) concentrations on desulfurization and denitration were investigated [26]. [PERSON] et al. proposed a DBD reactor combined with a wet electrostatic precipitator (WESP) system and studied the effects of the specific energy density (SED) and NO and SO\({}_{2}\) concentrations [27]. [PERSON] et al. used an EB combined with a wet scrubber for desulfurization and denitration, and the effects of the pollutant concentration, scrubbing solutions (NaCl, NaOH, H\({}_{2}\)O\({}_{2}\), NaClO\({}_{2}\)), and gas flow rate were investigated [28]. [PERSON] et al. studied the effects of NaClO, NaClO\({}_{2}\), and NaClO\({}_{3}\) solutions on denitration using an EB combined with a wet scrubber [29].