The International Maritime Organization (IMO) has decided to implement a tighter limit for nitrogen oxide (NOx) emissions from ships operating in emission control areas (ECA) from 2016. Hitachi Zosen Corporation has developed a marine SCR system to denitrate exhaust gas of large two-stroke diesel engines in order to comply with the IMO regulation. Nippon Kaiji Kyokai issued a certificate attesting that certifies a large two-stroke diesel engine Hitachi-MAN B&W 6S46MC-C7 fitted with the SCR system achieved the NOx emission level required by the IMO regulation. The system was installed on a new-built vessel, and verification tests were carried out for a long period. In this paper, we will present a summary of the marine SCR system, and report on sea trial results of the marine SCR system installed on the new-built vessel, as well as those of a similar SCR system installed on a multi-cylinder test diesel engine in order to solve technical issues encountered during long-term service test.
In this paper, the effect of magnesium electrode on the alkalization of seawater by electrolysis was investigated in order to improve the performance of SOx scrubbers for ship exhaust. The simulated seawater was electrolyzed using carbon electrode or magnesium electrode, and the pH, voltage, current, input power, and alkalinity values were measured. The energy efficiency improvement of the alkalization process was evaluated. The results show that the alkalinity of the simulated seawater increased from 100 to 200 mg-CaCO3/L by electrolysis. It was also shown that with magnesium electrode the energy efficiency was significantly improved compared with that using carbon electrode because of its ability to suppress the generation of Cl2.
A study was conducted to improve diesel generator efficiency using waste plastic decomposition oil (WPDO). Waste plastic reaches an annual figure of 10 million tons or more in Japan. Although it is thought that material recycling is the best approach to preserve the environment, its energy yield based on life cycle is not sufficient. Therefore, waste incineration to produce electricity with thermal power generation is recommended. However, this thermal recycle needs a huge facility, and requires extra energy to transport waste plastic. Consequently, another method of thermal recycle using WPDO is considered. The WPDO is used to run a diesel engine to increase generator efficiency. However, WPDO emits much nitrogen oxide (NOx) and smoke (exhaust gas light absorption coefficient). In this paper, the use of water emulsion WPDO to reduce NOx and smoke is proposed. An experimental study with water concentration ratios of water emulsion WPDO of 10%, 20%, and 30% respectively, was conducted. The fuel properties such as density and kinematic viscosity were measured. Finally, each water emulsion WPDO was burned in a conventional 219-cc diesel engine. Although total hydro carbon (THC) and carbon monoxide (CO) increased, NOx and smoke reduced drastically. The amount of NOx and smoke emissions were reduced by 60% at the maximum load compared with gas oil. Moreover, brake fuel specific consumption (BSFC) slightly improved at 10% and 20% water concentration ratios.