Mitsubishi Heavy Industries, Ltd. (MHI) and Mitsubishi Kakoki Kaisha, Ltd. (MKK) have jointly developed a “Hybrid SOx Scrubber System” that efficiently removes sulfur oxides (SOx) from exhaust gas emitted by marine diesel engines. The Hybrid SOx Scrubber System is the first in Japan to comply with the more stringent SOx emission regulations that will take effect in designated emission control areas (ECA) in 2015. The system is capable of scrubbing exhaust gas from the combustion of fuels emitted from bunker heavy fuel oil to the level combusting more costly low-sulfur fuel oil. By adopting a modular design, the system also facilitates retrofit installations on ships already in service.
The Hybrid SOx Scrubber System has two scrubbing system: one that uses circulating with freshwater and the other uses one-pass flow with seawater. Removal of atmospheric pollutants can be effected by either system. The freshwater system is capable of scrubbing exhaust gas from combustions of heavy fuel oil with 3.5% sulfur content to that of low-sulfur fuel oil with 0.1% sulfur content, achieving compliance with SOx emission regulations of IMO (International Maritime Organization) scheduled to go into effect in ECA in 2015. The seawater system is capable of scrubbing exhaust to a level of 0.5% sulfur content fuel oil to comply with regulations that are expected to be applied in global marine areas in the future. Washing seawater is discharged outside after treatment, complying with requirements for discharged wash water.
Hybrid SOx Scrubber System includes an SOx scrubber, a container unit housing a wash water processing system and other components, and ISO standard tank containers to store sludge and a caustic soda solution (NaOH) to neutralize circulating fresh water. Modular construction enables flexible arrangement of components, reducing installation time and cost requirements, and making it easier to retrofit the system to ships already in service.
The IMO SOx emission regulations scheduled to take effect in 2015 will tighten air pollution standards to 0.1% sulfur content in designated ECA including the North Sea, Baltic Sea, and the Pacific and Atlantic coasts of the United States. The 0.5% regulation in global marine area is being discussed with possible implementation in 2020 or 2025. In addition, designated emission control areas may be expanded in the future to other sea area. In order to continue to use inexpensive bunker heavy fuel oil with high sulfur content, SOx scrubber system will therefore become indispensable.
MKK has been providing flue gas scrubbing systems for desulfurization and denitration to the chemical industry in Japan since the mid-1950s. In addition, it has also developed products such as centrifugal separators for bunker fuel oil and lubrication oil for diesel engines, and pressurized fine filtration system for the chemical industry. By combining MHI’s sophisticated technology and shipbuilding expertise with MKK’s proven flue gas scrubbing technology, the two companies were able to successfully develop an advanced new SOx scrubber system that ensures compliance with increasingly stringent emission standards.
Going forward, MHI and MKK will draw on their extensive shipbuilding and engineering expertise to aggressively promote the new high-performance SOx scrubber system for use on both newly commissioned ships and ships already in service, including ships built by other shipyards.