7 February 2012
Mitsui O.S.K. Lines (MOL) announced the start of a demonstration test of a diesel particulate filter (DPF) system on an MOL Group-operated ocean-going vessel. The DPF system is installed on the diesel engine used for power generation onboard of the ship. This is the world’s first application of a self-cleaning DPF on an ocean-going ship, according to MOL.
With research support from Nippon Kaiji Kyokai (ClassNK), MOL and Akasaka Diesels have jointly developed a DPF system for marine diesel engines, which run on C heavy oil. The initiative is part of ClassNK’s program to support joint research and development with industry and academia. MOL conducted a demonstration test of the DPF system in 2010, using the main engine of the Sunflower Kogane ferry, serving coastal areas in Japan.
The DPF system utilizes four cylindrical, wall-flow silicon carbide (SiC) filters arranged in parallel. The PM collection efficiency was reported at 80%—a relatively low figure compared to automotive DPF systems, possibly explained by high concentrations of particle precursors (e.g., sulfur compounds) that pass through the filter in the gas phase. The filter was “significantly reducing black smoke emissions”, said MOL.
The DPF system includes an automatic, active regeneration (“self-cleaning”) system. One filter unit is regenerated at a time, with the exhaust gas flow to the regenerated unit being shut off by a valve and the three remaining units filtering the gases. The filter is regenerated using an internal heating system, but no technical details were disclosed. One of the challenges in developing DPF systems for heavy oil fuels is very high content of ash that cannot be oxidized during regeneration and accumulates in the filter. While no particulars were given on ash handling, the DPF system “requires no maintenance by seafarers”, said MOL.
The test is scheduled for about one year—about 4,000 hours of operating time—to verify the system’s PM collection performance and to accumulate enough time for a durability assessment. The test started in November 2011, and the DPF system has already operated for over 500 hours.