Jan de Nul cleans up new dredgers

Malcolm Latarche

Malcolm Latarche · 17 March 2017


A trio of new vessels being built in Singapore for Dutch dredging specialist Jan de Nul will be among the cleanest vessels operating globally the company has said. The three 3,500 m3 Trailing Suction Hopper Dredgers Jan De Nul Group ordered from Keppel Singmarine will be equipped with exhaust gas treatment systems reducing SOx, NOx and particulates. The vessels combine a shallow draught with high manoeuvrability, making them very suitable for working in confined areas. The new vessels will operate with normally available fuel oil, and the exhaust gases are cleaned by means of a Selective Catalytic Reduction (SCR) system, and a Diesel Particulate Filter (DPF). The SCR system lowers the amount of NOx in the exhaust to a level corresponding with the future European (EU Stage V) requirements for inland waterway vessels; this standard is much more stringent than the applicable IMO Tier II and Tier III requirement. The DPF removes particulate matter from the exhaust, down to a level in accordance with the future EU Stage V requirement for inland waterway vessels. Combined with the use of readily available low sulphur fuels, the emissions (NOx, SOx, Particulate Matter, CO and Hydrocarbons) will comply with EU Stage V, and be better than any other vessel or dredger. They will be equivalent or better than these of a dredger using LNG as fuel. But, by using normally available fuels, compared to the limited availability of LNG, these lower emissions are achieved worldwide, and all of the time. The vessels are in diesel-electric execution: all major drives (thrusters, dredge pump, jet pumps...) are electrically driven, and controlled by means of frequency converters. In this way each system can operate at its optimal speed and power. Power is generated by means of three diesel generator sets; a control system automatically starts and stops the sets depending on the power requirement, and by means of asymmetric load sharing ensures that the load is optimally distributed over the diesel generator sets. Jan De Nul is one of many shipowners considering how to meet the 2020 sulphur cap and with the date rapidly approaching, others must consider what strategy to adopt, For new vessels, exhaust gas treatment will add less to the capex bill than the retrofits needed for existing vessels. However, unlike ballast treatment where potential alternatives (regional exemptions and shore-based treatment systems) to installing a system are beginning to appear for some ships, meeting the new SOx rules means either fitting a scrubber, replacing or adapting the engine and fuel system or running on expensive distillates only.
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