Jan De Nul, international contractor specializing in dredging, offshore and environmental services, announced that ordered three new dredgers from Keppel Singmarine. The three 3,500 m3 Trailing Suction Hopper Dredgers will be equipped with exhaust gas treatment systems, in order to reduce harmful emissions.
JDN noted that the vessels combine a shallow draught with high manoeuvrability, making them very suitable for working in confined areas. In particular, they are in diesel-electric execution: all major drives, such as thrusters, dredge pump and 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, the load is expected to be optimally distributed over the diesel generator sets. All these measures result in a low fuel oil consumption.
In compliance with IMO regulations for NOx emissions and, as the new dredgers will frequently operate near residential areas, the company highlights that decided to limit the NOx emissions to a level beyond the actual requirements, and to reduce other contaminants that are currently not regulated by IMO. 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 and the DPF removes particulate matter from the exhaust, both in accordance with the future EU Stage V requirement for inland waterway vessels.
The company states that, comparing to LNG, the same or even better results are achieved by using exhaust gas treatment, and the important environmental and operational downsides of LNG are avoided.
“The availability of LNG is poor. In addition, due to space and cost restrictions, LNG dredgers have very limited capacity for LNG, and therefore an autonomy of only about 1 week. In practice, a LNG dredger is only occasionally, and/or in a limited geographical area, capable of operating with LNG. Normal fuel oil will have be used for most of the time or in most of the world, and therefore without any improvement with respect to emissions”.
Source & Image credit: Jan De Nul Group