The 3500 m3 Trailing Suction Hopper Dredger (TSHD) Diogo Cão was launched last Saturday at the Keppel Nantong shipyard in China, a subsidiary of Keppel Offshore & Marine.
This green vessel is the second of three hoppers to be launched, equipped with an exhaust gas treatment system filtering out and virtually eliminating many pollutants from the exhaust gases. In total, Jan De Nul Group ordered six such ultra-low emission TSHDs, called Ultra-Low Emission Vessels: three small ones (3500 m3), two medium-sized (6000 m3) and a larger vessel (18,000 m3).
European Stage V and IMO Tier III Regulations
The six diesel-electric vessels have engines allowing optimal use of generated power but with low fuel consumption and emissions. In addition, the vessels are equipped with a two stage highly efficient exhaust gas filter system, resulting in emissions complying with the European Stage V regulations for inland waterway vessels.
Robby De Backer, New Building Director at Jan De Nul Group: 'As the new dredgers will frequently operate in estuaries, rivers and coastal areas near urban areas, we decided to limit the NOx emissions to a level 30% below the actual IMO Tier III requirements, and to reduce other potentially harmful contaminants that are currently not regulated by IMO.'
The maritime transport regulator International Maritime Organisation (IMO), states that clean burning fuel vessels have to comply with the IMO Tier III regulation. The European regulations on land, Stage V, are far stricter. Mainly because for the first time, particles emitted down to 23 nanometres are taken into account.
SCR and DPF
The new vessels will operate with normally available ultra-low sulphur gasoil, with the exhaust gas treated in two stages by means of a Selective Catalytic Reduction (SCR) system, and a Diesel Particulate Filter (DPF). The SCR system lowers NOx to achieve EU Stage V levels for inland waterways. The second stage DPF removes particulates from the exhaust, also down to the future EU Stage V levels. Eliminating black carbon emission with the DPF significantly reduces the climate impact of these vessels.
Swiss Tunnelling Technology
Jan De Nul Group chose technology based on the Swiss example of filtering exhaust gases in the tunnelling industry.
'Since the 1990s, the tunnelling industry has used exhaust gas filtration on vehicle and heavy duty machinery emissions to provide clean, breathable air for workers tunnelling under the Alps,' explains Michel Deruyck toe, Fuel Coordinator at Jan De Nul Group. 'Today we are applying the same filtering techniques on our new vessels, and by accounting for particle numbers we obtain a 99% filtration efficiency and detoxification by catalysis.'
The Diogo Cão’s Design
The design of the Diogo Cão is based on the 3400 m3 TSHD Alvar Nuñez Cabeça de Vaca and Sebastiano Caboto, built in 2011. The vessels combine a shallow draught with high manoeuvrability, making them very suitable for working in confined areas.
Diesel-electric Propulsion
The Diogo Cão has diesel-electric propulsion: all major drives (thrusters, dredge pump, jet pumps, etc.) 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. Asymmetric load sharing results in optimal load distribution over the diesel generator sets.
Particulars
- Hopper capacity: 3500 m3
- Deadweight: 5500 t
- Length o.a.: 89.3 m
- Breadth: 22.0 m
- Max. dredging depth: 27.6 m
- Suction pipe diameter: 800 mm
- Speed: 11.3 kn
- Pump power (trailing): 1250 kW
- Pump power (discharging): 3000 kW
- Propulsion power: 2 x 1100 kW
- Total installed diesel power: 5510 kW
- Accommodation: 16 persons
Keel Laying of First 6000 m3 TSHD
Now the Diogo Cão is launched, the keel laying of the first 6000 m3 vessel is planned to take place on 19 July at the Keppel Singmarine in Singapore. Both 6000 m3 TSHDs will be named after two decommissioned vessels of the Group's fleet: Sanderus and Ortelius.
