container ships
large longhaul container ships. Major operational savings are deliverable, combined with very much lower air emissions. And the key feature of the design is that the vessel can also run on heavy fuel oil if required, increasing flexibility in the period before LNG bunkering is widely available.” The 365.5m-long/14m-design draught vessel would be powered by an MAN B&W ME-GI (gas injection) dual-fuel, low speed two-stroke engine configured to burn HFO and LNG. In minimum fuel/maximum gas mode around 10 per cent of the fuel is oil, yielding overall reductions in carbon dioxide emissions of around 23 per cent and SOx reductions of 92 per cent. With a maximum continuous rating of
72.3MW, the engine would deliver a design speed of 24 knots and enable a fully-bunkered operating range of 25,000 miles.
LNG fuel would be stored in a 22,490m3 capacity prismatic tank installed under the forward accommodation, with heavy fuel oil in a 4,430m3 bunker tank aft. The LNG storage facility would be based on Daewoo’s patented ACT-1B aluminium IMO type B independent cryogenic cargo tank with polyurethane foam panel-type insulation. “Compared with the same ship having a conventionally-fuelled power plant there will be extra capital cost for the engine, LNG tank and gas handling system as well as a loss of cargo space equivalent to 438 TEU to accommodate the gas tank and equipment,” Mr Segretain acknowledges. “But the extra capital cost and loss of earnings on a theoretical full ship are more than offset by the fuel economies and lower emissions of this design.”
Approval in principle from DNV has been gained for a 9,000 TEU LNG-fuelled container ship design development by Kawasaki Heavy Industries featuring cargo space-saving LNG storage. The prismatic, rectangular low pressure insulated (type B) LNG storage tank is said to exploit the available space much better than a cylindrical pressure tank (type C). In addition, Kawasaki’s Panel System for insulation reduces the evaporation rate of the LNG. B-type tanks produce evaporating LNG continuously, which must be tapped for propulsion or auxiliaries; reefer containers can consume the
Kawasaki’s 9,000 TEU LNG-fuelled container ship concept has DNV approval in principle
boil-off gas in port, eliminating any emission of LNG to the atmosphere and avoiding the need for cold ironing (switching to shoreside power supplies). The 7,000m3 capacity LNG fuel tank and diesel oil tanks are located under the forward superstructure to minimise the loss of cargo space. KHI has secured DNV approval in principle for both the gas supply system and the LNG fuel tanks, and now plans a safety assessment of the ship with the classification society. • Danish consultant Knud E Hansen sought high fuel economy with reduced environmental impact in developing a new 2,000 TEU feeder container ship design in conjunction with ABB. With main dimensions optimised for calls at the Thai port, the Bangkok- max vessel’s fine hull lines and efficient propulsion system reportedly achieve a fuel economy 15-25 per cent better per TEU than typical vessels of similar size.
The designers also addressed a reduced need for water ballast, slow steaming potential and flexible transit speeds, loading flexibility and increased container capacity (including a higher than usual reefer load). Capacity in the gearless version is arranged for 1,448 TEU on deck and 668 TEU in the holds, corresponding to a total high-cube capacity of 2,116 TEU.
Propulsive efficiency would be significantly
boosted by contra-rotating propulsors: an ABB electric Azipod unit mounted aft of a diesel- driven main propeller, with the power balance of approximately 65/35 per cent between propeller and Azipod. The 360-degree rotatability of the Azipod promises high manoeuvrability, reducing or eliminating the need for tug assistance in port. Compared
with an equivalent ship
with conventional direct-diesel propulsion, the designer explains, the main engine can be considerably downsized; and, with a correspondingly
smaller propeller LNG fuel storage for KHI’s 9,000 TEU design 28 I Marine Propulsion I February/March 2012
in combination with a low shaftline, ballast water to submerge the propellers in light-loaded conditions is generally not necessary. At 18 knots the main engine and associated generator
shaft will deliver the complete
propulsive power requirement, including electrical power for the Azipod, the hotel load and the reefer containers. Additional auxiliary power will only be needed if higher speeds (up to 21 knots) are required or if an exceptionally large number of reefer containers are carried. Three diesel gensets with an aggregate electrical output of around 8,000kW are arranged in an auxiliary machinery space completely segregated from the main engineroom. A speed of more than 13 knots will be possible with the main engine stopped and the auxiliary electrical power feeding the Azipod propulsor. A high degree of redundancy and more than sufficient get-home capability are thus secured by the machinery outfit. Another innovative feature of the Bangkok- max feeder vessel specification is ABB’s new onboard DC electrical grid system, which ensures that the engines run at their optimum load at any service speed from two to 21 knots. Fuel economy is thereby enhanced and highly flexible transit speeds facilitated, including slow steaming, which is not the case with most contemporary feeder vessels, Knud E Hansen reports. Heavy fuel
oil tanks are arranged in a
simple, square block below the narrow midship deckhouse, minimising the need for
trim-
compensating ballast water and changes in trim during a voyage. In addition, the tanks are segregated from the hull sides and bottom in readiness for Clean Design class notation. Space is prepared in the engine casing for
diameter
SOx scrubbers or a NOx-reducing selective catalytic reduction system, enabling the ship to be retrofitted for navigation in ECAs. Zero- emission port calls will also be possible since containers housing batteries can be stowed on the aft deck and connected to the DC grid. Maersk Broker, the exclusive broker for the new Knud E Hansen container ship design, was involved early in the project and is enthusiastic about its potential, citing impressive results in speed/fuel consumption, stowage flexibility and transit speed versatility. The ‘future-proof’ design should prove attractive to liner and tramp shipping operators, the Danish broker asserts. MP
www.mpropulsion.com
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