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DNV introduces LNG-fueled Very Large Crude Carrier concept

Rendering of the Triality concept design. © DNV/Making Waves. Click to enlarge.

Det Norske Veritas AS (DNV) has introduced a new very large crude oil carrier (VLCC) tanker concept that is fuelled by liquefied natural gas, has a hull shape that removes the need for ballast water, and will significantly reduce local air pollution. This concept vessel also recovers hundreds of tons of cargo vapors on each voyage.

The new crude oil concept vessel, named Triality, has been developed through a DNV innovation project. It was designed to fulfill three main goals(hence, Triality): to be environmentally superior to a conventional crude oil tanker; to use solutions that are feasible and based on well known technology;and to be financially attractive compared to conventional crude oil tankers operating on heavy fuel oil.

I am convinced that gas will become the dominant fuel for merchant ships. By 2020, the majority of owners will order ships that can operate on liquefied natural gas (LNG).

—DNV CEO Henrik O. Madsen

Compared to the traditional VLCC, the Triality VLCC will:

  • emit 34% less CO2;
  • eliminate entirely the need for ballast water;
  • eliminate entirely the venting of cargo vapors (VOCs);
  • reduce NOx emissions by more than 80%
  • reduce SOx and PM emissions by as much as 95%; and
  • use 25% less energy.

The new concept tanker has two high pressure dual fuel slow speed main engines fuelled by LNG, with marine gas oil as pilot fuel. The next phase of the Triality concept development will review the use of dual fuel medium speed engines and pure gas engines.

Two IMO type C pressure tanks capable of holding 13,500 m3 LNG—enough for 25,000 nautical miles of operation—are located on the deck in front of the superstructure. The generators are dual fuel (LNG and marine gas oil) while the auxiliary boilers producing steam for the cargo oil pumps operate on recovered cargo vapours (VOCs).

A traditional tanker in unloaded transit needs ballast water to obtain full propeller immersion and sufficient forward draft to avoid bottom slamming. The new V-shaped hull form and cargo tank arrangements completely eliminate the need for ballast water in the VLCC version. There will also be much less need for ballast water on other kinds of crude oil tankers, such as Suezmax, Aframax and smaller ships. The new hull shape results in a reduced wetted surface on a round trip and has a lower block coefficient and thus a more energy efficient hull.

A VLCC in unloaded transit will normally carry between 80,000 and 100,000 tons of sea water containing organisms that can cause damage when released into foreign ecosystems. In addition, a lot of fuel is needed just to transport this extra water. And finally, the initial coating and later maintenance of ballast tanks during operations are among a shipowner’s main concerns.

The Triality VLCC can collect and liquefy more than 500 tons of cargo vapors during one single round trip. These liquefied petroleum gases will then be stored in deck tanks and up to half will be used as fuel for the boilers during cargo discharge, while the rest can be returned to the cargo tanks or delivered to shore during oil cargo discharge.

DNV estimates an additional capital expenditure of 10-15% for a Triality VLCC newbuilding compared to a traditional VLCC. Even with this extra cost included, DNV estimates a reduced life cycle cost equal to 25% of the newbuilding cost for a traditional VLCC.



Why not!


Why not use the bad stuff for propulsion at sea and deliver LNG to the destination.

Yordan Georgiev

Even better solution:
Use small nuclear. US navy has done it for decades. See why:

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