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London: The introduction of a new crude oil tanker concept that is fueled by liquefied natural gas, has a hull shape that removes the need for ballast water and will almost eliminate local air pollution. This concept vessel also recovers hundreds of tons of cargo vapours on each voyage and represents a major step towards the new environmental era for the tanker shipping industry.
The new crude oil concept vessel, named Triality, has been developed through a DNV innovation project. As its name indicates, it fulfills three main goals: it is environmentally superior to a conventional crude oil tanker, its new solutions are feasible and based on well known technology, and it is financially attractive compared to conventional crude oil tankers operating on heavy fuel oil.
DNV CEO Henrik O. Madsen, who presented the new concept in its VLCC version in London today, says: “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). As a leading class society, DNV has an important role to play in finding more environmentally friendly solutions for the shipping industry, and I’m proud of what has been achieved for the crude oil tanker segment through this innovation project that we are presenting today.”
Less harm to the environment
The Triality concept VLCC has been compared to a conventional VLCC. Both ships have the same operational range and can operate in the ordinary spot market. 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 vapours (VOCs) - use 25% less energy - Less harm will also be caused to the health of people living close to busy shipping routes and ports as NOx emissions will be reduced by more than 80% while emissions of SOx and particulate matter will fall by as much as 95%.
The new concept tanker has two high pressure dual fuel slow speed main engines fueled 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).
No ballast water
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.
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