Exmar has chosen LPG-burning, dual-fuel engines to propel a pair of very large gas carriers (VLGCs) it has ordered at the Subic Bay yard of Hanjin Heavy Industries & Construction in the Philippines. On delivery in 2020 the 79,500 m3 newbuilding pair will go on long-term charter to Statoil.
The Belgian ship operator’s VLGCs will be the world’s first LPG-fuelled vessels. The ship and propulsion system design has been developed in tandem with Lloyd’s Register, as the vessels’ class society, and MAN Diesel & Turbo, the engine manufacturer.
MAN has achieved considerable success with its mechanically operated, electronically controlled, gas-injection (ME-GI) diesel engine, first in the LNG carrier sector and, more recently, with ethane carriers. The breakthrough Exmar VLGC orders represent a further step forward in the development of MAN’s dual-fuel, two-stroke engine technology and the utilisation of liquefied gas cargo as propulsion system fuel.
In January 2018 MAN Diesel & Turbo signed a memorandum of understanding (MoU) with Hyundai Heavy Industries Engine & Machinery Division (HHI-EMD) on the development and production of MAN B&W ME-LGIP dual-fuel engines.
On finalisation of the agreement, HHI-EMD will be able to deliver LPG-fuelled, two-stroke engines.
As is the case with LNG and ethane gas carriers, the relatively small amount of cargo boil-off gas required to propel the vessel is injected into the engine at high pressure. Propane, butane or propane/butane mixes can be burned in ME-LGIP engines.
MAN points out that, as is the case with its ME-GI engines, ME-LGIP units can also be used on vessels that are not gas carriers, provided they are fitted with LPG bunker tanks and fuel gas supply systems. LPG has similar clean-burning characteristics to LNG and the use of LPG fuel will enable ships to comply with the 0.5% global sulphur cap coming into force on 1 January 2020.
The lowest temperature at which LPG needs to be carried by sea is -45˚C, the boiling point of propane at atmospheric pressure. Because cryogenic carriage temperatures are not involved, the provision of LPG bunkering infrastructure, including shipboard equipment, should not be as technically challenging or as costly as that for LNG.