Houston-based GTT North America (GTTNA), US subsidiary of French engineering and technology company GTT (Gaztransport & Technigaz SA), has received approval in principle from ABS for the design of a 2,200 cu. m. liquefied natural gas (LNG) bunker barge. The distinctive design incorporates GTT’s proven membrane Cargo Containment System (CCS), which is utilized in 70 percent of the global LNG carrier fleet and nearly 90 percent of LNG carrier projects on order.
Leveraging over five decades of LNG storage and maritime transportation experience, GTT developed the membrane LNG bunker barge to demonstrate the efficient storage of LNG and safe, reliable management of Boil-Off Gas (BOG) in an unmanned push barge application. The barge was designed for use in bunkering operations including ship-to-ship LNG transfers or LNG bulk transport in US inland waterways, harbors, and intra-coastal service. The barge could operate as a mobile refueling resource or be moored temporarily to serve as a refueling station.
“An important step in the wide-range adoption of LNG as a marine fuel is the development of bunkering infrastructure that can adequately meet the various operational needs of vessels,” said ABS Director of U.S. Gas Solutions Roy Bleiberg. “The use of the LNG bunker barge will be a critical part of infrastructure development and this design, which leverages proven GTT technology, is certainly a concept that LNG stakeholders should consider.”
The CCS selected for the barge was GTT’s proprietary Mark III Flex system, an enhancement of the Mark III system that allows for improved thermal and structural performance of the CCS. The Mark III membrane CCS consists of a cryogenic liner directly supported by the vessel’s inner hull, which allows for maximum volumetric utilization of the available cargo space. This liner is composed of a primary metallic membrane fastened atop a prefabricated insulation panel that includes a complete secondary membrane.
The GTT membrane LNG bunker barge will be capable of loading 2156 m3 (@98%) or 570,000 US gals. within 4.5 hours and towed at maximum speed of 8 knots in an efficient footprint: 64.2 m (212 ft) overall length, 14.8 m (48.5 ft) breadth, 7.2 m (15.7 ft) depth, and 2.6 m (8.5 ft) fully loaded design draft. The dimensions and gross tonnage of approximately 1440 GT afford the GTT membrane LNG bunker barge greater maneuverability and access throughout inland and intra-coastal waterways.
A distinguishing feature of the GTT membrane LNG bunker barge is the management of natural BOG through small-scale reliquefaction units. The StirLNG-4 cryo-cooler unit from the Netherlands-based Stirling Cryogenics was the basis of the boil off management system design.
“This barge design, now approved in principle by ABS, provides a robust solution for boil off gas management, an essential requirement for any atmospheric LNG storage system. The design is a major step forward in bringing the coldest cargo with the highest stored energy value to the US LNG fuel market in a safe manner,” said Allyn Risley, chairman, GTT North America.
Alameda, Calif.-based Herbert Engineering Corp. (HEC) was commissioned to develop the hull and preliminary machinery design scope and Houston-based CH-IV International to develop the cargo handling system (CHS) design scope.
ABS Consulting also assisted in the development of the GTT membrane LNG bunker barge project.