Small-Scale Liquefied Natural Gas Distribution
Maersk Line, Limited (MLL) and the Argent Marine Companies, who specialize in waterborne transportation of liquefied natural gas (LNG), are developing state-of-the-art articulated tug/barges (AT/Bs) for the safe and economical distribution of small-scale quantities of LNG.
Our AT/B concept separates the propulsion unit (tug) from the cargo unit (barge), creating a flexible and cost-effective solution that adapts to fluctuations in demand. Separation allows the tug to remain employed as the barge loads or discharges, which lowers delivered cost and creates flexibility at terminals or liquefaction plants. The size and maneuverability of the AT/Bs improve safety and deliver LNG at a cost advantage to other modes of transportation and in volumes sufficient to drive adoption of this clean fuel.
The AT/Bs function independently of pipelines and facilitate wider distribution of LNG similar to the current distillate model. This approach is the most efficient means to distribute LNG where gas pipelines are not connected or lack capacity. Importantly, the small-scale design appeals to public concerns about LNG safety and includes a fortified vessel and tank structure that minimizes risks if an accidental release were to occur. These characteristics will promote more rapid conversion to natural gas for industrial uses and as a transportation fuel.
Our proprietary AT/B design has two variants, bulk and intermodal. The bulk version received approval-in-concept from the American Bureau of Shipping (ABS), one of the world's foremost marine classification societies.
This LNG mode of transportation offers considerable operating cost advantages over other means of shipping LNG to local facilities. The bulk AT/B has the flexibility to separate propulsion (tug) from cargo (barge), enabling a "swap and drop" arrangement.
This AT/B currently under development has a capacity of 13,300 m³ in its baseline configuration, although capacities can range between 4000 m³ and 20,000 m³. It utilizes four (4) Type C containers of varying sizes – depending on capacities and features of specialized boil-off handling techniques. The unique design is also being considered for ship refueling (bunkering) of LNG powered vessels.
The intermodal AT/B baseline configuration has a capacity of 5,300 m³ comprised of approximately 144 ISO standardized Type C containers. These LNG-rated containers, also called "tanktainers," can be configured to standard 20 ft., 40 ft., or 45 ft. sizes.
This novel, small-scale LNG AT/B resembles a hybrid version of a gas carrier and container vessel. The vessel is configured with interconnected tanktainers that can be loaded simultaneously at an LNG loading terminal in 6 to 8 hours through a specialized piping system that addresses the distinct physical characteristics of LNG, such as boil-off vapor and pressure and temperature relationships.
At the unloading port, the containers can be unloaded in bulk (as they were loaded) or detached from the integrated piping system and individually discharged from the intermodal AT/B by a gantry crane. The tanktainers are now free to move via truck or rail to inland destinations where they can meet local natural gas demand.
Both variants can operate reliably in any weather condition and are capable of service speeds ranging from 11 to 14 knots.