Retrofit concepts to reduce the costs of converting and operating LNG

LNG tanks would be stacked like containers and loaded and unloaded by container cranes (Marine Service/Newport Shipping)

Published March 11, 2022 17:01 by

The Maritime Executive

As the shipping industry looks for solutions to meet decarbonization goals, one of the challenges is to develop a cost-effective solution to accommodate the large number of vessels in service. Two different groups presented proposed solutions which they say will drastically reduce the cost of retrofitting a wide range of in-service container ships to use LNG and look to future alternative fuels such as bio-LNG or possibly next-generation fuels how to prepare ammonia.

While the container shipping segment has begun developing LNG-capable vessels, cost and lost operational time remain a hurdle to overcome. Hapag-Lloyd has completed the first major conversion of an LNG-capable ship, the 15,000 TEU Sajir, which was built in 2014 and anticipates a future remodeling. the The transition took almost nine months while the LNG tank was installed and the main engine and auxiliary diesel engines were converted for LNG and low-sulphur operation. In addition to the financial cost and downtime, the ship sacrificed an area equivalent to 350 containers to install a 6,700 cubic meter gas storage system and the piping between storage and engine. Rolf Habben Jansen, CEO of Hapag-Lloyd, said that while the company has gained valuable experience retrofitting and running the ship, the cost of retrofitting is prohibitive for the shipping company to consider across its fleet .

Marine Service GmbH and Newport Shipping believe they have developed an approach that simplifies retrofitting, requiring less time and cost while being easier to use. Their concept consists of LNG cylinders containerized in open frames of the same size as existing 40ft containers. The cylinders would be stacked on deck similar to current container stacks, handled in the same process as freight containers, and secured using the same process. The LNG containers would be fully portable, allowing them to be loaded and unloaded using container cranes and exchanged for full tanks during port calls. The empties would be transferred to trucks for refilling and could be stored at the port to load the ship on its next call.

LNG piping and venting systems and firefighting systems would be integrated into the container cell’s management structure. The gas handling room would be located adjacent to the container yard and separated from the containers by a cofferdam and fire suppression means to feed low pressure and high pressure fuel gas systems suitable for the current 4-stroke and 2-stroke two-stroke petrol engines.

LNG tanks would be exchanged at port with the same equipment as containers (Marine Services/Newport Shipping)

The LNG fuel tank container would be a class approved Type C LNG fuel tank according to the IGF code and is based on the German TÜV certified IMDG container. The capacity of the tank is 31 gross tons and about 33 m3 LNG. The containers feature a fail-safe dry quick-disconnect connector and are approved for loading in stacks up to seven tiers high. The double-walled stainless steel tank is also vacuum insulated and has a holding time of up to 80 days.

Another benefit of the rack system would be the ability to build the structure in advance at the shipyard. It could then be installed during a regularly scheduled dry dock, reducing the time the ship would spend out of service. They found that instead of tearing up space in the hull for the LNG tank, their design could also be used for new buildings.

The companies report that they have identified up to about 900 operational container ships of 4,000 TEU and above that would be best suited for the conversion. The system could be scaled to the specifications of the individual shipowner. Bureau Veritas worked with the companies that reviewed the designs and has granted approval in principle for the containerized LNG solution.

Concept envisages adding a section for the LNG tank and expanding the TEU capacity (Alwena Shipping)

The alternative retrofit concept, which also received an AiP from BV, was developed in collaboration between Alwena Shipping, COSCO Shipping Heavy Industry Zhoushan shipyard and GTT. Their LNG conversion concept combines a ship lengthening for very large container ships. They call for the addition of a section to the ship’s hull that would contain the LNG tank and the necessary equipment to reduce lost space and provide additional TEU capacity.

In this concept, the lengthening of the vessel combined with the conversion of the onboard propulsion and power generation system to LNG allows the operating costs of the vessel to be reduced with the additional capacity and benefits of LNG. They would limit the financial impact associated with the downtime required for the conversion of the ship by building the new section in advance at the shipyard and making the necessary preparations for the extension.

About Christine Geisler

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