The shipping industry is showing an increasing interest in reducing its global carbon footprint.

According to high-tech cryogenic equipment supplier Cryostar, there are at least two drivers to this trend: firstly, legislation is calling for more stringent emission control regulations. MARPOL TIER III (for NOx reduction) has been in force since January 2016 in coastal areas and further SOx reduction will become mandatory on all seas in the imminent future.

Secondly, with the perspective of the recovery of the heavy fuel oil price from historically low values, opportunities may be unleashed with cleaner fuels being less expensive in comparison. Combine this with the new ethane export market that has developed in the context of the shale gas discovery in the US, and there is tremendous potential for innovative fuel supply systems, Cryostar says.

Hartmann Reederei was one of the first ship-owners to embrace the use of ethane as a fuel, in order to comply with these stringent regulations. They selected AC Inox GmbH to facilitate the implementation of the fuel gas supply system (FGSS). Cryostar collaborated by suppling a number of key pieces of cryogenic equipment installed in its newly developed system.

The system is designed to feed either Ethane at 400 barg, or LNG at 300 barg as fuel to the MAN’s 7G50ME 12 MW main propulsion engine. The fully class approved FGSS, is installed on a semi-open deck and is expected to function for the entire 40-year vessel lifetime.

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Source: Cryostar

Cryostar’s long standing experience of delivering cryogenic equipment onboard LNG carriers ensured that few difficulties were encountered in adapting the already-referenced design to fulfil the specification and the related class requirements.

Cryostar designed, built and tested the following components to integrate the FGSS:

  • 2 Submerged motor pump (Subtran) installed in two separate tank
  • 2 Cryogenic reciprocating pump (MRP) built on a dedicated skid
  • 1 Vaporiser skid with HP CWX heater and integrated glycol water heating loop

After a number of project progress and interface meetings with DNV-GL’s active participation, the class issued the full design approval. The pumps, assembled at Cryostar’s headquarters in France, were successfully tested at full speed in the presence of the customer and owner. The Cryostar test facility, dedicated to cryogenic pumps, uses liquid nitrogen and is the largest of its kind in the world.

During the gas trial and after delivery of the vessels, on site operational feedback highlighted some peculiarities specific to the use of ethane. Aside from the higher pressures, some other challenges highlighted during operation were smoothly handled due to specific know how, which Cryostar has built over years of field experience.

These gas carriers are currently operating between the US and Europe, mainly using ethane as fuel. The FGSS availability reaches an unparalleled rate of more than 95%, making this system the most efficient and reliable high-pressure 2- stroke marine ethane-fuelled propulsion system in operation.