The Global Sulphur Cap 2020 adopted by the International Maritime Organization (IMO) in 2020 requires merchant vessel owners to comply with sulphur oxide emissions of less than 0.5% compared to 3.5%. LNG is an alternative fossil fuel that helps to achieve this goal.
By Joanne McIntyre
Compared to Heavy Fuel Oil (HFO), the use of LNG allows substantial reductions of more than 99% of sulphur oxides (SOx), 92% of nitrogen oxides (NOx), 91% of fine particles, and 23% of carbon dioxide. (Source: SEA-LNG report of April 13). LNG is therefore considered the ‘greenest’ fossil energy available for shipping, and a real technological breakthrough to reach compliance and maintain competitiveness simultaneously. GTT Group specialises in membrane containment systems for the transport and storage of liquefied gases. Its technologies are available for a wide range of shipping segments and LNG volumes. Its membrane technology is used to equip commercial vessels such as container ships, tankers, bulkers, car carriers, cruise vessels, etc.
Stainless steel and nickel-based alloys are employed in the membrane technology. The advantage lies in the specific combination of the various materials, giving inherent advantages for making lighter ships with high transport efficiency and a low ecological impact.
Membrane containment systems
Membrane tank volumes can vary from 1,000 m3 for passenger ships, to 10,000 m3 for tankers, and close to 20 000 m3 for very large container vessels.
As the increasing demand for LNG as fuel goes hand in hand with a developing supply chain, GTT has adapted its membrane technology for infrastructure including bunker barges, small and medium capacity LNG carriers used as refuelling vessels and suitable for inland waterways, and semi-submerge storage structures and bunkering stations placed on the seabed.
While the membrane technology uses relatively small quantities of corrosion resistant alloys (CRA), for the gas handling system, stainless steel is used for piping, valves and equipment (heaters, vaporisers, compressors, etc).
Cryogenic liner technology
GTT’s membrane technology is essentially a cryogenic liner used to contain liquefied gas at low temperatures during shipping, onshore and offshore storage, at atmospheric pressure.
Mark III is an insulating system directly supported by the ship’s hull structure. It is composed of a primary corrugated stainless steel membrane positioned on top of a prefabricated insulation panel, including a complete secondary membrane made of composite material. This modular system calls for standard prefabricated components that can accommodate any shape and tank capacity. To date, more than 400 LNG carriers in service or under construction have been equipped with this technology. The corrugated stainless membrane technology has been constantly improved and takes advantage of more than 50 years of experience at sea. It is also compliant with the latest standards: IGC 2016 and IGF.
The low thermal conductivity of the foam results in a thin insulation, maximising the cargo capacity. The two independent insulation spaces are continuously flushed with nitrogen gas. The integrity of both membranes is permanently monitored by detection of hydrocarbon in the nitrogen, making Mark III a very safe system.
