BOG Reliquefaction

With our market-leading Compact Reliq portfolio, boil-off gas is handled in the most efficient, reliable and safest ways and the portfolio is developed for easy integration and installation, suitable for all size of LNG Carriers and on both newbuilds and retrofits.

Nord Gas Solutions is solving your BOG handling effectively

When tankers transport liquefied natural gas (LNG), a slight evaporation of the cargo – known as boil-off gas (BOG) – is inevitable. To maintain the right tank pressure, it is essential to remove BOG from the tanks. The conventional method has been to use some BOG as fuel for propulsion, while excessive gas is burnt in a gas combustion unit. This not only releases harmful gases to the environment, but also treats most of the BOG as waste.

A more efficient and environmental-friendly alternative is to reliquefy excess BOG and return it to the cargo tanks. This way, pressure is maintained within safe limits and loss of cargo is prevented at same time as harmful emissions is minimized.

With Nord Gas Solutions market-leading Compact Reliq portfolio, boil-off gas is handled in the most efficient, reliable and safest ways and the portfolio is developed for easy integration and installation, suitable for all size of LNG Carriers and on both newbuilds and retrofits. With more than 75 systems in operation, Nord Gas Solutions has the highest number of BOG reliquefaction plants installed in the global LNG carrier fleet.

Technical Data

Nord Gas Solutions has been a pioneer in this field since the early 2000s, and is today a leading designer, developer and supplier of energy efficient LNG BOG reliquefaction plants. We supply complete and integrated systems including BOG reliquefaction and fuel gas supply systems as compressor solutions, and LNG pump solutions required for feeding engines with low and/or high-pressure gas.

Our BOG reliquefaction process is based on reversed nitrogen Brayton cycle refrigeration technology, using commercial grade nitrogen to extract heat from the boil-off gas. During this reliquefaction, the cargo is kept cool and at the right pressure under all operating conditions. The systems allows a portion of the BOG to be used as fuel for the ship's engines, while the excessive liquefied gas is returned to the main tanks to be sold as cargo. The systems can be designed to handle all boil-off gas, or only the excessive gas not used by the engines (partly liquefaction).

Nord Gas Solutions' Compact Reliq module is our updated offering, translated into a compact and reliable module. The Compact Reliq is also instrumented for remote monitoring and online operational support as part of Nord Gas Solutions' OPERIM programme.

For smaller BOG capacities we also have a Mixed Refrigerant (MR) system which offers supreme efficiency.

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