BOG Reliquefaction

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A reliquefaction system is used to control LNG tank pressure by liquefying boil-off gas (BOG)

Wärtsilä is a leading designer, developer, and supplier of energy efficient LNG boil-off gas (BOG) reliquefaction plants. With more than 50 systems in operation, we have the highest number of such plants installed – both onshore and on board the global LNG carrier fleet.

Our BOG reliquefaction systems are designed to be efficient, reliable, safe, robust and flexible. We work closely with our customers to develop technological solutions that meet their needs for increased fuel flexibility, energy efficiency, and environmental performance in today's fast changing LNG market.

    Technical data

    Typically, a reliquefaction system is used to control LNG tank pressure by liquefying boil-off gas (BOG).

    The reliquefaction process is based on reversed nitrogen Brayton cycle refrigeration technology. This means that the process is a closed nitrogen cycle for extracting heat from the boil-off gas. Our systems have the capability to handle all boil-off gas (100% capacity). The BOG reliquefaction system is engineered to order, with correct footprint and capacity, suitable for onshore facilities such as LNG terminals.



    Onshore, BOG reliquefaction is typically used in LNG terminals.

    Key benefits

    Instead of burning the boil-off gas, our reliquefaction system compresses, liquifies and returns the condensate back to the LNG tanks. Depending on the system's capacity, this reduces or eliminates harmful emissions and increases revenue.

    Our BOG reliquefaction plants offer the most comprehensive system solutions throughout entire gas value chain:

    • Competitive capex in all capacity ranges,
    • Optimized process for low opex cost
    • Could supply larger and complex systems

    Wärtsilä has the industry’s most extensive BOG reliquefaction reference list:

    • Reliable and proven technology
    • More than 50 plants delivered

    As a life-cycle oriented company, Wärtsilä adds value through:

    • Our global service network

    Smart digital solutions for optimal performance, 24/7 service available 


    • Knutsen-LNG-carriers
      Compact Reliq for Knutsen LNG carriers

      BOG reliquefaction simplified with the new Compact Reliq

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    • LNG vessel for Knutsen OAS Shipping reference
      LNG vessel for Knutsen OAS Shipping

      The latest development of the LNG infrastructure provides clear evidence of the increasing importance of LNG fuel to the marine industry. Wärtsilä has a lot of experience and know-how throughout the LNG value chain, and we are confident that their solutions are what we need for this latest expansion to our fleet.

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    Contact us

    Contact our 24/7 customer support at +47 815 48 500. For spare parts, please e-mail us with the equipment serial number or the name of the installation at (Inert Gas Systems) (all other products)
    For technical support & service, please email us with the equipment serial number or the name of the installation at
    Equipment serial number is taken from the equipment nameplate and includes all letters and numbers as given on the equipment nameplate.

    Please fill in the form, we aim to respond within 1-2 business days depending on the enquiry. For an existing installation, provide all necessary details to identify the installation and the equipment. Fields indicated with an asterisk (*) are required.