Figure 1. The Stirling Cryogenics micro scale integrated purification and liquefaction plant.
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he fast-growing use of LNG as a fuel for maritime and road transportation has increased the need for proven cryogenic technologies and solutions on a global scale. This novel market is pushing for a decentralised, flexible, and smaller scale LNG supply chain. This translates into developments such as LNG satellite storages and bunkering facilities, away from production facilities or terminals needing local small scale production of LNG. Critical success factors for the infrastructure are autonomous remote operation as well as energy efficient, modular, and reliable cryogenic cooling systems. The combination of all these factors have created opportunities for Stirling Cryogenics to prove its worth. Stirling Cryogenics is currently active in two different LNG applications: boil-off gas (BOG) management and micro scale LNG production.
Boil-off gas management BOG management is an iterative process. Storage tank volume, storage tank heat leak, composition of the BOG, management of non-condensable gases, systems layout and spatial constrains, desired output, operating pressure, engineering standards or notified bodies approval; all these parameters have their
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share of impact on BOG management. In designing the BOG management system, the main questions to be answered are: what is the expected boil-off rate? What is the maximum allowable and the required pressure of the LNG? What is the desired holding time? How can we handle the non-condensable gasses to avoid build-up and poor LNG heating value? In response to the market’s demand for retrofit solutions that can be implemented with minimum impact on the existing structures, Stirling Cryogenics developed a turnkey, containerised solution with a lead time shorter than one year. The only connections needed are BOG and LNG lines and electrical supply. The needed space is as limited as can be and easily dimensioned. The BOG management solution of Stirling Cryogenics is suitable for onshore and offshore storage tanks. Onshore storage tanks usually concern small scale LNG terminals or peak shaving facilities. Offshore storage tanks concern bunkering barges or small LNG carriers. Stirling Cryogenics adapted the technology to maritime conditions in 1990 when the Stirling machines were installed on the Tonen Ethylene Maru to manage BOG. The ethylene is transported as a (flammable) liquid at -104˚C. BOG coming from
