Thomas Hess, Burckhardt Compression, Switzerland, considers the range of compression technologies on offer for the handling of boil-off gas in LNG storage and shipping, and provides guidance on selecting the most suitable technology for different requirements.
ompressors are the main actors for gas handling in LNG facilities – both onshore and on ships. Handling of LNG boil-off gas (BOG) is complex, not least due to the very low gas temperatures. As the gas can be processed in multiple ways, each application has its own specific requirements. But why is gas handling required in LNG facilities at all? And what are the typical application ranges and compressor technologies available? This article provides a brief insight into the application range and the advantages of the LNG BOG compressor portfolio offered by Burckhardt Compression.
BOG in LNG storage and transportation
For storage in liquefaction plants, receiving terminals, or onboard ships, LNG is kept at atmospheric pressure under cryogenic conditions of below -160˚C. This condition is ideal for efficient storage and transportation since the liquid occupies only 1/600 of the volume of the gas. The transportation of LNG from liquefaction plants to the receiving terminals is done by ship. Onboard modern LNG carriers, the cargo is stored in highly insulated membrane type containment systems. Since the trading of LNG is a global business, and voyages from loading terminals in the US to receiving hubs in Asia can take approximately 30 - 40 days, the handling of BOG becomes crucial in order to keep the cargo tank pressure under control. Bunker ships supply LNG to gas-fuelled ships. Although smaller in size if compared to LNG carriers, BOG management is required to manage the cargo temperature and tank pressure. Despite the highest level of thermal insulation on storage tanks and piping, heat ingress to the LNG is unpreventable.
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