LNG tank ship having LNG circulating device

摘要

Disclosed is a liquefied natural gas storage apparatus. The apparatus includes a heat insulated tank and liquefied natural gas contained in the tank. The tank has heat insulation sufficient to maintain liquefied natural gas therein such that most of the liquefied natural gas stays in liquid. The contained liquefied natural gas has a vapor pressure from about 0.3 bar to about 2 bar. The apparatus further includes a safety valve configured to release a part of liquefied natural gas contained in the tank when a vapor pressure of liquefied natural gas within the tank becomes higher than a cut off pressure. The cut off pressure is from about 0.3 bar to about 2 bar.

主权项

1. An LNG tank ship for transporting LNG, the LNG tank ship comprising:
an LNG tank containing liquid phase (LNG) and gaseous phase (boil-off gas); a safety valve configured to release part of the boil-off gas from the tank when a vapor pressure within the tank exceeds a cut-off pressure of the safety valve, wherein the safety valve is configured to adjust the cut-off pressure within a range between a first value and a second value, the first value being 0.25 bar (gauge pressure) or below, the second value being between about 0.25 bar (gauge pressure) and about 2 bar (gauge pressure); and a liquid volume computing module configured to compute a current volume of LNG contained in the LNG tank; wherein the cut-off pressure of the safety valve is adjusted at least based on the current volume.