Abstract

Boil-off gas (BOG) from a liquefied natural gas (LNG) storage tank depends on the amount of heat leakage however, its assessment often relies on the static value of the boil-off rate (BOR) suggested by the LNG tank vendors that over/under predicts BOG generation. Thus, the impact of static BOR on BOG predictions is investigated and the results suggest that BOR is a strong function of liquid level in a tank. Total heat leakage in a tank practically remains constant, nonetheless the unequal distribution of heat in vapor and liquid gives variation in BOR. Assigning the total tank heat leak to the liquid is inappropriate since a part of heat increases vapor temperature. At the lower liquid level, BOG is under-predicted and at a higher level, it is over-predicted using static BOR. Simulation results show that BOR varies from 0.012 wt% per day for an 80% tank fill to 0.12 wt% per day at 10% tank fill.

Highlights

  • The necessity of liquefied natural gas (LNG) is continuously rising to produce power sources and fulfill transportation needs around the globe

  • Boil-off gas (BOG) generation is mainly caused by the inevitable heat leak to the LNG storage tank, which must be removed from the tanks to maintain their integrity [16]

  • Seismic activity, operational, and environmental conditions, the LNG storage tank can be built as environmentally-friendly in-ground and underground types, to reduce the footprints and psychological impact associated with large tanks

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Summary

Introduction

The necessity of liquefied natural gas (LNG) is continuously rising to produce power sources and fulfill transportation needs around the globe. BOG generation is mainly caused by the inevitable heat leak to the LNG storage tank, which must be removed from the tanks to maintain their integrity [16] Despite their thick composite insulation layers (~1 m thick) [18], LNG storage tanks are not completely immune to heat leakage. A methodology to effectively quantify and manage BOG is required for LNG storage tanks Depending on their applications, LNG storage tanks are designed to be of different sizes [19]. A full containment storage tank is capable of controlling the venting of vapor that arises from product leakage after a credible event (any event that is recognized as sufficiently likely for the system to be designed and operated to withstand) [23] Among these different types of designs, full containment type ( called, full integrity type) tanks are regarded as the most advanced type and have been exploited in several recently completed and ongoing projects [24], in the case of above-ground tanks. The current work is regarded as part 1 for designing full containment type LNG storage tanks

LNG Tank Heat Leakage
Insulation Properties Needed for Heat Leak Calculations
Tank Shell Heat Leakage
Tank Roof Heat Leakage
Tank Bottom Heat Leakage
LNG Regasification
Simulation
BOR Variation with Tank Liquid Level
Impact ofImpact
Section 3.1
Findings
Study Limitations
Unique Findings
Full Text
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