Reliquefaction of boil-off from liquefied natural gas

Patent · Tue Jul 04 04:00:00 EDT 1989

OSTI ID:5386041

Stuber, W G; Kovak, K W

This patent describes a process for liquifying boil-off gas resulting from the evaporation of liquified natural gas contained in a storage vessel, the boil-off gas being cooled and liquified in a closed-loop nitrogen refrigeration system and then returned to the storage vessel. The closed loop refrigeration system comprises the following steps: compressing nitrogen as a working fluid in a multi-stage compressor system having an initial and final stage to form a compressed working fluid; splitting the compressed working fluid into a first and second stream; isenthalpically expanding the first stream to produce a cooled first stream, then warming against recycle compressed working fluid and boil-off gas; isentropically expanding the second stream to form a cooled expanded stream which is then warmed against boil-off gas and working fluid prior to return to the compressor system; the improvement for reliquefying a boil-off gas containing from about 0 to 10% nitrogen by volume. It comprises: effecting isenthalpic expansion of the first stream under conditions such that at least a liquid fraction is generated; separating any vapor fraction, if generated, from the liquid fraction; warming the vapor fraction, if generated, against boil-off gas and recycle compressed working fluid; pressurizing the liquid fraction formed by pumping; warming the pressurized liquid fraction first against boil-off gas and then in parallel with the warming of the isentropically expanded second stream.

• Assignee: Air Products and Chemicals, Inc., Allentown, PA
• Patent Number(s): US 4843829
• Application Number: PPN: US 7-266729A
• OSTI ID: 5386041
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030300* -- Natural Gas-- Drilling
Production
& Processing
035000 -- Natural Gas-- Storage-- (1989-)
COMPRESSORS
COOLING
ELEMENTS
ENERGY SOURCES
EVAPORATION
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
LIQUEFACTION
LIQUEFIED GASES
LIQUEFIED NATURAL GAS
NATURAL GAS
NITROGEN
NONMETALS
PHASE TRANSFORMATIONS
REFRIGERATORS
STORAGE
THERMOCHEMICAL PROCESSES
VAPORS