System for enhanced fuel gas composition control in an lng facility
AssigneeConocoPhillips Company
InventorsWeldon L. Ransbarger, Jon M. Mock
Life of this patent
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Abstract
An LNG facility employing an enhanced fuel gas control system. The enhanced fuel gas control system is operable to produce fuel gas having a substantially constant Modified Wobbe Index (MWI) during start-up and steady-state operation of the LNG facility by processing one or more intermediate process streams in a fuel gas separator. In one embodiment, the fuel gas separator employs a hydrocarbon-separating membrane, which can remove heavy hydrocarbons and/or concentrate nitrogen from the incoming process streams.
Claims47
A process for liquefying a natural gas stream in an LNG facility, said process comprising:
- (a) separating a first predominantly methane stream into a first lights stream and a first heavies stream in a fuel gas separator;
- (b) burning a first fuel gas stream comprising at least a portion of said first lights stream in a gas turbine;
- (c) separating a second predominantly methane stream into a second lights stream and a second heavies stream in said fuel gas separator;
- and
- (d) burning a second fuel gas stream comprising at least a portion of said second lights stream in said gas turbine,
- wherein the difference in Modified Wobbe Index (MWI) between said first and said second lights streams is less than the difference in MWI between said first and said second predominantly methane streams.
A process for liquefying a natural gas stream in an LNG facility, said process comprising:
- (a) cooling at least a portion of said natural gas stream via indirect heat exchange in an open-loop methane refrigeration cycle to thereby produce a cooled natural gas stream;
- (b) separating at least a portion of said cooled natural gas stream into a refrigerant stream and a product stream;
- (c) separating at least a portion of said refrigerant stream in a separator comprising a hydrocarbon-separating membrane to thereby produce a nitrogen-rich stream and a nitrogen-depleted stream;
- and
- (d) returning at least a portion of said nitrogen-depleted stream back to said open-loop methane refrigeration cycle.
A process for liquefying a natural gas stream in an LNG facility, said process comprising:
- (a) cooling said natural gas stream in a first refrigeration cycle via indirect heat exchange with a first refrigerant to thereby produce a cooled natural gas stream;
- (b) separating at least a portion of said cooled natural gas stream in a fuel gas separator comprising a hydrocarbon-separating membrane to thereby produce a nitrogen-rich stream and a nitrogen-depleted stream;
- and
- (c) burning at least a portion of said nitrogen-rich stream in a gas turbine, wherein said gas turbine is used to power a refrigerant compressor of said first refrigeration cycle.
An LNG facility for liquefying a natural gas stream flowing from a natural gas feed inlet of said LNG facility to an LNG outlet of said LNG facility, said LNG facility comprising:
- a main flow path for transporting at least a portion of said natural gas stream from said natural gas feed inlet to said LNG outlet;
- an open-loop refrigeration cycle operable to cool said natural gas stream flowing along said main flow path;
- and
- a fuel gas separator defining a feed gas inlet, a fuel gas outlet, and a heavies outlet,
- wherein said LNG facility is shiftable between a start-up configuration where said feed gas inlet is in fluid flow communication with said main flow path upstream of said open-loop refrigeration cycle and a steady-state configuration where said feed gas inlet is in fluid flow communication with said open-loop refrigeration cycle.
Dependencies are inferred from the claim text.