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US 7,234,322 B2Granted
LNG system with warm nitrogen rejection
AssigneeConocoPhillips Company
InventorsPaul R. Hahn, Philip D. Ritchie, Jame Yao, Rong-Jwyn Lee, Anthony P. Eaton, William R. Low
Life of this patent
Estimating the term…
Abstract
Natural gas liquefaction system employing an enhanced nitrogen removal system capable of removing nitrogen from a relatively warm natural gas stream.
Claims86
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) warming a predominantly methane stream in a methane cold box to thereby provide a warmed predominantly methane stream;
- (b) conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit;
- and
- (c) removing nitrogen from said at least a portion of the warmed predominantly methane stream in the nitrogen removal unit to thereby provide a first nitrogen-reduced stream,
- wherein the temperature of the warmed predominantly methane stream introduced into the nitrogen removal unit is at least about 10° F. warmer than the temperature of said predominantly methane stream subjected to warming in said methane cold box.
2 more elements
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) warming a predominantly methane stream in a methane cold box to thereby provide a warmed predominantly methane stream;
- (b) conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit;
- (c) removing nitrogen from said at least a portion of the warmed predominantly methane stream in the nitrogen removal unit to thereby provide a first nitrogen-reduced stream;
- (d) splitting the warmed predominantly methane stream into a first portion and a second portion;
- and
- (e) conducting the first portion to a first inlet of a methane compressor, step (b) including conducting the second portion to the nitrogen removal unit.
3 more elements
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) warming a predominantly methane stream in a methane cold box to thereby provide a warmed predominantly methane stream;
- (b) conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit;
- (c) removing nitrogen from said at least a portion of the warmed predominantly methane stream in the nitrogen removal unit to thereby provide a first nitrogen-reduced stream;
- and
- (d) upstream of the methane cold box, cooling at least a portion of the predominantly methane stream in a first refrigeration cycle employing a first refrigerant comprising predominantly C1–C3 hydrocarbons, carbon dioxide, or mixtures thereof.
2 more elements
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) warming a predominantly methane stream in a methane cold box to thereby provide a warmed predominantly methane stream;
- (b) conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit;
- and
- (c) removing nitrogen from said at least a portion of the warmed predominantly methane stream in the nitrogen removal unit to thereby provide a first nitrogen-reduced stream,
- said warmed predominantly methane stream having a temperature of −50° F. or warmer.
2 more elements
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) warming a predominantly methane stream in a methane cold box to thereby provide a warmed predominantly methane stream;
- (b) conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit;
- and
- (c) removing nitrogen from said at least a portion of the warmed predominantly methane stream in the nitrogen removal unit to thereby provide a first nitrogen-reduced stream,
- said warmed predominantly methane stream having a temperature of 25° F. or warmer.
2 more elements
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) warming a predominantly methane stream in a methane cold box to thereby provide a warmed predominantly methane stream;
- (b) conducting at least a portion of the warmed predominantly methane stream from the methane cold box to a nitrogen removal unit;
- and
- (c) removing nitrogen from said at least a portion of the warmed predominantly methane stream in the nitrogen removal unit to thereby provide a first nitrogen-reduced stream,
- steps (a), (b), and (c) being are carried out in a cascade-type LNG facility having at least three sequential cooling cycles, each employing a different refrigerant.
2 more elements
A method of liquefying a natural gas stream, said method comprising the steps of:
- (a) cooling the natural gas stream by indirect heat exchange to thereby provide a cooled natural gas stream;
- (b) reducing the pressure of at least a portion of the cooled natural gas stream to thereby provide an expanded natural gas stream;
- (c) warming at least a portion of the expanded natural gas stream via indirect heat exchange with the natural gas stream cooled in step (a) to thereby provide a warmed expanded natural gas stream;
- and
- (d) removing nitrogen from at least a portion of the warmed expanded liquefied natural gas stream.
2 more elements
A method of operating a LNG facility, said method comprising the steps of:
- (a) introducing a warmed predominantly methane stream having a temperature warmer than about −50° F. into a nitrogen removal unit;
- (b) removing nitrogen from the warmed predominantly methane stream in the nitrogen removal unit;
- and
- (c) prior to step (a), warming the warmed predominantly methane stream via indirect heat exchange with a cooled predominantly methane stream.
1 more element
A method of operating a LNG facility, said method comprising the steps of:
- (a) introducing a warmed predominantly methane stream having a temperature warmer than about −50° F. into a nitrogen removal unit;
- and
- (b) removing nitrogen from the warmed predominantly methane stream in the nitrogen removal unit,
- step (b) including the substeps of:
- (b1) cooling the warmed predominantly methane stream by indirect heat exchange in a first heat exchanger to thereby provide a first cooled stream;
- (b2) separating at least a portion of the first cooled stream into a first separated stream and a second separated stream using a first vessel, said first separated stream containing a higher molar percentage of nitrogen than
- said first cooled stream, said second separated stream containing a lower molar percentage of nitrogen than said first cooled stream;
- (b3) separating at least a portion of the first separated stream into a third separated stream and a fourth separated stream using a second vessel, said third separated stream containing a higher molar percentage of nitrogen than said at least a portion of first separated stream, said fourth separated stream containing a lower molar percentage of nitrogen than said at least a portion of first separated stream;
- and
- (b4) using at least a portion of the fourth separated stream to cool the predominantly methane stream by indirect heat exchange in the first heat exchanger.
7 more elements
A method of operating a LNG facility, said method comprising the steps of:
- (a) introducing a warmed predominantly methane stream having a temperature warmer than about −50° F. into a nitrogen removal unit;
- and
- (b) removing nitrogen from the warmed predominantly methane stream in the nitrogen removal unit,
- step (b) including the substeps of:
- (b1) cooling the warmed predominantly methane stream by indirect heat exchange to thereby provide a first cooled stream;
- (b2) splitting at least a portion of the first cooled stream into a first split portion and a second split portion;
- (b3) conducting at least a portion of the first split portion to a lower section of a first stripper column;
- (b4) further cooling at least a portion of the second split portion by indirect heat exchange to thereby provide a second cooled stream;
- and
- (b5) conducting at least a portion of the second cooled stream to an upper section of the first stripper column.
7 more elements
A method of operating a LNG facility, said method comprising the steps of:
- (a) introducing a warmed predominantly methane stream having a temperature warmer than about −50° F. into a nitrogen removal unit;
- and
- (b) removing nitrogen from the warmed predominantly methane stream in the nitrogen removal unit,
- said nitrogen removal unit comprising:
- a high-stage indirect heat exchanger having a first high-stage cooling pass and a first high-stage warming pass;
- and
- a low-stage heat exchanger having a first low-stage cooling pass and a first low-stage warming pass, said first high-stage warming pass being configured to receive fluid flow from the first low-stage warming pass.
4 more elements
A method of operating a LNG facility, said method comprising the steps of:
- (a) introducing a warmed predominantly methane stream having a temperature warmer than about −50° F. into a nitrogen removal unit;
- and
- (b) removing nitrogen from the warmed predominantly methane stream in the nitrogen removal unit,
- steps (a) and (b) being carried out in a cascade-type LNG facility having at least three sequential cooling cycles, each employing a different refrigerant.
1 more element
A method of removing nitrogen from a predominantly methane stream, said method comprising the steps of:
- (a) cooling the predominantly methane stream by indirect heat exchange in a first heat exchanger to thereby provide a first cooled stream, wherein the temperature of said predominantly methane stream introduced into said first heat exchanger is warmer than about −50° F.;
- (b) separating at least a portion of the first cooled stream into a first separated stream and a second separated stream using a first vessel, said first separated stream containing a higher molar percentage of nitrogen than said first cooled stream,
- said second separated stream containing a lower molar percentage of nitrogen than said first cooled stream;
- (c) separating at least a portion of the first separated stream into a third separated stream and a fourth separated stream using a second vessel, said third separated stream containing a higher molar percentage of nitrogen than said at least a portion of the first separated stream, said fourth separated stream containing a lower molar percentage of nitrogen than said at least a portion of the first separated stream;
- and
- (d) using at least a portion of the fourth separated stream to cool the predominantly methane stream by indirect heat exchange in the first heat exchanger.
3 more elements
A method of removing nitrogen from a predominantly methane stream, said method comprising the steps of:
- (a) cooling the predominantly methane stream by indirect heat exchange to thereby provide a first cooled stream;
- (b) splitting at least a portion of the first cooled stream into a first split portion and a second split portion;
- (c) conducting at least a portion of the first split portion to a lower section of a first stripper column;
- (d) further cooling at least a portion of the second split portion by indirect heat exchange to thereby provide a second cooled stream;
- and
- (e) conducting at least a portion of the second cooled stream to an upper section of the first stripper column.
3 more elements
An apparatus for liquefying a predominantly methane stream, said apparatus comprising:
- (a) a methane cold box including a first cold box inlet and a first cold box outlet;
- (b) a methane compressor including a first compressor inlet and a first compressor outlet, said first compressor inlet being configured to receive fluid flow from the first cold box outlet;
- and
- (c) a nitrogen removal unit including a nitrogen removal unit inlet, said nitrogen removal unit inlet being configured to receive a drawn-off portion of the predominantly methane stream flowing from the first cold box outlet to the first compressor inlet.
1 more element
An apparatus for removing nitrogen from a predominantly methane stream, said apparatus comprising:
- (a) a high-stage indirect heat exchanger having a first high-stage cooling pass and a first high-stage warming pass;
- (b) a low-stage indirect heat exchanger having a first low-stage cooling pass and a first low-stage warming pass, said first high-stage warming pass being configured to receive fluid flow from said first low-stage warming pass;
- and
- (c) a high-stage column having an upper high-stage inlet and lower high-stage inlet, said lower high-stage inlet being configured to receive fluid flow from the first high-stage cooling pass.
1 more element
An apparatus for removing nitrogen from a predominantly methane stream, said apparatus comprising:
- (a) a high-stage indirect heat exchanger having a first high-stage cooling pass and a first high-stage warming pass;
- (b) a low-stage indirect heat exchanger having a first low-stage cooling pass and a first low-stage warming pass, said first high-stage warming pass being configured to receive fluid flow from said first low-stage warming pass;
- and
- (c) a nitrogen cold box housing the high-stage and low-stage indirect heat exchangers.
1 more element
Dependencies are inferred from the claim text.