Method of producing and distributing liquid natural gas

• US 10,006,695 B2
• Filed: 08/19/2013
• Issued: 06/26/2018
• Est. Priority Date: 08/27/2012
• Status: Active Grant

• Current Assignee: 1304338 Alberta, Ltd., 1304342 Alberta, Ltd.
• Original Assignee: 1304338 Alberta, Ltd., 1304342 Alberta, Ltd.
• Inventors: Millar, Mackenzie, Lourenco, Jose
• Primary Examiner(s): Jules, Frantz
• Assistant Examiner(s): KING, BRIAN M
• Application Number:
  US14/424,845
• Publication Number:
  US 20150219392A1
• Time in Patent Office: 1,772 Days
• CPC Class Codes: C10L 3/101 Removal of contaminants
• CPC Class Codes: C10L 3/106 of water
• CPC Class Codes: C10L 3/12 Liquefied petroleum gas liquefying by pressure and cold treatment F25J
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/0037 of a return stream
• CPC Class Codes: F25J 1/004 by flash gas recovery F25J1/0267 takes precedence
• CPC Class Codes: F25J 1/0201 using only internal refrigeration means, i.e. without external refrigeration
• CPC Class Codes: F25J 1/0202 in a quasi-closed internal refrigeration loop F25J1/0208, F25J1/0219, F25J1/0224 take precedence
• CPC Class Codes: F25J 1/023 for the combustion as fuels, i.e. integration with the fuel gas system
• CPC Class Codes: F25J 1/0232 integration within a pressure letdown station of a high pressure pipeline system
• CPC Class Codes: F25J 1/0274 Retrofitting or revamping of an existing liquefaction unit
• CPC Class Codes: F25J 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2220/64 Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general
• CPC Class Codes: F25J 2230/22 Compressor driver arrangement, e.g. power supply by motor, gas or steam turbine
• CPC Class Codes: F25J 2230/30 Compression of the feed stream
• CPC Class Codes: F25J 2240/40 Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
• CPC Class Codes: F25J 2240/70 Steam turbine, e.g. used in a Rankine cycle
• CPC Class Codes: F25J 2240/82 with waste heat recovery, e.g. in a combined cycle, i.e. for generating steam used in a Rankine cycle
• CPC Class Codes: F25J 3/0615 Liquefied natural gas

Abstract

A method for producing liquid natural gas (LNG) includes the following steps. Compressor stations forming part of existing natural-gas distribution network are identified. Compressor stations that are geographically suited for localized distribution of LNG are selected. Natural gas flowing through the selected compressor stations is diverted to provide a high pressure first natural gas stream and a high pressure second natural gas stream. A pressure of the first natural gas stream is lowered to produce cold temperatures through pressure let-down gas expansion and then the first natural gas stream is consumed as a fuel gas for an engine driving a compressor at the compressor station. The second natural gas stream is first cooled with the cold temperatures generated by the first natural gas stream, and then expanded to a lower pressure, thus producing LNG.

Claims

1. A method for producing liquid natural gas (LNG), comprising:

identifying compressor stations forming part of an existing natural gas distribution network, the compressor stations compressing a stream of natural gas flowing through a pipeline;

selecting compressor stations that are geographically suited for localized distribution of LNG;

at selected compressor stations, diverting a high pressure first natural gas stream and a high pressure second natural gas stream from the stream of natural gas flowing through the pipeline;

lowering a pressure of the first natural gas stream to produce cold temperatures through pressure let-down gas expansion and using the first natural gas stream as fuel gas for an internal combustion or turbine engine for a mechanical drive driving a compressor at the compressor station to compress the stream of natural gas flowing through the pipeline; and

cooling the second natural gas stream with the cold temperatures generated through pressure let-down of the first natural gas stream, and then expanding the second natural gas stream to a lower pressure and using the cold temperatures generated through pressure let-down of the second natural gas stream to produce LNG.

2. The method of claim 1, wherein a step is taken of pre-treating the first natural gas stream and the second natural gas stream by removing water before lowering the pressure.

3. The method of claim 2, wherein a step is taken of cooling second natural gas stream that has the water removed and removing hydrocarbon condensates before lowering the pressure.

4. The method of claim 2, wherein a step is taken of removing carbon dioxide from second natural gas stream that has the water removed before lowering the pressure.

5. The method of claim 1, wherein the step of cooling of the second natural gas stream is accomplished by a heat exchange through one or more heat exchangers.

6. The method of claim 3, wherein the step of cooling of the second natural gas stream is affected through a heat exchange with a vapour fraction from the first natural gas stream.

7. The method of claim 1, wherein the high-pressure first natural gas stream and the high pressure second natural gas stream are taken from either a discharge side or a suction side of a compressor.

8. The method of claim 1, wherein the lowering of the pressure of the high pressure first natural gas stream is accomplished by passing the first natural gas stream through a turbo expander.

9. The method of claim 2, wherein the lowering of the pressure of the high pressure second natural gas stream is accomplished by passing the second natural gas stream through one of a turbo expander or a JT valve.

10. The method of claim 3, wherein hydrocarbon condensates removed are captured in knock-out drums.