Method for the integration of a nitrogen liquefier and liquefaction of natural gas for the production of liquefied natural gas and liquid nitrogen

Patent metadata

Field	Value
Publication number	US-2017038136-A1
Application number	US-201615229892-A
Country	US
Kind code	A1
Filing date	Aug 5, 2016
Priority date	Aug 6, 2015
Publication date	Feb 9, 2017
Grant date	—

Abstract

A method for the integration of a nitrogen liquefier and liquefaction of natural gas for the production of liquefied natural gas and liquid nitrogen is provided. The method may include providing a nitrogen liquefaction unit and providing a natural gas liquefaction unit. Liquefaction of the nitrogen can be achieved via a nitrogen refrigeration cycle within the nitrogen liquefaction unit. Liquefaction of the natural gas can be achieved through the use of natural gas letdown and a second nitrogen refrigeration cycle. The two liquefaction units can be integrated via a common nitrogen recycle compressor, thereby providing significant capital savings.

First claim

We claim:

1 . A method for the integration of a nitrogen liquefier and natural gas liquefier for the production of liquefied natural gas (“LNG”) and liquid nitrogen (“LIN”), the method comprising the steps of:
a) providing a nitrogen liquefier having a first nitrogen refrigeration cycle, wherein the nitrogen liquefier comprises a turbine, a booster and a plurality of coolers, wherein the first nitrogen refrigeration cycle is configured to provide refrigeration within a first heat exchanger;
b) providing a second nitrogen refrigeration cycle, wherein the second nitrogen refrigeration cycle comprises a second turbine, a second booster and a plurality of second coolers, wherein the second nitrogen refrigeration cycle is configured to provide refrigeration within a second heat exchanger;
c) purifying a first natural gas stream in a first purification unit to remove a first set of impurities to produce a purified first natural gas stream;
d) cooling and liquefying the first natural gas stream in the second heat exchanger using the refrigeration from the nitrogen refrigeration cycle to produce an LNG stream, wherein the first natural gas stream has an LNG refrigeration requirement, wherein the LNG stream is liquefied at a first pressure P H ;
e) purifying a second natural gas stream in a second purification unit to remove a second set of impurities to produce a purified second natural gas stream;
f) partially cooling the second natural gas stream in the second heat exchanger;
g) withdrawing the partially cooled natural gas stream from an intermediate section of the second heat exchanger;
h) expanding the partially cooled natural gas stream to a medium pressure P M in a natural gas expansion turbine to form a cold natural gas stream, wherein the medium pressure P M is at a pressure lower than the first pressure P H ; and
i) warming the cold natural gas stream in the second heat exchanger by heat exchange against the first natural gas stream to produce a warm natural gas stream at the warm end of the second heat exchanger,
wherein the natural gas expansion turbine drives a first booster,
wherein the LNG refrigeration requirement is supplied by a combination of refrigeration from the second nitrogen refrigeration cycle and step i),
wherein a portion of the liquid nitrogen within the first nitrogen refrigeration cycle is withdrawn as product liquid nitrogen, wherein at least an equal portion of gaseous nitrogen is introduced to the first nitrogen refrigeration cycle as is withdrawn as product liquid nitrogen, and
wherein the first nitrogen refrigeration cycle and the second nitrogen refrigeration cycle share a common nitrogen recycle compressor.

2 . The method as claimed in claim 1 , wherein the first booster is configured to compress the second natural gas stream or a stream derived from the second natural gas stream.

3 . The method as claimed in claim 1 , wherein the first booster is configured to compress a stream selected from the group consisting of the first natural gas stream, the purified first natural gas stream, the second natural gas stream, the purified second natural gas stream, the partially cooled natural gas stream, the warm natural gas stream, and a nitrogen fluid within the nitrogen refrigeration cycle.

4 . The method as claimed in claim 1 , wherein the first set of impurities has a freezing point at or above the liquefaction temperature of methane at the first pressure P H .

5 . The method as claimed in claim 1 , wherein the second set of impurities comprises water.

6 . The method as claimed in claim 1 , wherein the first nitrogen refrigeration cycle further comprises a nitrogen feed compressor.

7 . The method as claimed in claim 1 , wherein the first nitrogen refrigeration cycle is a closed refrigeration cycle.

8 . The method as claimed in claim 1 , wherein the first natural gas stream and the second natural gas stream come from the same natural gas source.

9 . The method as claimed in claim 8 , wherein the natural gas source is a natural gas pipeline having a pressure between 15 and 100 bara.

10 . The method as claimed in claim 1 , wherein the first natural gas stream comes from a first natural gas source, and the second natural gas stream comes from a second natural gas source, wherein the first and second natural gas sources are different sources.

11 . The method as claimed in claim 10 , wherein the first natural gas source comprises a natural gas pipeline.

12 . The method as claimed in claim 11 , wherein the natural gas pipeline has a pressure between 15 and 100 bara.

13 . The method as claimed in claim 1 , wherein the first purification unit and the second purification unit are the same unit.

14 . The method as claimed in claim 1 , wherein the first purification unit and the second purification unit are separate units, wherein the first purification unit is configured to remove at least water and carbon dioxide, and wherein the second purification unit is configured to remove at least water.

15 . The method as claimed in claim 1 , wherein the nitrogen liquefier further comprises a subcooler.

16 . A method for the integration of a first liquefier and a second liquefier for the production of a first liquefied gas and a second liquefied gas, the method comprising the steps of:
a) providing a first liquefier having a first refrigeration cycle, wherein the first liquefier comprises a recycle compressor, a first heat exchanger, and a turbine booster; b) providing a second refrigeration cycle, wherein the second refrigeration cycle is configured to provide refrigeration within a second heat exchanger, c) cooling and liquefying a first gas stream in the second heat exchanger by heat exchange with the second refrigeration cycle to produce a liquefied first gas stream, wherein the liquefied first gas stream is at a first pressure; d) expanding a second gas stream to a second pressure to produce an expanded second gas stream; and e) warming the expanded second gas stream in the second heat exchanger to produce a warmed gas stream, wherein a portion of a first refrigeration gas within the first refrigeration cycle is withdrawn and liquefied yielding a liquid first refrigeration gas product, wherein at least an equal portion of gaseous first refrigeration gas is introduced to the first refrigeration cycle as is withdrawn as liquid first refrigeration gas product, wherein step e), in addition to the refrigeration provided by the second refrigeration cycle, provides the refrigeration used to cool and liquefy the first gas stream, and wherein the first refrigeration cycle and the second refrigeration cycle share a common recycle compressor.

17 . The method as claimed in claim 16 , wherein the first refrigeration cycle is selected from the group consisting of a nitrogen refrigeration cycle and a hydrogen refrigeration cycle.

18 . The method as claimed in claim 16 , wherein the first gas stream liquefied in step c) is derived from the expanded second gas stream, wherein the first pressure and the second pressure are about the same.

19 . The method as claimed in claim 16 , wherein the second refrigeration cycle is selected from the group consisting of a nitrogen refrigeration cycle and a hydrogen refrigeration cycle.

20 . The method as claimed in claim 16 , wherein the first gas stream cooled and liquefied in step c) comprises natural gas.

21 . The method as claimed in claim 16 , wherein the second gas stream expanded in step d) comprises na

Assignees

• Air Liquide

Inventors

• Turney Michael A
• Farges Oriane
• Guillard Alain

Classifications

• F25J1/0202

  in a quasi-closed internal refrigeration loop (F25J1/0208, F25J1/0219, F25J1/0224 take precedence) · CPC title

• F25J2290/34

  Details about subcooling of liquids · CPC title

• F25J1/0052

  by vaporising a liquid refrigerant stream · CPC title

• F25J1/0208 Primary

  in combination with an internal quasi-closed refrigeration loop, e.g. with deep flash recycle loop (F25J1/021 takes precedence) · CPC title

• F25J2210/06

  Splitting of the feed stream, e.g. for treating or cooling in different ways · CPC title