# US 11,079,176 B2 · Method and system for liquefaction of natural gas using liquid nitrogen

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- Number: US 11,079,176 B2
- Document ID: US11079176B2
- Status: Granted
- Kind: B2
- Application number: 16/262,243
- Filed: 2019-01-30
- Published: 2019-09-19
- Granted: 2021-08-03
- Earliest claimed: 2018-03-14
- Assignees: ExxonMobil Upstream Research Company
- Applicants: Fritz Pierre, Jr.
- Inventors: Fritz Pierre, Jr.
- Web page: https://patentgrep.com/patent/US11079176B2

## CPC

- F25J 3/0257: {separation of nitrogen (from air F25J3/04, production of nitrogen in general C01B21/00)}
- F25J 1/0022: {Hydrocarbons, e.g. natural gas}
- F25J 1/004: {by flash gas recovery (F25J1/0267 takes precedence)}
- F25J 1/005: {by expansion of a gaseous refrigerant stream with extraction of work}
- F25J 1/0221: {using the cold stored in an external cryogenic component in an open refrigeration loop}
- F25J 1/0223: {in combination with the subsequent re-vaporisation of the originally liquefied gas at a second location to produce the external cryogenic component}
- F25J 1/0278: {Unit being stationary, e.g. on floating barge or fixed platform}
- F25J 3/0209: {Natural gas or substitute natural gas}
- F25J 3/0233: {separation of CnHm with 1 carbon atom or more}
- F25J 2200/02: in a single pressure main column system
- F25J 2200/40: Features relating to the provision of boil-up in the bottom of a column
- F25J 2205/02: using simple phase separation in a vessel or drum
- F25J 2205/04: in the feed line, i.e. upstream of the fractionation step
- F25J 2205/30: using a washing, e.g. "scrubbing" or bubble column for purification purposes
- F25J 2205/90: Mixing of components
- F25J 2210/02: Multiple feed streams, e.g. originating from different sources
- F25J 2210/04: Mixing or blending of fluids with the feed stream
- F25J 2210/42: Nitrogen
- F25J 2210/90: Boil-off gas from storage
- F25J 2215/04: Recovery of liquid products
- F25J 2220/62: Separating low boiling components, e.g. He, H2, N2, Air
- F25J 2240/60: Expansion by ejector or injector, e.g. "Gasstrahlpumpe", "venturi mixing", "jet pumps"
- F25J 2245/90: the recycled stream being boil-off gas from storage
- F25J 2270/08: Internal refrigeration by flash gas recovery loop
- F25J 2270/16: with mutliple gas expansion loops of the same refrigerant
- F25J 2270/904: by liquid or gaseous cryogen in an open loop
- F25J 2290/62: Details of storing a fluid in a tank
- F25J: LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS {OR LIQUEFIED GASEOUS} MIXTURES BY PRESSURE AND COLD TREATMENT {OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE (cryogenic pumps F04B37/08; gas storage vessels, gas holders F17; filing vessels with, or discharging from vessels, compressed, liquefied or solidified gases F17C; refrigeration machines, plants, or systems F25B)}

## Abstract

A method for producing liquefied natural gas (LNG) from a natural gas stream having a nitrogen concentration of greater than 1 mol %. At least one liquid nitrogen (LIN) stream is received at an LNG liquefaction facility. The LIN streams may be produced at a different geographic location from the LNG liquefaction facility. A natural gas stream is liquefied by indirect heat exchange with a nitrogen vent stream to form a pressurized LNG stream. The pressurized LNG stream has a nitrogen concentration of greater than 1 mol %. The pressurized LNG stream is directed to one or more stages of a column to produce an LNG stream and the nitrogen vent stream. The column has upper stages and lower stages. The LIN streams are directed to one or more upper stages of the column.

## Claims

### Claim 1

A method for producing liquefied natural gas (LNG) from a natural gas stream having a nitrogen concentration of greater than 1 mol %, where the method comprises:
at an LNG liquefaction facility, receiving a first liquefied nitrogen (LIN) stream and a second LIN stream, the first and second LIN streams being produced at a different geographical location than the LNG liquefaction facility;
liquefying the natural gas stream by indirect heat exchange with a nitrogen vent stream and the second liquefied nitrogen stream to form a pressurized LNG stream, where the pressurized LNG stream has a nitrogen concentration of greater than 1 mol %;
directing the pressurized LNG stream to a jet pump, and using the pressurized LNG stream as a motive fluid for the jet pump;
mixing the pressurized LNG stream and a lower pressure natural gas stream in the jet pump to produce a two-phase LNG stream, wherein the lower pressure natural gas stream has a pressure that is lower than a pressure of the pressurized LNG stream;
separating the two-phase LNG stream into an LNG vapor stream and an LNG liquid stream;
directing the LNG liquid stream to one or more stages of a column, wherein the column is one of a fractionation column, a distillation column, or an absorption column;
directing the LNG vapor stream to one or more lower stages of the column;
directing the first liquefied nitrogen stream to one or more upper stages of the column; and
producing an LNG stream and the nitrogen vent stream from the column.

### Claim 2 (depends on 1)

The method of claim 1, wherein the lower pressure natural gas stream comprises one of
boil-off gas extracted from LNG storage tanks, or boil-off gas extracted from LNG during storage or unloading operations from an LNG carrier ship.

### Claim 3 (depends on 1)

The method of claim 1, further comprising compressing the lower pressure natural gas stream prior to being directed to the column.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
indirectly exchanging heat between the nitrogen vent stream and the natural gas stream to form a warmed nitrogen vent stream.

### Claim 5 (depends on 1)

The method of claim 1, wherein the LNG stream has a nitrogen molar concentration of less than 1 mol %.

### Claim 6

A method for producing liquefied natural gas (LNG) from a natural gas stream having a nitrogen concentration of greater than 1 mol %, where the method comprises:
at an LNG liquefaction facility, receiving one or more liquefied nitrogen (LIN) streams, the one or more LIN streams being produced at a different geographical location than the LNG liquefaction facility;
at least partially liquefying the natural gas stream by indirect heat exchange with a nitrogen vent stream to form a pressurized LNG stream, where the pressurized LNG stream has a nitrogen concentration of greater than 1 mol %;
directing the pressurized LNG stream to a separation vessel to produce an LNG vapor stream and an LNG liquid stream;
directing the LNG vapor stream to a jet pump, and using the LNG vapor stream as a motive fluid for the jet pump;
mixing the LNG vapor stream and a first lower pressure natural gas stream in the jet pump to produce a second lower pressure gas stream, wherein each of the first and second lower pressure natural gas streams have a pressure that is lower than a pressure of the pressurized LNG stream;
directing the LNG liquid stream to one or more stages of a column;
directing the second lower pressure natural gas stream to one or more lower stages of the column;
directing the one or more LIN streams to one or more upper stages of the column; and
producing an LNG stream and the nitrogen vent stream from the column.

### Claim 7 (depends on 6)

The method of claim 6, wherein the lower pressure natural gas stream comprises one of
boil-off gas extracted from LNG storage tanks, or
boil-off gas extracted from LNG during storage or unloading operations from an LNG carrier ship.