Liquefaction system using a turboexpander

Patent metadata

Field	Value
Publication number	US-2016377340-A1
Application number	US-201514749390-A
Country	US
Kind code	A1
Filing date	Jun 24, 2015
Priority date	Jun 24, 2015
Publication date	Dec 29, 2016
Grant date	—

Abstract

The subject matter disclosed herein relates to a liquefaction system. Specifically, the present disclosure relates to systems and methods for condensing a pressurized gaseous working fluid, such as natural gas, using at least one turboexpander in combination with other cooling devices and techniques. In one embodiment, a turboexpander may be used in combination with a heat exchanger using vapor compression refrigeration to condense natural gas.

First claim

1 . A gas feed liquefaction system, comprising:
a flow path configured to convey a working fluid comprising a vapor in a downstream direction; an initial cooling phase in a first heat exchange relationship with the flow path, wherein the initial cooling phase comprises a heat exchanger; a compressor positioned downstream of the initial cooling phase; a second cooling phase in a second heat exchange relationship with the flow path, wherein the second cooling phase is downstream from the compressor and comprises a first turboexpander and a second turboexpander, and wherein the first and second turboexpanders are configured to condense at least a first portion of the vapor into a liquid; a separation vessel downstream of the second turboexpander and configured to separate a second portion of the vapor from the liquid; and a recycle stream configured to direct the second portion of the vapor through the heat exchanger toward a mixer, wherein the mixer is configured to combine the second portion of the vapor with the flow path upstream of the second cooling phase.

2 . The gas feed liquefaction system of claim 1 , wherein one or both of the first turboexpander and the second turboexpander comprises between 7 and 15 stages.

3 . The gas feed liquefaction system of claim 1 , wherein the second cooling phase comprises a third turboexpander.

4 . The gas feed liquefaction system of claim 1 , wherein the heat exchanger is configured to transfer thermal energy from the flow path to a refrigerant of a vapor compression refrigeration cycle.

5 . The gas feed liquefaction system of claim 1 , comprising an additional separation vessel along the flow path upstream of the compressor and downstream of the initial cooling phase, wherein the additional separation vessel is configured to remove heavy hydrocarbons or contaminants from the flow path.

6 . The gas feed liquefaction system of claim 1 , wherein at least one of the first turboexpander and the second turboexpander are configured to provide power to the compressor.

7 . The gas feed liquefaction system of claim 1 , wherein a pressure ratio across at least one of the first turboexpander and the second turboexpander is between 1 and 5.

8 . The gas feed liquefaction system of claim 1 , wherein a pressure of the flow path upstream of the initial cooling phase is greater than 40 atmosphere.

9 . The gas feed liquefaction system of claim 1 , comprising a moisture removal device upstream of the initial cooling phase.

10 . The gas feed liquefaction system of claim 1 , comprising a third cooling phase upstream of the initial cooling phase, wherein the third cooling phase comprises a vapor compression refrigeration cycle.

11 . The gas feed liquefaction system of claim 10 , wherein the recycle stream is configured to pass through the third cooling phase before entering the mixer.

12 . The gas feed liquefaction system of claim 1 , wherein the first turboexpander is configured to separate the vapor from the liquid and configured to direct the vapor or the liquid to the second turboexpander.

13 . A gas feed liquefaction system, comprising:
a flow path configured to convey a working fluid comprising a vapor in a downstream direction; an initial cooling phase in a first heat exchange relationship with the flow path, wherein the initial cooling phase comprises a heat exchanger; a compressor positioned downstream of the initial cooling phase; a second cooling phase in a second heat exchange relationship with the flow path, wherein the second cooling phase is downstream from the compressor and comprises a first turboexpander and a second turboexpander, and wherein the first and second turboexpanders are configured to condense at least a portion of the vapor into a liquid; a splitter positioned downstream of the first turboexpander and upstream of the second turboexpander, wherein the splitter directs a first stream of the flow path through the heat exchanger and a second stream of the flow path to the second turboexpander; a separation vessel downstream of the second turboexpander and configured to separate a second portion of the vapor from the liquid; and a recycle stream configured to direct the second portion through the heat exchanger to a mixer, wherein the mixer is configured to combine one or more of the first stream, the second portion, and the flow path upstream of the second cooling phase.

14 . The gas feed liquefaction system of claim 13 , wherein one or both of the first turboexpander and the second turboexpander comprises between 7 and 15 stages.

15 . The gas feed liquefaction system of claim 13 , wherein an additional compressor is configured to compress the first stream and direct the first stream towards the mixer.

16 . The gas feed liquefaction system of claim 13 , wherein a pressure ratio across at least one of the first turboexpander and the second turboexpander is between 1 and 5.

17 . A method, comprising:
cooling a fluid along a fluid path using a heat exchanger of an initial cooling phase; compressing the fluid along the fluid path; cooling the fluid along the fluid path using at least one turboexpander of a second cooling phase, wherein the at least one turboexpander is configured to expand the fluid such that a temperature and pressure of the fluid are reduced to generate a fluid stream having both a vapor phase and a liquid phase; separating the vapor phase from the liquid phase using a separator; and combining the vapor phase with the fluid upstream of the second cooling phase.

18 . The method of claim 17 , wherein the at least one turboexpander comprises between 7 and 15 stages.

19 . The method of claim 17 , wherein a pressure ratio across at least one of the first turboexpander and the second turboexpander is between 1 and 5.

20 . The method of claim 17 , wherein a pressure of the fluid upstream of the initial cooling phase is greater than 40 atmosphere.

Assignees

• Gen Electric

Inventors

• Lissianski Vitali Victor
• Hofer Douglas Carl
• Shisler Roger Allen
• Sipoecz Nikolett
• Bi Xianyun

Classifications

• F25J1/0283

  Gas turbine as the prime mechanical driver · CPC title

• F25J2245/02

  Recycle of a stream in general, e.g. a by-pass stream · CPC title

• F25J1/0257

  Construction and layout of liquefaction equipments, e.g. valves, machines (F25J1/0279 takes precedence) · CPC title

• F25J1/0022 Primary

  Hydrocarbons, e.g. natural gas · CPC title

• F25J2240/40

  Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval · CPC title