Method and apparatus for cooling a hydrocarbon stream

Patent metadata

Field	Value
Publication number	US-10012432-B2
Application number	US-66855308-A
Country	US
Kind code	B2
Filing date	Jul 10, 2008
Priority date	Jul 12, 2007
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

A mixed refrigerant stream ( 10 ) comprising a first mixed refrigerant is passed through one or more heat exchangers ( 12 ) to provide a cooled mixed refrigerant stream ( 20 ). At least a fraction of a cooling stream ( 30 ) comprising a second mixed refrigerant is expanded ( 14 ) to provide one or more expanded cooling streams ( 40 a ), at least one of which may be passed through one or more of the heat exchangers ( 12 ), to cool the mixed refrigerant stream ( 10 ) thereby providing the cooled mixed refrigerant stream ( 20 ) which is used to cool ( 22 ) a hydrocarbon stream ( 70 ). The temperature (T 1 ) and the flow (F 1 ) of at least part of the cooled mixed refrigerant stream ( 20 ) is monitored, and the flow (F 2 ) of the cooling stream ( 30 ) is controlled using the flow F 1 and the temperature T 1.

First claim

What is claimed is:

1. A method of cooling a hydrocarbon stream comprising the steps of:
(a) providing a first mixed refrigerant stream comprising a first mixed refrigerant;
(b) using at least one first compressor driven by at least one first compressor driver maintained at a constant first speed for passing the first mixed refrigerant stream through one or more first heat exchangers to provide a cooled first mixed refrigerant stream;
(c) monitoring the temperature (T 1 ) and the flow rate (F 1 ) of at least part of the cooled first mixed refrigerant stream, and passing measured values of the temperature (T 1 ) and the flow rate (F 1 ) to a controller;
(d) using at least one second compressor driven by at least one second compressor driver maintained at a constant second speed for providing a second mixed refrigerant stream comprising a second mixed refrigerant, wherein the average molecular weight of the second mixed refrigerant stream is greater than the average molecular weight of the first mixed refrigerant stream;
(e) monitoring the flow rate (F 2 ) of at least part of the second mixed refrigerant stream provided in step (d), and passing a measured value of the flow rate (F 2 ) to the controller;
(f) passing at least a first fraction of the second mixed refrigerant stream through an expander to provide one or more expanded second mixed refrigerant streams;
(g) passing a second fraction of the second mixed refrigerant stream into a different one or more of the first heat exchangers than the first fraction, and passing at least one of the one or more expanded second mixed refrigerant streams through one or more of the first heat exchangers to cool the first mixed refrigerant stream thereby providing the cooled first mixed refrigerant stream;
(h) controlling the temperature of the cooled first mixed refrigerant stream by controlling the flow rate (F 2 ) of the second mixed refrigerant stream by controlling the expander with the controller;
(i) using the cooled first mixed refrigerant stream to cool the hydrocarbon stream, wherein step (i) comprises: (i1) passing the cooled first mixed refrigerant stream through at least one main heat exchanger and (i2) passing the hydrocarbon stream through the at least one main heat exchanger to be cooled by the cooled first mixed refrigerant stream or at least part thereof.

2. The method as claimed in claim 1 , wherein at least a part of the second mixed refrigerant stream also passes through the one or more of the first heat exchangers in step (b), to provide one or more cooler second mixed refrigerant streams prior to passing at least a fraction of the second mixed refrigerant stream through the expander in step (f).

3. The method as claimed in claim 2 , wherein the flow rate (F 2 ) of at least part of the second mixed refrigerant stream is monitored as the flow rate of at least part of a cooler second mixed refrigerant stream.

4. The method as claimed in claim 1 , wherein, prior to step (i), the first mixed refrigerant stream is passed through any number from 1 to 6 first heat exchangers, and wherein a different expanded second mixed refrigerant stream of the one or more expanded second mixed refrigerant streams from step (f) is passed through each first heat exchanger cooling the first mixed refrigerant stream.

5. The method as claimed in claim 4 , wherein the temperature (T 1 a , T 1 b ) and the flow rate (F 1 a , F 1 b ) of the cooled first mixed refrigerant stream is monitored downstream of each of the first heat exchangers.

6. The method as claimed in claim 1 , wherein the hydrocarbon stream also passes through at least one of the first heat exchangers prior to step (i).

7. The method as claimed in claim 1 , wherein, prior to step (i), the cooled first mixed refrigerant stream is separated into a lighter stream and a heavier stream.

8. The method as claimed in claim 7 , wherein the using, in step (i), of the cooled first mixed refrigerant stream to cool the hydrocarbon stream comprises heat exchanging the hydrocarbon stream against the lighter stream and the heavier stream.

9. The method as claimed in claim 7 , wherein monitoring the flow rate (F 1 ) of at least part of the cooled first mixed refrigerant stream comprises monitoring the flow rate (F 3 ) of the heavier stream.

10. The method as claimed in claim 9 , wherein the heavier stream defines the at least part of the cooled first mixed refrigerant stream.

11. The method as claimed in claim 1 , wherein the hydrocarbon stream is liquefied in the main heat exchanger during the passing of the hydrocarbon stream through the at least one main heat exchanger, to provide a liquefied hydrocarbon stream, such as liquefied natural gas.

12. The method of claim 1 , comprising:
maintaining the at least one first compressor driver at a constant first speed, the constant first speed being full speed of the first compressor driver, and
maintaining the at least one second compressor driver at a constant second speed, the second speed being full speed of the second compressor driver.

Assignees

• Chantant Francois
• Van Dijk Frederick Jan
• Jager Marco Dick
• Shell Oil Co

Inventors

• Chantant François
• Van Dijk Frederick Jan
• Jager Marco Dick

Classifications

• F25J1/0244

  Operation; Control and regulation; Instrumentation (F25J1/0279 takes precedence) · CPC title

• F25J1/0042

  by liquid expansion with extraction of work · CPC title

• F25J1/0057

  after expansion of the liquid refrigerant stream with extraction of work · CPC title

• F25J1/0214

  as a dual level refrigeration cascade with at least one MCR cycle · CPC title

• F25J1/0052

  by vaporising a liquid refrigerant stream · CPC title