US 6,378,330 B1 · Process for making pressurized liquefied natural gas from pressured natural gas using expansion cooling

Abstract

This invention relates to process for liquefying a pressurized gas stream rich in methane. In a first step of the process, a first fraction of a pressurized feed stream, preferably at a pressure above 11,000 kPa, is withdrawn and entropically expanded to a lower pressure to cool and at least partially liquefy the withdrawn first fraction. A second fraction of the feed stream is cooled by indirect heat exchange with the expanded first fraction. The second fraction is subsequently expanded to a lower pressure, thereby at least partially liquefying the second fraction of the pressurized gas stream. The liquefied second fraction is withdrawn from the process as a pressurized product stream having a temperature above −112° C. and a pressure at or above its bubble point pressure.

Claims24

Dependent claims

A process for liquefying a pressurized gas stream rich in methane, which comprises the steps of:

(a) withdrawing a first fraction of the pressured gas stream and entropically expanding the withdrawn first fraction to a lower pressure to cool and at least partially liquefy the withdrawn first fraction;
(b) cooling a second fraction of the pressurized gas stream by indirect heat exchange with the expanded first fraction;
(c) expanding the second fraction of the pressurized gas stream to a lower pressure, thereby at least partially liquefying the second fraction of the pressurized gas stream;
and
(d) removing the liquefied second fraction from the process as a pressurized product stream having a temperature above −112° C. (−170° F.) and a pressure at or above its bubble point pressure.

2 more elements

A process for liquefying a pressurized gas stream rich in methane, which comprises the steps of:

(a) withdrawing a first fraction of the pressurized gas stream and expanding the withdrawn first fraction to a lower pressure to cool the withdrawn first fraction;
(b) cooling a second fraction of the pressurized gas stream in a first heat exchanger by indirect heat exchange against the expanded first fraction;
(c) withdrawing from the second fraction a third fraction, thereby leaving a fourth fraction of the pressurized gas stream, and expanding the withdrawn third fraction to a lower pressure to cool and at least partially liquefy the withdrawn third fraction;
(d) cooling the fourth fraction of the pressurized gas stream in a second heat exchanger by indirect heat exchange with the at least partially-liquefied third fraction;
(e) further cooling the fourth fraction of step (d) in a third heat exchanger;
(f) pressure expanding the fourth fraction to a lower pressure, thereby at least partially liquefying the fourth fraction of the pressurized gas stream;
(g) passing the expanded fourth fraction of step (f) to a phase separator which separates vapor produced by the expansion of step (f) from liquid produced by such expansion;
(h) removing vapor from the phase separator and passing the vapor in succession through the third heat exchanger, the second heat exchanger and the first heat exchanger;
(i) compressing and cooling the vapor exiting the first heat exchanger and returning the compressed, cooled vapor to the pressurized stream for recycling;
and
(j) removing from the phase separator the liquefied fourth fraction as a pressurized product stream having a temperature above −112° C. (−170° F.) and a pressure at or above its bubble point pressure.

8 more elements

A process for liquefying a pressurized gas stream rich in methane, which comprises the steps of:

(a) withdrawing from the pressured gas stream a first fraction and passing the withdrawn first fraction through a first heat exchanger to cool the first fraction;
(b) withdrawing from the pressured gas stream a second fraction, thereby leaving a third fraction of the pressurized gas stream, and expanding the withdrawn second fraction to a lower pressure to cool the withdrawn second fraction;
(c) cooling the third fraction of the pressurized gas stream in a second heat exchanger by indirect heat exchange with the cooled second fraction;
(d) withdrawing from the cooled third fraction a fourth fraction, thereby leaving a fifth fraction of the pressurized gas stream, and expanding the withdrawn fourth fraction to a lower pressure to cool and at least partially liquefy the withdrawn fourth fraction;
(e) cooling the fifth fraction of the pressurized gas stream in a third heat exchanger by indirect heat exchange with the expanded fourth fraction;
(f) combining the cooled first fraction and the cooled fifth fraction to form a combined stream;
(g) pressure expanding the combined stream to a lower pressure, thereby at least partially liquefying the combined stream, and passing the expanded combined stream to a phase separator which separates vapor produced by the expansion from liquid produced by the expansion;
(h) removing vapor from the phase separator and passing the vapor through the first heat exchanger to provide cooling of the first withdrawn fraction;
and
(i) removing liquid from the phase separator as a product stream having a temperature above −112° C. (−170° F.) and a pressure at or above its bubble point pressure.

7 more elements

Dependencies are inferred from the claim text.

Process for making pressurized liquefied natural gas from pressured natural gas using expansion cooling

Life of this patent

Process for making pressurized liquefied natural gas from pressured natural gas using expansion cooling

Life of this patent

Abstract

Claims24