Process for producing a pressurized liquefied gas product by cooling and expansion of a gas stream in the supercritical state

A process for producing a liquid gas product comprising:

• (a) providing a gas stream having a pressure of at least 9,315 kPa (1350 psia);
• (b) cooling the gas stream to create a supercritical dense phase fluid stream;
• (c) withdrawing a portion of the supercritical dense phase fluid stream and expanding the withdrawn supercritical dense phase fluid stream and using the expanded stream to provide a portion of the cooling for step b;
• (d) expanding the remaining portion of the cooled supercritical dense phase fluid stream to a lower pressure and a temperature below the critical temperature of the gas stream to produce a liquefied product;
• and
• (e) recycling a portion of the liquefied product to provide a portion of the cooling for step b.

A process for liquefying a pressurized gas stream, which comprises:

• (a) withdrawing a first fraction of the pressurized gas stream thereby leaving a second fraction and expanding the withdrawn first fraction to a lower pressure to cool and at least partially liquefy the withdrawn first fraction;
• (b) cooling the 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;
• (d) removing a portion of the liquefied second fraction from the process as a pressurized product stream having a pressure at or above its bubble point pressure;
• and
• (e) recycling a portion of the liquefied second fraction from the pressurized product stream to provide a portion of the cooling in step (b).

A process for liquefying a pressurized gas stream to create a pressurized liquefied gas product by compressing, cooling and expansion of the gas stream in the supercritical region of the phase diagram at temperatures lower than the critical temperature of the stream, comprising:

• (a) compressing a gas stream to a pressure of at least 9,315 kPa (1,350 psia) and cooling the gas stream to a temperature of at least 41° C. (105° F.);
• (b) cooling the pressurized gas stream in a first heat exchanger by indirect heat exchange with the expanded first fraction from step (c) and the vapor and pressurized liquefied gas product from step (h);
• (c) withdrawing a first fraction from the cooled gas stream of step (b), thereby leaving a second fraction of the pressurized gas stream, and expanding the withdrawn first fraction to a lower pressure to cool and at least partially liquefy the first fraction;
• (d) cooling the second fraction of the pressurized gas stream in a second heat exchanger by indirect heat exchange with the vapor and pressurized liquefied gas product from step (h);
• (f) pressure expanding the second fraction to a lower pressure, thereby at least partially liquefying the second fraction of the pressurized gas stream;
• (g) passing the expanded second 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 and a portion of the liquefied gas product from the phase separator and passing the vapor and the pressurized liquefied gas product in succession through the second heat exchanger and then the first heat exchanger;
• (i) compressing and cooling the vapor and pressurized liquefied gas exiting the first heat exchanger and returning the compressed, cooled vapor and pressurized liquefied gas to the pressurized stream for recycling;
• and
• (j) removing from the phase separator a pressurized liquefied product.

A process for liquefying a pressurized gas stream to create a pressurized liquefied gas product by compressing, cooling and expansion of the gas stream in the supercritical region of the phase diagram at temperatures lower than the critical temperature of the stream, comprising:

• (a) compressing a gas stream to a pressure of at least 9,315 kPa (1,350 psia) and cooling the gas stream to a temperature of at least 41° C. (105° F.);
• (b) cooling the pressurized gas stream in a first heat exchanger by indirect heat exchange;
• (c) withdrawing a first fraction from the cooled gas stream of step (b), thereby leaving a second fraction of the pressurized gas stream, and expanding the withdrawn first fraction to a lower pressure to cool and at least partially liquefy the first fraction in step (b);
• (d) cooling the second fraction of the pressurized gas stream in a second heat exchanger by indirect heat exchange;
• (e) pressure expanding the second fraction to a lower pressure, thereby at least partially liquefying the second fraction of the pressurized gas stream;
• (f) passing the expanded second fraction of step (f) to a phase separator which separates vapor produced by the expansion of step (f) from liquid produced by such expansion;
• (g) removing vapor and a portion of the liquefied gas product from the phase separator and passing the vapor and the pressurized liquefied gas product in succession through the second heat exchanger in step (d) and then the first heat exchanger in step (b);
• (h) compressing and cooling the vapor and pressurized liquefied gas exiting the first heat exchanger and returning the compressed, cooled vapor and pressurized liquefied gas to the pressurized stream for recycling;
• and
• (i) removing from the phase separator a pressurized liquefied product.

An apparatus for liquefying a gas stream, comprising:

• (a) means for compressing the gas stream to the supercritical dense phase region of its phase diagram;
• (b) means for cooling the fluid without traversing the gas stream's critical point during cooling;
• (c) means for expanding the fluid without traversing the gas stream's critical point during expansion;
• (d) means for removing the expanded gas stream as a liquid product;
• and
• (e) means for recycling a portion of the liquefied product to provide a portion of the cooling for step (b).