System and method for gas liquefication

Abstract

A method and a system are provided for liquefying an industrial gas. Industrial gas is compressed, at a three-stage feed recycle compressor, to produce a first compressed gas portion and a second compressed gas portion. The second compressed gas portion is further compressed and divided into a first part and a second part. The first compressed gas portion is turbo-expanded to form a first turbo-expanded gas portion. The first turbo-expanded gas portion is warmed, at a heat exchanger, to form a first return stream. The first return stream is fed back to the three-stage feed recycle compressor, between a first compression stage and a second compression stage. A cooled first part is turbo-expanded to form a turbo-expanded first part. The turbo-expanded first part is warmed at the heat exchanger to form a second return stream. The cooled and liquefied second part is recovered as liquefied industrial gas.

What is claimed is: 
     
         1 . A method for liquefying an industrial gas comprising:
 compressing industrial gas, at a three-stage feed recycle compressor, to produce a first compressed gas portion and a second compressed gas portion;   further compressing and dividing the second compressed gas portion into a first part and a second part;   turbo-expanding the first compressed gas portion, at a warm turbine, to form a first turbo-expanded gas portion;   warming the first turbo-expanded gas portion and forming a first return stream, at a heat exchanger, by countercurrent flow indirect heat exchange with the first part and the second part,   feeding back the first return stream from the heat exchanger, to the three-stage feed recycle compressor, between a first compression stage and a second compression stage;   cooling the first part and the second part in the heat exchanger;   turbo-expanding the cooled first part, at a cold turbine, to form a turbo-expanded first part;   warming the turbo-expanded first part, at the heat exchanger, to form a second return stream, by indirect heat exchange with the second part, assisting in liquefying the second part; and   recovering the liquefied second part as liquefied industrial gas.   
     
     
         2 . The method of  claim 1 , further comprising:
 separating a gaseous portion and a liquid portion of the liquefied second part; and   warming the gaseous portion at the heat exchanger by countercurrent indirect heat exchange with the first part and the second part to assist in liquefying the second part.   
     
     
         3 . The method of  claim 2 , further comprising combining the warmed gaseous portion with the first turbo-expanded gas portion at the heat exchanger to form the first return stream. 
     
     
         4 . The method of  claim 1 , wherein, in compressing the industrial gas, the warmed first part is combined with an additional stream from an air separation plant and the industrial gas in the three-stage feed recycle compressor between the second compression stage and a third compression stage. 
     
     
         5 . The method of  claim 1 , wherein the first compressed gas portion and the second compressed gas portion have pressures of approximately 320 pounds per square inch absolute (psia). 
     
     
         6 . The method of  claim 1 , wherein the first turbo-expanded gas portion has a pressure of approximately 33 psia. 
     
     
         7 . The method of  claim 1 , wherein the first return stream has a pressure of approximately 30 psia. 
     
     
         8 . A system for liquefying an industrial gas comprising:
 a three-stage feed recycle compressor for compressing industrial gas to produce a first compressed gas portion and a second compressed gas portion,   a warm booster and a cold booster further compressing the second compressed gas portion, wherein the second compressed gas portion is split into a first part and a second part;   a warm turbine for turbo-expanding the first compressed gas portion to form a first turbo-expanded gas portion;   a heat exchanger for warming the first turbo-expanded gas portion by countercurrent flow indirect heat exchange with the first part and the second part, forming a first return stream that is fed back between a first compression stage and a second compression stage of the three-stage feed recycle compressor, and cooling the first part and the second part; and   a cold turbine for turbo-expanding the cooled first part to form a turbo-expanded first part,   wherein the turbo-expanded first part is warmed at the heat exchanger, to form a second return stream, by indirect heat exchange with the second part to assist in liquefying the second part, and   wherein the liquefied second part is recovered as liquefied industrial gas.   
     
     
         9 . The system of  claim 8 , wherein a gaseous portion and a liquid portion of the liquefied second part are separated, and the gaseous portion is warmed at the heat exchanger by countercurrent indirect heat exchange with the first part and the second part to assist in liquefying the second part. 
     
     
         10 . The system of  claim 9 , wherein the heat exchanger combines the warmed gaseous portion with the first turbo-expanded gas portion to form the first return stream. 
     
     
         11 . The system of  claim 8 , wherein the first compression system combines the warmed first part with an additional stream from an air separation plant and the industrial gas in the three-stage feed recycle compressor between the second compression stage and a third compression stage. 
     
     
         12 . The system of  claim 8 , wherein the first compressed gas portion and the second compressed gas portion have pressures of approximately 320 pounds per square inch absolute (psia). 
     
     
         13 . The system of  claim 8 , wherein the first turbo-expanded gas portion has a pressure of approximately 33 psia. 
     
     
         14 . The method of  claim 8 , wherein the first return stream has a pressure of approximately 30 psia. 
     
     
         15 . The system of  claim 8 , wherein the first turbo-expander is operatively coupled to and configured to drive a warm booster compressor in the compression system. 
     
     
         16 . The system of  claim 1 , wherein the second turbo-expander is operatively coupled to and configured to drive a cold booster compressor in the compression system.