Offshore liquefaction process without compression

Abstract

A process for producing liquid oxygen, including an offshore platform the system including cooling a high-pressure nitrogen gas stream in a main heat exchanger, thereby producing a cooled high-pressure nitrogen gas stream, expanding the cooled high-pressure nitrogen gas stream in a turbo-expander, thereby producing a cold low-pressure nitrogen gas stream, warming the cold low-pressure nitrogen gas stream by indirect heat exchange with a high-pressure gaseous oxygen stream, thereby producing a liquefied oxygen stream and a warm low-pressure nitrogen gas stream, wherein, at least a portion of the warm low-pressure nitrogen gas stream is vented to the atmosphere.

What is claimed is: 
     
         1 . A process for producing liquid oxygen, comprising an offshore platform comprising:
 a) cooling a high-pressure nitrogen gas stream in a main heat exchanger, thereby producing a cooled high-pressure nitrogen gas stream,   b) expanding the cooled high-pressure nitrogen gas stream in a turbo-expander, thereby producing a cold low-pressure nitrogen gas stream,   c) warming the cold low-pressure nitrogen gas stream by indirect heat exchange with a high-pressure gaseous oxygen stream, thereby producing a liquefied oxygen stream and a warm low-pressure nitrogen gas stream,   
       wherein, at least a portion of the warm low-pressure nitrogen gas stream is vented to the atmosphere. 
     
     
         2 . The process of  claim 1 , wherein step b) further comprises:
 i. expanding the cooled high-pressure nitrogen stream in a first turbo-expander, thus producing a first low pressure nitrogen stream,   ii. compressing the first low-pressure nitrogen stream in a nitrogen compressor, thereby producing a hot compressed nitrogen stream,   iii. cooling the hot compressed nitrogen stream in a nitrogen after-cooler, thereby producing a cooled compressed nitrogen stream, and   iv. expanding the cooled compressed nitrogen stream in a second turbo-expander, thus producing the cold low-pressure nitrogen gas stream.   
     
     
         3 . The process of  claim 2 , wherein the nitrogen compressor of step ii is driven by one or both of the expanders of steps i and/or iv. 
     
     
         4 . The process of  claim 2 , wherein at least a portion of the warm low-pressure nitrogen gas is vented to the atmosphere at the end of step  1 . 
     
     
         5 . The process of  claim 1 , wherein the high-pressure nitrogen gas stream has a pressure of greater than 40 bara. 
     
     
         6 . The process of  claim 1 , wherein the high-pressure nitrogen gas stream has a pressure of greater than 60 bara. 
     
     
         7 . The process of  claim 1 , wherein step c) further comprises: warming the cold low-pressure nitrogen gas stream by indirect heat exchange with both:
 i. a high-pressure gaseous oxygen stream, thereby producing a liquefied oxygen stream,   ii. a hydrocarbon comprising stream, thereby producing a liquefied hydrocarbon comprising stream, and   iii. producing a warm low-pressure nitrogen gas stream.   
     
     
         8 . The process of  claim 1 , further comprising an air separation unit, wherein the high-pressure nitrogen stream and the high-pressure oxygen stream are produced by the air separation unit. 
     
     
         9 . The process of  claim 8 , wherein the distance between the air separation unit and the offshore platform is greater than 1 mile. 
     
     
         10 . The process of  claim 8 , wherein the distance between the air separation unit and the offshore platform is greater than 5 miles. 
     
     
         11 . The process of  claim 8 , wherein the air separation unit comprises a liquid oxygen pump and a main heat exchanger, and wherein a liquid oxygen stream is compressed in the liquid oxygen pump and vaporized in the main heat exchanger, thereby producing the high-pressure gaseous oxygen stream. 
     
     
         12 . The process of  claim 8 , wherein, the nitrogen and/or oxygen from the air separation unit are compressed by gaseous mechanical compression.