Method For Producing Pressurized Gaseous Oxygen Through The Cryogenic Separation Of Air

Abstract

A method is provided for production of gaseous oxygen at moderate pressures by splitting a main air feed into at least three separate streams, with the first stream being fed to a heat exchanger and then a column system for rectification; the second stream being further compressed in a warm booster, partially cooled in the heat exchanger, expanded in a turbine coupled to the warm booster and then fed to the column system; the third stream being expanded in a warm expander before being introduced to the heat exchanger and introduced to the column system. In certain embodiments, substantially all of the main air feed is eventually introduced to the column system for rectification, resulting in reduced sizing of a main air compressor and improved product recoveries.

We claim: 
     
         1 . A method for producing pressurized gaseous oxygen through the cryogenic separation of air, the method comprising the steps of:
 obtaining a main air feed comprising filtered and compressed air;   splitting the main air feed into at least a first air fraction, a second air fraction, and a third air fraction;   fully cooling the first air fraction in a heat exchanger to a temperature suitable for rectification of the first air fraction to form a cooled air feed;   withdrawing the cooled air feed from the heat exchanger and introducing the cooled air feed to a column system under conditions effective for rectification of the cooled air feed into low pressure gaseous nitrogen (LP GAN), liquid oxygen (LOX), liquid nitrogen (LIN), and high pressure gaseous nitrogen (HP GAN), wherein the column system comprises a double column having a higher pressure column and a lower pressure column;   warming the LP GAN, LOX, and HP GAN in the heat exchanger;   boosting the second air fraction in a warm booster to form a boosted second air fraction;   partially cooling the boosted second air fraction in the heat exchanger and then expanding the boosted second air fraction in a turbine to form an expanded second air fraction;   introducing the expanded second air fraction to the column system;   expanding the third air fraction using a warm expander to create an expanded third air fraction; and   cooling the expanded third air fraction in the heat exchanger before introducing the expanded third air fraction to the column system for rectification.   
     
     
         2 . The method as claimed in  claim 1 , wherein the expanded second air fraction is at about the same pressure as the higher pressure column. 
     
     
         3 . The method as claimed in  claim 1 , wherein the main air feed has a pressure of least 10 bar 
     
     
         4 . The method as claimed in  claim 1 , wherein the main air feed has a pressure of at least 20 bar 
     
     
         5 . The method as claimed in  claim 1 , wherein the turbine is coupled to the warm booster. 
     
     
         6 . The method as claimed in  claim 1 , wherein the warm expander is not coupled to a booster. 
     
     
         7 . The method as claimed in  claim 1 , further comprising withdrawing LIN from the column system as product. 
     
     
         8 . The method as claimed in  claim 1 , wherein the step of splitting the main air feed further includes the step of splitting the main air feed into a fourth air fraction, and the method further comprises the steps of:
 expanding the fourth air fraction across a pressure valve; and then introducing the fourth air fraction into the heat exchanger for cooling before introducing the fourth air fraction to the column system.   
     
     
         9 . The method as claimed in  claim 1 , wherein the LOX is vaporized in the heat exchanger and has a pressure of about 5-15 bar after being warmed in the heat exchanger. 
     
     
         10 . The method as claimed in  claim 1 , wherein substantially all of the main air feed is introduced to the column system for rectification. 
     
     
         11 . The method as claimed in  claim 1 , wherein substantially none of the main air feed is vented to the atmosphere. 
     
     
         12 . The method as claimed in  claim 1 , wherein the third air fraction is at substantially the same pressure as the second air fraction and the first air fraction.