Cryogenic air separation process with excess turbine refrigeration

Abstract

A process for carrying out cryogenic air separation wherein liquid oxygen is pressurized and vaporized against condensing feed air to produce oxygen gas product wherein excess plant refrigeration is generated such that the aggregate warm end temperature difference of the process exceeds the minimum internal temperature difference of the primary heat exchanger by at least 2K.

1 . In a process for the cryogenic separation of feed air wherein feed air is cooled in a primary heat exchanger, is separated by cryogenic rectification in at least one column to produce oxygen-rich liquid and nitrogen-rich vapor, oxygen-rich liquid is increased in pressure, and the pressurized oxygen-rich liquid is vaporized by indirect heat exchange with at least some of the feed air to produce product oxygen, the improvement comprising generating sufficient excess refrigeration beyond that required to carry out the cryogenic rectification such that the aggregate warm end temperature difference of the process exceeds the minimum internal temperature difference of the primary heat exchanger by at least 2K.  
   
   
       2 . The process of  claim 1  wherein at least some of the refrigeration is generated by turboexpansion of nitrogen-rich vapor.  
   
   
       3 . The process of claim wherein at least some of the refrigeration is generated by turboexpansion of feed air.  
   
   
       4 . The process of  claim 3  wherein the feed air which undergoes turboexpansion is liquefied feed air.  
   
   
       5 . The process of  claim 1  wherein the aggregate warm end temperature difference exceeds the minimum internal temperature difference by at least 3K.  
   
   
       6 . The process of  claim 1  wherein the aggregate warm end temperature difference exceeds the minimum internal temperature difference by at least 4K.  
   
   
       7 . The process of  claim 1  wherein the oxygen product has a pressure of at least 200 psia.  
   
   
       8 . The process of  claim 1  wherein the oxygen-rich liquid is vaporized in the primary heat exchanger.  
   
   
       9 . The process of  claim 1  wherein the oxygen-rich liquid is vaporized in a product boiler separate from the primary heat exchanger.  
   
   
       10 . The process of  claim 1  further comprising recovering nitrogen-rich vapor as product nitrogen.