Cryogenic air separation main condenser system with enhanced boiling and condensing surfaces

Abstract

A cryogenic air separation system having a main condenser comprising a plurality of tubes having fluted external condensing surfaces upon which downflowing nitrogen vapor condenses, and having structured internal boiling surfaces upon which downflowing oxygen liquid vaporizes.

1 . A method for operating a cryogenic air separation plant having a higher pressure column, a lower pressure column, and a main condenser having a plurality of tubes wherein each of said tubes has a fluted external surface and a structured internal surface, said method comprising passing nitrogen vapor from the higher pressure column to the upper portion of the main condenser, flowing oxygen liquid from the separation section of the lower pressure column to the upper portion of the tubes of the main condenser, passing the nitrogen vapor down the main condenser in contact with the external surfaces of the tubes, passing the oxygen liquid down the tubes of the main condenser in heat exchange relation with the downflowing nitrogen vapor wherein at least some but not all of the downflowing oxygen liquid is vaporized, and withdrawing both oxygen vapor and oxygen liquid from the main condenser in a liquid to vapor mass flowrate ratio within the range of from 0.05 to 10.  
   
   
       2 . The method of  claim 1  wherein the liquid to vapor mass flowrate ratio is within the range of from 0.2 to 2.0.  
   
   
       3 . The method of  claim 1  wherein the main condenser is a shell-and-tube heat exchanger.  
   
   
       4 . The method of  claim 1  wherein the main condenser is a brazed aluminum heat exchanger.  
   
   
       5 . The method of  claim 1  wherein the main condenser comprises a plurality of condenser modules.  
   
   
       6 . A downflow condenser, particularly suitable as the main condenser of a double column cryogenic air separation plant, having a plurality of tubes wherein each of said tubes has a fluted external surface and a structured internal surface.  
   
   
       7 . The condenser of  claim 6  having from 300 to 800 tubes.  
   
   
       8 . The condenser of  claim 6  wherein the structured internal surface has cavities with a depth within the range of from 0.5 to 2.0 millimeters.  
   
   
       9 . The condenser of  claim 6  wherein the tubes have an internal diameter within the range of from 15 to 25 millimeters.