Purification of inert gases to remove trace impurities

Abstract

A method for purifying an argon stream is provided. The method includes pretreating an argon waste stream to remove impurities to provide a pre-treated argon waste stream having argon, nitrogen, and hydrogen; cooling the argon waste stream to create a cold feed stream; and condensing the cold feed stream to create a liquid feed stream. The liquid feed stream is fed to the cryogenic distillation column to create a bottoms argon product stream and a gas waste stream. The bottoms argon product stream travels to an expansion device to provide a cooled bottoms argon product stream, which can optionally be combined with an argon lift stream downstream of the expansion device. The combined argon lift stream and cooled bottoms argon product stream are fed to the overhead condenser and vaporized to create a purified vapor phase argon stream.

What is claimed is: 
     
         1 . A method for purifying an argon stream comprising argon, nitrogen, hydrogen, carbon monoxide, carbon dioxide, water, and methane, the method comprising the steps of:
 cooling an argon waste stream with a cryogenic heat exchanger to create a cold feed stream;   condensing the cold feed stream in a reboiler to create a liquid feed stream, wherein the cold feed stream is in a heat exchange relationship with bottoms liquid of a cryogenic distillation column, said distillation column comprising packing, the reboiler disposed in a lower portion of the cryogenic distillation column, and an overhead condenser in an upper portion of the cryogenic distillation column;   withdrawing the liquid feed stream from the reboiler and introducing the liquid feed stream to the cryogenic distillation column;   separating components of the liquid feed stream in the cryogenic distillation column into a bottoms argon product stream and a gas waste stream, the bottoms argon product stream having an increased purity of argon as compared to the cold feed stream;   withdrawing the bottoms argon product stream from the cryogenic distillation column and expanding the bottoms argon product stream using an expansion device to provide a cooled bottoms argon product stream;   feeding the cooled bottoms argon product stream to the overhead condenser and vaporizing the cooled bottoms argon product stream in the overhead condenser to create a purified vapor phase argon stream;   feeding the purified vapor phase argon stream to the cryogenic heat exchanger, wherein the purified vapor phase argon stream is used to cool the pre-treated argon waste stream, thereby producing a warm product stream; and   removing the gas waste stream from the cryogenic distillation column.   
     
     
         2 . The method as claimed in  claim 1 , further comprising the step of feeding the gas waste stream to the cryogenic heat exchanger, wherein the gas waste stream is used to cool the pre-treated argon waste stream. 
     
     
         3 . The method as claimed in  claim 1 , further comprising the step of pretreating the argon waste stream to remove impurities to provide a pre-treated argon waste stream having argon, nitrogen, hydrogen prior to the cooling step, wherein the impurities removed are selected from the group consisting of oxygen, carbon monoxide, carbon dioxide, water, methane, and combinations thereof. 
     
     
         4 . The method as claimed in  claim 1 , further comprising the step of combining the cooled bottoms argon product stream and an argon lift stream downstream of the expansion device to provide lift to the cooled bottoms argon product stream. 
     
     
         5 . The method as claimed in  claim 1 , wherein the step of withdrawing the bottoms argon product stream from the cryogenic distillation column further comprises pumping the bottoms argon product stream from the bottom of the cryogenic distillation column to the overhead condenser. 
     
     
         6 . The method as claimed in  claim 1 , further comprising the step of feeding the bottoms argon product stream to separation stages in the cryogenic distillation column positioned above the overhead condenser. 
     
     
         7 . The method as claimed in  claim 1 , further comprising the steps of:
 separating a portion of the warm product stream downstream of the cryogenic heat exchanger to create a recycle stream;   compressing the recycle stream;   cooling a compressed recycle stream in the cryogenic heat exchanger to produce a cooled recycle stream; and   feeding the cooled recycle stream to the cryogenic distillation column such that the recovery of the warm product stream is increased as compared to when the cooled recycle stream is not fed to the cryogen distillation column.   
     
     
         8 . The method as claimed in  claim 1 , further comprising the steps of:
 sending the bottoms argon product stream to a sorbent bed system;   removing trace impurities in the bottoms argon product stream using the sorbent bed system to produce a sorbent bed outlet stream;   feeding the sorbent bed outlet stream to the overhead condenser.   
     
     
         9 . The method as claimed in  claim 8 , wherein the sorbent bed system comprises regenerable adsorbents. 
     
     
         10 . The method as claimed in  claim 8 , wherein the sorbent bed system comprises getter material. 
     
     
         11 . The method as claimed in  claim 1 , wherein the method does not include the step of compressing the warm product stream for refrigeration purposes.