Cryogenic Neon Purification System and Method

Abstract

A feed gas including neon, nitrogen, and helium is cooled in a heat exchange system to a first temperature to produce a two-phase mixture that is introduced into a first phase separator and separated into a nitrogen-rich liquid and a first gaseous crude neon stream. The pressure is reduced in at least a portion of the nitrogen-rich liquid, which is vaporized in the heat exchange system to generate a portion of the refrigeration therein. The first gaseous crude neon stream is introduced into a first adsorber that removes impurities such as nitrogen. The gaseous crude neon stream is further cooled to a second temperature. A portion of the cooling duty may come from the heat exchange system and another portion may come from a cryocooler to produce a two-phase stream. The two-phase stream is separated in a second phase separator into a crude helium vapor stream and a crude neon liquid stream with the latter being introduced into a distillation column to produce a vent stream containing a helium impurity and a pure liquid neon product. The pure liquid neon product is vaporized in the heat exchange system to generate refrigeration and produce the pure gaseous neon product.

What is claimed is: 
     
         1 . A method of purifying a mixture comprising neon, nitrogen, and helium comprising the steps of:
 (a) cooling the feed gas comprising neon, nitrogen, and helium in a heat exchange system to the first temperature to produce a two-phase mixture;   (b) optionally reducing in pressure and then introducing the two-phase mixture into the first phase separator to be separated into a nitrogen-rich liquid and the first gaseous crude neon stream;   (c) reducing in pressure at least a portion of the nitrogen-rich liquid and vaporing it in the heat exchange system to generate a portion of the refrigeration for the process;   (d) introducing the first gaseous crude neon stream into the first adsorber that removes impurities such as nitrogen;   (e) further cooling the gaseous crude neon stream to the second temperature in such a manner that at least a portion of the cooling duty comes from the heat exchange system to produce a two-phase stream;   (f) separating the two-phase stream in a second phase separator into a crude helium vapor stream and a crude neon liquid stream;   (g) optionally reducing in pressure the crude neon liquid stream and then introducing it into a distillation column to produce a vent stream containing a helium impurity and a pure liquid neon product;   (h) optionally reducing in pressure of the pure liquid neon product and then vaporizing it in the heat exchange system to generate refrigeration and produce the pure gaseous neon product.   
     
     
         2 . The method of  claim 1  where an additional portion of the cooling duty in step (e) comes from another refrigeration device. 
     
     
         3 . The method of  claim 2  where the cryocooler cold head is placed inside of the second phase separator. 
     
     
         4 . The method of  claim 2  comprising multiple cryocoolers present in series and in parallel. 
     
     
         5 . The method of  claim 1  where a crude helium vapor stream of step (f) is purified in the second adsorber to remove neon. 
     
     
         6 . The method of  claim 1  where the nitrogen-rich liquid in step (c) is supplemented by an additional liquid nitrogen import. 
     
     
         7 . The method of  claim 1  where the feed gas is compressed before cooling. 
     
     
         8 . A system for purifying neon comprising:
 a feed stream line configured to receive a gas mixture, wherein the gas mixture comprises neon, nitrogen, and helium;   at first heat exchanger configured to cool and/or heat the streams of the system;   a first separator in fluid communication with the feed stream line, and wherein the separator is configured to separate the mixed gas mixture to a crude neon vapor stream and a nitrogen-rich liquid stream;   a first adsorber in fluid communication with the first separator, wherein the adsorber receives the crude neon vapor stream from the first separator;   a second separator in fluid communication with the first adsorber, wherein the second separator is configured to separate a stream from the first adsorber into a crude helium vapor stream and a crude neon liquid stream; and   a distillation column in fluid communication with the second separator, wherein the distillation column receives the crude neon liquid stream and is configured to purify the crude neon liquid stream to a pure neon liquid product.   
     
     
         9 . The system of  claim 8 , wherein the nitrogen-rich liquid stream is used to refrigerate the system. 
     
     
         10 . The system of  claim 8 , further comprising an imported liquid nitrogen stream. 
     
     
         11 . The system of  claim 8 , further comprising a second heat exchanger. 
     
     
         12 . The system of  claim 8 , wherein the second separator is associated with a cryocooler. 
     
     
         13 . The system of  claim 12 , wherein the cryocooler is placed inside the second separator. 
     
     
         14 . The system of  claim 12 , wherein the cryocooler is a Gifford-McMahon cryocooler. 
     
     
         15 . The system of  claim 8 , comprising a second adsorber in fluid communication with the second separator, wherein the second adsorber receives the crude helium vapor from the second separator. 
     
     
         16 . A method of purifying neon comprising the steps of:
 cooling a gas mixture comprising neon, nitrogen, and helium in a heat exchange system to a first temperature;   separating the mixture in a first separator into a nitrogen-rich liquid stream and a crude neon vapor stream;   purifying the crude neon vapor stream in a first adsorber;   cooling the crude neon stream to a second temperature;   separating the crude neon stream in a second separator into a crude helium vapor stream and a crude neon liquid stream; and   purifying the crude neon liquid stream in a distillation column to a purified neon product stream.   
     
     
         17 . The method of  claim 16  further comprising the steps of reducing the pressure of the nitrogen-rich liquid stream and vaporizing it in the heat exchange system to generate a portion of the refrigeration for the system. 
     
     
         18 . The method of  claim 16  further comprising the step of introducing an imported liquid nitrogen stream to the heat exchange system to generate a portion of the refrigeration for the system. 
     
     
         19 . The method of  claim 16 , wherein the first adsorber is configured to remove nitrogen. 
     
     
         20 . The method of  claim 16  further comprising the step of cooling the second two-phase stream with a cryocooler associated with the second separator. 
     
     
         21 . The method of  claim 20 , wherein the cryocooler is located within the second separator. 
     
     
         22 . The method of  claim 20 , wherein the cryocooler is a Gifford-McMahon cryocooler. 
     
     
         23 . The method of  claim 16  further comprising the step of purifying the crude helium vapor stream in a second adsorber. 
     
     
         24 . The method of  claim 23  further comprising the step of vaporizing the purified helium stream to create a purified helium product. 
     
     
         25 . The method of  claim 16  further comprising the step of decreasing the pressure of the crude neon liquid stream before entering the distillation column. 
     
     
         26 . The method of  claim 16 , wherein the distillation column separates nitrogen liquid from helium impurities. 
     
     
         27 . The method of  claim 26 , further comprising the step of venting the helium impurities. 
     
     
         28 . The method of  claim 16 , further comprising the step of heating the helium impurities in the heat exchange system. 
     
     
         29 . The method of  claim 16  further comprising the step of reducing the pressure of the purified neon product stream. 
     
     
         30 . The method of  claim 16  further comprising the step of warming the purified neon product stream. 
     
     
         31 . The method of  claim 16  further comprising the step of collecting the purified neon product stream.