Krypton xenon recovery from pipeline oxygen

Abstract

A method and apparatus for producing a krypton-xenon-rich stream in which a pipeline oxygen stream is removed from an oxygen pipeline at ambient temperature and then distilled in a cryogenic rectification plant to produce the krypton-xenon-rich stream from a column bottoms of a distillation column. The plant can generate its own refrigeration by way of a heat pump loop incorporating an expander or, alternatively, refrigeration can be added by means of a liquid oxygen reflux stream introduced into the top of such distillation column.

1 . A method of producing a krypton-xenon-rich stream comprising:
 removing a pipeline oxygen stream, containing oxygen vapor, from an oxygen pipeline at ambient temperature;   cooling the pipeline oxygen stream to a temperature at or near a dew point temperature of the oxygen vapor contained in the pipeline oxygen stream within a main heat exchanger of a cryogenic rectification plant and dividing the pipeline oxygen stream into a first oxygen vapor stream and a second oxygen vapor stream;   expanding the first oxygen vapor stream and rectifying the first oxygen vapor stream in a distillation column of the cryogenic rectification plant to produce a krypton-xenon-rich liquid column bottoms and an oxygen-rich vapor column overhead;   condensing the second oxygen vapor stream in a reboiler operatively associated with the distillation column to produce boil-up for the distillation column;   expanding and then re-vaporizing the second oxygen vapor stream, after having been condensed, in a condenser through indirect heat exchange a first oxygen-rich vapor stream, composed of the oxygen-rich vapor column overhead, thereby condensing the first oxygen-rich vapor stream to form a reflux stream;   fully warming the second oxygen vapor stream and a second oxygen-rich vapor stream composed of the oxygen-rich vapor column overhead, within the main heat exchanger, compressing the second oxygen vapor stream and recycling the second oxygen vapor stream, at least in part, back into the oxygen pipeline and recycling the second oxygen-rich vapor stream back into the oxygen pipeline after having been fully warmed;   passing at least part of the reflux stream into the distillation column as part of the reflux;   passing an oxygen liquid stream into the distillation column as another part of the reflux to introduce the refrigeration into the cryogenic rectification plant; and   discharging the krypton-xenon-rich stream from the distillation column, the krypton-xenon-rich stream composed of the krypton-xenon-rich liquid column bottoms.   
     
     
         2 . The method of  claim 1 , wherein:
 the reflux stream is passed in indirect heat exchange with the oxygen liquid stream within a subcooler, thereby to subcool the reflux stream;   the oxygen liquid stream after having passed through the subcooler is expanded and introduced into the distillation column;   a first part of the reflux stream after having been subcooled is passed into the distillation column as the part of the reflux therefor; and   a second part of the reflux stream, after having been subcooled, is discharged from the cryogenic rectification process.   
     
     
         3 . An apparatus for producing a krypton-xenon-rich stream comprising:
 a cryogenic rectification plant connected to an oxygen pipeline and configured to rectify a pipeline oxygen stream removed from an oxygen pipeline at ambient temperature and to produce the krypton-xenon-rich stream;   said cryogenic rectification plant comprising:   a main heat exchanger connected to the oxygen pipeline so as to receive the pipeline oxygen stream, the main heat exchanger configured to cool the pipeline oxygen stream to a temperature at or near a dew point temperature of oxygen vapor contained in the pipeline oxygen stream;   a distillation column connected to the main heat exchanger so as to receive a first oxygen vapor stream composed of part of the pipeline oxygen stream, the distillation column configured to rectify the first oxygen vapor stream to produce a krypton-xenon-rich liquid column bottoms and an oxygen-rich vapor column overhead and having an outlet to discharge the krypton-xenon-rich stream from the distillation column such that the krypton-xenon-rich stream is composed of the krypton-xenon-rich liquid column bottoms and an inlet positioned to receive an oxygen liquid stream as part of the reflux, thereby to impart refrigeration into the cryogenic rectification plant;   a reboiler operatively associated with the distillation column to produce boil-up for the distillation column, the reboiler connected to the main heat exchanger so that a second oxygen vapor stream composed of another part of the pipeline oxygen stream is introduced into the reboiler and condensed;   a condenser connected to the distillation column and the reboiler so that a first oxygen-rich vapor stream, composed of the oxygen-rich vapor column overhead, is condensed through indirect heat exchange with the second oxygen vapor stream, thereby to form a reflux stream returned at least part to the distillation column as reflux and to re-vaporize the second oxygen vapor stream;   expansion valves positioned between the main heat exchanger and the distillation column so that the first oxygen vapor stream is expanded prior to being introduced into the distillation column and between the reboiler and the condenser so that the second oxygen vapor stream after having been condensed is expanded;   the main heat exchanger connected to: the condenser so that the second oxygen vapor stream after having been re-vaporized is fully warmed within the main heat exchanger; the distillation column so that a second oxygen-rich vapor stream, composed of the oxygen-rich vapor column overhead, is passed in indirect heat exchange with the pipeline oxygen stream from the oxygen pipeline to assist in the cooling of the pipeline oxygen stream; and the oxygen pipeline so that the second oxygen-rich vapor stream is recycled back to the oxygen pipeline; and   a compressor connected between the main heat exchanger and the oxygen pipeline so that the second oxygen vapor stream after having been fully warmed is compressed back to pipeline pressure and at least in part is recycled back into the oxygen pipeline.   
     
     
         4 . The method of  claim 3 , wherein;
 a subcooler is connected to a condenser and is configured to receive the reflux stream and the oxygen liquid stream so that the reflux stream is subcooled within the subcooler;   the subcooler is connected to the distillation column so that the oxygen liquid stream is introduced into the distillation column after having passed through the subcooler, a first part of the reflux stream is introduced into the distillation column and a second part of the reflux stream is discharged from the cryogenic rectification plant; and   a further expansion valve is positioned between the subcooler and the distillation column so that the oxygen liquid stream is valve expanded before introduction into the distillation column.