Ultra-high-purity oxygen production method and ultra-high-purity oxygen production apparatus

Abstract

An ultra-high-purity oxygen production method and apparatus are provide, in which the method can include a step in which feed oxygen comprising low-boiling-point components as impurities is introduced from a warm end of a main heat exchanger and cooled, then introduced into an oxygen rectification column, and product ultra-high-purity oxygen from which the low-boiling-point components have been removed is drawn as a gas or a liquid from a lower portion of the oxygen rectification column.

What is claimed is: 
     
         1 . An ultra-high-purity oxygen production method utilizing an air separation unit comprising a main heat exchanger, a nitrogen rectification column, a nitrogen condenser, an oxygen rectification column, and an oxygen vaporizer, wherein the method comprises the steps of:
 introducing a feed oxygen comprising low-boiling-point components as impurities to a warm end of the main heat exchanger, wherein the feed oxygen is cooled and at least partially liquefied, then introducing the feed oxygen into the oxygen rectification column, and ultra-high-purity oxygen from which the low-boiling-point components have been removed is withdrawn as a gas or a liquid from a lower portion of the oxygen rectification column or from the oxygen vaporizer;   utilizing a heating fluid as a heating medium in the oxygen vaporizer, wherein the heating fluid is selected from the group consisting of: a portion of feed air cooled in the main heat exchanger, a portion of the feed oxygen cooled in the main heat exchanger, a liquid or gas withdrawn from a medium-pressure rectification column constituting the nitrogen rectification column, and combinations thereof;   vaporizing liquefied oxygen supplied from a bottom portion of the oxygen rectification column; and   supplying a vapour stream thereof to the bottom portion of the oxygen rectification column.   
     
     
         2 . The ultra-high-purity oxygen production method according to  claim 1 , further comprising a step in which liquefied nitrogen or an oxygen-containing liquid supplied from the medium-pressure rectification column, or liquid nitrogen or liquefied air supplied from outside the air separation unit is utilized as a refrigerant in an oxygen condenser provided above or in a top portion of the oxygen rectification column, and a low-boiling-point component-containing oxygen stream supplied from the oxygen rectification column is liquefied and supplied to a top portion of the oxygen rectification column as a reflux liquid. 
     
     
         3 . The ultra-high-purity oxygen production method according to  claim 1 , further comprising a step in which a portion of the feed oxygen drawn from partway through the main heat exchanger is expanded by an expansion turbine and cooled, after which it is once again supplied to the main heat exchanger. 
     
     
         4 . An ultra-high-purity oxygen production apparatus comprising:
 a main heat exchanger configured to receive a feed air and a feed oxygen;   a first rectification column having a bottom portion into which the feed air, that has undergone heat exchange in the main heat exchanger, is introduced;   at least one nitrogen condenser for condensing a nitrogen-rich gas drawn from a column top of the first rectification column;   a second rectification column having a column top into which is introduced a nitrogen-rich gas condensed in the nitrogen condenser and/or a nitrogen-rich gas drawn from the column top of the first rectification column, after said nitrogen-rich gas has been cooled in a sub-cooler;   an oxygen rectification column having a column top or a purification portion into which the feed oxygen that has undergone heat exchange in the main heat exchanger is introduced;   an oxygen vaporizer which is arranged below a bottom portion of the oxygen rectification column and vaporizes liquefied oxygen while using, as a heating medium, one or more of: a portion of feed air cooled in the main heat exchanger, a portion of the feed oxygen cooled in the main heat exchanger, and a liquid or gas drawn from a medium-pressure rectification column constituting the nitrogen rectification column; and   a sub-cooler for performing heat exchange of: an oxygen-rich liquid drawn from the bottom portion of the first rectification column, a purified gas condensed in the nitrogen condenser and/or a purified gas drawn from the column top of the first rectification column, and a nitrogen-rich gas drawn from the column top of the second rectification column.   
     
     
         5 . The ultra-high-purity oxygen production apparatus according to  claim 4 , comprising an expansion turbine into which a gas drawn from a gas phase in the nitrogen condenser is introduced, after said gas has been passed through a part of the main heat exchanger. 
     
     
         6 . The ultra-high-purity oxygen production apparatus according to  claim 4 , comprising an oxygen condenser for condensing a low-boiling-point component-containing oxygen gas drawn from the column top of the oxygen rectification column. 
     
     
         7 . The ultra-high-purity oxygen production apparatus according to  claim 5 , comprising: a feed oxygen pipeline for introducing the feed oxygen, via the main heat exchanger, into the column top or a rectification portion of the oxygen rectification column;
 a branch feed oxygen pipeline which branches the feed oxygen from partway through the main heat exchanger in the feed oxygen pipeline, and merges into a pipeline before connection to the expansion turbine; and   an ultra-high-purity oxygen extraction pipeline for extracting ultra-high-purity oxygen from a vaporized liquid portion of the oxygen vaporizer.   
     
     
         8 . An ultra-high-purity oxygen production apparatus comprising:
 a main heat exchanger into which feed air and feed oxygen are introduced;
 a nitrogen rectification column having a bottom portion into which the feed air, that has undergone heat exchange in the main heat exchanger, is introduced; 
 a first nitrogen condenser for condensing a nitrogen-rich gas drawn from a column top of the nitrogen rectification column; 
 a second nitrogen condenser for condensing the nitrogen-rich gas drawn from the column top of the nitrogen rectification column; 
 an expansion turbine into which a gas drawn from a gas phase in the first nitrogen condenser is introduced, after said gas has been passed through a part of the main heat exchanger; 
 a compressor for compressing a gas drawn from a gas phase in the second nitrogen condenser; 
 an oxygen rectification column having a column top or a purification portion into which the feed oxygen that has undergone heat exchange in the main heat exchanger is introduced; and 
 an oxygen vaporizer which is arranged below the bottom portion of the oxygen rectification column and vaporizes liquefied oxygen while using, as a heating medium, one or more of: a portion of feed air cooled in the main heat exchanger, a portion of the feed oxygen cooled in the main heat exchanger, and a liquid or gas drawn from the nitrogen rectification column.