High-purity oxygen production method, and air separation device for producing high-purity oxygen

Abstract

An air separation device comprises: a main heat exchanger; a nitrogen rectification column; a nitrogen condensers disposed in a top portion of the nitrogen rectification column; a high-purity oxygen rectification column; and an oxygen evaporator disposed in a bottom portion of the high-purity oxygen rectification column. An oxygen-containing fluid discharged from an intermediate stage of the nitrogen rectification column is rectified in the high-purity oxygen rectification column and is concentrated in the bottom portion of the high-purity oxygen rectification column.

What is claimed is: 
     
         1 . A method for producing high purity oxygen, comprising steps:
 introducing a feed air cooled by a main heat exchanger to a lower section of a first nitrogen rectification column;   introducing an oxygen-enriched liquid derived from a bottom portion of the first nitrogen rectification column into a rectification section of a second nitrogen rectification column;   separating the feed air into a nitrogen-enriched component and an oxygen-enriched component in the first nitrogen rectification column and the second nitrogen rectification column;   condensing a first vapor stream from the first nitrogen rectification column in a first nitrogen condenser;   condensing a second vapor stream from the second nitrogen rectification column in a second nitrogen condenser;   introducing an oxygen-containing fluid derived from the rectification section of the second nitrogen rectification column into a high-purity oxygen rectification column and producing high-purity product oxygen by using an oxygen evaporator; and   using gas removed from a bottom portion of the second nitrogen rectification column as a heat medium for the oxygen evaporator which evaporates liquefied oxygen, and returning the gas to the second nitrogen condenser.   
     
     
         2 . The method for producing high purity oxygen as claimed in  claim 1 , further comprising the steps of:
 compressing part of the feed air by a compressor;   cooling the compressed part of the feed air in a main heat exchanger;   expanding the feed air by a expansion turbine; and   introducing the feed air into the second nitrogen rectification column.   
     
     
         3 . The method for producing high purity oxygen as claimed in  claim 1 , further comprising expanding in a turbine a vapor formed by vaporizing liquid in the second condenser. 
     
     
         4 . The method for producing high purity oxygen as claimed in  claim 1 , further comprising pressuring nitrogen condensed in the second condenser in a pump and then sending the pressurised condensed nitrogen to the top of the first nitrogen rectification column. 
     
     
         5 . The method for producing high purity oxygen as claimed in  claim 1 , wherein the oxygen-containing fluid derived from the rectification section of the second nitrogen rectification column is introduced into the high-purity oxygen rectification column as the sole feed for the high-purity oxygen rectification column. 
     
     
         6 . An air separation apparatus for producing high purity oxygen, comprising:
 a main heat exchanger   a first nitrogen rectification column   a second nitrogen rectification column   a first nitrogen condenser   a second nitrogen condenser   a high purity oxygen rectification column   a n oxygen evaporator   a first conduit configured to introduce feed air cooled by a main heat exchanger to a lower section of a first nitrogen rectification column in order to separate the feed air into a nitrogen-enriched component and an oxygen-enriched component in the first nitrogen rectification column;   a second conduit configured to introduce oxygen-enriched liquid derived from the bottom of the first nitrogen rectification column into a rectification section of a second nitrogen rectification column in order to separate the oxygen enriched liquid into a nitrogen-enriched component and an oxygen-enriched component in the second nitrogen rectification column;   a third conduit configured send a nitrogen enriched vapor stream from the first nitrogen rectification column to the first nitrogen condenser;   a fourth conduit configured to send a nitrogen enriched vapor stream from the second nitrogen rectification column to the second nitrogen condenser;   a fifth conduit configured to send an oxygen-containing fluid derived from the rectification section of the second nitrogen rectification column into the high-purity oxygen rectification column and producing high-purity product oxygen at the bottom of the high purity oxygen rectification column; and   a sixth conduit configured to send gas removed from the bottom of the second nitrogen rectification column as a heat medium for the oxygen evaporator which evaporates liquefied oxygen, and returning the gas condensed in the oxygen evaporator to the second nitrogen condenser.