Method and Installation for Supplying Highly Pure Oxygen By Cryogenic Distillation of Air

Abstract

The invention relates a method for supplying highly pure oxygen by cryogenic distillation of air from an installation comprising a first (1) and a second (2) air separating apparatus. According to the invention: the first air separating apparatus has a medium pressure column, a low pressure column thermally connected to the medium pressure column, and has a mixing column in which air to be distilled is fed to the medium pressure column; liquids enriched with oxygen and with nitrogen are fed from the medium pressure column to the low pressure column; according to a first operation of the apparatus, a flow of oxygen-enriched liquid coming from the low pressure column is fed to the top of the mixing column; a flow of low-purity oxygen is drawn off from the top of the mixing column and at least a portion ( 3 ) thereof is fed to a first consumer unit ( 5 ), and; the second apparatus ( 2 ) supplies highly pure oxygen ( 8 ) to a second consumer unit ( 9 ), whereas according to a second operation, the flow of low-purity oxygen drawn off from the top of the mixing column is reduced in the first apparatus; a flow of highly pure oxygen is drawn off from the vessel of the low pressure column of the first apparatus and is fed ( 11 ) to at least the second consumer unit ( 9 ), and; the second apparatus ( 2 ) does not supply highly pure oxygen to the second consumer unit.

1 - 10 . (canceled)  
   
   
       11 . A method for supplying high-purity oxygen by cryogenic distillation of air from an installation comprising a first air separation unit ( 1 ) and a second air separation unit ( 2 ), the first air separation unit comprising a medium-pressure column, a low-pressure column ( 4 A) thermally coupled to the medium-pressure column, and a mixing column ( 6 A), in which method: 
 a) air to be distilled is sent to the medium-pressure column;    b) oxygen-enriched and nitrogen-enriched liquids are sent from the medium-pressure column to the low-pressure column;    c) in a first step of the air separation unit, an oxygen-enriched liquid stream from the low-pressure column is sent to the top of the mixing column;    d) in the first step, a low-purity oxygen stream is withdrawn from the top of the mixing column and at least one portion of this is sent to a first consuming unit ( 5 );    e) in the first step, air is sent to the mixing column;    f) in the first step, the second air separation unit supplies high-purity oxygen to a second consuming unit ( 9 ),    characterized in that:    g) in a second step, in the first air separation unit, the oxygen-enriched liquid stream sent to the top of the mixing column is reduced, possibly to zero, the stream of air sent to the mixing column is reduced, possibly to zero, and the stream of low-purity oxygen withdrawn from the top of the mixing column is reduced, possibly to zero; and    h) in the second step, a stream of high-purity oxygen is withdrawn from the bottom of the low-pressure column of the first air separation unit and sent to at least the second consuming unit.    
   
   
       12 . The method of  claim 11 , in which, in the second step, the second air separation unit ( 2 ) does not supply high-purity oxygen to the second consuming unit ( 9 ), or supplies part of the high-purity oxygen required by the second consuming unit.  
   
   
       13 . The method of  claim 11 , in which the first consuming unit ( 5 ) is a blast furnace and the second consuming unit ( 9 ) is a converter or an arc furnace.  
   
   
       14 . The method of  claim 13 , in which, during the first step, the blast furnace ( 5 ) is supplied with oxygen-enriched air and during the second step the blast furnace is fed either with air or with air less oxygen-enriched than that with which it is fed during the first step.  
   
   
       15 . The method of  claim 11 , in which the mixing column ( 6 A) does not operate during the second step.  
   
   
       16 . The method of  claim 11 , in which the second consuming unit ( 9 ) is fed with oxygen only from the second air separation unit ( 2 ) during the first step and is fed with oxygen only from the first air separation unit ( 1 ) during the second step.  
   
   
       17 . An installation for supplying oxygen by cryogenic distillation of air, comprising a first air separation unit ( 1 ) and a second air separation unit ( 2 ), the first air separation unit comprising a medium-pressure column ( 2 A), a low-pressure column ( 4 A) thermally coupled to the medium-pressure column, and a mixing column ( 6 A), which installation comprises: 
 a) means for sending air to be distilled to the medium-pressure column;    b) means for sending oxygen-enriched and nitrogen-enriched liquids from the medium-pressure column to the low-pressure column;    c) means for sending a stream of oxygen-enriched liquid from the low-pressure column to the top of the mixing column;    d) means for sending air to the bottom of the mixing column;    e) means for withdrawing a stream of low-purity oxygen from the top of the mixing column and means for sending at least one portion of this to a first consuming unit ( 5 ); and    f) means for sending high-purity oxygen from the second air separation unit to a second consuming unit ( 9 ),    characterized in that it includes:    g) means for reducing, possibly to zero, the stream of oxygen-enriched liquid sent to the top of the mixing column;    h) means for reducing, possibly to zero, the air sent to the bottom of the mixing column; and    i) means for withdrawing a stream of high-purity oxygen from the bottom of the low-pressure column of the first air separation unit and means for sending this stream to the second consuming unit.    
   
   
       18 . The installation of  claim 17 , in which the first consuming unit ( 5 ) is a blast furnace and the second consuming unit ( 9 ) is a converter or an arc furnace.  
   
   
       19 . The installation of  claim 18 , which includes means for feeding the blast furnace ( 5 ) with low-purity oxygen from the first air separation unit ( 1 ) and means for stopping the low-purity oxygen being sent from the first air separation unit to the blast furnace.  
   
   
       20 . The installation of  claim 16 , which includes at least one high-purity oxygen compressor ( 13 ) upstream of the second consuming unit ( 9 ) and downstream of the first air separation unit ( 1 ).