Method and device for low-temperature air separation

Abstract

A method and device for low-temperature separation of air in a distillation column system having a high-pressure column and a low-pressure column. The system includes a precolumn to which the first part of feed air is introduced and from which gaseous nitrogen product is removed and then heated in a heat exchanger. The precolumn includes a head condenser to which a liquefied portion of a second part of the cooled feed air is introduced. A gaseous fraction from the upper region of the precolumn is introduced to the system condenser and fluid formed in the system condenser is at least partially fed to the precolumn as return flow.

1 . A method for low-temperature separation of air in a distillation column system which comprises a high-pressure column and a low-pressure column, and where
 feed air is compressed in a main compressor,   the compressed feed air is purified in a purification device,   the purified feed air is cooled in a main heat exchanger,   a first part stream of the cooled feed air is introduced into the distillation column system in a gaseous state,   a second part stream of the cooled feed air is introduced into the liquefying chamber of a secondary condenser which is realized as a condenser-evaporator with a condensation chamber and an evaporation chamber,   a liquid oxygen fraction from the low-pressure column is introduced into the evaporation chamber of the secondary condenser,   an oxygen product fraction is removed from the evaporation chamber of the secondary condenser in a gaseous state, is heated in the main heat exchanger and is finally obtained as a gaseous oxygen product and where   a first gaseous nitrogen product fraction is removed from the distillation column system, is heated in the main heat exchanger and is obtained as a first gaseous nitrogen product,   
       characterized in that
 the distillation column system also comprises a precolumn, the operating pressure of which is higher than the operating pressure of the high-pressure column, 
 the first part stream of the cooled feed air is introduced into the precolumn, 
 the first gaseous nitrogen product fraction is removed from the precolumn, 
 the precolumn comprises a head condenser which is realized as a condenser-evaporator with a condensation chamber and an evaporation chamber, 
 a liquefied portion of the second part stream is removed from the liquefaction chamber of the secondary condenser and is introduced into the evaporation chamber of the head condenser, 
 the secondary condenser, the head condenser and the precolumn are arranged one above another, 
 a gaseous fraction from the upper region of the precolumn is introduced into the condensation chamber of the head condenser and in that 
 liquid formed in the condensation chamber is fed to the precolumn at least in part as reflux. 
 
     
     
         2 . The method as claimed in  claim 1 , characterized in that the secondary condenser is arranged above the precolumn. 
     
     
         3 . The method as claimed in  claim 1 , characterized in that the secondary condenser and the head condenser are arranged in a common container. 
     
     
         4 . The method as claimed in  claim 1 , characterized in that the secondary condenser is arranged below the precolumn. 
     
     
         5 . The method as claimed in  claim 1 , characterized in that a second gaseous nitrogen product fraction is removed from the high-pressure column, heated in the main heat exchanger and obtained as a second gaseous nitrogen product. 
     
     
         6 . The method as claimed in  claim 1 , characterized in that a third part stream of the cooled feed air is expanded so as to carry out work and is introduced into the high-pressure column. 
     
     
         7 . The method as claimed in  claim 1 , characterized in that a first raw oxygen stream is removed in a liquid state from the sump of the high-pressure column and is introduced into the low-pressure column at a first intermediate point and in that a second liquid raw oxygen stream from the precolumn is introduced into the low-pressure column at a second intermediate point which is arranged higher than the first intermediate point. 
     
     
         8 . A device for the low-temperature separation of air
 comprising a distillation column system, a high-pressure column and a low-pressure column,   wherein the distillation column system also comprises a precolumn, the operating pressure of which when the device is operating is higher than the operating pressure of the high-pressure column,   having a main air compressor for compressing feed air,   having a purification device for purifying the compressed feed air,   having a main heat exchanger for cooling the purified feed air,   having means for introducing a first part stream of the cooled feed air into the precolumn,   wherein the precolumn comprises a head condenser which is realized as a condenser-evaporator with a condensation chamber and an evaporation chamber,   having means for removing a first gaseous nitrogen fraction from the precolumn,   having means for heating the first gaseous nitrogen fraction in the main heat exchanger and for subsequently removing it as a first gaseous nitrogen product,   having means for introducing a gaseous fraction from the upper region of the precolumn into the condensation chamber of the head condenser;   having means for feeding liquid that is formed in the condensation chamber into the precolumn as reflux,   having means for removing a first gaseous nitrogen product fraction from the precolumn,   having a secondary condenser which is realized as a condenser-evaporator with a condensation chamber and an evaporation chamber, wherein the secondary condenser, the head condenser and the precolumn are arranged one above another,   having means for introducing a second part stream of the cooled feed air into the liquefaction chamber of the secondary condenser,   having means for introducing a liquefied portion of the second part stream from the liquefaction chamber of the secondary condenser into the evaporation chamber of the head condenser,   having means for introducing a liquid oxygen fraction from the low-pressure column into the evaporation chamber of the secondary condenser and   having means for heating a gaseous oxygen product fraction from the evaporation chamber of the secondary condenser in the main heat exchanger and for subsequently removing it as a gaseous oxygen product.   
     
     
         9 . The device as claimed in  claim 8 , characterized in that the secondary condenser is arranged above the precolumn. 
     
     
         10 . The device as claimed in  claim 8 , characterized in that the secondary condenser and the head condenser are arranged in a common container. 
     
     
         11 . The device as claimed in  claim 8 , characterized by
 means for removing a second gaseous nitrogen fraction from the high-pressure column and by   means for heating the second gaseous nitrogen fraction in the main heat exchanger and for subsequently removing it as a second gaseous nitrogen product.   
     
     
         12 . The device as claimed in  claim 8 , characterized by
 an expanding machine for expanding a third part stream of the cooled feed air so as to carry out work and by   means for introducing the third part stream, which has been expanded so as to carry out work, into the high-pressure column.   
     
     
         13 . The device as claimed in  claim 8 , characterized in that a first raw oxygen line for removing a first liquid raw oxygen stream from the sump of the high-pressure column and for introducing the first raw oxygen stream at a first intermediate point into the low-pressure column and by a second raw oxygen line for removing a second liquid raw oxygen stream from the precolumn and for introducing the second raw oxygen stream into the low-pressure column at a second intermediate point which is arranged higher than the first intermediate point.