Process and plant for low-temperature fractionation of air

Abstract

A SPECTRA process for low-temperature fractionation of air, in which bottoms liquid from an additional second rectification column used to obtain oxygen is evaporated in a second condenser-evaporator. In this second condenser-evaporator, gas that has been evaporated beforehand in a first condenser-evaporator, which is used for condensation of tops gas from a first rectification column, is condensed at the pressure level of the previous evaporation. The invention likewise provides a corresponding plant.

1 - 13 . (canceled) 
     
     
         14 . A process for the low-temperature fractionation of air, in which an air fractionation plant having a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator is used, wherein the process comprises that
 the first rectification column is fed with air and operated at a first pressure level, and the second rectification column is fed from the first rectification column and operated at a second pressure level below the first pressure level, wherein   tops gas of the first rectification column is obtained as a nitrogen product and discharged from the air fractionation plant, and bottoms liquid of the second rectification column is obtained as an oxygen product and discharged from the air fractionation plant,   a first and a second material stream below the first pressure level are subjected to evaporation in the first condenser evaporator, and further tops gas of the first rectification column is condensed in the first condenser evaporator and returned to the first rectification column as a return flow,   the first material stream is formed using liquid taken from the first rectification column with a first oxygen content, and the second material stream is formed using liquid taken from the first rectification column with a second oxygen content above the first oxygen content,   gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator is partially or completely subjected to recompression to the first pressure level and fed into the first rectification column, and gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to work-performing expansion and discharged from the air fractionation plant, and   bottoms liquid of the second rectification column is evaporated in the second condenser evaporator, and   gas of the first or second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator and fed at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or fed into a lower region of the first rectification column,   wherein   the gas of the first or second material stream, which is subjected to condensation in the second condenser evaporator after its evaporation or partial evaporation in the first condenser evaporator, is subjected to condensation in the second condenser evaporator at a pressure level at which it was previously subjected to evaporation or partial evaporation in the first condenser evaporator.   
     
     
         15 . The process according to  claim 14 , in which a first portion of the first material stream after its evaporation in the first condenser evaporator is subjected to recompression to the first pressure level, and in which a second portion of the first material stream after its evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator. 
     
     
         16 . The process according to  claim 14 , in which a first portion of the second material stream after its evaporation in the first condenser evaporator is subjected to work-performing expansion, and in which a second portion of the second material stream after its evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator. 
     
     
         17 . The process according to  claim 14 , in which one or more compressors is or are provided for the recompression of the gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator, and in which, for the expansion of the gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more expansion machines are provided which is or are coupled to the one or more compressors. 
     
     
         18 . The process according to  claim 14 , in which the gas of the first or second material stream, which after evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the first condenser evaporator, is transferred into the second condenser evaporator using a gas line that without a compressor couples the first condenser evaporator and the second condenser evaporator. 
     
     
         19 . The process according to  claim 14 , in which at least a portion of a condensate formed during condensation in the first condenser evaporator is by use of a pump subjected to an increase in pressure in the liquid state. 
     
     
         20 . The process according to  claim 19 , in which the pressure increase to the first pressure level is carried out in the liquid state. 
     
     
         21 . The process according to  claim 14 , in which the tops gas of the first rectification column has a content of in each case less than 1 ppb oxygen, carbon monoxide, and/or hydrogen and a content of less than 10 ppm argon on a volume basis. 
     
     
         22 . The process according to  claim 14 , in which the bottoms liquid of the second rectification column has a content of less than 10 ppb argon and/or 5 ppm methane on a volume basis. 
     
     
         23 . The process according to  claim 14 , in which the first pressure level is 7 to 14 bar absolute pressure and in which the second pressure level is 1.2 to 5 bar absolute pressure. 
     
     
         24 . The process according to  claim 14 , in which all of the cooled compressed air to be fractionated in the process is fed into the first rectification column in gaseous form. 
     
     
         25 . An air fractionation plant having a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator and configured
 to feed the first rectification column with air and to operate it at a first pressure level, and to feed the second rectification column from the first rectification column and to operate it at a second pressure level below the first pressure level,   to obtain tops gas of the first rectification column as a nitrogen product and discharge it from the air fractionation plant, and to obtain bottoms liquid of the second rectification column as an oxygen product and discharge it from the air fractionation plant,   to subject a first and a second material stream below the first pressure level to evaporation in the first condenser evaporator, and to condense further tops gas of the first rectification column in the first condenser evaporator and to return it to the first rectification column as a return flow,   to form the first material stream using liquid taken from the first rectification column with a first oxygen content, and to form the second material stream using liquid taken from the first rectification column with a second oxygen content above the first oxygen content,   to partially or completely subject gas of the first material stream, after its evaporation or partial evaporation in the first condenser evaporator, to recompression to the first pressure level and to feed it into the first rectification column, and to subject gas of the second material stream, after its evaporation or partial evaporation in the first condenser evaporator, to expansion and to discharge it from the air fractionation plant,   to evaporate bottoms liquid of the second rectification column in the second condenser evaporator, and   to subject gas of the first or second material stream, after its evaporation or partial evaporation in the first condenser evaporator, to condensation in the second condenser evaporator and to feed it at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or to feed it into a lower region of the first rectification column,   wherein for the recompression of the gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more compressors are provided, and for the expansion of the gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator, one or more expansion machines mechanically coupled to the one or more compressors are provided,   wherein   the first condenser evaporator and the second condenser evaporator are arranged in such a way that the gas of the first or second material stream, which is subjected to condensation in the second condenser evaporator, is subjected to condensation at a pressure level at which it was previously subjected to evaporation in the first condenser evaporator.   
     
     
         26 . Air fractionation plant according to  claim 25 , having means which are configured to carry out a process for the low-temperature fractionation of air, in which an air fractionation plant having a first rectification column, a second rectification column, a first condenser evaporator, and a second condenser evaporator is used, wherein the process comprises that
 the first rectification column is fed with air and operated at a first pressure level, and the second rectification column is fed from the first rectification column and operated at a second pressure level below the first pressure level, wherein   tops gas of the first rectification column is obtained as a nitrogen product and discharged from the air fractionation plant, and bottoms liquid of the second rectification column is obtained as an oxygen product and discharged from the air fractionation plant,   a first and a second material stream below the first pressure level are subjected to evaporation in the first condenser evaporator, and further tops gas of the first rectification column is condensed in the first condenser evaporator and returned to the first rectification column as a return flow,   the first material stream is formed using liquid taken from the first rectification column with a first oxygen content, and the second material stream is formed using liquid taken from the first rectification column with a second oxygen content above the first oxygen content,   gas of the first material stream after its evaporation or partial evaporation in the first condenser evaporator is partially or completely subjected to recompression to the first pressure level and fed into the first rectification column, and gas of the second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to work-performing expansion and discharged from the air fractionation plant, and   bottoms liquid of the second rectification column is evaporated in the second condenser evaporator, and   gas of the first or second material stream after its evaporation or partial evaporation in the first condenser evaporator is subjected to condensation in the second condenser evaporator and fed at least in part to the liquid taken from the first rectification column with the first or second oxygen content and used in the formation of the first or second material stream, or fed into a lower region of the first rectification column,   wherein   the gas of the first or second material stream, which is subjected to condensation in the second condenser evaporator after its evaporation or partial evaporation in the first condenser evaporator, is subjected to condensation in the second condenser evaporator at a pressure level at which it was previously subjected to evaporation or partial evaporation in the first condenser evaporator.