Method for the cryogenic separation of air, and air separation plant

Abstract

A method for the cryogenic separation of air, in which method an air separation plant with a rectification column arrangement is used, which plant has a pressure column, a low-pressure column, a raw argon column and pure argon column. In the method, evaporation gas from a head gas condensation device associated with the raw argon column is partially or completely fed into the low-pressure column in a first feed-in region, whereas evaporation gas from a head gas condensation device associated with the pure argon column and excess liquid from this head gas condensation device are partially or completely fed into the low-pressure column in a shared second feed-in region. In one embodiment, flash gas forming during the expansion of cooling fluid into the head gas condensation device associated with the raw argon column can be partially or completely fed into the low-pressure column in the second feed-in region.

1 . A method for the cryogenic separation of air, in which method an air separation unit with a rectification column arrangement is used, which plant has a pressure column, a low-pressure column, a raw argon column and a pure argon column, wherein
 using a first proportion of an oxygen-enriched liquid from the pressure column, a first liquid pressure flow is formed, which is expanded while a first flash gas is produced and a first low-pressure liquid remains,   using a second proportion of the oxygen-enriched liquid from the pressure column, a second liquid pressure flow is formed, which is expanded while a second flash gas is produced and a second low-pressure liquid remains,   the raw argon column is operated using a first head gas condensation arrangement in which head gas of the raw argon column is subjected to condensation with partial evaporation of a first cooling fluid provided using the first low-pressure liquid or a part thereof,   the pure argon column is operated using a second head gas condensation arrangement in which head gas of the pure argon column is subjected to condensation with partial evaporation of a second cooling fluid provided using the second low-pressure liquid or a part thereof,   a first evaporation gas formed during the partial evaporation of the first cooling fluid or a part thereof and a first excess liquid remaining after the partial evaporation of the first cooling fluid or a part thereof are fed into the low-pressure column, and   a second evaporation gas formed during the partial evaporation of the second cooling fluid or a part thereof and a second excess liquid remaining after the partial evaporation of the second cooling fluid or a part thereof are fed into the low-pressure column,   the first evaporation gas or the part thereof fed into the low-pressure column is partially or completely fed into the low-pressure column in a first feed-in region,   the second evaporation gas or the part thereof fed into the low-pressure column is partially or completely fed into the low-pressure column in a second feed-in region,   the second excess liquid or the part thereof fed into the low-pressure column is partially or completely fed into the low-pressure column in the second feed-in region, and   the first feed-in region is 5 to 25 theoretical plates below the second feed-in region and the first and second feed-in regions are each regions which do not comprise any separating devices.   
     
     
         2 . The method according to  claim 1 , in which
 the first flash gas is separated from the first low-pressure liquid in a first phase separation and   the second flash gas is separated from the second low-pressure liquid in a second phase separation, wherein   the first and second phase separations are carried out in separate first and second phase separators, and   in particular the second phase separator is formed by the evaporation chamber of the second head gas condensation arrangement.   
     
     
         3 . The method according to  claim 1 , in which the formation of the first flash gas and the first low-pressure liquid and the production of the second flash gas and the second low-pressure liquid are carried out in a common valve and in a common phase separation and a common phase separator, which is formed in particular by the evaporation chamber of the second head gas condensation arrangement. 
     
     
         4 . The method according to  claim 1 , in which the first flash gas or a part thereof is partially or completely, and separately from the first evaporation gas, fed into the low-pressure column in the second feed-in region, wherein in particular the first flash gas is transferred unthrottled into the low-pressure column after it has been provided in the first phase separation. 
     
     
         5 . The method according to  claim 1 , in which the first evaporation gas or a part thereof is fed together with the first excess liquid or a part thereof as a first two-phase flow into the low-pressure column in the first feed-in region. 
     
     
         6 . The method according to  claim 1 , in which the first low-pressure liquid or the part thereof which is forcibly fed through the one or more condenser evaporators is held in a reservoir which is geodetically arranged above one or more feed-in positions into the one or more condenser evaporators. 
     
     
         7 . The method according to  claim 5 , in which the first evaporation gas and the first excess liquid are discharged from the condenser evaporator as the first two-phase flow without returning the first excess liquid or a part thereof into the one or more condenser evaporators. 
     
     
         8 . The method according to  claim 4 , in which the first flash gas is transferred unthrottled to the low-pressure column after being provided in the phase separation. 
     
     
         9 . The method according to  claim 4 , wherein the second evaporation gas or the part thereof fed into the low-pressure column in the second feed-in region is combined with the second excess liquid or the part thereof fed into the low-pressure column in the second feed-in region to form a second two-phase flow which is fed into the low-pressure column in the second feed-in region. 
     
     
         10 . The method according to  claim 5 , in which the first two-phase flow is passed between the first head gas condensation arrangement and the low-pressure column through a throttle valve. 
     
     
         11 . The method according to  claim 6 , in which there is passing between the head gas condensation arrangement and the low-pressure column into a phase separator in which the first evaporation gas and the first excess liquid are separated from each other, wherein the evaporation gas is passed between the phase separator and the low-pressure column through a throttle valve. 
     
     
         12 . The method according to  claim 11 , in which the throttle valve is completely open at least temporarily during operation. 
     
     
         13 . The method according to  claim 11 , in which the liquid level in the phase separator is measured and the amount of first cooling fluid introduced into the first head gas condensation arrangement is adjusted as a function of the measured value. 
     
     
         14 . The method according to  claim 13 , in which the amount of liquid produced in the phase separator is quantitatively controlled. 
     
     
         15 . The method according to  claim 11 , in which the head gas condensation arrangement comprises a heat exchanger block and said heat exchanger block is arranged in the interior of the phase separator, in which the first evaporation gas and the first excess liquid are separated from each other. 
     
     
         16 . The method according to any of  claim 10 , in which the throttle valve is adjusted such that the temperature of the first cooling fluid is preferably at least 0.1 K above the triple point temperature of argon upon entering the first head gas condensation arrangement. 
     
     
         17 . An air separation plant with a rectification column arrangement having a pressure column, a low-pressure column, a raw argon column and a pure argon column, wherein the air separation plant is configured to,
 using a first proportion of an oxygen-enriched liquid from the pressure column, form a first liquid pressure flow and expanded said first liquid pressure flow while a first flash gas is produced and a first low-pressure liquid remains,   using a second proportion of the oxygen-enriched liquid from the pressure column, form a second liquid pressure flow and expand said second liquid pressure flow while a second flash gas is produced and a second low-pressure liquid remains,   operate the raw argon column using a first head gas condensation arrangement and subject this head gas of the raw argon column to condensation with partial evaporation of a first cooling fluid provided using the first low-pressure liquid or a part thereof,   operate the pure argon column using a second head gas condensation arrangement and subject this head gas of the pure argon column to condensation with partial evaporation of a second cooling fluid provided using the second low-pressure liquid or a part thereof,   feeding a first evaporation gas formed during the partial evaporation of the first cooling fluid or a part thereof and a first excess liquid remaining after the partial evaporation of the first cooling fluid or a part thereof into the low-pressure column, and   feeding a second evaporation gas formed during the partial evaporation of the second cooling fluid or a part thereof and a second excess liquid remaining after the partial evaporation of the second cooling fluid or a part thereof into the low-pressure column,   characterized by means which are configured:   to partially or completely feed the first evaporation gas or the part thereof fed into the low-pressure column into the low-pressure column in a first feed-in region,   to partially or completely feed the second evaporation gas or the part thereof fed into the low-pressure column into the low-pressure column in a second feed-in region, and   to partially or completely feed the second excess liquid or the part thereof fed into the low-pressure column into the low-pressure column in the second feed-in region,   wherein the first feed-in region is 5 to 25 theoretical plates below the second feed-in region and the first and second feed-in regions are each regions which do not comprise any separating devices.   
     
     
         18 . The air separation unit according to  claim 17 , comprising means which are configured to partially or completely, and separately from the first evaporation gas, feed the first flash gas or a part thereof into the low-pressure column in the second feed-in region.