Air separation unit

Abstract

An air separation unit including: a main heat exchanger, a medium-pressure rectification column, a low-pressure rectification column, a crude argon column, a nitrogen condenser, a crude argon condenser, an oxygen turbine, a nitrogen compressor, and a nitrogen turbine. The nitrogen turbine expands nitrogen gas supplied from the nitrogen compressor. The air separation unit includes an inlet temperature of the oxygen turbine is lower than an inlet temperature of the nitrogen turbine.

1 : An air separation unit comprising:
 a main heat exchanger comprising feed air introduced from a warm end thereof and drawn from a cold end thereof;   a medium-pressure rectification column into configured to introduce the feed air drawn from the main heat exchanger;   a nitrogen condenser into configured to introduce a vapour stream from the medium-pressure rectification column, the vapour stream being condensed and drawn out as a reflux liquid;   a low-pressure rectification column into configured to introduce an oxygen-rich liquid drawn from the medium-pressure rectification column;   an oxygen turbine for expanding and cooling an oxygen-rich gas drawn from the nitrogen condenser, after the oxygen-rich gas has undergone heat exchange in the main heat exchanger; and   a nitrogen turbine for expanding nitrogen gas drawn from the low-pressure rectification column, after said nitrogen gas has undergone heat exchange at least in the main heat exchanger, been compressed to a predetermined pressure and cooled, and once again cooled in the main heat exchanger,   wherein, an inlet temperature of the oxygen turbine is lower than an inlet temperature of the nitrogen turbine.   
     
     
         2 : The air separation unit according to  claim 1 , further comprising
 a crude argon column into configured to introduce an oxygen-containing fluid drawn from the low-pressure rectification column; and   a crude argon condenser into configured to introduce a vapour stream from the crude argon column, the vapour stream being condensed and drawn out as a reflux liquid.   
     
     
         3 : The air separation unit according to  claim 1 , further comprising:
 a nitrogen gas pipeline configured to draw nitrogen gas from the low-pressure rectification column and extracts nitrogen gas at least via the main heat exchanger;   a nitrogen gas branch pipeline configured to branch the nitrogen gas pipeline downstream from the main heat exchanger, configured to introduce the nitrogen gas from the warm end of the main heat exchanger, configured to draw out out nitrogen gas from an intermediate portion, the nitrogen gas then being expanded by the nitrogen turbine and merged into the nitrogen gas pipeline or extracted as nitrogen gas once again via the main heat exchanger;   a bypass line configured to branch from the nitrogen gas branch pipeline, configured to bypasds the main heat exchanger so that nitrogen gas is not introduced therein, and configured to merge with the nitrogen gas branch pipeline; and   a regulating valve for regulating an amount of nitrogen gas circulating through the bypass line.   
     
     
         4 : The air separation unit according to  claim 1 , comprising:
 a nitrogen gas pipeline configured to draw nitrogen gas from the low-pressure rectification column and configured to extract nitrogen gas at least via the main heat exchanger;   a nitrogen gas branch pipeline configured to branch from the nitrogen gas pipeline downstream from the main heat exchanger, configured to introduce the nitrogen gas from the warm end of the main heat exchanger, configured to draw out nitrogen gas from an intermediate portion, the nitrogen gas then being expanded by the nitrogen turbine and merged into the nitrogen gas pipeline or extracted as nitrogen gas once again via the main heat exchanger;   a nitrogen booster which is provided in the nitrogen gas branch pipeline and configured to boost the pressure of the nitrogen gas to a predetermined pressure; and   a second cooling unit configured to cool the nitrogen gas pressure-boosted by the nitrogen booster.   
     
     
         5 : The air separation unit according to  claim 3 , further comprising a recycling nitrogen line configured to branch from the nitrogen gas branch pipeline inside the main heat exchanger, configured to draw nitrogen gas out from the cold end of the main heat exchanger, and configured to introduce nitrogen gas into the medium-pressure rectification column. 
     
     
         6 : The air separation unit according to  claim 3 , further comprising: a second nitrogen booster which is provided in the nitrogen gas branch pipeline and configured to boost the pressure of the nitrogen gas to a predetermined pressure; and
 a second cooling unit which is provided in the nitrogen gas branch pipeline and configured to cool the nitrogen gas pressure-boosted by the second nitrogen booster.   
     
     
         7 : The air separation unit according to  claim 1 , further comprising a sub-cooler which is configured to accept an oxygen-rich liquid drawn from the medium-pressure rectification column introduced from a warm end and drawn from a cold end.