Cryogenic air separation unit with argon condenser vapor recycle
AssigneePraxair Technology, Inc.
InventorsZhengrong Xu, Neil M. Prosser
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Abstract
A system and method for improving the performance of an oxygen, nitrogen, and argon producing air separation unit configured to produce a gaseous nitrogen product stream is provided. By recycling the argon condenser boil-off vapor stream to the main air compression train, the argon recovery and oxygen recovery while maintaining the production level of a medium or high pressure gaseous nitrogen product stream. In addition, some operational cost savings in terms of lower power costs can also be realized compared to some prior art oxygen, nitrogen, and argon producing air separation units.
Claims14
An oxygen, argon and nitrogen producing air separation unit configured to receive an incoming feed air stream and produce one or more oxygen product streams one or more nitrogen product streams, and an argon stream, the air separation unit having a main air compression and purification system, a main heat exchanger, and a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer arrangement via a main condenser-reboiler, an argon column configured for receiving an argon-oxygen containing stream from the lower pressure column, and an argon condensing arrangement configured for condensing an argon-rich vapor stream from the argon column against an oxygen containing condensing medium, the air separation unit characterized by:
- a first portion of a boil-off vapor stream exiting the argon condenser is configured to be returned to the lower pressure column;
- and
- a second portion of the boil-off vapor stream exiting the argon condenser is configured to be recycled and mixed with the incoming feed air stream.
A method for increasing the argon recovery in an oxygen, nitrogen, and argon producing air separation unit, the air separation unit configured to receive an incoming feed air stream and produce an oxygen product stream, a nitrogen product stream, and an argon stream, the air separation unit having a main air compression circuit, a main heat exchanger, and a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer arrangement via a main condenser-reboiler, an argon column configured for receiving an argon-oxygen containing stream from the lower pressure column and an argon condensing arrangement configured for condensing an argon-rich vapor stream from the argon column against an oxygen containing condensing medium, the method comprising the steps of:
- (a) directing a first portion of a boil-off vapor stream exiting an argon condensing arrangement to the lower pressure column of the distillation column system;
- (b) recycling a second portion of the boil-off vapor stream exiting the argon condensing arrangement to the main air compression circuit;
- (c) mixing or blending the second portion of the boil-off vapor stream exiting the argon condensing arrangement with the incoming feed air stream;
- wherein the recycled second portion of the boil-off vapor stream exiting the argon condensing arrangement is preferably between about 5.0% and about 12.0% of the flow of the incoming feed air stream.
Dependencies are inferred from the claim text.