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Hints About Air Separation Units

asu cryogenics air separation distillation column oxygen production air separation unit cryogenic air separation steelmaking asu dynamics air separation unit dynamics

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#1 ciamba87


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Posted 27 December 2018 - 04:48 AM

Good morning, I spent this year trying to learn more about air separation units, an interesting field but very difficult to find something about. I did not need to deepen each detail but I would to know the more I could. There is a last aspect i couldn't find anything reliable about: dynamics of such a system. I don't need very depth information, I'm just looking for some hints about start and stop time and about the inertia to regulate it (for example, I found it could change from 80% to 105% at a variation speed of 0.25% per minute, is it correct?). The size of the plant is quite small, about 200 ton per day. Are there any method to keep a mimimal (or zero) production without switching off the plant? How much is it energetically cost?

Could you help me?


Thank you,



#2 Bodhisatya


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Posted 30 December 2018 - 09:47 AM



There are two variants of an ASU Start-Up:

(a) Hot Start-Up

(b) Cold Start-Up.


Each requires a different time to establish products.  Generally, it takes 19 hours for Gaseous Oxygen production to start in a hot startup and another 12 hours for Argon Production. In cold start up it takes roughly 8 hours to resume Oxygen production.


APCS (Advanced Process Control) enables Automatic Load Control (ALC) and Automatic Start-Up (AST) enables a change in the plant load at will.  Need to check about the loading /unloading rate you mentioned.


Plant can be designed for multiple cases from MAX GOX (Gaseous O2) to MAX LIN (Liquid N2) and MAX LOX (Liquid O2), accordingly one needs to play with the plant's cold balance.  For each case, the specific power of the plant can be evaluated.




#3 ciamba87


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Posted 01 January 2019 - 12:09 PM

Thank you, Bodhisatya.  Can you suggest to me some handbooks to learn more about these system?  Particularly I would find an enthalpic analysis of the whole system: is there any reference?  They suggest Barron Cryogenic System but before buying it (because our library lacks it) I would like to know if it's worth it.


Thank you again,


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