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Specifications Of A Cryogenic Distillation Column

cryogenic distillation air separation unit aspen hysys distillation column example distillation column

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#1 ronb_2008

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Posted 19 April 2014 - 10:23 PM

Hey everyone, I got a question about cryogenic distillation. I need to have an air separation unit for my senior project, and I'm not quite sure how to size it. I created it in HYSYS, and it's given me some specifications about it. I have 25 stages, it operates at 1310 kPa and -165 C for the condenser and -149 C for the reboiler. HYSYS is giving me a sieve tray configuration, a diameter of 1.5 m, a tray/packed space of .55 m, and a tray/packed volume of .97 m^3. Oh and my air flow rate in is 7,055,000 kg/hr. 

 

What I'm wondering is if these specifications seem correct to anyone who has worked with these before. Some of spec values I can change, which makes me feel like the program didn't calculate it out, it is just a default. Any feedback would be great, or if anyone can tell me the specifications of an existing cryogenic distillation column that I could use as a reference I'd appreciate it. 



#2 Bobby Strain

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Posted 19 April 2014 - 11:12 PM

Your diameter is not remotely related to the air flow you report.

 

Bobby



#3 ronb_2008

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Posted 19 April 2014 - 11:59 PM

I didn't think it was. Do you have a more reasonable number in mind?



#4 Bodhisatya

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Posted 20 April 2014 - 12:31 AM

(a) What sort of Air Separation Unit is it?Does this unit produces Argon ,Nitrogen and Oxygen or only Nitrogen?

(B) What is the Produce Spec of the Products?25 stages that u r referring to are part of HP Column or LP column?The number of stages seems to be quite low if you desire a product spec of 99.99 % purity.

© Have your Reboiler and Condenser duties matched?

 

" Some of spec values I can change, which makes me feel like the program didn't calculate it out, it is just a default."...

Please elaborate the above statement?

 

Cheers

 

Bodhisatya.



#5 ronb_2008

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Posted 20 April 2014 - 12:41 PM

Sorry, I guess I could have been a little more specific. The column separates out nitrogen and oxygen, and the oxygen is what I need for my process. It only needs to be 97.5% pure. The pressure of my column is 1310 kPa, so that would be a HP column right? I'm unsure what you meant about my condenser and reboiler duties matching, but I have 5.898x10^5 kW for my condenser and 6.403x10^5 kW for my reboiler. 

 

 

And what I meant about the spec values that I can change, in HYSYS these values are blue, meaning I can change them to whatever I want. The black values are ones that are calculated out. So I was just wondering if the blue defaulted values seemed reasonable compared to what I am producing, which they are obviously not. I attached a picture of what I'm talking about. 

 

 

I'm basically looking to get an appropriate size for this. It doesn't have to be exact, I just need it for my senior design project. I'm working on converting coal and biomass to transportation fuels (diesel), and the air separation unit is where I get my oxygen for the gasification reaction. Again, any help is much appreciated. 

 

 

Attached Files



#6 Bodhisatya

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Posted 20 April 2014 - 11:51 PM

Requesting you to upload the HYSYS file in XML format uploaded in ZIP folder.More thoughts can be shared ,only after I go through the case file.

The calculated Reboiler and Condenser duties are different,so the simulation needs to be checked.

Also are you using Peng-Robinson Equation of State.

Bodhisatya

#7 ronb_2008

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Posted 21 April 2014 - 12:49 AM

Here's my file. Please don't be too harsh, like I said I'm only a student haha. I am actually using 2 different equations of state in the process, but Peng-Robinson for the Air Separation Unit at the beginning. Thanks again for your help. 

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#8 Bodhisatya

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Posted 23 April 2014 - 09:21 AM

I have gone through your file and am afraid to say that this is not the way of Simulating a Cryogenic Air Separation Unit.

 

Please let me know if you want a detailed Simulation of this Air Separation Unit,if yes then furnish  complete product spec (Required N2 and O2 flow,pressure and purity)

 

As per as Column dia is concerned it is strictly a function of Air Flow,to cross verify your dia obtained please refer to any standard Mass transfer book for detailed calculation.

 

Bodhisatya. 



#9 ronb_2008

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Posted 26 April 2014 - 01:59 PM

No that's ok, I had to turn in the project yesterday and didn't really have time to work on the HYSYS anymore after Tuesday, as there were other sections of the project that needed to be completed. Me and the classmate I was working with just kept the design and estimated some parameters the best we could using literature data. 

 

I really do appreciate you looking at my file and offering to help though. If I would have found this website sooner I know your input would have been extremely helpful for the project. Unfortunately the environmental, economic and safety sections of the project took quite a bit of time so after Tuesday that's all we were working on. Again, thank you for offering to help out. 






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