3 replies to this topic

[srihari]

I have done a depressurization calculation by HYSYS for LPG condensate system but results showing negative temperature and pressure.

 

 

How to avoid negative temperatures in results 

 

After depressurization, system to reach a pressure of 0.5 barg and temperature 47.8C

 

Please find the attached required data and simulation file 

Can any one check the attached file HYSYS file??

 

http://www.4shared.c...ehydration.html

 

Thanks in advance

Attached Files

•  Condensate dehydration depressurization.docx   53.87KB   98 downloads

[ColinR33]

I can't read your html link (work firewall probably) but negative temperatures during depressuring are quite common as a result of the Joule Thompson effect, the system being depressured can get down to -40 or lower, sometimes to the level of requiring special metallurgy.  This depends on fluid inventory, initial conditions and mass of metal involved, someties the fluid will get very cold, but the mass of metal is large enough that the metal itself cannot physcially get that cold. It can  be even worse downstream of the blowdown valve where it is just piping.  There have been incidents involving cold embrittement fractures causing explosions in relief headers.  It is a little unusual that you would see them in a fire case unless you are referring to the temperature after the blowdown valve. Not much you can do about it, I and others have used special heaters to heat up the relief stream.

 

Cheers,

Colin

[PaoloPemi]

srihari,

you have openend another thread for this question...

[aqassam]

Disclaimer:I work at AspenTech.

 

I wanted to mention that for cold-temperature systems you should use a more rigorous technology than HYSYS DPU. 

 

We released BLOWDOWN Technology in Aspen HYSYS in May 2016 (v9). We have an upcoming webinar that will show exactly how to use this tool (it is more rigorous, and more complex than DPU). 

 

Update: You can now view the recording for the webinar:

 

http://www.aspentech...wn-oct/?src=cer

Edited by aqassam, 03 November 2016 - 11:20 AM.