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Glycol Dehydration 2500psig


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#1 Miguel

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Posted 09 October 2008 - 11:02 AM

helou im a tesis student from Venezuela Working on natural gas dehydrataion at 2500 psig and 120F ive encountered numerous setbacks doing my simulations and ive been stuck wodnering what they are

ive calculated for simulation basics (aspen hysys)

column diamenter : 4.04ft
column trays ; bubble cap
glycol flow : 3.0 gal /lbofh20 absorbed (assumed)
Presure : 2500
T:120ªF
tray spacing :24 inch
ive calculated the dew point i must have at 7lb2h0/mmscf and its 47 F but the simulation sayts its 113 f at the outlet of dry gas it doesnt make sense i also change the equation from gycol package to PR and it improved alot my numbers but , with PR i cant find dew point in my inlet gas ( wet gas ) it says my presure its above critical presure i know wat it means but i dunno how does it aplly to my process because its supoosed to be saturated with water
flow : 85mmscf of natural gas

i would really apreciate feedback

regards

#2 senthil13

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Posted 09 October 2008 - 12:23 PM

Hi,

You shd refer to Design and engineering practise by Shell or petronas, commanly called Shell DEP or PTS.

Thanks

#3 Zauberberg

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Posted 09 October 2008 - 12:55 PM


HYSYS is extremely inaccurate for modeling TEG systems, and you should definitely not rely on software outputs for your process design subject. Actually, HYSYS is quite infamous with regard to glycol units modeling. This is the information I got from software vendor. Imrovements are continuously being incorporated but this is still not sufficient for TEG process design purposes.

Also, your operating pressure is very high (>170barg); water content should be very convenient for solid adsorption units application (activated alumina or mole sieves). Fractionation towers become critical at extremely high vapor densities, and this is exactly the case you have. Expect high levels of foaming and operational problems.

#4 Miguel

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Posted 09 October 2008 - 04:44 PM

thank you very much for your response i agree with u that hysys has been very inacurate and ive read alot of it in the web plus i realised it today when i used glycol package and then tryed peng robingson basically aspen hysys glycol package sux big time , but my research is to deshgn 3 processes ( cooling and separation , glicool absortion , and adsortion molcular sieve ( my choice) ) so i have to simulate all tree and compare results but basicly has been hell for my simulation and it gives me very wierd results what simulator do you recomend for me to do this process and yes i know the considerations using thes presure means the column will be very heavy and expensive and glicol will have a drag of hidro carbons to the buttom do to solubitly but still i must design it, so i would apreciate if u recomend me a simulator that fits to glicol pretty well, also i would like to know were can i find or buy Shell DEP or PTS.

PD: english is not my first language so if i slip on techincal terms i am sry
ok ty very much regards

#5 JoeWong

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Posted 09 October 2008 - 07:13 PM

This is one of the old discussion that i had with ASPEN some time ago... ASPEN has some studies shown that HYSYS is still good for TEG system. However, present of some component i.e. BTEX, it starts to deviate. This is only from ENGINEER perspective. From RESEARCH/SCIENTIST perspective, the focus may be different. In addition, ASPEN also admitted that HYSYS is not perform well in MEG system... I may check my old record...

I have used PROMAX and conducted some benchmarking activities. So far, it gave me confidence especially thus cases where HYSYS does not perform well...

I also have used PRO-II and conducted some benchmarking activities. It perform much better than HYSYS and in the same order to PROMAX.

One of the problem i have with your system is the pressure (2500 psig). It is very high. Really doubt if HYSYS, PROMAX or PRO_II will perform well in the pressure range. Hoping that other experience CheJedies i.e. Mr. Montemayor, Joerd, etc can tell the real world experience.

DEP and PTS are owned by SHELL and PETRONAS respectively. Without permission from respective company, NOBODY are allowed to quote and use these documents. Thus, it is NOT possible to BUY them.

#6 Miguel

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Posted 09 October 2008 - 08:15 PM

thank you very much i apreciate your response i will try to simulate this process in PRO II and probably ask for the company were im working to see if they have acces to promax u clarified much of my doubts , i also thought presure was to high but iwasnt sure now i am.

changing the subject, will adsortion process with moleculars sieve have the same problem ? , what software beside aspen adsim can simulate adsortion process or u recomend manual calculations for the design? , and were could i find information or what literature should i go to for information on dehydration by cooling and separation

ty very much for the help

regards from Venezuela

#7 Zauberberg

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Posted 09 October 2008 - 10:54 PM


For solid adsorbents, the best way is to get budgetary proposals from vendors such are UOP, Grace/BASF, NATCO etc. Manual calculations are likely to be inaccurate as well.

#8 Miguel

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Posted 13 October 2008 - 02:38 PM

hello again, thank you very much for the recomendatiosn and explanations

if its not much trouble could you explain a little bit deeper why absortion columns for glycol dehydration are not recomended to work at presures as high like 2500 ?

what are the consequences?
why simulators cant give accurate results at those presures?

thank you regards

Miguel Araque


#9 Qalander (Chem)

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Posted 13 October 2008 - 11:08 PM


Dear Miguel hello/Good Morning,

Although you should get better professional response(s) from other learned forum colleagues.
I just provide one simple thought that,
as per high pressure range mentioned by you& considering the withholding strength requirements
it will not be feasible and very costly

to manufacture and handle such columns.
You should appreciate.
Best regards
Qalander

#10 Miguel

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Posted 14 October 2008 - 10:19 AM

thank you for you response sir

also for heat exchangeres im a bit stuck, i would like to know how to calculate the reboiler temperature, and the poor glicol tempearture, and the regenerated glicol conecentration - once it leaves the reboiler also how much should the glicol be preheated before entering the reboiler.
also

is there any calculus algorithym i could follow for the heat exchanger especifications both Gas/poor glicol and Glicol /glicol exchanger?

#11 JoeWong

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Posted 15 October 2008 - 04:51 PM

QUOTE (Miguel @ Oct 14 2008, 11:19 AM) <{POST_SNAPBACK}>
thank you for you response sir

also for heat exchangeres im a bit stuck, i would like to know how to calculate the reboiler temperature, and the poor glicol tempearture, and the regenerated glicol conecentration - once it leaves the reboiler also how much should the glicol be preheated before entering the reboiler.
also

is there any calculus algorithym i could follow for the heat exchanger especifications both Gas/poor glicol and Glicol /glicol exchanger?


It is better to open new thread / post for different issue to ease follow-up and future search...




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