8 replies to this topic

[Satheshchem]

Hi,
I am getting an error stating "A temperature stream is not found at requested condition" while doing flashing for high pressure condensate @ 98 barg( want to calculate relieving temp& mass heat of vap).
Can any one advice me why I am getting such error The same stream is getting flashed @30 barg pressure .my liquid mixture consists of methane, ethane, propane, butane, pentane etc

[Bobby Strain]

Raise the pressure in increments until you get the error. This should give you a clue. And you should be using PR or similar EOS.

Bobby

[Dacs]

Check your stream critical pressure. There's a utility in Hysys (CTRL + U, choose Critical Properties) for you to check.

[Satheshchem]

Dear sir(s),
Am unable to calculate even critical properties.am getting an error called "Utility critical properties-1 is not available with the property package ". I have used PR and SRK.
Am giving my fluid composition below in mole fraction.
Methane:0.024
Ethane:0.06
Propane:0.263
I-butane:0.084
n-butane:0.266
I-pentane:0.094
N-Pentane:0.102
N-hexane:0.104
H2s:0.01
Nitrogen:0.001
Co2:0.001
Operating temp is 37.7 deg c
Operating pressure is 46.5 barg

[breizh]

Let you try this resource .

http://www2.questcon...mo/thermot.html

Breizh

[PaoloPemi]

it may happen that a software fails to find a solution but
it could also be a inconsistent specification,
to detect these cases my preferred tool is the phase envelope,
I did a test with Prode Properties (see prode.com), the results are in the attahced file phaseenvelope.jpg,
temperatures in Celsius, pressures in Bar
as you see at 96 Bar you are well above cricondenbar in dense phase,
at that condition you can't solve a VLE equilibrium point (if that was your intent)

Attached Files

•  phaseenvelope.jpg   110.75KB   28 downloads
•  composition.jpg   39.77KB   17 downloads

Edited by PaoloPemi, 23 October 2012 - 02:12 AM.

[Dacs]

Strange, I just made a quick check and I was able to run it (BTW, phase envelope utility would also yield the same data)

(see attached file)

Anyway, the calculated value is similar with what PaoloPemi arrived at.In short, you're operating at supercritical region and saturation properties (VLE) won't make any sense.

Attached Files

•  Crit Prop.jpg   85.73KB   19 downloads

Edited by Dacs, 23 October 2012 - 02:40 AM.

[Satheshchem]

Dear sir(s),

Thanks lot for your reply .some eos package is not compatible with that process condition.i have used sour SRK but PR is able to solve .yea my fluid is at critical point.actually I was trying to size a psv during fire scenario when my fluid is critical point ..

[PaoloPemi]

that could depend from the type of operation you are attempting to solve,
as said you can't include in your specification an equilibrium point (i.e. liquid fraction, vapor fraction) as above cricondenbar you are in dense phase where a EOS predicts similar properties for liquid and vapor phases...
However you should be able to solve all other types of operations,
at least the isothermal flash shouldn't fail,
take care to utilize a suitable procedure for sizing a psv discharging that fluid, see this thread
http://www.cheresour...ng-temperature/