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separator calculation (Ki ratios)

separator calculation (Ki ratios)

separator calculation (Ki ratios)

(OP)
Hi, I'll be very helpfull to see someones separator calculation in order to obtain liquid and gas composition at desired separator pressure and temperature.
I'm getting sum of mole fractions of gas phase=1, but for liquid fraction I get numbers different than 1.
I attached my example.
Also I used Kessler-Lee correlation for C7+ critical temperature and pressure, Edmister correlation for C7+ accentric factor, and Wilsons correlation for Ki.
 

RE: separator calculation (Ki ratios)

It look like 1 to me?

Best regards

Morten

RE: separator calculation (Ki ratios)

(OP)
sum of xi is 0.8239
I'm not sure if it's correct.
 

RE: separator calculation (Ki ratios)

Now i see it - whats the vapour fraction?

If its 1 then it may be rounding?

Im assuming that its not something like "dry basis" where in reality water is present?

Best regards

Morten

RE: separator calculation (Ki ratios)

(OP)
I appologize for not explaining the symbols.
xi is the composition of the liquid phase
yi is the composition of the vapour phase

zi is composition before separation
As far as I know, this should be satisfied: sum zi = sum yi = sum xi
nL is quantity of the liquid phase, ng is quantity of the gas phase. I guessed nL by newton-rhapson iterration method in order to satisfy sum zi=1, calculated from nL and corresponding Ki ratio.
omega is accentric factor for the component - from book, and omega for C7+ fraction is calculated from correlations (MC7+ -> pseudocritical T and p -> omega C7+)
nL + ng should equal one.  

RE: separator calculation (Ki ratios)

As i suspected the nL is very low.

I think it may be a round error that gets accepted because the overall error is sufficient low.

If this does not make you "happy" then you must call the support line smile

Best regards

Morten

RE: separator calculation (Ki ratios)

(OP)
Thanks. So you think such big error occurs with condensates that vaporize very quickly?

RE: separator calculation (Ki ratios)

No - I would assume that your simulator is steady state - and its always at equilibrium.

Im talking about a numerical error that is accepted (by the software) because the liquid part is small compared to the overall phase.

Best regards

Morten

RE: separator calculation (Ki ratios)

(OP)
I don't use simulator, unfortunatelly my antivirus detects a virus in registration tool ˙:(.

I just made spreadsheet calculation and then guessed nL using solver, ie. I guessed nL until sum of zi was zi=1
I think this method should work, but anyway - the error
repeatedly occurs (I have only one analysis, so I just change separator pressure)

RE: separator calculation (Ki ratios)

well my guess is the only one i will still cling to (except then maybe an error en your homemade sheet): The overall error is acceptabel since your liquid fraction is so small.

Best regards

Morten

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