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Distillation column with GERG 2008 AGA 2017
2

Distillation column with GERG 2008 AGA 2017

Distillation column with GERG 2008 AGA 2017

(OP)
I did some tests with the steady state column in Prode Properties to compare EOS models such as Peng-Robinson, Soave etc. (the Extended PRX-SRKX versions in Prode) with GERG 2008 model which should be more accurate on both vapor-liquid and enthalpy,

for several separations (HC) I observe that results are not too different (GERG 2008 vs. PRX models in Prode),

also, the phase diagrams (GERG 2008 vs. PRX models in Prode) show limited differences (1-2 K or less after tuning EOS) which could explain the limited differences with columns (a similar VLE),

I would ask the Prode experts in this forum, should I prefer GERG 2008 when solving compressors, pipelines etc. or is it preferable to adopt GERG in all cases (VLE etc.) ?

RE: Distillation column with GERG 2008 AGA 2017

in my opinion (not from an expert) multiparameter models such as GERG 2008 do not offer large advantages (compared with extended EOS) for phase equilibria, however for V, H, S (and derived as speed of sound etc.) these models are more accurate,
certainly, if you wish to model a compressor, GERG 2008 can be the best option (considering the model includes 21 chemicals only),
but a extended EOS such as Prode PRX can give values reasonably close to GERG reference,
also Prode can include MBWR which could be another good option, depending from application...

RE: Distillation column with GERG 2008 AGA 2017

I would say it depends from application,
for process design in many cases a 1-3 % error is acceptable,
in other cases (for example fiscal metering etc.) one wish to obtain best accuracy.

RE: Distillation column with GERG 2008 AGA 2017

(OP)
yes, when required one should adopt GERG 2008 or other complex models.


RE: Distillation column with GERG 2008 AGA 2017

Depends on your pressure range. High pressure and composition with various non methane compounds, I would prefer GERG for compressor calcs. Not only because of enthalpy but isentropic exponents and compressibility could effect power and discharge temperature calculations significantly. I think however that it would still be hard to have these results when obtained via GERG and other EOS deviate one another by more than 5 percent.

RE: Distillation column with GERG 2008 AGA 2017

(OP)
rotw,
I agree with you, I compared GERG 2008 and several EOS models with polytropic compression test cases provided by R.A.Huntington in 1985 (and 2017) papers,

for CO2 Pin 75.85 Bara Tin 310 K Pout 413.7 Bara Tout 460 K

Huntington 3 points model (included in Prode Properties) gives these values:

GERG 2008 Head (Kj/Kg) 80.336 Eff. 0.6439

Lee Kesler (Ploecker) Head (Kj/Kg) 80.680 Eff. 0.6326

SRKX (Soave Extended) Head (Kj/Kg) 81.35 Eff. 0.707

other models (Peng Robinson etc.) give similar values (with differences about 1 Kj/Kg on Head),

for these calc's GERG 2008 is probably the best option.

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