CO2 absorption with H2O/MEA/DEA

[HenkF]

Hi,
could anyone advise me on the suitability of COCO/COFE for removing CO2 from a gasstream by a MEA/DEA/water solution?
is any of the available EOS models capable of modeling this or should I use an activity model.
regards, Henk

[jasper]

This is not an easy system from a thermodynamic point of view. The CO2 that dissolves in the liquid is only part of the CO2 that will be adsorbed; the CO2 that reacts with the amines is what you are interested in. Also the reaction of H2O to form H2CO3 should probably be catered for, which depends on the pH and ionic strength.

To model such a system with any accuracy you need a specific property package that does reactions and electrolytes in the liquid phase. TEA will not do this for you.

Of course if you have measurements of the results within the operating region that you are interested in you can also approach the CO2 absorption as an interpolation problem. But this too requires some custom thermodynamics package.

[HenkF]

Thanks for your feedback.
I remember such a problem solved by using an apparent approach for species, no use of ionic species. I will dig in somewhat deeper, maybe using an Excel UOP which calculates the equilibria using ionic species and return the apparent composition. To be continued.
regards, Henk

[jasper]

This would calculate the adsorption locally. If you need it throughout your flowsheet you are likely better off putting it in a property package implementation.

[colancto]

Most commercial simulators are proposing an amine package that represents such a system. I am pretty sure most of the parameters needed for such a system may be found in the open literature, or at least the experimental data obtained on such a system. I have no information on a free to use Property package on such a system.