3 replies to this topic

[Seonwoo]

Hello,
I would like to simulate the scrubbing of water-soluble components from a gas stream using water in Aspen Plus, and I have a few questions regarding the modeling approach.

In the RadFrac column model, there are two base options: Equilibrium and Rate-based. However, I’m not entirely sure what kind of "equilibrium" the Equilibrium model refers to.

From what I’ve learned in my studies, scrubbing of water-soluble components is typically modeled using mass transfer coefficients, which are then used to calculate NTU and HTU values to determine the required column height.

In contrast, the Equilibrium model in RadFrac appears to be based on phase equilibrium, possibly using K-values and vapor-liquid equilibrium (VLE). I am unsure whether this equilibrium-based approach is appropriate for modeling simple physical absorption, as in the case of scrubbing without chemical reaction.

I have seen some cases online where the Rate-based model is used, but those were for reactive absorption systems like CO₂ absorption using MEA.

Could you please advise on whether the Equilibrium model is suitable for modeling simple physical absorption (scrubbing), and if not, what would be the appropriate modeling approach in this case?

Thank you.

[Pilesar]

Start with the equilibrium model. It should work just fine. Does a simple flash unit with your gas and water give some component separation? The equilibrium model is essentially a series of flash units. Only used rate-based if you know you need it. Do you have a real data set to compare? An internet search for the system you want to model may provide clues to help.

[Seonwoo]

Although the simulation runs and produces results when using the Equilibrium mode, I am unsure whether this approach is truly appropriate for my system.

As you mentioned, if the column calculations in Equilibrium mode are fundamentally based on flashing behavior, then does that mean the Equilibrium mode should not be used for solubility-driven scrubbing processes, where no actual phase change occurs?

[breizh]

H,

Why don't you give us information about your system before talking simulator?

note: a google search will tell you the capability of the software.

key words aspen plus physical absorption

Good luck,

Breizh