2 replies to this topic

[PengRobinson]

Hi,

I want to simulate a Fischer-Tropsch process in Aspen Plus in a multitubular fixed bed reactor.
My issue is the following: Even though, there should be a liquid phase in my product stream (considering my process parameters, it would be very small but not zero), Aspen Plus gives me a liquid fraction of 0. 
I tested adjusting the stoichiometric coefficients for the long chained hydrocarbons and figured I get a small molar liquid fraction (0.0015) when increasing the molar flow of those long chained hydrocarbons to 0.1 % of the total product flow. Previously their flow was about 0.01 % of the total product flow. 
Therefore I am reassured it's not due to my process parameters but the issue is the low quantity. 

Now, since I am quite unfamiliar with Aspen Plus, I thought it might be a cutoff of very small fractions. 
I tried decreasing the minimum fractions in the calculation options but the issue persists.

I am using Aspen Plus V12.1 and the SRK method.

Happy for any information on this matter.

Thanks in advance to everyone!

Edited by PengRobinson, 09 February 2025 - 01:04 PM.

[Pilesar]

Did you try your own equation of state? Find the dewpoints of the thermo packages for the composition and conditions you have. Troubleshoot the system.

[shvet1]

How did you checked the reliability of the SRK thermo package for this particular reactor?

Why do you believe there shall be a liquid? How did you checkd it?

Why do you believe the problem is with the software, not SRK or real data?

Edited by shvet1, 10 February 2025 - 12:12 AM.