3 replies to this topic

[barbieros]

Hi everybody.

I have 2 questions:

1) I'm studying a mixture of water and ethylene in a flash separator and I'm using Aspen Plus to simulate the process. I read many things in Aspen Helps to select the thermodynamic model. For what I read I think SR-Polar is a good model to Vapor Liquid Equilibrium. But I'm still in doubt. Could be another model like NRTL with RK as vapor model or SRK ? What's the best ?

2) I'm using Aspen Dynamics the first time, so I'm having problems trying to adjust the controllers of a destillation process. I put the set-point, for instance, 0.25. When I reach Enter, the number goes to 0. I'm not able to put numbers with fraction. What am I doing wrong ?

Thanks everyone.

[barbieros]

Does anybody know ? Even the question about Dynamics ?

[Root]

Hi,
the answer of your 1st question is , use SRK or PR because, the case you are simulating is Hydrocarbon based.
2nd question let to weight for some expert, come and explain the question.
Good luck

[Steven_Zhu]

Hi everybody.

I have 2 questions:

1) I'm studying a mixture of water and ethylene in a flash separator and I'm using Aspen Plus to simulate the process. I read many things in Aspen Helps to select the thermodynamic model. For what I read I think SR-Polar is a good model to Vapor Liquid Equilibrium. But I'm still in doubt. Could be another model like NRTL with RK as vapor model or SRK ? What's the best ?

2) I'm using Aspen Dynamics the first time, so I'm having problems trying to adjust the controllers of a destillation process. I put the set-point, for instance, 0.25. When I reach Enter, the number goes to 0. I'm not able to put numbers with fraction. What am I doing wrong ?

Thanks everyone.

I just reply the second question:
From your description, I resume that you using PID controller, when you want to active PID controller, you must connect the necessary stream, also you need to transfer the control model from manual to auto mode, so it can work well afer you finish.

By the way, to give the right P, I , D parameter is very important for you to control the process varialbes.