1 reply to this topic

[tomr91]

Hello everyone,

I have a static (steady-state) simulation in Aspen HYSYS that is fully converged, and I want to convert it to a dynamic simulation. I understand that dynamic mode requires additional specifications and configuration adjustments, but I’d like to ensure I’m covering all necessary steps.

Here’s what I’ve done so far:

1. Base Simulation: The steady-state simulation is converged, with all material balances, energy balances, and pressure drops accounted for.
2. Transition to Dynamics: I switched the environment to "Dynamics" in HYSYS.

Now, I’m facing challenges in configuring certain elements to make the dynamic simulation run smoothly. Could you help me identify the necessary steps to successfully transition from static to dynamic mode? Specifically:

• Equipment Considerations: What modifications do I need to make to equipment such as columns, compressors, and heat exchangers?
• Holdup Parameters: How should I set holdup volumes for vessels, columns, and reboilers?
• Controller Tuning: Are there specific control schemes or tuning guidelines I should follow for dynamic mode?
• Initialization and Stability: How can I ensure smooth initialization of the dynamic simulation without running into convergence or instability issues?
• Pressure-Flow Specifications: What’s the best way to define pressure-flow relationships for streams?

I’d greatly appreciate any advice, best practices, or resources you could share to guide me through this process.

Thank you!

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[Dacs]

 

Equipment Considerations: What modifications do I need to make to equipment such as columns, compressors, and heat exchangers?

 

Column: Tower ID, tray details (type spacing, weir height, weir length, downcomer volume)

Compressor: Compressor curves, motor data 

HEx: At a minimum - tube/shell volumes, UA (overall/shell/tube)

 

Holdup Parameters: How should I set holdup volumes for vessels, columns, and reboilers?

 

 

Vessels: Per equipment dimension

Columns: Per equipment dimension and tray details

HEx: At a minimum - you need to manually calculate from equipment details and plug it in the model. While I haven't personally tried doing this, I believe you can also define the HEx details in more detail (like in EDR)

 

 

Controller Tuning: Are there specific control schemes or tuning guidelines I should follow for dynamic mode?

 

If you're simulating an existing facility, use as-built information. If not, then implement the control loops as per your design P&ID. Tuning parameters are per company philosophy so seek guidance to your standards. Otherwise, use the "auto-tuning" in Hysys (never used it in any of my dynamic models before though, so YMMV)

 

 

Initialization and Stability: How can I ensure smooth initialization of the dynamic simulation without running into convergence or instability issues?

 

 

This is a very tough one. This is more of an art than science. Just make sure you are defining the boundary conditions in all your inlet/outlet streams, by ticking the right boxes in your pressure/flow specification. And keep your fingers crossed when running it!

 

Pressure-Flow Specifications: What’s the best way to define pressure-flow relationships for streams?

 

 

From steady-state!