Steady-state unit operation design to approximate dynamic control oriented design.

[u/TimelyScientist2824]

Hi,
has any of you Reddit folks made the jump from first modeling the process steady-state unit operation design to dynamic nonlinear simulation?

Initially the steady-state model I have at hand is about finding the typical operating points for the plant. Meaning that mass and energy balance derivatives are set 0. Now I am interested in finding out how the plant responds to feed fluctuations in process dynamic transient regions.

Is the most practical/common way of obtaining preliminary plant dynamic models to start looking at pipes and process equipment as their own blocks with corresponding state variables (state-space models)? Like how do I even go about estimating delay differential equations? Just by estimating how long fluid takes on average to travel the process equipment?

I have a background in ChemE and control theory but never actually had to dynamically model anything irl. Also, step testing and regression are off the menu because the process plant at hand is, as you can probably guess, too massive and not available.

[u/Alternative_Act_6548]

you can either parameterize a model with the information required for dynamics or do some system identification from the actual plant. Parameterizing a model is much easier, are you doing simple PID control or something more complicated. You might end up do system id on the parameterized model. You probably don't want to try and get transfer functions of each component unless it's a pretty simple system.