Problem with using Case Study on Aspen HYSYS

[vtf1221]

I have a problem related to using the Case Study tool in Aspen Hysys (can't assign some variables as a function of others). The simulation has converged correctly. Here I attach an extensive explanation, but at the end the problem has already been explained here.
My final purpose is to visualize the fraction of lactam lost in the overhead of the column as a function of the temperature and also the temperature obtained at the end of the bypass of one heat exchanger as a function of the mass flow bypassed.



I am working with an existing Aspen simulation that was originally built quickly and in a rough manner to perform a preliminary study of two energy integration options using two heat exchangers.

The purpose of the simulation is to evaluate an energy integration in which the heat from evaporated toluene (stream called “tolueno vapor”) is used to preheat the feed to an absorber column (stream “T-2 con precalentamiento”).
The objective is to reduce the reboiler duty, which in the model is represented by a heat exchanger called E-7-1.

• Original file: “simulación definitiva”
• My modified file: “prueba_allbypass”

What I am trying to do​

I want to run a Case Study in “prueba_allbypass” with the following setup:

• Y-axis (dependent variable): Mass fraction of lactama in the overhead stream of the column → Stream name: “TO salida”
• X-axis (independent variable): Temperature of the stream feeding the absorber column → Stream name: “a T2”

The problem​

When I open the Case Study in my file and search for variables, I cannot find:

• The mass fraction of caprolactam in stream “TO salida”
• The temperature of the stream “a T2”
• The mass or molar flowrate of the following streams:
  
  • “a bypass”
  • “alimentación a T-429-2”

However, in the original simulation, it seems that a Case Study could be performed, so I am not sure what is blocking it in my modified file.

What I believe is not the root cause​

I do not think this issue is related to:

• The use of an Adjust block to fix the flowrate of “a bypass”
• The fact that “bypass E-27” is currently fixed at 0 kg/h

My understanding is that a Case Study should be able to vary one variable and observe its effect on another, regardless of whether an Adjust is present.

Questions​

• Can anyone share my simulation where the Case Study finally shows:
  
  • The composition (mass fraction of caprolactam) of “TO salida” VS temperature of “a T2”
  • The mass flow of “bypass E-27” VS temperature of “a T2”
• Why are these variables not available in my Case Study?
  
  • What could be causing this?
  • How can I modify or restructure the simulation to make them accessible?
• What is the difference between my simulation and the original that allows the Case Study to work correctly?

Any help or guidance would be greatly appreciated.

Link to the simulation files:

• Original file: “simulación definitiva”:

https://www.dropbox.com/scl/fi/svv2wgixxytesn99vi33s/Simulaci-n-original.hsc?rlkey=jkj4tv6jhfk71q0fup6wfdbmx&st=9bmlfr8g&dl=0

• My modified file: “prueba_allbypass”

https://www.dropbox.com/scl/fi/tbzd6l6rl2x9z2o43dtv8/prueba_allbypass.hsc?rlkey=jlcagp6l7873l7vd6usaoiuo8&st=fe7ynbem&dl=0