CSTR-Evaluation Failed

[nrgeng]

A flowsheet that solved yesterday does not solve today after I updated with CUP. The EquilibriumReactor Unit with the same Reaction Package solves, but not the CSTR Unit. Both flowsheets solved without errors yesterday.

Also, depending on the sequence that I follow before editing the flowsheet Unit to delete one of three reactions, the “Solve failed:” dialog changes between two versions:

(1) Solution failed: Function evaluation failed. Failed to obtain reactionRate for reaction . . .

(2) Solution failed: Function evaluation failed. Internal error; unknown reaction basis . . .

I thought that the CSTR configured for equilibrium reactions was equivalent to the EquilibriumReactor configured for a single known phase. What am I missing?

[jasper]

Please send me the fsd file?

[nrgeng]

With a great deal of effort, I created a new simulation for the Hydration of Ethylene. I hoped that the same problems would occur with this new CSTR simulation as had occurred with the previous Methanol simulations. All of the same problems do present themselves so my efforts have not gone to waste.

I am attaching two flowsheet files showing the two “Solution failed;” messages that I receive when attempting to solve the CSTR Reactor Unit with a single equilibrium reaction. As described in an earlier Posting, the sequence of events prior to receiving the Message determines which of the two Messages that I receive.

(1) Solution failed: Function evaluation failed. Failed to obtain reactionRate for reaction . . .
(2) Solution failed: Function evaluation failed. Internal error; unknown reaction basis . . .

It may be of note that the CSTR simulation solved before the update. The problems presented after an update with CUP on April 19. I updated again before I ran these simulations so that I was up to date. I am reporting these as fresh results. Again, the Equilibrium Reactor simulation solves as shown in another posting, Ethylene (equilibrium) V1.1 M1.pdf.

I e-mailed the fsd file to you. I hope this is easier for you than it was for me.

NB. The file size is too large so I will have to send the second file with another message.

[nrgeng]

This is the second file as stated in the previous posting. File: CSTR (equilibrium) V1.0 (fail, 1)

NB. The file is too large to send. Please request it if you need it. I may be able to shrink it in size (256 kB max.).

[colancto]

What is the size of the file you try to attach?

[jasper]

Version 2.5.0.10 indeed introduced a bug in the CSTR reactor. Apologies for the inconvenience, and thank you for reporting. This is now fixed (CUP).

Typically to debug such a problem I am looking for any fsd file that reproduced the problem. It does not have to be an accurate representation of your setup, but it merely has to show the problem so that I can see what is going on. My e-mail limit it a lot higher than the forum limit. Thank you again.

[jasper]

I thought that the CSTR configured for equilibrium reactions was equivalent to the EquilibriumReactor configured for a single known phase. What am I missing?

They are only equivalent provided the Equilibrium Reactor operates in a single phase region. The CSTR mixes kinetic and equilibrium reactions, but is limited to single phase. The Equilibrium Reactor only deals with equilibrium reactions, but calculates the (reactive) phase equilibrium as well.