I am modelling a CDU using Aspen Plus. The current objective is to tune the model to the actual plant behavior (test run data) so that the CDU model can be further integrated with preheat trains, VDU, stabilizers etc for optimization studies.
I have test run data for the CDU, including D86 volume curves for the crude and its products which I am trying to match using an Aspen Plus CDU model (PetroFrac). I am able to converge the column with all its pumparounds, strippers etc but I am having trouble matching the D86 curves for the products that I get from the model.
For example, the Heavy Naphtha cut from the test run has an IBP: 104 C and FBP: 144 C while I get a much wider range from 87-177 C. Similarly, I have issues with Kero, LGO, HGO cuts as well, where the differences are even greater. Even if I ignore the IBP and FBP and look at 5-95% curves, the differences are significant. Moreover, I do not see a trend, the Light Kero cut is surprisingly closer to the test run. I am unable to manipulate draw flowrates or return temperatures as those have been provided by the client and cannot be changed, that leaves me with only being able to manipulate the stage efficiencies. I will appreciate if you could provide some guidelines on how to manipulate the efficiencies so that my cuts have a better/closer D86 fit or if there is anything fundamental that I may be overlooking. I am using section-wise efficiency method and have divided it into 10 sections.
I am attaching an Excel spreadsheet with the BPs of the cuts that I get from the model vs the test run data (highlighted in yellow). Thank you very much for your help in advance.