3 replies to this topic

[aransari85]

Dear All,

I had previously used HYSYS/UniSim for simulation, now i have to use PRO-II, I need your help for specifing efficiencies in the column.
In PRO-II there is option of tray efficiency, inside this option there are three sub options as murphee efficiency, equilibrium efficiency and vapor efficiency. I have to select any one of these three.
I need your expert openion for selecting these efficiencies. I have seen a big difference when i sepcify equillibrium efficiency and murphee efficiency. please advice me.
I have to simulate refinery fractionation column.
Your valuable inputs are very useful.
Thanks in advance.

Best Regards,
ARA

[abhi_agrawa]

ARA,

I usually do not use these efficiency factors. What I do is as follows:

- For new designs, I optimize the number of stages in the simulation and for the actual column, I divide the number of theoritical stages by column efficieny to get the actual number of stages.

- For checking the existin column, I assume some efficieny and based on the efficiency I estimate the theoritical stages. The I simulate the column and tune the theoritical stages to match the plant data. Now column efficiency is known.

You may also go through the earlier discussion in this forum: http://www.cheresour...ray-efficiency/

Hope this helps you,
Abhishek

Edited by abhi_agrawa, 18 January 2012 - 09:37 AM.

[aransari85]

Hi Abhi,

Thanks for the information.

Yes i used same method for new column and for matching existing column performance.
But in some cases i have faced problem where i have to tune the stages to match the plant TEST RUN RESULTS data. In the column across the fractionation section, between pump around section, it may be having some 2.5 stages in actual, with 2.5 stages i may match the result data ASTM D86 temperatures. If i put 2 stages then i am getting some less amount of separation and when i put 3 stages i am getting little more separetation which result in 10 Deg C mismatch in the simulation result and actual test run results.

I still can go with above approximation and keep 2 or 3 stages for this section. For more accuracy i want some inputs where i can tune the simulation more close matching the plant results.


Regards,
ARA

[abhi_agrawa]

ARA,

In such a case I usually go with the lower tray efficiency. Thus the actual plant performance is slightly better that that predicted by simulation.

abhishek