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Query- Reboiler Pressure Value
Dear Reader,
I wish to know how the Reboiler Value is taken as 1.1 atm. In the tutorial on Shortcut Distillation, the value of Condenser as well as Reboiler Pressures was 1 atm respectively. I am attaching the screenshot from my simulation of Shortcut Distillation which represent the same. The attached screenshot is from the simulation that has exactly the same values from simulation done by the tutor in the tutorial.
Also, while updating most of the values in the Rigorous Distillation simulation, there are a lot of red error messages which can be seen in the tutorial as well (for eg while updating the Reboiler pressure itself, which reads
<table><tbody><tr><td></td><td></td><td></td><td><font color="#cc3300">Error</font></td><td><font color="#cc3300">Distillation Column: Phase equilibria calculation error. (T = 373.58 K, P = 0.00 Pa, MoleFracs = { 0.4, 0.6, })</font></td><td>

Thank you for your time and suggestion.
Sincerely Yours,
B.Tech (Chemical Engineering- Third Year)
IET Lucknow
<img align="none" alt="" src="http://">

DWSIM Rigorous-Distillation 07-08 min 10-20 sec 12-07-20, 7:56 p.m. himanshu08


It is true that condenser and reboiler pressure is taken as 1 atm in the shortcut column. The reboiler pressure in the distillation column which is 1.1 atm is a very minor deviation from reboiler pressure in the shortcut column which is 1 atm and, therefore, it won't make a significant difference in the distillation column results. However, the reason behind entering 1.1 atm as reboiler pressure in the distillation column is to demonstrate how the intermediate stage pressure is generated using interpolation.

About the different error messages that keep coming is due to the "Flowsheet Calculator Active" button which is active when you are entering different input values in the distillation column. If the "Flowsheet Calculator Active" button is turned on, DWSIM will try to simulate the flowsheet as soon as an input value is entered/changed. Since entering the input data is not completed, that's why it will keep throwing the error message. The error message will not occur anymore once you complete all the required input for the column. If you wish not to see the error message, you may turn off the "Flowsheet Calculator Active" button till you complete entering all the input values. Once you complete entering the values, turn on the "Flowsheet Calculator Active" button and click on "Solve Flowsheet".
13-07-20, 12:18 p.m. priyamnayak
Thanks for your answer. It helped me a lot.

13-07-20, 12:40 p.m. himanshu08

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Check the units of "Product Molar Flow" in the Reboiler section...Change it to kmol/hr if not already selected..The software by default sets the units in mol/s in that section! Hope that solves your problem of getting error messages!!
06-08-20, 6:59 p.m. A_Iyer37

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