Dear Saeed,

Aspen can calculate the bubble point pressure of a liquid mixture or the vapor pressure of a pure component.   You can check the vapor pressure predictions for pure components in Aspen by using the Analysis feature in the Properties section of Aspen Plus.   Depending on the Property package you will either be using the equation of state, or a vapor pressure equation like Antoine or Wagner.   If you confirm that the vapor pressure predictions from these methods are reasonable then moving forward to regress binary parameters may be the next step.  

If the predictions are not accurate, you may want to try selecting a different Pure Component data bank to see if you get better pure component vapor pressure predictions.   There are some helpful examples of how to quickly generate vapor pressure curves for pure components in Aspen Plus that are available on the Aspen Tech website once you register (free).

Generally speaking the quality of the pure-component data in Aspen is quite good, so if you have an obscure component or one that doesn't have readily available data, you may want to get best estimates from other sources and develop Antoine or Wagner parameters based on that data so you can provide them as input data for you regression model. 

Best Regards,

Dave

The default model is PLXANT Extended Antoine vapor pressure

model. You can find the equation in the appendix of this document http://infohouse.p2ric.org/ref/22/21210.pdf

Best regards

Dear Dania, Dave and Elias

Thanks for your answers. My question was mainly about the method that Aspen Plus applies in calculating the vapor pressure of the compounds in the case we are using an equation of state. In this case, I was trying to calculate the vapor pressure of methanol using PC-SAFT equation of state. I noticed that the vapor pressure calculation is quite accurate while I put it on UNIQUAC model but not for PC-SAFT EOS.

My final conclusion after discussing with colleugues (which seems true) is that an equation of state can calculate the vapor phase as well as the liquid phase, so it does not need any extra vapor pressure to be calculated using an extra vapor pressure equation such as Antoine equation. So, I tried to fit the parameters of PC-SAFt for the pure compound (in this case it was methanol) and the vapor pressure is calculated correctly afterward.

Thanks for your suggestions and comments again.

Sincerely

Saeed

you can using the property estimation of aspen plus to estimate the vapor pressure of pure compound.