4 replies to this topic

[Nikunj Gangar]

i am solving one of practice the sums given in a text for sequencing of distillation train.
Separation of 8 components into 7 product streams needs to be done.
Prods are H2+C1, C2ene, C2, C3ene, C3, nC4 and nC5.
I need relative volatility data of adjacent products for this.

My question is:
Should i use Depreister charts for predicting K values and then predict relative volatility (i've never used one so can some please guide me how to use them) or should i use the normal Raoult's law which includes activity co-eff's.? Prediction of activity co-eff's is very tedious manually.
Is there any other method by which we can predict relative volatilities??

[ankur2061]

Nikunj,

You need to refer to Section 8.16, Chapter 8 of Coulson & Richardson Vol. 6. The section is devoted to phase equilibrium data. DePriester charts are vailable as Fig 8.3 (a) and 8.3 ( in the same section. There is no rocket science involved in reading these charts. The K-value is a function of the pressure and temperature of the hydrocarbon. Draw a line from the pressure value to the temperature value across the chart. From the intercept point for the given hydrocarbon curve read the K-value directly.

In case you don't have access to DePriester charts, I have posted a spreadsheet for "Flash Composition" on the forum where the charts are shown. Following is the link:

http://www.cheresour...3896#entry33896

Hope this helps.

Regards,
Ankur.

[breizh]

HI ,
These papers could help you :

http://faculty.ksu.e.../CHE411/CH4.pdf

http://puccini.che.p...#494,1,Enthalpy vs. Composition – Ponchon-Savarit Plot

Breizh

[Zauberberg]

See the extract from Stanley Walas' book dedicated to process design heuristics (rules of thumb). Some information about column sequencing can be find therein:

http://www.aiche.org.../heuristics.pdf

[Padmakar Katre]

Dear,
If you are looking for the vapor liquid equilibrium K values prediction for certain HC systems you can use a commercial simulators available. If your college doesn't have an educational version of these standard simulators then you can use the books listed below and the procedures,
1. API Technical Data-book for refining, Chapter-8 (Vapor Liquid Equilibrium K values)
2.GPSA Engineering Data-book, Chapter-25 (Equilibrium Ratio(K) Data)
And if you are looking for the "Distillation Sequencing" in general I will recommend you the following reading,
1.Chemical Process Design and Integration by R. Smith, Chapter-11 (Distillation Sequencing".
Hope it helps you.