8 replies to this topic

[naga_chemeng]

hi guys, im going to design propane propylene distillation column... feed consists of multicomponent .. column pressure 16 kpa temp 38 - 46 c. i need vapour liquid equilibria data for these compounds propane propylene, isobutylene , ethane, and n-butane..and their relative volatility...

or any body having equilibrium constants K for these compounds butene, transbutene2,cisbutene2, isopentane,butene1. tell me how to find out ?

help me gys for my project work...

[Zauberberg]

Some of K-value charts can be found in GPSA Databook (C1 - nC10) but for other components you need to dig through your textbooks.

K-values can be obtained directly from process simulators. If there is no simulator available to you, download ChemSEP Lite version and try to model your system: http://www.chemsep.c...s/data/lite.exe
and see what K-values you are getting from the software vs. K-values obtained by using available charts, for any of the components. ChemSEP also provides an interesting literature for multicomponent distillation, browse through the website: http://www.chemsep.com/

As you have other components in the system - apart from Propane and Propylene - you will need 2 towers at least, to achieve that separation. One to remove C3 fraction from the feed, and the other one to fractionate between Propane and Propylene.

[breizh]

Hi ,
let you try this data base

http://infosys.korea.../kdb/index.html

Hope this helps
Breizh

[naga_chemeng]

Thank u zauberberg..

i downloaded that software. i read chemsep help manual. i'm facing some problems in that.. especially
thermodynamic properties.. wt should i give in k values option and reference state, reference temp, and vapour pressure heat of formation.. and feed specifications..

wt should i give degree of freedom? how i get ans from this?

my stream is sat liquid i's bubble point.

waiting for ur reply zauber..

[naga_chemeng]

Hi ,
let you try this data base

http://infosys.korea.../kdb/index.html

Hope this helps
Breizh

thank u for ur help Breizh... i tried that web but quite confusing .. we have to program to get vapour pressure in fortran?

it's all pure components... but my feed mixture of various components..
Ethane, propane,,propylene, isobutane, n-butane, butene..at 318k and 1825 kpa..

thank u for ur favour .

[breizh]

From the data base you can get all the vapour pressure and calculate the Ki .

Breizh

[naga_chemeng]

K-values can be obtained directly from process simulators. If there is no simulator available to you, download ChemSEP Lite version and try to model your system: http://www.chemsep.c...s/data/lite.exe
and see what K-values you are getting from the software vs. K-values obtained by using available charts, for any of the components. ChemSEP also provides an interesting literature for multicomponent distillation, browse through the website: http://www.chemsep.com/

To Zauberberg

Tahn

Thank ur help.. and one more thing is we dont know how to model the system even many of my classmates do not know how to do this?
how to model this? i expect ur reply.. wt ever may it is/

[Zauberberg]

Naga,

You need to specify the number of stages - and it has to be higher than the minimum number of stages. Then you need to specify operating conditions of the tower - top and bottom pressure, followed by the feed conditions (pressure, temperature, composition, flow). Finally, you need to define product purity, for both top and bottom product of the column(s). As simple as that.

[milenkom]

Hiya, Mate. I think VLE data for these components should be readily available inside process simulators themself. You can also check DECHEMA collection, but this one is also built in into commercial simulators. For components in question my best bet would be to use Peng Robinson EOS. You should also check for nonideal behaviour in the liquid phase and also if some of components will form azeotropes in which case you´ll definitly need to use activity coefficients model.
Once components are entered and you´ve got adequate Thermo model, you can model the separation using short cut column. This will give you enough data which you can then use on more rigorous column models. When modelling rigorous columns play a bit. Actually play alot change reflux ratio, feed stage, vap fraction in feed stream etc ... Generate charts separation by stages etc, there´s alot of usefull tools in Aspen or Hysys. Get some literature on the subject and compare data, check and compare everything. Get your hands dirty it´s not easy being an engineer.

PS: Also make sure you´ve got enough cafee and cigarettes in stock

Edited by milenkom, 11 February 2011 - 11:33 AM.