4 replies to this topic

[chem400]

Dear all,
Can anyone please explain me how to determine the vapour pressure of a multicomponent hydrocarbon mixture theoretically?.

Is there any source or link ,where i could get a clear idea?

thanks for information sharing

[hoyoku]

You can use the Antoine Equation.

Dear all,
Can anyone please explain me how to determine the vapour pressure of a multicomponent hydrocarbon mixture theoretically?.

Is there any source or link ,where i could get a clear idea?

thanks for information sharing

[MrShorty]

Antoine equation can work for pure compounds. However for mixtures one would usually use a more involved process involving activity coefficient equations and/or equations of state with appropriate interaction parameters.

For a simple mixture of chemically similar hydrocarbons, you could maybe assume Raoult's law (Py(i)=P*(i)x(i) where Py(i) is the partial pressure of component i, P*(i) is the vapor pressure of pure i, and x(i) is the liquid mole fraction of i) holds and calculate the VLE that way (put Raoult's law into a search enginie. Wikipedia and other sites have decent descriptions of Raoult's law).

Caution, though, The assumption of an ideal solution built into Raoult's law is very limiting in terms of it's utility and accuracy. It depends on what exactly you are being asked to do, but this might be adequate.

[Art Montemayor]

The Antoine Equation is NOT a theoretical relationship. It is based on empirical constants - and is limited to a specific temperature range..

An equation of state (EOS) is what is theoretically used. However, I wouldn't use theoretical means.

If you are interested in an excellent article, I recommend you read the attached one by Andrew Vieler. I highly recommend every student of chemical engineering read this paper through-and-through, especially those of you dealing with simulators.

I wish all the people posting in the Simulation Forum would read it.

 Uncovering_the_Realities_of_Simulation.doc   96KB   177 downloads

[riven]

I wish all the people posting in the Simulation Forum would read it.

 Uncovering_the_Realities_of_Simulation.doc   96KB   177 downloads

Excellent articles, best:
"For some reason, error analysis seems to be a lost art, and novice users of process simulation tools seem to forget that, although their simulator may display temperatures to four decimal places, only rarely will more than one actually make any sense. For some whimsical reason, it seems that the computer replaces the lab such that it provides results with quasi-infinite accuracy. "