Calculate composition of gas mixture

[partialpressure]

Hi everyone, hope I am posting this in the right place.

I have a project where I am working with gases, each can be assumed individually to be 100 % pure. These are separately injected into a closed vessel, as in injecting 30 bar of Gas A and then 30 bar of Gas B where the closed vessel thus has a total pressure of 60 bar.

I would like to know the composition of my gas mixture as accurately as possible. Gas sampling and analysis is however not an option. I am currently using Daltons Law with compressibility factor to calculate moles of each gas. :

n(A) = P(A)V/Z(A)RT and n(B) = P(B)V/Z(B)RT
n(TOT) = n(A) + n(B), --> %A = n(A)/n(TOT) * 100 %, and %B = 100 - %A.

Would an EOS solve this better, and are there any software which could calculate this (or a MATLAB script)?

 

[chemebabak]

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[25362]

Adding pressures?

 

[MortenA]

Although i agree that this looks a lot like homework, here what i would do:

1 Decide wether you do this adisbatically or maintain a stable temperature

2) You know the volume that you are injection into - note initial density.
3) "Add gas" until you reach your desired pressure (cool if you decided stable temperature in 1)
4) Read the new average density. Any increase in density must be from the added component B (the density is P/T independant since you have a fixed volume)
5) Yse the difference in densities and the total vlume and the MW of B to calculate the added amount of B in moles.

Now you know how many mol A and how many mol B you have and thus the concentation.

The above procedure assuems that its a single phase at all times.

I would use an EOS to calculate the amount of B added in order to get the P/T required - but you could do this as an experiment if you liked. I would prefer someting like PR/SRK - but thats dead easy to say when you have HYSYS avaiable.

Best regards,

Morten