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Topic: phase equilibria  (Read 5287 times)

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Offline nertil1

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phase equilibria
« on: August 01, 2008, 12:01:58 PM »
I need to find the composition of a mixture of methane and heptane in a surge drum. I have the flow rate, pressure and temp. I was thinking I can do this with just reading a T-x-y or P-x-y diagram but I can't find one for methane and heptane. I was also thinking about using Ideal Solution equations to find the composition also. What should I do?


Offline nertil1

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Re: phase equilibria
« Reply #1 on: August 04, 2008, 09:07:45 AM »
I was able to use the equilibrium ration to find the composition of methane and ethane in vapor and liwuid but unfortunately I don't know how to find the overall vapor and liquid compositions, although I do have the total amount in the drum. I was thinking of using solubility data to do this but I can't find any for methane in heptane. Any help?

Offline eugenedakin

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Re: phase equilibria
« Reply #2 on: August 04, 2008, 11:42:55 PM »
Hello nertil1,

In one post, you mentioned methane and heptane, in the other, you mentioned methane and ethane ... two different questions. Which one is it?

Just for fun, could you post the mathematical work that you did to come up with an answer?

Thanks for your help.

Sincerely,

Eugene
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Offline nertil1

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Re: phase equilibria
« Reply #3 on: August 05, 2008, 08:20:09 AM »
Im sorry, it is methane and heptane (sorry for the confusion)
I started all over. I managed to find the solubility chart of methane in heptane at various temperatures. I have two locations, before a valve and after a valve
.
Before:T = 288.65K x(meth) = 5.9E-5
After: T = 266.48K x(meth) = 6.3E-5

To find the amount of methane in the liquid:
amount of meth/(amount of hep + amount of meth) = x(meth)
(I do have the total amount coming in), So I just solve for amount of methane

Similar thing to find the amount of heptane in liquid:
amount of hep/(amount of hep + amount of meth) = (1-x(meth))

Now my question is how would I find the amount of hep and meth in the vapor? K ratio?

thanks

Offline Gerard

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Re: phase equilibria
« Reply #4 on: August 06, 2008, 11:20:53 AM »
i dont know if this is correct but if it is kindly do correct the equation i derived:
if:
Pa=YaPt
Pa=XaPvap
therefore:
YaPt=XaPvap

where Pa=partial pressure of component a
Ya=is the moles in vapor phaseof component a
Xa=is the moles in the liquid phase of component a
Pvap=vaporization pressure of component a(pressure it takes to vaporize component a at a particular temperature)

hope this will help you
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