9 replies to this topic

[irreplaceable]

Hello!
I have a little question. I have ternary system, which consist 2 gas and water. Gases dissociate and is weak electrolytes. How do I to calculate composition of vapour phase which is be in equilibrium with liquid phase, if we know composition of liquid phase, temperature and pressure.
Thanks in advance!
Regards,
Denis.

[Dacs]

Hello!
I have a little question. I have ternary system, which consist 2 gas and water. Gases dissociate and is weak electrolytes. How do I to calculate composition of vapour phase which is be in equilibrium with liquid phase, if we know composition of liquid phase, temperature and pressure.
Thanks in advance!
Regards,
Denis.

I don't see how this becomes a ternary system since gases are miscible with each other. This will result in a binary system (gas-liqud) unless your liquid forms 2 phases (eg water-HC).

Review Raoult's Law for starters.

[irreplaceable]

I don't see how this becomes a ternary system since gases are miscible with each other. This will result in a binary system (gas-liqud) unless your liquid forms 2 phases (eg water-HC).
Review Raoult's Law for starters.

Yes, sure. You are fully right. It was mistake. I meant that system is not ternary, but have 3 components, but in fact, as you said, it's binary system. So I need know how do I calculate composition of vapour phase which is be in equilibrium with liquid phase, if I know composition of liquid phase, temperature and pressure.
Thanks in advance!

[DanW]

Yes, sure. You are fully right. It was mistake. I meant that system is not ternary, but have 3 components, but in fact, as you said, it's binary system. So I need know how do I calculate composition of vapour phase which is be in equilibrium with liquid phase, if I know composition of liquid phase, temperature and pressure.
Thanks in advance!

As the liquid phase is at its bubble point, you can try a bubble point calculation.

[Dacs]

I don't see how this becomes a ternary system since gases are miscible with each other. This will result in a binary system (gas-liqud) unless your liquid forms 2 phases (eg water-HC).
Review Raoult's Law for starters.

Yes, sure. You are fully right. It was mistake. I meant that system is not ternary, but have 3 components, but in fact, as you said, it's binary system. So I need know how do I calculate composition of vapour phase which is be in equilibrium with liquid phase, if I know composition of liquid phase, temperature and pressure.
Thanks in advance!

As I said in my previous post, you can start by considering Raoult's law.

To elaborate, if you are given a mixture of gases, the first droplets that would form (at dew point) can be calculated using Raoult's law (and Antoine Equation).

Same thing goes for liquids at bubble point.

If you have an access to process simulators (such as Hysys), this will take much of the legwork for you

[irreplaceable]

I have ChemCad. Can you please advise me how use Chemcad to calculate this equilibria?

[Dacs]

I have ChemCad. Can you please advise me how use Chemcad to calculate this equilibria?

I'm not familiar with ChemCad but most probably this might apply as well (this works on Hysys).

Setup your stream and input the compositions (vapor or liquid, whichever is given). Then input the pressure then either input 1 (if you have vapor) on the vapor fraction (of course input an arbitrary number of flowrate to make sure that the simulator will solve the stream). The temperature calculated would be the dew point. Input 0 (if you have liquid) on vapor fraction and it'll give you the bubble point.

In case of Hysys, it'll also give you the composition of the other phase. You just have to do whatever is needed for ChemCad to execute the procedure I stated above.

Or just do a manual calculation. It's pretty much straightforward if you're just talking about 2 components.

[kuldeepd]

May be this website helps,

http://processcalculator.com

[siddiqsh]

I have ChemCad. Can you please advise me how use Chemcad to calculate this equilibria?

I'm not familiar with ChemCad but most probably this might apply as well (this works on Hysys).

Setup your stream and input the compositions (vapor or liquid, whichever is given). Then input the pressure then either input 1 (if you have vapor) on the vapor fraction (of course input an arbitrary number of flowrate to make sure that the simulator will solve the stream). The temperature calculated would be the dew point. Input 0 (if you have liquid) on vapor fraction and it'll give you the bubble point.

In case of Hysys, it'll also give you the composition of the other phase. You just have to do whatever is needed for ChemCad to execute the procedure I stated above.

Or just do a manual calculation. It's pretty much straightforward if you're just talking about 2 components.

can you elaborate more on manual calculation using equation of state

[xtianchem]

May be this website helps,

<a href="http://processcalculator.com" target="_blank">http://processcalculator.com</a>

hello
i dont know how this page estimate the values do you think they are giving us good values they dont say which equations or references take, but if you are a student it can help you.
best regards
xtian