contact method - flash with inert gas

[gelsi]

In a flash drum, inert gas can be used to put down the vapour pressure of a component and so increase its transfer from liquid to vapour phase. In particular when, fixed the temperature, there is necessity to due the operation at vacuum pressure, inert gas can allow the operation to less negative pressure.

Now the question:
1) It's possible to have the right contact between liquid and inert gas (nitrogen) to consent the flash of light component, without filling in the coulumn, but only distributors?
2) If Yes, how I can calculate the right bubble size?
3) I think that a static mixer istalled upstream of drum can be a better solution than two complex internal ditributors, but what size must have the bubbles of gas?

Thanks for reply

 

[gelsi]

read "filling" like "packed"

 

[ash9144]

So you are proposing performing a multistage separation in a single stage by adding a little inert gas?

 

[gelsi]

Yes, an "equivalent" multistage, but somethink also:
a vacuum multistage operation needs an operative absolute pressure minor than vapour pressure of separating component, at max temperature available (Low steam utilities is used, so we can say about 120°C).
Using inert gas, it's possible an higher pressure and so a smaller vacuum system.
All Your critical comments are welcome.

My worry is the size of bubble and performance of unit without traies or packed bed. Help...

 

[gelsi]

my idea is to make a single teorical stadium with a packaed tower with nitrogen to rise the pressure from 0.004 to 0.15 bara.

 

[Compositepro]

An inert gas flow can promote "stripping" where the gas will move the volatile away from the liquid interface and increase the concentration difference that drives vaporization. However, increasing the absolute pressure will prevent "boiling" where volatiles can be turned to vapor in the liquid that is not at the liquid interface. Boiling is more efficient than stripping when it can be done.

 

[StoneCold]

I think he is saying he wants to increase the total pressure of the system using Nitrogen so he does not have to get to as low a vacuum. Not really stripping using an inert gas. He will maintain the same temperature, and the partial pressure of the component will be the same.

StoneCold

 

[gelsi]

that's true stonecold