6 replies to this topic

[Spliknot13]

so today I had a tour at the plant for edible oils and one of the operators said that the vacuum in the distillation columns is produced by contacting steam with water in a tank, where a pipe is connected to the distillation column and that produces vacuum and said that this is more economical than using a vacuum pump. My question is how does the water + steam combo produce vacuum? I dont know if it is a stupid question but i cant figure it out. I tried using the search bar but then again I dont know what to look for. Any explanation would help or any related article would do.

[Dacs]

Steam in contact with water practically cools it down and what happens when you cool down steam? It'll condense back to water (if cooled enough).

 

And as you already know, water density is way higher than steam density.

 

So just imagine what will happen if you have a steam inside an enclosed vessel that has suddenly changed into liquid water.

 

 

PS: Nice avatar, I missed playing SC

Edited by Dacs, 02 May 2013 - 10:54 PM.

[Spliknot13]

Thanks Dacs, I kind of get the idea.   although I have some difficulty imagining how it occurs in a continous operation.

 

Im really suprised that people recognize one of the faces of SC in this site. Never thought that such technical people here would happen to also love SC.

[Dacs]

I have to admit that I haven't seen that kind of configuration in a continuous setting before since what I said above can be best visualized in a batch setting.

 

Off topic: I played SC for years when I was in college. Good times

[thorium90]

Hi Kerrigan,

 

Im not sure how the vacuum in your plant is produced, but I can share one of the most common ways of creating a vacuum. The use of the venturi effect to reduce the pressure. Multiple ejectors in series can produce pretty high vacuums.

https://en.wikipedia.org/wiki/Injector

Edited by thorium90, 03 May 2013 - 12:22 AM.

[chemag2012]

When you run a distillation with vacuum you will find this: vapors that created from the evaporator will be going up through structured packing or something similar to that technology in order to condense one component from a mixture. Some vapors will still escape from the column. Then, they are condensed with water in barometric condenser. On the other hand, non-condensable gases are withdrew with a flow of steam in an steam ejector.

[Art Montemayor]

 

 The question was: “ how does the water + steam combo produce vacuum?”.  It is not about how a steam jet ejector produces vacuum.  The correct answer is:

 

When you condense all the steam in a system that is filled with steam, you will produce a vacuum.  This is explained by common sense, since the volume occupied by the steam is much greater than the volume occupied by the resulting water (a.k.a., condensed steam).

 

This is easily done in a batch system by filling the system with steam vapor and subsequently condensing it by spraying in cold water.  However, the trick is limited to systems that do not contain non-condensable gases.  This is the old high school physics lab experiment where a can is filled with steam, sealed and then immersed in water.  The can collapses because of the vacuum produced internally.